METEOROLOGICAL MONOGRAPHS

BOARD OF EDITORS

Editor

E. WENDELL HEWSON University of Michigan

Assistant Editor

A. NELSON DINGLE University of Michigan

Associate Editors

J. J. GEORGE Eastern Air Lines

A. H. GLENN A. H. Glenn and Associates

Ross GuNN U. S. Weather Bureau

W. C. JACOBS Air Weather Service

J. KAPLAN University of California, Los Angeles

•

H. E. LANDSBERG U. S. Weather Bureau

R. B. MONTGOMERY Johns Hopkins University

H. A. p ANOFSKY Pennsylvania State University

c. M. PENNER Meteorological Service of Canada

H. RIEHL University of Chicago

METEOROLOGICAL MONOGRAPHS, a serial publication of the American Meteorological Society, serves as a me­dium for original papers, survey articles, and other material in meteorology and closely related fields; it is intended for material which is better suited in length or nature for publication in monograph form than for publication in the journal of Meteorology, in the Bulletin of the American Meteorological Society or in Weatherwise. A METEOROLOGICAL MONOGRAPH may consist of a single paper or of a group of papers concerned with a single general topic .

• INFORMATION FOR CONTRIBUTORS

Manuscripts for the METEOROLOGICAL MONO­GRAPHS should be sent directly to the Editor: E. Wen­dell Hewson, Department of Civil Engineering, Univer­sity of Michigan, Ann Arbor, Michigan. Manuscripts may be submitted by persons of any nationality who are members or nonmembers of the Society, but only manu­scripts in the English language can be accepted. Every manuscript submitted is reviewed and in no case does the editor advise the author as to acceptability until at least one review has been obtained. Authors will receive galley proof but not page proof.

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1. Title page. This will be prepared by the editor if the manuscript is accepted for publication.

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8. Table of contents. Chapter, section, and subsec­tion headings should all be listed in the table of con­tents.

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6. Text. For one of a group of papers which together constitute a MONOGRAPH, it is sufficient to divide the text into sections, each with a separate heading, num­bered consecutively. The section heading should be placed on a separate line, flush with the margin, and should not be underlined. Subsection headings, if needed, should be located at the beginning of certain paragraphs and underlined.

7. References. References should be arranged alpha­betically and designated by numbers. The numbers are enclosed by brackets in the text but not in the alpha­betical listing. When two or more references are in­volved, separate the numbers by semicolons: thus, "pre­vious investigations [3; 12; 27] have shown ... "

Each reference listed should be complete and in the following form. For an article: author(s), year, title of article, title of serial publication (underlined), volume

Continued on Cover 3

METEOROLOGICAL MONOGRAPHS

Volume 2 May 1957 Number 9

INDUSTRIAL OPERATIONS

UNDER EXTREMES OF WEATHER

by

J. A. Russell; W. W. Hay;

J. W. Waters; H. E. Hudson, Jr.;

J. Abu-Lughod, W. J. Roberts, and J. B. Stall;

A. W. Booth; and E. F. Taylor.

Edited by J. A. Russell

with a

FOREWORD

by

Helmut E. Landsberg

PUBLISHED BY THE AMERICAN METEOROLOGICAL SOCIETY

3 J 0 Y ST., B 0 S T 0 N 8, MASS.

ISBN 978-1-940033-13-6 (eBook)DOI 10.1007/978-1-940033-13-6

FOREWORD

Operational applications of climatology have been primarily an outgrowth of military activities during World War II. Shortly after that war there was a flurry of statements and publications which cited the accomplishments of climatology for martial purposes. Some of the papers listed what might be done for peaceful pursuits. In fact, this monograph series (Vol. I, No. 1) was inaugurated by the now classical study of W. C. Jacobs, Wartime Developments in Applied Climatology. Regrettably there was more talk than action. Industrial meteorology and clima­tology got off to a slow start. But the potentials have not diminished. Climate is still one of the most important environmental factors.

In climatology applied to agriculture there have been centuries of experience to draw on. Although there, too, vast domains still wait to be explored, at least a fairly substantial body of knowledge exists. Nature has a way of bringing the relations of climate to crops forcefully to our attention. In contrast, in the commercial and industrial field other problems have overshadowed the climatic factor. It exists nonetheless. It is a factor with increasing growth on the balance sheets. Operations in marginal areas, migration to more favorable locales, distribution of new items, together with greater emphasis on good planning, force a refined analysis of weather prob­lems upon the industrialist and his meteorological consultants.

Among the new aspects is the industrial expansion into heretofore sparsely settled or underdeveloped regions. In many of these climate is a crucial factor. In addition, air conditioning, the use of atomic and solar energy, and the unending needs for more water have, just in the last decade, posed many new ques­tions to the meteorologist. An understanding of the industrial problems is a necessity before the meteor-

lll

ologist, private or public, can render real service. In­telligent advice, with the expectation of satisfying a client, can only be given in the light of a full analysis of his case. The procedures of operations research are very much in order for this purpose. On an industry-wide basis the studies presented in this monograph are an attempt in this direction.

As yet there is flo standard treatment of such problems. These essays present an approach toward analysis of weather effects on selected industries. Cold weather operations are much in evidence in these, partially because weather difficulties become most obvious under these extreme conditions. Even if one does not agree with every detail, it is gratifying to see this start in a new direction. There are very few papers in the meteorological literature relating, in a quantitative fashion, weather and climate to industrial and commercial operations. The profes­sional meteorologists have written reams on improve­ments in their "product", the forecast or risk, but very few case histories on the ultimate application of these products are on record. They have furnished data and predictions but rarely, except in the cases of aviation and the general public, have they been concerned how well these fit the requirements. They have dispensed a universal "pill" with little regard to the ill to be cured.

One can readily foresee extensions of the present work to other industries and trades, to other regions and climates. In this era of export of "know how," detailed information on effects of atmospheric en­vironment on processes and product is needed. This monograph should set the stage for further studies.

H. E. LANDSBERG

Director, Office of Climatology, United States Weather Bureau,

Washington, D. C.

ACKNOWLEDGMENTS

The research upon which the papers in this mono­graph are based was made possible by a contract between the United States Air Force Cambridge Research Center and the University of Illinois. Literally scores of people contributed to the work, but, unless otherwise noted, the authors of the papers that follow were chiefly responsible for the research and preparation of the reports submitted to the Air Force Cambridge Research Center corresponding to those appearing in this volume. Among those whose names do not appear elsewhere, special mention must be made of Professor John L. Page, University of Illinois, who served as adviser on meteorological aspects of the work throughout most of the project, and who contributed in many other ways to the work; and of Professor Kenneth Trigger, University of Illinois, who gave freely of his time in assisting with technical engineering problems. Special thanks are due to Mr. Samuel Solot, Air Force Cambridge Research Center, for his understanding and sympa­thetic encouragement as Scientific Supervisor of the project and to Dr. Leo Alpert for his initiation of the work. A. S. Behrman, Chicago; L. C. Herkert, Pittsburg, Kansas; and Oliver Burke, Detroit were

professional consultants on matters pertammg to water supply, synthetic ammonia, and synthetic rubber manufacture, respectively. James A. Bier, Thomas W. Scott, Stanley B. Shuman, Anthony Sokol, and Frederick T. Witzig were research and cartographic assistants. Gladys Hollingshead and Mrs. Nan Salerno contributed materially to the research as project secretaries.

There is a large literature available on certain aspects of the problems treated in this monograph; some of the papers, therefore, have lengthy biblio­graphic references. Other aspects had meager supplies of published source data, and it was necessary to draw upon the experience of engineers and production men in a variety of industries and concerns. Where this was done, a list of the companies consulted is provided. However, in most instances no specific reference is made in the text to information con­tributed by individual concerns. This is not intended to depreciate the gratitude of the authors to the many people who permitted their working day to be interrupted by answering questions or questionnaires, nor to the administrators of the organizations who authorized the interruptions.

General information on the application of meteorology to industry, business and agriculture may be obtained from:

AMERICAN METEOROLOGICAL SOCIETY

3 Jov STREET, BosTON 8, MASSACHUSETTS

IV

TABLE OF CONTENTS PAGES

FOREWORD ........••.................................. H. E. LANDSBERG 111

ACKNOWLEDGMENTS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv

TABLE oF CoNTENTS................................................... v

I. The Problem, Method, and Conclusions ..................... ]. A. RussELL 1-9

II. Effects of Weather on Railroad Operation, Maintenance, and Construction . ............................ W. W. HAY 1Q-36

III. Weather Limitations to the Construction of Industrial Establishments ............................. ]. W. WATERS 37-52

IV. Weather Limitations to Electric Power Utility Operations ................•..................... ]. W. WATERS 53-65

V. Problems of Industrial Water in Areas of Extreme Weather Conditions ............. ]. ABu-LuGHOD, W. ]. ROBERTS,

AND J. B. STALL. Edited by H. E. HuDSON, Jr. 66-86

VI. Weather Limitations to Primary Iron and Steel Plant Operations .................................. ]. W. WATERS 87-95

VII. The Petroleum Industry .............. . A. W. BOOTH AND E. F. TAYLOR 96-103

VIII. Petroleum Refining and Selected Chem-ical Industries ......................................... . A. W. BoOTH 104-111

IX. The Transportation Equipment Industries .................. ]. A. RussELL 112-121

v

INDUSTRIAL OPERATIONS UNDER EXTREMES OF WEATHER

by

J, A. Russell; W. W. Hay; J, W. Waters; H. E. Hudson, Jr.;}. Abu-Lughod, W, J, Roberts, and J, B. Stall;

A. W. Booth; and E. F. Taylor. Edited by J, A. Russell.

I. THE PROBLEM, METHOD, AND CONCLUSIONS

By J, A. RUSSELL

University of Illinois

(Original manuscript received 27 March 1956; revised manuscript received 7 June 1956)

ABSTRACT

This paper sets up five assumptions under which research was undertaken on the impact of extremes of weather elements on industrial location, processes, and output. Qualitative categories are established for describing this impact, yet in some industries and for some of the weather elements it is not possible to categorize the findings, and in these qualified descriptions must suffice. It is pointed out that damage to plant structures may expose interiors to outside atmospheric conditions, and that an understanding of the effects of weather on processes that are normally housed may avoid costly delay and repair. Conclusions are that although it is theoretically possible to conduct manufacturing operations in virtually any extreme weather element or combination of extremes, the costs would become so excessive under certain conditions as to be prohibitive. At the very least there are serious delays caused by weather elements in accumulating plant supplies and services and in distributing products. The following are listed and briefly described in their order of over-all importance as impediments to industrial operations: low temperature (including permafrost), snow, sleet and ice, high wind, heavy rainfall, high humidity, poor visibility.

It is theoretically possible to construct and main­tain a manufacturing plant to operate in virtually any extreme weather element or combination of extreme weather elements that are known to exist in the world. However, the costs of construction, supply, maintenance, and distribution would be so excessive per unit of product that no existing enterprise could sustain itself in areas where the adaptations in materials, processes, or techniques require a greater expenditure of time and material than the value of the product. At the very least, extreme weather conditions cause serious production and delivery delays.

In the case of plants already satisfactorily adapted to weather extremes existing at their locations, fire, explosion, or other catastrophy suddenly may expose the plant interior to the full effects of adverse weather elements; in such an event prior knowledge of the results of such exposure may help prevent complete disruption of operations. Population shifts, exploita­tion of new resources, the opening of new resource areas, strategic considerations, and other factors have

1

already led to the development of new kinds of locations for industry; sometimes these are in climatic areas where manufacturing, transportation, and plant servicing had previously not been accomplished. Trial and error modifications to compensate weather extremes may be so costly as to be disastrous. Con­tinuing decentralization will result in new problems.

Weather is then an important consideration in production planning for existing manufacturing and for all design and planning for the establishment of new plants. The objective of each of the series of papers that make up this monograph is to determine the extent to which weather elements, particularly extremes of the elements, and combinations of weather elements influence the operation of selected industries or groups of industries. These industries are: railroad operation and maintenance, construction of industrial establishments, electric power generation and transmission, water supply, primary iron and steel manufacture, petroleum exploration and re­covery, selected chemical manufacturing (petroleum refining, synthetic ammonia, coke chemicals, synthetic

2 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

rubber), and transportation equipment production (automobiles, airframes, and railroad locomotives and cars). It is the purpose of this introduction to describe the general frame of reference within which the papers were prepared and to draw summary conclusions on the impact of weather on industrial location and operation.

1. Method and assumptions

The data pertaining to both industrial operations and to weather are almost entirely variables. In­dustries are able to vary their protective housing or servicing, their techniques, their stockpiling and warehousing, or their requirements for personnel to compensate for most of the weather conditions pre­dicted at their locations. The weather elements­temperature, precipitation, humidity, wind, visibility, sunlight-occur singly in all degrees of intensity and, in combinations, in almost unlimited numbers of variable conditions.

In order to obtain at least a degree of comparability of results from the studies of the individual industries and to reduce the problems to workable, yet meaning­ful proportions, it was necessary first to make several controlling assumptions, next to develop a theoretical categorization of the impact of weather elements on industrial processes, and finally to establish practical categories of the impact of weather conditions on the selected industrial operations, housing, and output. i. Assumptions. Five assumptions were established to guide the research :

(1) That the extremes of weather that have the most serious limiting effects on modern industrial operations occur in microthermal humid continental, dry con­tinental, and high latitude climates. These climates, according to the Koppen system of identification, are the Df(w)a, Df(w)b, Df(w)c, Df(w)d (microthermal humid continental); BSk, BSh, Bwk, Bwh (dry con­tinental); and ET and EF (high latitude). Although climates of other types periodically have weather extremes (particularly of precipitation) that exceed the extremes occurring in the above climatic regions, it was assumed that the extremes experienced in other climates of the world were either of little con­sequence to industrial operations or that they would be closely approached in the more severe climatic zones under consideration.

Emphasis was placed on Northern Hemisphere conditions, particularly those which occur over much of the dry interior and northeastern United States and virtually all of Canada and Alaska (fig. 1), throughout all of eastern and northern Europe, and in Asia to the north and east of the Caucasus including

Accordin; lo KlJppen'1 Cloulfleation

LEGENO TO CLIMATIC TYPES A. Tropical Clinw:ltu ,_ SGvm'IKI Cimale Cool Dfo Hot Sutnmers e. Oty BW Otserl aimate Snow- Dfb -.,"" Su'nf'Mf't:

Olmcnes 8S Steppe Otlmott D. Forest Ofc: Cool SunwMni Cso ttoi,Ory Sutr'lll'lltt$ Clmatu

Warm Clb WCII'fi\Ory Summen. E. Pclor ET Tundra CUmore C. Ttmperale Cfo HOI ~s* Ctimoles

Roil'ly Cfb Worm SwnmetS* *t - 1•4Ju.ru thl Ab~e•ce ol • Ot)' S.etM~~ OimcrtH Cft Coot ~ * • - Ot'MtU. a 0' $tUM ill Wllllllf'

FIG. 1. The climates of North America. Definitions of the letter symbols are:

B-Dry climates BS -Steppe or semi-arid climate BW-Desert or arid climate

D-Microthermal, snow-forest climates; coldest month below 32F (OC), warmest month above SOF (10C)

E-Polar climates: warmest month below 50F (10<;:) ET-Tundra climate: warmest month below 50F (10C) but above 32F (OC) EF -Perpetual frost: all months below 32F (OC)

a-Warmest month above 71.6F (22C) b-Warmest month below 71.6F (22C) c-Less than four months over 50F (10C) d-Same as "c" but coldest month below -36.4F ( -38C) £-Constantly moist; rainfall all through the year h-Hot and dry; all months above 32F (OC) k-Cold and dry; at least one month below 32F (OC) w-Dry season in winter

the great deserts of the Near and Middle East but excluding southeast Asia from India to the Hwang Ho (Yellow River) of China. (2) That industrial processes and levels of techniques used as bases for the study should be those current in the United States, Alaska, and Canada in 1953. Conditions elsewhere were noted wherever reliable data were available, but such instances were few. (3) That there are three major steps in the manu­facture of commodities:

a. The accumulation of the necessary materials and services at the place of manufacture. The

1957 J. A. RUSSELL 3

~ather sensitivity of this step includes consider­[on of not only the deterioration, spoilage, eakage, etc. of materials that result from weather nditions, but also the transportation problems tendant upon their accumulation; therefore con­tsions reached concerning the weather limitations . posed on railroad transportation and electric ,wer generation and transmission are generally plicable to the other industries, so weather nditions over a relatively wide area are pertinent. b. The processing of materials into products at e place of manufacture. Weather conditions at ly the place of manufacture are significant to this ~p, except for certain aspects of water supply. c. The distribution of products from the place of :mufacture to the places of consumption. Much e same weather considerations pertain to this step to the accumulation of materials and services.

fhat factors other than weather are commonly :reater importance in industrial location and 1tion than weather. Many of these other factors,

as accessibility to fuels, power, water, other ~rials, and markets, are industrial cost problems can be solved through the availibility of adequate ;portation. Still others, particularly the presence bor, depend not only upon adequate transporta­to bring food, clothing, fuel, and other human ;sities to the plant site, but also on psychological itions of willingness to live near the plant site. pproaching this study it was further assumed labor would be available at any point that other .derations made plant location feasible, and that .abor was a problem largely because additional ;portation would be required to keep workers in ition to work.

fhat modern materials, industrial techniques, other practices exist that make it possible to truct and operate an industrial plant in an area !Ct to any known weather extremes if there is npelling reason for such a location. Nevertheless, ased costs, lower production, or costly modifica-

from normal processes will result from such ions; or if the protective housing is damaged or for any reason, shutdowns or slowdowns will

t. For these reasons each industry was studied mly under conditions of normal operation of the her-protective housing and services, but, insofar ossible, under conditions of nonfunctioning of her protective housing and services.

heoretical categorization of the impact of weather ~nts on certain industrial operations.* Under cer-

ile theoretical solution to the problem was developed chiefly N. Waters with the advice and guidance of Alfred W. Booth.

tain conditions weather elements can have a detri­mental effect upon an industry's equipment and upon an industry's maintenance and service operations.** These detrimental effects operate as agents which place limitations on the existence of specific pieces of equipment or on the functioning of particular in­dustrial operations. To overcome such limitations • the practices and equipment involved can be altered until the limitations reach a degree that makes the performance of the specific operation absolutely im­possible. In most in~tances, however, clearcut limita­tion stages do not exist; rather, there exist degrees of limitation. To facilitate practical research it is necessary to define categories or classes of limitations within which all possible degrees of limitation can be placed. It seems likely that in actual practice each specific degree of limitation pertains to several operations. Thus the problem is to determine theoreti­cal categories of limitations that approach most closely those categories which exist in reality.

A definitive program for arriving at such categories would involve determining all critical weather limits for every industrial operation at which any changes in practices and equipment become necessary. At a few specific limits a great many changes have to be made simultaneously, for example, changes in practice and equipment involved at 32F. From the results of such an analysis many categories of limitations could probably be recognized and defined empirically for each specific operation; however, the actual deter­mination of such detail for all possible variations in operations and equipment is an unreasonably great task. In lieu of such a program it is suggested that five categories of weather limitations can be recognized as adequate for presenting and describing the effects that varying qualities of weather elements have on the industries considered in this monograph.

Category I. No degree of limitation. Fully normal operation of an industry is not interfered with by weather conditions to a sufficient degree that any changes in practice or equipment are necessary.

Category II. A minor degree of limitation. The fully normal operation of an industry becomes interfered with to a minor degree so that minor changes in practices and equipment become necessary in order to facilitate the continued functioning of the industry. Such minor changes can be made without great technical difficulty or without placing the industry in economic jeopardy. The changes can be instituted without any interference in the normal operation of

** Positive beneficial effects of weather were not determined except as an attempt was made to discover the optimum weather for each industry or process.

4 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

the industry provided that the specific weather con­dition is predictable. Category III. A major degree of limitation. The oper­ation or existence of an industry is interfered with to a major degree, so that major changes in practice and equipment become necessary in order to facilitate the continued functioning of the industry. These major changes can only be made with considerable technical difficulty, and with the possibility of placing the industry in economic jeopardy (in terms of the economy of the United States) provided that the weather condition lasts long enough; however, if the condition does not persist too long, and if its occur­rence is predictable and not too frequent, the major changes make possible the continued functioning of the industry, and remove the threat of economic jeopardy. ·Category IV. Economic degree of limitation. The oper­ation or existence of an industry becomes interfered with to a degree that changes in practice and equip­ment necessary to facilitate any form of operation become too costly to be profitable over the long term (in terms of the economy of the United States). Category V. Physical degree of limitation. The oper­ation or existence of an industry becomes absolutely physically impossible in terms of current engineering practices and techniques. For descriptive purposes this category would include all forms of operation which have never been accomplished, and which, therefore, have not been proven physically possible. iii. Categories used to define the impact of weather conditions on industrial operations, housing, and output. The five theoretical categories of the degree to which weather conditions can affect industrial operations, housing, and output included limits of a physical nature for Categories I and V; but limits of a cost-revenue nature for Categories II, III, and IV. The extremely detailed cost-revenue data are normally not available; therefore, only three categories of impact could be meaningful. As finally established and used in the research, the three categories are expressed: Category X. No significant limitation. Weather con­ditions that do not require recognizable adjustments in process or equipment for fully normal operations.

Category Y. Significant but compensable limitation. Weather conditions that decrease operating efficiency to a degree that special techniques, structures, processes, etc., are required, but with these in exist­ence, the industry can function.

Category Z. Absolute limitation. Weather conditions that decrease operating efficiency to a degree that the industry will close if exposed to the weather, cannot

reopen if shut down, or will not be located in areas frequently subject to those conditions.

In applying the above three categories to individual industries, an attempt was first made to establish the optimum conditions for individual processes and next to ascertain what process adaptations and modifica­tions would be required to compensate for increasing or decreasing degrees of weather elements. The final objective was to learn what degree of each weather element resulted in termination of the process.

It will be noted in the summary conclusions (below) and in the detailed discussion in other papers of this monograph that the categories of limitations were applicable to the subject industries with varying degrees of success. Those industries which normally are largely unprotected from the weather elements, such as railroad transportation, power transmission, petroleum exploration and recovery, and, to a lesser degree, steel manufacture, industrial construction and the like, are subject to reasonably firm categoriza­tion. Industries which are normally housed, and for which engineers can design protection against any known weather condition, defy definitive categoriza­tion. Certain economic activities, unhoused in mild climates, are successfully housed in areas of extreme conditions. An attempt was made in such cases to establish the limits at which housing is required. An attempt also was made to study all housed processes under the assumption that sufficient housing failure had taken place to expose the plant interior to ex­ternal weather conditions.

Nevertheless, it will be noted that categorization was most feasible for the industries that have the greatest overall importance to the continued operation of an industrial economy. The industries considered fall into two functional classes: 1) those producing specific limited-use commodities and 2) those which facilitate and make possible the continuing operation of the first group.* The mechanical industries of class (1) that are included in this monograph are the fabrication and assembly of automobiles, airframes, locomotives, and railway cars; the chemical industries of this type make synthetic ammonia, coke chemicals, synthetic rubber, and petroleum products. Iron and steel manufacture is basic to all other industry, and as such is facilitative as well as limited-purpose. The same is true to a lesser degree with petroleum refining and some of the chemical industries. The truly facilitative industries discussed in the papers that follow are electric power, railroad transportation, industrial construction, and water supply. It was

* There are many other ways of classifying industries; many industries fall within both of the classes stated above. This classification is intended for use only in this monograph.

1957 ]. A. RUSSELL 5

;e that generally proved most subject to categori­on. he limited-purpose industries cannot operate 1out the services or materials supplied by the litative industries. Without these, plants cannot built; goods, machines, personnel, and services not be accumulated for the manufacturing process, can products be distributed; the machines of

mfacture cannot run. Therefore, the impact of .ther on the efficiency of the construction, trans­tation, and power industries is of paramount tificance with lesser importance being attached to )thers.* 'he transportation, electric power (transmission),

construction industries normally are conducted doors so that these are the most susceptible to Lther conditions. This being the case, however, 5e are the ones that most successfully have found terials, techniques, and processes which can permit tinued operation under extreme conditions.

Summary conclusions

'he weather elements which impair industrial rations are, in their order of overall importance:

temperature (including permafrost as a side 1lt of continuous low temperature), snow, sleet [ ice, high wind, heavy rainfall, high humidity, [ poor visibility. These differ in their impact on ividual industries and with the experience of man­ment and personnel in meeting them as is indicated the papers that follow. In most of these papers ,sideration is given not only to the impact of the 1ther elements on the industrial process, but also

means by which individual companies have dified machines, services, techniques, housing, and . er aspects of their operations to compensate for reme weather conditions. Sow temperature. Low temperature is the single st critical weather element in affecting the efficiency operations of the industries considered in this nograph. The efficiency of workmen exposed to 1peratures below 40F (or above 90F) decreases y rapidly (fig. 2). The effects of low temperature

intensified by increasing wind speedst and the

It will be remembered that the availability of adequate labor assumed for these studies. The effects of weather extremes

labor efficiency are noted in the individual papers as appro­.te, but no separate treatment is given to this very important tionship between weather and industry. There is a large ·ature in existence concerning this question. The presence of pie in any area of inhospitable climate will require the impor­on of most human necessities and thus will impose extra dens on the facilitative industries which may be already ~rely taxed to supply industrial essentials. Temperature limits cited in this part of the conclusion are mmed to be still-air temperatures. Increasing wind velocities rply increase the chill suffered by humans who are exposed

Labor Eff eciency 50% +--!----t---<i~-N'>--+---lh!---------1

0%-t-~~~~~~g_+---+---r~~ -100 -60 -20 0 20 60 100 140

Temperature- Degrees Fahrenheit

Conditions Reported in 0 Industrial Construct ion EJ Automotive Industry A Airframe Industry x Locomotive and Cor Building ® Petroleum Exploration and Recovery 181 Coke Chemicals

References ore to Ia bor efficiency estimates mode independently by consultants in the industries named.

Comp_ile~ by Lawrence E. Doyle, University of IllinOIS.

FIG. 2. Labor efficiency at various temperatures.

occurrence of snow; this combination of weather elements (low temperature, wind, snow) creates the most critical conditions.

Although the efficacy of temperature as a deterrent to economic activity varies from one industry to another, there are several limiting temperature values that impose comparable difficulties on several. This is particularly true of the facilitative industries. If these cannot function, or if they are seriously im­paired, the other economic activities dependent on them will suffer comparable slowdowns or shutdowns .

Category X. No significant limitation. Although the optimum temperatures for most economic activities are somewhat higher, all industries studied for this report can conduct (for all practical purposes) fully normal operations at virtually all outside temperatures above 32F.t Therefore, it can be concluded that no significant limitation to industrial location or operation exists in areas where extreme temperatures are be­tween 32F and 110F. Industries that normally have protective housing can operate with some minor difficulty when the plant interior is exposed to

to low temperature. Consultants have indicated that exposure to OF and 20 mph wind is as great a labor-efficiency deterrent as exposure to -SOF in still air.

t High temperatures are not significant deterrents up to about 110F. Cooling tower operation, water supply, electrical controls, etc., are adversely affected by temperatures in the neighborhood of lOOF. Labor efficiency decreases sharply as temperatures exceed 90F if combined with high humidity, and is nil at temperatures above about 130F even in dry air.

6 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

temperatures approximating the freezing point. Pos­sible exceptions are: paint shop operations are impaired below 60F and cease between 40F and 50F (dependent to some extent upon the industry and the degree of finish perfection required); labor efficiency of personnel accustomed to inside work drops to about 65 per cent of normal at temperatures around 40F (fig. 2); from 5 to 25 per cent of the parts required in airframes cannot be satisfactorily pressed at temperatures below 40F; some precision machine operations are made difficult at temperatures below 60F.

Category Y. Significant but compensable limitations. (1) Significant limitations imposed by temperatures between 32 and OF. Significant limitations to in­dustrial activity are encountered when temperatures fall between 32 and OF, but these limitations apply only to the industries which normally are housed but which are, for any reason, exposed to such temper­atures. The greater incidence of heavy snow in this temperature range than at lower temperatures imposes certain difficulties on the transportation, building construction, and electric power transmission in­dustries, but these do not result from temperature alone and are considered below.

Temperatures between 32 and OF create a large number of problems for manufacturing processes that are unprepared for the contingency. Most of these are associated with the freezing of water, but there are others. Unprepared machines will not start or at best will start with difficulty. Machine metals pro­duced for tolerance to heat that is generated during operation may become brittle. Labor efficiency drops to about 50 per cent of normal at 32F and to 25 per cent at about 10F among those not accustomed to cold weather work, and personnel accident rates increase. Some materials, particularly among the plastics, become unworkable at approximately 20F. One informant (airframe industry) indicated that the lower limit for continued assembly production, even with limited space heaters for personnel, would be 20F.

However, industries that are prepared for cold weather operations and are experienced in such con­ditions, such as railroads, industrial construction, electric power, iron and steel, petroleum refining, and certain chemical manufacturing, although suffering some inconvenience during periods when temperatures are between 32 and OF, can make relatively minor modifications in process, plant structure, labor force, or equipment that are sufficient to continue essentially normal operations.

It can be concluded that mechanical and assembly industries (airframe, automotive, tire manufacture,

locomotive and car building) which normally are housed, suffer at best serious efficiency impairment, and in extreme cases complete stoppage, if the plant interior is exposed to temperatures below 32F. The impairment becomes increasingly serious and will result in shutdowns between 20 and lOF.

Industries that are normally unhoused or semi­housed (as by a roof) and that are experienced in operations at below freezing temperatures are subject to negligible reduction in efficiency (although incurring somewhat increased costs) at temperatures between 32 and OF. However, important segments of certain of these industries, particularly petroleum refining, chemical manufacture, iron and steel production, and electric power generation, are normally completely housed, and if the housing is removed or damaged so as to expose these essential parts, the industry is subject to the same temperature limitations as those of the mechanical and assembly industries, namely, 32F for serious impairment and 20 to 10F for shutdown. (2) Significant limitations to industries imposed by temperatures below OF. Limitations to industrial efficiency of all industries become apparent when temperatures drop below approximately OF. Housed industries cannot operate if plant interiors are sub­jected to these conditions, so the discussion that follows is directed to those processes which are normally exposed or partly exposed.

As noted above, impairment to unhoused industries is relatively minor at temperatures near OF, but costs of overcoming the difficulties become increasingly greater below OF. The critical temperatures vary from industry to industry, but there is a general critical temperature at about -40F. Below -40 all activities are severely curtailed, even with greatly increased effort; above -40 the expenditure of sufficient effort will permit continued operations on a practicable scale.

For many industries the rate of efficiency loss increases rapidly at temperatures between approxi­mately 0 and -40F. At OF trains lose about 5 per cent tractive effort and hot boxes increase; between 0 and -20F train tonnages are reduced up to 15 per cent (diesel) and 25 per cent (steam); between -20 and -40F the tonnage decrease is 20 per cent (diesel) and 30 per cent (steam). Ordinary carbon steels become increasingly brittle below OF. Steel mills that are not experienced in low-temperature operations shut down at about - 20F.

Train tonnages are further reduced up to 40 per cent (diesel) and 50 per cent (steam) at -40F and below, rail impact toughness is at its lowest level, and only emergency track maintenance can be undertaken. The industrial construction industry has a critical

MAY 1957 J. A. RUSSELL 7

point at about - 30F below which costs are increased as much as 250 to 500 per cent of normal and buildings are not entirely satisfactory. Worker effi­ciency is only 15 per cent of normal among power transmission linemen at -40F. At -40 to -SOF there is serious curtailment of operations at iron and steel mills, even in those that are experienced in low temperature operations; if a mill is shut down, -SOF is estimated to be the minimum at which operations can be started up. The temperature minimum for drilling for petroleum at depths greater than about 6000 ft is -4SF.

It is concluded that temperatures of 0 to -40F impose increasingly severe handicaps, added costs, and serious delays to economic activities that are conducted in the open, but the situation is not critical until approximately -30F is reached. These industries can function at 30 to SO per cent effi­ciency with temperatures as low as -40F; however, costs range from 100 to 500 per cent above normal.

Category Z. Absolute limitation. Although it is diffi­cult to set an absolute temperature limit to the possibilities of operation of industries that have had experience in low temperature operations because most of them have actually functioned at short-term temperatures below -SOF, -40 to -SOF has been determined as the lowest range at which the subject industries can be effective regardless of the cost or effort expended. Although there is a diesel locomotive that will operate satisfactorily at -70F, although adjustments can be made in electrical transmission equipment that will permit power transmission at -80F, and an oil well has been cemented at -68F, all these suffer the most severe impairment at about -SOF. It is estimated that -SOF is the lowest temperature at which a steel mill can function; petroleum refineries and other petrochemical plants have maintained operations during short periods of about -SOF but at greatly increased cost.

It is concluded that the lowest temperature at which any economic activity can be continued on a useful basis is approximately -SOF.

ii. Diurnal range of temperature. A large diurnal range of temperature was considered to be an important limiting weather element by consultants in only one industry-the airframe industry. Although most close tolerance machinery and assemblies will suffer from differing rates of expansion and contraction charac­teristic of different materials, only in airframe assembly was the matter stressed. In general diurnal variations of less than 40F are not detrimental; diurnal ranges greater than 40F impair the assembly of close tolerance aircraft parts.

iii. Permafrost. A side effect of continuously low temperatures is the development of permanently frozen ground (permafrost). All industries are faced with comparable problems of foundation construction and stability if located in permafrost areas, especially if the industry is one that generates considerable heat in the manufacturing process. This heat will melt the frozen layer adjacent to the foundation and structural instability will result.

However, engineering techniques appear to be available which will partly negate the effects of permafrost on industrial construction and operation, with the possible exception of iron and steel operations, but at greatly increased costs.

iv. Snow. It is difficult to set quantitative limits concerning the effects of snowfall on the efficiency of the operations of most of the industries discussed in this monograph. Nevertheless, snow is one of the more significant climatic elements in causing shutdowns and slowdowns of industrial activity, and it was generally agreed that a snowfall of 12 in. or more would cause a decreased production of about 10 per cent for one or two days. It is important to note, however, that the degree to which snow is effective as a delaying factor depends on the amount of experience the community and industrial personnel and management have with snow problems. A very light fall (under 1 in.) can cause more confusion in an area that is unprepared for it than a 10 to 15 in. fall in an area where such falls are of common occurrence. Heavy snowfall normally is associated with temper­atures close to 32F, and therefore its effeCts on industrial location and efficiency cannot be considered without appreciation that the handicapping effects of temperatures at these levels are accentuated by the simultaneous occurrence of snow. Strong wind, snow (or ice), and low temperatures are perhaps the most detrimental combination of weather elements insofar as industrial efficiency is concerned. The combination of temperatures between 32 and OF, snow or ice, and wind in excess of 20 mph constitutes weather which has serious results on such activities as power transmission, railroad transportation, in­dustrial construction, and other essentially unhoused activities. Blizzards, combining these elements at temperatures of 0 to -2SF, provide the most severe weather impairment to these activities.

Snow falling on unprotected machinery, materials, semi-finished goods, etc., seriously will delay or stop the manufacturing process of most industries that normally are housed. In most industries the primary problems associated with snowfall are the inability of personnel to reach work, difficulties of intra-plant movement, and isolation from power and rail trans-

8 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

portation. All of these may impose temporary shut­downs, the length of the shutdown depending not only on the interval before melt, but also on the degree of preparedness of the area.

Snowfall has the most serious effects on rail trans­portation and electric power transmission, and these are reflected in all industries dependent upon them. Snowfall greater than 10 to 15 in. is one of the most serious weather hazards in railroading, particularly when combined with ice and wind (low temperature is assumed). The worst possible combination of weather for train movements is a sequence of (1) heavy snow, (2) thaw, (3) freeze, (4) heavy snow. Drifts and impacted snow can cause derailments. Signals may be obscured or short-circuited by snow; and if communication lines are brought down by snow, ice, and wind, the difficulties of reaching the fallen sections are increased by poor traffic conditions. Under drift conditions it may be necessary to reduce train tonnages by 50 per cent until the line is entirely cleared. All of the delaying results of snow are ac­centuated in yards and terminals where space for snow removal is at a minimum; the delays consequent of yard and terminal blockage are more serious than on-line blockage.

The same situation as that pertaining to railroad transportation is true of the electric transmission system. Periods of maximum line damage coincide with blizzard conditions and the difficulties of reaching and repairing damaged line during or after blizzard conditions prolong the loss of service. Even a light snow associated with destructive winds (30 to 50 mph) will create emergency conditions. Standby power units normally must be installed in areas of unusually difficult power transmission.

v. Sleet and ice. As in the case of snow, so sleet and ice affect industrial efficiency largely through im­mobilization of personnel, impairment of intra-plant movement and external transportation, and cutoff of power. Two inches of ice on railroad tracks will halt the movement of light equipment, and lack of traction may reduce train tonnages by 40 per cent. However, the most serious impairment to train movement is caused by the loss of communication because of the breakage of ice-burdened wires and by winds associ­ated with ice storms. The same 1s true of electric power transmission.

vi. Wind. Most industrial plants are designed to withstand winds in excess of 100 mph. Yet exposed operations can be affected by winds of as little as 15 mph, although such instances are rare and the effects are minor. The impairment to industrial efficiency by wind is often due to side effects (such as blowing dust,

sand, snow, ice, debris) or because of the intensifica­tion of the effect of another weather element, such as high or low temperature. Yet wind alone (55 mph) can halt production flight-testing of aircraft and thus create storage and test backlogs, can disrupt com­munications and power systems, destroy incomplete industrial construction, and otherwise impair the efficiency of economic activity.

Winds of less than about 40 mph are not in them­selves impediments to industry. Velocities between 40 and 60 mph will cause difficulty to outside installa­tions and personnel if there is debris to be transported. Winds of velocity greater than 60 mph will impair almost any outside activity, and can seriously damage wires and poles.

vii. Rainfall. Rainfall (and snowfall) have their most important long range impact on industrial location and operation through their effect on the availability of water for process and personal use. This is par­ticularly significant in the chemical industries, iron and steel manufacture, electric power generation, and petroleum recovery and refining, but an adequate water supply is one of the essentials for the operation of many other industrial processes.

Manufacturing processes that normally are pro­tected from the weather require shelter from precipi­tation, but unless winds are high or temperatures are low, such protection can be afforded easily on a temporary basis if the protective housing is damaged.

Flooding from overburdened streams or from ex­cessive rainfall on unprepared surfaces effectively will shut down virtually all industries.* Twelve to 18 in. of water over the tracks will halt steam locomotives; only 3 to 4.5 in. of water are required to halt diesel locomotives.

viii. Humidity. High relative humidities impose rela­tively minor impairments to the industrial activities discussed here. The most important short term reaction is in reducing labor efficiency when combined with high temperatures, but longer range effects of increasing corrosion are probably of greater total consequence. Corrosion of steel is excessive at relative humidities greater than 80 per cent.

Some industrial processes are adversely affected by high relative (and absolute) humidities. Blast furnace efficiency decreases with high absolute humidity. An absolute humidity of greater than 8. 7 grains of water vapor per cubic foot of air (80 per cent relative humidity at 80F) will create conditions that result in

* The extremely serious consequences in lower New England of the heavy rains associated with hurricane Diane following within a week of hurricane Connie in August, 1955, are well known.

MAY 1957 J. A. RUSSELL 9

inferior castings. High relative humidities reduce evaporative cooling processes and boiler pressures.

It seems to be generally agreed that the critical humidity figure for the impairment of economic activity is 80 per cent relative humidity.

ix. Visibility and other weather elements. The most important remaining weather elements are those affecting visibility. Fog can immobilize completely a transportation system and thus create delays in delivery of materials and distribution of products. Other poor visibility conditions can have similar slowdown effects, and can prevent production flight­testing of aircraft.

Lightning may damage electric power transmission lines for short periods. Strong sunlight exposure will adversely affect certain materials by causing chemical changes which reduce strength and ductility and increase fragility in extre~e cases up to the complete

disintegration of the materials. This is particularly true of plastic materials.*

The other papers in this monograph contain detailed consideration of the effects of weather elements on a few economic activities. These should be read with the understanding that certain elements, particularly low temperature and permafrost, affect most of these act1v1t1es in much the same ways. Similarly most economic activities are affected by water supply problems occasioned by weather elements. In an effort to avoid repetition, material on the effects of permafrost has been concentrated in Paper III and data on water supply problems are found largely in Paper V.

*A differently organized summary of some of the effects of weather elements on certain of the industries described in detail in this monograph appears in Doyle, L. E., and Lemon, R. D., 1955: Controlling weather effects to meet industry needs. The Tool Engineer, 35, no. 6, 113-120.

INDUSTRIAL OPERATIONS UNDER EXTREMES OF WEATHER

by

J. A. Russell; W. W. Hay; J. W. Waters; H. E. Hudson, Jr.; J. Abu-Lughod, W. J. Roberts, and J. B. Stall;

A. W. Booth; and E. F. Taylor. Edited by J. A. Russell.

II. EFFECTS OF WEATHER ON RAILROAD OPERATION, MAINTENANCE, AND CONSTRUCTION

By W. W. HAY

University of Illinois

(Original manuscript received 27 March 1956; revised manuscript received 9 Nov~mber 1956)

ABSTRACT

The railroad section of this monograph presents a condensed version of a study to determine the effects of weather factors on railroad maintenance and operation. Weather effects can cause work stoppages and delays to train operation varying from a few minutes to complete obstruction of the line and normal activi­ties for periods of a few days to weeks. Low temperatures and snow effects are the most frequent and far reaching. The worst effects of weather occur when several elements such as snow, wind, and low tempera­ture combine in one storm. Except for infrequent major disasters--extensive floods, hurricanes, and torna­does-the adverse effects need be only nominal and the trains can be kept running if adequate preparations with trained personnel, materials, and equipment have been made before difficulties arise. Almost universal use of mechanized work equipment contributes significantly to the efficiency and economy of combating weather effects.

This paper has been prepared to show the ways in which temperature, ice, snowfall, wind, moisture, and visibility affect the railroad industry, especially ad­versely. The study is apparently unique. Some limited phases of the problem have been subject to analysis but no overall presentation has, to the writer's knowledge, ever been made. The construction of railroad buildings and bridges and the problems of steel and timber erection, of concrete work, and of foundations are similar to those of general industrial construction, and for these reference should be made to Paper III of this monograph. Purely railroad construction-grading and trackwork-poses the same problems as track maintenance which is discussed at appropriate times throughout this paper.

Railroad operation does not lend itself to establish­ing absolutes. There are too many variables and unknowns involved. In most instances, therefore, it has been necessary to indicate zones of conditions within which certain effects can reasonably be anticipated.

Aside from the ordinary weather effects which are overcome by routine maintenance and operating

procedures, some few situations can tie up a railroad and delay trains for more than nominal periods.

Destruction of a major bridge structure definitely halts train movements over that line until the bridge can be repaired or renewed. Small structures of one or two spans and up to about 20 ft in height can usually be replaced in 12 to 24 hr, using pile bents if destruction is fairly complete. Larger structures will require up to a week for temporary repairs and very large structures will require from a week to several months.

Bridge destruction occurs from floods and washouts, from hurricane and tornado winds, and from fires in areas of excessive dryness. Severe floods can wash out long stretches of track requiring several days to a month or more to rebuild. The worst situations are likely to occur where the track follows a river valley and is thus exposed to flood action for many miles of its length. Floods of such destructiveness follow a long series of heavy rains or heavy spring rains coinciding with rapidly melting snow on frozen ground.

10

Excessive snowfall and drifting have caused delays ranging from one day to a week on main lines of

MAY 1957 W. W. HAY 11

Unites States railroads and up to a month on minor branch lines and on foreign railroads lacking adequate snow-fighting equipment. Snow alone can usually be removed by sufficient plowing but heavy snowfall combined with high winds and low temperatures pack and freeze the snow into solid masses in narrow cuts. Snow slides in avalanche proportions may carry away both track and roadbed. Yards and terminals become blocked when switches are impacted with ice and snow. Such major snow disasters are of infrequent occurrence, once every 20 to 30 yr.

Loss of signals and communication can halt or seriously impair train operations for as much as ten days. Signal and communication lines can be destroyed by floods, hurricanes, tornadoes, or forest fires. A common cause in some areas is the ice storm occurring at or near the freezing point which coats wires, poles, and nearby trees with sufficient ice load to cause breakage. Wind in any amount adds to the destructive effect of the ice.

Severe dust and sand storms while at their peak can halt all train movements and other activities due to loss of visibility and to drifted sand. Individual storm delays are usually of only a few minutes to a few hours duration but the storms may occur with adverse frequency over a period of several months.

The impact of various weather elements on each of the major categories of the railroad plant and operation will be considered in turn. A final summary relates these several categories in their individual and combined effects on the primary function of a railroad-train operation and the movement of traffic.

1. Roadway and track

Weather conditions may affect roadway and track in any one or a combination of the following ways: 1) by rendering the structure unsafe for use, 2) by obstructing the track, 3) by affecting maintenance costs, and 4) by preventing the carrying out of maintenance procedures.

i. High temperature. High temperatures in railroad operation are arbitrarily taken as those above 100F. It is especially important to note that in any temper­ature effect it is often the range of temperature changes involved rather than any specific temperature which is of importance; for example, in the expansion and contraction of rails.

(1) Track. High temperature may cause excessive rail expansion and sun kinks, which can bring about delays or derailments. Rail expands 0.0000065 ft per ft of length per Fahrenheit degree rise in temperature. In laying rail, sufficient openings must be left between rail ends, approximately 1/8 in. per 25F change in

temperature to permit anticipated expansion. No opening is used when rail is laid at 100F or higher. When insufficient opening is allowed the rail ends may crowd together under considerable pressure, breaking the bolts on "rust-frozen" rail joints and bulging the joints out of line. With light rail or im­properly ballasted track (as when inter-tie spaces are empty during track raising or ballasting operations) "sun kinks" may bend the track out of line and sometimes off the roadbed. Serious train delays have arisen during the correction of sun kinks and derail­ments have occurred when the kink was not detected in time. Careful supervision makes sun kinks a rare occurrence: bolts of strained joints are loosened and work which disturbs the track is performed only in the cool hours of the day or concentrated during cool months of the year. Continuous welded rail is re­strained against expansion by rail anchors, spring clips, heavy tie plates, and ample ballast. Preferably the rail is laid at a time of year when the range of temperature changes is a minimum.

(2) Bridges. Expansion must also be considered in the design of steel bridges, especially those with movable spans. Excessive expansion has prevented closing a movable span bridge for several hours. Although the rails may align properly, the locking devices fail to engage and the interlocked signals holding the trains cannot be cleared. Spraying cold water on the steel work and even removing metal with a torch are emergency expedients. The delays are temporary and are not hazardous.

(3) Other effects of high temperature.

a. Dryness in forested areas leading to forest fires. b. Easy ignition of trestles and other timber struc­

tures. Delays due to burned bridges vary from several hours to several weeks depending on extent of damage and size of bridge. In one instance traffic was restored over 72 burned out trestle panels after 150 hr of continuous restoration effort.

c. Warm temperatures, especially if associated with precipitation, promote growth of vegetation on track and right of way, fouling the ballast section and hastening track deterioration. High grass and vegeta­tion close to the track impede the work of trainmen; it may get caught between locomotive wheels and rails causing slippage.

d. High temperatures are associated with drought conditions which in turn combine with high winds to form the dust storms later described under that heading.

e. High temperature and drought also create diffi­culties with water supply. Lack of water has an adverse effect on the entire operation especially with regard to

12 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

locomotives. This will be discussed more fully in the section on motive power. ii. Low temperature. (1) Roadway. Temperatures below freezing can have serious consequences for roadway and subgrades. The degree of obstruction varies with the duration and repetition of freezing cycles, with drainage con­ditions, and with the character of subgrade materials.

Frost heaving comes from the freezing of moisture in the subgrade and ballast section and the resultant expansion of the ground in proportion to its water content. Heaving disturbs the cross level of the rails and, if allowed to continue, will soon make the track dangerous and eventually unusable. Freezing of only a few days duration normally is not as destructive as a prolonged cold spell of a week or more. Repeated freezing and thawing increase the moisture content and thereby the severity of frost action.

Frost heaving is usually nominal where penetration into the subsoil is only two or three feet, but assumes serious proportions with penetrations of five or six feet. Ice forms from surface water and from moisture in dirty ballast and poorly drained subgrades. Ice lenses occur when moisture rises by capillary action from below to the freezing zone. Coarse sands and gravels are free draining, retain little moisture, and discourage capillarity. Fine-grained sands, silts, clays, swamp muck, peat bogs, and muskeg possess or retain moisture and are likely to promote heaving and should be avoided in construction.

Normal track surfacing cannot be followed when the ballast is frozen. The immediate remedy is shimming by placing prepared wooden pads of various thicknesses, 1/16 to 1 in., under the rail or tie plate. A well maintained railroad in moderate temperatures (above 20F) requires only nominal shimming. With poor maintenance or lower temper­atures, shimming becomes a major problem. In the swampy areas of northern Wisconsin, Minnesota, Michigan, Maine, Canada, and Alaska planks several inches thick may be laid on top of the ties and, in some instances, an additional tie has been used to gain the required height and regularity of surface for distances of half a mile or more. Shimming keeps track open to traffic but "slow orders" across shimmed sections delay trains, and the placing and removing of shims in winter and spring consume many man hours.

In permafrost areas of Alaska and northern Canada, the track is permanently underlain with permafrost and ice lenses and the average depth of summer thaw is only a few feet. During the summer season the ballast and embankment progressively melt the ice underneath and uneven settlement follows.

Heaving occurs when freezing sets in. The evils of frost heaving and permafrost can be partially fore­stalled by proper roadbed construction and drainage. In permafrost areas the vegetation and brush are left in place to form a supporting mat. At least the top two to five feet of subgrade should be of porous free-draining gravel, coarse sand, etc., to remove moisture, prevent capillary rise, and absorb the heav­ing from lower placed materials. The Norwegian railways have had success in placing a bed of peat under the sub-ballast section to absorb the swell and, by virtue of being in a state of saturation, to seal off capillary action [2]. Adequate surface drainage, culverts, and clean, full ballast sections and roadbed shoulders also give some relief from heaving.

Bridge piers, abutments, and pile bents, poles, and even building foundations are lifted out by the com­bined processes of frost penetration and frost adhesion. Initial frosts form a top crust uniting with the piers, etc. As the frost crust gets thicker and the freezing ground below expands, the crust is lifted upward and with it the attached foundation members. Adhesive soils should be separated from contact with foundation members by backfilling with gravel or other non­adhesive porous aggregates.

Where drainage is inadequate, ice formation on the track in narrow cuts and in tunnels is a problem. Ice forms in a few hours in solid masses on wall, floor, and over the track, in amounts sufficient to halt or derail a train. It hangs in huge icicles from tunnel roofs. Headlights, windshields, classification lights, and windows are broken and, in extreme cases, derailments occur. Proper drainage, repairs to tunnel linings, constant inspection, speed restrictions, and extra gangs to chop ice away from these critical locations are the usual solutions.

(2) Track. Although sharing directly in the adverse effects of low temperatures upon subgrades, the track itself experiences only a few difficulties due alone to low temperatures.

Rails continue to expand and contract with changes in temperature at the rate of 0.0000065 ft per ft of length per Fahrenheit degree change in temperature. A rail just 39 ft long at SOF would be approximately 3/16 in. shorter at -SOF. Some roads (e.g., the Santa Fe) do not lay rail at OF or lower. The usual adverse effect of expansion and contraction is rail end batter at open joints, affecting the economic life of the rail. As the rail expands in warm weather, the track may be kinked out of line even when temperatures are not relatively high. Difficulties of replacing broken por­tions of continuous welded rail occur with low as well as high temperatures.

Rail steels become significantly brittle somewhere

MAY 1957 W. W. HAY 13

within the 10 to - 25F range and the impact toughness decreases to a low value at -40F. Rails have broken merely by being dropped on frozen ground during unloading at subzero temperatures although probably few rails break from cold alone; localized stresses due to frozen ballast and roadbed sections are also active causes. However, rails already cracked or weakened or when struck a heavy blow as by a fla~ wheel, break with greater frequency in zero and subzero weather. The increase is about 50 to 100 per cent over summer breakage depending on severity of the winter. Joint bars, bolts, turnouts, and crossing materials are also liable to increased breakage. These occurrences are random and produce only minor delays unless the break causes a derailment before being discovered. A derailment may be a major disaster but even then the obstruction to traffic is only temporary.

Switches and movable point crossings may become frozen and inoperative at 32F or lower when moisture from rain, sleet, snow melt, etc., is present. Delay time in unsticking a frozen switch varies from 10 to 20 min, but if many are allowed to freeze at one time an entire interlocking plant, yard, or terminal could become inoperative. Once temperatures have stabilized below freezing, trouble seldom arises from this cause alone.

(3) Minor effects of low temperature.

a. Difficulties and delays occur in cold weather in starting work equipment.

b. Radiators, compressor tanks, lines, etc., must be kept free of moisture and protected with antifreeze below 32F.

c. Hand tools break easily as the steel becomes brittle.

d. Calcium chloride must be added to water in fire protection barrels on timber trestles. (2! lb per barrel is considered safe to -lOF.)

e. Emulsified asphalts used in repairing crossings, driveways, platforms, etc., must not be exposed to freezing weather or spread at temperatures below 50F.

f. Outside painting should not be attempted below 40F.

g. Concrete must be artificially warmed if poured at temperatures below 32F to prevent crumbling upon thawing. Warming is usually considered un­feasible below 20F.

iii. Snowfall. Snowfall has adverse effects on roadway and track both in terminals and on open track.

(1) Terminals. Switches, movable point frogs, cross­ings, derails, expansion joints, and car retarders are susceptible to snow becoming impacted in and around the moving parts. An inch of snowfall, either hard and dry or wet and frozen, may become packed

between the switch point and stock rail, forcing the point to stand open enough to catch a sharp flange of a wheel or to prevent clearing of the switch machine and interlocking controls and signals.

Critical points are large groupings of switches and movable points as in terminals, yards, and interlocking plants. The worst conditions are those of a damp, saturated snow which freezes or a snowfall drifted by heavy winds. A combination of these followed by another snowfall means disaster. Derailments from impacted snow in point openings and in frog and guardrail flangeways are frequent. Even though the main line is kept open a railroad can be completely tied up if turnouts and crossings in one or more important terminals become blocked. When trains cannot be brought into a yard or terminal area the main lines become congested and a general tie-up is likely to occur.

A severe terminal blockade was caused by the blizzard of December 1945, in the trunk line territory centering principally around Buffalo, New York and in a belt 100 mi wide from Erie, Pennsylvania to Albany, New York [6, 7]. Total snowfall exceeded 120 in. and was accompanied by high winds and con­tinuously low temperatures. In Buffalo, 15 in. of snow fell on the 11th and 12th followed by a second storm on the 27th. A thaw and warm rain saturated the snow. On the 28th a quick freeze accompanied a blizzard with 15 in. of snow and winds of gale intensity. Entire yards were tied up with cars frozen to the rails in 18 in. of ice. Snow drifted to car floor and even car roof depths. Hundreds of switches, frozen and impacted, were inoperative and prevented move­ment within the terminal area. Maintenance forces had to dig out individual tracks with picks and shovels to permit the entry of spreader cars to clear adjacent tracks. Even with the use of snow-melting devices, several hundred workmen were required. Snow and ice on the rails reduced locomotive adhesion as heavy winds blew locomotive sand clear of the rails as it fell from the sander pipes. One railroad in this area reported 35 to 50 derailments per day. On the main line trains were snowed in and rotary plows were used to clear the drifts. (2) Open track. Serious snow blockades may occur on main line tracks from direct fall and accumulation, especially in narrow cuts, from snow slides, from drifting, or from a combination of these. A direct fall of several inches on open lines will have no appreciable effect but when accompanied by heavy winds, as in the Great Plains states, only a few inches of fall can drift into shallow cuts forming hard, compact drifts sufficient to derail a train. Wet snow fallen or drifted may, with drops in temperature, freeze into an equally

14 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

hard and dangerous obstruction. Wind blown sand frozen into the drift gives it a concrete-like hardness.

The worst conditions prevail in mountainous regions where heavy snows combine with winds and low temperature. Rotary plows are necessary to remove the obstruction. Trains may become snowed in and even the plows and relief trains may be stranded. Snow slides and avalanches create obstruc­tions equally impassable and worsen the situation by depositing trees or rock masses on the track or by sweeping the track, and sometimes trains, away entirely. In the Pacific Northwest slides often occur during a period of mild weather following a heavy snow storm, covering the track 5 to 40 ft in depth for distances of 50 to 500 ft.

An example of extreme conditions is found in the blizzards of 1949 which hit the railroads of the Great Plains and Rocky Mountains west and northwest of Omaha, Nebraska [12]. These storms began January 2 and carried into the month of February. Winds with speeds up to 70 mph formed drifts 35 ft in height and solid as concrete. Rotary plows could bore tunnels into the drifts but the overburden of ice and snow had to be dislodged by blasting. Many cleared lines immediately again became blocked.

A line between Billings, Montana and Alliance, Nebraska was put out of service for a week by 35-ft drifts. One transcontinental line held all eastbound trains 4 days before a detour route could be opened. A crack streamliner held its passengers 4 days in the Sierras, the train itself not being removed for several days after that.

(3) Snow fighting. Snow fighting may be divided into three main categories: a, initial preparation; b, keep­ing switches and crossings open, especially in yard and terminal areas and interlocking plants; and c, keeping the main line open.

a. Real snow fighting begins long before the first snowfall. Brooms, shovels, salt, sand, oil, plows, spreader cars, and other equipment are made ready and placed at strategic points. Switch heaters are cleaned and tested. Portable snow fences are set out. Sources of emergency equipment, supplies, and personnel are arranged. The railroad's own forces are given assignments for emergency duty. Preparations on the Milwaukee Lines must be completed by November 1, on the Canadian Pacific by September 15, and on the Alaska Railroad by September 1.

b. Snow and ice must be swept and chipped clear of switch and crossing points, plates, flangeways, and moving parts of switches, guard rails, frogs, crossings, and retarders and at platforms and road crossings. Snow melting or removing devices replace hand labor

in turnouts or crossings. These devices may be in the form of portable kerosene burning pots, permanently installed gas heaters, electric resistors, or jets of compressed air. Portable hand burners, weed burners, and steam jets from locomotives are also used. Adequate drainage is mandatory around switches and crossings where snow melting devices are used.

The Canadian Pacific Railway's Montreal terminal operates under extremely rigorous conditions of 120 in. annual snowfall and -50 to - 60F temperature minima. The terminal depends on steam lines to each switch to melt the snow and clear the ground around each switch and crossover. Air lines are laid for use of pneumatic tools in chipping ice and snow. The terminal is kept open with an average labor force of 112 men (maximum of 233) whereas without switch heaters and mechanical snow removal devices 500 to 1000 men would be required [11]. Using switch heaters and jets from weed burning machines, the Illinois Central's Markham Yard in the Chicago Terminal area has experienced a maximum tie-up of 6 hr with blowing and drifting snow which covered the top of rail from bare ground (9 in.) in 7 min.

Snow and ice must be cleared from the track as quickly as possible before another storm arrives, presenting a real problem in yard and terminal areas.

c. Permanent protection is afforded the main line by building snow sheds of heavy timber or concrete as protection against the perennial occurrence of drifts and snowslides. The structures are most often found in the mountains of the west and northwest. One road has an entire wye track, used to reverse the direction of cars and locomotives, under cover to turn engines and plows. Pilot plows or the stream­lined fronts of many electric and diesel electric locomotives permit trains to run through light snow in compacted drifts up to 6 or 8 ft in depth. However, heavier snow or compacted drifts require push plows. snow spreaders, or rotary plows.

Snow fighting requires full cooperation between the operating and maintenance departments. Weather reports are received at division headquarters. When a storm is imminent an alert is sounded to road­masters and trainmasters who remain close to their headquarters. As soon as snow begins to fall or starts drifting, section foremen and signal maintainers are alerted. Those responsible for the operation of switch heater units go to those points immediately. If the storm continues, trackmen are called to sweep snow from switches, crossings, and busy station platforms.

As the storm progresses it may be necessary to put into effect all the emergency arrangements. On the line, snowplows and (if necessary) rescue trains are given right of way. Where traffic is light, or snow and

MAY 1957 W. W. HAY 15

drifting particularly heavy, a plow may be sent ahead of every train. Frequent train and engine movements are more effective than plowing to keep a track open. All efforts are directed toward keeping the main line of each division open.

Regardless of its severity, cleanup following a storm is of the utmost importance especially around yard and terminal areas. Branch lines are cleared as convenient. In severe instances some have remained closed for several weeks or even until spring.

Quantitative aspects of storm delays are presented in the section on train operation.

iv. Wind. Wind alone is not a serious problem in railroad operation except when it strikes in disaster proportions in the form of tornadoes or hurricanes. Wind which combines with snow, sand, rain, or ice intensifies the adverse effects of these in the form of snow and sand drifts, decreased visibility, floods and washouts, and destruction of signal and communica­tion lines. These conditions often attain disaster proportion and delay or tie up traffic for several hours or even several days. A principal effect of wind on roadway and track is drifting snow which obstructs switches and crossings and blocks the main track. These effects are dealt with more fully in the previous section on snow.

(1) Sand and dust. Akin to snow drifting is the drifting of sand on the track. Sand is heavier than snow and is more serious in small quantities. As much as 1 in. over the top of the rail is hazardous to train operation. In cold areas sand mixed with snow or even wet sand alone may freeze into a solid rock­like mass. Sand drifts form rapidly, especially wher:e a cluster of shrubbery or other obstruction forms a nucleus for the drift. Switches, crossings, cattle guards, etc. in the track have the same effect. Drifts have formed to a depth of 12 in. in 5 hr and have completely covered the track and right of way where removal did not begin immediately. Sand gets into the moving parts of switches, signals, cars, locomo­tives, and work equipment. In extreme cases, lubri­cating oils must be drained and bearings disassembled and cleaned.

Sand and dust storms intensify the foregoing problems and add a few more. While drifting sand as a permanent problem is largely confined to the southwestern United States and to sandy beach areas, dust storms are additionally found throughout agricultural areas. Dust storms in 1935 spread over a large portion of the western plains for a 2-mo period. Dust storms are caused by high winds with subnormal precipitation over a 2 or 3 yr period leaving the top soil, already denuded of sod by agricultural activities

and overgrazing, so thoroughly dried out that it blows around freely. Visibility may be severely re­duced and maintenance work halted for periods of 12 to 48 hr. One other serious effect of dust storms is the filling of drainage ditches and openings beyond the capacity or railroad forces to keep them clear. If a heavy rain follows the dust storm, washout and flood damage are likely to occur. Dust choked ballast churns into "puddled" track as rain follows dust.

Emergency measures include vigilant track patrol, imposition of "slow orders," and hand shoveling of sand from switches, crossings, and drifted areas. Heavier drifting may require continuous removal work as in a blizzard with spreader plows, bulldozers, and power shovels, Only heavy rains can properly counteract a dust storm.

Preventive measures include the use of sand (snow) fences and windbreaks, flattening cut slopes (4: 1 to 6: 1) to reduce drifting, raising and skeletonizing track to permit the sand to blow through, and oiling the land surface adjacent to the track. The best permanent protection is to restore grass and forests to denuded areas. On the Saudi Arabia line of the Arabian American Oil Company, shifting desert sands are partially overcome by oiling the right of way, ballasting the track with crushed stone in the dune area, and constantly employing sand sweepers to clear the rails. (2) Severe storms. Gales, hurricanes, and tornadoes, although infrequent in occurrence, cause direct wide­spread damage to large structures as well as small. Tool houses, station buildings, water tanks, coaling stations, trestles, and even larger buildings may be totally wrecked. The heavily constructed deck of a timber trestle on the Alaska Railroad's Whittier Line was once ripped away as a unit.

In the case of a tornado with speeds of 150 mph and higher the danger area moves quickly, cutting a swath a few hundred or more feet in width. The actual damage thus is limited to a small area and seldom delays traffic more than a few hours unless a timber bridge is knocked out or the course of the tornado follows the line of the railroad.

Hurricanes move more slowly. Winds are less severe but may continue for several hours to several days. Large structures may not be destroyed but smaller ones are, the damage extending over an extensive area. Heavy rains and wave action in coastal areas do more damage than the wind alone.

(3) Maintenance. Most routine maintenance is not affected by wind except for the annoyance and dis­comfort to personnel; this may retard slightly but ordinarily does not halt the work. Work performed in unprotected high and dangerous places may be

16 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

halted by winds of 40 mph or greater. Painting must be halted when winds of about 13 mph or greater blow dust on the newly painted surface. Chemical weed spraying in cultivated and settled areas may be halted at wind speeds of 4 to 7 mph to prevent drift of the dangerous spray. Difficulty is experienced in directing the flame of welding and cutting torches with winds of 20 mph or more unless a shield is used. Open flame snow melting pots can be blown out by 25-mph or stronger winds.

v. Moisture. Moisture assumes a variety of forms­rain, sleet, hail, snow, humidity, fog. It is often difficult to isolate each form for individual study. Snow, sleet and ice are given separate sections. Problems arising from lack of adequate water supply are discussed above under high temperature. Humidity is discussed in the first paragraph of this section, but rainfall and floods are of principal interest.

(1) Humidity. Excessive humidity has no appreci­able effect on railroad operation. Paper, cloth, and leather deteriorate from mildew. Steel and iron pro­ducts stored out-of-doors must be given a coating of protective oil, grease, or other compound to reduce rust and corrosion. Experiments have shown that a humidity of 80 per cent or more causes 38 per cent of steel corrosion. Excessive humidity combined with salt air from the ocean causes appreciable corrosion of rail and fastenings. The exact amount of corrosion varies but the Great Northern Railway considers it economical to spend $700 per mile in flame cleaning and applying a corrosive resistant coating to their track where it borders Puget Sound [13]. Corrosion is a contributing factor to "frozen" joints and "sun­kinked" track.

(2) Rainfall. Rainfall promotes vegetation which must be periodically removed to insure clearance, visibility, locomotive adhesion, and a dry ballast section and subgrade. On the western slope of the Cascades, for example, weed growth is excessive due to the moist climate. Growth may continue there throughout the winter.

Almost any soil makes a good roadbed material when it is dry, but excess moisture (usually directly related to rainfall) may cause dangerous and costly instabilities. Cavities or soft spots in the roadbed, usually a result of improper construction methods, collect moisture to form water pockets. Ballast pockets are formed by the working of wet, plastic clays and compressible silts under the pumping action of traffic. Both types grow in size permitting the track to settle or shift, fouling the ballast section and contributing to tie and joint bar wear, rail-end batter, and general track deterioration. Large pockets

may cause the subgrade to slip or slide sometimes under a -train with disastrous consequences. Unstable subgrades are frequently protected with speed re­strictions which increase the running time of trains.

Slips and slides of cut slopes also result from excess moisture, but there are several methods of correcting this situation. Regardless of stabilizing methods used, adequate drainage must be provided to insure stable roadbeds. Surface drainage culverts divert rain, snow melt, and flowing streams away from or under the track and subgrade. So-called deep ditching lowers the water table by placing the ditch invert below the level of the adjacent water table. Sub­drainage collects and carries away underground flow and seepage, and drains ballast and water pockets.

Ditches, culverts and bridge openings are designed on the basis of maximum anticipated volume of flow or runoff from a drainage area. Selection of the proper design-storm is a question of safety and economics. Cost can be the controlling factor for a little used branch freight line; it is cheaper to build for a 5 or 10 yr storm and spend money for restoration if heavier storms hit. When passenger safety and the continuance of a heavy flow of traffic are at stake, however, the design aims at safe, uninterrupted train movement: The 30- or 50-yr storm then becomes a minimum basis for design.

Drainage once installed must be adequately main­tained. Ditches, culverts, and bridges are inspected, cleaned, and repaired at frequent intervals. Changes in vegetation and topography may increase the flow rendering some openings inadequate.

Moisture has little direct effect on the track, but poorly drained track deteriorates more rapidly. Moisture around the ties hastens wood decay. The tie can only be parti<:iJly waterproofed by treatment with creosote compounds. The bearing surface on the tie under rail or plate must be kept dry to prevent accelerated crushing and cutting of the wood fibers. Fiber or rubber pads and cementing compounds are being designed to waterproof this critical area.

Some rusting of rails and fastenings is caused by moisture, especially in steam operated wet tunnels where sulphuric acid corrosion results from the mixing of coal smoke and water. Except in tunnels and salt air, rust and corrosion are negligible on a busy track but are important factors in hastening deterioration of an idle track.

(3) Maintenance. Principal effects of rainfall on maintenance are the effects on personnel-reduced output due to poor visibility and increased work load in maintaining or correcting unstable roadbeds, maintaining drainage structures, and restoring tracks, signals, structures, cars, and locomotives after wash-

MAY 1957 W. W. HAY 17

outs and floods. Most engineering survey work stops in all but the lightest drizzles. Painting of bridges, signals, structures, etc. must stop during even light rains because a surface must be clean and thoroughly dry to accept paint. Weed killing with either chemicals or burners stops until the weeds are dry. Ballast too must be dry for satisfactory cleaning. The hardening and welding of rail ends cannot be properly carried on in the rain because of the quenching action of cool rain on hot metal. Shields are sometimes used but are clumsy and not very satisfactory. Concrete pouring and finishing and earth moving of fine-grained soils must be discontinued when heavy rains occur. (4) Floods and washout. Washouts develop from floods and other causes. An obstructed culvert may impound water behind it with sufficient head to overlap or break through the embankment, or the rush of excessive rainfall or snow melt may be too great for the size of opening. Very little flow across the track is sufficient to start erosion of ballast and subgrade. Piping or erosion along the outside of the culvert barrel sometimes occurs causing the vertical settlement of the subgrade and tracks. Trains may be flagged across such washouts with only a few minutes delay or the track can be out of service 12 to 48 hr while repairs are made. In addition to adequate design there must be continual inspection, semi­annually for the budget program, and also once a week and after every storm by the track foreman to remove debris and make necessary repairs.

Railroads at the foot of high bluffs suffer not only from washouts but from "washons." Heavy rains send quantities of silt, sand, and gravel down the hillside watercourses, filling channels and openings and not infrequently spilling over onto the track causing train delays of 1 to 6 hr. Check or riffle dams and settling basins constructed at intervals down the hillside give some relief by checking flow rates and settling out the sediment. Power shovel ditching must be used at some locations once or twice a year.

The Alaska Railroad is an annual victim of the Knik Glacier which accumulates each year a volume of snow and ice melt behind it. By early July the glacier has melted enough to discharge the accumula­tion down the Knik River with the destructiveness of a more conventional flood, carrying with it ice, glacial silt, boulders, and uprooted trees. The railroad has constructed large bridge openings across otherwise dry areas to accommodate the 3- to 5-day flow. It must man these bridges with men and derricks to prevent tree and ice jams forming and taking out the railroad.

Dry streams occasionally carry large flows from upstream sources. A large northwestern railroad some

20 yr ago lost its crack passenger train and the lives of over 70 passengers when the train ran into a washed-out bridge across a "dry" stream. A cloud­burst had occurred back in the hills many miles from the track so that the railroad had no warning of danger.

Washouts occur from wave erosion even when no excess moisture is present. Four miles of the Milwau­kee's westbound main track were washed out along Lake Pepin in 1942 when a strong wind set up excessive wave action. Severity of wave action depends on strength and direction, fetch (or extent of open, wind-swept area), and depth of water. Derrick stone riprap or concrete sea walls offer the best protection but even these sometimes fail.

a. Flood occurrence. Floods usually follow a more familiar pattern than the foregoing. An extended period of heavy rain is likely to bring streams and rivers to flood stage. The water so acquired varies with each river. Many of the most severe floods have combined heavy rains with melting snows on frozen ground. The rate of snow melting is increased by the rain but there is no soil absorption because of the frost, hence rain and snow melt combine to flood water channels and adjacent land.

Such floods can occur quickly in upstream areas although some warning is possible from a study of snow and frost conditions. Downstream the height and movement of the approaching crest can be plotted with reasonable accuracy.

b. Flood preparation. When a flood is imminent or in its early stages, railroad embankments are sand­bagged, stone riprap is dumped, and timber mats or other protective mass are laid on the slopes and shoulders to prevent scour and wave wash. Bridges are sometimes weighted with rails, loaded cars, or even old locomotives to hold the structures in place. Cranes and men are stationed there to remove trees, stumps, ice jams, and other debris which might jam against the bridge. The closing of rail line openings in dikes and flood walls to provide continuity of the wall may directly halt rail operations throughout the period of high water on the river side of the wall.

More elaborate preparations can be taken when time permits. From its records and river knowledge the Army Corps of Engineers was able to predict, eleven days in advance, the height and time of crest for the April 1951, Mississippi River flood on the 25-mi stretch of the Rock Island Railroad between Nahant and Muscatine, Iowa. Sandbags and riprap were placed on the river side of the embankment and the two main tracks were raised 8 to 10 in. on slag ballast (7 in. above predicted flood stage) for a distance of 9000 ft. The new gradient conformed to that of the

18 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

expected crest slope of the river. Signal batteries and relays were placed on raised covered platforms and a second deck was placed on the existing floor of a bridge. Seepage through the embankment and mud or water boils were pumped out or isolated by a ring of sandbags. The work required 250 carloads of slag, 150 carloads of riprap, 40,000 sandbags, and 175 men. Normal traffic was maintained except for work train delays.* Few flood situations lend themselves to so happy a solution.

c. Flood damage. Flood damage depends upon height of water over track, duration of crest, and velocity of flood. A light lapping of water over the rails will produce a slight ballast wash, but heavy flow across the track will wash out the entire embank­ment and/ or roll the track on edge or completely over in a confused tangle. High flow velocities parallel to the track scour the subgrade from under the track and are most severe where the stream makes an abrupt bend. Scour is also caused when wind sets up wave action in normally quiet pools.

Bridge piers and abutments, especially on ap­proaches, are washed and scoured. Loss of a bridge is the most serious disaster that can hit a railroad. All traffic is absolutely halted until the bridge is repaired or a detour provided.

2. Signals, communications, and electrification

Signals and communications are the heart of modern high speed, high traffic density railroading. Generally weather conditions have little effect but in a few situations the effects are extraordinarily severe. The individual and combined effects of temperature, ice, and wind in ice storms are of such significance as to be treated in a separate part of this section. i. High temperature. The principal effects of high temperature are found in expansion and contraction of communication and signal line wires and of the pipe and wire connections to semaphore signals and to switches in mechanical systems of interlocking. These effects continue downward into the cold tem­perature ranges. Switch and signal connections are equipped with expansion joints or must be adjusted by the signal maintainer as the temperature rises and falls.

ii. Low temperature. Wire expands and contracts much as do rails. Contraction movements set up strains which will cause wires to break at their weakest points-at nicks, worn, or corroded sections. Unless there is some slack in the wire, the strains of contrac­tion will cause breakage even in sound wire over long

*Address by Downing Jenks, President of the Rock Island Lines, at the University of Illinois, 13 February 1952.

temperature ranges, depending on the initial amount of slack and the extent and rapidity of the change. Catenary wires on electrified railroads sometimes experience the same difficulties but to a lesser degree because of the heavier, stronger wire in use. Most railroads decrease or increase the slack or sag in their lines to compensate for temperature changes.

Frosted contact points in trackside signal relays and in switch machines may cause failure of such equipment. Mechanical signals and interlocked switches fail due to freezing of the outside controls (pipes or wires) or by freezing of the moving parts of the signal arms or switches.

Poles are sometimes heaved upward by frost action sufficiently to lose their support. Tripods have been used to carry the wires across swamp and muskeg. Being toed in only a few inches, the tripods are little affected by heaving and adjust to it.

iii. Snow. Snow has little direct effect on signals and communications. Wet snow may freeze on pole lines contributing to the disastrous effects of ice storms. It may render mechanical type signals and switches inoperative by becoming impacted and frozen in moving parts. Snow slides have removed sections of pole lines, signals, and other equipment in their descent. Signals may become obscured or made in­operative by heavy snow. A serious train wreck in 1952 on a major transcontinental railroad was caused by snow covering the signal lens. Switch stands and dwarf signals are drifted over and reflectorized buttons covered so they no longer reflect.

iv. Wind. The principal effects of wind on signals and communications occur in ice storms. Signal and communication lines are often lost during blizzard conditions. Defective wires are likely to snap apart under high winds. Wet snow freezing to the wires creates conditions similar to those of an ice storm. High winds may attain sufficient velocity to break poles and wires. This is more fully described in the section on ice storms.

Wind blown dust and sand have erosive effects on wires and have caused signal failures when sifting into relay boxes and onto contact points of relays. Switch machine mechanisms and controls must be partially disassembled and cleaned following heavy dust storms.

v. Moisture. The principal effects of moisture are found in ice storms. In addition, where electric track circuits are used for automatic signals, water or wet snow between or against the rails may cause sufficient leakage of track circuit current to short-circuit the relay and cause the signals to display a "stop" or "stop-proceed" indication. Delays of an hour or more

MAY 1957 W. W. HAY 19

per train may thus accumulate in passing a succession of such signals before a signal maintainer can get over the line to increase the voltage in each circuit to compensate for leakage. Work on wayside signals and relay boxes must be stopped to prevent moisture entering.

Rain also decreases signal visibility in foggy areas (as in Allegheny Mountain valleys) where amber tinted position-light (or light pattern) signals have been adopted for their ability to penetrate fog. More effective are cab signals which repeat on a panel in the locomotive cab the aspect of each wayside signal and sound a warning whistle when a restrictive indication appears.

Floods and washouts frequently take out pole lines, relay boxes, and signals. Relay boxes are some­times temporarily raised ahead of a flood crest. On some railroads they are raised permanently above anticipated high water levels.

vi. Ice storms. Ice storms are a phenomenon occurring almost anywhere within the continental United States but are generally concentrated in a belt including the Midwestern States between the Canadian border, the central areas of the Gulf States, and eastward to the Atlantic seaboard. Ice storms of great intensity have occurred in Texas and the lower Mississippi valley. Railroads in the eastern half of the United States have experienced more ice storms than those in the western half. Extremely cold areas are normally free of ice storms but ice accumulation from sleet may create similar effects.

The occurrence of major storms has been random in location and not of sufficient regularity to justify much special construction by the railroads although one railroad has installed a short section of microwave radio to avoid hazards of ice storms.

Signals, interlocking, catenaries and third rails, turnouts and movable point crossings, and communi­cations are especially susceptible to ice storms. Turn­outs, movable points, and interlockings experience the same effects noted for icing at low temperatures except that the ice storm often acts more quickly.

All maintenance work is performed with difficulty because tools, materials, and walkways are covered with ice. Motor track cars conveying workmen are not sufficiently heavy to break the ice encrusted on the rails to secure adequate adhesion for movement. Sometimes the car can follow a train which breaks away the ice.

a. Effect on signals. Signals are often put out of service by ice storms. The signal wires are usually located on the low-position cross arms on communica­tion poles. If the communication lines go down, the

signal lines go down too, or become crossed and fouled by the communication wires. Signal wires are often broken by falling trees or linbs falling across the wires.

When signal power service lines are broken, the emergency battery supply automatically cuts in. When signal control wires break, signals generally display their most restrictive indication because the system is designed on the closed circuit principle whereby any unusual condition will manifest itself by the display of a "red" aspect which is on the side of safety.

When only a few signals are affected and repairs can be made in a short time, no major changes in train operation are made. Trains will be delayed because of the restricting aspects of the signals ("Stop-then proceed at 15 mph or with caution, etc."), or because additional restricting train orders and clearance cards must be obtained to pass the restricting indication, but traffic continues to move. When stretches of several miles or more are involved over a period of time, signals will be temporarily taken out of service and manual block rules, with signals displayed by hand, placed in effect.

No serious difficulties arise from ice forming on signal roundels. The optical system and intensity of light in the roundels is sufficient to penetrate even heavy ice layers. (Note: a different situation exists for snow on the roundels.) Semaphore type signals present special problems. Their mechanical movement may freeze in the "green" position and give a false "proceed" indication to trains, a serious type of failure.

These problems are greatly reduced where manual block or timetable book of rules operations normally are in effect. There are few signals, and failures of those that are used do not constitute a serious source of delay. Manual block semaphore signals and train order boards sometimes become iced or frozen and difficult or impossible to operate. No difficulties will be experienced with electrically lighted signals with no moving parts, except through failure of the power supply or the control lines.

Cab signals dependent on power lines for supply become inoperative when those lines are broken. Manual block rules may then be put into effect and trains kept moving at reduced speed, or the trains may proceed on wayside signal indications if those are still in operation.

When centralized traffic control (CTC) systems are hit, traffic is brought to a complete standstill and cannot resume until temporary measures have been taken. A few railroads have installed underground cables for CTC which are free from storm damage but

20 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

experience other and nonclimatic difficulties. When a CTC system is lost, it is necessary to establish train order book of rules operations, usually combined with manual block. Temporary train order block station offices are opened and switches are thrown by hand.

b. Effect on catenaries and third rails. Icing of catenary and overhead contact wire may cause brief delays on little used lines, as it can also in third rail territory.

c. Effect on communications. Communications are more severely affected than any other part of the railroad plant by ice storms. Adverse effects of icing occur in three ways: wires break from the weight of ice, poles break beneath the load of iced wires and crossarms, and lines and poles are broken by falling branches and trees which have in turn broken from the weight of ice. A few broken wires place additional strain on the remainder and release the tension holding the poles in place. These effects are worsened when high winds accompany the icing, a usual condi­tion. A slight breeze is sufficient, however, to set the wires vibrating and cause breakage.

Wire breakage occurs within 3 or 4 hr (occasionally less) after icing begins and extends throughout the area of the storm. Nicked and damaged wires and old, deteriorated poles and crossarms break first, but soon the weight of ice is sufficient to cause failure at any point. Breakage continues as long as ice forms or a high wind blows until all tension in the line has been relieved.

As soon as a storm begins to cause damage, section linemen and signal maintainers go out immediately to make repairs to communication and signal lines. In a storm of disaster proportions, the futility of individual effort is soon apparent. Supervisory forces ride over the line on trains to survey the extent of damage. Motor track cars cannot be used because ice on the rails makes it impossible to obtain traction.

d. Example of effects of ice storms on railroad operations. For illustrative purposes, an ice storm with typical characteristics on the Illinois Central Railroad is described herewith* (fig. 1). The Illinois Central Railroad is a modern well equipped railroad with an extensive north-south traffic between the Gulf Coast (centered at New Orleans) and the Great Lakes at Chicago. Trains are pulled by diesel locomo­tives. Train operation is mainly under automatic block signal rules. The railroad operates an elaborate communication system on its own pole lines including dispatcher's phone and telegraph wires, message lines, railroad business trunk lines, carrier telephone cir­cuits, and teletypewriters. The Illinois Central can

* Extracted from files of the Illinois Central Railroad signal and communication departments.

FIG. 1. Section of Illinois Central lines hit by the ice storm of 30 January-2 February 1951.

be considered an example of a dense traffic railroad with modern and complex systems of train operation, signaling, and communication.

At 1230 GCT 29 January 1951 the leading edge of a cold air mass extended from Chattanooga, Tennessee, through Tusca­loosa, Alabama, across Mississippi and Louisiana to Brownsville, Texas (fig. 1). The temperature at Shreveport was 31F and at Memphis 21F. Professor John L. Page describes the progress of the storm :

"A cyclonic whirl of wind and falling pressures on the east coast of Texas on the morning of January 30 indicated the for­mation of a new center on the front in the northwest Gulf. At this time freezing rain was falling from the Texas coast north­eastward into Virginia. Temperatures in the lower Mississippi Valley had fallen to freezing or below except on the Mississippi coast and the delta south of Lake Pontchartrain.

"During the morning of January 31, the apex of the cyclonic wave moved northward past New Orleans. This gave rise to a change in wind direction to the southeast with a rapid rise in temperature to 74F at New Orleans. This lasted for 5 hr, but for only 3 hr at Moisant Airport, 9 mi to the west. Baton Rouge, 73 mi to the west-northwest, reported 33F, a difference of 41F in the 73 mL As the cold front moved eastward, thunderstorms, accompanied by high winds, caused much damage because ice had already accumulated on objects at or near the surface. Also, as the cold air became thicker the rain changed to sleet and finally to snow."

By the end of the first day, January 30, communication failures began to occur and train delays due to weather conditions became numerous. First reports showed extensive breakage 'of wires and poles over the McComb, Canton, and Yazoo districts on the Illinois Central southern lines. As an emergency measure, five amateur radio stations were utilized to keep Jackson, Mississippi in touch with the rest of the system. The storm increased in intensity during the night and by 1600 GCT 31 January, all through wire service south of Memphis, Tennessee was disrupted.

MAY 1957 W. W. HAY 21

The affected zone included Clarksdale, Grenada, and Corinth on the north, and points south of Vicksburg and Jackson, Mississippi. Extra linemen worked on the Birmingham district and a line gang and outfit cars were moved into the territory that same evening. Extra linemen worked from Grenada south in the Jack­son, Mississippi area. By the end of that day, scattered wire breaks from ice loading and falling trees had occurred all over the Illinois Central southern lines and Jackson, Mississippi was completely cut off from the rest of the system. The storm had then been in progress 31 hr with no indication of a letup.

Several emergency measures were taken immediately (on Janu­ary 31) to alleviate the situation. Additional short wave radio stations were utilized at strategic points to keep the railroad operating. For nearly a week all rail operations between Jackson, Mississippi and New Orleans, as well as in other locations, were carried on by short wave radio. All available signal gangs, extra gangs, extra linemen, and work trains were working overtime during the first two weeks in February making emergency repairs to dispatchers' circuits which had been given top priority.

The storm continued through the night and most of 1 February 1951 as reports of storm damage continued. Although telegraph and telephone gangs, extra linemen, and signal forces worked feverishly throughout the day, ice damage continued to increase more rapidly than emergency repair work. There were still no communications either way out of Jackson, Mississippi although signal gangs were working continuously in this area. As an ex­ample of the extent of ice damage to the Jackson, Mississippi area, the stretch of railroad from Grenada to Jackson (a distance of 111.4 mi) had 614 poles down (75 per cent requiring replace­ment), 3500 wire breaks, 200 trees on wires, and 50 total failures (all lines and poles down). Other southern line territories suffered similar damages spread over a greater area.

Along with communication failures, the ice storm brought other effects which were detrimental to the movement of traffic. The coal chutes and water tanks at many locations were frozen so that trains had to take additional coal and water at points where these items were available. Switches were frozen and packed with snow, causing minor delays in several instances.

By evening of 2 February, the fury of the storm had passed and the railroad continued to concentrate on making temporary repairs to dispatchers' circuits as rapidly as possible. Ice and frozen debris on the tracks had caused several derailments at the coal fields of Paducah. The storm caused a washout on the Tehula District where rising waters piled frozen drift a foot high over the track for distances of 3 or 4 rail lengths. Trains were continually late for over a week after the storm had subsided. The maximum passenger train delay was about 12 to 14 hr at any time during the storm period. Many freight trains were annulled for over a week after the coming of the storm. By the end of 3 February, the storm had subsided to such an extent that it could cause little additional damage although snow still fell that day around Jackson, Mississippi.

Temporary repair work on dispatchers' circuits continued for the next week to ten days as maintenance gangs and work trains were moved about on the various territories where damage was the greatest. By February 15 all dispatchers' circuits were in operation on the southern lines. Trains began to run consistently on schedule after all dispatchers' circuits had been reactivated, but repairs of a permanent nature were being made by southern line signal and communication forces months after the termina­tion of the ice storm. Full permanent restoration of the signal lines was not complete for over two years.

TABLE 1. Ice storm damage: summary of emergency repair work from 1 February to 15 February 1951 on dispatchers'

circuits, Illinois Central Railroad

Item

Work trains Communication gangs

Track gangs (extra) Extra linemen

Section forces including section lineman

Number of days worked

Number of hours worked (average 10 hours per day)

Number of man-hours worked Man-hours per mile (temporary

repairs)

Labor costs (Jackson, Mississippi, area)

Total cost of permanent repairs Cost per mile for temporary repairs

Wire breaks: three sections where all wires were down

Poles down Trees down on wires: many reported

as numerous Broken crossarms (no definite figure)

Train delays: Annulled schedules (maximum

duration) Operated trains (maximum delay) Average train delay (passenger)

Number

3 4 (1 from northern

lines) 2 7 (3 from northern

lines)

365 11 days 4 overtime days

150hours (temporary repairs)

70,050

64

$23,000 $932,500

$850

4,052 plus 3,000

234 plus several thousand

14 days 13 hr 30 min 4 hr 5 min

Due to the emergency nature of much of the work, figures of cost, materials, labor, and train delays are necessarily incomplete. Table 1 compiled from rail­road correspondence files is accurate enough, however, to show the extent of damage and the task of rehabili­tation which the storm imposed.

3. Yards and terminals

A yard is a system of tracks used for the classifica­tion and make-up of trains, the storage of cars, and other purposes. A terminal is an assemblage of yards and servicing, transfer, and other facilities for the originating, terminating, transfer, and interchange of trains and traffic. The roadbed and track facilities and the signal, communication, and electric traction transmission systems are subject to the same weather effects as open track. The sections on low temperature and snow effects have correctly indicated yards and terminals to be more susceptible to the delays of frozen and snow-impacted switches than the main lines. This section is therefore concerned only with those additional effects peculiar to yard and terminal facilities.

22 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

i. High temperature. Terminal facilities generally ex­perience no special difficulties from high temperature. One exception should be noted.

In hump and gravity yards cars roll more readily in hot weather than in cold because of the better lubricating qualities of warm oils and greases. This effect must be considered in designing the height of humps and the grades of hump descents, ladders, and body tracks. With manual hump operation, two humps have sometimes been used, a high hump for winter and a lower hump for summer. Modern retarder yards provide sufficient retarding force to control easy-rolling cars in summer and have non­accelerating grades for easy-rolling cars beyond the last retarder so that the easy-rolling car will not exceed a safe coupling speed of 4 to 5 mph. The required grade varies from 0.15 to 0.20 depending on type of traffic, car loading and weather conditions. This problem is further discussed in connection with low temperature. ii. Low temperature. The proper design of hump and ladders must take account of cold weather require­ments. That is, the height of hump must be sufficient to take a hard-rolling empty car (one with cold lubricant in the journal box bearings) from the top of hump past the clearance point of any body track in the yard. The retarders (or car riders) must then be able to control the loaded, easy-rolling car in summer. There is no winter problem when cars are humped as soon as they come in from the road. However, trains usually are held from 30 min to 2 hr or more before humping, giving the journals ample time to cool and the lubricant to stiffen. Even when given a large velocity head from a high hump, cars with cold journal boxes are hard to handle. At several yards, hot oil is squirted into the bearing boxes as the cars roll over the hump. This not only warms the journal but provides a necessary refilling of lubricant for the road haul.

The engine terminal is susceptible to low temper­atures, especially where steam operation continues and where the turntable is a key unit. The table is set in a pit which forms a natural collector for rain, snow, runoff, and debris. The pit must be kept clean or else the debris will foul drainage openings. If drainage is not provided, the table can become frozen and immovable if a cold wave follows a period of thaw or if moisture enters from other sources (from locomotive wastage perhaps). Some railroads, the Canadian Pacific, for example, place steam heating coils in the pit to assure its continued operation.

At coaling stations, frozen coal is dug and poked out of cars and station pockets by hand at the rate of one or two cars per day. The speed of unloading is

only slightly increased by injecting live steam into the frozen mass. A recent development is a giant shaker which can be set over the top and sides of cars and which, by violent vibration, loosens and dis­charges all the car's contents in 8 to 10 min. Even when coal is placed dry in bins moisture accumulates and freezes. The combined weight of coal and moisture may wreck the bin, especially if it is open to the weather. Bottom discharge gates may also freeze and cause delays while being forced or steamed open. The problem never has been completely solved.

Diesel fuel oil storage should have steam or hot water heating coils for all temperatures below OF, the normal pour point. Special fuels have pour points of -15 and -25F, but even these cause some trouble at -50F.

Water columns and hydrants for steam locomotives are also subject to freezing. The feed lines should be laid well below the frost line and drain valves provided at the same depth so water will not stand in the column or hydrant above that level. Nevertheless improper installations, or failure of the drain valve to function, or even a gradual buildup from quick freezing will lead at times to frozen pipes and thawing delays. One type of hydrant is said to be suitable for filling passenger cars at -40F.

Car-washing machines and racks become ice covered at low temperatures. Use of this equipment is usually halted at 28F or lower.

Other facilities also are affected by low temperature. Not only at engine terminals but also at any point where coal, ore, etc., are transferred, as at a Great Lakes port, for example, the problem of emptying cars of frozen contents arises. The use of steam jets and car shakers are conventional solutions but involve delay and additional expense. Difficulty is experienced in unloading viscous liquids such as asphalt, heavy oils, molasses, etc., from tank cars in cold weather. Critical temperatures vary with the substance. Some tank cars have built-in steam heating coils to warm the contents. For others, small portable coils are introduced through the dome of the car.

Car floats and ferrys are delayed or tied up entirely. Great Lakes ferries manage to keep a path broken through the ice of Lake Michigan most of the year, but are sometimes forced to halt operations. (See Appendix I for details on train ferry operation.) Ice-filled harbors and rivers create hazards and slow the rate of movement even when operations are maintained. iii. Snow. The adverse effects of snow in yards and terminals have already been presented concurrently with its effects on open track. The reader should therefore refer to that portion of this study.

MAY 1957 W. W. HAY 23

iv. Wind. The principal effects of wind in yards and terminals are found in the design and operation of humps. The height of hump should include some additional allowance to compensate for head winds which retard hard rolling cars. The retarders should also have sufficient retarding force to stop an easy rolling car even with a tail wind helping it along. A few yards are now equipped with retarders which automatically vary the retarding effect with the speed of the car.

v. Moisture. Yard tracks pose problems of stability and drainage similar to those already discussed for roadway and track with the added difficulty in properly draining a large, relatively flat area. Cleaning mud from switches and tracks following a flood is an important part of flood cleanup. The discussion of the serious problem of frozen switches need not be repeated here nor that of the effects of fog which are discussed later. Light moisture on the rails serves as a lubricant, reducing adhesion and allowing the cars to run too fast. An electronic device installed in a few large yards indicates car speed and automatically sets up the right retarding pressures and coupling speeds.

In areas of medium and heavy rainfall, freight houses should have canopies or other means of pro­tecting freight being moved to and from cars or trucks. Passenger platforms should be provided with shelters or roofs.

4. Motive power and rolling stock

i. High temperature. High temperatures have a few emergency effects on cars and locomotives. Other adverse effects are overcome by initial design and manufacture.

(1) Locomotives. As regards steam locomotive oper­ation, some increased efficiency is obtained by in­creasing the temperature of combustion and decreasing boiler radiation losses. Lubricants flow a little more freely but those commercially available are able to withstand the relatively small increase above normal operating conditions.

Diesel units offer more of a problem. The crank case oil must be more carefully selected but again suitable commercial grades are available. The motors are more likely to overheat and must be closely watched. If extreme or warm temperatures prevail the year round, a steam heating generator is omitted from passenger locomotive equipment. Cooling fans may be provided for comfort of the engine crew. Locomotives must have radiators and fans designed to provide cooling capacity for the extremes to be encountered. Sufficient ventilation must also be provided under the engine hood to obviate the

removal of side panels when temperature extremes occur. Such removal is undesirable because sand and dust, usual accompaniments of hot, dry climates, will enter the engine-generator compartment.

The failure of water supply is in part attributable to prolonged high temperature. A railroad cannot operate without an adequate supply of water. Even diesels need some water but where steam operation predominates, the drying up of wells, rivers, and reservoirs can bring operations to a halt.

An 1800 hp steam locomotive will evaporate approximately 6150 gal (51,000 !b) of water per hour and a modern 6000 hp steam locomotive approxi­mately 13,000 gal (107,600 !b). Locomotive water tender capacities vary from 6500 gal for small loco­motives to 25,000 gal for the largest. Theoretically steam locomotive water tanks could be spaced about SO mi apart based on an average running speed of 30 mph. As a practical matter stations are closer than this, probably one every 20 mi in the United States but somewhat farther apart in dry regions of the world. Where local supply is inadequate for sufficient wayside watering points, the locomotive may have to carry an extra tender or tank car or water may be hauled to wayside tanks in trains. The quantity of storage capacity required at wayside and terminal water points will vary on each railroad with the size and number of locomotives operated. Capacities of 50,000, 100,000 and 200,000 gal are not unusual.

Diesel locomotives require water in smaller quanti­ties than do steam locomotives for use in radiators and steam generators for car heating. The lesser demand is offset by requirements for chemical purity approaching that of distilled water. Poor water means high maintenance cost and steam generator failures. A modern diesel locomotive cooling system requires 100 to 600 gal of water, sufficient normally to last from terminal to terminal. Car heating generators used with diesel and electric locomotives consume 160 to 350 gal per hr. Locomotive storage capacities are 1000 to 2500 gal. Water is usually stored in 12,000 gal tanks equipped where need be with insulation and steam heating coils to prevent freezing.

(2) Cars. Freight cars experience an increase in hot­box incidence when temperatures rise above 40F, as illustrated graphically in fig. 2.

Failure to observe proper grade design and require­ments for the easy rolling car in warm weather will permit too high a coupling speed and excessive im­pacts. Excessive impact between moving and standing cars causes damage to lading and to the cars, jars bearing brasses out of position (creating potential hotboxes), and sometimes causes derailments.

Fruits, vegetables, meats, and dairy products in

24 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

.. -"' ..,_

16r----,r----.-----.-----.-----.----~

<f)·-

~lzr---~~~~----~-----+-----+----~ >< ~ 0 0 mu I

- c: 0 0

A

I ::: 8 r-~~1---~\---~--------J:------+----~ ~i 0 ~

E ~ 41------jl---'~;;;;;;;c;;;;:::::~::;;;;o-"Lf----~B "'"' I w:::

0

~~0----~0~--~20~---4~0~--~6~0~--~8~0~--~100 Mean Daily Temperature in Degrees F.

FIG. 2 Estimated hotbox setoffs per million car miles, after Wright eta!. [3].

Line A. North-South Railroad line (Great Lakes to Gulf of Mexico, Divisions 1, 2, and 3).

Line B. East-West Railroad line (Great Lakes to Pacific North­west).

transit must be kept at a mmtmum temperature slightly above freezing. Most perishables are thus shipped in refrigerator (reefer) cars, insulated and iced to maintain an inside temperature of 38 to SOF. Cooling comes from cakes of ice in bunkers (9600 to 10,600 !b) at the ends of the cars. Frequently all empty space between the lading and car is packed with crushed or "snow-ice," blown in by air pressure through a hose. Some cars have mechanical fans to improve the circulation of cool air. Cars are now made with mechanical refrigerating units to maintain sub­freezing temperatures for shipping frozen concentrates.

Some produce requires ventilation only. In shipping tomatoes for example, ventilators are opened when outside temperatures go above 40F and closed when outside temperatures are below 40F. For sweet potatoes and pineapples, the critical temperature is 4SF. Ventilators must be open between 32 and 4SF for apples and pears, closed above and below this range. For all other perishables except bananas, the critical temperature for opening and closing ventila­tors is 32F. Bananas must be cooled but not chilled and are kept within the 33 to 4SF range. An important factor here is the amount of ripening desired enroute. In warm weather, ice is placed in the bunkers but in cold weather charcoal or liquid fuel heaters are used instead. Most produce requires one heater when the outside temperature is about 20F and a second when it is -SF.

Domes are provided on top of liquid cargo cars into which liquids can expand on warm days and where gases can collect and pass off safely. Commercial invoices covering liquid shipped in tank cars are usually based on gallonage at 60F. Because there is

considerable evaporation of volatile liquids at high temperatures, railroads in warm climates often place a metal shield or shell around the car to deflect the sun's rays and reduce the rate of evaporation. Load­ing and unloading racks for inflammable liquids must be grounded against static electricity and lightning.

Temperatures for air conditioned passenger cars are held between 70 and 7SF where possible with a maximum difference between inside and outside temperatures of 20F. Two hours and 14 min of delay were charged to setting out cars with defective air conditioning by the Illinois Central Railroad during the period August 19S1 through January 19S2. ii. Low temperature. Low temperatures have several rather severe and numerous minor effects on locomo­tives and cars. Frost or ice on the rails causes loss of adhesion. Ice is easily broken usually by the weight of the locomotive, but when ice storms deposit as much as two inches of ice as happened in England during the blizzards and ice storms of 194 7, locomo­tives may proceed only with difficulty and much use of sand while light rail cars and track cars cannot move at all. No reliable figures are available for loss of adhesion. A coefficient of friction of 0.1S is some­times taken for slippery rails instead of the customary 0.2S for dry rails. This would mean a 40 to SO per cent reduction in tractive effort and therefore in load hauling capacity. In other words a train of 3000 tons would have to be reduced to 1800 tons. It is interesting to note that tonnages were reduced SO per cent during the Buffalo blizzard of 194S [6, 7] when loss of ad­hesion was a serious factor. The effect of snow in reducing adhesion is discussed in the section on snow.

Heat radiation losses reduce locomotive steaming capacity especially if a heavy wind is blowing. In any case a moving locomotive creates its own air currents. The overall loss of tractive effort from a combination of radiation and cold air intake into the firebox with lowered temperatures of combustion is about S per cent at OF; at -70F the reduction is markedly greater. No actual measurements have been made of the tractive effort losses or additional BTU's required at extremely low temperatures. The experience of the Alaska Railroad and other railroads show it is almost impossible to get a full head of steam when the temperature goes below -SOF. Low temperatures are advantageous for diesel-electric engines through better cooling of the motors.

In addition to heat losses, freezing also takes place. Small diameter steam lines will freeze at low temper­atures, as will condensation in the cylinders. Lubri­cants become stiff, and wheels freeze to the rails if the locomotive stands idle for long. Steam locomotives standing outdoors in the yards at Fairbanks, Alaska,

MAY 1957 W. W. HAY 25

at temperatures of -50 to -70F had to be moved at least every two hours to prevent freezing.* Diesels are also likely to freeze--wheels to rails, radiator, steam fittings or heaters, and air lines. The three big prob­lems for diesel engines are frozen radiators, stiff oil in the crankcase, and starting difficulties. The U. S. Army Transportation Corps' new diesel locomotive designed for -70F operation has heaters in the radiator and crankcase. Diesel engines must be housed in heated sheds when not in operation at -40F and colder.

A serious effect both on cars and locomotives is the increase in train resistance due to an increase in journal bearing resistance. The increase in train resistance due to cold journal lubricants over a drop from normal summer temperatures to OF may be as much as 50 to 60 per cent. Again no figures are avail­able as to the effect at lower temperatures. The increase is most pronounced at starting, and helper engines may be necessary to get the train under way and to push it up adverse grades. After the train has been in motion for several miles the bearings become heated and resistance falls to normal. In summer a minimum resistance is usually reached in about 4 or 5 mi but in winter 20 to 25 mi of running may be necessary for temperatures at OF or slightly below and train resistance may never reach the summer minimum at extremely low temperatures. The effect on the train will vary with the actual temperature, with the length of time the train has been standing (whether or not the bearings have cooled) and the proximity to adverse grades.

Low and high temperatures adversely affect car journal lubrication causing overheated journals or hotboxes. Recent studies made at the University of Illinois led to the following conclusions about temperature [3].

"The studies of factors influencing the development of hot­boxes led to the conclusion that the tendency to develop hotboxes is increased by atmospheric temperatures higher or lower than approximately 40F. The development of hotboxes was at a mini­mum when the temperature was 40F. Extreme cold or hot weather up to 70 to 80F was accompanied by increased numbers of hot­boxes. Though cold weather was found to result in increased numbers of hotboxes within a single day, the same relation could not be established for hot weather."

Fig. 2 taken from this same report shows the relation between cars set out from trains and average temper­ature per million car miles.

Other moving and contact points suffer from the cold effect on lubrication. Crank pins, side rod bear-

*"Winter Operating Conditions on the Alaska Railroad," an exhibit by J. P. Johnson, General Manager, Alaska Railroad, May 26, 1951.

ings, cross heads, and cylinders of steam locomotives experience increased resistance as low temperatures reduce lubricating efficiency.

The following tonnage reduction schedule is recom­mended for diesel operation on the Alaska Railroad:*

Temperature range (F)

30 to 0 - 1 to -20 -21 to -40 -41 to -60

Reduction (per cent)

0 15 20 40

Earlier instructions required tonnages 10 per cent lower than this (when steam was in general use). As an actual practice, train crews frequently cut their trains in two and run with only half tonnage, especially over adverse grades.

The Milwaukee Road reduces tonnages as follows:

0 to -10F

-11 to -20F

10 per cent

30 per cent

Below -30F dispatchers use their own judgment. Usually a 5 to 10 per cent reduction is made when strong adverse winds prevail.

Where very steep grades (2.00 per cent or more) are encountered, the increased resistance due to temperature may be so small relative to grade re­sistance that its effect is ignored. The effect of low

Type of Deloy

Thaw Out Steam L1nes on Cars Snow 1n Switches

Frozen Switches

Frost on Contact Points St •ppery Roi Is Heavy and Onfted Snow General Blizzard Conditions Frozen Cool Supply

Frozen Water Supply

Snow Sl•des

Snow Plow Delays

Strong Winds

Poor Visibility (Fog)

Poor Visibility (Snow)

• • •

• ~

0

Amount of Delay ,...,..._._ __

• 15h2om

10h54m

lh 12m

3h oom I h 32m

::3 7h 49m

204h 54m

rh oom

oh 20m

2h 41m

32h 59m

I h 25m

4h 19m

oh1om

10 20 30 40 190 200 210

Hours of Delay

Total Weather Delays 317h 35m

Toto I Delays (oil kinds) 2519h OOm

Per cent Weath-er Delays 12.6%

15 Trains Annulled

FIG. 3. Summary of recorded delays to regular trains caused by weather on the Milwaukee Road main line: Chicago, Illinois, to Tacoma, Washington, January, 1952.

26 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

Type or Delay

Thaw out Cars Clean Snow -Diesel Exhaust Thaw out Steam L•ne

Snow in Switches

Frozen Switches

Frost on Contact Points Red Signa I -Snow Leakage Slippery Rails

Heavy and Drif1ed Snow~===== General Blizzard Conditions Frozen Cool Supply

Frozen Water Supply Coupler Failure II (Impacted Snow) ... ~ ... ,.. .... Snow Plow Delays P' Strong Winds

Poor Vis i b 11i t y (Fog) Poor Visibility(Snow)

-

Amount of Delay

I

I

I

d'o7m oh4om

2h44m

sh3zm

ohzom

d'zzm oh,om

ohz5m

27h45m 75h 29m

None

None zh35m

47h23m

1h55m

oh5zm

oho5m zh5sm High Wo ter I

O~-;J:I0:-:21,0~30:--:4!:JO 120 130 140 150 160 170 180

Hours of Delay

Total Weather Delays 470h II m

Total Delays (O!I kinds) 1537h 30m

Per cent Weather Delays 12.6%

17 Trains Annulled

FIG. 4. Summary of recorded delays to regular trains caused by weather on the Milwaukee Road main line :.Chicago, Illinois, to Tacoma, Washington, March, 1952.

Causes

Repo~rs to Air Conditioning

Frozen Steam L1nes

Frozen Water Connections

Frozen InJectors

Frozen Express Cor Doors

Frozen Couplers

Frozen Switches

Snow in Sw1tches

Frost on Signal Contacts

Strong Winds

Fog

Rain

Snow

HHJh Water

General Weather Conditions

• • •• ~

w.

0 3 4 5 6 7 8

Hours of De loy

Toto! Deloys-40hl2m (August, 1951 through Jonuory,l952)

Amount or Delay

zh 14m

4h31m

zhs lm

oh36m

ohzsm

oho7m

oh44m

ohssm

4h37m

shzsm

3h3om

I h03m

1 hssm

3hoom

sh 15m

9

FIG. 5 Delays to Illinois Central scheduled trains caused by weather and related factors, August, 1951-January, 1952.

temperature in cars in yards has been covered in the paragraph on yard operation. Generally tonnage reductions can be ignored with diesel-electric and electric operation because of the overload capacities of those types of motive power at starting and at slow speeds.

Brakes are susceptible to cold. Ice and snow frozen on the brake rigging can make those inoperative. Frozen condensation in train line, brake valve, or brake cylinder is a possible hazard. The steam line is also subject to freezing delays from these causes as shown in fig. 3, 4, and 5.

A series of miscellaneous effects can be noted for cold. Wet coal freezes in tenders and requires hand work or steaming to dig or to thaw it. Ice around the manholes of the water tanks on tenders and at way­side water stations offers hazards to the engine crew. Frozen water columns may necessitate running to another point for water, sometimes with dangerously low water. Occasionally water column discharge valves have frozen open while in use overflowing the tank and flooding and freezing the adjacent area. Sand may freeze in the sand boxes of diesel and electric locomotives or in the discharge pipes on any type of locomotive. Windshields and cab and car windows become glazed with ice, a hazard on the engine or caboose, an annoyance in passenger cars. Car wheels and axles are more likely to break as the steel becomes brittle somewhere in the 0 to -30F range. Ice storms as such have no special effects not already noted on motive power and rolling stock. iii. Snow. Snow has few direct effects on cars and locomotives. Finely powdered, dry snow blown by heavy winds or carried to the sides of cars or locomo­tives by the swirling action of the moving train causes some difficulties. The snow enters through air filters of diesel locomotives, blocking interior passageways with a foot or more of depth. It also gets in the electrical control apparatus, main generators, and traction motor blowers causing leakage, short circuits and burned out motors. Moisture grounding results. Remedies lie in winterizing the locomotives by block­ing off about half of the car body filters. Exhaust openings from the main generator to the outside are closed to reuse circulated air rather than snow laden fresh air. The foregoing are practices on the Canadian railways [5]. Diesel locomotives having the air intake placed on the roof take advantage of the relatively snow free space above the locomotive. Similar but less severe difficulties are experienced with air condi­tioning filters on passenger equipment. Snow on third rails reduces contact as in ice storms.

Snow in gangways of steam locomotives is excluded by cab inclosure or by canvas curtains. Snow (and ice)

MAY 1957 W. W. HAY 27

on handholds, steps, brake wheels, brake valves, and other external appurtenances of cars and locomotives creates accident hazards, but otherwise is merely annoying. Snow on windshields and windows obstructs vision. Snow on headlights, marker lights, and classification lights reduces their illumination and effectiveness. Agitated snow also becomes impacted and frozen in fireboxes, running gear, trucks, and brake rigging. Minor delays may be required for thawing and clearing away the accumulation. iv. Wind. Wind increases heat losses from steam locomotive boilers and is one of the factors that determines cold weather tonnage reductions. In warm temperatures this effect is of little importance and can be ignored. Strong winds often blow sand away which is being deposited on slippery rails to increase adhesion. A tonnage train ascending a ruling grade could well be stalled and forced to double the hill (take the train up in two sections). Winds reduce visibility from the locomotive cab by blowing smoke and steam over the front end and cab. A few American and many European locomotives are equipped with smoke lifting shields or draft plates on the front of the boiler to counteract this tendency. Sand and dust blown into the bearings and moving parts increases wear and abrasion. This is of minor importance except in the case of sand and dust storms. The resistive effect of wind will be discussed in connection with train operation.

The principal difficulty with diesel and electric locomotives is sand and dust blown into motors, generators, and other moving parts. The air intake for the engines is equipped with an air filter but after running through a severe dust storm it is usually necessary to clean the air filters and strainers. Diesel locomotives used in Saudi Arabia are equipped with a special "snorkel" type air inlet to filter out the sand. The smoke and steam problem and heat losses from boilers are absent from diesel and electric operation.

Although the conventional freight car journal box bearing is simple and rugged, sand blown in during a dust storm can be a contributing cause of hotboxes. Passenger car bearings are more tightly sealed and suffer less. v. Rainfall. Slightly wet rails reduce adhesion and require sand at starting and on long steep grades, but rails washed clean by heavy rains offer almost as good adhesion as when dry. Steam locomotives can run through water up to the firebox or about 12 to 18 in. over the top of the rail. Diesel and electric locomotives are limited to depths not over 3 in. to keep moisture out of the motors. Motors and generators must be kept dry to avoid leakage and possible complete

breakdown of insulation and burned-out motors. In wet or humid weather electric and diesel locomotives will operate at somewhat reduced efficiency due to current leakage through moisture absorbed by the windings. Rainfall has no effect on cars other than adding moisture that would freeze in a sudden temper­ature drop and having a slight cooling effect on incipient overheated bearings.

5. Personnel

The principal effects of weather elements on person­nel are: 1) reduced efficiency, 2) discomfort, 3) in­creased accident hazards. None of these can be considered limiting in railroad operation. Outdoor workers, including maintenance of way, structures, signal and communication workers, and outdoor equipment repair men are primarily affected. Train and engine crews, coal dock men, pumpers and yard men, being out of doors intermittently, are less affected. i. Extreme heat. Heat is enervating and reduces the rate of work. Sun glare causes eyestrain, headaches, and dizziness. Perspiration trickles into eyes, attracts annoying insects, and makes handholds on tool handles and grab irons slippery and insecure. These conditions are all conducive to accidents. Hot tool handles and materials, especially in track work and in car repair yards, reduce the work output and cause discomfort. Rail temperatures of 130F are common. A steel lining bar may literally become too hot to handle, at least without wearing gloves. Wrapping the tool handles with friction tape is of some help.

The combination of heat and humidity must not be overlooked. The normal discomfort that most people experience in summer is due more to humidity than to heat. Discomfort is felt at about 80F and slight distress at 90F on humid days. Little discomfort is felt until about 90F on dry days and distress may not be noticed until 100F. The southwestern areas usually experience a dry heat.

Sunstroke and heat exhaustion are dangers from overexposure or overwork in the sun. The occurrence of these varies with the constitution and experience of the individual and is not a limiting factor for most workers on a railroad who are usually acclimated to local conditions. ii. Extreme cold. At temperatures down to about OF well clothed workmen will perform with little dimi­nution of effort. Below OF and down to -40F there is likely to be much lost time in trying to keep warm. Yardmen will spend time in yard offices and switch shanties and trackmen will build fires and stay as close as the foreman permits. There is real danger

28 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

of frostbite within this range and overexertion may injure the lungs. Below -40F outside work is reduced to a minimum. The Alaska Railroad has found that very little outdoor car repair, track maintenance, construction, or other work can be performed if the temperature drops to -40F, and only in emergencies are men required to work out of doors for lengthy periods. Nevertheless, the Quebec, North Shore, and Labrador Railroad carried on ballasting operations at -56F to meet their completion date [16].

Train and engine crews are exposed directly to the cold only for short periods of time and can therefore continue their work under extreme conditions. An exception is the flagman who has to remain outside for lengthy periods, but, as little activity is required of him, he can dress accordingly.

The foregoing is based on the use of conventional winter clothing suitable for the locality. It is always possible to add additional garments but the resultant loss in freedom of movement offsets the advantage gained and there still remains the problem of vulner­ability of the lungs to frostbite.

Even with conventional clothing, speed of move­ment and nimbleness of hands and fingers is lost. As a rule of thumb, human efficiency may be considered as decreasing at about the same rate as the tonnage rating for locomotives.

Low temperature creates accident hazards. Tem­peratures below 32F cause ice and frost to form on walkways, footboards, platforms, gangways, grab irons, and steps. Slipping accidents result. Ear coverings reduce hearing and sensitivity to warning sounds and approaching trains at a time when snow blanketed ground muffles those sounds anyway. Men riding on motor track cars set up windshields or turn their heads from the cold wind thereby failing to note the approach of a train or other obstruction. Clumsiness from heavy dress when handling tools or heavy materials can result in accidents. In general a man who is bundled in heavy awkward clothing, with head and face partially covered, chilled and with tingling hands, feet and nose is neither safe nor efficient as a workman.

Low temperature imposes added duties. The re­moval of ice from track and switches, repair of broken wires, etc., and the shimming of frost heaved track takes most of the maintenance man's winter work period which could otherwise be devoted to other work. iii. Ice storms. The principal effects of ice storms on labor are the creation of unpleasant and hazardous outdoor working conditions and a demand for greater intensification of effort on the part of signal, electrical, communications, and track labor. These workmen

are called upon to put in long hours of overtime duty, leading at times to exhaustion or accident. There may be difficulties in contacting laborers and getting them to the job because, like the railroad, other modes of transport-highways, bus, and interurban lines, etc.­experience interruptions from the storm. Motor track cars in some instances cannot be used because ice on rails causes loss of adhesion.

iv. Snow. Falls of 6 to 18 in. tie up other modes of transport and hinder workmen going to their work. This effect is the worst in cities where heavy snowfalls are unexpected. Twelve inches of fall in such a locality could make most workers several hours late to work; many would not report at all.

All outdoor work is performed at a disadvantage where snow is present. Slipping and tripping hazards prevail, hand tools and small items of material are easily buried and lost in snow. Some work, rail laying, for example, is avoided in snow seasons if at all possible. Snow melting on clothing is a hazard to health. Falling or wind-blown snow decreases visibility and increases the dangers of being struck by trains or of tripping over unobserved objects. When snow is present men usually cover their ears against the cold, thus adding the hazard of obstructed hearing to obstructed vision. Snow also muffles the sound of approaching trains.

When snowfall is beyond the capacity of normal equipment and personnel, temporary labor is secured from furloughed employees, from among the office and shop personnel, and from labor contractors. These extra forces create serious problems in super­vising, feeding, and billeting. Extra forces are usually untrained, and must be given special supervision to avoid injuries. Usually the regular maintenance employees act as foremen in charge of small groups of extra help. The effects of extreme cold often combine with the difficulties of labor under snow conditions further to reduce labor efficiency and safety.

v. Wind. Some inconvenience and discomfort is caused workmen by wind. In the winter it chills more quickly and drives snow, decreasing visibility. In summer sand and dust are blown into the workmen's eyes and may again reduce visibility. Goggles and (in dust storms) respirators are sometimes worn as a protection against wind-blown dust. These discom­forts reduce work output and create personal injury hazards, especially where vision is obscured.

vi. Rainfall. Outdoor work is decreased a varying amount and accident hazards are increased by rain. Train and yard crews perform their duties regardless of rain. Trackmen, linemen, signal maintainers, car inspectors, and car repair men work in slow steady

MAY 1957 W. W. HAY 29

light rains but usually seek cover during heavy or continuous downpours except in emergencies. Cumber­some clothing and wet, slippery tool handles, ma­terials, walkways, steps, and grab irons are potential accident hazards. Visibility is reduced, especially when rain and fog occur together. Exposure to rain, especially at low temperatures, is a health hazard.

6. Train operation

The effects of extreme weather conditions on railroads can almost always be reduced to one or a combination of the following: 1) train delays, 2) in­creased costs, 3) increased accidents. The only purpose of a railroad is to move freight and passengers by means of train operation; analysis of the several and combined effects of weather elements on train oper­ation will amount to a summary of weather effects on railroads. The effects of weather on cost and accidents are here to be considered only in a briefly summarized form because an adequate extended treatment of either would constitute a study in itself.

i. High temperature. Train and yard operation at high temperature involves few problems not already discussed in preceding paragraphs. General inefficiency of personnel will delay trains an indefinite amount. Trains may lose from 10 min to 6 hr awaiting correc­tion of sun kinked track. Expanded rail joints, switch points, and locking devices on movable span bridges may also cause delays of 10 min to several hours. Hot bearings on rolling stock cause delays of 20 min to 2 hr for cooling or re-brazing the hot journal or setting the car out of the train. An undiscovered hotbox may cause a serious train wreck delaying traffic several hours to several days.

ii. Low temperature. Preceding paragraphs have in­dicated most of the effects of low temperature on operations. Train movements are delayed by frozen

D•v•s•ons

Milwaukee

La Crosse 8 R1ver

Host tngs 8 Dakota

Trans- Mtssouri

Rocky Mountain

Idaho

Coast • •• 0 20 40 60 eo

Hours of Delay

• T Amount of Delay

5h56m

8hosm

202h37m

39h49m

45h53m

5h32m

9h43m

190 210

Total Delays-January, 1952- 317h35m

FIG. 6. Delays to regular trains caused by weather on the Milwaukee Road by divisions, main line: Chicago, Illinois, to Tacoma, Washington, January, 1952.

DiviSions

Mi lwou kee

La Crosse 8 R1ver

Amo.unt of Delay

3h43m

7h29m

• 374h 12m

84h57m Host1ngs 8 Dokoto~========~M Trans- Missouri -

Rocky Moun to 1n

Idaho

Coast

None I I I

None I I I

None

0 20

No De lays

No Delays

No Delays

40 60 80 1001.1...!:3,-±6-:!-0...1...!3:-!80

Hours of Delay

Total Delays- March, 1952- 470h 11m

FIG. 7. Delays to regular trains caused by weather on the Milwaukee Road by divisions, main line: Chicago, Illinois, to Tacoma, Washington, March, 1952.

Divisions

Iowa

Chicago Term•nol

Springfield

Ill ina is

St. Louis

Kentucky

Memphis

Vicksburg

Louis ion a

Hours of Delay

Total Delays- 40h 12m {August,l951 through Jonuary,l952)

Amount of Delay

10

FIG. 8. Delays to Illinois Central scheduled trains caused by weather and related factors, August, 1951-January, 1952.

switches, broken rails, frozen train lines, frozen brakes, and by frozen water and coaling stations. The effects of these in actual time lost are shown in fig. 6, 7, and 8 in which delays on the Milwaukee Railroad operating under severe low temperature conditions and on the Illinois Central Railroad which operates under moderate conditions are shown graphically.

30 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

Low temperature alone will not halt train operation or even cause more than nominal delays if proper routine and conventional maintenance is carried out. A more serious effect is the reduction in tonnage ratings, which, at temperatures below -40F, will approximately double the number of trains required to handle a given volume of traffic and increase the road time. Steam locomotives have taken 36 hr to haul a reduced tonnage train between Nenana and Fairbanks on the Alaska Railroad, a distance of 60 mi, at temperatures between -60 and -70F. Diesel performance has been more dependable.

In yards the problems are those of frozen switches and of increased rolling resistance due to loss of lubricating qualities of journal oils. Proper initial hump design, introduction of hot oil into journal boxes, or extra running are solutions. In one of the large Chicago yards the solution has been to pull the cars back from the receiving yard away from the hump before classifying. This serves to warm the journals but delays operations. Their experience, which is typical of Chicago and similar locations, is that temperatures from 32 to OF slow down the movement of cars but not seriously. From 0 to -15F the standing cars must be pulled back once before humping. This takes about 15 min for trains averaging 52 cars per train. Temperatures lower than -15F (seldom encountered in Chicago) require two pull-backs and an average lost time of 30 min. Another disadvantage, in most yards, of the pull-back is the blocking of the inbound end of the receiving yard during the move­ment. Yard operations may be delayed but are not halted by cold. iii. Ice storms. Ice storms do not halt railroad opera­tion but can cause serious delays. The minor delays of frozen switches, signal mechanisms, ice on catenary wires and third rails, etc., have been previously dis­cussed, as has the effect of ice storms on communica­tions. The present discussion is concerned with the operational consequences of lost signals. When signal lines go down, signals become inoperative and display their most restrictive aspect until they are put out of service or the batteries become exhausted. In auto­matic block territory, trains must stop at each restricting intermediate signal and proceed with caution (15 mph) to the next signal.

To avoid the stopping at every signal, the automatic system rules are therefore suspended and manual block rules put into effect. Normally both manual block and train order signals are retained in their most restrictive position except when cleared for a specific movement. The delays which occur through failure are those of stopping the train to obtain a train order and/or a form "A" clearance permission

to pass a stop signal. For an individual train the delay is from 20 min to 1 hr because of the long walk from the caboose to the train order office or telephone. Delays for passenger trains are less because the con­ductor has a shorter distance to walk. If traffic is heavy, these delays have a cumulative adverse effect on movement of traffic throughout the division. If the train order or interlocking signal is inoperative, the operator at a train order office or interlocking plant may· also handle movements by use of hand signals given with flags or lanterns. The simpler the system of train operation and signaling, the less susceptible is the system to storm damage.

When centralized traffic control systems are dis­abled, traffic is brought to a complete standstill and cannot resume until temporary measures have been taken. It is necessary to establish train order and/ or manual block operation with temporary train order and/ or block stations from which operators control train movements.

While reverting to train orders and/ or manual block operation is a satisfactory solution in itself for temporary train control, the situation is usually made far more serious by loss of communications upon which even these temporary measures must depend. The delays inherent in manual block operation are insignificant compared to the additional delays which result from inability to pass train orders from dis­patcher to block station and train or from one block operator to another.

Loss of communication is of serious consequence to train operation and can halt it for a week or more. Freight trains suffer more serious delays than passen­ger trains and may be annulled entirely until some form of communication is restored. Efforts are usually concentrated on keeping the principal passenger trains moving. Both freight and passenger trains on branch lines are usually annulled entirely until some form of communication is available. Recorded delays to trains are given in earlier paragraphs. The amount of delay is dependent on the amount of initial damage, duration of storm, availability of other means of communication and availability of repair facilities. The more complex the normal operation, the more disruption occurs when disaster strikes. Commercial lines are usually destroyed also by the same storm that wipes out railroad facilities. These lines are then not available for railroad lease and at the same time the commercial companies are competing with the railroad for the purchase of emergency repair mater­ials and equipment.

Scheduled train operation can be restored in 2 to 14 days (upon restoration of dispatchers' circuits). iv. Snow. Snow has the obvious effect of obstructing

MAY 1957 W. W. HAY 31

ORE.

NEB.

~'-·- ----~·-·--I KANS. .,

i. I

i \ ILL.

I AND PACIFIC RAILROAD I

\ \.

ARIZ. DOUBLE TRACK -·-·l

FIG. 9. Chicago, Milwaukee, St. Paul, and Pacific Railroad.

tracks, turnouts, crossings, etc., and halting train movement. Fig. 3 through 5 give quantitative signifi­cance to the effects on train operations of snow and winter conditions. In a study of snow effects it is impracticable to screen out the closely interwoven effects of wind, ice, and low temperatures as these combine with snow.

Delay quantities of fig. 3 and 4 are taken from the 7 a.m. reports of the Milwaukee Road and use the delay nomenclature of those reports. Not all actual delays are indicated as these reports cover only regular trains that were operated. As noted in fig. 3 and 4 many regular trains were annulled because of storm conditions. Also extra trains were not run during the peak of the storm period. Efforts were directed mainly toward getting the passenger trains and one time freight, number 263-264, through. The reports may also be somewhat inaccurate in detail because they were prepared each morning under the stress of emergency conditions. However, the general effects of snow and blizzards are clearly defined.

Fig. 3, 4, 6, and 7 show delays by types and by operating divisions on the Milwaukee Road during the months of January and March 1952. The Milwau­kee is a modern, well equipped, well managed carrier, one of the first ten in track mileage. Its main line extends from Chicago to Seattle and Tacoma via the Twin Cities; Aberdeen, South Dakota; Miles City and Butte, Montana; and crosses the Rocky, the Bitter Root and the Cascade mountain ranges (fig. 9). The selected months represent severe but not necessarily peak conditions. Diesel-electric power is used on most passenger trains and time freights

except on two electrified divisions totalling about 600 mi across the mountains. Steam power is used on extra trains and for emergencies.

Fig. 10 and 11 show the snow and various low temperature data for the Milwaukee Road territory. Maximum snowfall occurs in the mountain areas with a secondary peak area extending from Montevideo, Minnesota, to La Crosse and Milwaukee, Wisconsin. The plains areas of South Dakota and eastern Mon­tana have relatively light snowfall. The lowest temperature conditions, with the exception of the average for the coldest month, which occur in the Dakotas, occur in the Rocky Mountain area. Tem­peratures rise from these cold areas both to east and west, more gradually, however, to the east than to the west. The most notable downward break in these generally ascending curves is caused by altitude m the Cascades.

In the following list the five principal sources of winter delays are summarized from fig. 3 and 4.

Per cent of total weather delays

Delay January March

Thawing out steam lines 4.8 Snow and ice in switches 3.8 1.4 Heavy and drifted snow 11.9 27.2 General blizzard conditions 64.5 37.3 Snow plow delays 10.4 31.3 All other weather delays 4.6 2.8

100.0 100.0

Thawing out steam lines on cars and locomotives (passenger trains only) is entirely a low temperature problem. Snow in switches usually combines snow and low temperature unless the reporting agent is more

32 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

precise in his determination of cause than can be expected. Probably snow is the major factor because these are delays under blizzard conditions.

Heavy and drifted snow implies snowfall or drifts without the additive effects of cold and wind which characterize general blizzard conditions. These two should probably be taken together. As a practical matter the category used often depends on the whim of the individual who reports.

Snow plow delays result from waiting at a station while a plow clears the track or following behind a slowly moving plow in the process of clearing track. These delays can become very large if a plow or its locomotive is derailed. Of the 145 hr 18 min of such delays in March, 111 hr 29 min were lost because a snow plow and a three-unit diesel locomotive became derailed near Aberdeen, South Dakota. It must be remembered, however, that had delays not been incurred by adequate plowing, the total of delays attributable to heavy and drifted snow would have been staggering.

Delays accumulate with equal rapidity if a train becomes snowbound. In the same storm that derailed the plow, a train stuck in a snow drift on single track caused a total of approximately 49 hr delay to itself and five other following and opposing trains.

The grouping of delays by divisions also brings out some interesting features. Both in January and March winter delays were relatively few on the divisions east of the Twin Cities and west of the Rockies.

In January heavy delays were experienced on the Rocky Mountain, Trans-Missouri, and Hastings and Dakota divisions. In March only two divisions, the Hastings and Dakota, and the Trans-Missouri, had significant weather delays. Both months showed the Hastings and Dakota, in a minimum snowfall area, as having the most delays. But the Hastings and Dakota also operates one more through passenger train than the Trans-Missouri. The Hastings and Dakota extending from the Twin Cities to the Missouri River (at Mobridge, South Dakota) traverses a plains area with numerous low rolling hills and many medium depth cuts. The rolling terrain offers no protection against the drive of wind and snow, and the small cuts are conducive to drift formations.

These experiences of the Milwaukee Road bear out the experiences of other railroads that windswept, rolling plains bring about winter and snow difficulties as bad as or worse than mountain areas, provided the mountain divisions are properly equipped for snow removal and large snow slides do not occur.

For contrast and comparison, delays on the Illinois Central are presented in fig. 5 and 8. The Illinois Central is also large, modern, well equipped and

well managed. Its line from Chicago to New Orleans traverses an area generally free from severe winter conditions, but the Iowa, Illinois, and Chicago Terminal divisions experience some of the same difficulties as the Milwaukee, and La Crosse and River divisions of the Milwaukee. This study covering the period August 1951 through January 1952 has very few delays to regularly scheduled trains which are directly attributable to snow. The major cause of delay, general weather conditions, 8 hr 15 min, undoubtedly includes some snow storms. Recorded snow effects account for only 2 hr 15 min. Total weather delays in this six months period were only 40 hr 12 min. Much of this was attributable to low temperature rather than to snow.

The foregoing are the delays that a transcontinental line in the northwestern United States would ex­perience in a normally severe winter period. This presupposes an adequate organization of men, sup­plies, and snow fighting equipment. Normally snow removal becomes a difficult but routine maintenance task so that snow is not a barrier to a modern railroad.

The picture can quickly change, however, from many causes. A train unwisely forwarded may get snowbound and have to be laboriously dug out before snow plows can finish clearing the line. The plow itself may become stuck in a drift or worse yet, derailed in a drift. It is impossible to forecast the occurrence of these incidents except to state that the likelihood of their happening increases as severity of weather conditions increases.

An unfortunate combination of storm occurrences (e.g., blizzard followed by quick heavy thaw followed by another blizzard) or a winter of more than normal severity will develop conditions similar to those in the example year of 1949 when main lines were blocked and trains delayed 24 to 96 hr and branch lines were closed a week to a month.

If adequate organization and equipment are not available, the situation, even in normal circumstances, becomes more serious. Thus in England in 1940 the British railways, having no rotary snowplows and facing blizzards with winds of gale intensity and 10 to 15 ft drifts, had 1500 mi of line out of service for 12 to 72 hr [15]. Again in 1947 with 20 ft drifts they had four lines blocked and plows and locomotives stuck in the drifts [8]. Tracks were out of service two days to two weeks. The line from Barnard Castle to Kirkby Stephen became blocked on February 3. No through trains could run until March 31, when the line was finally opened by hand shoveling.

The costs of snow removal may be substantial. Table 2 shows the totals of Interstate Commerce Commission account items for removing snow, ice,

Industrial Operations under Extremes of Weather

MAY 1957 W. W. HAY 33

TABLE 2. Cost of removing snow, ice, and sand from American railroads in selected years

I. All Class I Line-Haul American Railroads

All districts Eastern district Southern district Western district

Per cent Per cent Per cent Per cent of total of total of total of total

Year Amount expenses Amount expenses Amount expenses Amount expenses

1945 $27,729,650 0.390 $21,536,330 0.759 $ 754,716 0.059 $ 5,438,604 0.185 1948 30,597,600 0.409 19,095,804 0.623 2,091,610 0.144 9,410,186 0.318 1949 22,708,093 0.330 6,084,587 0.221 696,780 0.053 15,926,726 0.565 1950 26,753,994 0.379 13,531,879 0.468 1,586,767 0.119 11,635,348 0.410

II. Selected Class I Line-Haul American Railroads (A) (B) Cost A as

Cost of removing Total railway per cent of Railroad Year snow, ice and sand operating expenses expense B

Union Pacific 1945 $ 545,494 $362,286,584 0.1506 1948 1949 1950

New York Central 1945 1948 1949 1950

Long Island 1945 1948 1949 1950

New Haven 1945 1948 1949 1950

Burlington 1945 1948 1949 1950

and sand, as reported by several example carriers to the Interstate Commerce Commission [4]. While the sums expended are large, they represent only a small precentage of the total operating expenses of a large United States railroad, varying from as little as 0.067 to a maximum of 3.115 per cent with a preponderance falling within the 0.1 to 0.5 per cent range. Yearly variations are worthy of note. The New York Central's cost was 1.177 per cent in 1945, the year of the big Buffalo-Albany blizzard, and 0.739 per cent in 1948, a more normal year. Both the New Haven and Long Island railroads had high costs for 1948 reflecting in part the costs of snow removal from the blizzard starting 26 December 1947. The effects of the western blizzards of 1949 on operating expenses is clearly indicated for the affected roads.

The inclusion of sand removal in this account is of minor importance and does not invalidate these figures as representative of snow and ice costs. There are practically no sand removal costs involved on any major railroad except the Santa Fe, Southern Pacific, and the Rock Island and these all show low

1,376,166 321,403,216 0.4282 5,015,281 317,922,665 1.5775 1,350,648 327,013,967 0.4130

6,834,484 580,680,970 1.1769 4,929,086 667,342,966 0.7386 1,677,916 597,038,307 0 2810 4,102,774 632,848,260 0.6483

314,822 33,978,263 0.9265 785,760 45,528,555 1.6532 172,708 44,404,743 0.3889 138,649 48,872,220 0.2837

1,354,655 142,244,846 0.9525 2,677,867 135,370,333 1.9707

493,470 117,145,462 0.4212 362,665 115,075,645 0.3151

427,839 174,150,921 0.2457 574,372 167,888,010 0.3421

1,097,417 167,265,649 0.6561 482,817 161,964,674 0.2981

costs anyway so that the percentage influence of either snow or sand is small. v. Wind. Wind is not generally considered a serious problem in railroading. It can, of course, cause great loss of life and property when it strikes in the form of a hurricane or a tornado; otherwise it is only an annoy­ance. Wind creates serious problems when its effects are combined with snow, rain, and ice storms and with excessive dust and sand. Tornadoes may occur any­where in the United States, but are most frequent in the midwestern part of the country. Hurricanes affect principally the coastal regions. Strong winds creating dust storms occur in the Southwest and blizzard creating winds blow throughout the snow belt but especially in the Northwestern States, North Central States, Canada and Alaska.

Train delays from drifting sand or from other debris blown onto the tracks, except from tornadoes and hurricanes, are accidental in occurrence and of relatively short duration. Sand drifting is not as extensive as snow drifting but less is required, two or three inches above top of rail, to derail a train.

34 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

Normally drifted sand does not freeze. It is removed by hand, by wedge plow, spreader car, rotary brooms, bull dozer, power shovel, or a combination of these.

The resistive effect of wind on train movements is usually one of reducing the train speed. However, a train, because of track curvature, is seldom moving in a constant direction with respect to the wind. It can vary from tail to quartering wind to headwind within a few miles because of track curvature. A 5 to 10 per cent reduction may be made in tonnage rating where prevailing headwinds are encountered but in most situations the effect is ignored and the train comes in a few minutes late on windy days. The effects of streamlining are beyond the scope of this study.

The resistive effect of wind is often of some im­portance in yard operation. The empty hard-rolling car may actually stop on the ladder before rolling beyond the clearance point. A special move is required then or later by a locomotive to get the car properly placed. Ten minutes to half an hour of delay may ensue. The easy-rolling car may also be stuck if the retarder operator misjudges the wind effect and applies too much retardation. On the other hand, a tail wind can move a car along at faster than safe coupling speed and cause damage by the coupling impact. In most retarder yards and all manual yards, the adverse effects of wind depend largely on the skill, experience, and judgment of the retarder operator or the switching crew. Winds make it difficult to pass signals due to the obscuring effects of dust, and communication through loud speakers and talk-back systems is muffled.

Most water borne operations conducted by a rail­road are carried on in protected waters. Even here, however, waves become heavy enough to slow the movements of barge, car float, or ferry and make steering difficult, sometimes dangerously so.

Tornadoes destroy all but the strongest structures within a relatively narrow range. Actual blockades may last only a few hours but property damage can be critical and may include trains blown off the track and fueling facilities, trestles, and other facilities damaged or destroyed. Bridge destruction causes delays of 2 to 20 days. Hurricane winds also cause property damage similar to that of tornadoes and accompanying rains create flood conditions. Duststorms cause delays varying from a few minutes to two days. vi. Rainfall. Direct effects of rain on train operation are few; indirect effects are many. Unstable sub grades and cuts are protected by "slow orders" which reduce train speeds to 50, 30, 20, 10, or even 5 mph over unsafe sections depending on the seriousness of the condition. If there is a subgrade failure or a slide,

trains will be delayed 2 to 48 hr or even more depend­ing upon the extent of failure, its accessibility, etc. Loss of a narrow side hill bench could tie up the line indefinitely. False "red" indications from track circuit leakage as already noted force the affected trains to crawl from signal to signal at 15 mph, or, at inter­locking plants, to wait until some form of clearance card or order can be given the train by the dispatcher. Washouts and floods may delay trains several weeks. Effects on water borne traffic are discussed in the section on fog.

Train dispatchers are kept informed of rising waters and trains are given "slow orders" or halted clear of danger zones. Occasionally waters rise so rapidly as to isolate the train. All railroads have prearranged detour routes over their own and neigh­boring lines which are used to keep trains moving. Occasionally an entire area is hit so hard that the detour routes will also be impassable and train oper­ations are brought to a standstill. Train movements are restored at the first opportunity but it may be weeks or months before the railroad and its services are back to normal.

During the years 1943 to 1949 and 1951 to 1953, 70 out of 695 train accidents reportable to the I.C.C. were caused by moisture conditions. Of these, 53 were caused by poor visibility (5 by rain, 3 by mist, and 45 by fog). Fifteen were caused by washouts, one by a wash-on, and one by a landslide. These amount to 9.9 per cent of all reportable train accidents due to weather conditions.

7. Accidents

A few train accidents can be directly traced to weather. A review was made of all train accidents reported to the Interstate Commerce Commission for the years 1943-49 and 1951-53. Out of 695 accidents, 94 could be directly related to weather, and of these, 58 were collisions caused by limited visibility. Among the remaining 36 accidents, 15 were attributed to washouts. Some added seriousness is thus noted for the problems of visibility and rainfall. Altogether 13.5 per cent of reportable train accidents were caused by weather conditions. A more detailed state­ment of the accident report analysis is found in table 3.

8. Summary

With the exception of certain combinations of severe conditions, railroads do not stop running be­cause of weather conditions. Railroads can and do operate regular schedules from -70 to 136F. They operate through any winds less than a hurricane in

MAY 1957 W. W. HAY 35

TABLE 3. Relationship of weather conditions and railroad accidents from Interstate Commerce

Commission Reports

Collisions Under conditions of limited

visibility Related weather condition

Head-end Rear-end Side Due to slippery rail

Derailments Under conditions of limited visi­

bility applying in movements at drawbridges, interlockers, switches, or on curves

Due to kinked track in hot weather Due to slippery rails on steep grades Involving grade crossing accidents From washouts, sinking fills, or

collapse of bridges Due to material washed onto track Due to rockslides Due to landslides

Rain Mist

1 3

5

15 1 2 1

2

1 3 1

Fog Snow 12 3 20 9

7 1 1

40 13

5

3

Total

17 32 9 2

60

7 3 1 4

15 1 2 1

94

The above accidents are those showing at least a moderate causal relationship between weather conditions prevailing and mishaps occurring.

Total number of I .C. C. accident reports examined: 695 (1943-49, 1951-53 through April, 1953).

Total number of accidents related to weather conditions: 94. Proportion of railroad accidents into which weather enters as

a significant factor: 13! per cent.

violence. Rainfall alone is no handicap. Humidity has no marked effect. Tracks are kept open through the heaviest of snowfalls and through drifts of 20 to 30 ft in depth. Delays do occur but under normal conditions these are purely nominal, usually being only a few minutes, and seldom exceeding 24 hr. Even when certain lines are blocked by severe conditions, traffic, in the United States at least, suffers very little delay because it is detoured over other routes or transferred to trains on tracks that can be negotiated. However, the importance of minor delays and speed reduction should not be underestimated. The severity of weather effects varies inversely with the preparation and planning for those conditions. The worst delays are likely to occur where a railroad (or its personnel) has had little experience with a climatic factor in effect.

The question may well be asked why trains are not

delayed more than they are. The answer lies in the

organization of men, materials, and equipment to

carry on a continual and unremitting routine battle

against adverse weather and all other situations

which might cause blockades.

REFERENCES

1. Committee 16, American Railway Engineering Association, 1942 : Train resistance of freight trains under various con­ditions of loading and speed. Proc. A mer. Ry. Eng. Assn., 43, 51-71.

2. Skavn, S. V. and C. E. Haug, 1947: Norse make scientific attack on heaving track. Abstract in Railway Engineering and Maintenance, April 1948, pp. 404-406 of paper pre­sented at Second International Conference on Soil Me­chanics, The Hague, Holland.

3. Wright, R. M., D. E. Taylor, R. Ferber, and F. S. Dotson, 1953: An economic investigation of solid journal bearing operation in freight service on two large Class I Railroads. Urbana, Illinois, University of Illinois Engineering Ex­periment Bulletin No. 406.

4. U. S. Government, Statistics of United States Railways, 1945-1950, Section A-1, Washington, D. C., Interstate Com­merce Commission.

5. Unsigned, 1952: Snow-and lots of it. Modern Railroads, 7. no. 7, 185-187.

6. --, 1945: Freight congestion continues serious. Railway Age, 118, no. 5, 266-269.

7. --, 1945: Roads gain in battle against weather. Ibid., 118,

no. 6, 300-303. 8. --, 1947: The London and Northeastern v~ Winter 1947.

Ibid., 122, no. 26, p. 1315.

9. --, 1947: Hurricanes destroy mainline trestles. Ibid., 123, no. 13, p. 538.

10. --, 1935: Dust storms bring new problems to maintenance men. Railway Engineering and Maintenance. May, 276-280.

11. --, 1946: Machines keep terminals open in winter. Ibid., December, 1294-1296.

12. --, 1949: Western lines h1t by worst blizzard in history. Ibid. February, 142-143.

13 --, 1951: To thwart salt air corrosion. Ibid., February, 127-129.

14. --, 1951: Record floods hit railroads hard over wide area. Ibid., September, 820-823.

15. --, 1940: Arctic weather on the railways. Railway Maga­zine, 86, 190-192.

16. --, 1954: The Q. N. S. and L. says ..• never! Track and Structures, April, 55-56.

APPENDIX I. The effect of weather on operation of Lake Michigan train ferries

by Thomas Scott, University of Arkansas

Although most navigation on the Great Lakes is officially suspended each winter from December 15 until a variable date in March, four railroads operate

train ferries across Lake Michigan throughout the year. The rigors of this operation require the use of large and powerful twin-screw steamers, each with a.

36 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

capacity of 34 to 38 freight cars. Normal crossing time on the various routes is 5 to 8 hr, but on several days each year weather conditions become severe enough to delay arrivals and cause sailings to be postponed for several hours. More than a 24 hr delay is considered exceptional, but on rare occasions more serious disruptions do occur.

Delays are chiefly caused by high winds and their accompanying heavy seas, or by heavy ice floes which develop in exceptionally cold winters. Fog is a minor problem. Heavy snow does not materially affect operation of the ships themselves but may result in cancellation of trips if main lines or yards of the railroads served are seriously crippled.

The force of a: strong head wind suffices to slow a ship down materially. Heavy head seas will further arrest its progress, and may oblige the vessel to heave to or seek shelter. Thus in October 1919 one steamer breasting contrary winds and seas required 27 hr to make what is normally a 6 hr crossing. Large seas coming from either side may oblige the vessel to alter its course to avoid heavy rolling. When violent motion of the steamer cannot be avoided, it may damage unsteady freight car loads or even cause some of the cars to upset. In January 1918 three carloads of timber upset in the Ann Arbor #6, and unloading of the vessel was delayed for 19 hr. Two years later a similar mishap caused an unloading delay of 10 hr. Even though cars are fastened by rail damps, body jacks, and tie-down chains, these have been known to break loose in exceptionally heavy seas. In such a case the ship may be obliged to let the loose cars run off into the lake, though the resulting change in ship's trim may be a serious hazard. To avoid these problems, ships occasionally defer sailings for 24 to 48 hr. In December 1917 one steamer lay for 56 hr in Frankfort while a gale blew itself out.

Because Lake Michigan is narrower in the northern part than toward the south, average 65 mi as against 85, the crossings in the upper lake are shorter; and here, too, steamers have the added advantage of being able to find shelter behind the Manitou or Fox Islands if overtaken on the run by dangerous condi­tions. On the longer run between Muskegon and Milwaukee no such protection is available, and the greater breadth of the lake in the southern part permits the development of larger seas. These over­whelmed the train ferry Milwaukee in 1929 and she sank with all 55 hands. But the fact that the Ann Arbor #4 sank while entering the northerly port of Frankfort in 1923, and that the Pere Marquette's City of Flint was driven ashore at Ludington in 1940, may show that in no part of the lake can the steamers count on avoiding the stress of winter storms.

Ice conditions vary greatly from year to year and in different parts of the lake. In mild winters no delays from ice are experienced. Such was the case in 1920-21, whereas in 1917-18-19 much ice formed and caused significant delays. The lake seldom freezes completely across, and steamers are not often troubled far offshore. Delays are caused mostly by floe ice which drifts before the wind and lodges against the shore and within the harbor entrances on the lee side of the lake. There it accumulates as a mushy mass several miles in breadth, normally showing only a few feet above the water but extending below the surface to a considerable depth, there tending to clog condenser intakes of ships attempting to force a passage. Included in the mass are large chunks of ice which may knock the blades off ships' propellers, requiring delay in port for replacement of propeller blades.

Occasionally floe ice becomes sufficiently compacted to trap steamers for days. This trouble occurs most often in February, and most commonly in the northern part of the lake-especially in Green Bay and its tributaries. Thus, two steamers lay for a week in the ice near Manistique in February 1910; and three vessels were caught for a week off Frankfort in February 1917.

Ice conditions were moderately severe in the winter of 1935-36. In March 1936 Ann Arbor #6, while bound from Manistique for Frankfort, was stuck fast several times and delayed over 48 hr on a passage normally requiring 7 hr.

In February 1943 the same vessel was delayed over 65 hr by heavy windrowed ice while en route across Green Bay from the Sturgeon Bay Ship Canal toward Menominee. This leg of the voyage normally requires 1 hr 30 min. The relatively quiet waters of Green Bay especially favor development of heavy ice; and the port of Gladstone, on Bay de Noc, off the north end of Green Bay, suffered so severely from ice conditions that a train ferry service once established there had to be abandoned.

In addition to winds, seas, and ice on the lake, snow conditions ashore sometimes cause ferry trips to be delayed or cancelled. Because the main line of the Ann Arbor Railroad was snowed in from 19 March to 4 April 1923, the steamers could handle no traffic and were tied up. And on 13 February 1936, the Chicago and North Western's Manitowoc yard was snowbound for 18 hr and car-ferry traffic in the port was delayed accordingly. Thus the railroad steamers are affected by railroad tie-ups as well as by maritime hazards, But in general, schedules of the train ferries appear to be less disrupted by severe winter weather than are operations of the railroads themselves.

INDUSTRIAL OPERATIONS UNDER EXTREMES OF WEATHER

by

J, A. Russell; W. W. Hay; J, W. Waters; H. E. Hudson, Jr.; J, Abu-Lughod, W. J, Roberts, and J, B. Stall;

A. W. Booth and E. F. Taylor. Edited by J, A. Russell.

III. WEATHER LIMITATIONS TO THE CONSTRUCTION OF INDUSTRIAL ESTABLISHMENTS

By J, W. WATERS .

(Original manuscript received 27 March 1956; revised manuscript received 7 June 1956)

ABSTRACT

The effects of weather conditions on the construction industry are discussed. It is concluded that low temperature, particularly where it has resulted in permafrost, imposes the most severe restrictions on the construction of buildings. Sleet, ice, and snow rank next as impairments to construction activity; rain and wind impose periodic difficulties which may occasionally reach serious proportions.

This paper is an attempt to determine the weather conditions which impose specific and definable degrees of efficiency limitation upon the operations involved in the construction of industrial establishments. Material presented is based upon consultation with contractors and engineers* through personal interview and by means of questionnaire.** It is augmented by pertinent engineering literature.

In any consideration of the effect of different weather conditions upon the operations of any industry, both operational efficiency and cost of production must be considered. For the purposes of this problem it is assumed that all conclusions con­cerning the adaptability of construction operations to weather extremes pertain to operations that are characterized by costs of production and efficiencies which are typical or average for United States estab­lishments.

The construction of industrial establishments con­sists of a variety of types of operations which must

* T. C. Shedd and W. H. Munse, Department of Civil Engi­neering; W. L. Collins, Department of Theoretical and Applied Mechanics, University of Illinois.

**The companies consulted were:

1. Morrison-Knudsen Company, Boise Idaho. Alaskan District, 603 Hoge Building, Seattle 4, Washington.

2. Peter Kiewit Sons' Company, Philadelphia, Pa. Seattle Dis­trict, 1300 Aloha Street, Seattle, Washington.

3. C. F. Lytle and Green Construction Company, 321 Locust Street, Des Moines, Iowa.

4. McLaughlin, Inc., Box 1824, Great Falls, Montana. 5. Vaile-Sommers Construction Company, P.O. 4096, Interbay

Station, Seattle 9, Washington.

37

be treated separately if meaningful generalizations are to be obtained. It cannot be assumed that the different operations involving different equipment in the construction of different units would behave similarly upon exposure to extreme weather condi­tions. Consequently for the purposes of this research it becomes necessary to recognize the following major divisions:

1. Surveying 2. Materials stockpiling 3. Excavation 4. Pile driving 5. Concrete form construction 6. Concrete pouring 7. Masonry 8. Structural steel work 9. Carpentry

10. Roofing 11. Plumbing and Heating 12. Electrical installation 13. Painting 14. Construction of miscellaneous structures 15. Road and rail siding construction

1. Low temperature

The temperature which is considered optimum for construction of industrial types of establishments pertains in most instances to worker efficiency. Approximately SO to 7SF is considered optimum for

38 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

most operations particularly if much labor is involved. A temperature of 60F has been stated as optimum for heavy manual labor; 67F for semi-skilled moderate to light manual labor. Below approximately SOF problems begin to arise which tend to reduce the efficiency of some types of construction operations, while overall labor efficiency begins to decline gradually.

At temperatures down to approximately 32F manual work is not appreciably impaired. Some reduction in efficiency occurs between 10 and 32F dependent upon the type of work and the condition -of the other climatic elements, in particular, wind and snow. At temperatures below approxil)lately 10F problems occur which interfere with construction operations to a much greater extent. The following are the conditions which have been experienced in undertaking construction operations down to and below 10F.

i. Surveying. Surveying operations are affected by low temperatures in two major ways. At very low temperatures allowances must be made for the shrinkage of parts of the instruments. Secondly, surveying operations involve considerable inactive outdoor work in which it is desirable to make adjust­ments with bare hands. Consequently surveyors be­come subjected to the cold air. Work efficiency drops considerably at temperatures below approximately 32F. The lower the temperature becomes, the more frequent the need arises for interruptions to warm up. It is estimated that the 0 to -10F zone is the low temperature limit : J :::urveying- as normally practiced by United States CG .. "r.1.cting extablishments. Depend­ing upon the condlt.on of other weather elements, particularly wind and snow, surveying can be, and has been continued at temperatures down to -30 to - 35F. A marked decline in efficiency occurs at tem­peratures lower than - 35F so that it is not considered practical to attempt surveying beyond that limit.

ii. Materials stockpiling. Most construction materials -sand, gravel, cement, lumber, structural steel-can be stockpiled without regard to temperature. Some materials such as brick, tile, and concrete blocks, although not affected by low temperature alone, suffer deterioration when low temperatures are ac­companied by precipitation or high humidity condi­tions. Shelter from extremely low temperature must be provided for water and explosives. The normal storage precautions which must be heeded at a tem­perature of 32F also apply at - SOF. Thus, extremely low temperatures do not impose unusual restrictions upon storage practices.

iii. Excavation. The performance of excavation oper-

ations can be analysed in terms of three differing aspects. There can exist low temperature limits to

(1) the operation of excavation machinery, (2) the performance of work by labor, and (3) the practi­cability of the actual excavation operation. Each of these will be discussed in turn.

(1) Excavation machinery. Vehicles and equipment utilized for excavation provide adequate service at temperatures down to OF. At lower temperatures problems begin to arise which impose restrictions upon operations. At temperatures down to OF minor operational problems arise which can be readily met (e.g., need of antifreeze at subfreezing temperatures). At temperatures between 0 and -SOF excavation vehicle and equipment operations are feasible within certain limitations. At, and below these temperatures the following difficulties occur:

a. Weatherproof cabs or shelters must be mounted on open equipment for the protection of the operators. Oversize heaters, ventilating fans, or defrosters need to be provided on shovels, tractors, graders, heavy duty trucks, etc. [17].

More room is required in the operator's seat and cab because of the great bulk of the operator's clothing. The handling of pedals, knobs, switches, and gears becomes cumbersome unless allowances have been made for the performance of an operator dressed in arctic clothing. A comparison of several of these dimensional differences is presented in table 1.

b. Greases and lubricants exist which are satisfac­tory at -SOF although greases which are satisfactory at such a temperature become excessively viscous at OF. Below -SOF there is difficulty in distributing the lubricant to the critical bearing points [7]. Engine oils can be diluted with kerosene or gasoline at temperatures as low as -70F to prevent solidification. The quantities to be added vary from 5 per cent kerosene for - 25F to 20 per cent gasoline for -70F. When an engine has been running for some time the diluent will vaporize so that it must be replaced prior to every idle period in order to facilitate future

TABLE 1. Space requirements for arctic clothing [7]

With warm With arctic weather weather clothing clothing Difference

Parts measured (inches) (inches) (inches)

Chest 37 61 24 Hips 37 64 27 Ankle 9 28 19 Head 23 38 15 Wrist 7.5 21 13.5 Foot (length) 11 14 3 Foot (width) 3.5 5 1.5 Breadth across shoulders 18 32 14 Thickness through chest 10 17 7

MAY 1957 J. W. WATERS 39

starting. This technique is not completely satisfactory because it results in excessive wear on parts. A dis­advantage of utilizing oils of extremely low viscosity is that they lubricate unsatisfactorily at moderately higher temperatures; an oil having a pour point of - SOF would not be completely satisfactory even at temperatures above - 35F. Synthetic oils of the polyalkylene glycol type have advantages in engine starting, but develop sludge under operating condi­tions. Naphthalene base oils with special additives have been used, although a slight solubility for water is evident. Similar oils and special greases have been developed for general machinery and hydraulic transmission gears. Nonspreading lubricants developed for instruments and fine mechanisms may solidify at low temperatures and may, on occasion, be replaced by powdered graphite. The best low temperature lubricant must be specially designed for the particular job [35].

c. Characteristics of the coolant may change. The cooling system, which is designed to do a cooling job under conventional service must under arctic condi­tions keep the engine warm, rather than cool. Although mixtures of antifreeze which will remain fluid at very low temperatures (down to - 65F) are available, most of these mixtures are extremely unstable when subjected to sudden changes of temperature such as occurs when the coolant is used as a means of trans­mitting heat from a heat source to an engine [8].

d. Gasoline fails to vaporize, and diesel fuel does not flow properly at - SOF.

e. The cranking system becomes inadequate. The power demands in starting become increasingly great, while the cranking device performance is lowered. Standard batteries are too weak (60 to 80 amp hr) for successful vehicular operation. Batteries with 140 to 160 amp hr capacity are recommended [16, 24]. Block heaters can be provided for idle periods if shelter is not available. As an alternate vehicles can be kept running continuously for up to a week until they are shut down one at a time for servicing [28]. Methods of providing heat for starting diesel engines include a system of using a nonelectric, natural draft, manually ignited pot-type heater, and a hot air heating system.

Military equipment winterized for arctic service must be able to self-start and operate at -40F. Starting must be possible with the aid of temporary kits at temperatures between -40 and -65F. Generally, the problem of meeting -40F conditions is not considered unduly severe. However, as the temperature drops from -40 to -65F, extensive changes occur in some of the materials and items of primary importance (e.g., oils, battery, coolant, etc.,

cited above) with the result that overall operational efficiency becomes reduced markedly [8].

f. Vehicular maintenance needs increase. Also the time .required in the performance of maintenance tasks increases. Thus more vehicles and larger main­tenance facilities are needed for the various tasks.

g. Many materials such as steel, rubber, plastics, become defective. Rubber belts become stiff. Chain or gear drives become desirable. Synthetic rubber materials are not satisfactory.

The brittle fracturing of steel parts of vehicles and equipment becomes a problem at very low temper­atures. At -30F it is estimated that the usual grades of steel in heavy power equipment lose up to 50 per cent of their strength with the result that parts snap which are exposed to impact forces. Particularly vulnerable are dipper bails, dipper sticks, booms, side frames, and even the main lower frames of power shovels, and axles and frames on trucks.

Ferrous metals such as ordinary carbon and low alloy constructional steels exhibit this characteristic loss of toughness suddenly, when certain low tem­peratures are reached. On the other hand, most of the nonferrous metals, such as aluminum, copper, nickel, lead, and alloys of these metals are relatively free from such behavior. Also certain types of stainless steel do not have this transition temperature zone above which the metal is ductile and below which it is brittle.

This transformation of tenacity appears to be evident only when the surface of the steel has been notched in some manner, and when a force which sets up complex stresses about the notch is applied with extreme rapidity. The existence of the notch actually approaches the duplication of a real steel structure situation in which numerous "notches" exist in the form of drilled holes, etc. Because of this property in steel, unexpected failures have occurred which have resulted in the complete destruction of large struc­tures. Apparently no satisfactory theoretical explana­tion of this characteristic transformation exists. Consequently, impact-brittleness tests are employed by metallurgists and engineers to provide reliable information about the tendency of materials to fail by brittle fracture. The tests also serve as a useful device for securing consistency of product [40].

Generalizations pertaining to the temperature zone at which this transformation takes place are not sufficiently reliable, however, that they can be applied to any specific quality of steel. Results of tests which are used to measure the "notch-brittle" sensitivity of a steel have been shown to vary up to 20 or 25F for specimens from the same ingot, and up to SOF for specimens from the same heat. They have

40 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

shown that even standard deviations range from 6. 7 to 20.4F [39]. Generally, however, most ordinary carbon steels reach the transformation zone at between 0 and -30F. At -30F it can be expected that such steels will either have reached the brittle state, or will be close to it.

Despite this, however, it appears that no deliberate selection of qualities of steel for low atmospheric temperature exposures is made for structures within continental United States. Qualities of steel do exist whose transformation zones occur at temperatures lower than the absolute minima which have been recorded upon the earth's surface. Thus it is possible that equipment and standard steel structures could be built to withstand such extremely low temperatures ( -90F) without the necessity of modifying the design, or of substituting other materials for the steel. It is pertinent to note, however, that only in exposed structures such as trucks and mechanical equipment, bridges, trestles, or outdoor cranes, are steels sub­jected to the minimum atmospheric temperatures; the structural steel framework of a building is shel­tered since it is covered by the siding of the building.

Physical qualities of steel other than impact brittleness do not seem to display the tendency to deteriorate at low temperatures. Ferritic steels and iron appear to be no worse engineering materials at subnormal temperatures when strength and tough­ness are evaluated by the usual static methods upon unnotched specimens. In fact, it seems that increased strength due to decrease in temperature is accom­panied by less loss of ductility than when comparable increase in strength is produced by other means at the command of the metallurgist [18]. It is also of significance that changes brought about by a decrease in temperature are generally of a temporary nature [40].

Considerable attention has also been focused upon the behavior of welds at low temperatures. The general conclusion seems to be that properly com­pleted welds stand up to low temperature embrittle­ment tests as satisfactorily as do the metals which the weld joins [10, 38, 40]. (2) Labor. In general workers involved in excavation operations are able to perform their tasks satisfactorily at temperatures down to OF. Below OF worker efficiency begins to decline rapidly, particularly if other inclement weather conditions, particularly snow and wind, prevail in association with the low temper­atures; consequently, under many conditions at temperatures near OF workers become inefficient. However, if other conditions are satisfactory, and if workers are properly clothed, activity can be satis­factory at -40F [17]. At temperatures below -SOF

Temperature

70F 20 0

-23 -40

-50

-80

TABLE 2. Working efficiency of man at various temperatures [45]

100% 75 50 25 14

Percentage of efficiency

(Point where arctic natives normally become inactive)

10 (Point where man can no longer per­form outdoor mechanical work but must spend practically all of his energy to survive)

0

in nearly all instances excavation work must cease. Table 2 presents an estimate of the working efficiency of man at various temperatures.

(3) Excavation operations. The actual excavation operation becomes very severely impeded in sub­freezing temperatures because of the difficulty in digging into frozen soil. The interference is augmented at low temperatures by the declining efficiency of equipment described above. Consequently excavation is usually not undertaken when the soil is frozen (usually not below 20F). Dependent upon the actual frost condition in the soil however, excavation can be completely feasible down to OF. If the soil is solidly frozen operations can proceed only with great diffi­culty, generally including thawing as excavation progresses, usually with steam. Such operations can cost three times as much as excavation in unfrozen soil. In some instances drilling and blasting techniques are adopted [17]. Temperature exposures of -40 and - SOF can result in a frost penetration of up to 10 ft into exposed surfaces. Excavation is thus possible at even lower temperatures (i.e., at -70F) but only if the expensive techniques such as thawing and drilling are adopted [29].

A problem characteristic of moderately low tem­perature, as well as extremely low temperature, is the freezing of excavated material to the sides and bottoms of trucks and other similar load carrying equipment. The severity of the problem depends to a considerable extent upon the length of time during which the load remains in the vehicle. One of the more successful methods of dealing with this problem is to heat the truck boxes by piped exhaust gases. Also, antifreeze compounds such as mixtures of low grade fuel oil and organic solvents can be sprinkled on the box floor ; this is a practice used in rail hauling of earth materials [17].

iv. Pile driving. The most significant effect of low temperature upon pile driving involves the problem of driving piles into frozen soil. This topic is considered

MAY 1957 j. W. WATERS 41

in detail below in the section on ground frost. Com­pared to the problem of frozen soil, other weather restrictions are less severe. Pile driving equipment can be designed to operate in extremely low temperatures, in a heated shelter if necessary, but normally piles are not driven in temperatures lower than 20F. At temperatures lower than OF it is not considered economical to drive piling. Despite these limitations, in areas of permafrost it is considered best to drive piling during winter and early spring although earth thawing is a necessity [45].

v. Concrete form construction. The erection of concrete forms involves much outdoor work by carpenters, steel workers, and general labor. Productive efficiency is markedly reduced if low temperatures necessitate work in heavy cumbersome clothing, Many of the tasks involve climbing, reaching, and working in restricted spaces. Gloves are a hindrance. Conse­quently at only moderately low temperatures work must cease unless operations justify greatly increased costs. Actually this work has been continued at a temperature of - 20F, although such an operation was not considered to be economical. At temperatures lower than - 20F both heat and shelter are necessary to facilitate operations, a practice not adaptable to the construction of large units. The low temperature limit to economic operation actually occurs between 0 and 10F. Because of much greater efficiency it is desirable to construct forms at temperatures which exceed 32F, and, if possible, 40 to 50F.

The task of stripping concrete forms from a hardened concrete structure can be greatly impaired at temperatures below 32F if the forms have become frozen to the concrete. Such a delay in the removal of forms can interfere with succeeding jobs. Generally, however, work involved in stripping forms is not as sensitive to low temperatures as is work involved in erecting them.

vi. Concrete pouring. [5] Because of the susceptibility of freshly poured concrete to frost damage, the pouring of concrete is limited to temperatures higher than 32F unless increased costs, and the possibility of inferior quality are acceptable. Even under the most ideal circumstances the pouring of concrete at temperatures below 10F is considered by most operators to be uneconomical; this temperature, with little or no wind, is the lowest for practicable pouring of large, thick sections such as airstrips [11]. Conse­quently this discussion of concrete pouring at temper­atures below lOF pertains mainly to the technical feasibility of the task.

There do exist, however, possible exceptions to the above generalization. Certain types of concrete jobs

have been undertaken with considerable success ex­posed to sustained temperatures as low as -20 to -30F. These were all large projects (i.e., dams) for which investments in complete protective and heating devices were justified by the size of total operation­the investment being minimized by the advantage of mass pouring of concrete in relatively confined areas. It has been found that it is more economical to invest in winter protection to facilitate all-year operation if the project is of a size that takes three or four years to complete, rather than attempt to operate only during the warm season. This is particularly true in areas in which the average temperature falls below 32F for six months of the year, below 10F for three of those months, and below OF in January. Overall cost of concreting on such large projects under winter conditions with sustained exposures of - 30F has been only 8 per cent higher than for comparable warm weather operations, including the entire cost of installing and operating a boiler plant, steam lines, the heating of aggregate and water, and the protection and heating of work areas and forms [27]. The major changes in practices and equipment are listed below.*

1. A boiler plant is installed to provide steam heat.

2. Steam pipe lines are wrapped in asbestos in­sulation, or laid in shaving or sawdust insulated box enclosures.

3. Water mains are traced by steam lines, both being wrapped in asbestos and housed in an in­sulated box enclosure. Extra long water pipelines (i.e., sufficiently long that steam heating is not practicable} are heated by a low voltage hotbed cable.

4. The entire concrete mixing plant is housed. 5. All aggregate preparation is completed during

the warm season, so that winter work may be based upon stockpiled supplies.

6. Water is stored in an elevated enclosed tank. In the tank submerged steam coils and jets thermo­statically maintain the water at temperatures up to 180F. By adjusting the thermostat, and thereby the heat of the water, it is possible to control accurately the heat of the concrete at discharge from the plant, despite atmospheric temperature variations.

7. Transportation of the concrete to the form is accomplished by conveyer, truck, or pipeline. Conveyers are housed and heated by steam pipe­lines. Concrete is trucked up to about one mile at temperatures above OF without any covering. For

* The expedients listed were used to facilitate construction of a hydroelectric dam.

42 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

longer distances and lower temperatures tarpaulin covers are necessary, and, in extreme instances, box heaters. Pipelines for the concrete are heated to avoid freeze-ups in case the pumping ceases. Also, steam is forced through the pipes prior to concrete pumping so that freezing will not occur as the first batch of concrete moves along the line.

8. As large a unit as possible is poured continu­ously. Where possible forms consist of 3/4 in. plywood, since lumber panels (1 X 6 in. boards) provide much less protection, and make necessary additional tarpaulin protection at low temperatures. A platform is built over each pouring unit, the entire structure being enclosed and roofed. Unit heaters (fan-backed steam radiators) are lowered by block and tackle to thaw the base of the form prior to pouring (steam jets are also used for this purpose). As pouring progresses the heaters are raised, until eventually they are left suspended for about 72 hr over the finished surface of the "pour". Recording thermometers and thermocouples facil­itate accurate control of the temperature. Corners and edges are the most vulnerable to frost penetra­tion, and, if necessary, heaters are installed outside at the corners.

9. For thin wall sections of small yardages, housings of tarpaulins are built to envelop the form completely, and make heating feasible. Where numerous small quantities of concrete are placed in the same general area, as in the construction of a power house, the entire area in which construction is to proceed is housed beneath a tarpaulin and wooden shelter supported on Bailey bridging.

10. Winter operations involve greatly increased fire hazards arising from the use of heaters and improvised tarpaulin and lumber shelter structures. Work such as welding in confined enclosures can be dangerous; adequate precautions involve barring salamanders, flame proofing of tarpaulins and critical lumber structures such as conveyer housings, and installing a system of fire hoses and hydrants. For large projects permanent fire fighting equip­ment and firemen are desirable.

Another experience pertains to the erection of a reinforced concrete three-story industrial building occupying approximately an acre, during a protracted period of cold weather [14]. Walls of canvas were erected outside the building walls to a height of 10 ft above the second story floor. Over the entire structure a frame roof was built in four sections, supported on columns or shores that rested on jacks. This tem­porary roof was raised as work progressed. The roof provided protection from snow and supported a

lighting system which facilitated 24 hr a day opera­tions. Steam heat was provided where necessary. Only that volume of the enclosure where concreting was actually in progress was heated. Each slab was heated by 12 unit heaters, 8 below and 4 above. By this means the working space was kept between 60 and 70F while outside temperatures of 15F prevailed.

It is technically possible to pour concrete at extremely low temperatures (e.g., -68F) [26, 30], but for structures of great size it is neither economical nor practical. Experience of one major operator in attempting a large construction project during an Alaskan winter resulted in a decision to avoid all such contracts in the future. The company lost money on the contract because operating costs reached four or five times anticipated costs.

If reinforced concrete buildings are to be constructed in areas which experience a very great temperature range, expansion joints must be provided, although they are expensive and difficult to maintain. In relatively short buildings expansion and contraction can be provided for by additional reinforcing. vii. Masonry. The construction of masonry struc­tures is even more sensitive to low temperature than is the construction of concrete structures, largely because it is laid in thinner sections [6]. Generally masonry construction has not been attempted in areas of extremely low temperature because it does not stand up to conditions of instability which characterize permafrost. There is, however, a recent trend toward using concrete block masonry in such areas, not in the form of load bearing structures, but as "curtain" walls, because of their high insulation qualities. It is considered that concrete is better insulation than units of insulated sheet metal.

The economic low temperature limit for masonry is considered to range between 10 and 3SF. At lower temperatures the quality of work tends to decline, and the costs of production rise. Temporary shelters and heat become necessary [1]. Stockpiles need to be sheltered.

Examples of work at low temperatures indicate that although masonry might not be considered economic, it is technically feasible. Stone foundations have been laid at -30F [47]. Cement mixer, sand, and gravel are placed in a heated shed; steam heat is supplied while the mortar sets. A strip-reinforced brick smokestack 140m high was constructed during temperatures as low as - 58F and exposed to snow storms. Heaters at working level supplied by a central heating system were placed both inside and outside the stack [9]. The strength of masonry upon thawing has been found to be 75 per cent of that laid under summer conditions, but it approaches the

MAY 1957 ]. W. WATERS 43

strength of summer masonry about one month after thawing [36].

viii. Structural steel work. Structural steel work is not completely satisfactory at temperatures below 32F, although some operators consider it to be economically feasible down to 10F, and technically feasible down to - 20F. At low temperatures work tends to become inferior. Welding, which is more sensitive to low temperature than riveting, is being used increasingly in structural steel work. Riveting, although generally limited to temperatures above 10 to 15F, has been done at -40F.

For moderately cold weather erection, structural steel is preferable to either reinforced concrete or masonry. The operations involved in erecting a structural steel building are less vulnerable to low temperature interference than the other two, although the difference in degree of vulnerability is not great. Steel is delivered ready for assembly. Immediately after erection it assumes its full structural strength­a property not characteristic of reinforced concrete or masonry structures. As a disadvantage, structural steel work is much less adaptable to being undertaken beneath temporary shelter structures. Because it generally involves large units of steel and large equip­ment such as cranes, temporary housings are im­practical. Thus, whereas much concrete or masonry work can be sheltered and heated if necessary, so that workers and materials are not exposed to atmospheric conditions, steel workers and their equipment are exposed. At extremely low temperatures, therefore, it seems that structural steel work is less practicable than concrete or masonry.

ix. Carpentry. Carpentry work is not greatly inter­fered with at temperatures down to about 10F. Since man's estimated working efficiency drops rapidly at temperatures below 10F, carpentry work rapidly be­comes less efficient. A temperature of - 20F is considered to approximate the economic limit (table 2). At temperatures between 10 and -20F work efficiency depends upon the condition of the other climatic elements, in particular, wind and snow. If the distinction is made between rough and finished carpentry work, it can be generalized that the former is less sensitive to low temperature conditions than the latter. (Concrete form construction is considered to be rough carpentry work). Much finished carpentry is done inside the buildings after they have been closed in, so that exposure to weather is eliminated.

x. Roofing. The application of built-up asphalt roofing becomes seriously interfered with at temperatures below 40F. Thus, roofing is possible at much lower temperatures only if some other type of material

such as sheet metal or shingles is applied. If such is the case, temperature limits exist which are com­parable to those for carpentry work (discussed above).

xi. Plumbing and heating. Plumbing and heating work is mostly confined to the interior of buildings after they are closed in. Work that must be undertaken outdoors can be planned for periods when weather interference is at a minimum. Work becomes seriously hampered at temperatures below 35F; at - 20F the work becomes economically impractical. The difference between the feasibility of outdoor and indoor work can be very great since a temperature differential between the two of 130 to 140F can exist [3].

xii. Electrical installation. Most of the work involved in installing electrical systems in industrial buildings is undertaken after the form of the building has been completed. Work can proceed indoors. Thus electrical work is usually not vulnerable to low temperature, or other kinds of climatic interference. There does not exist, therefore, a low temperature limit to electrical work. However, work on outdoor electrical installa­tions is subjected to limitations imposed by weather. For practical purposes tasks cannot be performed at temperatures much lower than -20 or - 30F.

xiii. Painting. Painting is neither economically nor technically practical at temperatures lower than 32F. Satisfactory results cannot usually be obtained if paint is applied at temperatures lower than about 50F. Painting can, of course, be facilitated if the entire structure to be painted is enclosed and heated. Indoor painting is feasible since air conditions can be con­trolled. In most types of construction painting can either wait until optimum weather prevails, or until the work area becomes completely enclosed within the building. A temperature exceeding 60F is desirable for applying varnishes and enamels [21].

xiv. Construction of miscellaneous structures. The fol­lowing low temperature limitation conditions pertain to the construction of miscellaneous structures typical of many standard types of industrial establishments.

(1) Smoke stacks. Brick smoke stacks are generally considered to be the least satisfactory of the types of stack construction in areas in which low average temperature conditions create a condition of perma­frost. However, the actual construction of stacks of all types is greatly limited by weather conditions. Steel stacks are considered to be the most satisfactory; they are preferred to reinforced concrete stacks because of their greater degree of flexibility. At sub­freezing temperatures shelter and heat must be provided for all types, so that winter construction of stacks is not considered economical. Nevertheless, as

44 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

indicated earlier, masonry stacks have been con­structed at extremely low temperatures on permafrost. (2) Water towers. Unless water towers can be en­closed and provided with heat, they are not used in extremely low temperature areas. Pressure systems can be more readily enclosed and heated.

xv. Road and rail siding construction. There exist low temperature limitations to the construction of the receiving and shipping facilities of an industrial establishment. The construction of entrance roads, workers' parking areas, truck unloading areas and railway sidings requires outdoor work comparable with that discussed under Excavation and Concrete pouring. Generally such construction work is not undertaken in winter weather at temperatures lower than 32F. If necessary temporary roads, etc., can be constructed during the winter to serve until permanent installations are competed in the summer.

xvi. Water. The availability of water is a critical factor both during the actual construction operation and afterward, since water is necessary for all in­dustrial establishments. In constructing an industrial establishment which will utilize much water, the problem arises more out of the anticipated demand for the industrial establishment than out of the demand created during the construction. During the actual construction operation water is required both for domestic use and industrial use. The former is needed for drinking water, and to supply the camp or community installations. Industrial water is needed for mixing concrete, washing aggregates, curing con­crete, and for cleaning up for new pours. As an example of the water requirement in the construction industry the building of a certain dam consisting of 1,000,000 cu yd of concrete necessitated a raw water storage tank of 100,000 gal. The consumption per hour during operations averaged 118,000 gal of raw water, and 3750 gal of fresh water [2].

TABLE 3. Estimations of low temperature limits to economic construction operations

1. Surveying 2. Materials stockpiling 3. Excavation 4. Pile driving 5. Concrete forms 6. Concrete pouring 7. Masonry 8. Structural steel 9. Carpentry

10. Roofing 11. Plumbing and heating 12. Electrical installations 13. Painting 14. Miscellaneous structures 15. Road and rail sidings

Fahrenheit degrees

-10 to 0 None (with exceptions)

20 20

0 to 10 10

10 to 35 10

-20 40

-20 -30 to -20

32 32 32

xvii. Conclusions. Low temperatures impose serious restrictions .upon nearly all construction operations. Table 3 presents estimates of the low temperature limits for economic operations as normally practiced by United States establishments. At lower temper­atures operations can only be considered economic if they can be justified on the basis of expediency.

For many construction operations 32F is a signifi­cant critical temperature. At temperatures above 32F only a few minor operational efficiency limitations occur. At lower temperatures many problems arise which result either in a reduction in efficiency or in an increase in operating costs. Most operations are reasonably satisfactory, however, at 10F, provided minor changes are made in equipment and practices, and providing there exists very little wind and no precipitation. At temperatures lower than 10F very many operational problems arise. Interruptions in some types of work, become inevitable. Costs increase greatly. It becomes necessary to provide shelter and heat for much of the work if delayed completion or inferior workmanship is to be avoided. In some instances sheltering and heating have been found to be practical. Under such conditions it would be possible for construction to proceed exposed to the minimum temperatures which occur upon the earth's surface.

2. Ground frost

Seasonal ground frost need not limit construction operations seriously if, in the timing of operations, the seasonal conditions of the soil are taken into con­sideration. Also structural design need not ordinarily be changed to adapt to seasonal ground frost. All that is necessary is that the foundations of structures be based upon levels which lie below alternate occurrences of freezing and thawing.

In areas of permafrost, however, the problem of of frost is one which must be met throughout the year, and construction problems cannot always be solved by basing the foundations of structures below the level of thaw. The disturbing element is the penetration of the permafrost by heat which is generated within the structure. The existence of permafrost affects excavation, pile driving, foundation construction, and structural design. A discussion of these effects follows.

i. Excavation. Frozen soil can be excavated only with considerable difficulty and at a marked increase in cost. Overall costs of excavating permafrost can be as much as three times as great as the cost of excavating un­frozen soil. In its most severe condition the problem of excavating frozen soil is quite comparable with

MAY 1957 j. W. WATERS 45

that of excavating solid concrete. Excavation of frozen ground may require blasting, the use of pneumatic paving breakers, or thawing with water or steam. The cold water method used by mining companies in Alaskan placer mining operations is generally more economical and produces more uniform thawing action. For small localized areas, however, steam is faster and equally effective. Steam should be used during winter since use of water may cause severe icing conditions as it flows toward the natural drainage. If it is more important to reduce cost than to save time, excavation can proceed without forced thawing by exposure to warm summer air. Each level is premitted to thaw before stripping is begun. Explosives are sometimes used to expedite the job. It is standard practice to thaw permafrost to a depth of 40 to 60 ft under heavy foundations [34].

The excavation of thawed permafrost also presents unusual engineering problems. In order to prevent earth slides and ground water flooding of excavations, the surrounding embankment can be sealed by re­frigeration. A system of pipes set vertically in holes drilled below the depth of the foundation can be equipped with a refrigerant to maintain a temper­ature of OF during construction [13], The entire freezing process requires from 40 to 60 days [42].

In areas where trees exist, clearing can be under­taken by bulldozers only when the surface ground is frozen. If the surface is thawed and soft, the bulldozers tend to tear out the trees by the roots, rather than to shear them off, thereby disturbing the equilibrium of the permafrost.

In nonpermafrost areas (in northern United States) January is considered to be the lowest cost winter month for excavation. Roads and tracks are frozen solid. The surface is smooth and traction is good. Frost has not yet penetrated sufficiently deep to interfere with operations. The spring breakup period is considered to be the time of highest cost. Roads and tracks disintegrate and equipment suffers [17].

ii. Pile driving. To facilitate pile driving in perma­frost areas, forced thawing must precede the actual driving of the piles. Steam and water jetting are the most satisfactory methods of thawing and can be used in most types of soil. After the hole has been properly thawed piles can be placed by the usual methods [ 45].

According to theory, structures resting on piling which is properly set into a bed of permafrost (twice the depth of the active layer into the bed of per­manently frozen ground) should attain stability comparable with that typical of construction upon unfrozen ground [15]. Not in all cases has this

occurred. Some attempts have been completely unsatisfactory. The piles, instead of remaining rigid, moved up or down even before any load had been impressed upon them. In one such instance the piling had to be abandoned. iii. Foundation construction. The actual operation of constructing a foundation on permafrost is not interfered with by the frozen condition of the soil. Forms can be erected and concrete can be poured in the same manner whether or not permafrost exists. It is the result of permafrost that imposes the limita­tions. Unless adequate steps are taken to change radically the design of the structure, failure can be expected as the result of differential settling. In many instances the changes which were considered to be adequate turned out not to be so. For example, a six-story structural steel building in Fairbanks, Alaska, has settled unevenly because part of the building rests on permafrost, and part does not. The building is now visibly out of plumb, and a street level plate glass window has had to be replaced several times within a period of less than two years. Plans to save the building call for a refrigeration sys­tem to be buried around the foundation.

Buildings of moderate size can be erected on piling by allowing an air space between the floor of the building and the ground, so as to prevent alterations in the permafrost level. It is recommended that foundations for large buildings, however, be laid on a gravel mat at least 3 ft thick. The gravel should be compacted in 6 in. layers, the first layer being com­pacted upon the tundra without removing the top soil or vegetation except for trees and bushes. The careful selection of a site is most important because of the very great differences in the behavior of soils of different texture. Well drained coarse grained soils seldom give rise to foundation instability. Poorly drained fine grained soils tend to be extremely unstable when thawed.

Small wooden structures up to 48 ft in width do not need foundations deeper than approximately 3 to 6 ft, unless unusually heavy loads are involved. If ventilated subfloor areas are not used, the walls must be protected by an earth embankment and snow must be cleared away, especially in the first part of winter [ 44].

In marginal areas of permafrost it must be decided whether the frozen soil of a site will be eliminated or maintained for construction purposes. Consequently permafrost has been classified both as stable and unstable from the engineers' point of view. The latter type is thawed before construction, particularly if buildings are large. The criteria of permafrost stability are considered to be [12]:

46 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

1. Temperatures of 32F or less and the absence of ground water movement

2. A permafrost layer at least 80 ft deep, and a temperature which does not exceed 30F at the 32 ft level

3. A permafrost layer 65 ft deep, and a temper­ature which does not exceed 30F at a depth of 20ft

4. A stable regime 5. Ability to regenerate itself and to resist changes

in external conditions

iv. Structural design. Considerable success has been met by designing very heavy structures, such as electric power plants, to rest directly on the ground without utilizing an air space. Steam thawing to a depth of 30 to 50ft is first necessary. Nonfrost acting fill is compacted upon the surface. A very heavily reinforced concrete mat of about 4 ft thickness forms the base, so that if heaving or settling occurs, the entire foundation tends to move as a unit.

Masonry is generally considered to be unsatisfactory upon permafrost because it tends to be less rigid than other types of structures when exposed to differential heaving or settling [33, 43].

Some miscellaneous problems involving permafrost merit special consideration. For example, sewer sys­tems require special design principles in permafrost regions. Sewers must not be laid in or near the center of the street, because consolidation of the roadbed under traffic during spring thaw adversely affects sewer alignment. Sewers must not be laid directly on permafrost without adequate insulation, or in frost­susceptible soil. The pipe should be at least 8 in. wide to avoid closure by frost accumulations. One authority recommends that all pipes should consist of wooden staves to resist permanent deformation or breakage [31]. Differential settling or heaving on permafrost can interfere seriously with the performance of tanks and filters, the proper functioning of which is con­tingent upon precise alignment along a hydraulic grade line [41]. At the present time, under permafrost conditions, construction and operation costs of sewage facilities commonly used in continental United States are so high that such facilities are not economically feasible for most inhabitants of the arctic [3].

The disposal of garbage imposes unusual problems in permafrost areas both because of the difficulty of burial, and because filth-borne diseases are not reduced by the low temperature conditions. About one foot of earth cover is needed to bury garbage effectively. On permafrost the soil would not always be workable and it is doubtful if decomposition would take place. Consequently bulk or concentrated wastes must be

reduced to a stable noninfectious condition prior to ultimate disposal, or they must be adequately re­moved from the area beyond the flight range of flies and other insects. Of the various methods of garbage disposal, incineration appears to be the most satisfactory [4].

Considerable evidence exists that permafrost should be considered as a major factor placing limitations upon the construction industry. Thus the climatic condition which is responsible for permafrost, an annual average temperature of 32F, should be con­sidered critical. No entirely satisfactory method of preventing foundation failure has yet been developed [37]. Although it is estimated by some authorities that most industrial types of construction could be attempted upon permafrost, little experience exists with large structures. It cannot be overemphasized that as a result of permafrost, construction methods and structural design must be radically altered to facilitate any degree of satisfaction in use. The con­cept has even been advanced that permafrost should be recognized as comprising a distinct region in which construction methods and the means used for reducing structural deformation are entirely different from those which exist in areas that lack permafrost [23]. Thus for practical purposes the "Engineer's Arctic" becomes defined as that region north of the lowest latitude at which permafrost may be expected to exist [19, 25].

3. High temperature

High atmospheric temperature conditions have received attention in this study only since they occur as warm season characteristics of nontropical climates. Consequently this treatment of the effect of high temperature upon construction operations will appear inadequate if judged in terms of tropical operating experience. However, due to the occurrence of extremely high temperatures in high latitude con­tinental locations, the degree of heat experienced exceeds that of most tropical areas for periods of relatively short duration.

The overall efficiency of construction operations will tend to decline from the maximum as the temper­ature increases from the optimum range of 50 to 75F. The rate of efficiency decline does not appear to be great, however, and there do not appear to exist any overall critical temperature levels beyond which operational efficiency is significantly lowered. The decline in efficiency which does occur seems to pertain in most instances to worker activity rather than to equipment or machinery behavior.

Since much construction involves outdoor work,

MAY 1957 J. W. WATERS 47

nearly all phases of construction operations are affected by the decline in worker efficiency which occurs as temperature rises; however, this is not a function of temperature alone, but a combination of atmospheric conditions which combine to create dis­comfort. Thus generalizations cannot be made in terms of any specific temperature level. It is pertinent also to consider wind, sunlight, and humidity. Con­struction work is possible at considerably higher temperatures if such occurrences are combined with moderate winds, shelter from sunlight and low relative humidity. Unless it is very dry, generally very little work can be undertaken at temperatures greater than lOOF. At temperatures up to, and considerably beyond that level, mechanical equipment continues to operate satisfactorily. Thus, although operations are possible at temperatures above lOOF, because of reduced working efficiency and increased susceptibility to error and accident, it can be con­cluded that construction operations are not economic at temperatures exceeding lOOF.

4. Rainfall

Occurrences of rainfall constitute departures from the optimum for construction activity. Such occur­rences do not interfere with all types of construction operations equally. Also, the effect of different types of rainfall are not similar for all types of operations. A discussion of these distinctions follows. i. Surveying. Surveying is greatly impeded by rain­fall. The efficiency of the surveyor is appreciably reduced even in light rainfall; in heavy rainfall work becomes impossible for practical purposes. Also, rain can damage surveying instruments. ii. Materials stockpiling. If rainfall detrimentally af­fects stockpiled material, shelter must be provided. For example, bricks and cement must be stored out of the rain. In order that the moisture content of sand and gravel be kept constant, special roofs of timber, sheet metal, or canvas are provided. Drainage is a major item in storing sand, particularly since a constant moisture content offers the simplest means of maintaining proper control over the concrete mix [2]. Generally, however, rainfall does not impose serious problems in the stockpiling of materials since shelter can be easily provided. iii. Excavation. The effect of rain upon excavation can range all the way from a moderate reduction in efficiency to complete obstruction of work. Of all the construction operations, excavation appears to be the most seriously affected by rain. Earth moving equip­ment can become bogged in wet mud. Tractors and tired vehicles lose traction. If sufficient rain falls,

TABLE 4. Limitations imposed upon excavation equipment by weather [2]

Types of equipment

Tractor-drawn scraper Trucks Rubber-tired tractors and

wagons (truck-wagons) Crawler tractors and wagons Belt conveyers

Aerial tramways Drag lines

Type of weather interference

Unsuited in rain or mud Poor going in rain or mud Poor going in rain or mud

Rain and mud reduce production Unless covered, rain will reduce

output seriously when han­dling earth or clay

High winds hamper operations Storms, floods, and ice hamper

the operations of the floating dredges. Can operate and place fill through ordinary rains and changes in water level.

work must cease until the ground dries. The amount and frequency of rainfall can affect directly the selection of types of equipment; tracked vehicles are preferable to tired vehicles in mud [2]. Table 4 presents a listing of the weather factors (in particular rainfall) which impose limitations upon the operations of various types of excavation equipment.

The following is a listing of the steps considered to be necessary to keep heavy equipment operating with reasonable efficiency during wet weather [32].

1. Keep haul roads smooth. Fill in water holes. Assure good drainage.

2. Smooth up the fill, cut, borrow pit, or haul road at the end of a working shift.

3. Keep cuts low at sides and high at center for drainage.

4. Keep fill compacted by spreading loads thinly. 5. In hilly country cut ditches to drain cuts. 6. Use bulldozers to skim off mud. 7. Cover slippery haul road with sand or cinders,

and scrape the wet layer off the surface. Reduce road grades.

8. i\1 uck out soft spots by bulldozing and filling. 9. Adjust tire pressures low for soft and spongy

mud, and high for cutting through shallow mud to a firm base.

iv. Pile driving. Pile driving is not detrimentally affected by rainfall. It is even possible that con­siderable rain could ease the driving of piles by softening the ground. v. Concrete form construction. The construction of concrete forms is interfered with by rainfall only if it becomes impossible for workers to continue work. The task itself is not vulnerable to rain. vi. Concrete pouring. Ordinarily most concrete units can be poured during a rainfall. Walls and thin sections are not very vulnerable, and are protected

48 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

readily. The pouring of slabs, however, cannot be continued in the rain. Either shelter must be provided or work must cease, since a fall of rain can ruin a freshly poured concrete slab, deck, or pavement. It is possible at increased cost to protect slabs during rain by covering the freshly poured concrete with portable panels. Concrete mixing operations must be protected if occurrences of rain are frequent.

vii. Masonry. Generally masonry work cannot be continued if it is exposed to rainfall. Either shelter must be provided or work must cease. Partly com­pleted masonry walls that are not protected by roofs or copings can be covered with boards weighted down by bricks [6].

viii. Structural steel work. Rainfall seriously interferes with structural steel work, although it need not completely preclude operations. Both riveting and welding are interfered with by heavy rain. Shelter becomes necessary if rain is frequent. Of the two, welding is the more sensitive.

ix. Carpentry. Generally carpentry' work cannot be exposed to rainfall unless the rain is very light.

x. Roofing. Most roofing work cannot be continued in the rain. For built-up roofing work it is necessary that the weather be dry for at least two or three days.

xi. Plumbing, heating and electrical installation. Plumb­ing, heating, and electrical installation involve work in partly, or nearly completed structures. Since work is sheltered it can proceed independent of weather conditions.

xii. Painting. It is not possible to paint in the rain. Shelter must be provided or work must cease.

xiii. Construction of miscellaneous structures. The ef­fect of rainfall upon the construction of miscellaneous structures depends upon the nature of the operations involved. These generally consist of carpentry, masonry, concreting or steel work. Each is discussed separately above.

xiv. Road and rail siding construction. Much of the work involved in the construction of roads, parking areas, and railway sidings consists of excavation or concreting. The effect of rainfall upon each is dis­cussed separately above.

xv. Labor. The effect of rainfall upon workers varies, dependent upon the rate of fall, and the condition of wind and temperature. If adequate rainproof clothing is provided, if the temperature is higher than SOF, if it is not windy, and if it is not raining heavily, outdoor work can be continued indefinitely. Lack of adequate clothing, low temperature, strong winds, and heavy rainfall can each, individually or in combination, pre­clude outdoor work. For example, no matter how well

workers are clothed it is impossible to keep dry for more than an hour or so if exposed to rain and strong winds. At Ketchikan, Alaska (average annual pre­cipitation approximately 150 in.), construction oper­ations have been curtailed by 20 per cent because of rainfall. Workers are more likely to continue working in the rain if they are used to it. Under favorable conditions (temperature above SOF, no wind) it is estimated that work efficiency declines approximately 10 per cent due to rainfall.

5. Snowfall

Occurrences of snowfall constitute departures from the optimum for construction activities. The problems which are imposed upon the various construction operations are discussed separately below.

i. Surveying. Snowfall places limitations upon survey­ing in several ways: snow can damage a surveyor's instruments; heavy snowfall can reduce visibility, thereby decreasing accuracy; snowfall can obliterate survey markers. Snow ordinarily is associated with temperatures of less than 32F so it is combined with the effects of low temperature on the surveyor, pre­viously presented. Snow on the ground can make sur­veying difficult; falling snow can make it impossible.

ii. Materials stockpiling. Some materials cannot be stockpiled where they will become exposed to snow and shelter must be provided. Materials that do not deteriorate when exposed to rainfall are usually not affected by snow. Tarpaulins provide adequate pro­tection in most instances.

iii. Excavation. A moderate amount of snow on the ground does not interfere with excavation operations. Deep snow need only be removed by ploughs, snow loaders and trucks, or by snow blowers. Excavation equipment parts and tools that are normally piled on the ground need to be sheltered to prevent their being covered by snow [17].

iv. Pile driving. To facilitate pile driving snow can be cleared. Pile driving operations are not hindered by snowfall.

v. Concrete form construction. Snowfall can interfere with the construction of concrete forms, but not to a sufficient degree to make work impossible. Snow that drifts in and around the forms must be removed. Hand shoveling becomes necessary to accomplish this work.

vi. Concrete pouring. Largely because of the low temperature which is associated with snowfall, con­creting must be considered impractical if exposed to snowfall. Work units can, if necessary, be sheltered from snow; winter concreting is likely to be sheltered

MAY 1957 ]. W. WATERS 49

from low temperatures as well as snowfall. For example, one instance has already been cited of an industrial building constructed during the winter beneath a temporary roof that was raised by jacks as work progressed upward. The roof not only enclosed the work areas, making heating possible, but also provided shelter from snow [14].

vii. Masonry. Masonry work cannot be continued when exposed to snowfall. Shelter must be provided. Brick must be covered to avoid the danger of freezing after being wetted by snow.

viii. Structural steel work. Structural steel work is interfered with by snowfall. Work becomes hazardous as platforms and steel become icy and slippery. Exposure to low temperature and moisture from snow lowers the quality of welding.

ix. Carpentry. Generally carpentry is not continued when exposed to snowfall. Tools and wood become wet, work becomes difficult and efficiency low.

x. Roofing. It is not possible to apply built-up roofing if it is snowing both because of the low temperature and the snow. A moderate fall of snow will interfere with work on other types of roofing materials as well.

xi. Road and rail siding construction. Snowfall can make the construction of roads, parking areas, and railway sidings impractical. It is possible, however, to construct temporary roads by compacting snow with graders and bulldozers.

xii. Snowloads. Snow loading must be taken into consideration in the construction of both temporary and permanent roofs. It has been stated that existing values for snowloads are unsatisfactory because they are based upon inadequate data. The minimum basic live snowload requirements should be based on a maximum accumulation of snow in a given area. This accumulation may be converted by using a factor 0.5 lb per sq ft per in. of snow depth, based upon the assumption that the average specific gravity of snow after falling is 0.1 [22]. Flat roofs are subject to greater accumulations of snow and ice than sloped roofs. It has been calculated that the maximum snow load should be expected to be approximately twice the weight of the snow pack which would be equaled

TABLE 5 [46]. Minimum uniformly distributed design vertical live roof loads

(For fiat roofs or roofs having a rise of 3 in. per ft or less)

lb per sq ft

Southern States 20 Central States 25 Northern States 30 Great Lakes, New England and Mountain Area 40 Flat roofs used for sun decks or promenades 60

or exceeded once in 10 yr. A customary safety factor of 2.5 is applied to allow for considerations such as deterioration of structural members or fastenings during the life of the structure. Design vertical live loads for flat roofs are given in table 5.

The above data indicate that snow loading in the areas of heaviest snowfall does not require as high a standard of design strength as do loads involving people (i.e., promenade or sun deck). Sloping roofs require even less design strength (table 6).

TABLE 6 [46]. Minimum uniformly distributed design vertical live roof loads

lb per sq ft of hori7.ontal projection

3 in 12 12 in 12 Slope: or less 6 in 12 9 in 12 or more

Southern.States 20 15 12 10 Central States 25 20 15 10 Northern States 30 25 17 10 Great Lakes, New England,

and Mountain areas 40 30 20 10

6. Sleet and ice

A heavy icing condition created by a sleet or ice storm or by freezing of fog on all exposed surfaces can make construction work extremely difficult, if not impossible, especially for concrete form construc­tion, masonry, structural steel work, carpentry, and roofing. Work must cease until the ice melts, or until it is cleared. Generally workers will not continue working during a sleet storm. Sleet and ice are considered to be even more of a limitation to outdoor work than either rain or snow. If shelter is provided, work can continue without interruption.

7. Humidity

High atmospheric humidity conditions impose limitations upon certain construction operations. Humidity has an effect upon the behavior of all compressed air equipment at subfreezing temperatures. Moisture condenses and forms ice on the exhaust of the compressed air tools, choking off the exhaust and thus causing a shutdown. If the humidity is very low the tools might work satisfactorily at temperatures as low as - 20F. If the humidity is high tools can become frozen up at 10 or even 20F. The interference caused by such interruptions can be serious because of the large variety of power tools that are best operated by compressed air units; no really good substitute for this type of power exists. If alcohol is vaporized into the air lines, the tools can be kept operating at low temperatures. Thus it appears that this problem can be minimized or eliminated.

50 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

Other effects of high humidity conditions upon construction operations exist. Painting is not satis­factory in very humid weather and a longer period of time is required for the paint to dry. In a very wet climate where prolonged periods of very high humidity exist, problems arise in the handling of cement. Normally bulk cement is handled in special type box or hopper railway cars, and in conveyers, pumps and pipelines. High humidity precludes such handling techniques. Cement must be handled in paper bags as is the practice in Panama [2]. Even in drier areas it is important that if an airstream is used for trans­porting cement the air must be as dry as possible. For this reason an aftercooler and moisture trap are frequently employed on cement pumping installations [2].

Humidity is a factor in the comfort of workers. Lower temperatures are more tolerable if the relative humidity is also low. The same is true of high tem­perature conditions. Work at temperatures exceeding 100F is possible only if the air is very dry. If not, work efficiency at temperatures exceeding 85F de­clines considerably.

8. Wind

The degree of interference which can be imposed by wind upon the construction of industrial establish­ments can extend to a complete stoppage of opera­tions. As the wind speed increases, operational conditions depart from the optimum, and efficiency declines. Critical wind speeds appear to exist beyond which significantly lower degrees of operational efficiency exist.

Winds up to 15 mph do not impose serious limita­tions upon operations. A continuing wind speed of 15 mph does, however, tend to have a debilitating effect upon workers resulting in a decline in work efficiency. An average wind speed of 30 mph is considered to be the maximum limit for most exposed outdoor work particularly because an average wind speed of 30 mph will involve gusts of 40 to 60 mph. Beyond this limit, outdoor work efficiency declines sufficiently so that continued operations cannot usually be justified.

Wind is a critical factor in association with other weather conditions, such as low temperature, rainfall, and snowfall. For example, at OF a wind speed of 20 mph results in lower work efficiency than a condi­tion of no wind and -SOF. Another example pertains to the formation of ice on a sewage treatment filter unit. Ice forms at 20F in winds of 25 to 35 mph, but not at - 24F if the wind speed is less than 5 mph [ 41 ].

Some types of operations are more vulnerable to wind interference than others. For example, structural

steel work tends to be highly susceptible to wind interference. Finished structures must be designed to withstand the maximum wind velocities to which they are likely to be exposed [41] although engineers do not ordinarily design for such exceptionally high winds as characterize tornadoes. Partly finished structures cannot be expected to attain such standards. Thus, work becomes dangerous when exposed to wind speeds of 20 to 25 mph. Safety cannot be assured even with advance planning if wind speeds of 30 to 40 mph occur. Partly completed structures can be shifted or blown down. Cranes become inoperable, and can be blown over if not properly anchored. Special structures like smoke stacks that have not attained their finished strength can be damaged or blown over.

Site choice is a critical factor when wind exposure is considered. Relatively minor features of topography or man-made structures can create marked differences in the degree of exposure to wind [41].

Several types of construction operations are partic­ularly susceptible to wind interference. High winds tend to obscure visibility, largely because of debris being carried, and generally jeopardize accuracy in surveying. Long conveyer belts and aerial tramways used for excavation become inoperable in moderately strong winds [2]. Roofing work cannot be continued if it is very windy. Also certain roofing materials are more susceptible to wind damage than others; slate, tile, asphalt-prepared rolled roofing, shingles, and metal roofings are quite vulnerable to damage in wind storms.

The present knowledge of wind pressure distribution on buildings of various shapes and outlines is not adequate to permit drafting satisfactory general rules that can be advocated for building design. Wide variations in the wind load requirements of building codes exist throughout this country partly because of regional differences in wind velocities, and partly because of the above stated lack of adequate data upon which rules can be based. One overall recom­mendation calls for design to sustain a uniformly distributed force of 20 lb per sq ft for the first 300 ft above ground level, increased above that level by 2.5 lb per sq ft for each additional 100 ft in height. For buildings whose width is large in proportion to their height, wind stresses are not as important a factor. The stiffening effect of the panel walls and partitions, and the rigidity of the joints between the girders and columns may be sufficient to provide satisfactory resistance to wind forces. However, criteria differ. For example, some codes state that buildings less than 150 ft high whose least width is greater than one-fourth the height need have no

MAY 1957 ]. W. WATERS 51

special provision for wind. Others place the limit of height at 100ft and require that the least width be one­third the height in order that the effect of wind may be disregarded. Nevertheless, special wind force specifications must be formulated locally for areas that are definitely known to be subject to hurricanes and tornadoes.

9. Sunlight

Sunlight can be considered a factor of major significance as a result of its effect upon construction operations. Without sunlight, artificial lighting of work areas must be provided, or work must cease. This is particularly pertinent for work in the arctic, since the seasonal variation in the daily period of sunlight is great. Winter work requires artificial lighting. Different operations are affected differently both because of the need for light and the size of the area of operations which require light (e.g., masonry vs. excavation). Summer sunlight is one of the climatic factors which tends to limit arctic construc­tion to summer months.

In very few other instances is sunlight a factor. One of these involves surveying. Fine surveying must be done on cloudy days, or during the period between daylight and sunrise so as to avoid the effect of the hot sun on the metallic parts of 'instruments which tends to throw sizes and shapes out of proportion by differential expansion.

10. Other weather elements

None of the other weather elements such as pressure and lightning or combinations of elements have a significant effect upon the efficiency of construction operations. Variations in other elements are not accompanied by appreciable variations in the oper­ating efficiency of the construction industry.

11. Conclusions

Generally, when construction in high latitude areas is called for, it is scheduled so that as much outdoor work as possible is completed before winter sets in. Winter work is either continued under heated shelters, or inside structures. Other operations cease. Con­tractors estimate that 90 to 95 per cent of their construction work in Alaska is undertaken during the summer. The remaining 5 or 10 per cent either consists of inside work, or it consists of urgent projects for which cost limitations do not exist. Costs of winter construction work in Alaska have been found to be 150 to 250 per cent those of summer work; some operations cost four or five times as much. It can be concluded, therefore, that winter construction~ in

northern areas is generally impractical either in terms of cost or quality of product.

There exists a condition in permafrost areas indirectly created by weather conditions which im­poses a considerable degree of efficiency limitation upon worker activities. Conventional methods for drainage of areas adjacent to construction sites are impractical and almost impossible in the permafrost regions. Breeding in these poorly drained areas are hordes of disease-bearing sucking and biting insects, such as mosquitoes, black flies, horse flies, deerflies, blowflies, and other flies and midges (150 species have been recognized). The degree of interference which these pests can impose upon work can be considerable.

In areas of low temperature and permafrost steel­framed, sheathed buildings are the most readily erected, but reinforced concrete structures are con­sidered to be the most satisfactory. Masonry struc­tures are unsatisfactory.

It appears that it would be physically possible to construct any size of industrial establishment under any climatic condition providing cost limitations were not imposed. Large projects have definite advantages over small ones because costs of operating in such areas do not increase in proportion to the size of the project.

Economic operations are considered to be possible in any area of the world since by a careful scheduling of activities, operations can be timed so that they are undertaken when weather conditions are most favorable. Cost increases resulting from summer activities are created by attempts to rush a job to completion; from winter activities they are created by the provisions made necessary for protection of work and structures.

Low temperature and permafrost appear to impose the greatest degree of limitation upon operations. Precipitation possibly ranks next, with sleet, ice, and snow imposing greater restrictions than rain. Wind is less important, not because it is incapable of interfer­ing seriously with operations, but because it is less likely to occur in a condition detrimental to con­struction. The other climatic elements have minor significance by comparison.

REFERENCES

1. Abeles, P. W., 1951: How much prestress? Engineering News­Record, 147, no. 3, 33-34.

2. Ackerman, A.]. and C. H. Locker, 1940: Construction Plan­ning and Plant. New York, McGraw-Hill, 381 pp.

3. Alter, Amos]., 1950: Water supply problems in low tem­perature areas. Science in Alaska. Selected Papers of the Alaskan Science Conference of the National Academy of Sciences. Washington, National Research Council. Henry· B. Collins, ed. June 1952, 219-239.

52 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

4. --, 1951: Garbage Disposal in Difficult Areas. National Research Council, Div. Mat., Sci. Committee on Sanitary Engineering and Environment.

5. American Concrete Institute, 1949: Recommended practice for winter concreting methods. Proc. A mer. Concrete Inst. Current Reviews, 45, 1-18.

6. Bach, Carl H., 1946: Protection of masonry in cold weather. Brick and Clay Record, 109, no. 4, p. 30.

7. Beal, R. W., 1951: Designing construction equipment for Arctic service. Abstract, Machine Design, 23, no. 2, 204-206.

8. --, 1950: Winterizing of construction equipment. A uta­motive Industries, 103, no. 12, 120-122.

9. Belskii, V. I. and V. I. Alatyrtsev, 1943: The construction of a 140 meter smokestack above the Arctic Circle. Stroitelnaia Promyshlennost, 21, no. 9, 3-5. (SIPRE Re­port 12, Vol. 3, p. 130, S.I.P. U3009).

10. Bijlaard, P. P., 1951: Brittle fractures in welded bridges. Engineering News-Record, 146, no. 17, p. 46.

11. Concrete, 1943: Winter construction methods followed at bomber base, 51, no. 10, 2-5.

12. Dementiev, A. 1., 1947: Classification of permafrost from the engineering point of view. Academy of Sciences, Merz­lotovedenie, 2, no. 1, 55-57 (SIPRE Report 12, Vol. 2, p. 19, S.I.P. U813).

13. Dorman, I. A., 1952: Application of refrigeration for ground freezing. Kholodilnaja Tekhnika, 29, no. 2, 2-5 (SIPRE Report 12, Vol. 3, p. 219, S.I.P. U3516).

14. Engineering News-Record, 1936: Winter concreting. 116, 696. 15. Engineering News-Record, 1947: A test study of foundation

design for permafrost conditions. 139, 404-407. 16. Espenschade, P. W., R. C. Navarin and W. W. Van Neuss,

1952: Six musts for subzero winterization. Soc. Automotive Engineers J., 60, no. 5, 26-29.

17. Friedman, E. A., 1953: Problems encountered in winter stripping of open pit mines in Northern Minnesota. Minnesota Engineer, 4, no. 3, 11-13.

18. Gillett, H. W., 1949: Impact Resistance and Tensile Proper­ties of metals at sub-atmospheric temperatures. Project No. 13 of the joint A.S.M.E. and A.S.T.M. Research Com­mittee on Effect of Temperatures on the Properties of Metals. Philadelphia, 112 pp.

19. Hoge, W. M., 1947: Construction in the Arctic. Lecture at the Army War College (Abstract in SIPRE Report 12, Vol. 2, p. 278, S.I.P. U2078).

20. Hubbard, Lee D., 1945: Construction methods at Juneau. Pacific Builder and Engineer, 51, no. 4, 56-57.

21. Huntington, Whitney C., 1941: Building Construction. New York, John Wiley and Sons, 674 pp.

22. Ketchum, Verne and James H. Cissel, 1949: Snow loads on buildings. Engineering News-Record, 143, 76-77.

23. Lukashev, K. 1., 1938: Permafrost region as a separate topo­graphical and construction region. Izdanie Leningradskogo Gosudarstvennogo Univ., 187 pp. (SIPRE Report 12, Vol. 2, p. 85, S.I.P. U1144).

24. Marzhetskii, V., 1940: Mechanical Transportation in the Arctic. Moscow, 103 pp. (SIPRE Report 12, Vol. 2, p. 124, Bibliography Abstract No. S.I.P. U1336).

25. Maslov, N. N., 1941: Problems of construction on perma­frost. Inzhenernaia Geol., Stroiizdatnarkomstroia, Lenin­grad-Moscow, pp. 410-419 (SIPRE Report 12, Vol. 2, p. 270, S.I.P. U2043).

26. Merritt, Alan, 1944: Construction methods in sub-arctic. Pacific Builder and Engineer, SO, no. 2, 33-34.

27. Mitchell, Gordon and R. B. Young, 1950: Winter concreting can be economical. Civil Engineering, 20, 511-515.

28. Moriarty, C., 1945: So you think you have transportation problems. Pacific Builder and Engineer, 51, no. 5, 52-55.

29. Pacific Builder and Engineer, 1944: Excavation at 70 degrees below zero. 50, no. 1, 36-38.

30. Potter, A. R., 1952: Sub-zero weather complicates well­servicing operations. World Petroleum, 23, no. 5, 88-89.

31. Public Works, 1950: Designing sewers for the sub-arctic. 81, p. 44.

32. Roads and Engineering Construction, 1951: How to keep heavy equipment operating efficiently in wet weather. 89, no.4,p.117.

33. Saltykov, N. 1., 1946: The building foundations in lakutsk. Akad. Nauk SSSR, Trudy instituta merzlotovedeniia im. V.A. Obrucheva, I, 102-136 (SIPRE Report 12, Vol. 2, p. 223, S.I.P. U1816).

34. Seeman, L. E., 1951: How Alaska contractors fight perma­frost. Pacific Builder and Engineer, 57, no. 7, 54-56.

35. Sellers, E. S., 1951: The selection of lubricants for use at low temperatures. Polar Record, 6, no. 42, 237-244.

36. Shishkin, A. A., 1937: On the actual strength of masonry erected during winter. Stroitel, 10, no. 20, 7-19 (SIPRE Report 12, Vol. 3, p. 179, S.I.P. U3298).

37. Spofford, C. M., 1949: Low temperatures in inaccessible arctic inflate construction costs. Civil Engineering, 19, 12-15.

38. Stout, Robert D., 1950: The properties of weldments at low temperature. Symposium of Effect of Low Temperature on the Properties of Materials, A.S.T.M., Spec. Tech. Pub. No. 78, pp. 51-59.

39. Sweeney, E. F., 1953: Evaluation of brittle fracture research. Welding J., 32, no. 1, 1-s-13-s.

40. Teed, P. L., 1950: Properties of Metallic Materials at Low Temperatures. Chapman and Hall, 222 pp.

41. Thomas, Harold Allen Jr., 1950: Investigation of Sewage Treatment in Low Temperature Areas. National Research Council, Committee on Sanitary Engineering and Environ­ment, 1 p.

42. Trupak, N. G., 1948: Frozen ground in the building industry. Stroiizdat, Moscow, 324 pp. (SIPRE Report 12, Vol. 2, p. 70, S.I.P. U1063).

43. Tsytovich, N. A., 1940: The peculiarities of construction on permafrost in the Yakutsk area. Akad. Nauk SSSR, Trudy Komiteta po vechnoi merzlote, 9, 27-37 (SIPRE Report 12, Vol. 1, p. 142, S.I.P. U766).

44. Tumel, V. F., 1946: The behavior of permafrost under foun­dations of wooden houses in the northern regions of the permafrost zone. Trudy Inst. Merzlotovediia im. V.A. Obrucheva, 1, 5-26 (SIPRE Report 12, Vol. 2, p. 29, S.I.P. U862).

45. U. S. Government, 1950: Construction of Runways, Roads, and Buildings on Permanently Frozen Ground. Dept. of the Army Tech. Bull. TB5-255-3, Washington, D. C., 87 pp.

46. U. S. Government, 1952: Snow Load Studies. Housing Res. Paper No. 19, Housing and Home Finance Agency, Div. Housing Research, Washington, D. C., 16 pp.

47. Volovelskii, A. and V. Krasnogorskii, 1938: Laying stone foundations by means of freezing and subsequent thawing by steam. Stroitelnaia promyshelennost, 16, no. 3, 54-55 (SIPRE Report 12, Vol. 1, p. 139, S.I.P. U752).

INDUSTRIAL OPERATIONS UNDER EXTREMES OF WEATHER

by

]. A. Russell; W. W. Hay;]. W. Waters; H. E. Hudson, Jr.;]. Abu-Lughod, W. ]. Roberts, and]. B. Stall;

A. W. Booth; and E. F. Taylor. Edited by ]. A. Russell.

IV. WEATHER LIMITATIONS TO ELECTRIC POWER UTILITY OPERATIONS

By]. W. WATERS

(Original manuscript received 27 March 1956; revised manuscript received 7 June 1956)

ABSTRACT

The effects of extremes of weather on steam, hydro-, and diesel-electric power generation and on power distribution are considered. It is concluded that in areas subject to extremely low temperatures and perma­frost these two conditions impose the most serious difficulties to the electric utility industry, but that in other regions sleet, wind, lightning, and snow are more serious.

An attempt is made to determine the weather conditions which impose specific and definable degrees of efficiency limitation upon the operations of electric power utilities. The material presented is based upon library materials and upon consultation with Con­sumers Power Company of Jackson, Michigan; Northern States Power Company of Minneapolis, Minnesota; and Otter Tail Power Company of Fergus Falls, Minnesota. Operators were questioned con­cerning their experiences with weather extremes, and estimates of what their operating efficiencies would probably be if their utilities became exposed to even more severe conditions, ranging all the way to the most extreme conditions which have occurred upon the earth's surface.

Electric power utilities differ markedly in terms of buildings, special structures, equipment, and opera­tions depending principally upon the source and the method of generating their power. Treatment, in terms of weather, of all types of power generating units taken together would be unproductive of meaningful generalizations because it cannot be assumed that the different units would behave similarly upon exposure to extreme conditions. Con­sequently for the purposes of this work it has be­come necessary to recognize the following major divisions:

53

Power production

a. Steam plant 1) Coal storage handling and preparation 2) Water intake and circulatory system 3) Boilers 4) Turbogenerators

b. Hydro plant 1) Water storage and intake system 2) Turbines and generators

c. Diesel plant 1) Diesel fuel system 2) Diesel engines

Power plant electrical system (from generator terminals to transmission line terminals, including bus system, circuit breakers, transformers, etc.)

Power distribution

a. Substations b. Transmission and distribution lines

Not all the effects of weather upon electric power utility operations can be stated in terms of single elements or even specific combinations of elements. For example, quite a variety of weather circumstances can create seasonal variations in the power load

54 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

demand; peak loads can occur during either winter or summer depending upon their severity. An in­creased use of air conditioning equipment is creating a summer seasonal load peak in the southern states. Variations in loads are desirable, providing they are not too great, because they provide time for major equipment overhaul. Daily load variations permit only minor types of maintenance. Consequently in an area having a relatively constant power load additional capacity would have to be installed to provide for regular major overhaul maintenance. The inter­connection of power systems can reduce or eliminate the need for such extra capacity, since peak loads for different areas seldom coincide [13].

Some seemingly very minor nonweather factors have a direct effect upon the behavior of equipment when it is exposed to extreme weather variations. Very little is known about the real effect upon equip­ment behavior of many of these minor factors. Consequently generalizations in terms of weather elements which ignore these minor factors or variables are less valid than would be possible had more infor­mation been available. For example, the following are structural variables which affect the incidence of weather limitation to operations of electrical distribu­tion systems [2]. Treatment of their influence upon power line behavior has not been presented because adequate information could not be obtained.

1. Grounded or ungrounded distribution system 2. Voltage 3. Conductor spacing 4. Conductor covering (quality, size, age) 5. Pole structure design 6. Strength of conductor (i.e., wire size) 7. Pole spacing 8. Material in braces, pins, etc. (i.e., steel or

wood) 9. Tree contact exposures

10. Miscellaneous object contact exposures

1. Low temperature

The temperature which is considered optimum for operations of electric power utilities pertains in most instances to worker efficiency. A temperature range from 40 to 75F appears to be optimum for worker efficiency depending upon the location of work (i.e., within a power plant, or outdoors). For a situation in which the optimum condition does not pertain to worker efficiency, the most desirable temperature condition is slightly above freezing. Steam plants which use a river or lake supply for their main con­densers desire as low a water temperature as possible (32F) to maximize the effectiveness of their con-

densers. This is not true for plants that utilize cooling towers. They use the river or lake water mainly for boiler makeup. For these plants a water temperature of 50 to 70F is most desirable since preheating for boiler use would be required if the water temperature were lower. Thus, although temperatures below 40F are not quite optimal for worker efficiency, it can be generalized that between 32 and 75F normal opera­tions are not hindered to a sufficient degree so that any changes in practice or equipment are necessary.

The low temperature problems which interfere most with electric power utility operations do not apply to all types of power systems equally. The freezing of water supplies, and of water intake systems (of both steam and hydro plants) seems to be the greatest single low temperature problem. Another problem of somewhat lesser importance is the freezing of coal, especially in railroad cars. For many plants which use lignite as fuel this becomes the foremost low temperature problem. Other less severe low tem­perature problems are the operation of mechanical equipment and the continuation of worker activity outdoors. It seems likely that although overall operations would not be possible with operating efficiencies and costs comparable to average United States establishments at temperatures lower than -50F, such operations would be possible beyond this limit providing cost and efficiency limitations are not taken into consideration.

Several critical temperature levels can be recognized, above and below which there appears to exist signifi­cantly different conditions for operation. The first of these critical temperatures is 32F. Above 32F, up to approximately 75F, temperature problems do not exist. The second critical temperature is approximately 15F. Certain low temperature problems frequently characterize the 15 to 32F temperature zone, in particular, sleet storms, but including freezing of coal, cooling tower difficulties, freezing of wet conveyor belts, etc. A third critical temperature is approxi­mately OF. At temperatures above OF outdoor operations are not seriously hampered by low temper­ature alone. Below OF serious problems begin to arise pertaining to outdoor activities. Thus the temperature zone of 0 to 15F is one which is relatively free from interference with operations, and one which is con­sidered, by some operators, to be ideal for all types of power utility work. The fourth critical temperature level appears to exist at approximately - 25F. At lower temperatures blizzards are not as likely to occur. Thus the temperature zone of 0 to - 25F is characterized by the prevalence of blizzards. and resulting serious operational interferences. At tem­peratures below - 25F low temperature induced

MAY 1957 J. W. WATERS 55

operational interferences gradually become greater until a final fifth critical level appears to exist at approximately -40 to -SOF. Below this level very serious operational problems are imposed upon all types of outdoor and some indoor operations. The following are operating conditions experienced at temperatures below OF. i. Power production-steam plants. Power plant build­ings are designed to facilitate continuous operations at the lowest temperatures that occur in the United States. Exposures to -40F do not restrict operations. It is estimated that by incorporating minor changes in design, such as improving the insulating quality of the walls, and by increasing the number and size of space heaters, temperatures of - 90F would not interfere with operations. Plenty of boiler heat exists within the plants so that more and larger space heaters could be readily installed. For low temperature exposures double walls of galvanized or aluminum sheet metal separated by an insulating material are satisfactory. Heaters must be provided at draft air intakes. Since, however, combustion air is preheated to 300 to 350F normal fluctuations of the atmospheric temperature do not impose problems.

A minor problem is encountered at some of the plants of one company. A marked pressure differential occurs between the air pressure inside a power plant building and atmospheric pressure during cold spells when ventilators and windows are closed. The differential is induced by the forced draft fan equip­ment; indoor air pressure is reduced. If windows or ventilators are opened to equalize the pressure, large quantities of cold air are sucked in. To prevent this air from cooling the plant, and to avoid the freezing of lines which pass nearby, radiators are installed at the vents. In some instances the air movement has been sufficiently great to freeze the exposed sides of these radiators (at - 20F).

There have been recent trends toward constructing steam plants in which part or almost all of the equip­ment is outdoors. Freedom from winter conditions seems to be the controlling factor in the design of such plants. All completely outdoor plants are located in the southern states and have only their control room enclosed [10]. Semioutdoor plants are located, however, in areas which experience extreme winter conditions. One such plant is exposed to extremes of below -40F and above 110F [12]. The turbo­generator for this plant is located on top of a roof platform which is straddled by an all weather service crane. All pipelines are enclosed. There is an extra boiler for heating the plant when equipment is not in use because peak load service is only required about 30 per cent of the time. The chief problem here seems

to be the protection of pipelines from freezing at low temperatures. The degree of exposure of equipment incorporated in such designs depends upon the weather; outdoor type of construction has not generally been utilized by companies which operate plants continuously in the northern part of the United States. Outdoor type of construction would probably be still less practical in areas which experience even more severe winter weather conditions. (1) Coal storage, handling, and preparation. Coal can freeze in railroad cars depending upon the moisture condition in the loaded cars, the rank of coal, and the temperature. The problem is greater with lignite than with sub-bituminous coal, or coals of higher rank because of the structure and greater moisture content of the lignite. The most serious frozen coal condition occurs when wet snow or rain is falling as the cars are being loaded at the mine, followed by a rapid tem­perature drop. If the temperature drops sufficiently low the coal in the cars may freeze solid. If not, freezing may only occur one or two feet in from the sides, top, and bottom of the car; but the car hopper frequently freezes solid. In either instance the problem involves removing the frozen coal from the cars in such a condition that it can be fed through the conveyor belt system to the boiler storage bins. The following methods for dumping frozen coal are used at different plants with varying degrees of success:

1. Frozen coal next to the sides of cars and in the hopper can be thawed by hand torches. This method is not effective with solidly frozen carloads. Also, the cars can be damaged.

2. Frozen cars can be placed over heated thaw­pits; 20 to 30 min of heating is usually sufficient for cars which are not frozen solid. Cars will then con­tinue thawing on their own for some time, so that they are usually not dumped for 30 min to an hour afterward. Unsheltered thawpits are not very satisfactory.

3. At some plants car shakers are used to speed up the dumping operations.

4. Small dynamite charges can be used to loosen the coal.

5. Steam can be injected into the frozen cars. 6. Jackhammers, picks, and bars can be used to

loosen the coal. The average time required for this operation is 20 to 30 min per car.

The last method mentioned seems to work best for solidly frozen lignite which presents the most severe conditions. Thawpits are not as popular in areas of very low temperature, possibly because of the longer period of time necessary to thaw a solidly frozen car. Thawpits are completely effective when used with

56 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

car shakers on cars in which the coal is frozen for only about 6 in. from the sides, top and bottom.

The problem of frozen coal in cars can become no worse at temperatures lower than -40F except that outdoor worker activity becomes exceedingly difficult. At such low temperatures there is less likelihood of the cars becoming frozen solid, for the combination of weather conditions most conducive to car freezing occurs in association with a temperature range of 15 to 32F. Consequently the problem is met most often at temperatures of about 20F.

Preventative measures have been attempted, but as yet the results are not conclusive. The coal and the cars can be sprayed with an antifreeze solution (e.g., petroleum) at the mine tipple. Experience with this practice has been insufficient to evaluate the success of the measure. One company uses lignite as fuel and moving frozen lignite into their power plants is one of their chief winter problems. Under certain conditions they have had to smash practically every lump of frozen lignite individually by hand in order that the fuel could be loaded into the conveyors. Although the problem is a serious one, it is not critical. If necessary unfrozen lignite can be drawn from stock piles.

An antifreeze mixture of low grade fuel oil and organic solvents is sprayed upon car floors in the Mesabi iron mines. This appears to be successful in facilitating the handling of ore and fill during the winter [8].

Although at low temperatures coal freezes in the stockpiles, the depth to which frost penetrates is seldom more than two or three feet. Consequently the problem of moving coal from a frozen pile to a plant conveyor is not a serious one. The weight of a crane clamshell type bucket is usually sufficient to break through a fro~en crust. Bulldozers can dig coal out from beneath it. If necessary explosives can be used. Thus, although the problem becomes greater at lower temperatures, it is estimated that handling coal directly from a frozen stockpile would be feasible at -80F providing mechanical equipment functioned adequately.

Frozen coal can be fed to boiler bunkers without any difficulty, but if frozen and unfrozen coal are mixed in the bunkers a freezing problem may arise. This can be avoided if coal of approximately the same temperature is fed to the bunkers. Broken up frozen coal alone moves through the bunkers to the boiler without difficulty.

Systems of handling fuel at power plants differ depending upon whether the fuel is seasonally stock­piled, and whether it is lignite or coal. Because of its high bulk, lignite is usually stockpiled just for emer~

gency use, for example, 45 days supply may be kept at hand. As much lignite as possible is moved directly from the rail cars to the boiler plant so as to avoid double handling in and out of the stockpile. At such plants the fuel is unloaded from rail cars all winter and dumping frozen cars is a major problem. Plants which receive their fuel by water store it seasonally if necessary to avoid winter hauling by rail. For such plants frozen coal in cars is not a problem since stockpiles are drawn upon during the cold weather.

Problems arise in operating mechanical equipment at low temperature mainly because of the inability of some lubricants to permit cold starting and yet lubricate satisfactorily at running temperatures. Other problems are the low temperature brittle fracturing of structural parts which sustain impact forces, the freezing of coolants in radiators and cooling system, and the heating and defrosting of the operator's compartment. In large plants as a rule, space can be provided for garaging such equipment as bulldozers, trucks, turna-hoppers, etc. At small plants this is not possible without the additional expense of constructing a garage.

In general, vehicles cannot be counted on to start at temperatures below -30F, although such occur­rences have not been known to cause plant shutdown. Crane cabs can be heated, shelter structures can be mounted upon bulldozers, and oversize heaters and defrosters can be installed on all vehicles. Vehicles which must be left in the open can be kept warm by block heaters to make starting possible. It is estimated that with conventional mechanical equipment serious trouble might be expected at temperatures lower than - SOF. It seems likely that satisfactory operations might be possible at temperatures as low as -80F if such exposures were anticipated and remedial meas­ures taken.

Coal unloading units can be enclosed and heated if necessary. Steam lines can be run down beneath conveyor belts to provide heat inside the conveyor housing. Coal breaking and crushing equipment is generally housed within the power plant building, and can be readily heated if necessary to ensure low temperature operation.

In general mechanical equipment functions satis­factorily outdoors down to -30F. Serious problems can be expected below -50 F.

There are definite low temperature limits to outdoor work. During periods of extremely low temperature, outdoor work is eliminated if possible. At some small plants track coal hoppers are sufficiently large that several days fuel supply can be stored. Outdoor work becomes unnecessary during storms. (The most severe winter weather condition for outdoor work,

MAY 1957 ]. W. WATERS 57

the blizzard, is discussed below in the section on snowfall.) Further details concerning the effect of low temperature upon outdoor work is presented below in the section on power distribution. (2) Water intake and circulatory system. Water sup­ply problems can be critical at low temperatures depending upon the site and design characteristics of the power plants.* The overall water needs of power plants are very great. It is estimated that a plant that uses river or lake water directly to cool condensers would require about 60 gal per hr per kw of capacity (i.e., 15,000,000 gal per hr for a 250,000 kw station) [5]. If a cooling tower system is used, a minimum of about 0.6 gal per hr per kw (or 1 per cent of the above) would be required (i.e., 150,000 gal per hr for the above station). It is necessary that a supply be available during a period of minimum temperature. Plants which are designed to make use of a cooling tower system encounter additional problems in pre­venting low temperature freezeups.

At temperatures below 32F plant design and operations must take into consideration the freezing of water. Outdoor pipelines must be insulated, or buried below frost level; 6 ft seems to be adequate for temperature exposures down to -40F. Water intake structures must be designed to facilitate a continuous flow of water despite river ice. By installing ice breakers upcurrent from the intake, an ice boom across the intake, and by disposing of warm condenser water (at temperatures of 42 to 52F) so as to keep surface ice clear of the plant, a continuous supply of water can be maintained at temperatures as low as -40F.

(3) Boilers. Boilers are not sensitive to low temper­ature interference providing the temperature condition is anticipated in their design. Sufficient heat is gener­ated by boilers so that atmospheric temperature variations do not affect operations, provided that all pipelines and ancillary hydraulic equipment are suitably protected. Generally boilers are located within the power plant building. At some recently constructed plants, however, the boiler is outdoors. All piping is protected and usually the firing aisle is sheltered. Such plants operate successfully at temperatures as low as -40F but they must be provided with an

*See Paper V for a more detailed treatment of water supply problems in areas of extreme weather. There is a relatively ex­tensive literature dealing with the conservation of water in the electric utility industry. Among others are:

Farmer, A. E., 1952: Why and how of England's new cooling towers. Power Magazine, 96, no. 7, 94-95.

Powell, Sheppard T. and Bacon, Hilary E., 1950: Magnitude of industrial demand for process water. J. Amer. Water Works Assoc., 42, 777-785.

Salzman, M.G. and Elliott, Louis, 1951: Type of water supply influences location and layout of Texas steam-electric plants. Civil Engineering, 21, no. 5, 30-33.

auxiliary boiler to provide heat during periods when the main boiler is inoperative. If boilers are adequately housed it is estimated that they would function satisfactorily at the minimum temperatures which have been experienced upon the earth's surface.

(4) Turbogenerators. Turbines and generators must be cooled to remove their running heat. Consequently no problem exists in operating them at reduced temperatures. Turbogenerators can be started cold if steam is available. These units are located in some new plants in the open and performance is satisfactory to at least -40F. Operation would probably be possible at the earth's minimum temperature pro­vided the units were housed and the best lubricants used.

ii. Power production-hydro plants. A temperature of 32F is critical for hydroelectric generating plants. Above 32F no ice problems exist; below 32F such problems are encountered. No other critical temperature levels have been recognized. Subfreezing temperatures affect the runoff, the reservoir, the dam and its flow control devices, and the intake system.

Surface runoff is reduced during periods of low temperature. It may even approach zero. Thus, hydro plant capacity may be reduced depending upon the source of the stream water. During freezeup under­ground drainage is still likely to maintain a slight flow, but variations in flow brought about by sub­freezing temperatures need to be anticipated in the planning and designing of hydro plants. The volume of winter flow is not, however, determined by temper­ature alone. Other factors affect it more directly (e.g., nature of source, size, depth, and volume of reservoir, stream gradient).

(1) Water storage and intake system. Reservoir ice seldom freezes sufficiently thick to imperil operations providing an adequate flow into the reservoir exists, and the reservoir is sufficiently large. A thick layer of surface ice can reduce the effective head of water, but seldom sufficiently to make operating impossible. Ice five feet thick would reduce a normal head of 25 ft to 20 ft; yet operation would still be feasible.

Hydro plant dams must be kept free of ice to ensure their not being damaged. Concrete dams are particu­larly susceptible to frost damage. A temperature range which spans 32F seems to result in the most rapid deterioration of such structures through the alternate freeze-thaw action of the absorbed moisture in the concrete. A fluctuating water level can augment this destructive action. It seems likely that earth­filled dams would stand frost exposures better than concrete dams.

Air bubblers (warm air bubbled up beneath surface

58 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

ice) help mtmmtze ice thickness on reservoirs. It is possible to use heating devices along the dam itself or at sluice gates. If metallic parts exposed to water are heated above 32F, the formation of frazil ice in subcooled water will not tend to occur [16]. A practice at some plants is to heat one or two flood gates so as to alter the flow of water along the dam, resulting in the removal of all ice, or alternately to so control the opening of sluice and flood gates that reservoir currents are altered so that the dam remains ice free.

To keep intake gates, screens and racks clear of ice, heat can be provided in any form. Also, an arrange­ment of installations with respect to the current can divert ice from the intakes [9]. If a continuous flow of water can be maintained, it is estimated that intake equipment could be kept free of ice at the earth's minimum temperature. In general, the main problem in the successful operation of hydro plants at any temperature is not so much one of keeping a water supply from freezing, as of selecting a site at which the winter water flow is naturally sufficient to ensure continuous operation. Otherwise equipment will only provide power during the "runoff" season.

Frazil ice, anchor ice, and slush ice each impose operating problems which are overcome at most plants providing that an adequate flow exists [7]. Frazil ice is formed in turbulent streams when the water becomes cooled below freezing. Needles of ice form on the surface and are submerged by the tur­bulent waters forming a turbid mass of ice and water. Slush ice is caused by heavy snowfall on open water that is near or below the freezing point. It tends to choke intakes, penstocks and turbines, necessitating the closing of power facilities to clear the pipes. Compressed air forced through the water at the intakes has been effective in minimizing this problem. Anchor ice forms most rapidly on dark colored streambeds of turbulent streams on cold, clear nights. It will never form under a sheet of ice. Anchor ice thaws loose and floats away during days of bright sunshine. It is possible to accelerate the formation of surface ice on open streams and so reduce the frazil and anchor ice problem by introducing a barrier [17].

(2) Hydroturbine and generator. Low temperature operation of the turbines and generators of hydro plants presents no problem providing an adequate head of water exists. Winter water temperatures keep the equipment close to 32F at all times. Consequently lubrication presents no problem. Generally, turbo­generators are enclosed in a power house. This is not necessary, as far as the equipment is concerned, and at some new hydro plants the turbogenerators are

outdoors. Ice chunks which have passed through the penstocks do not interfere with turbine operation.

iii. Power production-diesel plants. Power plant build­ings can be so constructed and heated to sustain operations at the minimum temperatures which have occurred upon the earth's surface. Diesel fuel remains in a usable condition to at least -40F. Prior to motor use, however, it must be heated. This is usually done as the fuel enters the filter. Outdoor storage tanks need not be heated, providing there exists storage indoors for the warmed fuel.

Although diesel engines exist which will operate at extremely low temperature [15], units used for the generation of electric power generally need to be sheltered and heated. These engines cannot be started cold since the lubricants used for high running speeds will not permit starts at temperatures lower than OF.

iv. Power plant electrical system. This category in­cludes all electrical equipment such as cables, trans­formers, circuit breakers, bus systems, etc., which are located between the generator terminals and the transmission line terminals. Generally, all equipment included within this category is not affected by ex­posure to extremely low temperature. Problems which do occur are minor ones. For example, water cooled transformers function adequately to at least -40F. In plants of outdoor design, electrical equipment is unsheltered. Performance appears to be satisfactory.

v. Power distribution-substations. Substation equip­ment is generally not susceptible to low temperature conditions. The substation building is usually heated to about 65F for worker comfort. Generally only the control devices, meters, etc. are indoors. Transformers, circuit breaker equipment, and mechanical devices for operating it are located outdoors. Some low temperature problems arise in operating the circuit breakers; sometimes the oil becomes too stiff, and the operating mechanism fails to function. This seems to be only a minor problem that is being overcome with recently designed equipment. All difficulties in operating a substation could be overcome by enclosing sensitive units in heated buildings.

vi. Power distribution-transmission and distribution lines. The major low temperature problem involving transmission and distribution lines is the necessity for outdoor work. The temperature at which routine line construction and maintenance work is suspended varies from company to company depending upon the severity of the local extremes. One company suspends outdoor work at -10F or even somewhat higher, depending upon the condition of wind and snow. At another company routine work continues

MAY 1957 ]. W. WATERS 59

TABLE 1. Working efficiency of man at various temperatures [19].

Temperature (F)

70 20 0

-23 -40

-50

-80

100 75 50 25

Per cent efficiency

14 (Point where arctic native nor­mally becomes inactive)

10 (Point where man can no longer perform outdoor mechanical work, but must spend practi­cally all of his energy to survive)

0

to - 20F ( -10F if it is windy). In Alaska certain routine outdoor jobs are continued until the temper­ature reaches -30 or -40F. Thus the limit depends upon the experience of workers, and the frequency of occurrence of extremely low temperatures. It is the general practice of United States utilities to undertake emergency outdoor work at any temperature down to -40F. It seems possible that such work could be undertaken at even lower temperatures although not without considerable difficulty and loss of efficiency. It has been estimated, however, that at temperatures lower than - SOF a man can no longer perform out­door mechanical work, but must spend practically all of his energy to survive. Table 1 presents estimates of working efficiency at various temperatures.

All the foregoing information pertains to actual operating experience under low temperature condi­tions. It is augmented by estimates concerning operations at lower temperatures than the consulted utilities had experienced. Concerning these lower temperatures it is estimated that operations would be feasible with the following reservations:

1. The power house building must be adequately designed in terms of insulation, heating, and ventila­tion to maintain satisfactory indoor temperature (60 to 70F or higher).

2. All piping must be protected by insulation, heat, or by being placed underground.

3. Adequate frozen coal unloading facilities must exist.

4. Coal handling equipment must be fitted out for low temperature operations and must be provided with shelter for idle periods.

5. Year round water supply must be available for both thermal and hydro plants.

6. Transmission and distribution service equip­ment must be fitted out for low temperature operations and must be provided with protective facilities for idle periods.

7. Workers must be adequately clothed and experienced with low temperature exposure.

2. Ground frost

A prolonged subfreezing atmospheric temperature condition will result in frozen soil, providing that the soil is sufficiently moist. If such a condition prevails for only a brief period of time the depth to which frost penetrates will not be great. If, however, the period is not brief, frost may penetrate deeply into the soil and remain for a considerable proportion of each year. It may even exist permanently in the soil at very great depths (hundreds of feet). Construction problems created by the existence of deep ground frost and permafrost are considered in Paper III of this monograph. The present discussion is limited to the effects that permafrost will have on electric utility facilities.

Although no serious problem exists in constructing power houses and their auxiliary structures in areas which experience seasonal ground frost, it is difficult to construct and maintain such structures upon permafrost, because of their great weight and because of the great amount of heat which they generate [6]. Electric power generating plants comparable to those which exist outside of the limit of permafrost in North America would probably not be able to operate satisfactorily if built upon permafrost.

The following are the problems encountered, and the adaptations in equipment and practices made necessary in order that power utilities can operate upon permafrost:

i. Foundations for buildings. Generally all heavy per­manent structures which enclose continuous sources of heat (e.g., boiler houses, power plants) need to be constructed on piling and should be provided with an air space under the floor to allow a free circulation of air (desirable in order to maintain the permafrost at its natural level). The use of gravel mats is difficult, expensive, and not generally recommended except where accurate and extensive subsurface explorations show that the permafrost layer is comprised of fairly dense granular material devoid of ice lenses and layers [19]. Floors need to be well insulated. Piles (wood, steel, or precast concrete) need to be set at least twice the depth of the active layer into the permafrost. The length of the piling in the active layer should be surrounded with a layer of sand or gravel, the upper portion being well greased and encircled with a thick layer of tarpaper to prevent the adhesive forces from gripping the pile. The lower portion of the pile should be left rough and notched in order to increase the adhesive strength of the permafrost layer, thus decreasing its tendency to heave [4].

ii. Pole installation. Mechanical diggers (augers) will

60 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

bore through frozen soil satisfactorily but line poles set in frozen ground cannot be tamped down until the ground thaws in the spring. If the spring tamping is not done before windstorms occur, entire lines of poles can be blown over. Poles set in the active layer of permafrost can be stabilized by rock ballast. Thus, although it is frequently easier to erect poles in frozen soil than unfrozen soil, the results are im­permanent unless the poles are later stabilized when the ground softens. In areas where both the active zone and the underlying permafrost are composed of fine-grained, frost-acting materials, pole installation can be carried out in one of the following ways [19]:

1. Poles are placed into the permafrost to a depth about twice the thickness of the active zone. For suspension stream crossings or sharp turns, additional stresses can be provided for by installing additional butt poles and adequate guy wires, or by using H-frame construction.

2. In marshy terrain cross braced, rock filled cribs can be used for pole foundations.

3. For temporary installations, a tripod of three poles can be constructed with a weight suspended from the apex, or guy wires can be fastened to crosspieces bolted to the weighted bottom of the pole.

iii. Road instability. Frost heaving and spring ground­water movements soften roadbeds. In some instances line service operations necessitate the movement of heavy mechanical equipment over these roads. Load restrictions are sometimes imposed during this period to prevent the destruction of the roads. This is especially true for asphalt topped gravel roads. Dates of such restriction in Minnesota range from about March 15 to June 1. The restricted load varies with the structure and condition of the road. Loads in excess of the limit are permitted only during emer­gencies. Considerable inconvenience can result since heavy loads of poles or tower steel must either be broken down or hauled by roundabout routes.

iv. Dam construction. Special precautions are neces­sary in constructing dams. Heaving or settling due to the action of permafrost can more readily damage a concrete dam than an earth fill dam. Dam construction imposes special problems, involving excavation thaw­ing by heated water and refrigeration of surface prior to filling to prevent instability [11]. Dams on perma­frost must possess unique characteristics of flexibility, internal and external stability, and insulation. When masonry dams are constructed many expansion joints must be present to facilitate the inevitable deforma­tions that take place. Ground subsidence is minimized by defrosting all ice inclusions in the foundation and

filling with some type of grout, consolidating the thawed ground by vibration, or incorporating con­struction features that preserve the permafrost [14]. The tendency exists for the water stored behind a dam to thaw the underlying and adjacent ground, causing earth slides into the reservoir. The lowering of the permafrost table may impair seriously the stability of the structure due to the change in state of the underlying ground [4]. v. Piping. All piping must be installed in some form of heated "utilidor," unless exposures are small and the heat of the water or steam is sufficient to maintain a flow. Utilidors may be of wood, metal, or concrete, and may be constructed for water, steam, and sewage, or they may be combined into a single utilidor system which is subject to increased hazard of total failure [19]. vi. Water supply. Because most surface water freezes, dependable supplies must be based upon either large bodies of water (lakes or rivers) which do not freeze to the bottom, or sub-permafrost wells which may be highly mineralized [1]. A detailed water prospecting survey takes years and requires both summer and winter information concerning the lowest yield in terms of anticipated demand, and the seasonally varying quality of the water [18].

3. High temperature

High atmospheric temperature conditions have received attention in this study only because they occur as warm season characteristics of nontropical climates. Consequently this treatment of the effect of high temperatures upon electric power system operations will appear inadequate if judged in terms of tropical operating experience. However, due to the occurrences of extremely high temperatures in high latitude continental locations, the degree of heat experienced exceeds that of most tropical areas, for periods of relatively short duration.

The overall efficiency of electric power system operations will tend to decline from the maximum as the atmospheric temperature increases from the optimum of 40 to 75F. The rate of efficiency decline does not appear to be great, however, and there do not appear to exist any overall critical temperature levels beyond which a significantly lower degree of operational efficiency occurs. The decline in efficiency which does occur seems to pertain in most instances to worker activity rather than to equipment or machinery behavior.

4. Rainfall

Occurrences of rainfall do not in most instances significantly reduce the efficiency of utility operations.

MAY 1957 ]. W. WATERS 61

A heavy fall of rain creates a greater degree of inter­ference to operations than a light fall, but even the former does not produce any serious limitations, providing there exists an adequate drainage system. If the drainage system is inadequate, flooding may occur, resulting in operational interruptions, or even destruction to structures and equipment. Such oc­currences are avoidable, however, by means of adequate planning for power plant, transmission line, and substation sites.

Power plants are especially susceptible to flooding because they must be sited near river water level to facilitate an adequate intake system. Generally plant designs take into consideration the maximum recorded flood stage plus some fraction of the flood increment as an extra precaution (e.g., one-third higher). Consequently the length of record which is available affects the degree of susceptibility of a power plant to flooding. If a plant must be built at a level which is occasionally flooded, waterproof construction is possible.

Heavy rains, combined with winds, have, on occasion, brought down great quantities of leaves suddenly during the fall season. Clumps of the leaves formed by eddying currents have entered the intake, choked up the screens, cut off the water supply of a plant and nearly forced a shutdown.

5. Snowfall

The major single problem which arises as the result of snowfall stems from the areal spread of power utility transmission and distribution equipment. Line repair and maintenance operations can be greatly interfered with because roads become impassable due to the snow. Other problems of lesser severity involve coal unloading and handling, and worker arrival at power plants.

The snow condition that interferes most with power line repair and maintenance work is the blizzard. Blizzard conditions are most likely to occur at tem­peratures between 0 and -25F in continental United States. Temperatures lower than this usually occur in stable high pressure areas with relatively calm polar air. Snowfall need not be quantitatively great. A moderate fall of snow carried by winds of 30 to SO mph can reduce surface visibility to practically zero, and can create hard packed drifts which make roads impassable to standard wheeled vehicles. Power line breaks or damage are both difficult to discover and hard to reach, whether the lines follow the road or not. Modern highway snow removal equipment em­ployed in northern areas clears roads very rapidly. Moreover power utility companies are able to reach

any point on their lines during emergencies by using special track driven equipment such as the snow­mobile [3]. After winds have died down damage can be located by air reconnaissance. Airborne inspection of lines is considered to be more effective than ground inspection for many types of line and pole damage.

Blizzards and heavy snowstorms also interfere with workers arriving at power plants, many of which are somewhat isolated from builtup urban areas. At such plants emergency food rations are stored in case of such occurrences. Snow also imposes problems in the unloading and handling of coal at steam plants. If fresh snow falls into coal cars prior to, or during loading at the mine, solid freezing will be more likely to occur.

Snow loading on wires can be great and can cause breakages, but severe damage is not usual because the snow generally blows off. Snow does not have a direct effect upon transformers. Wet snow in which dirt has accumulated can, however, result in short circuit flashovers. Snow must be cleared from around all outdoor equipment at substations to make the equipment accessible.

The variability of snowfall from year to year con­tributes to the variability of surface runoff thereby affecting the long time power capacity of a hydro­electric site or the water supply of a steam plant. Such variability should, therefore, be taken into consideration in planning a power plant site.

6. Sleet, ice and frost

Only one major problem occurs because of sleet, ice, and frosts: transmission and distribution lines become coated, and if strong winds occur at the same time, severe damage to installations can result. Such oc­currences are not unusual, since the passing of a front over a region can create the succeeding conditions of a subfreezing surface subjected to subcooled rain followed by a drop of temperature and strong winds. In the National Electric Safety Code [20] three general degrees of ice loading are recognized and mapped as being heavy, medium, and light. Both wind speeds and ice thicknesses are taken into consideration in these generalizations. In the heavy loading district transmission lines are designed to sustain ice loads of one-half inch radial thickness in winds of 30 mph. A single cable which contains many lines seems to withstand wind damage better than many separate lines. Such cables will even support broken poles. They will sustain greater ice loads in higher winds than the equivalent number of single lines. Local distribution lines are not expected to carry such loads, but are more readily repaired, and interruptions

62 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

are not so critical. Sleet and ice do not adversely affect transformers or other outdoor substation equip­ment. Transportation becomes hazardous, however; roads are not blocked, but vehicle movement (for line patrols and repair work crews) is slowed down. Sleet and ice are no problem at the power plant. Coal dumping and handling problems are not seriously affected. It is pertinent to note, however, that sleet and ice storms are not common in areas of extremely low temperature, but occur most frequently along the warm margin of the area in which precipitation falls as snow all winter.

Sleet and ice storms are a serious problem only insofar as distribution and transmission lines are concerned. Interruptions which occur as the result of such storms are serious, and do reduce the operating efficiency of the power utility; but the lost power and damaged lines do not increase costs sufficiently to warrant the further protection provided by a duplicate system, or an underground sytem. The cost of pro­tecting lines would exceed the cost of repair plus the revenue lost due to interruption.

An accumulation of frost upon power lines can occur with temperature conditions slightly lower than freezing. The result is that the electric power load on the lines must be reduced. On occasion the reduction has been sufficiently great that it has become necessary to cut off service to marginal customers. Various methods such as dragging a rope along the line have been attempted to remove the frost. Frost occasionally remains on lines for several days.

7. Humidity

Atmospheric humidity conditions affect electric power utility operations in a few relatively minor ways. In nearly all instances a low absolute humidity and a relative humidity of 40 to 60 per cent is con­sidered the optimum condition. Departures from this condition will likely result in reduced operating effi­ciency in some instances and increased costs.

Power plants which utilize a recirculatory water system with a cooling tower are affected detrimentally by a high relative humidity in association with a high temperature. With these conditions the rate of evaporation is minimized with the result that the cooling tower becomes relatively ineffective. The water is not cooled sufficiently for adequate condensa­tion of spent steam in the main condensor. Thus the boiler steam pressure must be reduced. Power output declines. A loss of up to 10 per cent of a plant's capacity has actually occurred for this reason.

8. Wind

Serious interference with the operation of electric power utilities can result from winds of high speed. Therefore, for overall operations a condition of no wind or very light wind (to remove power plant smoke) can be considered optimum. As winds become moderately gusty, problems begin to occur. Such winds tend to interfere with outdoor worker activity to a slight degree, especially around the coal piles and coal unloading and handling equipment. Moderately strong winds can also blow coal dust and cinders out of power plant yards to nearby residential areas.

It is the strong winds which damage installations, cause power interruptions and generally create the more serious operational problems. Overhead trans­mission and distribution power lines are particularly susceptible to wind damage. These can usually with­stand winds up to about 50 or 60 mph, although as a direct result of such winds, damage frequently occurs due to flying objects, particularly trees and tree branches. Distribution lines suffer more than trans­mission lines, partly because trees and other structures are kept clear of the latter. In open areas the opposite seems to occur: transmission lines are more vulnerable because the lines are heavier and the spans between poles or towers are greater. In the open country these lines are seldom damaged in winds of less than 60 mph. It is pertinent to note that on open plains, and in the treeless arctic, there is, of course, no problem of wind damage to power lines from falling trees or branches.

Line failures usually consist of broken poles, cross­arms and wires (particularly at splices) caused directly by strong winds or by the impact of some object blown into the line by winds.

The results of a survey undertaken to determine the chief causes of line failures indicate the weather­induced faults are the cause of slightly over half of all service interruptions [2]. Of the weather faults the greatest proportion are created by the wind. Trees are involved in about one-third of the wind­induced weather faults. Accumulation of sleet and ice, in association with wind, also ranks high as a cause of line failures. These generalizations, derived from only a single year's experience, have not been based upon a sufficiently large sample of failures to justify including quantitative data.

It has been estimated that power lines could be constructed that would sustain winds of higher speed, even if accompanied by sleet and ice. Stronger lines, smaller spans, and sturdier pole structures would be necessary. However, not all occurrences of wind damage could be avoided, especially those occurring

MAY 1957 J. W. WATERS 63

during such violent storms as tornadoes. A consider­able degree of protection against all types of inter­ruptions can be obtained by erecting duplicate transmission lines, or by burying lines. Such steps become economical when the average losses due to service interruptions and equipment repair exceed the extra cost of installing either duplicate overhead lines or underground lines. It is interesting to note that although strong winds generally prevail from one direction in many areas, no correlation appears to exist between line damage and line orientation.

All power plant equipment is designed to sustain winds of relatively high speed. The power plant building itself is considered to be the most vulnerable, Experience of winds up to 100 mph at one plant did not result in interruptions caused by power plant failure. At another plant the conveyor structure and the power house have been designed for winds of 80 mph. At this plant 60 mph winds have caused no serious damage. Outdoor operations at power plants become hampered when winds exceed about SO mph. Conveyor belts, if not enclosed, are susceptible to wind damage, and special braces and brackets are necessary to maintain the rigidity of the structure and to hold the belt down on the rollers. Winds of SO mph have not interfered with the operations of unenclosed conveyor belts.

A few other effects of wind upon electric power utility operations merit inclusion. Continuing strong winds can lower or raise the level of water at a power plant so as either to flood the plant, or to leave the intake high and dry. This has occurred at a plant situated on a river. Runoff was sufficiently accelerated by a strong wind which prevailed downstream that the plant had to close down for lack of water. Wind can also blow debris and ice into intakes. Wind has been known to alter suddenly the course of a stream occupying a wide flood plain, so that the intake can be left without water; this has occurred on the Missouri River. The level of a hydroelectric plant reservoir can be altered by strong winds so that the effective head becomes appreciably reduced, or alternately, that the high water must be discharged over the spillway to prevent plant flooding. Most of such hazards can be prevented by adequate planning for the plant site. Proper design and construction of the water intake system for both hydro and steam plants is very important in view of the effect of winds.

9. Lightning

Lightning can damage electric power transmission and distribution lines, transformers and other sub­station equipment, causing serious service inter-

ruptions. In areas in which lightning storms are com­mon, damage to installations can be appreciable, and limitations to operating efficiency can be significant.

Although equipment can be struck directly by lightning, this seldom happens. Some protective devices are highly effective in protecting equipment from nearby flashes. Lightning arrestors protect power plant equipment and substations. Transformers are particularly vulnerable to lightning damage, and those mounted on poles, although shielded, are occasionally struck directly. Substation or power plant transformers are struck very infrequently. Some companies protect their transmission lines (over SO,OOO kw) by stringing a grounded conductor on top of the poles to serve as a continuous lightning rod. These extra protective lines are not completely satisfactory, however, since it is estimated that they increase line losses due to winds, because transmission systems having the extra lightning protection are more vulnerable to wind damage, especially when ice loading conditions prevail. Lightning damage affects operations directly but protective devices exist to ensure relatively continuous operations. It is pertinent to note that lightning is not frequent in areas of extremely low temperature.

10. Sunlight

Although sunlight is of minor importance insofar as the operations of electric power utilities are concerned, certain conditions of sunlight do have a direct effect upon operations. The optimum condition consists of constancy of light, or changing intensity of light which occurs only very gradually. If dark clouds suddenly obscure the sunlight without advance warning, a suddenly increased power demand can occur in a large city as the result of the simultaneous switching on of lights. Large sudden demands of extra power cannot be supplied unless extra steam pressure already exists in standby boilers. Otherwise power service to some consumers must be interrupted and it takes from four to five hours to heat up a boiler. Providing accurate weather forecasting service is available, interruptions caused by such occurrences can be avoided.

11. Conclusions

In table 2 the weather elements which most affect each of the various subdivisions of an electric power utility are indicated.

The most serious weather-induced limitations are imposed upon electric power utilities by permafrost and low temperature. This is despite the fact that in some areas sleet, wind, lightning, and snow are

64 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

TABLE 2. Relative effect of weather elements on electric power utility subdivisions

Note: Numbers pertain to the order of severity of effect of weather elements (in their most extreme condition) upon each of the subdivisions of operations or equipment. "X" indicates those conditions which limit operations but for which the relative effect has not been evaluated.

Example: Hydro plant operations (IB, below) are interfered with most severely by ground frost, next most severely by low temperatures, and also by rain, snow, and wind (unranked).

Low Ground High Electric power utility subdivisions temp. frost temp.

I. Power production 2 1 A. Steam plant X 1

1. Coal 1 2. Water 1 X 3. Boilers 1 4. Turbogenerator 1

B. Hydro plant 2 1 1. Water 1 1 2. Turbines and generators 1

c. Diesel plant 1 2 1. Diesel fuel system 1 X 2. Diesel engine 1 X

D. Power plant electricel system 2 II. Power distribution 4 X X

A. Substations X 3 B. Trans. and dist. lines 4 X X

III. Overall operations 2 1 X

considered to be more serious. In such areas extremely low temperatures do not normally occur, and perma­frost does not exist. Sleet, wind, lightning and snow are only relatively more severe in those areas than low temperatures and permafrost.

Although both permafrost and low temperature affect electric power utility operations as individual elements, there are other instances in which combina­tions of weather elements in association impose the limitations. Three such combinations of elements have particular significance in terms of electric power utility operations: sleet storms (ice accumulation as the result of precipitation, subfreezing temperature and high wind); lightning storms (lightning, wind and rain); and blizzards (snow, wind, low temper­atures). Each of the three affect the transmission and distribution system most; by comparison power plant installations are less vulnerable. It is not possible to generalize, however, concerning the relative severity of each. It is only possible to observe that by incor­porating relatively minor changes in equipment and practices, and by accepting a slight reduction in efficiency, operations comparable to those of average United States utilities are possible.

REFERENCES

1. Alter, Amos ]., 1950: Water supply in Alaska. J. Amer. Water Works Association, 42, 519-532.

2. American Institute of Electrical Engineers, 1950: Progress Report on Coordination of Construction and Protection of Distribution Circuits Based on Operating Data for Year 1949, New York, New York.

Sleet, ice and Humid- Light- Sun-

Rain Snow frost ity Wind ning light

X X X X X X X X X X

2 X 2 2 X 3

X X X 2 2 3

3 X 1 X 3 1 2

2 X 1 X 3 1 1 2 X X X X X X X

3. Automotive Industries, 1949: The snowmobile, Canada's winter vehicle. 100, no. 7, p. 31.

4. Army Headquarters, Directorate of Engineering Develop­ment, 1949: Permafrost, A Digest of Current Information, Ottawa, Canada.

5. Carr, T. H., 1951: Electric Power Station. London, Chapman and Hall, 3rd ed., Vol. 1, p. 96.

6. Eremin, A. P., 1936: Settling of electric power station con­structed on permafrost. Vestnik Inzhenerov i Teknikov, 22, no. 5, 282-287. (Abstract SIPRE Report 12, Vol. 2, p. 345, S.I.P. U2392.)

7. Farrow, R. C., 1950: Frazil and anchor ice. Proc. Western Snow Conference, Fort Collins, Colorado, pp. 29-31. Dis­cussion by R. L. Parsha, pp. 31-36.

8. Friedman, Edwin A., 1953: Problems encountered in winter stripping of open pit mines in N9rthern Minnesota. The Minnesota Engineer, 4, no. 3, 11-13.

9. Gisiger, Paul E., 1947: Safeguarding hydro plants against the ice menace. Civil Engineering, 17, 24-27.

10. Hanson, R. M., 1948: Operation and maintenance of outdoor plants found practicable. Electrical World, 130, no. 7, 93-96.

11. Huttl, John B., 1948: Building an earth-fill dam in arctic placer territory. Engineering Mining J., 149, no. 7, p. 92.

12. Iliff, D. G., 1951: Semi-outdoor plant for -40F weather: The Frank Bird steam electric station. Power Engineer, 55, no. 4, 56-59.

13. Knowlton, A. E., 1947: Seasonal load spread: Is it enough for maintenance? Electrical World, 127, no. 15, 91-98.

14. Lewin, J.D., 1948: Dams in permafrost. Public Works, 79, no. 567, 22-23; 32; 33-34; 57-58.

15. Military Engineering, 1948: Machinery in the antarctic. 40, p. 429.

MAY 19$7 ]. W. WATERS 65

16. Murphy, John, 1930: Ice problems in power development. Construction Engineering, 58, p. 612.

17. Ofitserov, A. S., 1950: On problems of ice cover growth and the acceleration of ice formation. !Yfeteorol. i Gidrologiia, No. 2, 58-60. (Abstract SIPRE Report 12, Vol. 2, p. 334, S.I.P. U2338.)

18. Tolstikhin, N. I., 1938: Instructions for the search of water supplies in permafrost regions. Akad. Nauk SSSR, Mos-

cow-Leningrad, pp. 193-212. (Abstract SIPRE Report 12, Vol. 2, p. 259, S.I.P. U1991.)

19. U. S. Army, 1950: Construction of runways, roads, and buildings on permanently frozen ground. Department of the Army Technical Bulletin, TBS-255-3. 87 pp.

20. U. S. Government, 1941: National Electric Safety Code, 5th ed., Part 2 (National Bureau of Standards Handbook H32), p. 97.

INDUSTRIAL OPERATIONS UNDER EXTREMES OF WEATHER

by J. A. Russell; W. W. Hay; J. W. Waters;

H. E. Hudson, Jr.; J. Abu-Lughod, W. J. Roberts, and J. B. Stall; A. W. Booth; and E. F. Taylor.

Edited by J. A. Russell.

V. PROBLEMS OF INDUSTRIAL WATER IN AREAS OF EXTREME WEATHER CONDITIONS

By J. ABU-LUGHOD, W. J. ROBERTS, AND J. B. STALL*

Illinois State Water Survey Division

Edited by H. E. HUDSON, JR.** Hazen and Sawyer, Engineers, New York

(Original manuscript received 27 March 1956; revised manuscript received 24 October 1956)

ABSTRACT

Extremes in climate present special industrial water requirement problems. Significant points pertaining to general water needs in industry are discussed and conservation methods applicable to most types of industrial establishments are outlined.

The availability of surface water is considered from the standpoint of development, distribution, and handling of water under extreme climatic conditions. Water requirements for industrial establishments are estimated by means of a nomograph which accounts for stream discharge, water demand, and drainage area.

The problem of industrial water requirements has not been given adequate attention in the United States because water has usually been fairly abundant in any region chosen for an industrial location. Within the United States it has therefore been possible to establish industrial plant locations on a basis of availability of transportation, raw materials, labor, etc.

In many industrial establishments where water resources are ample, the use of water may greatly exceed the necessary requirements. In general:

1. Plant location is determined by many factors, of which water supply is only one consideration.

2. The importance of water supply as a factor in plant location varies in almost direct relation to the quantities of water consumed and to the ratio of water cost to the value added by manufacture.

3. Every industry requires water for fire fighting, sanitation, and housekeeping. The amount of water required for these purposes, however, is usually small both absolutely and in comparison to the amount of water required for process, steam generation, and cooling purposes.

* Basic material prepared by these individuals as staff members of the Illinois State Water Survey.

** Present affiliation: Hazen and Sawyer, Engineers, New York.

66

4. The major differences between types of m­dustries are to be found in the requirements for water for cooling, power, and process uses.

5. In United States industry, the single most important industrial use of water is cooling. The largest users of water (power, petroleum, iron and steel) are industries which use the greatest propor­tion of their water for cooling purposes.

6. Water requirements for cooling can be varied from nearly zero (by substitution of air or refriger­ant and cooling techniques) to the enormous quan­tities used for once-through-and-waste water cooling systems [27]. Between these extremes are found values dependent upon the use of conservation techniques such as use of spray instead of immersion for washing and cooling operations, recycling of cooling water by passing it through ponds or cooling towers, successive use, elimination of waste through controlled flow, m1mm1zation of evaporation through closed cooling systems, and use of non­potable sources such as sewage or salt water for certain cooling operations.

7. Quality requirements differ from one industry to another and, within the individual plant, from one operation and function to another. These

MAY 1957 J. ABU-LUGHOD, W. J. ROBERTS, AND J. B. STALL 67

quality requirements are sometimes equal in im­portance to the quantitative requirements in decisions concerning plant location, choice of con­servation techniques, and economic feasibility.

This paper discusses aspects of industrial water requirements and conservation methods that are applicable to nearly all types of industrial establish­ments. The available information on conservation of industrial water is reviewed in some detail in the papers on specific industries to point out possibilities that may influence industrial location and operation. This information is not sufficient for design purposes. For such purposes, standard reference books are required.

1. Use and conservation of water in industry

i. Major industrial uses of water. Every industrial plant uses water for sanitation, drinking and wash­rooms, and generally. maintains a supply for fire fighting and other emergency uses. These require­ments, however, are small. The major uses of large quantities of water are for steam generating plants to supply energy for the industrial operations, for clean­ing and rinsing or transporting raw materials or products, for incorporation into the· finished product or process, for cooling the operating equipment, and for condensing purposes [43].

Estimates of the percentage of total water circulated that is used for cooling vary considerably-from one­third to three-fourths of all industrial water used in the United States. The latter estimate is suggested in the Paley Report, which states that: "By far the greatest use of industrial water is in cooling or heat exchange. Probably 75 per cent of total industrial demand is for this purpose" [63].

The former estimate (one-third) is made by the National Association of Manufacturers in their study Water in Industry [37]. Another third is utilized as process water, that is, water which is either incor­porated into the finished product or placed in direct contact with the product at any stage. An additional 10 per cent is used as boiler feedwater; and another 15 per cent for sanitary and service uses. The re­mainder is used for miscellaneous purposes such as fire fighting, air conditioning, etc.

Of all water circulated in the larger water using plants (using in excess of 107 gal per day) 54 per cent is used for cooling, as compared with 32 per cent for process, 9 per cent for boiler feed, 6 per cent for sani­tary and service uses, and 4 per cent for miscellaneous uses [37].

In steam power generation, over 90 per cent of all water circulated may be used for cooling purposes,

and some oil refineries report that up to 97 per cent of the water goes for cooling and condensing. Even in the processing of food, where large quantities must be utilized for washing, diluting, and processing, it has been estimated that SO per cent of all water is used in cooling operations.

Because the greatest opportunities for water con­servation are to be found in the re-use of cooling water or in the substitution of cooling methods using little or no water, there is a direct relationship between the percentage of water required for cooling and the variability of the industrial requirement for water. This makes the problem of anticipating probable industrial locations from water requirements difficult, since those industries which seem most dependent upon large quantities of water are industries which, by technological devices and conservation measures, can potentially decrease their water requirements the most. Such conservation methods are the key to the problem of industrial location in areas of extreme climatic conditions where adequate water supplies are likely to be costly to develop. Water consumption can, of course, be reduced in many other industrial operations, such as washing, processing, sanitation and service, but the major economies in water intake will be achieved through the reduction of water required for cooling.

ii. Variability of demand. Normally the water require­ments of a particular industry will not vary sub­stantially from year to year unless operations are expanded or contracted, nor will the water demand of an industry vary greatly from month to month unless the industrial operations are highly seasonal, in which case the daily water requirements will not vary greatly within each season.

iii. Water conservation methods in areas of extreme weather conditions. Flow control, the most obvious arid effective means of conserving water, will not be dis­cussed because the technique is unaffected by condi­tions of extreme weather. Basically, water used for cooling may be conserved by elimination of water as a coolant and by re-use or recirculation to keep make­up water to a minimum. Air coolers or closed liquid cooling systems which require no make-up water may be used for industrial cooling operations in areas of extreme cold and in hot dry climates where water is not accessible.

Although air cooling is more efficient in the areas of extreme cold where lower final temperatures can be attained, there have been a number of applications in hot dry areas. At the Sun Oil Plant in Texas, 90 per cent of the cooling is done by air, and the furnace-type carbon black plant at Borger, Texas, by

68 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

" ... maximum air cooling, uses only one-fourth gallon of water per pound of carbon black produced, whereas similar water cooled plants average four to fourteen gallons per pound" [63].

In general, where water supply is not a factor of overwhelming importance, air cooled heat exchangers are selected for high level heat removal (for example, where temperatures must be reduced from above 130F). Degler states that, although " ... normally the cooling tower is more economical, ... the cost of the dry cooler decreases relative to that of the tower as the temperature of the fluids to be cooled rises." He also advocates the use of air cooled heat exchangers where water is scarce, expensive or badly polluted and where low maintenance costs are desired [12].

Olstad advises that at temperatures above 180F dry air cooling ordinarily is more economical [38].

Laubach [30] offers the following rule of thumb for deciding between air cooling versus cooling towers: Where the temperature of the material to be cooled is above 160F, it is more economical to use air cooling; where products to be cooled are at temperatures below 120F, it will be more economical to use cooling towers. Decisions as to the technique to be used for the range between these two figures will be based upon the cost and availability of water.

(1) Refrigeration. The air cooled refrigeration system not only eliminates the need for water as a cooling agent, but may also result in an additional decrease in the water used. When designed to use waste thermal energy of other processes to power the refrigeration unit, it reduces the amount of water required to dissipate such waste energy. In general, where final temperatures not more than 10F above the maximum wet bulb temperature are desired, a refrigeration unit is the best available cooling method, for lower temperatures are not obtained by evapora­tive water recycling techniques under United States economic standards.

The refrigeration unit will, of course, be at maximum operating efficiency in the colder regions, although, because of the opportunities of air cooling to extremely low temperatures in these regions, it may not be as essential as in hot dry climates where its efficiency is lower.

In addition to the standard refrigerating devices, industry can utilize some of the excess heat carried by cooling water to operate a water chilling refriger­ation system [19, 24, 51, 65].

(2) Evaporative cooling. The cooling effect produced by the evaporation of one pound of water per minute is equal to 4.85 tons of refrigeration per day [49]. A ton of refrigeration is the cooling obtained equiva-

lent to the melting of one ton of ice, that is, the absorption of 2.88 X 106 btu. Evaporation of one pound per minute of water is equivalent in refriger­ating effect to the use of about 3.6 kw of electric power. Where relative costs are for water about ten cents per thousand gallons, and for power about one cent per kwh, it is six times more economical to use water for heat dissipation than to use electrical energy. This does not include equipment amortization.

The three major devices for evaporative cooling are the pond, the tower, and the evaporative condenser. The efficiency of any of these methods of evaporative cooling is dependent upon climatic factors, and their application will be confined to those areas where the ambient air is capable of absorbing large quantities of moisture. In cooling by evaporation about one quarter of the heat dissipation is through transfer of sensible heat and the remaining three-quarters through the latent heat of evaporation of a small part of the cir­culated water. The rate of heat removal depends on (a) area of water exposed to the air, (b) the difference between the water temperature and the wet-bulb temperature, (c) the relative velocities of water and air at contact, and (d) the time of contact [11].

Although cooling devices are generally designed with reference to a wet-bulb temperature of 75F (a temper­ature exceeded no more than 5 per cent of the time in most temperate regions), in hot arid regions lower wet-bulb temperature designs are available. For example, the design wet-bulb temperature in Denver, Colorado, is 64F and that in El Paso, Texas 69F [15]. An efficient cooling tower can lower the temperature of the water to within a few degrees of the wet-bulb temperature [1]. A 10 degree "approach" is more commonly attained.

The water cooling device which has had the most widespread industrial applications is the cooling tower, which is a" ... hollow vertical structure with internal baffles to break up falling water so that it is cooled by upward flowing air and evaporation from the extended surface of the water" [4]. Cooling towers may be either of the natural draft variety, or of the forced- or induced-draft variety, which employ power­driven fans at the air inlet or outlet, respectively, to increase the circulation of air.

As has been pointed out above, the major use of cooling towers for a recirculation system will be found in hot dry climates. Despite this generalization, cooling towers are widely used in temperate zones for establishments that do not require water temperatures near or below the wet-bulb temperature [15].

Degler states that " ... extremely cold weather normally does not increase performance (of cooling towers) to any great extent, but operating hazards

MAY 1957 J. ABU-LUGHOD, W. J. ROBERTS, AND J. B. STALL 69

are increased considerably" [13]. Two operating hazards are fogging and freezing. Fogging occurs when the tower ices and the fans move less air. The air leaving the tower at low speed and high temper­ature causes fog when warm tower air mixes with the colder ambient air. Thi.s fog difficulty is worse however in mild winters than in subzero temperatures [14]. The second and more important problem is that of ice formation in the tower. Ice formation generally occurs only on parts of the tower that are lightly wetted by fine drops which splash toward the entering air stream. Advice on how to minimize such hazards has been given by several writers [13, 14, 31].

Spray and cooling ponds comprise another class of devices that help industry to re-use cooling water. "Cooling ponds may well be more economical than other methods of supplying cooling water to plants more than 2000 to 3000 ft from a river, where a temperature 3 to 4F above river temperature is ac­ceptable and where the terrain is suitable .... Cooling ponds ... may operate for extended periods with ~o make-up. For design conditions that might be con­sidered average, one to two months without make-up would be possible" [29].

A spray pond is capable of doing the same amount of cooling with one-fiftieth the amount of space required by a cooling pond without spray. Some of the advantages of the spray pond over a cooling tower are: (a) no power requirements for fans, (b) low maintenance. Some of the disadvantages of spray ponds for cooling are (a) spray drift and (b) limited cooling performance. "It is impractical to design spray ponds for severe cooling conditions-close ap­proach to wet-bulb with a long cooling range" [11]. Where wide performance ranges are desired, the cooling tower will be preferred, since, by altering the physical dimensions of water concentration, the per­formance of the tower can be changed as desired.

Although evaporative cooling in an open system­represented by the cooling tower and the cooling pond-is most widely used in industry, there is an­other device which operates on the principle of evaporative cooling which is coming into more com­mon use, where considerations of design flexibility and low initial water requirements are important [21].

The evaporative condenser or cooler is " ... the method of removing heat from a fluid inside a tube coil by transferring it to a water spray on the outside of the tube. A stream of air then picks up the heat in the form of water vapor as the spray evaporates" [38]. The advantages of such an evaporative con­denser over the water tower condenser combination have been enumerated by Martin [32]. The evapora­tive condenser (a) takes less space; (b) evaporation

takes place within the unit so less water must be pumped; (c) friction losses are lower; and (d) indoor and outdoor installation is more feasible. Like air cooled heat exchangers, however, evaporative con­densers are better suited for high level cooling of fluids down to say, 130F [68]. (3) Other conservation techniques. The foregoing dealt entirely with conservation methods needed for heat dissipation. There are many other methods of water conservation employed for other purposes. Prominent among these is the use of low quality waters, such as reclaimed sewage or seawater,instead of high quality fresh water [39]. Also important is successive use of water, first in the process requiring highest water quality, then in subsequent processes where requirements are less exacting [48]. iv. Water quality. The quality of water required for various industries will vary with the industry. Since a large part of industrial water is utilized for steam generation and for cooling purposes in power plants, the quality requirements for these purposes may be listed briefly. A good boiler feedwater is one which will not (a) form scale which interferes with efficient heat transfer on boiler tube surfaces, (b) be corrosive to the boiler or produce steam that will corrode steam or condensate lines, nor (c) cause foaming or priming.

Such a desirable boiler feedwater would therefore (a) be free from calcium and magnesium compounds (to eliminate scale), (b) be slightly alkaline and free from dissolved oxygen (to prevent corrosion), and (c) have a minimum dissolved solids content (to avoid foaming and priming, and to reduce boiler blowdown to the maximum extent possible). v. Determining industrial requirements. Some general­izations may be stated regarding the magnitude of industrial water supplies in the United States. The largest supplies, utilizing as much as 1000 mgd (million gallons per day) for a single industrial establishment, have been developed for cooling pur­poses in conjunction with condenser water cooling for steam generation of electric power. There are numerous steam power plants using water at rates of 500 mgd in the United States. These are central stations that serve power through large areas. Aside from these once-through-and-waste systems for power generation, very large systems are not so commonly encountered in industry for individual establishments. Certain steel works develop supplies of 200 to 300 mgd for cooling purposes without conservation methods in areas where water resources are abundant, but ordinarily a large individual industrial establish­ment will not require more than approximately 30 mgd if certain simple conservation techniques are

70 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

TABLE 1. Maximum, minimum and average water requirements per unit of production in a selected sample of industry groups

Product or user

Steam power generation (Cooling only)

Petroleum refining

Finished steel

Soaps and edible oils (Combined plant)

Carbon black Glass containers

Natural rubber Synthetic rubber

(Incl. butadiene distilling)

Maximum water consumption

170 gal per kwh (a)

44.5 gal per gal crude oil [48]

65,000 gal per ton (cJ

7.5 gal per lb product [39]

14 gal per lb 667 gal per ton glass [39] 507 gal per ton glass [39] 6 gal per lb rubber [39] 309 gal per lb of GRS

Average water consumption

80 gal per kwhthl

18.3 gal per gal crude oil [27]

40,000 gal per ton Cdl

4 gal per lb

Minimum water consumption

0.45 gal per kwh [15] 1.20 gal per kwh [43] 1.32 gal per kwh [47] 0.8 gal per gal crude oil [39] 1.0 gal per gal crude oil [39] 1. 73 gal per gal crude oil [48] 1400 gal per ton Cel 4000 gal per ton to 1.57 gal per lb product

0.25 gal per lb 118 gal per ton glass 192 gal per ton glass 2.54 gal per lb rubber 1-19 gal per lb GRS (gl

tal NAM sample firm (dl Iron and Steel Institute (bl Ohio Water Resources Board tel Fontana Division of Kaiser Steel (cJ Ohio Water Resources Board (fl Estimate of Utah Steel Plant water use (gJ Unpublished letter from F. D. Kelly, Director, Office of Synthetic Rubber, Reconstruction Finance Corp., 30 October 1953,

employed. Where conditions limit the amount of water available, similar establishments may be able to operate on much smaller quantities.

In areas where water resources are abundant, there is no practical limitation to the capacity of the water supply system that may be installed using surface water, but there are very definite practical limitations on groundwater development. The largest commonly used unit for obtaining groundwater in the United States are special groundwater collectors which con­sist of shafts of approximately 16 ft diameter sunk vertically to the level of the water bearing formation (usually not more than 150 ft). Through the walls of these shafts horizontal perforated pipes are forced out to admit water into the shaft. Such units com­monly have capacities of 4 to 20 mgd each, and are most often installed in alluvial unconsolidated mater­ials where flow of water from a river or lake into the ground may be induced by pumping.

Wells of various types are constructed for develop­ment of water from ground sources. Ordinarily a well for a large industrial supply will have a diameter of approximately 20 in. and whatever depth is necessary to reach the water bearing formation. An individual well capable of yielding 700 gal per min or more is considered to be a very high grade installation, and. the capacities of such wells seldom exceed 2500 gal per min. Such wells may cost as much as $100 per ft of depth. Wells for large supplies should be spaced so that pumping one well will not unduly lower water levels in adjacent wells.

From a practical viewpoint, therefore, a ground­water development for an individual industrial establishment will seldom have a capacity in excess of 20 mgd, but any capacity below this is apt to be

found where conditions are favorable. Where larger quantities of water are required, it is most common to use surface water sources.

The only method known for estimating industrial requirements in the absence of detailed studies of the individual establishemnt is that based on unit figures. The unit figure needed first is the production rate to be expected in the industrial establishment. This refers to the number of units of product that will be pro­duced per unit time. When an estimate of the produc­tive capacity for an individual establishment has been made, water requirement data may be taken from the tables given in the chapters on separate industries or from table 1.

If upon investigation it should develop that the estimated water requirement is greatly in excess of the quantity available, then the possible employment of technical measures for water conservation should be considered. So far as has been possible, table 1 gives the minimum value for use in estimating water requirement where conservation techniques are em­ployed. To this should be added water required for the workers.

vi. Waste disposal.* Any discussion of water problems that is concerned with water availability must pay heed to the effects of waste disposal on water resources. The most economical method of waste disposal modern society has found makes use of flushing wastes away in a stream of water. Unfortunately, discharged waste-laden liquids gravitate to water courses and inevitably foul them.

*See Thomas, Harold Allen, Jr.: Investigation of Sewage Treat­ment in Low Temperature Areas, National Research Council, Committee on Sanitary Engineering and Environment, May 1950, SIPRE reprint, for a more complete analysis of this problem.

MAY 1957 J. ABU-LUGHOD, W. J. ROBERTS, AND J. B. STALL 71

Some improvement in the quality of the wastewater takes place enroute downstream through the operation of oxidation and sedimentation, but the unrestricted discharge of wastewater frequently results in de­terioration of water quality downstream or under­ground to such an extent that purification of the contaminated water becomes very costly, and in some cases prohibitive.

In areas where surface water resources are copious, there may be sufficient dilution of wastes to render them unobjectionable. Self-purification in streams should proceed more rapidly in warm climates than in cold ones.

Generally speaking, disposal of wastes can be reduced as a hazard by waste treatment processes that are well known and increasingly widely used by modern industry. Costs of waste disposal tend to be roughly proportionate to cost of water supply develop­ment. Where water supply is easily developed, there is apt to be sufficient flow to dispose of wastes by dilution. Where water supply is hard to develop, more complete waste treatment is likely to be re­quired because of the lack of dilution. One major exception to this lies in situations near the sea, which may effectively be used as a disposal place.

In modern society, waste disposal has come to be as severe a limiting factor on industrial location as water availability, and must be reckoned as a powerful influence on industrial development.

2. Availability of surface water

The majority of American industrial establishments use water obtained from surface sources, namely, rivers, streams, or lakes. The availability of water in these sources is dependent on a number of factors, most prominent of which are precipitation, temper­ature, evaporation, permeability of soils and sub­surface materials, topography, and vegetation. The section that follows deals with the availability of water from surface sources, principally from streams and rivers. Natural lakes of large size are excellent sources of surface water and may frequently be used without extensive investigation as to their capabilities.

Time utility is a primary consideration in industrial water supply since the normal water supply require­ment does not fluctuate greatly. An industry which is directly dependent upon a flowing stream for a con­tinuous supply of water can be certain of an un­interrupted supply of water only as large as the minimum flow of the stream. The excess of stream flow during flood periods is quickly passed on down stream and unless storage is provided, it is not available for use. The construction of a storage

Water Avai I able

High, welt distributed precipitation

High precip.~ somewhat var 1 able

Mediume~recip., un if arm

Medium precip. somewhat variable

Medium precip., highly variable,

or

Low precip, rela­tively uniform

Low toto I precip., highly variable.

Quantity of Wafer Needed

Medrum 0

Sup pi y

Smoll 0

Supply

Difficulty of Water Supply Development

HiQhly difficult to develop a supply.

(· Must be on lor9e river or oroctice extreme supply or conservation measures.

(·

Fairly difficult to develop a supply. Considerable judg­ment needed and water conservation and re-use

Sup pi y can -be deve roped by use of selected site, storage or 'Water conservation prac­tice. No big prob I em.

Supply can be developed with on I y minor limitations as to site and use.

No water supply problem. Con be developed at almost any location. No restrictions on use.

FrG. 1. Block diagram showing the difficulties of water supply under various climatic regimes.

reservoir on the stream may greatly increase the dependable supply of water which can be taken from the stream. It is seldom possible to construct a reservoir large enough to store the entire stream flow during periods of high flow. The optimum supply of water which can be developed at a particular location is dependent upon the presence of a reservoir storage site, the cost of construction of the storage reservoir, and the value of the increased quantity of water available.

When a number of locations are available for a particular industry it is usually possible to place the plant where the water supply possibilities are best. Consequently, it is normal to choose a spot where groundwater formations are likely to yield the quantity of water required, or a location near a flowing stream which either carries the amount of water required or could furnish the amount of water required to a storage reservoir.

A special issue of Power Magazine [66] gives a concise well illustrated report of the general aspects of an industrial water supply.

i. Effect of climate on water supply. The water supply of the earth may be considered as fixed in amount

72 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

and as moving continuously from the ocean and from the land to the atmosphere thence through precipita­tion to the earth, thence laterally back to the ocean. Winds carry moist air inland from the oceans where the moisture is dropped as rainfall on the land. Climatic factors are important in studying moisture movement since the climate greatly affects the operation of the water cycle. Koppen's climatic classification is used as the basis for the present study.

In an area of temperate climate the development of a satisfactory water supply is usually simple, requiring only common reason and judgment. On the other .hand climates having extremes of temperature, precipitation, or winds pose serious problems in de­veloping a water supply.

The problems of water supply under various climatic regimes are illustrated in fig. 1, which is a water supply nomograph developed by J. B. Stall. In fig. 1 the left column shows the availability of water on the land, which varies from high well­distributed precipitation at the top to highly variable low-total precipitation at the bottom. The right column of fig. 1 shows the increasing problems of water supply development varying from no water supply problem at the bottom to a highly difficult water supply problem at the top of fig. 1. The center column of fig. 1 shows the quantity of water which can be developed under the conditions set out in the right and left columns of the figure. This column contains three quantities of water, labelled large supply, medium supply, and small supply. These descriptions might be interpreted as follows: large supply, 100 million gallons per day (mgd); medium supply, 10 mgd; and small supply, 1 mgd. Any straight line connecting a box on the left column to a box on the right column will pass through the quantity of water available or needed.

ii. Considerations other than climate. Any physical characteristics of the earth which affect the hydrologic cycle will affect the availability of the water. To­pography is a factor. As the slope of the land increases, the rain falling on the land will flow laterally into streams more quickly and downstream more rapidly. The vegetation is an important factor since trees and plants intercept much rainfall directly as it falls and thus enable it to evaporate back to the atmosphere. Plants also transpire a large amount of water from the soil directly back to the atmosphere. Colman [9] discusses the importance of these factors. Factors such as temperature and soils, through their effects on vegetative development, are particularly important in determining the disposal of precipitation. The nature of the soil itself is important since the soil

absorbs and holds moisture and transports it vertically and laterally.

The geology of an area has a major effect on the water supply available. Glacial deposits may contain water-bearing gravels. Creviced limestone or porous sandstone formations may absorb and yield large quantities of water. Rain may soak directly into rock formations and move laterally through these formations to feed streams many miles away. In other cases the superficial materials may be so impervious that a large amount of the rainfall flows immediately into the stream and downstream causing the stream flow to be highly variable. Meinzer [33] discusses the geological aspects of water supply.

The physical factors discussed above are fairly well documented in the references given. These factors vary greatly and are major influences on the water supply of any particular area. The importance of these factors must be kept in mind throughout this investigation of weather elements and their effects on water supply. In any particular location, such factors will have to receive primary consideration.

3. Specific effects of weather on surface water

i. Records available.

(1) Precipitation. Records of precipitation and tem­perature in the United States are collected by the Weather Bureau. These are published each month in Climatological Data and include daily and hourly rainfall amounts from about 6500 stations in the United States of which some 300 are first order stations. The first order stations operate recording rainfall gages, make hourly observations of temper­ature, wind direction and speed, relative humidity, barometric pressure, sky conditions, and many other meteorological elements. The nonrecording stations with cooperative observers make daily observations of precipitation and temperature. Other publications of the Weather Bureau contain additional information.

Precipitation data in Canada are collected by the Canadian Meteorological Service. The government of practically every nation of the world maintains a weather agency. Most of these agencies collect precipitation and temperature data continuously.

Several general weather summaries are available. The U. S. Department of Agriculture [57] has summarized the climate of the United States. Tanne­hill presents weather data for the entire world and discusses these data by continents.

Precipitation data are frequently the most valuable (and sometimes the only) information available in many parts of the world for estimating the quantity of water which may be available for stream flow.

MAY 1957 ]. ABU-LUGHOD, W. ]. ROBERTS, AND]. B. STALL 73

Precipitation records are frequently 50 to 100 yr in length and can be utilized successfully in investigating the water resources of an area.

(2) Stream flow. Throughout the United States, the rate of flow is observed and recorded at selected points on rivers and streams by the Geological Survey (USGS). In the United States these records are the primary source of basic data for investigating the use of stream flow for water supply. In 1950, the USGS [58] was operating 6540 gaging stations. These stream gages are operated in cooperation with various sponsoring organizations, most of which are local or state agencies. The stream flow records are published annually.

(3) Groundwater. Information on groundwater avail­ability in the United States and Canada is collected by state or provincial, and by national agencies. The groundwater available in any particular region is closely connected to the local geological structure of the earth. Thomas [54] has summarized the ground­water situation in the United States. Meinzer [33] discusses in detail the occurrence and movement of water in the ground. Groundwater availability is too dependent on local physical conditions to be discussed even on a regional basis.

ii. Analytical methods of estimating water supply.

(1) Rainfall versus runoff. Runoff varies from more than 40 in. per yr in the humid parts of the eastern United States and in the Pacific Northwest to less than 1 in. per yr over broad areas of the arid inter­mountain region. Mountain ranges have an important effect on precipitation. Continental air movement in middle latitudes is generally eastward. Any mountain system lying in a north-south direction forces the air upward causing precipitation to fall in the higher regions. The precipitation increases with the altitude as the temperature decreases. This results in a cor­responding increase in runoff. Runoff from the melting snow in the vVestern States furnishes much of the stream flow for nearby arid regions. The Hydrology Handbook [3] discusses the general relationships of runoff to rainfall. Colman [9] also deals with this subject.

Fig. 2 illustrates the general rainfall-runoff relation­ship. In the upper part of fig. 2 is plotted the mean monthly rainfall at Fort Nelson, British Columbia. In the lower part of the figure is shown the mean monthly discharge of the Peace River at Peace River in second-feet per square mile of drainage area. This represents the runoff. It will be noted from the com­parison of these graphs that the major precipitation in this part of Canada occurs during the period 1 uly through September. A considerable portion of this

. •

4

~ 3 c

c -~ 2

Q.

:IE .;.

0

3

~ 2 • Q.

lL

..; "' "' ;: I 0 c

" a:

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Fort Nelson, B. C.

ONDJFMAMJJAS

Month of Water Year

Peace River,

Alberta

ONDJFMAMJJAS

Month of Water Year

FIG. 2. Comparison of mean monthly precipitation to mean monthly stream flow in Alberta and British Columbia, Canada.

precipitation probably occurs as snow in the mountains of the upper drainage basin of the Peace River. It thus does not appear as stream flow (shown in the lower portion of this figure) until the following May, 1 une or 1 uly when the spring melt occurs.

In the analysis of runoff data it is important to call attention to the time factor involved. The lower portion of fig. 2 shows the mean runoff from the drainage basin discussed. The stream flow varies from day to day much more than the block diagram for a particular month would indicate.

It should be noted from fig. 2 that the rainfall shown in the upper portion of the figure is given in inches. In the lower portion of the figure the runoff is given in second-feet per square mile of drainage area. The scales of these two figures are not com­parable, but the total runoff for the year amounts to 10.7 in. Since the total annual precipitation is 16.7 in., the annual runoff amounts to 64.1 per cent of the annual precipitation. This is an extraordinarily high proportion.

74 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

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.or 0.01 0.1 I 2 5 10 20 3040506070 80 90 95 98 99 99.9 99.99

Time in percent of total period

FrG. 3. Duration curves of monthly and annual flows of the Mississippi River at the outlet of Pokegama Reservoir, Minnesota in the Dfb climatic province. Drainage area of 3265 square miles [27].

(2) The duration curve. In examining the flow regime of the stream at a particular location to determine what quantity of flow may be available for use for a particular period of time the duration curve is found to be extremely useful. The duration curve shows graphicaily the variability of the stream flow.

A duration curve runoff is a plot of time versus the quantity of runoff in which runoff values are arrayed in order of magnitude. The horizontal axis indicates the percentage of time for a period of record during which the flow indicated was equalled or exceeded. The vertical axis shows the runoff. The concept of the duration curve has been discussed by Foster [17]. The duration curve has also been discussed recently by Hazen [23] and Mitchell [34].

In the duration curve the frequency of occurrence of the various flows, irrespective of chronological sequence, is the element of primary importance.

Such charts indicate the frequency of floods, drouths, and other characteristics of the flow. They show the frequency of occurrence of the various rates of flow throughout the entire range of flows at a given place. It is customary to use a logarithmic scale for flows and a normal probability scale for per cent of time in preparing duration curves.

Duration curves can be drawn for mean monthly flow, mean annual flow, or mean daily flow. It is important to note the time unit used in each curve. A flow duration study of the daily mean discharge is the most valuable and informative. Unfortunately this type of curve requires the most work to prepare. To prepare a flow duration curve for a given gaging station all the values of the flow are arranged in classes dependent upon magnitude. The proportion of time during which the flow was equal to or greater than the lower limit of each class is then determined.

MAY 1957 J. ABU-LUGHOD, W. ]. ROBERTS, AND]. B. STALL

NORTH AMERICA 0 200 400 000 .......a l bdbdbd

~- ...... ..oJICTIGOI

~IV

DRAINAGE BASINS INVESTIGATED IN KOPPEN CLIMATIC PROVINCES

l Chatinika River, Alaska 2. Peace River, Alberta, Canada 3. Mattigami and Groundhog Rivers,

Ontario, Canada 4. Mississippi · River, Minnesota 5. Kings River, California 6. Cedar River, Iowa 7. Spoon River, Illinois 8. Pecatonica River, Illinois 9. Lodge Creek, Montano 10. Moreau River, South Dakota 11. Salt River, Arizona 12. Gila River, Arizona

-. ~. IILOOMIN$TOM. IWMOIS 13. Milk River, Montana 14. Sacramento River, California

FIG. 4. Location of drainage basins investigated in various Koppen climatic provinces in North America.

75

76 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

For example a stream that often goes dry for a day or two at a time might have a duration curve of mean daily flow that would drop to zero at, say, the 90 per cent time point, whereas its duration curve of mean monthly flow might never fall to zero. The duration curve of mean annual flow of the same stream might show a flow considerably higher than zero for 90 per cent of the years of record.

The two curves shown in fig. 3 and referred to later in the text under Dfb climate are duration curves of monthly and annual flows. The duration curve does not show the sequence of events. Low flows might occur on isolated days throughout the year or during periods of a week at a time, or the entire period of deficient flow might occur at one season of the year. The utility of the duration curve has been greatly increased by the recent study of :\1itchell [34] who devised a method for the transposition of duration data from one stream where the data are available to another stream for which information is desired. iii. Stream flow in various climatic provinces. In fig. 4 is shown a location map delineating the various climatic provinces in North America and showing the points at which stream discharge or precipitation data have been studied for a special report.* Friedrich [18] has prepared an extensive bibliography containing articles dealing with stream flow analysis in various parts of the world. For the original report from which this discussion is taken, stream flow and precipitation data were studied and reported on for all pertinent climatic provinces. Graphic examples are included here only for Dfc climate.

(1) Dfc climate [7, 8, 60]. Stream flow records were investigated at three general locations in Dfc province as shown in fig. 4.

Fig. 5 shows the mean monthly discharge of the Chatinika River below Poker Creek, Central Alaska. The block diagram shows that this particular stream is highly variable in its monthly discharge. The high proportion of the annual flow takes place during the month of May. This is undoubtedly due to the snow melt in the watershed and falling ice in the flood plains. The flow is fairly well stabilized through September and becomes almost nonexistent during the winter months.

A long-time stream flow record was studied for the Peace River located in Central Alberta. This stream has a drainage area of 72,000 sq mi. Even at this location, considerably farther south than the Chatini­ka, the monthly stream flow regime still exhibits considerable variation. Fig. 2 showed the principal

* Climatic criteria defining efficiency limits for certain industrial activities. Contract No. AF 19(604)-416. This report gives analy­ses of stream flow in all of the drainage basins indicated on fig. 4.

4 ,.......

3

·-:a cT VI .. 2 ., CL

...:

..... .. .. (/)

0

-

0 0 N D J F M A M J J A s

>-

c- 1:1 :::0 ... .. .. 0 0 ... .., ~ ...

"!~~ .. ~-o U) U) Ill C» ·::;

0 .. N - 0 0 0 ..... ]I ...

0

.....

FrG. 5. Mean monthly discharge of the Chatinika River near Fairbanks, Alaska, in the Dfc climatic province. Drainage area of 456 square miles [16].

part of the annual runoff occurs during May, June, and July. This is undoubtedly attributable to snow melt. On a stream such as this, water supplies might be safely developed without impoundment to utilize nearly 0.2 sec ft per sq mi. In the southeastern portion of the Dfc climatic province is the stream basin of the Mattigami River. This river is gaged at Smoky Falls in Ontario and has a drainage basin of 15,400 sq mi. A tributary of the Mattigami River is also gaged in this area, the Ground Hog River at Fauquier. This tributary has a drainage basin of 4,610 sq mi. The stream flow is highest during the months of April, May, and June, the snow-melt months of the year. The mean annual flow, however, is somewhat higher on this basin than on the two Dfc climate basins discussed previously. The flow during the other months of the year are more nearly equal.

(2) Dfb climate [22, 26]. In the Dfb province, a SO yr stream flow record is available on the Mississippi

MAY 1957 J. ABU-LUGHOD, W. J. ROBERTS, AND J. B. STALL 77

River at the outlet of Pokegama Reservoir. Fig. 3 contains duration curves of mean monthly flow and mean annual flow of the Mississippi River at this location. The mean monthly discharge is fairly well stabilized, not highly variable. Such a stream might easily be used as a source of industrial water supply. The uniformity of flow is desirable. It should be noted that this drainage basin, having a total area of 3265 sq mi contains several large lakes. This is typical of the Dfb climate and wherever such a climate might occur the natural lakes would tend to stabilize this stream flow making it more desirable for a ·water supply.

(3) Dwc, Dwb, and Dwa climates. These climates do not occur in North America, but are characteristic of Asia. Temperatures are similar to the Dfc, Dfb, and Dfa provinces already discussed. The chief difference pertinent to water supply is that precipitation occurs mainly during June to September, when most of the water flows downstream and away. The basic seasonal variability in precipitation and the probable rapid runoff of the summer rains would make industrial water supply problems more difficult than in the Df climates.

(4) ET climate. In the ET province, water supply problems are usually difficult because of the extreme cold. The general regime of stream flow may be some­what similar to that of the Chatinika River in central Alaska as shown in fig. 5. The variation in monthly stream flow is likely to be more severe however. In this province streams are likely to be frozen for the greater part of the year. The general methods of stream flow analysis in this province would be similar to that of the other provinces described above where stream flow data are available.

The securing of large amounts of water in the ET province, largely covered by permafrost, presents a major problem. Small amounts of water can be obtained generally from melted ice and snow. In the permafrost area, rivers which can be used as source of water supply are not very numerous. During the winter most rivers freeze to the bottom except where the channel is deep and in these deep places water may become stagnant and unfit for use. Only the larger rivers and lakes furnish water throughout the year.

4. Reservoir design

The dependable steady flow of water which is available from a particular stream at a particular place can be greatly augmented by the use of a storage reservoir. This reservoir stores the waters of the flowing stream during periods of high flow for use

during periods of low flow. In analyzing the stream flow data at a particular place regarding reservoir storage the mass curve is particularly valuable. In this curve the horizontal scale represents units of time and the vertical scale represents the total volume of flow that has passed a particular point since zero time. Fig. 6 shows a mass curve of a typical stream. In this particular case the time unit along the hori­zontal scale is the month and the volume unit along the vertical scale is the second-foot day. One second­foot day is equal to a flow of one cubic foot per second for a day. The slope of the curve in fig. 6 represents the rate of change of volume with respect to time and is thus the rate of flow. With proper con­version of units, the slope of the curve can thus be expressed as cubic feet per second or as million gallons per day (mgd). The sloping lines in the lower right hand portion of fig. 6 show rates of 50, 30, and 10 mgd.

The slope of a line joining any two points on the curve in fig. 6 represents the uniform rate of discharge that would have yielded the same total volume during that period. It is this property of the mass curve which is of special value in studying the possibility of constructing a reservoir. In fig. 6 a straight line has been drawn tangent to the nodes of the curve at 30 May 1933 and 31 October 1936. This line is found to have a slope corresponding to 50 mgd. If a reservoir of adequate capacity had been available at this point and the reservoir had been full on 30 May 1933, discharge could have been maintained at a uniform rate of 50 mgd throughout the period and the reservoir would once again have been full on 31 October 1936. At any time during the intervening period the length

. ... .. 0

;: u 200 ~--4----+----+-~~~~+----+--~ . "' 0 0 2 I . ~ .. ~ 100 1----+----++--+----+---:c. ·~o:._-+---l 0

_; 0 :; E " u

1930 1931 1932 1933 1934 1935 1936

Ytor

FrG. 6. Mass curve of stream flow utilized in determining reservoir storag-e capacity necessary to furnish a particular water demand in million gallons per day.

78 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

of ordinate between the straight line and the mass curve measures directly the draft on the reservoir. That is, the amount which would have been taken out of the reservoir up to that particular time. The maximum value of such ordinate then measures the total volume of storage that would have been neces­sary in the reservoir to maintain the flow at SO mgd throughout the period. In fig. 6 this maximum amount can be scaled as 32,000 sec-ft days. This amount of water would fill a reservoir having a surface area of two square miles and an average depth of SO ft.

It should be noted that the rates of usage plotted in fig. 6 do not consider evaporation. As soon as the actual reservoir water surface area is known, a fair estimate can be made of evaporation losses and the storage capacity available as determined from fig. 6 can be reduced accordingly. This correction will often be appreciable, particularly when the draft on the reservoir continues over long periods of time. For example assuming two square miles of surface area at an average annual rate of evaporation of three feet per year, the dependable rates on 32,000 sec-ft days of storage would be reduced from SO to about 47 mgd.

A further factor that reduces the available reservoir storage capacity is the fact that after the reservoir is constructed the stream will carry silt into the lake which will deposit. In the construction of a reservoir in practically any part of the world it is necessary to consider the silt factor. Usually the reservoir is con­structed with increased capacity by an amount de­termined to be economically feasible. This excess storage capacity is allotted to hold silt which will be carried into the reservoir.

The quantity of silt carried into the reservoir will be highest under conditions of steep slopes on a watershed which has very little vegetation. Water­sheds which are well covered by forest or grass will normally carry only a nominal silt load. Several major reservoirs in the United States are losing capacity at a rate of 1 per cent per year. Some smaller lakes are losing up to 5 per cent of their original capacity per year and a large number of lakes lose 0.5 per cent of capacity per year or less.

Where the silt load of a particular stream is high this factor is usually documented in the literature and any source of extensive data on stream flows and the character of the stream will probably comment on the silt load carried by that stream.

5. Water quality

Some specific information is available on the quality of surface waters. Thomas [55] has reported the general quality of the surface waters of Canada.

Moore [35] has reported on the quality of surface waters of Alaska. The surface waters of northern and central Alaska are fairly uniform in mineral analysis and apparently can be treated by standard coagula­tion, filtration, and chlorination methods. The waters of southern Alaska are similar to those of eastern United States and require no special treatment.

Climatic provinces in which the rainfall is con­siderable and dependable generally yield waters of better quality than those in which rainfall is slight, for the existence of the larger rainfall over a long period causes a leaching of minerals from the soils and underground materials so that the more soluble portions are removed, and the waters discharging into the streams are less likely to contain mineral matter than the waters from arid regions, where less opportunity for leaching of water soluble materials exists.

The water quality also depends on geologic and other forces that may have caused or prevented the occurrence of water soluble materials in the area involved. Water yielded from predominantly lime­stone country is apt to be hard, while water yielded from areas covered and underlain by less soluble materials is apt to be softer.

6. Development, distribution, and handling of water

The physical problems of development and distribu­tion of water are closely associated with climate. The methods current throughout much of the United States are suited to temperate zones. For purposes of this report it is assumed that they are fairly widely understood, and little space is devoted to them. Information on development and distribution prob­lems is gained from public water supply and industrial supply experiences, since the principles involved in either are similar.

Both areas of extreme cold and areas of hot dry climate are likely to be areas of water shortage. Area of water shortage is here defined in a comparative sense; that is, either an area in which exploitation of water resources is more difficult and costly than in most other areas, or an area in which exploitation of water resources is more difficult or costly than use of substitutive resources or techniques. Water is always thought of in terms of both quality and quantity, so that the availability of a large volume of water of unsuitable quality may constitute, in fact, a water shortage.

Because adequate supplies of water of desired quality may be difficult to obtain and because a distribution system for such water may present technical difficulties in both extreme hot dry and in

MAY 1957 J. ABU-LUGHOD, W. J. ROBERTS, AND J. B. STALL 79

extreme cold climates, industrial installations of cer­tain types may not be economically feasible in these areas and other industrial installations may have to modify their technological processes to minimize water requirements. Industrial plants in both types of areas require water conservation measures. How­ever, the particular solutions to the conservation problem are different in the two extreme cases.

There is no such thing as a complete absence of water. Water can be obtained in or transported to any area of the world if it is needed. Water of any quality may be treated to obtain the desired charac­teristics. Ocean water may be desalted, snow and ice may be melted, and hard water may be made soft. But, in the last analysis, this is not the basic problem. Water has extensive use in industry, not only in processes for which it is indispensable, but in many other processes for which substitutes are available. Water is used in such processes because it is the least expensive material. Where supply, distribution, and treatment raise the cost of water beyond the cost of alternatives, the use of water in the industrial process may be uneconomical. ·Hence, the basic problem is one of efficient allocation of resources, of which water is but one.

i. General problems with ground water. Ground water gains heat from the center of the earth and from solar radiation. It loses heat through radiation of heat to the atmosphere and through evaporation. Ground water from depths in excess of a few hundred feet is generally considerably warmer than ground water at depths of 20 to 50 ft, for at the greater depths the gradient is caused by the heat loss from the center of the earth. The gradient in the outermost segment of the earth's crust varies seasonally, depending on local weather conditions and particularly on the air temperature. As a rough approximation ground water temperatures in the shallower formations may be estimated by using the annual air temperature, and the rule that temperatures in the deeper zone fre­quently increase 1F for 100 ft of depth.

Ground water in the upper 10 to 20 ft responds much more readily to seasonal changes in air tem­perature than does water at 50 ft where it is apt to vary only a few degrees throughout the year. Water at great depths is virtually constant in temperature.

Ground water obtained from formations adjacent to streams from which recharge is induced by pump­ing varies to a greater extent with the seasonal temperature than ground water in formations that are replenished by precipitation and subsequent infiltration.

The quality of ground water is strictly a function of the amount of water that moves through the

underground formations and the nature of the forma­tions. It is therefore primarily a local matter and cannot be generalized. ii. Water problems in extreme climates. (1) Hot, dry climates (Bw). The major sources of water supply in hot, dry areas are ground water, surface water from streams, rivers, and lakes (fresh water), and surface supplies of salt water from the oceans or salt lakes. For most industrial operations, the ideal source of fresh water in this climatic region would be ground water. Since the chief industrial use of water is for cooling purposes, uniform temperature throughout the year is to be desired. In addition, ground water, although it may require treatment to remove hardness or other mineral content, is generally of uniform quality and unpolluted. However, hot, dry climates are associated generally with low-production wells, thus the amount of water available from this source in most locations is severely limited.

Although ground water supplies in hot, dry climates may be meager, recharge of ground water through artificial means may be employed to insure a source water of uniform temperature. "The development of facilities for water reclamation from sewage, wherever possible, and the return of reclaimed water through such spreading ground to underground reservoirs would furnish an additional year-round supply of valuable water to the depleted underground basins" [42]. The possibility of such disposal of industrial wastes as well as ordinary sewage might prove a partial solution to inadequate ground water supplies.

Streams, 'lakes, and rivers constitute the second source of water supply. These sources, too, present difficulties in hot dry climates. Not only are such surface sources infrequent, but they are often in­adequate for a year round supply. Due to the high rate of evaporation in such areas, a lake may lose large quantities of water during certain periods when the rate of evaporation exceeds the rate of rainfall, and streams and even rivers may be subject to seasonal drying-up. Construction of artificial lakes by the damming of streams or rivers to store water during the dry seasons may be essential to insure year round supply. Because of the variability of water supply due to spasmodic rainfall and to evapor­ation, Weaver advises that " ... the chance of a supply from surface streams is good where the rainfall is more than 40 in. but it is generally unpromising elsewhere, especially where the rainfall is less than 30 in." [67]. Exceptions will be found to this rule, but it indicates likelihood of success. A strong adverse factor is that, in the hot dry climate, potential evapotranspiration from land surfaces is often greater than actual water losses, a condition that may result

80 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

in a rise in the rate of transpiration with an increase in the amount of water available. C. W. Thornthwaite has calculated the actual and potential evapo­transpiration rates during the summer months in selected areas of the United States with hot dry climates [56].

A second major problem encountered in the use of fresh-water surface supplies is the initially elevated temperature of the water during the hottest months. Where water is used for cooling, this elevated tem­perature may considerably decrease the efficiency of the operation, and may even preclude the use of such water without prior refrigeration. Powell gives figures on the summer temperatures of municipal water supplies in various cities using surface water. In New Orleans, for example, during August and September the temperature of the water is 90F [44]. In hot arid climates, even greater elevations in temperature might be expected. According to Salzman and Elliott, initial temperature elevations of from 5 to 10F may cause a reduction in the efficiency of a steam power plant of 1 to 1.5 per cent [47]. Elevated water tem­peratures may also create technical difficulties in electroplating. During the summer months, Lake Michigan water (60 to 70F) is too warm for the needs of one firm, which employs a water chilling system to maintain certain bath temperature levels for electro­plating during these months [24].

The third major source of water in the hot dry climates is ocean water. In some industrial operations, this water may be used on a once through basis for cooling purposes. Several examples of power plants which utilize untreated sea water for cooling will be given below; The advantages of this method can be appreciated more when one considers that nearly all of the water required in steam power generation is used for cooling purposes. However, using untreated salt water for cooling, even on a once through basis, increases maintenance or equipment costs because of the corrosive action of such water on the circulating surfaces.

Another possibility is the use of a sea water supply for cooling recirculated fresh water. "The fresh water may thus be 'bottled up' in a closed system. Savings can be effected by reducing the size of the treatment plant for conditioning a fresh water supply and utilizing sea water for all cooling services" [44].

Another possibility is the distillation of fresh water from sea water sources. This is technologically possible but, except for boiler feed water, has usually been uneconomic thus far [42, 53, 64]. (2) Extremely cold climates (ET, EF). Possible sources of water in extremely cold climatic regions are ground water, surface water from fresh streams,

rivers, and lakes, ocean water, and water secured by melting snow or ice. Each of these sources presents unique problems in supply; all of these sources present a common problem in transportation and distribu­tion. The latter is often most difficult.

During the warmer months of the year, securing adequate water may not be difficult due to the presence of many flowing streams and rivers as well as large fresh-water lakes. Water of low temperature and good quality is often available in large enough quantities to permit simple once through usage by industrial establishments, although the waters may require treatment since they may sometimes have high mineral content. They are generally clear and unpolluted.

Quite the opposite is the case during the winter months when streams and rivers may freeze solid and lakes may have surface ice coatings up to 20 ft in depth. However, these ice coated lakes may provide year round water supplies if the intake is located at a sufficient depth. This often necessitates expensive construction cut through frozen materials, since the permafrost in many arctic regions exists from a few feet to hundreds of feet below surface. A hydroelectric power plant for Anchorage, Alaska, for example, obtains its water supply from a frozen-over lake. A tunnel was sunk 206 ft below ground to carry lake water down from a storage area to a power plant near tidewater. Water is tapped at a level below operating storage level. "The intake structure is to be placed entirely under the lake surface, thus providing a free access for the water under thick ice formed in the winter (where temperatures may drop as low as -60F)" [16].

The most dependable source of ground water is generally found below the permafrost. Under favorable conditions such wells may have large yields of water suitable for human consumption. The water may be comparatively warm because of its depth below the surface, but this initial warmth may help prevent freezing in the supply system. Aquifers which may have considerable thickness may be found below the permafrost as alluvial deposits in broad river valleys; centers of structural depressions sometimes provide bedrock aquifers providing the wells are drilled deep enough to tap the water bearing strata below the permafrost; wells sent through fissures produced by weathering may collect sufficient water especially if they intercept fault zones, dykes, intrusions or stratigraphic contacts; limestone and dolomite provide water bearing channels which may occur below the permafrost. Information on the mineral quality of deep well waters in the ET zone is extremely limited. In general, mineral quality worsens with depth, but

MAY 1957 ]. ABU-LUGHOD, W . ]. ROBERTS, AND]. B . STALL 81

CLOUDS

'1-'-r'-r'-r PRECIPITATION

IMPERVIOUS SURFACE. GROUND FORCES WATER TO PERCOLATE THROUGH THE UNFROZEN PART ( TALIN) IN PERMAFROST

FIG. 7. Occurrence of ground water in the permafrost region.

there are conspicuous exceptions to this. Fig. 7 illustrates ground water occurrence in permafrost areas.

Black [6] gives a concise discussion of permafrost problems including water supply. Muller [36] pre­sents perhaps the most complete and up-to-date discussion of water supply problems in permafrost regions.

Sea water, as a potential source of supply, presents similar possibilities and difficulties as those experienced in the hot dry climate regions, with the exception that distillation may be even less feasible because of the large quantities of energy required [62]. That such a source is usable is attested by the fact that the U. S. Air Force Base at Thule, Greenland, ob­tained 50 per cent of its water supply from the distillation of salt water. Three distilling plants had a daily capacity of 130,000 gal. That such a source is currently uneconomic is attested by the fact that, as soon as a surface water system for transporting fresh water six miles to the base was completed, the distilling

units were maintained only for standby emergency use [50].

Although melted ice and snow is utilized for domestic purposes in arctic and subarctic regions, it remains to this time an uneconomical source of water for industrial purposes [10]. Water cannot economically be transported any great distance and snow melting machines are expensive to operate and yield only small quantities of wa ter for large quantities of precious fuel oil consumed.

Alter cites evidence on the high cost of water from the melting of ice. "The cost of one hundred gallons of water brought as ice from a distance of 2 to 25 mi is about $7.25 according to estimates made in 1947 for the village of Barrow, Alaska" [2].

Often outweighing the problems of supply, however, are the problems of distribution in extremely cold climates [40]. In cold climates where no permafrost exists, water distribution pipes are buried in the earth below the frost line, the location of which varies with the air temperature and its duration, the charac-

82 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

ter of the soil, the amount of moisture in the soil, the density, texture, and color of the soil. Additional meteorological factors such as wind velocity and the amount of sunshine and clouds also affect the frost line somewhat [41].

Where permafrost conditions exist, however, the most feasible solution may be the installation of an above-surface distribution system where the pipes are well insulated. At Flin Flon, Manitoba, water from a clear lake is pumped to a reservoir through an above-ground pipe system. Boiler houses are located strategically along the pipe system ready to inject steam if the pipe is in danger of freezing. Steam is injected into the water mains to maintain temperature, and service lines provide for small constant flow to prevent freezing. When the pipes run underground, they are encased in a wooden box filled with cinders; above-ground pipes are insulated with wood shavings [45].

Another installation, described by Cronkwright in his article, Water Supply Problems of Arctic, utilizes surface distribution mains encased in well insulated boxes supplied with heat. This installation proved effective in a subarctic area where temperatures of -40 to -SOF were recorded continuously for a month. A reservoir was impounded by placing a small dam across the conveniently located stream. The distributing system consisted of some 2500 ft of pipe of which only 750 ft was enclosed in structures. To protect the pipe from freezing, it was encased in a wooden box packed with Kimsul. This box also con­tained a three-inch steam line and a one-inch return line. When the outside temperature was -41F, and the temperature of the water at the treatment plant was only 32 to 33F, water was preheated and circu­lated through the system at a temperature of 120F.

Considerable advice has been given on how to maintain a water distribution system in the face of low temperatures. The main points may be sum­marized as follows :

1. Withdraw "warm" water from the reservoir or lake supply. Riddick states that water at 39F may be obtained from the bottom of a frozen­over lake and water at 37F may be obtained from the middle of such a lake [46].

2. Provide for continuous flow at a high velocity. For example, water travelling at 4.25 ft per sec does not freeze in a bare pipe at 32F [45].

3. Enlarge pipe diameter and minimize pipe length. If temperature falls below 32F, water freezes no matter what the velocity if the line is long and the diameter small [45].

4. Avoid dead ends in water pipe grid [64].

5. Blow off water to waste at the end of the line, or recirculate it back to the point of origin for reheating to decrease the detention period [46].

6. Use adequate insulation. 7. Thaw by electrical heating or by steam

injections.

Storage tanks in cold weather climates also present difficulties. Some of these problems are discussed by Holden. Complete enclosure of storage tanks together with a heating stove is advised for cold climates. "In northern climates it is not good practice to rivet any accessory ... to the inside of the tank, as falling ice may tear out rivets. Smaller diameter tanks are also usually equipped with radial grids inside the tank to prevent damage by ice .... Fully overcoating all steel tubs under 50.000 gal with insulated housing ... " is also recommended. Tanks with larger capacity need only frost casing. Holden also mentions that '' ... some progress has been made in frost protection by mineral insulations applied directly to the steel tub" [25].

Thus it can be seen that extreme cold and perma­nently frozen ground present several obstacles to the development of water systems adequate to support extensive industrial developments in the tundra areas of the northern hemisphere. However, from a techno­logical standpoint there are no absolute barriers to development of such systems.

The development of quantities of water of the order of 1 mgd or more for an industrial establishment within the ET climate zone appears to be limited either to the use of sea water, to stream flow in large rivers that do not freeze solid, or to deep ground water developments below the permafrost. It would there­fore appear that the only probable locations for industrial extablishments in the ET climate zone at which sufficient water could be obtained for operation would be along the major rivers.

(3) Cold winter climates (D). North American munic­ipal water systems are not limited greatly by the climate within this region [52]. Distribution systems have to be guarded against frost penetration which varies throughout the climatic province. At Calgary, Alberta, water mains laid in gravel must be buried to a depth of 12 ft. If they are in loam, 8 ft of cover will suffice. At Ottawa water pipes laid under streets with heavy traffic must be 6 ft deep to resist frost action. At Leadville, Colorado, water pipes are buried 9 ft, but in New York City under asphalt on concrete base they need to be only 3t ft under the surface. Further southward the necessary depth decreases to 2t ft at Bluefield, West Virginia.

Surface water reservoirs undergo changes of tern-

MAY 1957 J. ABU-LUGHOD, W. J. ROBERTS, AND J. B. STALL 83

perature which are an important consideration for industry. Water intakes have to be spaced so that surface ice will not be thick enough to clog intake ports. Generally all problems caused by icing may be temporarily overcome by reversing the flow or apply­ing steam, though great quantities of heat are required.

There is no particular problem connected with the pumpage of ground water in the Db climate that cannot be overcome by conservative design. Where suitable water yields occur, cold water (45 to SSF) may be obtained from depths of 100 to 300 ft over a large part of this area.

Underlying the glacial deposits are gently sloping or horizontally laid sedimentary rocks which supply vast quantities of water for industry. For example, wells in the Chicago region pump approximately 85 mgd from wells varying in depth to a maximum of 2000 ft.

The same sedimentary aquifers that provide this water for the Chicago region yield highly mineralized water SO mi to the south. Also the temperature tends to rise in the water as the gently sloping sediments are followed southward.

Development of adequate surface supplies depends to a large extent upon topography. Throughout the Dfb and Dfa climatic zones in the North American continent there are numerous natural reservoirs and artificial impoundments.

Churchill, Manitoba on the western shore of Hudson Bay at latitude 58 deg 45 min N has a water supply obtained from a reservoir in the 2.5 mi water reserva­tion that contains a group of small lakes about 2 mi SE of the settlement. Each of these lakes is 6 to 8 ft deep with about 40 ft of unfrozen material between the lake bottom and the permafrost. It was necessary to build a reservoir large enough to store an adequate supply of water under the ice for use during the winter months as lakes of such depths frequently freeze completely in wintertime.

iii. Distribution systems in permafrost. Preheated water may be distributed in pipes lying in the permafrost or, if covered with a mound of insulation, on the ground surface. The recommended depth of a pipe below the surface is 7 to 9 ft; a recommended cover, if the pipe is laid on the ground surface, is 9 ft. The cushion of sand, with width and depth at least three times the pipe diameter, should surround the pipe. Adequate drainage must be provided. Moss or peat insulation 18 to 24 in. thick is placed over the sand and covered with excavated material. Under certain combinations and sequences of weather this method has serious disadvantages. If freezing and thawing of the ground around the pipe takes place, water may

freeze in the pipe or the pipe may move enough to cause breaks at the joints.

Steam heated utilidors have provided the most satisfactory method for protecting water and sewer lines from the elements at many arctic and subarctic locations.

Available evidence indicates that water can be extracted from the ground below the permafrost in the Dfc climatic area and that it can be transported through a distribution system provided sufficient heat is added to the water to prevent it from freezing.

7. Estimating available water for areas with meager data

The present section is designed to enable estimation of the amount of water available from streams for industrial establishments in areas on which quantitive data are lacking. If the streams do not carry the necessary amount of water for a given industrial esta­blishment, there is little likelihood that an enduring industrial establishment could be founded on develop­ment of ground water in the same area. Adequacy of ground water supplies is generally considerably less than that of surface supplies in a particular area. If the computations of available stream flow indicate the possibility of development of substantial sources, then there is a parallel possibility that ground water sources may be present in the same region that would furnish requirements for industrial establishments needing smaller amounts of water than those estimated for stream flow. i. Unit stream flow data. Table 2 summarizes approxi­mate values of stream flow that may be expected to be exceeded 90, SO, and 10 per cent of the time, respectively, for various climatic provinces and for the case in which water originates in a Dfb climatic province and discharges through a BS climatic province. The figures given in this table are approxi­mate and need to be adjusted for the local conditions. They are satisfactory in their present condition for

TABLE 2. Probable stream flow extremes in various climatic provinces

Climate

ET Dfc Dwc and Dwd Dfb Dwb Dfa Dfb-BS BSw

Flow values in sec-ft per sq in.

90

0.00 0.4 0.3 0.1 0.05

Flow exceeded during stated percentages of time

50

0.5 0.7-1.1 0.7-1.1

0.5 0.5

0.03-0.2 0.4 O.ol 0.1 0.00 0.05

10

3-4 4 1.0 1.5 1.5 0.3 0.4

84 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

.. :::E .. ~

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Q= 1.547336 0 A, or A=0.646272 § 1.0

.7

.5 100,000

.4

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10,000

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.I c: 0 -- 1,000

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.04 :::E 100

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~- .. =-10-- 0'

-:01 _______ <l " ::

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FrG. 8. Nomograph for solution of problem involving unit dis­charge of stream (left), water demand (center), and drainage area (right).

rough estimating purposes, but more detailed allow­ances in light of the local geology, vegetation, pre­cipitation, and evaporation data ought to be made before applying values like these for precise estimates. As discussed in earlier sections, within any given climatic province there is considerable variation in the hydrologic conditions.

In using the values from table 2, it is intended that the values in the 90 per cent column may be used for estimating the safe yield of a stream without major storage construction.

When it is found necessary to consider the possibility of large impounding structures, a value higher than the 90 per cent value, but not in excess of the SO per cent value should be chosen as the amount which might reasonably be developed through the use of storage.

ii. Estimating yield for specific watershed. For the final determination of flow available, it is necessary to study maps of the area to estimate the watershed area of the streams that may be considered as sources of supply. Examination of the maps and of other sources for information such as foundation conditions, suitable

topography, etc., is desirable for the location of impounding reservoir sites if they are required.

The sections on industrial water requirements yield data on water needs in gallons. Stream flow data are expressed in second-feet per square mile.

For making this conversion, and for computing yields, the nomograph shown in fig. 8 has been prepared. The center column of this chart contains the quantity of water needed in million gallons per day (mgd). The left hand scale of this chart contains the unit discharge from a particular drainage area in second-feet per square mile and the right hand scale of this chart contains the drainage area in square miles. By knowledge of any two of these factors it is possible to lay a straight edge across the nomograph and read directly the value of the unknown item from the third scale. The example illustrated by the dashed line shows that a drainage area of 646 sq mi can supply a quantity of water of 10 mgd if the unit discharge amounts to 0.01 sec-ft per sq mi. Any straight line intersecting these three scales represents a solution to a conversion problem.

By the use of fig. 8 it is possible to estimate the water available at a particular location by knowing the unit discharge available for a particular period and the watershed area of the stream under study .

8. Bibliography on water resources in cold regions

1. Alekseyev, N. N., 1939: Gidrologicheskiye raboty v arktike v III pyatiletti (Hydrological work in the Arctic during the third five-year plan). Prob. Ark. No. 10/11, 102-04.

2. Alter, A.]., 1950: Water Supply in Alaska. J. Amer. Water Works Assoc., 42, 519-32.

3. Gomoyunov, K. A., 1945: Gidrologicheskiye issledovaniya v sovetskoy arktike za 25 let (1920-45) (Hydrological studies in the Soviet Arctic during 25 years (1920-45)). Izv. Vse. Geog. Ob., 77, no. 6, 328-40. (Contains selected list of works published on this subject. English summary of this paper appears in Polar Record, 5, no. 37/38, 355-60, 1949.)

4. Handbook of Siberia and Arctic Russia, 1918: London, Ad­miralty-Intelligence Department. 3 Vols. (Reference to Vol. 2, p. 87).

5. Hydrogeologic conditions of water supply in the areas of frozen zone of the lithosphere (permafrost), 1936: Tr. 1-oi Geol-Razv. Knof. Glavsevmorputi, Geology and Mineral Deposits of the North of the USSR. Vol. 3 (Permafrost), 102-127 (In Russian.)

6. Hyland, W. L. and G. M. Reece, 1951: Water supplies for army bases in Alaska. J. New England Water Works Assoc., 65, no. 1, 1-16.

7. Kornilov, 1., 1937: Vodnyye puti Yakutskogo severa (Water­ways of the Yakutsk north). Sov. Ark. No. 7, 50-53.

8. Korovkin, I. P., 1940: Materialy po gidrologii reki Khatangi (Material on the Hydrology of the river Khatanga). Sev. Mar. Put', No. 16, 39-98.

9. Kublistskiy, G., 1949: YeniseyReka Sibirskaya (The Yenisey is a Siberian river). Moscow, Leningrad, Gosudarstvennoye

MAY 1957 J. ABU-LUGHOD, W. J. ROBERTS, AND J. B. STALL 85

lzdatel' stov Detskoy Literatury Ministerstva Prosvesh­cheniya RSFSR, 288 pp. (Reference pp. 281-84).

10. Kurenkov, A., 1940: Reka Indigirka i yeye osvoyeniye (The river lndigirka and the conquest of it). Sov. Ark. No. 7, 36-38.

11. Laktionov, A. F., 1939: Zadachi ledovykh i gidrologicheskikh issledovaniy v arktike (The tasks of ice and hydrological studies in the Arctic). Prob. Ark. No. 6, 5-10.

12. Lationov, A. F., 1935: Nauchnyye resul'taty arkitcheskoy ekspeditsii na Lomonosove v 1931 godu. Gidrologiya i meteorologiya (Scientific results of the arctic expedition in the Lomonosov in 1931. Hydrology and Meteorology). Trudy Ark. Inst., 18, 1-107.

13. L'Vov, A. V., 1916: Poiski i Ispytaniia Vodoistochnikov Vodosnabzheniiz na Zapadnoi Chasti Amurskoi Zhel. Dorogi (Prospecting for and testing of sources of water supply along the western part of the Amur Railroad). Irkutsk, 881 pp. (In Russian.)

14. Mineral water of the frozen zone of the lithosphere, 1938: Tr. Kom. po Iz. Vech. Merzloty, Acad. Sci., USSR., 6, 63-78. (In Russian with summary in English.)

15. Rose, Edwin, 1947: Thrust exerted by expanding ice sheet. Trans. Amer. Soc. Civil Engineers, 112, p. 871.

16. Svetozarov, 1., 1934: The hydrogeology of permafrost regions, based on investigation in the area of the town Yakutsk. Probl. Sov. Geol. No. 10, 119-132. (In Russian with sum­mary in English.)

17. Tolstikhin, N. I., 1932: Ground water of Trans-Baikalia and their hydrolaccoliths. Tr. Kom. po Iz. Vech. Merzloty, A cad. Sci. USSR., 1, 29-50. (In Russian.)

18. Underground water in Quaternary deposits in regions of ever­frozen ground, 1933: Tr. II Int. Conf. Assoc. Study Quater. Period of Europe, 2, 56-72. (In English.)

REFERENCES

1. Agnon, S. and C. Y. Young, 1952: Cooling of water below wet-bulb temperature of ambient air by cooling tower. Heating, Piping and Air-Conditioning, 24, no. 10, 139-142.

2. Alter, A. J., 1950: Water supply in Alaska. J. Amer. Water Works Assoc., 42, 519-532.

3. American Society of Civil Engineers, 1949: Hydrology Hand­book. New York. Amer. Soc. of Civil Engineers, 184 pp.

4. A.S.T.M. Manual on Industrial Water, 1953: Philadelphia. Amer. Soc. Testing Materials, 326 pp.

5. Beard, L. R., 1953: Statistical analysis in hydrology. Trans. A mer. Soc. of Civil Engineers, 108, p. 1110.

6. Black, R. F., 1950: Permafrost. Applied Sedimentation, P. D. Trask, ed. John Wiley, 247-275.

7. Canada. Dominion Water Power and Hydrometric Bur., 1936: Surface water supply of Canada, arctic and western Hudson Bay drainage, climatic years 1929-1930 and 1930-1931. Water Resources Paper No. 68, 277 pp.

8. Canada. Dept. of Resources and Development, Water Re­sources Div., 1950: Surface water supply of Canada, St. Lawrence and southern Hudson Bay drainage-Ottawa and Quebec, climatic years 1945-1946 and 1946-1947. Water Resources Paper No. 99, 385 pp.

9. Colman, E. A., 1953: Vegetation in Watershed Management. New York, Ronald Press, 400 pp.

10. Cronkwright, A. B., 1947: Water supply problem of arctic. Public Works, 78, no. 8, 18-20.

11. Degler, H. E., 1950: Evaporative cooling-potent weapon for water conservation. Power, 94, 112-113.

12. --, 1951: Selection and operation of water-cooling towers and air-cooled heat exchangers. Petroleum Refiner, 30, 145-150.

13. --, 1951: Selection, operation, maintenance of industrial cooling equipment. Trans. Amer. Soc. Mech. Engineers, 73, 1031-1036.

14. --, 1949: Winter operation of water cooling towers. Diesel Power, 27, 46-47.

15. Farmer, A. E., 1952: Why and how of England's new cooling towers. Power, 96, no. 7, 94-95.

16. Felkner, B. G., 1952: Eklutna is USBR's first project in Alaska. Engineering News-Record, 14, no. 11, 35-36.

17. Foster, H. A., 1934: Duration curves. Trans. A mer. Soc. Civil Engineers, 99, 1261-1267.

18. Friedrich, Wilhelm von, 1939: Gewasserkund (1930-37). Geographisches Jahrbuch, 54, 85-180. Schlachtensee, Gotha Justus Perthes.

19. Gilbreath, J. A., 1952: New uses for cold water. Heating and Ventilating, 49, no. 2, 106.

20. Girand, J ., 1941: Water supply on the upper Salt River, Arizona. Trans. Amer. Soc. Civil Engineers, 106, p. 398.

21. Goodman, W., 1939: The evaporative condenser. Heating, Piping and Air-Conditioning, 10, 165-168; 225-228; 327-328.

22. Hail, L. S., 1921: The probable variations in yearly runoff as determined from a study of California streams. Trans. A mer. Soc. Civil Engineers, 84, 191-213.

23. Hazen, R., 1951: Analysis and use of surface water data. Proc. Conf. Water Resources, 1951. Urbana, IIIinois. IIIi­nois State Water Survey Div., Buiietin No. 41, 87-95.

24. Hoglund, M. L., 1953: Water chiiier ups production of electro­plating tanks. Heating, Piping and Air-Conditioning, 25, 108-109.

25. Holden, K., 1943--44: Construction of tanks and reservoirs. Proc. Conj. Minnesota Section, American Water Works Assoc., 91-95.

26. Jarvis, C. S., 1934: Discussion of the paper "Duration curves" by H. Alden Foster. Trans. Amer. Soc. Civil Engineers, 99, 1249-1251.

27. Jordan, H. E., 1946: Industrial requirements of water. J. A mer. Water Works Assoc., 38, 65-68.

28. Keiley, R. C., 1949: Certain criteria in the selection of appa­ratus for power plant engine cooling. Diesel Power, 27, no. 8, 194-198.

29. Langhaar, J. W., 1953: Cooling pond may answer your water cooling problem. Chemical Engineering, 60, no. 8, 194-198.

30. Laubach, N. B., 1950: Selection, operation and maintenance of water cooling towers. Oil and Gas J., 48, p. 58.

31. LeBaiiiy, A. R., 1951: Some economic factors in the selection of cooling towers. Trans. A mer. Soc. Mechanical Engineers, 73, 1021-1025.

32. Martin, R. ]., 1948: Evaporative condensers, their use in water shortage areas. Refrigerator Engineering, 55, p. 453.

33. Meinzer, 0. E., 1942: Hydrology. Physics of the Earth, Part IX. New York, McGraw-Hiii, 712 pp.

34. Mitcheii, W. E., 1950: Water Supply Characteristics of Illinois Streams. IIIinois, Dept. of Public Works and Buildings, 311 pp.

35. Moore, E. W., et al., 1950: Summary of Additional Data on Alaska Waters. Washington, D. C., National Research Council, Committee on Sanitary Engineering and Environ­ment.

86 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

36. Muller, S. W., 1947: Permafrost, or Permanently Frozen Ground and Related Engineering Problems. Ann Arbor, Michigan, J. W. Edwards, 231 pp.

37. National Association of Manufacturers, 1950: Water in Indus­try. New York, National Assoc. Manufacturers and the Conservation Foundation, 51 pp.

38. Olstad, M. H., 1948: Evaporative coolers and condensers. National Engineer, 52, no. 1, 12-14.

39. Partin,]., 1953: Water conservation-a by-product of indus­trial waste control. Sewage and Industrial Wastes, 25, 1050-1059.

40. Petrica, ]., 1951: Relation of frost penetration to under­ground water lines. J. Amer. Water Works Assoc., 43, 911-916.

41. --and ] . W. Hall, 1951: Frost penetration in Montana soils. J. Amer. Water Works Assoc., 43, 904-908.

42. Physical basis of water supply and its principal uses. Physical and Economic Foundation of Natural Resources, Part II. U. S. House of Representatives, Interior and Insular Affairs Committee, Washington, D. C., 73 pp.

43. Powell, S. T. and H. E. Bacon, 1950: Magnitude of industrial demand for process water. J. Amer. Water Works Assoc., 42, 777-785.

44. --and L. G. von Lossberg, 1949: Relation of water supply to chemical plant location. Chemical Engineering Progress, 45, 289-300.

45. Redman, W., 1950: Mains above ground in spite of 40 below zero weather. Water Works Engineering, 103, 120-122.

46. Riddick, T. M ., 1950: How to prevent pipe line freezing. Engineering News-Record, 145, no. 19, 38-41.

47. Salzman, M. G. and L. Elliot, 1951: Type of water supply influences location and layout of Texas steam electric plant. Civil Engineering, 21, no. 5, 30-33.

48. Simonsen, R. N., 1952: How four oil refineries use water. Sewage and Industrial Wastes, 24, 1372-1377.

49. Strout, R.: Industrial water (unpublished). Urbana, Illinois, Illinois State Water Survey Div.

50. Sturgis, S. D., ]r., 1952: Arctic engineering know-how gets acid test at Thule. Civil Engineering, 22, no. 9, 31-35.

51. Sweet, C. G., 1952: Consider steam-jet refrigeration units for low cost water chilling. Power, 96, no. 9, 132-133.

52. Tannehill, I. R., 1943: Weather around the world. Princeton, N. ]., Princeton University Press, 200 pp.

53. Telkes, Maria, 1953: Fresh water from sea water by solar distillation. Industrial and Engineering Chemistry, 45, 1108-1114.

54. Thomas, H. E., 1951: The Conservation of Groundwater. New York, McGraw-Hill, 327 pp.

55. Thomas,]. F.]., 1953: Industrial water resources of Canada. Water Survey Report, No. 1-4. Ottawa, Dept. of Mines and Technical Surveys, Industrial Minerals Div.

56. Thornthwaite, C. W., 1946: Moisture factor in climate. Trans. Am. Geophys. Un., 27, 41-48.

57. U. S. Dept. of Agriculture, 1941: Climate and Man. Washing­ton, D. C., 1248 pp.

58. U. S. Geological Survey, 1953: Surface water supply of the U. S., 1950, Part III. Water Supply Paper No. 1173. Washington, D. C., 730 pp.

59. --, 1953: Surface water supply of the U.S., 1950, Part VI. Water Supply Paper No. 1176. Washington, D. C., 826 pp.

60. --, 1915: Surface water supply of the Yukon-Tanana region of Alaska. Water Supply Paper No. 342. Washing­ton, D. C., 343 pp.

61. --, 1920: Water supply of the St. Mary and Milk Rivers, 1898-1917. Water Supply Paper No. 491. Washington, D. C., 590 pp.

62. U. S. President's Materials Policy Commission, 1952: The technology of ocean resources. Resources for Freedom, 4, 115-126.

63. --, 1952: Water for United States industry. Resources for Freedom, 5, 83-98.

64. Van Deusen, E. ]., 1951: Cold weather operation of distri­bution systems. J. A mer. Water Works Assoc., 43, 909-910.

65. Weaver, P., 1952: Turning waste heat into refrigeration. Diesel Power, 30, no. 6, 66-68.

66. --, 1952: Water, a special editorial report. Power, 96, no. 9, 72-117.

67. --, 1951: Water supplies. Industrial and Engineering Chem­istry, 43, 1734-1737.

68. Westcott, R., 1947: Evaporative condenser scale control. Refrigerator Engineering, 54, 15-17.

INDUSTRIAL OPERATIONS UNDER EXTREMES OF WEATHER

by

]. A. Russell; W. W. Hay;]. W. Waters; H. E. Hudson, Jr.;]. Abu-Lughod, W. ]. Roberts, and]. B. Stall;

A. W. Booth; and E. F. Taylor. Edited by]. A. Russell.

VI. WEATHER LIMITATIONS TO PRIMARY IRON AND STEEL PLANT OPERATIONS

By ]. W. WATERS

(Original manuscript received 27 March 1956; revised manuscript received 7 June 1956)

ABSTRACT

The effects of weather extremes on operations of iron and steel plants, and the adjustments in plant operations that have been successfully used to meet extreme conditions are considered. It is found that serious limitations to iron and steel plant operation are imposed by only two conditions, low temperature and permafrost.

This paper is an attempt to determine the weather conditions which impose efficiency limitations upon the operations of primary iron and steel plants. The weather conditions range all the way from those which are conducive for optimum performance to those which completely preclude operations. The solution of the problem is based upon consultation with steel plant operators through personal interview and by means of questionnaire.*

A fully integrated primary iron and steel plant, as this descriptive name suggests, consists of an integration of several distinct industrial entities, which have become recognized as parts of a greater whole because of their material flow linkage, and their tendency to common ownership and similar location. These separate departments comprise buildings, special structures, equipment, and operations which differ greatly from one another. Treatment of all departments together would be unproductive of meaningful generalizations. It cannot be assumed that the separate departments would react similarly upon exposure to extreme weather conditions. Con­sequently it has become necessary to recognize the following major divisions:

* Companies consulted: 1. Algoma Steel Corporation, Sault Ste. Marie, Ontario 2. Bethlehem Steel Company, Bethlehem, Pennsylvania 3. Colorado Fuel and Iron Corporation, Pueblo, Colorado 4. United States Steel Corporation, Pittsburgh, Pennsylvania 5. Youngstown Sheet and Tube Company, Youngstown, Ohio

87

1. Coke ovens 2. Coke oven by-product plant 3. Blast furnaces 4. Open hearths 5. Rolling mills 6. Utilities 7. Intra-plant transportation 8. Storage of iron and steel products 9. Administration

1. Low temperature

The temperature which is considered optimum for all the plant subdivisions pertains in most instances to worker efficiency, which should be distinguished from worker comfort, since the optimum temperature for worker comfort (70 to 75F) is not necessarily the optimum for worker efficiency. A temperature of approximately 50 to 60F appears to be optimum for worker efficiency. Thus 40 to 70F is a suitable range depending upon the location of worker activity with respect to plant-generated heat and outdoor weather (table 1). However, the optimum temperature for the operation of equipment is not comparable to the optimum for worker efficiency in all instances. Blast furnaces perform best at lower temperatures (0 to 40F), because cold air tends to have a much lower absolute humidity than warm air, and with dry air less heat energy is required in the blast than with humid air.

88 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

The opmwn of steel men concerning optimum temperature differ, depending upon the climate at each plant; at the more northerly plants "optimum" temperatures are lower. The possibility exists that such differences represent, in part, the adjustment of each plant's performance to the average, or typical weather conditions of its locality.

Although the overall operating efficiencies of steel plants tend to decline from the maximum as the temperature decreases from the optimum, that decline is very gradual so that few overall critical temperature levels appear to exist. One significant critical temper­ature level occurs at 32F below which the freezing of hydraulic equipment becomes a problem (table 1). At temperatures between 32 and 70F fully normal operations are not hampered by temperature condi­tions to a sufficient degree that any changes in practice or equipment are deemed necessary.

At temperatures slightly below 32F the alterations in practices and equipment which become necessary are only very minor ones. Depending upon the operational conditions of the equipment (degree of shelter from the wind, nearness to plant generated heat, etc.), changes gradually become necessary as the temperature is reduced without any marked evidence of reduced efficiency. For example, the following adaptations are necessary under exposure conditions of approximately OF:

1. Frozen ore and coal in railroad cars are loosened by heating devices, such as torches, steam injectors, or thawpits.

2. Finished materials (steel strip, sheets, etc.) which would suffer deterioration if exposed to low temperatures and accompanying moisture condi­tions are stored in heated shelters or warehouses.

3. Space heaters (gas, coal, or oil fired salaman­ders) are required to provide heat in buildings at locations where the temperature of operations is insufficient for equipment or men.

4. Precautions are taken concerning all hydraulic equipment. Pipe lines and valve equipment are drained, or the water is run continuously if the pipes and valves are not protected by heat, by insulation, or by being buried below frost level.

5. Production based solely upon natural gas is curtailed if an increased domestic gas consumption makes necessary a reduction in the supply which can be made available to industry.

The degree to which plants are adapted to weather extremes depends to a very great extent upon the nature of the climate of each locality. Thus, one plant which has not been exposed to temperatures

lower than - 20F would probably suffer a serious curtailment of operations at -30F. At another plant, which occasionally undergoes exposures of -30F, practices and equipment will have been adopted which will sustain such a minimum without serious interference. For this second plant the exposures of - 30F are not serious, and operations could probably be maintained continually at - 20F. This plant would probably begin to experience a serious curtailment of operations as the temperature dropped below -40F.

It is not logical to assume, merely because steel plants on this continent are not exposed to temper­atures lower than -40F that they could not operate at greater extremes by incorporating further adapta­tions in practices and equipment. Estimates concern­ing the extreme exposure conditions under which such plants might be able to maintain continuous opera­tions made by plant operators at the plants which experience the greatest extremes could be erroneous, since a tendency exists for operators to think that their own ability to adapt to extreme conditions closely approaches the limit. Therefore, a clear distinc­tion must be drawn between facts which pertain to actual experience and estimates which are derived from experience. Two facts pertain to actual experi­ence: occasional exposure of steel plants to a minimum of -40F need not seriously curtail operations; and continuous operation at - 20F seems possible.

To illustrate further the adaptations in practices and equipment that become necessary as the tem­perature decreases, the following items are listed. They pertain to normal operations as practiced at a plant which experiences occasional minimum tem­peratures approaching -40F and relatively frequent occurrences of minima of - 20F.

(1) Coal and ore piles freeze if wet. The coal and ore are dislodged, if necessary, by explosives. However, the freezing of coal piles is not common because of the heat retentive properties of coal in piles. Coal piles seldom freeze to a depth of more than one or two feet. (2) Ice forms on rails and switches near the quenching tower. If necessary, the ice is cleared every day or two by work crews. (3) Coke by-product tanks are heated to prevent freezing, especially during idle periods.

(4) Blast furnace stock bins and hoppers are steam heated because the ore and coke will freeze if wet.

(5) Unheated mill buildings of standard structure (corrugated sheet metal on structural steel frame) require more heat than becomes available from hot rod or strip steel of small dimensions. Heat is provided by salamanders or conventional space heaters.

MAY 1957 ]. W. WATERS 89

(6) Salamanders must be placed near all valves and hydraulic equipment, and in locations where workers require heat. (7) Frost on cold ingots and billets leads to some rusting when frost melts.

(8) Steam and fuel oil pipelines are insulated. (9) Water is run continuously in outdoor pipelines which are not drained. Hydrants are drained. (10) Water transportation of iron ore, coal, and limestone ceases during freeze-up. (11) Ore and coal become frozen in hopper and gondola cars. Steam heat and work crews are required to dislodge the ore or coal. Alternate devices are torches and thaw-pits. (12) Bunker fuel oil storage tanks are heated near their outlets to prevent the oil from congealing. (13) Fracture and breakage of rails, structural mem­bers, etc., occurs with rough handling in unheated warehouse buildings. Rail steel becomes brittle at -10 or -15F. Some fracture of steel ingots occurs at -20F.

(14) Steam is turned on the rollers in the rolling mills especially during idle periods. (15) Water supply presents no problem for this particular plant despite the low temperatures, because of the location on a large fast-flowing river. A freeze­up problem might arise if water supply is based upon a lake of limited size or a small river. If, however, necessary precautions are taken concerning the operation of the intake system it seems likely that where sufficient water exists in the form of ice, the water can be made available for plant use. The occurrence of freezing and the thickness of the ice can be minimized by installing an ice-breaker upstream from the intake and a boom across the entrance of the intake; by releasing warm waste water upstream from the intake, and by installing air bubbling apparatus beneath the reservoir pond.

It is estimated that operations planned for the above described conditions would probably encounter very serious efficiency impairment at temperatures below - 50F, even for short periods of exposure. Some of the problems that would probably bring about operational limitations are listed below.

(1) The impact brittleness in steel and cast iron members would probably result in a considerable breakage of equipment and machinery.

(2) Errors, accidents, and lost production would probably occur because workers would devote much time and attention to keeping themselves warm. (3) Serious problems concerning the operation of continuous rolling mill equipment would probably

occur, particularly if the mills ceased producing for more than a brief period of time. Mills rolling hot items of small bulk such as steel strip would probably become inoperative since the heat from the steel would be insufficient.

(4) Serious losses of production would probably occur through breakage by freezing of both water and steam pipelines, and valve equipment.

(5) Obtaining an adequate supply of water would become a problem depending upon the winter runoff regime of the river, or the depth and volume of the lake which serves as the source of water.

The possibility of operating successfully at tem­peratures lower than -40F depends upon the two variable factors which were discussed previously: the operating efficiency required, and the limitations placed upon costs of production. It appears to be theoretically possible that by accepting greatly increased costs, and a considerably reduced efficiency, operations would be possible under the minimum temperature condition of any locations upon the earth's surface. In any case a decision would have to be made concerning the two variables. Reduced efficiency or shutdown would become necessary during periods of extremely low temperature, unless critical divisions were protected by additional shelter struc­tures and changes in equipment and practices. Such adaptations would only be necessary for limited periods of time, since no location on the earth is continually subjected to its minimum temperature. On the basis of the evidence available from North American plants it is impossible to derive generaliza­tions concerning how much reduced efficiency, or how much increased cost would become necessary to facilitate operations at temperatures lower than -40F. Table 1 presents low temperature data pertaining to the experience and estimations of the operators of North American steel plants.

Problems of industrial construction associated with deep ground frost and permafrost are treated in Paper III of this monograph. The material in the present discussion is directed specifically toward problems of building facilities for iron and steel manufacture. No serious problem exists in constructing coke ovens, blast furnaces, open hearths, etc., in areas which experience seasonal ground frost, but it would probably be difficult to construct and maintain such structures upon permafrost, both because of their great weight and because of the great amounts of heat which they generate. Consequently it seems likely that steel plants, structurally comparable to those which now exist in North America, would be unable to operate if built upon permafrost.

90 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

TABLE 1. The effect of low temperature conditions upon steel plant operations(•>

Steel plant subdivisions

2 3 4 5 6 8 9 10

Coke Intra-Low temperature Coke by-product Blast Open Rolling plant Ad minis- Overall

condition Cb l ovens plant furnace hearth mill Utilities transport tration Storage plant

1. Optimum 40 50 40 40 50 50 50 50 50 40 to to to to to to to to to to 70 60 70 70 70 60 60 60 60 70

2. Critical 32 32 32 32 32 32 32

3. Minimum for: -30 -30 -20 -20 i. continuing full B to B to to B B B B to B

operation -30 I -60 -30 I -50 -30 -30 -30 -30 -30 -30

ii. partial -30 I -60 -30 -30 -30 B -30 -30 -20 operation to to to to -30 to to to

I -50 I -50 I -50 I -40 I -40 I -40 I -60

iii. starting-up -20 -30 I -20 -20 I -20 I -20 -20 operations to to to to to to

I -50 I -50 -30 -40 -40 I -50

C•l Temperatures are presented in degrees F. Figures marked with an 1 are estimates, not based upon an actual experience of the temperature condition. B stands for below.

Cbl The low temperature conditions (column 1, table 1) for which data are tabulated are defined as follows: 1) An optimum tem­perature condition is one that not only does not deter from, but can also be conducive to maximum operational efficiency. 2) A critical temperature condition is one which marks a distinguishable limit to operations of any specific degree of efficiency, beyond which the operational efficiency differs. 3) (i) A minimum temperature condition for a continuing full operation is one which marks the low tem­perature limit to an operation which functions fully or continually without low temperature induced interference. At temperatures below the minimum, full operation is not possible continuously. (ii) A minimum temperature condition for partial operation is one which marks the low temperature induced limit to an operation which functions in part (any of the productive facilities operating) for any period of time. (iii) A minimum temperature condition for a starting-up operation is one which marks the low temperature induced limit to starting up the operation of productive equipment after it has been idle sufficiently long to have become cooled to the tem· perature of the air.

However, it does appear to be technically possible to construct a steel plant satisfactorily upon perma­frost providing that all known precautions are taken and providing necessary structural changes are made. Actual experience indicates, however, that few bulky structures constructed upon permafrost have not encountered considerable foundation instability. Thus it might be anticipated that a considerable reduction in operational efficiency and a considerable increase in cost of production would plague any initial attempt to operate a steel plant upon permafrost. Not only would the erection of the heavy structures present problems, but the construction and main­tenance of most of the lighter structures, such as coal and ore bridges, rolling mill machinery and buildings, and power plant, would pose impressive difficulties.

3. High temperature

High temperature conditions have received at­tention in this study only because they occur as warm season characteristics of nontropical climates. Consequently this treatment of the effect of high temperatures upon steel plant operations will appear inadequate if judged in terms of tropical operating experience. However, due to the occurrences of

extremely high temperatures in high latitude con­tinental locations, the degree of heat experienced exceeds that of many tropical areas for periods of relatively short duration.

The overall efficiency of steel plant operations tends to decline from the maximum as the atmospheric temperature increases from the optimum of 50 to 60F. The rate of efficiency decline does not appear to be great, however, and no overall critical temperature level appears to exist beyond which a significantly lower degree of operational efficiency occurs. The decline in efficiency that does occur seems to pertain in most instances to worker activity rather than to equipment or machinery behavior. An exception to this generalization exists for blast furnace and open hearth furnace operations. Hot air has a high moisture bearing capacity so that even at moderate relative humidities the absolute moisture content of hot air can be very great. More heat energy is required to operate furnaces when the moisture content of air is great. Consequently the operational efficiency of blast and open hearth furnaces tends to decline as the temperature increases from the optimum.

It can also be noted that the optimum temperature range for the storage of coal is 32 to 40F because the rate of oxidation varies directly with the temperature.

MAY 1957 J. W. WATERS 91

Thus, for example, it is possible that coal which will store for 90 days during winter will only retain its coking quality for 30 days during a hot summer. Also, spontaneous combustion becomes more likely in high temperature than in low temperature. Temperature variations do not have a directly detrimental effect upon coal storage, even in terms of exfoliation caused by the alternate freezing and thawing of water in the coal. This is probably because the amount of water in a coal pile is small, and because atmospheric temper­ature variations are not readily reflected in coal pile temperature variations because of the insulation properties of coal in piles. However, the greater the diurnal and seasonal range and rate of temperature variations, the greater the possiQility for both oxida­tion and spontaneous combustion through the occur­rence of induced drafts within the pile as a result of the temperature differential between the coal pile and the atmosphere.

The high temperature extremes which have been experienced by North American plants have not brought about stoppages, nor even serious production interferences. One plant has operated at a temper­ature of 105F. The decline in efficiency that occurs due to the effect of heat upon worker activities is the result of the following conditions:

1. In hot weather workers tend to avoid physical activities as much as possible so that production based directly upon worker activity declines.

2. At the more northerly plants in North America worker efficiency reaches a peak during the spring and fall, (March-May and October-November) falling to a low during the summer and winter (July-August, and January). For example, open-hearth maintenance work, as required between heats, is poorer during the hot weather when operators tend to avoid the heat of the furnaces.

3. A tendency for worker absenteeism to be greater during heat waves than during cold spells is observed at more northerly plants. This condition does not prevail, apparently, at plants where high temperature is a more normal condition.

4. Rainfall

Rainfall does not, in most instances, significantly reduce the efficiency of steel plant operations. A heavy fall creates a greater degree of interference to operations than a light fall, but even the former does not produce any serious limitation to operations, provided an adequate drainage system exists. If the drainage system is inadequate, flooding might occur resulting in operational interruptions or even damage to structures and equipment. Such occurrences are

avoidable, however, provided adequate planning for plant site, layout, and drainage has been undertaken. This seems to have been the case for the North American steel plants dealt with in this study. No operational interferences were reported because of flooding, although such occurrences are possible because the high water requirement of steel manu­facture necessitates a waterside location.

Only very minor operational limitations are caused by rainfall. Such limitations pertain mostly to out­door work. The heaviest fall of rain recorded at plants which are included in this study was three inches within a period of two hours.

Rainfall is not usually a serious problem in coal storage. The only detrimental effect of rainfall on coal storage is the increase of moisture content which tends to accelerate the rate of oxidation. However, alternate wet and dry periods tend to augment the conditions conducive to the slacking of low rank coals.

A problem directly related to rainfall exists at plants which depend upon surface runoff for their water supply. Variations in the quantity, type, and regime of rainfall can result in periods of reduced runoff, so that a curtailment of production or even complete stoppage might become necessary. Such a condition can be prevented if steel plants are planned in terms of long term minimum river flow.

i. Water supply.* In the production of iron and steel, water for cooling accounts for a large proportion of the great water requirement. Lesser quantities are used for the quenching of coke, for condensing distil­lates, for scrubbing gases, washing down Cottrell precipitator dust, and in tanks for pickling, washing and rinsing sheet metal.

Estimates on the total amount of water required to produce a ton of finished steel vary. A study of selected German iron and steel plants revealed that approximately 38,000 gal of water were used per ton of raw steel [4]. A somewhat comparable estimate was made for American firms by the American Iron and Steel Institute, which set the water requirements at close to 40,000 gal per ton of finished steel. A more recent figure in common use in the industry today is 65,000 gal per ton of finished steel. Nebolsine suggests that if one excludes the water used in the generation of electric power and makes no allowance for steel and product manufacturers, the average water re­quirement in an integrated steel plant can be assumed to be between 40,000 and 45,000 gal per ton of finished steel. Where conservation measures are

*This section was originally prepared by Janet Abu-Lughod, Illinois State Water Survey. See Paper V for a discussion of the relationship between weather extremes and water supply in general.

92 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

TABLE 2. Average water requirements by type of product

Water Unit of requirements Source of

Product product (gal) information

Finished steel Ton 65,000 Ohio Water Res. Bd. Fabricated steel Ton 42,000 Symons Ingot steel Ton 18,000 Symons Pig iron Ton 4,000 Symons Cold rolled strip Ton 6,000 NAM Steel sheets and

coils Ton 13,000 NAM Hot rolled steel

plates Net ton 15,000 NAM Cold rolled high

carbon strips Ton 62,000 NAM Rolled steel Ton 80,000 NAM Rolled steel Net ton 110,000 NAM

employed, this figure may be reduced to 30,000 gal; where an inexhaustible supply exists, water may be used at the high rate of 65,000 gal per ton of finished steel [5]. It must be understood that of this water in circulation, all but about two per cent is in non­consumptive use and can be returned to the source of supply.

Various processes within the integrated steel mill, however, have different water requirements and the particular specialized steel products also have their own unique water requirements. Table 2 summarizes water requirements by type of product and table 3 presents information on the percentage of water in circulation which is used at each stage of the produc­tive process.

Of great value in the present analysis is water use within an integrated steel plant broken down accord­ing to stage of the productive process. Two such breakdowns are available in the literature [2, 5]. Table 3 presents the estimates of Nebolsine and the figures in a British iron and steel firm which was subject to detailed analysis. N ebolsine's figures are

· based on an assumed modern steel plant with a water requirement of 40,000 gal per ton of finished steel. The British figures are based upon a daily water circulation of almost four million gallons of water. Unfortunately, no production data are given for the British firm.

Although the figures presented in table 3 may be useful in determining the magnitude of the steel industry's demand for water, substantial evidence is available which demonstrates that water conservation in the steel industry can bring about an enormous reduction in water requirements and can thus permit the location of steel plants in areas where water is scarce and difficult to obtain. Two steel plants in the United States have achieved such reductions.

The most outstanding example of water conserva­tion through extensive recycling is found at the Fon-

tana Division of Kaiser Steel Corporation located in Southern California. Water in this plant is circulated 40 times and, it is claimed, the only water losses in the entire plant occur directly from evaporation or incorporation into the final product. The plant circu­lates some 144 million gallons of water daily. Elaborate recycling through a system of seven cooling towers results in a make-up requirement of only 2.5 mgd­only 2.8 per cent of the total water in circulation. As contrasted with the national average water re­quirement of 65,000 gal per ton of finished steel, the Fontana Division states that water requirements per ton of steel are between 1100 and 1400 gal in their installation.*

The Fontana Division attains its record minimal requirements primarily through cooling tower re­cycling. A second steel plant located in an arid region of Utah achieves similar reductions through the use of a cooling pond. The Utah steel plant, which circu­lates some 195,000 gal per minute, requires only 13,600 gal of new water per minute--a make-up requirement of under 7 per cent of the total water in

TABLE 3. Water requirements by production stage for an integrated steel mill

Volume of water Percent

Stage (thousand gal) of total

Nebolsine (per ton finished steel) Blast furnace area (including blowers,

furnace cooling, gas washing) 10 25 Open-hearth area 5 12.5 Coke plant area 5 12.5 Hot mills and related processes 10 25 Finishing mills and related processes 8 20 Sanitary boiler, make-up, miscellaneous 2 5

Total 40 100

Daniel (per day) Blast furnaces 791 20.0 Gas cleaning plant 460 11.7 Sinter plant 165 4.2 Blast furnace boilers 75 1.9 Coke ovens 572 14.5 Bessemer plants 315 8.0 Bessemer boilers 230 5.8 Rolling mills 575 14.0 Open-hearth plant 33 0.8 Tube works 512 13.0 Cold narrow strip mills 140 3.5 Mines department 25 0.6 Miscellaneous services 50 1.3

Total 3,923 99.4*

* Discrepancy due to rounding.

*Additional information on this plant may be found in: "Only 2.8% make-up water required daily at Kaiser Steel," Plant Engi­neering, November 1952, pp. 83-85; Elder Claybirn, "Deter­mining future water requirements," J. A mer. Water Works Assoc., February 1951, pp. 124-135; Richard D. Hoak, "Water use and conservation policy," Chemical and Engineering News, August 24, 1953, pp. 3348-3354; and many other articles.

MAY 1957 J. W. WATERS 93

circulation. Because of the high cost of cooling towers, it was decided that a cooling basin would be used. A two mile basin was constructed to reduce the temper­ature of the warm discharge water to 60 or 65F, a process involving a heat loss through evaporation of 18,000,000 BTU per min. Practically all water used in the plant is passed through this cooling basin and re-used. However, the water used to cool the rolls of the blooming, plate, and structural mills and to cleanse the blast furnace gas cannot be re-used economically due to deteriorated quality. This water receives slight treatment and is then made available for farm irrigation in the area [7].

As can be seen from the above, the chief means for reducing water requirements in steel production is through recycling. However, additional economies may be achieved through substitution of low quality liquids for cooling operations and through substitu­tion of spray methods of quenching for immersion techniques.

The Corby plant described by Daniel conserves water in the quenching of coke by substituting spent ammoniacal liquors for good quality water. The circulation of the quenching liquor is similar to that of water, except that " ... because of its highly corrosive nature, particular attention must be paid to the design of pumping equipment to withstand wastage" [2].

The substitution of sprays for immersion rinses is gaining increased acceptance in the steel industry, not only because of the water saving it makes possible, but also because of its efficiency in yielding higher quality steel, since the rate of cooling greatly affects quality. "The time necessary to reach 1100F by cooling in still water is approximately nine seconds and by spray quenching at 90 psi pressure, it is only two seconds" [6].

From the foregoing it should be clear that there is a wide range of flexibility in the steel industry's requirement for water. Despite estimates and averages which conclude that the water requirements per ton of finished steel range between 40,000 and 65,000 gal, experience in plants employing maximal conservation shows that a plant may operate in an area where fresh water is available at a rate as little as 2.8 to 6.9 per cent of the water required in circulation. Table 4 has been constructed on the assumption that an integrated steel plant using water on a once­through-and-waste basis will require 50,000 gal per ton of steel produced.

It has been estimated that as a rule in the United States the investment in the steel plant water system represents 3 per cent of the total initial investment and that, generally, the cost of operating this system

TABLE 4. Water intake requirements per ton of steel produced in plants using various water systems

Per cent of Water new water requirement to water in per ton of

Plant circulation finished steel

Theoretical once-through method plant 100.0 50,000

Fontana Division using cooling towers 2.8 1,400

Utah Steel Plant using cooling basin 6.9 3,450

requires only one per cent of the total cost of making finished steel [5]. These figures would, of course, be higher where conditions of extreme water shortage obtain.

In contrast to an average re-use of water of 98 per cent in a group of plants in the petroleum products industry in the United States, only 25 per cent of the water intake is re-used by the iron and steel firms reporting*.

5. Snowfall

Two significant problems arise in steel mill opera­tions as the result of increasing quantities of snow. It becomes increasingly difficult to maintain the flow of intraplant traffic, and the arrival of workers at the plant becomes impeded.

In all instances the amount of snowfall necessary to create operational interference depends upon whether such snow has been anticipated and has been prepared for. For example, plant operation in an area that receives on the average a very small amount of snow (30 in. per winter) becomes seriously hampered by a heavy fall of snow (3 to 4 ft). One plant experienced such a shutdown, and fully normal operations at this plant were not restored until one week after a storm during which 46 in. of snow fell. On the other hand, another plant in an area which receives a heavy average fall of snow (100 to 130 in. per winter) readily copes with such snowstorms, since for this plant such occurrences are relatively frequent. The former plant has little or no special snow removal equipment. The plant in the locality which receives much snow every winter is equipped and its workers are skilled for removing the snow. Moreover, in areas

* These and many other figures cited in this section have been taken from a study, Water in Industry, National Association of Manufacturers and the Conservation Foundation (New York, 1951). This study was based upon a sample for manufacturing firms throughout the United States. The sample was not random and there may, therefore, be bias in the results. All figures should be treated with reservation. Such percentages, therefore, have no validity for individual plants (or even the "average" plant). Their value is limited to comparative purposes.

94 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

of meager snowfall a tendency exists for workers to consider heavy snowstorms as major crises. Absentee­ism can be considerable. In areas of heavy snowfall, comparable snowstorms are expected occurrences and are dealt with as matters of routine, and absenteeism tends to be negligible.

The situation is augmented by the differing abilities of the cities to remove snow from their streets, and to operate their public transit systems. Therefore, it seems that snow can result in a greater reduction of operational efficiency for plants which are located in light average snowfall areas. Plants in heavy snowfall areas seem to be able to cope with the snow problems without experiencing seriously reduced efficiencies.

Since those plants which receive heavy snowfalls are able to handle their snow problems without serious operational limitation, it seems probable that by further increasing the available supply of special equipment, even greater quantities of snow could be handled successfully.

6. Humidity

Atmospheric humidity conditions affect steel plant operations in at least three different ways. For all of these situations low absolute and relative humidity are considered optimum. Departures from this condition tend to give rise to increased production costs, but not serious operational efficiency limitations. The first situation concerns the use of air in combustion, in blast furnaces and open-hearth furnaces. Humid air requires more heat to operate a blast furnace than does dry air. Because the quantity of moisture is less in saturated air at low temperature than at high temperature, there is an advantage in operating air­using equipment at low temperature. In areas of very high humidity it becomes necessary to operate moisture removing equipment at the air intakes. At a Brazilian steel plant high atmospheric humidity conditions prevail (in one case 90 per cent relative humidity with a temperature of over 80F). Nearly 1-1/2 tons of water is blown into an open hearth furnace with the air and gases every hour. This condition has made desirable the installation of moisture removing equipment [1].

The second situation concerns the corrosion of iron and steel equipment and products. Atmospheric con­ditions of low absolute and relative humidities minimize corrosion. As the humidity increases the occurrence of corrosion becomes more significant. The effect of corrosion upon plant equipment is not readily apparent in terms of reduced efficiency, although the long run cost of such deterioration can be considerable. A high relative humidity is a major reason for storing steel products under shelter.

Experiments which have attempted to determine the causes of corrosion have led to the conclusion that high relative humidity conditions contribute to the rate of corrosion as much as does rainfall. The results of the experiments indicate that very little corrosion occurs when the relative humidity is less than 80 per cent [3].

The third situation pertains to the storage of coal. The oxidation process is facilitated by water. Water appears to serve as a catalyst in this process. A variation in the quantity of available moisture, either through changes in the absolute quantity of moisture, or through changes in the relative quantity of moisture as a result of temperature change, results in fragmenting or slacking due to the alternate swelling and shrinking of coal through its alternate absorption and loss of moisture. This only becomes serious, however, for low ranking coals of a noncoking quality.

7. Sleet and ice

Sleet and the formation of ice as the result of pre­cipitation do not ordinarily impose a serious degree of efficiency limitation upon the operations of steel plants. Only activities carried on outdoors become directly affected-chiefly those which pertain to the movement of materials. If necessary, ice can be removed, or sand and salt applied to slippery roads and rails. More serious interference can occur if sufficiently strong winds accompany the icing and damage the electric power lines. Such interference depends upon the source of the plant's power, and upon whether transmission lines are susceptible to such damage. If excessive icing is anticipated, inter­ference can be practically eliminated by installing transmission lines of greater strength and by placing key lines underground. Efficiency limitations due to ice and sleet can be minimized to a sufficient degree that they become practically negligible by using plant-generated power and underground cables.

8. Wind

Wind does not ordinarily impose serious limitations to the operation of steel plants. Light winds that clear the air by removing smoke and gases are considered optimum. As the wind increases in speed operational conditions tend to depart from the optimum. As the speed of the wind becomes moderately gusty (15 mph) outdoor worker activity tends to be hindered. Wind­borne dust and cinders worsen this situation. However, only very minor limitations to efficiency result from such occurrences. The occurrence of wind can seriously increase the potential for spontaneous combustion

MAY 1957 J. W. WATERS 95

by inducing drafts in coal piles. Some exposed elevated structures, particularly coal and ore bridges, become susceptible to damage by winds of higher speed. Experience has shown, however, that winds up to 75 mph have not seriously damaged equipment.

High wind speeds associated with other weather conditions can interfere with operations. Wind-drifted snow increases the problem of snow clearance within plant yards, and makes interdepartment transporta­tion more difficult. Drifts can be expected with most snowstorms but can ordinarily be dealt with as a routine phase of snow removal. The wind can harass and delay clearing operations but cannot itself seriously limit operations for any considerable period of time.

Electrical installations, especially overhead trans­mission and distribution lines, suffer the greatest damage when high wind velocities accompany sleet and ice conditions. The degree to which a plant may suffer efficiency limitation as the result of such damage depends upon whether the plant is dependent upon outside sources for its electric power, whether its lines are adequately constructed, and to what degree its intraplant communication and electrical system consists of overhead lines. Winds need not ordinarily be recognized as limiting elements to the continuing operation of steel plants.

No other climatic elements (such as sunlight or visibility) or combinations of climatic elements have a significant effect upon the efficient operation of steel plants.

9. Conclusions

Serious limitations to the operation of steel plants are imposed by only two conditions: low temperature and permafrost. It has been estimated that steel plants would be unable to operate satisfactorily if they were constructed upon permafrost, and were exposed to temperatures lower than -50F.

Since most areas in which the temperature falls lower than - 50F experience such minima for only short periods of time, the degree of limitation to production which would be encountered need not be great. Thus it seems likely that of the two conditions, low temperature and permafrost, the latter, which affects operations the year round, might be the more critical.

REFERENCES

1. Blast Furnace and Steel Plant, 1947: 35, no. 11, 12, 1365-67; 1488-89; 1538.

2. Daniel, J. L., 1950: The supply and distribution of water by iron and steel works. Iron and Steel Inst. J., 165, 437-453.

3. Dearden, J., 1948: Climatic effects on the corrosion of steel. Iron and Steel Inst. J., 159, 241-246.

4. Guthmann, K., 1949: Wasserhaushalt der Eisenhuettenwerke. Gesundheits Ingenieur, 70, no. 21-22, 377-379.

5. Nebolsine, Ross, 1953: Water supply for steel plants. Tech. Session Assoc. Iron and Steel Engineers, Sept. 28. (Mimeo. by Hydrotechnic Corporation, 665 Fifth Avenue, New York.)

6. Wallace, W. P. and C. E. Manes, Jr., 1952: Are you getting the most from your water sprays? Iron Age, 169, part 1, 112-114.

7. Western Construction News, 1944: Water for Utah steel plant. p. 73.

INDUSTRIAL OPERATIONS UNDER EXTREMES OF WEATHER

by

]. A. Russell; W. W. Hay;]. W. Waters; H. E. Hudson, Jr.;]. Abu-Lughod, W. ]. Roberts, and]. B. Stall;

A. W. Booth; and E. F. Taylor. Edited by ]. A. Russell.

VII. THE PETROLEUM INDUSTRY

By A. W. BOOTH

University of Illinois

and E. F. TAYLOR

De Golyer and MacNaughton, Dallas, Texas

(Original manuscript received 27 March 1956; revised manuscript received 7 June 1956)

ABSTRACT

Each of the four phases of the petroleum industry-exploration, production, transportation, and storage­was examined for possible effects of each element of weather and climate. This list was compared to ex­perience in order to eliminate those effects which caused little or no operational problem or expense. Hence only those factors of weather and climate judged critical are discussed. The general restriction of the scope of the paper to cold winter environments is a result of this procedure.

The bulk of the following discussion on the effect of weather extremes on the petroleum industry, including exploration, production, transportation, and storage is confined to the problems arising in four general northern hemisphere environments, the tun­dra, the taiga, middle latitude steppe, and high altitude mountain and plateau areas in middle latitudes. All these environments have as climatic common denominators, extreme cold, a dangerous windchill factor, frequent freeze and thaw conditions, and snow cover.* All have been the scenes of intensive

* Tundra (subpolar) At least one month with average tempera­ture above 32F. No monthly average higher than 50F. Average coldest month averages in interior may be less than -40F. Frost possible any time of year. Meager precipitation. Small amount of snow usually blown into drifts on windswept surface. Ground or subsoil permanently frozen over wide areas (permafrost). Summer surface thaw converts plains area into vast marsh with numerous shallow lakes and ponds. Vegetational coverage pre­dominantly highly specialized low-lying forms such as lichens, mosses, and sedges. Koppen ET climatic zone.

Taiga (subarctic) At least one month but no more than three months with average temperatures over 50F. Mean annual tem­perature below 32F. Midsummer frosts normal. A small amount (10 to 20 in.) of rainfall largely concentrated in summer. Vege­tation dominantly a coniferous association (the taiga) degener­ating into a widely spaced bush-like association on its poleward margin. Wet swampy areas or muskegs scattered throughout. Koppen Df(w)c and Df(w)d climatic zones.

Middle latitude steppe Like adjacent middle latitude humid climates in general except for less rainfall, less reliable rainfall, greater temperature ranges and extremes, and stronger and more

96

petroleum exploration and significant recovery activity in North America in the past decade, with such areas as Norman Wells, Canada, and Point Barrow, Alaska, pointing up problems under tundra condi­tions, the Peace River area and other Northern Alberta areas problems under taiga conditions, Southern Alberta and the Williston Basin under steppe conditions, and various areas in the Rocky Mountain and northern Colorado Plateau the prob­lems in middle latitude, high altitude environments. The effects of dry and hot conditions are discussed in the final section.

In none of the above environments has activity been completely and permanently halted because of the weather factor (table 1). However, in all of them efficiency of operations as measured against a cost-of­operations standard developed in more humid and milder middle latitude environments is somewhat to very much lower than the usual norms. Operations in tundra areas are most severely handicapped, indeed,

frequent winds. North of 45 deg latitude have subarctic winters. Dominantly short grass vegetation allowing for much freedom of access. Koppen BSk and BSh climatic zones.

High altitude, middle latitude areas A mosaic of various middle latitude climates varying from very wet to very dry. Winters normally quite severe. Tendency to local climatic extremes en­hanced by variable exposure to sun and wind.

MAY 1957 A. W. BOOTH AND E. F. TAYLOR 97

TABLE 1. Critical temperatures for petroleum exploration

1. -68F

2. -60F

3. -45F

4. -40F

5. -30F

6. -20 to -30F

7. -20 to -30F

S. -20F

9. -10F

"Successful cementing jobs have ... been carried out (at this temperature) in bitter cold winds of gale proportions" [8]. " ... a northern Alberta wildcat (operator) had a kelly joint freeze solid in a rathole" [2]. "It is doubtful if any operator would run an extremely long casing string at temperatures lower than -45F because of the brittle nature of steel ... strings up to 6000 ft are run without regard to temperature" [5]. " ... winterized equipment kept (production) operations on schedule" (in the Williston Basin) [11]. "Sustained temperatures below this point mean very special care needed to maintain water supply" [6]. "Human efficiency 25 to 40 per cent of nor­mal" [8]. " ... surveying becomes extremely difficult since the eye has a tendency to freeze to the eyepiece of the transit . . . (and) the instru­ment ... difficult to handle" [4]. " ... with a strong wind ... made a con­tinuous blow torch heating operation neces­sary in a (seismic drilling operation)." "Seismic shooting is good if the temperature is above (this point)" [11].

to such an extent that as yet no purely commercial exploitation of oil has been attempted. In the remain­ing environments extremely rich strikes seem to have much more than compensated for higher costs in exploration, drilling, and production so that it is difficult as yet to assess from experience the marginal production limits.

1. The effects of cold weather on petroleum explo­ration

Special problems arise in exploration for petroleum in cold winter environments. Some, like the break­down of equipment at extremely low temperatures, the freezing of fluids, or the need for snowplows are directly attributable to weather elements. Others, like the need for special foundations in permafrost areas, a wintertime deficiency in water supply, or the very poor soil trafficability in muskeg areas, are indirect results.

The chief result of the combination of these direct and indirect problems is that exploratory operations in cold winter areas must be conducted over a longer period of time than in most other environments. It is this reduction of tempo plus the need for specialized materials and equipment which results in a generally higher cost factor or a lower efficiency rate. In spite of winter problems, both direct and indirect, the <mly activity which has been confined to summer is surface geological surveying in the tundra and taiga areas and some of the wildcat drilling in the Williston Basin.

i. Surface geology. The greatest deterrent to surface geological exploration in all the environments is probably heavy snow cover which obscures all exposures of rock. Such elements as severe cold, windchill, and storms become additional deterring factors in what is almost entirely an outdoor operation.

In the tundra area where the most severe conditions exist, geological field parties work only from about mid-April to mid-September. In the taiga there is about the same field season although summer ex­ploration is difficult in both because of the transpor­tation problem resulting from surface thawing and the formation of vast stretches of impassable terrain. To overcome this handicap helicopters are now being used. Outcrops are spotted from the air and the helicopter is set down as close to the outcrop as possible so that samples may be taken. This system of scouting and getting samples is also utilized in difficult mountain country.

In the steppe areas, in contrast to the tundra and taiga, winter exploration is not too unsatisfactory or too hazardous since snow is frequently blown or evaporated off large areas and, because the ground is frozen, cross-country travel is often much easier than in other seasons. In drier mountainous areas where snow will blow off exposed places (these exposed areas are often the sites of the best outcrops) the same situation applies. In either area with careful planning it has been estimated that surface parties can operate at about 75 per cent efficiency in winter.

ii. Geophysical

(1) Seismic surveys. In seismograph operations the working crew is usually divided into several units. First is the road-dozing tractor crew with its own surveyors laying out roads. This group is followed by another surveying crew which locates shot holes. Then comes the drilling crew working with their water wagons and finally the shooters, recorders and "jug hustlers" who complete the work. Each of these groups is independent and usually self-sufficient; they follow each other at variable intervals-as much as a year sometimes occurs between road building and shot hole surveying-although drilling is usually followed by shooting within a day interval [6].

Because of the heavy equipment utilized by some groups and the precision requirements of others, effects of storms, very low temperatures, heavy snow cover, poorly drained land, and frozen water sup­plies, all reduce efficiency of operations an estimated 50 per cent or more in the winter season in tundra, taiga, steppe, and high altitude environments. How­ever, in the tundra and the taiga areas in spite of the handicaps of cold, snow, and poor lighting (surveying

98 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

by using lights is absolutely necessary in the tundra in winter) winter is a preferred season because of the frozen ground which permits "weasels" in the tundra and the heaviest kinds of equipment in the taiga to get to nearly all sites. In the Peace River, Alberta, muskeg area drilling equipment is usually moved out before the first thaw (about May 1) and moved back about October 15 and much of the summer supply work is done by plane.

In all these environments the most difficult job of all in cold weather is drilling, because the driller and the rigs become sprayed with water and mud and are soon sheathed in ice. When temperatures drop to -30F, two hours may be required to drill and prepare a single shot hole because of this frequent freezing. This is about five times as long as under normal conditions. Also associated with cold is metallic crystallization and the kelly swivel is especially susceptible to breakage. Because holes must be drilled below the first layer of weathering into premanently frozen or solid ground, drilling is usually deeper (20 to 40 ft) and therefore more time-consuming in these environments than is normal [6].

Any drilling requires water, and during periods of low temperature two problems of water supply are: 1) finding a reasonably close source, and then 2) keep­ing the water liquid for use in drilling. If the water supply is a considerable distance from the drilling a reserve supply of water must be built up to permit continuous drilling while water trucks are refilling.

Seismic shooting in permafrost or muskeg areas is handicapped by the unsatisfactory seismographic pattern which results from the presence of frozen ground or of water lenses under a frozen surface. Several shots at each hole may be necessary or complete data on permafrost conditions must be obtained [4]. (2) Gravimeter. Gravimeter and magnetometer sur­veys are affected by heavy snow, blizzards, and severe cold, and in the tundra area these types of surveys are carried on only in the April to September period. Gravimeters are transported on the ground by "weasel" and in small aircraft which can land frequently to permit readings on the ground. Magnetometers may also be airborne. Good flying weather is thus very desirable for both aerial magnetic and gravimetric work. Absence of electrical storms is necessary for magnetometer surveys.

In other environments operations can be carried on in winter in a more or less normal fashion except during the periods with temperatures below about -30F when surveying becomes difficult. The cost per station of gravimeter operations for wintertime operations is about twice that of summer operations.

The best times are the two-months period before the spring thaws and the period July through October when mosquitos and other insects constitute the greatest natural problem to operations. In Alberta a common practice is to work the open plains country in summer and the muskeg areas in winter when they are more accessible.

2. The effects of cold weather on drilling operations

The most serious weather hazard to drilling opera­tions is extremely low temperature, a handicap found in all four of the environments under consideration. It has been estimated that extreme winter conditions add at least 20 per cent to overall drilling and well costs [6]. However, it must be noted drilling has never been entirely suspended because of cold weather alone, although with temperatures below -45F it is doubtful whether an operation would run an extremely long casing string (over 6000 ft) because of the brittle nature of steel (table 1).

The list of special adaptations that are made to counter low temperatures in drilling operations is a long one. All derricks must be enclosed, usually with metal sheathing and heavy canvas around the ply­wood panels or heavy canvas around the pump and engine houses. In addition, special bunkhouses and shanties must be built for the men who are usually confined to the isolated cold winter drilling site for long periods of time. Usually mud pits are also enclosed and water and steam lines entrenched if the well is to be more than 6000 ft deep. It is almost impossible to to carry out drilling operations without a steam boiler on the location. Water for mixing mud and cementing must be kept from freezing by constant use of steam. Steam is also used to insure complete removal of ice and frozen mud from equipment before it is moved to a new site and for preheating equipment that is being set up in a new site. In the latter situation flame throwers are also sometimes used [5].

It is estimated that cementing operations require almost double the time and labor as compared to that in above freezing temperatures because of the careful preparations which must be made before operations begin. Nevertheless, cementing operations have been carried on with the temperatures at -68F [8].

Another critical need for a steam supply is to keep blowout prevention equipment in condition so that it will be available when needed and to keep mud and water from freezing in the standpipe and kelly hose or to keep freezing mud off the tool joint pins.

Preparation of a site in winter involves such special processes as snow clearance and burning of straw, crude oil, or lignite on the surface to thaw the ground,

MAY 1957 A. W. BOOTH AND E. F. TAYLOR 99

or dynamiting the hard surface so that pits and cellars may be dug. Just these items of preparation may cost $6000 to $9000 before a rig is moved into a location as compared to perhaps at the most several hundred dollars under usual conditions [11].

A further expense item in winter drilling is the need for larger than normal crews not only because so much extra work is necessary but because of lowered human efficiency in extremely cold weather. A rule of thumb utilized in estimating output of work is that with temperatures below - 20F it takes twice . as many men twice as long to do half as much [8]. In one Arctic project it was estimated that a weather­experienced carpenter (1.5 to 3 times more efficient than a carpenter inexperienced in working in low temperatures) was 75 per cent efficient at 32F, SO per cent efficient at OF, and 25 per cent efficient at -30F. Much of this lowered efficiency is ascribed to bulkier clothing and greater precautions taken at the lower temperatures.

Perhaps the greatest cost factor of all, beyond the need for special equipment and more man hours of work is the cost of transportation, a cost factor which compounds itself more or less geometrically as drilling sites are removed farther and farther from supply centers and farther and farther poleward.

i. Tundra. A special problem in drilling in tundra areas relates to the presence over wide areas of permafrost, or permanently frozen ground. In some sites the entire subsurface zone to as much as 1200 ft depth may be frozen, in others the frozen material may be concentrated in lenses and dikes of varying extent and thickness. Most of these problems are similar to those discussed in Paper III of this mono­graph. They are caused by the thawing of frozen ground by heat generated during drilling. Cost of adequate precautions against damage to foundations and pipe can amount to as much as $500,000 for a deep test hole.

ii. Taiga. In taiga areas in spite of the drilling prob­lems associated with cold weather, which in this environment are estimated to cause a 10 to 15 per cent slowdown, winter is the favored season for drilling [5]. This is largely because warm season surface thawing results in poor drainage conditions and practically impassable terrain over wide areas. In one case where road construction was attempted, the cost of a 70 mi road was $500,000 or over one-third the total cost of well drilling [1]. The usual procedure is to prepare the site in the fall by digging pits and cellars in the yet unfrozen ground and moving in the drilling equipment as soon as the ground is frozen. If the drilling is not completed by the end of the

winter season, the rigs are left until the next season. Heavy snows are not particularly a problem in these areas because drifting conditions are usually not severe [5].

iii. Steppe. In the steppe environment, although snow­fall is less than in the taiga it may cause more difficulty because of the increased drifting with stronger winds and the normal exposure of nearly all sites to the full sweep of these winds [5]. True blizzards with low temperature, strong wind, and low visibility due to blowing snow are also a factor of contention. In view of this problem a bulldozer for snow removal is usually a standard item of equipment at each rig site. Transportation problems are also bothersome during the spring thaw period and after heavy summer rains when country roads become impassable.

iv. Mountains and plateaus. In the Rocky Mountain fields of the United States it is estimated that ordinary field wells can be drilled at about 90 per cent efficiency in winter. Wildcat drilling averages about 60 per cent efficiency, although there is a wide variation in this figure, since efficiency is usually dependent on the ability to transport equipment and personnel regu­larly and to supply drilling water.

3. The effects of cold weather on oil well production

Low temperatures are the chief climatic handicap to petroleum production in the environments under consideration. Even in the occasional cold spells of other middle latitude climates there are such problems as sluggishness of flow of very heavy crude oils through transmission lines and pumps, the freezing of gas in meter runs, the rapid formation of paraffin and hydrates inside of casing pipes and cold surface lines, the freezing of flow lines and lead lines from the wells to the tank batteries, maintenance of water supply, and lowered human efficiency [13].

In high latitude and high altitude areas these problems are compounded not only because temper­atures get extremely low and stay low for long periods of time, but also by the presence of deeply frozen earth and permafrost which may cause cooling of fluids before they reach the surface and by the fre­quent occurrence of windchill conditions which cause an extraordinary rate of heat dissipation from well fluids and all exposed surfaces. Crude oils with pour points above 2SF will not flow readily through the permafrost zone. With all gases and liquids at low original temperatures the adiabatic cooling associated with release of pressure in recovery operations is usually sufficient to produce serious condensation and solidification difficulties even with fluids of normally high volatility. Another unique problem

100 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

in permafrost areas is the formation of ice in shallow oil sands which cuts off flow from the source [12].

Numerous special measures must be taken to over­come these cold weather difficulties. To prevent or reduce paraffin, ice, and hydrate formation in the casing, especially where it passes through a zone of frozen earth or ice, one of several steps may be taken; electrical resistance heating units or coils may be attached to the casing; hot mud, brine, or heated oil may be used to fill in the annular ring; the annular ring may be steam heated; or the whole tubing may be given special insulation. In permafrost areas, although such methods may expedite the flow of fluids, they nevertheless aggravate the problem of maintaining frozen earth about the casing. Casing collapse is the most serious problem yet encountered in sustaining Arctic production, especially if wells are shut down for any length of time [12].

Pumping units are best completely enclosed to reduce windchill loss and enable heat waste from prime movers, supplemented or unsupplemented by steam or electric radiators, to warm lubricants and bearings and to provide temperatures in which crews can function efficiently. Often steam from a portable or, less frequently, a stationary heater is used to keep valves, the blowout preventer, and small fittings from freezing. Steam is also traced along pipes, or if the source is portable, applied when necessary at those places along the line where freezing or paraffin formation has caused blockage [2]. Electric coils may also be used for this purpose. When crudes are very heavy much more elaborate measures, such as con­tinuous heating at all pumping points and valves, must be taken to keep up a continuous flow. With so much need for special heating, secondary problems of fuel, power, and water supply further complicate the situation. Some measures have been taken recently in North America to utilize cold resistant, year round silicone base lubricants and special types of quick starting and high horse power motors [13].

4. The effects of cold weather on petroleum transpor­tation

Petroleum is transported by trucks, railroad tank cars, tankers and barges on waterways, and pipelines. Of all the forms of land transportation, pipelines have proven the most efficient, particularly in the move­ment of crude oil, and so pipelines are constructed as soon as possible in all the variety of climatic areas in which oil is produced. In each of the climatic areas under discussion there are specific problems imposed by the weather elements on both the construction of pipelines and the operation of pipelines. The most

serious of these problems are encountered during winter, with very low temperature and snow the most critical elements, although daily and seasonal temperature fluctuations also pose special problems. Related to these specific climatic problems are the problems of ground freeze and thaw and of permafrost.

i. Construction of pipelines

(1) Permafrost areas. The initial problem in laying pipelines in permafrost areas is the transporting of equipment, machinery, and personnel to the scene of operations. Whenever possible this is done over inland waterway systems in the period between June and mid-September before the waterways become completely closed by ice. After the ice is formed, it is believed that frozen rivers such as the Mackenzie can be used as roadways for trucks and tractors [3], since evidence from Siberia indicates that through the use of the proper methods winter sledge roads on large rivers are possible. However, even in the warm season, water transportation is hazardous because strong prevailing winds make rivers and lakes choppy. Wooden barges and pontoons built for heavy cargoes are difficult to handle and open-top pontoons have been swamped by wind-whipped waters. Weather also makes it difficult to construct base camps [7].

In zones of permafrost, pipelines cannot be buried. Pipes are laid on the surface and bulldozers cover them with tundra moss and brush which in turn receives a dirt fill. This insulating layer not only serves to retard surface thawing and freezing but also prevents thawing of the hard frozen subgrade.

Anchoring a pipeline at river crossings and else­where requires certain features of design [10]. A steel pipe which is 577 mi long at -30F in the winter becomes 0.36 mi longer at 70F in the summer and this expansion has to be distributed along the line to avoid damage. The sinuosity of the line suffices largely to accommodate expansion and contraction without special provisions, but on long grades the pipe tends to crawl with each reversal of temperature. Unless anchored at the proper places the tendency to move down hill may produce stresses sufficient to break the line.

Steel pipe contracts approximately 8 in. per 1000 ft for a temperature drop from 100 to OF. This inside contraction would cause a stress in the steel of 20,000 lb per sq in. This much stress should not cause a line to break, but screw-coupled lines pull apart during severe cold weather and sometimes field welds break.

Heavy snow will interfere with pipeline construction. Where an annual snowfall of 37 in. was encountered, no work stoppages were necessary. However, in moun-

MAY 1957 A. W. BOOTH AND E. F. TAYLOR 101

tain areas of western Canada, a snowfall of 120 in. is sufficient to impede construction.

The tremendous scope of operations and the technological processes involved in pipeline construc­tion requires the use of a great number and variety of machines. Some machines are, by necessity, designed for special use in cold climates where con­ventional machinery is troublesome or useless, and without a design adapted to weather conditions some jobs cannot be done. Similarly, conventional machin­ery, designed and used in milder climates, can be used in cold climates if special preparations and maintenance are practiced. In like manner special considerations must be given to the problem of equipping personnel for work in these cold winter areas. (2) Nonpermafrost areas. Pipeline construction in areas free of permafrost utilizes the advantages of burying pipes to prevent, as much as possible, any climatic interference. Air temperatures, ranging from -50 to 100F, transmitted to oil in an exposed pipeline would not present operating problems unless the oil has a low pour point. Ground temperature at a depth of three feet is 25F. Pipelines buried at three feet have enough cover and weight to provide against frost heaving in spring and at the same time prevent the oil from getting cooler than 30F. Perplexing construc­tion problems do, however, arise in laying pipelines across areas of muskeg and peat swamps too large to be detoured. These areas are too soft and wet during summer to support the conventional type of pipeline construction equipment. It is necessary to construct during the winter months a work road on timber foundation along the right of way which will support tracked vehicles used in construction and later the light vehicles that might be used for maintenance purposes.

The problem of severe winter temperature again arises in connection with long sections of exposed line in these swampy areas, permitting chilling of the oil with consequent increase in viscosity. Wet peat moss can be molded about the pipe and allowed to dry, when it can be wrapped with waterproof paper to form an excellent insulating blanket. This method of insulation is expected to preserve the fluidity of the crude and also prevent excessive expansion of the line when exposed to hot sun.

Contrary to the working season in the permafrost areas of the tundra and taiga, pipeline construction in the high steppe and some areas of the taiga is done during the summer months, between the late breakup of frost in May and the early fall rains and freezing in October. More construction equipment must be concentrated and utilized than ordinarily. Compared

to colder climates and winter work, construction in the high steppe is more rapid so pumping station con­struction must commence in advance of pipelaying. This requires air transportation to supply those pumping stations which are isolated from ground transportation.

In areas where pipelines are buried, a continuous wind is a handicap to construction. A steady wind will handicap stovepipe welding, particularly if the ditch is parallel to prevailing winds. The air currents will go down into and along the ditch. This will cause the welding crews to be shut down more often than if they were roll-welding away from the ditch with higher electric currents and larger rod. ii. Operation of pipelines. The principal problem of pipeline transportation is to keep the crude oil above the pour point so that it will flow. Oil temperature below the pour point not only resists flow but paraffin condenses and solidifies within the pipeline, causing obstructions. The mobility of petroleum has been increased by mixing with natural gas.

Petroleum from Norman Wells, with a low pour point and a small amount of paraffin in the crude, will flow at temperatures below -70F, which does not present serious obstacles to all-year operation or pipeline distribution even under the rigors of the arctic winters.

At the temperatures encountered-down to -65F­on the Norman Wells-Whitehorse pipeline, it was found that the friction loss in a 4-in. crude oil pipe at the desired rate of flow would amount to approxi­mately 5. 7 lb per sq in. per 1000 ft of line. This necessitated pressures which required spacing of pumps so that power was available to pump viscous oil during periods of low temperatures. On a segment of the pipeline 577 mi long pumps were spaced 50 mi apart.

Due to extreme changes in temperature, crude oil and products pipelines in the subarctic have suffered serious breaks [9] resulting from expansion and con­traction of pipe or ground heave.

A snow cover is an effective insulating surface and some pipeline authorities have relied upon a sufficient snow cover to prevent oil temperatures from dropping too low.

The flow of oil through a buried pipeline, in which the minimum temperature is 25F, is not obstructed by severe winter conditions. However, entering crude oil having low temperatures must be heated to a uniform temperature to protect the line against damage which might be caused by expansion and contraction arising out of the movement of oils of differing temperatures.

Pipeline operations are affected by flooding when

102 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

pipelines are broken by flood waters or are broken by damage to their supporting structures, particularly at river crossings. Broken lines shut down a system and flood waters prevent repairs. Damaged and broken pipes present a hazard by leaking oil which may be carried by flood waters to a fire source. However, floods affect pipeline transportation primarily by damaging or shutting down terminals and gathering points where oil is pumped through and received from the line. However, it has been possible to maintain approximately 90 per cent of normal gasoline flow in a pipeline through the use of auxiliary pumping units when the terminal pumping facilities were shut down.

iii. Truck movement. Moving crude oil by trucks is, of course, dependent on the same problems as are other forms of surface transportation. Deep snow, blizzards, and spring "road ban" in Canada present problems. Trucks cannot operate in the tundra or muskeg during the warm season and a heavy snow storm will limit all operations until the snow is cleared. iv. Inland waterway and tankcar shipment. Transpor­tation of petroleum over the inland waterways of the climatic zones being considered is subject to the same limitations as those described for carrying materials for pipeline construction above. The impacts of weather elements on tankcar transportation are the same as those treated in Paper II.

5. The effects of cold weather on the storage of petroleum

Low temperature and snow are the most critical weather elements in the storage of both crude and refined petroleum with heavy rainfall a secondary consideration.

The main effect of low temperature is the deposition of the least viscous constituents of petroleum within storage tanks or in the pipes and valves leading to and from them. Periodic drainage of the tanks to scrape out deposited waxes, the constant circulating and heating of such very high viscosity products as asphalts, and the tracing of pipes and casing of valves with steam lines are the usual corrective procedures. Actually the seriousness of this problem is more a function of the pour point factor than of the weather. For example, Norman Wells oil with its extremely low pour point does not present as much of a storage problem in the production area as do many oils produced in much milder climates.

The most serious effect of very heavy snows is that they make floating roof tanks impractical. This type of tank, with the roof floating on the stored liquid, allows for no vapor space and thus eliminates evapo-

ration. In the Rocky Mountain areas of heavy snows, closed tankage systems are now being utilized to overcome the snow load factor with the consequent increase in evaporation rate. In tank farms special care is taken to prevent drifting of heavy snow over fire lanes. This is usually done by putting the fire lanes or roads on the earthen fire walls ordinarily built around individual tanks with the expectation that wind will keep the lanes clear.

In areas where heavy rainfall may be expected, storage tanks are provided with special tank top drains. If there is any expectation of flooding, tanks may be specially anchored or kept filled with water to prevent their floating out of place.

6. Dry, hot summer climates and the petroleum in­dustry

Included among the areas of the world with very dry and very hot summers are several in which there has been significant development of the petroleum industry. Notable examples are the southwestern United States and the Middle East. In none of these areas has climate ever proven more than a minor handicap to the industry. Strong winds, high temper­ature, and rapid variations in temperature as well as the normal dry climate problem of water supply are the weather elements most likely to cause difficulty. Perhaps the most serious of these is strong wind and this only because the wind usually carries with it much dust and sand. Usually the season of strongest winds is also the driest season when there is a po­tentially large supply of material available for wind carriage. i. Exploration. Normally hot, dry climatic areas are almost ideal for exploration because of the large number of days when outdoor work can be carried on without any particular weather handicaps and because lack of both vegetation and a deep soil cover permits for easy surface and aerial exploration as well as permitting widespread cross-country operations on normally very trafficable terrain. In addition to high temperatures which produce a degree of abnormal fatigue in workers, the chief handicaps to exploration are sandstorms which temporarily stop surface ex­ploration parties, aerial survey work, and seismic surveying, recording, and shot hole activity. In the Arabian Peninsula an average of 10 to 15 working days are lost each year during the period from June to September when sandstorms or shamals occur.

ii. Drilling. Drilling operations are also most handi­capped by sand and dust storms although measures must also be taken to overcome the effects of hihg temperature. In a drilling operation in southern

MAY 1957 A. W. BOOTH AND E. F. TAYLOR 103

California it was found necessary to prevent sand drifting by constructing a windbreak of corrugated steel sheathing and to set up a water spray system beyond the fence to settle dust and sand. Later an ordinary snow fence was also set up. In Arabia mud tanks rather than earthen pits are used to store drilling fluid in order to prevent the fluid from having too large a sand content as a result of blowing or contact with the pit surfaces. An ordinary practice in dry areas is to have all drilling engines equipped with heavy batteries of filters on the carburation and oil systems to prevent sand wearing of moving parts. Ventilating fans, sometimes in conjunction with water drip or spray systems, to keep sand moving away from equipment or to prevent it from blowing on equipment are sometimes utilized. Efforts to have personnel at drilling sites wear goggles or respirators during sandstorms have never met with too much success.

iii. Transportation. Wind and high temperature are the weather elements that interfere most with the truck transportation which is so common to the petroleum industry. Trucks on duty in areas subject to sandstorms and extremely high temperatures ordinarily are equipped with large size tires for better traction over sand drifts, have pressurized cooling systems, and sometimes are equipped with emergency oversize fuel and water tanks. Having trucks stall or tip over in sand banks or be forced to layover because of very poor visibility during sandstorms are common experiences. Wind-pitting and sand in movable parts increases truck maintenance problems. The use of corrosion resistant tanks on trucks is a recent innovation.

iv. Storage. One of the major replacement items in very dry areas has been steel storage tanks. Sand­storms erode the paint off the tanks so that night

dampness will start corrosion. Subsequent sandstorms remove the rust and the process of rusting starts all over again. To overcome this corrosion loss plastic tanks have been introduced in the Middle East.

Because of very high temperatures it is also the usual procedure to paint tanks with reflecting paint which reduces evaporation about 30 per cent as compared to tanks painted black, and to keep lines from tanks to pumps just as short as possible to prevent dangerous vaporization.

REFERENCES

1. Binning, Ralph L. and B. H. Corey, 1953: Efficiency curbs Canadian drilling costs. World Oil, 136, 286-292.

2. Elliott, D. J., 1951: Canada's subzero temperatures create complex operating problems. World Oil, 133, 115-117.

3. Finnie, Richard, 1942: A route to Alaska through the North­west Territories. Geographical Review, 32, p. 416.

4. Hemstock, Russell A., 1952: Permafrost problems in oil development in northern Canada. Canadian Mining and Metallurgical Bulletin, 45, p. 280.

5. Hunter, Vern H., 1953: Drilling operations continue the year round in Canada. World Oil, 136, p. 160.

6. Joseph, James, 1953: Br-r-r-rother, it's cold outside. World Oil, 136, 286-288.

7. Lloyd, Trevor, 1944: Oil in the Mackenzie Valley. Geographi­cal Review, 34, 275-307.

8. Potter, A. R., 1952: Sub-zero weather complicates well servicing operations. World Petroleum, 23, 88-,-89.

9. Ralph, Henry D., 1943: Truman committee preparing Canol report. Oil and Gas Journal, 42, 23-24.

10. Stockman, L. P., 1944: Canol: an engineering project from road building to completed refinery. Oil and Gas J., 43, no. 21, 65-69, 76.

11. Sveen, Lloyd W., 1953: How they're whipping Williston's winter. World Oil, 136, 120-122.

12. Vender Ohe, Karl L., 1953: Operating problems in oil explo­ration in the arctic. Petroleum Engineering, 25, p. 312.

13. Wright, G. D., 1951: Winter operations in western Canada. World Oil, 133, 169-174.

INDUSTRIAL OPERATIONS UNDER EXTREMES OF WEATHER

by

J. A. Russell; W. W. Hay; J. W. Waters; H. E. Hudson, Jr.; J. Abu-Lughod, W. J. Roberts, and J. B. Stall;

A. W. Booth; and E. F. Taylor. Edited by J. A. Russell.

VIII. PETROLEUM REFINING AND SELECTED CHEMICAL INDUSTRIES*

By A. W. BOOTH ** University of Illinois

(Original manuscript received 27 March 1956; revised manuscript received 7 June 1956)

ABSTRACT

Several important chemical industries, including petroleum refining, the synthetic rubber industry, the coke chemical industry, and the synthetic ammonia industry, are featured in common by largely unhoused plants and unenclosed units, by tall structures, and by great use of water and other liquids in their opera­tions. They are all thus peculiarly susceptible to the elements of weather and climate. Each one of these industries was examined originally on a structure by structure basis with respect to the effect each element of weather and climate would have on the operations and functions of that particular portion of the plant. The results of that survey are summarized in the following report. However, the report is organized on a weather element basis, since such an organization not only fits into the general organization of the mono­graph of which it is a part, but also results in a considerable economy in presentation. Extremely high temperature, temperatures below 20F, heavy rainfall or snowfall within a brief period of time, constant high humidity, and winds of extraordinarily high speeds are the elements which most seriously handicap operations and for which the greatest adjustments must be made in this group of industries.

Because of many basic similarities, particularly with respect to climatically induced problems, certain chemical industries such as the coke chemical industry, and the synthetic ammonia industry are discussed in the following along with petroleum refining. Weather

* The information compiled for this report is based on the experiences of the following petroleum refineries, chemical com­panies and engineering firms: Dow Chemical Company, Midland, Michigan and Valasco, Texas; du Pont of Wilmington, Delaware; Commercial Solvents Corporation, Terre Haute, Indiana; Im­perial Oil Company, Whitehorse, Yukon Territory, Canada; Imperial Oil Company, Winnipeg, Canada; Shell Oil Company of Montreal, Canada and Houston, Texas; Phillips Petroleum Company, Kansas City, Missouri; Standard Oil Company, El Paso, Texas; Humble Oil Company, Baytown, Texas; Panama Corporation, Hooker, Oklahoma; Standolind Oil and Gas Com­pany, Pettus, Texas; Skelly Oil Company, Borger, Texas; Socony Vacuum Company, Paulsboro, New Jersey; The Texas Company of Port Arthur, Texas and Lemont, Illinois; The Globe Refining Company of Lemont, Illinois; The Marley Company, Inc., Los Angeles, California; The Ralph M. Parsons Company, Los Angeles, California; Koppers Company, Pittsburgh, Pennsyl­vania; United States Steel Corporation of Geneva, Utah, Gary, Indiana, and Pittsburgh, Pennsylvania; Spencer Chemical Co., Pittsburg, Kansas; Pittsburgh Consolidation Coal Company, Library, Pennsylvania.

**From the original contributions on petroleum refining by Alfred W. Booth; synthetic rubber by Oliver Burke and Joseph A. Russell; coke chemicals and synthetic ammonia by Alfred W. Booth and Leslie Martin.

conditions affect synthetic rubber production in approximately the same way as oil refining. Plants of these various industries are found in many different parts of the world from the tropics to the subarctic, and thus have been subjected to a wide variety of climatic conditions and weather extremes. These variations are significant because large scale chemical industries, although they are fairly well standardized, must be adapted to the prevailing climate by modifi­cation of unit designs, insulating techniques, steam tracing, or other ways, since in all these industries unhoused plants and unenclosed units are the rule.

Any and all climatic and weather elements may affect the various plant equipment and operations associated with this group of industries. Extremely low temperatures will affect those facilities, such as scrubbing towers, condensers, and pipelines, all very common in chemical and refinery plants, in which fluids are subject to freezing. Very low temperatures will also decrease the efficiency of labor and unhoused instrumentation panels and boards. Very high tem­perature will also have the same effect on labor and

104

MAY 1957 A. W. BOOTH lOS

instruments in addition to posing problems in main­taining proper water cooling conditions and the storage of raw materials and chemicals such as anhydrous ammonia. Rapid variations in temperature will cause variations of absorption rates, acid strengths, and in gas volumes which may result in periods of very low efficiency until adjustments are made. High humidity may cause a slower startup of plant operations and accelerate corrosion. Extremely heavy rainfall may occasionally stop these essentially outdoor operations and, indeed, in the rainy tropics in the coke chemical industry special roofing and cambers are required for the removal of rain water. Heavy snow fall not only hinders interplant move­ment but imposes special design problems, particularly for tank storage facilities. Because high, narrow vertical structures are so common in this group of industries, another problem of special design within it is for resistance to exceptionally strong winds. On the other hand the nature of these industries is such that rather steady ventilation of the plant areas by winds is significant.

Perhaps the optimum climate for this group of industries is a cool, dry climate with light steady winds. For example, in the coke chemical industry the consensus is that fairly low temperatures generally enhance plant efficiency, and the upper middle latitudes with annual means of SOF are the best areas. In the synthetic ammonia industry the most efficient plants seem to be in the middle latitude steppes with their generally cool, windy, and dry climate. For petroleum refineries and the petro­chemical industries optimum temperature conditions lie between 45 and 7SF, the higher figure largely determined by the temperature of available water supplies and, more important, high temperature reaction on worker efficiency. Decline of efficiency, increase in cost, and certain operating problems are caused more significantly by temperatures below the optimum range.

1. Low temperature

Most processes in chemical industries are operated in unhoused units which with a few exceptions are completely exposed to the weather, and as such are subject to a wide variation of weather conditions. However, low temperatures do not ordinarily cause shutdowns because units and processes will operate in the coldest weather if carefully designed and main­tained to prevent freeze-ups. Where temperatures are low for prolonged periods of time as in the tundra and taiga (ET and Dfc, Dfd), or where occasional low temperatures are encountered which seriously

affect sensitive units such as coolers, condensers, exchangers, and instrumentation, housing is required to minimize exposure to cold. With housing around sensitive units, petroleum refinery operations have continued in temperatures as low as -SOF or lower at Whitehorse, Yukon Territory. A synthetic ammonia plant in Kansas has operated during a cold wave when the temperature remained at or near -lOF for a period of several days. The only serious effect of this low temperature was to cause continual freezing of the water in the cooling towers. In parts ofAlberta, Canada, with a January average temperature of 12F, to prevent freezing during short periods of temper­ature below OF, the fans which blow heat out of the cooling tower of a synthetic ammonia plant are reversed to heat the water.

Of the many functional groupings which comprise a chemical plant there are those which require housing under all conditions of temperature in order to operate efficiently. Among these are the administration and laboratory buildings, the pumping, boiler and power houses, and the instrumentation. In severe climates such as the taiga, housing is extended to protect heat exchangers and fractionating units which are difficult to keep "on steam" during prolonged periods when temperatures remain below 20F. In a petroleum refinery at Montreal, Canada, batteries of heat exchangers are permanently enclosed in a concrete building and all connective outdoor piping is steam traced [12]. At refineries in Yukon Territory, Canada, a substantial part of the refinery equipment is en­closed with the columns of the units extending through the roof. This permits housing the pumps, heat exchangers and instrumentation, thus operating and maintenance problems which would result from exposure to low temperatures are elimimated. Housing of equipment, such as exchangers, pumps, power units, etc., can present a safety problem when the air in housings becomes contaminated with com­bustible vapors. This necessitates an alarm system which will automatically shut off machinery. By this safeguard diesel engines and pumps can be installed in the same room without a fire or explosion hazard [16].

Since much of the chemical and refinery processes are continuous and automatic, control is maintaineP through an elaborate system of sensitive instrumenta­tion. The efficiency of this control has been greatly improved by centralization and removal from ex­posure to the weather. All instruments are housed as conveniently as possible to the entire processing area in severe climates. Housing has eliminated the difficulty of weather-proofing and accessibility of individually located instruments [6].

106 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

Oil refinery engineers agree that 20F is the critical temperature below which problems imposed by ex­posure can be expected and winterizing of units becomes necessary. In the coke chemical industry it is estimated that efficiency of operations would be decreased 50 per cent without the use of housing and other special techniques at temperatures below 32F, and that OF is the critical point at which all vulnerable parts of the plant must be housed. The most trouble­some factor is the prevention of freezing of materials in pipelines.

Liquid products are also transported throughout the plants in pipelines. Products susceptible to freezing are handled in pipelines that are insulated and steam traced. The tracer line transfers enough heat to the air bath surrounding the pipe so that the pipe wall temperature will always be above the freezing point of the liquid in the pipe. If the pipeline product has a high freezing point or if outside temperatures drop below the product freezing point pipelines are equipped with double steam traced lines. Pipeline insulation is finished in canvas wrapping and painted with weather­proof cement. Molded forms are used for certain pipe sizes and common types of fittings and are serviceable in temperatures from 1200 to -20F [5]. In one Kentucky oil refinery, fractional distillation units, desalting tanks, surge and storage vessels, coopers, oxidizers, mixers, isomerization towers, and pipelines have all been insulated [7].

As with liquids, care must be taken to avoid excessive cooling of gas products. In some gas cooling coils, hydrates and crystals of methane are formed on the walls of the tubes if the gas is cooled excessively and if there is any moisture in the gas. When cooling liquids or gases contain water, the water might freeze, causing considerable damage to the tubes, headers, or piping. In cooling lubricating oil or other viscous fluids the viscosity increases with decreased temper­atures, tending to increase operating pressure in the system.

If a line freezes, thawing is a major job. However, obstructions are ordinarily detected before the freeze extends too far and the usual experience is spot freezes.

Chemical plants located in areas that have severe winters are faced with construction and maintenance problems caused by low temperatures. In a Montreal oil refinery all construction operations are scheduled to allow excavation and installation of concrete to be carried out in milder seasons [12]. Here a catalytic cracker regenerator had to be installed completely before arrival of freezing weather. Unhoused equip­ment is designed so that it is capable of being replaced

as units. This reduces exposure of men to the weather and reduces down-time [17].

The most adverse combination of climatic elements negatively affecting refinery processes is low temper­ature accompanied by snow. This combination pre­sents the conditions which require the greatest effort to keep refineries "on steam" and forestall any shut­down. It also has an effect on personnel by creating absenteeism which noticeably reduces output and efficiency under prolonged conditions. There are some difficulties in getting maintenance crews to work in foul weather. Attempts are made to eliminate major repair jobs during the coldest weather and pieces of equipment have been shut down for as long as 24 hr in severe weather rather than to try to get a crew to repair it. Inside work is assigned during extremely cold weather, but if outside work is necessary for several hours, temporary shelters are provided for maintenance personnel. Also, temporary scaffolding is erected and covered with a fire proof tarpaulin where barehanded operation is necessary [9].

The successful winterizing of units and adaptation of personnel and processes to outdoor work in cold weather is indicated by the production rate of an oil refinery at Lemont, Illinois, which is fairly constant through the seasons. However, where outdoor work is required, as in the coal handling part of a coke chemical plant at Gary, Indiana, it has been found that labor efficiency is reduced 75 per cent at 10 to 15F and is nil at OF. i. Water supply. Chemical industries are large users of water. The two chief applications of water are in the generation of steam and in the cooling of con­densers. The amount of water required for a petroleum refinery with 25,000 bbl a day capacity is 18,000 gal per min for cooling and 30,000 gal per hr for steam conversion [14]. Generally, if there is a plentiful supply of water, such as from a river or a lake, the processing water is run through once and then dumped as waste. If the water is not too plentiful and has to be used again, or if the temperature of the water supply is above the desired level, water cooling towers are utilized. These towers, used for the evaporative cooling of water by contact with moving air, vary in size as a function of air temperature in different climatic areas. Cooling towers in Montreal, Canada, are smaller than those of Gulf Coast refineries because of cooler average air temperatures which cool effec­tively without the necessity of an extended surface area [14]. However, during hot weather the cooling capacity of these smaller coolers and condensers is not great enough and must be augmented by water sprays. A hose or portable spray nozzle plays water over the unit to assist in lowering the temperature.

MAY 1957 A. W. BOOTH 107

Ammonia plant scrubbing towers in areas with very low temperatures also are subject to freezing. Their use involves the additional problem that at temper­atures below OF, the solubility of the scrubbing agent decreases so that copper precipitates out of the solu­tion and thus the efficiency of the operation decreases because it is more difficult to remove the impurities, carbon monoxide and carbon dioxide.

Provision is also made, particularly in cold climates, to decrease air flow during cold weather to keep the cooling tower from getting too cool. Operating difficulties are increased considerably in extremely cold weather since the processing temperature of cold water is seldom kept below 60F. Cooling towers operated in freezing weather are subject to ice forma­tion at the air inlets. The accumulation of ice will restrict the inlet area and reduce the air flow thus increasing the temperature of the water being circu­lated through the tower resulting in inefficient opera·· tion of the coolers and condensers [2].

2. High temperature

The effect of high temperatures varies from industry to industry. In oil refineries the chief result is less in changing operations than in changing unit designs. In the synthetic ammonia industry high temperature affects efficiency of operation and aggravates the storage problem. In the coke chemical industry effi­ciency of operations is also affected, but more signifi­cantly, in this industry high temperatures are very detrimental to labor efficiency.

In the petroleum refining industry and related petrochemical industries temperatures above the op­timum do not have any significant effect on operations because the largest percentage of refinery processing operations are those in which heating and high tem­perature maintenance is the dominant process. However, unit designs are, to some extent, modified on coolers and condensers in which heat transfer is essential. To operate efficiently, coolers and condensers must transfer heat from processed products to circu­lating water. The temperature of the water, therefore, must be low enough to absorb the necessary amount of heat. Cooling water is kept at temperatures be­tween 60 and 90F. The critical temperature of the water is 90F; if the water supply is warmer, then cooling towers and spray ponds must be used to lower the temperature to at least this figure. In the Gulf Coast area where the water supply is very warm­above 90F-and where high air temperatures keep it warm, cooling towers, spray ponds, coolers, and condensers are of larger design than those used in the cooler climates, because a greater cooling surface

area and circulating volume is necessary to compensate for the higher temperatures of water and outdoor air.

The most significant factor in limiting total syn­thetic ammonia poroduction is high temperature. The major effect of high atmospheric temperature is to raise the temperature of the cooling waters used in processing the raw materials and in synthesis of ammonia. High water temperature affects the absorp­tion operations and cooling of gases. As temperature rises the efficiency of production is reduced for each pass of the gas over the catalyst. There is a 28 per cent conversion of gas to ammonia at a water temperature of 60F. At a temperature of 95F the rate of conversion is only 12 per cent. The ideal temperature is between 50 and 60F. Above 80F there is a substantial rate decrease which increases the time required to produce a definite amount of ammonia and requires a greater number of passes over the catalyst to maintain production.

In addition, with high water temperatures the water scrubbers do not remove as much of the cata­lytic poison, carbon monoxide, as they do at lower temperatures. Only one per cent is removed at each scrubbing as compared to 2.25 per cent under winter temperature conditions. This situation causes an in­creased amount of stress on the caustic scrubbers. This problem could be reduced if not entirely elimi­nated by the use of refrigeration in the cooling towers.

High temperatures also affect anhydrous ammonia storage. The optimum temperature for storage is below 32F because high atmospheric temperatures cause high vapor pressures which in turn cause a loss of ammonia.

High atmospheric temperature is an important factor in coke plant performance. The inability to maintain proper oven coking temperatures due to insufficient over stack draft during extreme high temperatures is a significant item at various coke plants in the United States. Blowers are essential to provide supplementary draft on oven stacks at extremely high temperatures and/ or high elevations due to the decreased air pressure. As many as four blowers are necessary on the stacks to furnish a supplementary draft.

High temperatures reduce the maximum recovery of light oil products due to the higher temperatures of cooling waters. Light oil recovery operations can continue satisfactorily at a water temperature of 70F. Above 70F losses increase. The amount of loss is proportional to temperature as increased temperature affects the partial pressures of the gases. At lake-side plants in northern Indiana extraction of light oils is reduced seven per cent from winter to summer. This loss is relatively small compared to that in areas that

108 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

are not favored by large volumes of cooling water. A review of operating performance of several coke plants shows that light oil, and similarly, benzol products recovery was lower than normal for the winter of 1952-1953 due to the mild weather in January, February, and March in the eastern section of the United States. Light oil recovery from gas could be improved at high temperatures by artificial cooling if the value of the light oil warranted it.

3. Rapid temperature changes

Rapid changes in temperature of as much as 45F in eight hours do not ordinarily affect chemical plant operations because the process heat maintains stability of operation. If the sudden temperature changes include eventual temperatures very much below freezing it is possible that pipelines may snap or that the water seals for the vent pipes of volatile product stills may freeze and thus build up excessive and possibly dangerous pressure in the stills. A small heating coil can prevent such an occurrence. Safety valve settings should also be set properly to take care of a greater differential between opening and closing pressures and thus prevent leakage after sudden temperature changes [4]. In the synthetic ammonia industry sudden changes in temperature change the volume of gas going into compressors and thus require the operator to make compensating adjust­ments. If the temperature change is too rapid even with close watching and rapid adjustments a drop in efficiency of production usually occurs until temper­atures level off. ·

4. Rainfall

Of the kinds of precipitation which can potentially disrupt chemical plant operations, rain and snow are most important because of their great frequency and the large amount of precipitation which may fall. Rain is a major factor in the corrosion and deteriora­tion of units and accessories. It also contributes to flooding and trouble with electrical contacts, and interferes with outdoor work of personnel.

The first stage at which rainfall enters considera­tion is that of site location and plant layout. Flooding has shut down an oil refinery at Lemont, Illinois, after a three-inch rainfall, but another refinery nearby suf­fered no flooding under the same conditions.

Even if there is no threat of flooding, a soaking rain will stall operations in a petroleum refinery temporarily, usually in a sporadic pattern through the refinery. The trouble may be wet insulation in motors on one unit, wet filter elements on another

unit, or clogged oil collectors on a third unit. Old or worn insulation on exposed outdoor motors becomes wet easily and contacts may give trouble. Unprotected crane installations have been operating in a chemical plant in central Michigan since 1926, and while there has been trouble in wet and icy weather with electrical contacts, it has never been necessary to house the unit [17]. Current practice is to weatherproof com­pletely all motors installed in outdoor units and these will perform under all rainfall conditions except flooding. Oil collectors may become clogged when moisture has seeped into the unit during rains of an inch or more. One serious problem imposed by rain­fall is changing recording charts on individually located instruments [6]. This problem has best been overcome by housing the instruments.

Heavy rainfall seriously hampers and sometimes makes it impossible for a coke plant to carry on its operations. A rainfall of two inches in a single storm may shut down operations until the storm has sub­sided. Rain water may cool all units down so that normal operations are not resumed for 24 to 36 hr. There are a number of coke plants in India and Brazil where the coke ovens must be provided with a camber on top of the ovens for quick water removal in case of heavy tropical rains, and in some cases where the rainfall is exceedingly high a roof is provided above the ovens so that workmen can have some degree of comfort without becoming wet, and also to prevent a large mass of water from entering the coke ovens. Moisture will destroy the quality of ammonium sulfate so that complete housing is required in the processing and storage of this product.

A more widespread and destructive type of flooding results from the overflow of streams. One oil refinery in Kansas City was forced to shut down in 1951 when the Missouri River overflowed the high dike system which had provided adequate protection for many years [11]. The flood, which inundated almost all of the refinery site with the exception of most of the crude oil distillation equipment, the refinery labora­tory, the personnel office, change house, and main warehouse, had become a threat a few days before the shutdown, enabling refinery management to map a plan of a systematic halt. Complete shutdown and evacuation of all employees was effected in ten hours.

The greatest damage from the flood was to the electrical equipment; 850 motors plus countless other pieces were removed as soon as the water receded. In addition to motors this included switch gears, motor starters, instruments, and all types of controls. Some of the motors were dried in place by pulling rotors and installing hoods connected to furnaces fueled with oil. Other units were dried and repaired

MAY 1957 A. W. BOOTH 109

in outside shops at points extending from Texas to Chicago.

Since maintenance of insulation is one of the main considerations in operating outdoor processing units, much attention is given to the kinds of insulation used and techniques of application to prevent moisture seepage and consequent damage [5]. Any area of access into the insulation by rain provides the start­ing point of operational difficulties when the close limits of heat loss, heat gain, and temperature maintenance of operating units are disturbed. Pre­vention of moisture seepage is accomplished by various techniques of asphalt mopping and incasing insulation layers in impregnated canvas, special felts, and weather resisting paints.

As mentioned in the temperature section of this report some of the product pipelines throughout a refinery are steam traced to maintain temperatures of flow and processing. Low atmospheric temperature interferences are successfully overcome by this system but under conditions of cold wind and rain the demand for heat varies. A cold wind blowing across a pipeline lowers the heat value in the flow line. More exacting than the wind is a cold rain which creates a greater demand for heat as observed on the steam flow meter. The steam flow will jump up with a cold rain as it washes down the insulation [9].

5. Snowfall

Snow accumulation can interrupt transportation and movement within a chemical plant, reduce accessibility to various units and potentially affect the overall maintenance and output efficiency.

Most of the chemical industry units operate at elevated temperature and enough heat is dissipated to the surrounding air to keep the temperature of adjacent air above freezing. Any snow is melted before it gets a chance to accumulate. Snow is not an interfering factor to the operation of units, but it is a consideration in plant layout and housekeeping. Need for accessibility is an important reason for snow removal. In northern United States and in Canada greater spacing is allowed between buildings and operating areas to allow room for machinery to clear working areas of snow.

A snowfall of 15 in. has caused a slowdown for a period of 24 hr at steel works in northern Indiana. A snowstorm which gave from 20 to 40 in. in 1950 at Pittsburgh caused complete plant shutdowns for 48 hr.

6. High humidity

Most chemical industry processes require operating conditions which are maintained irrespective of atmos-

pheric humidity, and consequently efficiency in chemical industries remains basically unchanged in either low or high relative humidity. However, atmos­pheric corrosion which is normally more serious with high humidity, is an important factor in equipment and machinery deterioration. The intensity of the problem varies, but it is of such importance as to warrant a continuing effort of modifying unit designs, unit locations, and utilizing various structural mater­ials and alloys to find better ways of minimizing corrosion damage.

In ammonia plant operations ammonia leakage, the formation of oxides of nitrogen from the nitric acid plant, and the presence of carbon monoxide and carbon dioxide in the water scrubber, all make cor­rosion an especially serious problem in plant main­tenance. In the Gulf Coast area this problem is further complicated by salt spray corrosion.

7. Wind

Wind is an important consideration in an outdoor plant because of its speed and its changing or pre­vailing directions which influence plant layout and design. High speed winds are destructive where many of the units are tall and unhoused. The production of volatile products and emission of noxious gases make ventilation a necessity; therefore some air movement may be considered necessary. The critical limit of wind speed lies between 70 and 125 mph. Wind~ blow­ing with a speed at or above this range can be expected to damage units and interfere with operations.

All of the units in a modern petroleum refinery are designed to withstand at least 100 mph wind speed and in some areas such as the Gulf Coast where hurricane winds are experienced, units are made to withstand 125 mph winds [13]. Tall units such as stacks, cracking and fractionating towers, and large broad units such as water cooling towers are most susceptible to the effects of wind speed. At Houston, Texas, a hurricane blew down a giant water cooling tower 50ft high, 1000 ft long, and weighing 1,409,215 lb. All generators were knocked out and production stopped. Full production schedules were rushed to resumption in three weeks whereas ordinary recovery time from a damaged water cooling tower is 50 to 60 days [10].

There is a catalytic cracker at El Paso, Texas, 360 ft high, which will withstand a gravity and wind load of 20 lb per sq ft and a deflection not to exceed 12 in. in a 70 mph wind [8]. This design stress is calculated to exceed the wind speed encountered under normal conditions.

Winds of high speed can cause damage to the coal

110 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

bridge of a coke chemical plant if ample warning is not given in advance. When the plant is notified of an approaching storm the coal bridge is clamped to the rails, otherwise it might be blown to the end of the rail and topple over, as occurred in Providence, Rhode Island, during a storm in the 1930's.

High wind also affects the efficiency of operations in the coke chemical industry. In winter, winds of 30 to 40 mph cool the coke ovens very rapidly. At such times efficiency of operations is decreased (causes poor yields and affects the quality of light oils), and total production is reduced.

In order to minimize possible damage and carry out precautionary measures, oil refiners and operators of chemical plants along the Gulf Coast of the United States have set up a radar network to trace the path of Gulf hurricanes [13]. Each refinery has a shutdown procedure which permits production to continue until the winds of destructive force come within a critical distance. The cost of shutdowns is high. It takes 24 to 36 hr to fire up the multitude of units because many depend on feed stock from sister units. Also some are difficult to get in balanced operation after being shut down. Following a storm in September 1949 it required two weeks to get an entire plant running smoothly at capacity.

Although most refinery layouts are not oriented to prevailing winds, some units, such as a gasoline plant, are safer and more efficient when oriented to wind direction. A combination of topography and atmos­pheric conditions are important considerations in the layout of a gasoline plant [6]. In refinery layout it is preferable that any fires such as boilers or fired heaters be located on the upwind side of the plant so that normally any gas or vapor leakage within the processing areas will blow away from fires rather than toward them.

In areas of dust and sand storms any equipment which has motors, fans, gears, or pumps is particularly susceptible to failure from dust and sand accumulation [2]. Cooling towers require extra protection with decking, and maintenance must be increased through frequent inspection to prevent clogging [3].

At the beginning of this paper, reference was made to ventilation and air movement as necessary to remove gases. Changing air currents play an important part both in removing volatile vapors from work areas around refinery operating units and in dispersing waste gases discharged through stacks. Certain local meteorological conditions cause excessive and dan­gerous concentrations of gases [15]. In the coke chemical industry it was found that fine coal and char are not carried away unless the winds exceed four mph. Windy, dry, and gusty days are best for the

rapid dispersion of gases and other wastes in the atmosphere. Calm moist days, particularly those which have a strong temperature inversion, are the worst for the disposal of industrial wastes in air.

Problems of controlling air pollution result from variations in topography, their effect on wind cur­rents, and from large concentrations of industry in a comparatively small geographic area. It has been observed that the dispersal of industrial waste gases into the atmosphere may be safely accomplished by a combination of the following factors:

1. The determination of an economical stack height to insure minimum gas concentration at ground level.

2. Proper plant location with due regard to pre­vailing wind, topography and the surrounding neighborhood. In locating a plant consideration should always be given to general weather condi­tions of a given locality and to the location of the proposed plant site with respect to farms and towns and their relations to wind direction. Generally it is advisable to locate plants on the downwind side of towns and agricultural land. The major topo­graphical restriction on normal atmospheric dif­fusion comes from the presence of mountains and valleys. In most cases industry gravitates to valleys chiefly because of ease of transportation, sources of water for process, and for disposal of water wastes. From the point of view of air pollu­tion this is an unfortunate choice because valleys act as funnels carrying air streams for long distances. Under moist and calm conditions, dangerous con­centrations of polluting gases can build up easily and be carried to ground level where they may damage crops and health.

3. Alteration of the type of discharge by inciner­ation or by chemical means. Destruction of com­bustible gases is accomplished by passing the gas through the flame of a burner. In chemical alter­ation, acidic gases for example, have been passed through alkaline substances such as lime. In some instances, it has been necessary to build units which remove sulphur from sulphurous gases, resulting in altered effluent gases and recovery of useful sulphur.

4. Control of the rate of discharge according to daily local weather conditions to insure that the dispersal power of the atmosphere will not be exceeded.

5. Installation of proper control equipment so as to be able to meet the predetermined maximum emission rate.

MAY 1957 A. W. BOOTH 111

REFERENCES

1. Creevey, John, 1946: Safety considerations in plant design­III. The Chemical Age, 54, 427-429.

2. Degler, Howard E., 1951: Water cooling towers and air­cooled heat exchangers. Petroleum Refiner, 30, no. 11, 145-150.

3. Dresser, Harold A., 1951: Performance of cooling equipment. Petroleum Refiner, 30, no. 5, 110-113.

4. Hicks, Tyler G., 1950: Power plants for modern refineries, Part II. Petroleum Refiner, 29, no. 2, 129-132.

5. Kemp, H. S., L. T. Mullen, and A. P. Guess, 1951: Con­struction of acid recovery units, indoors or outdoors? Chem. Engineering Progress, 47, no. 7, 339-340.

6. Lewis, 0. L., 1951: Design of gasoline plants, Part I. Petro­leum Engineer, 23, no. 11, c-16---{;-22.

7. Ludwig, David Lee Von, 1947: Insulating unhoused plants. Chem. Engineering, 54, no. 3, 114-117.

8. McCone, Alan, 1953: Two erection practices speed refinery completion. Petroleum Refiner, 32, no. 1, 114-115.

9. Minevitch, J, R., S. E. Root, H. E. Boracks, and G. B. Knight, 1951: Chemical plant construction cost, indoors vs. outdoors. Chem. Engineering Progress, 47, no. 8, 385-391.

10. National Petroleum News, 1943: Storm damage quickly re­paired. 35, no. 36, p. 24.

11. Oil and Gas Journal, 1951: Plant rehabilitation. 50, no. 18, p. 63.

12. Oil and Gas Journal, 1951: Shell's building program at Mon­treal east refinery ups input to 25,000 bbl daily. 50, no. 9, 74-76.

13. Reese, A. L. and R. E. Spann, 1953: When the big winds blow. Petroleum Refiner, 32, no. 7, 211-216.

14. Shell News, 1951: Montreal refinery. p. 10. 15. Sittenfield, Marcus, 1951: When wastes go up the stack.

Chem. Engineering, 58, no. 5, 136-140. 16. Stockman, L. P., 1944: Canol: an engineering project from

road building to completed refinery. Oil and Gas J., 43, no. 15, 65-69.

17. Williams, W. H., 1951: Chemical plant operations and the weather. Chem. Engineering Progress, 47, no. 6, 277-282.

INDUSTRIAL OPERATIONS UNDER EXTREMES OF WEATHER

by

]. A. Russell; W. W. Hay; J. W. Waters; H. E. Hudson, Jr.;]. Abu-Lughod, W. J. Roberts, and J. B. Stall;

A. W. Booth; and E. F. Taylor. Edited by ]. A. Russell.

IX. THE TRANSPORTATION EQUIPMENT INDUSTRIES*

By J. A. RUSSELL

University of Illinois

(Original manuscript received 27 March 1956; revised manuscript received 7 June 1956)

ABSTRACT

The effects of weather elements on the manufacture of automobiles, aircraft, and locomotive and railway rolling stock are considered. A discussion of general weather effects on plant layout, personnel, and adminis­tration is followed by an estimate of the impact that exposure to weather would have on operation of foundry, forge shop, press plant, heat treatment, anodizing, machine shop, assembly, and rubber tire manufacture. Included also is a discussion of the effects of weather extremes on the properties of copper, aluminum, lead, tin, zinc, magnesium, nickel, and plastics.

The efficiency of the use of transportation equip­ment-automobiles and trucks, locomotives and rolling stock, and aircraft**-is directly affected by weather conditions, and, as has been noted in the introductory paper, this impact is reflected in other economic activities through its effect on material and service accumulation and product distribution. A similar interrelationship exists between the manu­facture of transportation equipment and power generation and transmission, industrial construction, and iron and steel manufacture; among the chemical industries the production impairments imposed on petroleum refining and rubber synthesis are particu­larly pertinent to the production and use of transpor­tation equipment. Information from previous papers of this monograph treating these industries should, therefore, be applied to the functioning of the me­chanical industries described here. Nevertheless, there are weather elements or combinations of weather

*This paper is condensed from reports prepared on the auto­mobile industry by Lawrence Doyle, University of Illinois and Ronald E. Lemon, Oklahoma State Development Comm.; the aircraft industry by Lawrence Doyle, Ronald Lemon, and Joseph A. Russell; and locomotive and car manufacture by William Hay, University of Illinois, and G. M. Cabbie. Data in section 5 on the properties of materials was originally prepared by J. W. Waters.

** Shipbuilding is not specifically considered in this section, although as an essentially unhoused industry in its assembly stages, it is subject to many of the impediments described here and in other papers of this monograph.

elements that impose limitations on the manufacture of transportation equipment (as well as other me­chanical industries), or under which the production of this equipment can be continued only at greatly increased capital costs for buildings and equipment or production costs in labor, maintenance, supplies, spoilage of materials and products, and the like.

As was pointed out in the introduction to this monograph, it is possible to construct buildings and other protective structures to house most of the processes described in this paper so that they could operate in conditions of extreme weather. However, certain steps in the fabrication and assembly of transportation equipment, particularly of aircraft (and ships) are normally accomplished in the open, and to house them would impose unreasonably high expense on the industry; in addition, as with other industries considered in this monograph, each process was studied under the possibility that some mis­chance had exposed the operation to outside weather. Of the thousands of operations required to transform raw materials into finished transportation equipment, only those that are conceivably weather-sensitive are included here.t

t Engineers and other officials of the following companies in the transportation equipment field were generous with material used in the original research for this paper: Ford Motor Com­pany, Boeing Airplane Co., North American Aviation, Inc.,

112

MAY 1957 ]. A. RUSSELL 113

I. Effects of weather extremes on plant layout, per­sonnel, and administration

The production of airframes (flyable aircraft) is generally more sensitive to weather extremes than automotive manufacture or locomotive and car build­ing. One of the major reasons is that much of the final inspection, modification, and testing, including flight testing, is done in the open and is subject to the full impact of weather conditions at the plant site. Flight testing, which is the final inspection of the aircraft, is particularly vulnerable to weather factors, although airframe plants have been, and still are, located in areas of very limited flying weather.

The large size of aircraft requires huge assembly rooms and exit doors; large machines, jigs, and tools with extremely close tolerances are used; and exact­ing labor performance standards give airframe pro­duction additional sensitivity to climatic extremes. It costs between 25 and 50 per cent less to build and maintain an airframe plant to function in the mild southern California climate than it does to build and maintain the same plant in more severe northeastern areas. Dependable transportation for the large, rela­tively delicate incoming subassemblies and for plant supplies such as aviation fuel, together with weather problems of constructing a plant with the required floor space, add to the sensitivity of airframe manu­facture to weather extremes. i. General plant layout. The fabrication processes for automotive, railway equipment, or aircraft manufac­ture are normally completely housed and thereby all steps, except the flight testing of aircraft, can be protected from weather conditions so long as the housing does not fail. However, extreme conditions of temperature, wind, or precipitation (particularly snow) may create the necessity for modifications in building size, design, and materials, heating and ventilating equipment, water tower and water cooling systems, smoke stacks and gaseous waste exhaust pipes, which would be so costly as to be unfeasible (see Paper Ill).

The modern industrial design practice of zoning a plant, or dividing the facility into sections that are relatively self-contained in power, water, heat, venti­lation and other service-dispensing equipment pre­vents general plant shutdown if limiting weather elements penetrate any one zone.*

Areas with permafrost present special problems of establishing the necessary foundations for the huge, Lockheed Aircraft Corp., Norfolk and Western Railway (loco­motive and car shop), Montreal Locomotive Works (Canada), General Electric Co., ElectroMotive Div. General Motors Corp., American Locomotive Company, Baldwin-Lima-Hamilton, Dav­.enport-Besler Corp.

* This practice is used primarily as a fire prevention precaution.

delicate machinery used in producing transportation equipment. Nevertheless, it is possible to build ade­quate foundations for any of these plants upon any type of land surface with the use of concrete mats or other expedients. Especially stable foundations are required for plants engaged in aircraft manufacture. Huge presses and other large machines such as skin and spar millers which must operate with close tolerances need massive footings to insure stability and to maintain alignment. The degree of precision is shown by the fact that wing and fuselage jigs are aligned optically, so that critical points of the as­sembly lines must be placed on the most stable of foundations.

The chief modification from normal plant layout that would be required in transportation equipment plants would be to provide protection for parts storage and, in aircraft manufacture, for flight line operations. After aircraft are assembled within the airframe plant, they generally are rolled into an open air flight line, where some of the assembly and interior work can be completed, where flight line testing is done, and from which testing in actual flight is accomplished. If necessary, most of these functions could be enclosed, but at least three of the necessary nonflight operations can be housed only with extreme difficulty or hazard. They are:

1. Engine run-off; within an enclosed structure this would be extremely dangerous because of fire hazard. Control of fire would be especially difficult during periods of low temperature.

2. Refueling of engines; this would be especially dangerous from the fire standpoint. If this operation were moved indoors all electric motors in the vicinity would have to be sparkproofed, and all machine and hand tools would have to be grounded.

3. Magnetic compass adjustment; this should be done in the open, or in a nonmagnetic structure.

The area occupied by flight line operations areas may amount to as much as 40 per cent of the total roofed production space of an airframe plant, and, if the operations normally accomplished on the line must be enclosed, the plant roof space would have to be increased 75 to 100 per cent. The disproportion­ate amount of inside space over outside space occupied by flight line operations is necessary because craft are spaced more widely for safety in an enclosure than they are in the open.

(1) Weather limits to operation of outside flight lines. Experience has shown that personnel who normally work in the open have a somewhat wider range of extreme temperature adaptability than those who are engaged in indoor work. In aircraft flight line opera-

114 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

tion labor efficiency is highest at temperatures be­ween 70 and 90F; at 32F labor efficiency is about 50 per cent of maximum; at OF it is approximately 15 per cent; and at -10F it is nil. High humidities and wind increase the effects of low temperature on labor efficiency. It is probable that at either high or low temperature winds in excess of 30 mph will affect outdoor labor sufficiently to warrant enclosure of operations.

However, many of the flight line operations are performed inside the plane, and portable heaters are used to maintain workable temperatures there.

Excessively high temperatures cause a sharp de­crease in labor efficiency; particularly as about 120F is approached. Efficiency is nil above 130F, and when the airframe is exposed to direct sunlight, internal temperatures within the wing and fuselage may reach that figure or higher.

The retarding effects on personnel of both high and low temperatures are greater for work on small than on large aircraft because workers in small craft are more confined and it is more difficult to arrange heating or cooling devices for such small spaces.

In practice, outdoor flight line operations have been found to be impractical at temperatures much outside the range between 32 and 100F. Electronic equipment, which is being increasingly used in aircraft, will not test properly when subject to temperatures below 32F or above 100F.

Snow and rain, except in amounts great enough to prevent personnel and materials from reaching the plant, are of minor significance. High wind is im­portant chiefly if accompanied by dust, precipitation, or low temperature. Both large and small planes have been tied down successfully in winds up to 100 mph. (2) Flight testing and field service. Flight testing is one vital operation of an aircraft plant that is entirely subject to existing weather. Therefore, a climate with the maximum number of good flying days per year is most desirable for aircraft manufacturing. In flight testing production aircraft from the assembly line many minor faults are discovered and there are some mechanical failures. Thus most test pilots do not fly in marginal weather; instrument flying is not entirely practicable because part of the test flight is instru­ment check.

Strong winds may halt flight testing. For some large craft, wind speeds of 50 mph halt testing operations; some smaller craft can take off and land in wind speeds of 50 to 60 mph, but head-on winds of 55 mph are generally considered to be about the maximum tolerable for flight testing; winds of 20 to 30 mph across the runway will halt flight testing.

Heavy snowfall, sleet, or ice lying on the runway surface will prevent flight testing until runways are cleared. Falling rain or snow is usually accompanied by low ceiling and limited visibility. Heavy craft can land and take off with as much as six inches of snow on the runway, but this is extremely hazardous. Drifts of almost any size present serious obstacles to take-off and landing.

Although flight testing can be undertaken at a wide range of temperature (it has actually been accomplished from -65 to 140F for repair testing), -40F is about the limit for production flight testing, but human efficiency is so low at that temperature that large scale production flight testing would not be effective much outside the range from 0 to 100F. Warm ground temperatures are more suitable for flight testing than are cold surface temperatures be­cause it is possible to start testing at high temperatures and carry the test through a wide downward temper­ature range by climbing to high altitude. (3) Storage of parts, tools, and materials. The neces­sity of providing protected storage space (which would add to plant size) against weather extremes for materials, parts, and components results not only from deterioration of materials (rust, chemical or physical change, etc.) but from difficulties of assem­bling separate parts made from different materials which change dimensions at variable rates when subjected to the same weather conditions. This is more critical in the aircraft industry than in the automotive and railway equipment industries, because tolerances are smaller, the lighter metals having a high coefficient of expansion are used more, and dimensions between mating surfaces are often longer in the former industry.

According to officials at one aircraft company, any material used in the manufacture of airframes could be stored outdoors in any kind of weather extreme if properly wrapped or protected. However, magnesium and certain parts such as electronic equipment are especially susceptible to damage if unprotected. Most aircraft companies store all materials, parts, and tools in completely enclosed buildings, some of which are unheated, however. Jet engines are shipped and stored in large pressurized containers to give protection against corrosion. Plaster dies are cocooned for outdoor storage and Kirksite dies may be stored outdoors. Painted jigs with grease on the contact surfaces may also be stored outdoors.

Materials and parts are brought up to normal work­ing temperature (65 to 70F) before being used. The normal production bank of materials usually affords sufficient time inside the plant for the materials to

MAY 1957 ]. A. RUSSELL 115

assume this normal working temperature. One air­frame manufacturer established through tests that " ... forty-eight hours is double the time required for the average gauge to reach room temperature ... " from OF. It required 32 hr for the largest gauge tested to come from OF to room temperature.

Electric equipment, vital to all transportation equipment, must be kept dry. Moisture in motors due to rain, snow, or even high humidity reduces the insulating resistance to unacceptable, if not unsafe, values. Electric equipment thus affected must be dried before it will pass inspection and be suitable for use.

Heavy snowfall also creates problems in connection with the outside storage of parts and materials. An estimated 10 per cent additional labor force is required at one locomotive plant to keep paths and roadways clear and remove snow from stored items about to be used. One locomotive works estimates that a 10 per cent cut in production for one or two days due to yard and interbuilding delays occurs when as much as 18 in. of snow has freshly fallen; this decrease seems a generally accepted value for plant production loss where the snowfall is 12 in. or more.

ii. Personnel. Maximum output of inside workers is achieved at about 70F, falling to 65 per cent at 40 to 45F, 50 per cent at about 30F, 25 per cent at 10F, and nil at OF. Under emergency or high morale conditions, indoor labor can be expected to work at lower tem­peratures than those indicated, but only if their tasks permit the use of the necessary clothing. In the auto­motive industry walkouts and slowdowns start if inside temperatures fall below 50F or above 95F, particularly if these are accompanied by high relative humidity. Continued hot and humid weather will result in absenteeism and in reduced output per worker. One railway car manufacturer estimated that continuous temperatures over 90F for more than two days decreased output of cars by 10 per cent; if over 100F, output decreased 25 per cent; other companies have estimated a 5 per cent loss at 90F and a 10 per cent loss at 100F. Five to ten per cent production loss is estimated when outside temperatures reach zero or less if the plant buildings cannot be heated adequately.

iii. Administration. Automobile and aircraft manu­facturing particularly require large amounts of administrative and engineering work. Inventory con­trol is vital because thousands of parts are used. Drafting, blueprinting, and other engineering shops are significant links in manufacture and planning. If the protective housing needed to safeguard records

and paper work were damaged sufficiently to permit contact with outside elements, precipitation and wind would do irreparable harm to the administrative and engineering functions.

2. Water requirements of the transportation equip­ment industry *

Large scale machining and assembly of automobiles, aircraft, and railway equipment requires water primarily for steam boilers and for cooling. Steam is used in power generation and, secondarily, for heat­ing, drying and processing. Water is used for cooling condensers, furnaces, machines, engines, and welding equipment. Process water is used in relatively small quantities for metal cleansing, pickling, electro­plating, anodizing, washing and scouring.

It has been estimated that approximately 12,000 gal of water are required to produce one light passen­ger automobile and up to 15,000 gal are needed to build a heavy car, truck, or coach. These figures include water used in all manufacturing, assembling and finishing operations. Forging and hot metal pressing are excluded, but sheet metal stamping, form rolling, grey iron casting, machining, plating, painting, testing, and assembling are all taken into consideration in arriving at the final estimates [3].

Although a comparable estimate for the aircraft industry could not be obtained, it has been pointed out that the testing of a piston-type airplane engine alone requires in the neighborhood of 50,000 to 125,000 gal of water [11].

There are a number of relevant water conservation techniques which can be used in the auto and aircraft industries if water is in short supply. A saving of 25 per cent in the automobile industry through the sub­stitution of spray for immersion rinses is reported. "Sprayed on water is far more effective and it takes just a small percentage of what it does to 'dunk' " [3]. In addition to spray rinses, another means of water conservation is recycling in closed and open systems. Solar Aircraft reports a yearly saving of $13,000 on water since the introduction of a recircula­tion unit which cools three welders at a time. From 50 to 90 per cent of the cooling water gets reclaimed in this system [19].

The large average plant size and labor force required for mass production stamping and assembling increases the dependence of the automobile and aircraft industries, particularly, upon the water supply.

*From material prepared by Janet Abu-Lughod, Illinois State Water Survey Division.

116 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

3. Effect of weather extremes on specific plant opera­tions

The foregoing sections of this paper have largely been concerned with external plant functions, and with the weather limitations that exist or modifica­tions to plant layout or practice that are required to maintain operations in areas where weather extremes occur. These are applicable to any establishment manufacturing automobiles, trucks, aircraft, locomo­tives or railway cars. The following section deals with the effects that significant weather elements would have on processes that under current practice are provided with enclosed space. So long as the protective housing is weather tight and its heating and venti­lating equipment are operating satisfactorily, these processes can be continued in any condition of weather (assuming the availability of materials, workers, and necessary facilitative services). In the following sec­tions each process has been studied under the eventu­ality that the protective housing or its weather­proofing equipment might be ineffective; results are in part speculative, but they represent the considered judgments of practicing experts in each process.

i. Foundry.*

(1) Low temperature. If temperatures approach 40F, outside air must be pre-heated before it enters the cupola. Large castings may crack if cooled too rapidly, and these must be placed in heated pits to retard loss of temperature to cold air. Heavy greases and oils for machines must be changed to lighter lubricants. Foundry operations would probably stop if exposed to temperatures of OF for 12 hr.

(2) Precipitation. Precipitation and high humidity are more critical than low temperature. Casting cannot take place if precipitation is falling on the mold, and hot metal poured into a cold mold with a high moisture content will produce an inferior product. Therefore, the maximum water content of molding sand can be only 2.5 to 3 per cent (sand is saturated at 16 per cent). The flours and clays used to bind the molding sand also have to be dry.

ii. Forge shop.

(1) Low temperature. Temperatures much below 32F would cause difficulties in the forge shop; when the presses and hammers are cold they will break rela­tively easily, and in extreme cold the bearings on mechanical presses have to be pre-heated until they attain a temperature of at least 32F. If cold forgings are being produced, heat has to be maintained at the bearings. Billets must be brought to at least 32F

* One of the firms consulted about foundry problems had operated its foundry in the open.

before they can be sheared and worked without difficulty.

(2) Wind. Associated with most forging operations is a sand blasting department for cleaning rust and scale from the metal. The sand blasting operation provides a source of particles for blowing by wind, and these cause excessive wear on the dies and bearings.

iii. Press plant. At temperatures below freezing, water condensate will freeze in the compressed air lines supplying the feeding devices for the presses. In addition structural changes occur in steel at low tem­peratures and there would be a sharp rise in the percentage of scrap. For precision die and press work the temperature should be between 60 and 100F, especially if carbide inserts are used for precision die work. '

Dies on large presses have to be lubricated to elimin­ate or reduce breakage at the points where the metal is stretched the most. It is necessary to use a very heavy oil or thick grease, usually 600 w or SAE 9Q-120, and some operations require waxes. Such heavy oils, greases, or waxes are necessary to prevent them from being squeezed out under high pressure. Lubricants of such viscosity do not flow or spread easily at normal temperatures and would be almost impossible to work with at lower temperatures.

In airframe manufacture there is much shaping and forming of parts, both for the structural frame­work and skin covering, and low temperatures impair this process. To obtain the maximum structural strength with the least amount of metal, many of the pressing and shaping operations work the metal to its fullest ductility at normal room temperature (70F); about 25 per cent of the airframe parts pro­duced are bent or stretched to the fullest capacity of the metal. The rate at which metal is work hardened as it is drawn, bent, stretched, or squeezed increases as the temperature decreases. Metal has less work­ability at low temperatures than it has at high tem­peratures. Therefore, if the plant temperature is reduced any appreciable amount (down to 40F) 5 to 25 per cent of the parts produced at normal temper­atures could not be made: either the parts would have to be redesigned so that they would require less working of the metal, or dies would have to be heated. With some metal stretching operations the dies have to be heated even at normal temperatures. This is true particularly in the forming of magnesium parts. Redesigning the dies to form the metal in steps with a suitable annealing operation between successive steps would be a possible method of preventing the metal from rupturing, but this expedient would more

MAY 1957 ]. A. RUSSELL 117

than triple costs. As the temperature decreases, the parts or operations that are normally well above the critical point become closer to the work hardening point. More parts would be affected as the temperature decreases until even the simplest shaping would be difficult. The diurnal range of temperature is a most important consideration in the airframe plant press shop. A diurnal range of approximately 30F is con­sidered to be the tolerable limit in press shop space, whereas a range of not more than 20F is considered desirable in the tool and die space of the press shop.

iv. Heat treatment. Heat treatment operations cannot be carried on if exposed directly to rain or snowfall. Precipitation will not harm the furnace, but a con­stant temperature has to be maintained usually by electric controls, which are vulnerable to moisture. Oil quenches should be protected from precipitation. Salt baths have to be protected and any stock put in them has to be dry. If a salt bath operation were exposed to precipitation it would explode. The air in the furnace has to have a humidity between 10 and 30 per cent when metal is being carburized. Moisture carried in on the metal would alter the moisture con­tent of the air and affect the process unfavorably.

v. Anodizing. Anodizing requires very close temper­ature control of the plating solution; no more than a plus or minus five degree variation from 100F is allowable. If the daily temperature range of the ambient air exceeds 40F, difficulty is encountered in controlling the solution temperature within the 10F allowable range and operating costs are increased, as ordinary equipment could not maintain the solution temperature.

vi. Machine shop. (1) Low temperature. Temperature below 40F seri­ously hinder conformance to close machining toler­ances. At temperatures below 32F special measures have to be observed to prevent the machine tool cutting fluid from freezing. Machining aluminum and· magnesium requires especially large amounts of cut­ting fluid because of the high speeds at which these metals are machined. At low temperatures the cutting fluids stiffen. However, once started the heat pro­duced in the cutting operation keeps thecutting fluid warm except at extremely low temperatures.

For general overall machining operations the operating temperature should be between 60 and 100F. Diamond boring machines require that a temperature of 65 to 68F be maintained. For machining dis­similar metals which require close tolerances, 40F is the critical low temperature. Below this temperature the necessary tolerances cannot be kept, but toler­ances required by automotive gasoline engines are

fairly wide (.0005 to .002 in.). Nevertheless, all materials to be machined are brought to room temperature.

(2) Moisture. Machining operations can be carried on exposed to moisture provided the automatic screw machines and the electric motors are kept dry. Automatic screw machines use a high grade oil with lubricating properties as a cutting fluid. For this reason the spindles etc. are not sealed in, and the cutting fluid is allowed to seep freely into the bearings. Therefore, any rain or snow on the machine would mix in with the oil and be carried into the machine.

Magnesium corrodes the most rapidly of any of the metals used in aircraft manufacture. Therefore, great care must be taken to prevent any water or even moist fingerprints from coming in contact with the metal.

vii. Assembly. Automotive, aircraft, and locomotive and car building industries use the technique of building subassemblies which are later assembled together as the finished vehicle. Both large and small components are assembled, often at distant locations, and some of these must be so precisely built that they will fit all other parts and subassemblies as required. The chief difficulties imposed by weather on the sub­assemblies are those that cause differential expansion and contraction of various metals-temperature ex­tremes and high diurnal ranges. Wind blown dust will impair the assembly of parts with highly polished surfaces, and excessive humidities or any precipitation may result in rusting. Paint shop operations are im­paired below 60F, and spot welding is difficult if exposed to precipitation. It is probably that exposure of parts storage or assembly line to weather extremes will shut down subassembly operations. Much of the work on these components is complicated and pains­taking, and the effects of high or low temperatures, combined with high relative humidity and wind, on worker efficiency are accentuated in delicate work.

Final assembly operations, particularly of auto­mobiles and railway equipment, are not affected so much by weather elements as are subassembly operations because each of the subassemblies affords a degree of protection within itself. Workers on the ass.embly line can operate very successfully wearing gloves and other protective clothing.

Final assembly of aircraft is a more demanding process than that of automobiles and trucks. Exposure to weather extremes would create virtually impossible conditions for the continued production of completed craft.

A revealing example of an assembly line under out­side conditions is provided by the car building shops

118 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

of the Norfolk and Western Railway at Roanoke, Virginia. The shops concentrate entirely on steel hopper cars for coal transportation. An unsided shed holds machinery for pressing out the car sides, etc., the shearing machines, punching machines, etc. The paint shop and storage area are outdoors. Heating consists of stoves in several shacks nearby into which the men go to rest and get warm. Natural lighting is used in daytime. During World War II, the shop operated at night under floodlights.

In addition to the naturally mild climate at Roan­oke, a principal reason for the possibility of outdoor operation is the fact that the cars are of riveted rather than welded construction. What welding is done is performed with oxyacetylene torches rather than electric arc.

This shop suffers from 2. 7 to 4.1 per cent loss in total scheduled production due to weather conditions, especially in the late fall, winter, and early spring. Tables 1 and 2 show summaries and details of this loss. It is clear that precipitation is a more serious cause of production loss at Roanoke than low tem­perature, with losses ranging as high as 70 to 100 per cent during particularly heavy rain or snow fall.

At locations with more severe weather than Roanoke it was the concensus that work could be carried on at car building shops without protection from the ele­ments only with difficulty and up to SO per cent loss in production. The car repair tracks of all United States railroads are traditionally outdoors but the small parts storage, machine (and wheel) shops, foundry, woodworking, upholstering and electrical shops are all under cover.

4. Rubber tire manufacture

The manufacture of rubber tires is essential to both automobile and aircraft. A brief statement on the

TABLE 1. Effects of weather conditions on railroad freight car production in outdoor shops

Norfolk and Western Railway Company Roanoke, Virginia

Period

I II III Total 2-1-51 2-1-52 2-1-53 2-1-51

Dates to to to to 1-31-52 1-31-53 4-30-53 4-3Q-53

Number months actual production 12 9* 3 24

Total freight cars pro-duced 3,192 2,087 613 5,892

Car production loss due to weather conditions 66 46 17 129

Per cent of production loss due to weather conditions 2.07% 2.20% 2.77% 2.19%

* Production delayed from 6--6-52 to 9-2-52 due to shortage of steel.

TABLE 2. Effects of weather conditions on railroad freight car production in outdoor shops

Date

2- 1-51 2- 2-51 2- 7-51 2-21-51 3-13-51 3-19-51 3-28-51 3-29-51 3-30-51 4- 2-51 4-10-51 9-14-51

10-24-51 12- 4-51 12-18-51

1-22-52 1-28-52 3- 3-52 3- 4-52 4-24-52 4-28-52

10- 9-52 11-20-52 11-21-52 12- 5-52

1-21-53 3- 2-53 3- 3-53 3-18-53

Total

Norfolk and Western Railway Company Roanoke, Virginia

Scheduled production

14 cars 14 cars 14 cars 14 cars 14 cars 14 cars 14 cars 14 cars 14 cars 14 cars 14 cars 12 cars 12 cars 8 cars 8 cars 8 cars 8 cars

14 cars 14 cars 14 cars 14 cars 10 cars 10 cars 10 cars 10 cars 10 cars 10 cars 10 cars 10 cars

Type of weather

Rain and ice Cold weather Rain Rain Snow Rain Rain Rain Rain Rain Rain Rain Rain Rain Sleet Rain Rain Rain Rain Rain Rain Rain Rain Rain Rain Rain Snow Rain and snow Rain

Cars lost

6 4 5 4 5 4 4 4 9 4 4 4 1 1 3 2 2 6 6 2 1 7 3 4 8 9

10 4 3

129

effects of weather and water supply on rubber tire manufacture follows.

All processes connected with the manufacture of rubber tires are completely housed under normal operating conditions. Damage to the plant structure which permits the intrusion of outside weather con­ditions will result in the same slowdowns and stoppages in machine and human operations that have been described for other mechanical industries.

Low temperature would not affect the compounding ·of either GRS type or butyl rubber. However, as workmen must handle the compounding materials and feed the compounding mills, it is necessary that the building temperature be maintained at a level at which workmen can work an eight hour shift.

Natural rubber processing requires water as a cooling medium to reduce the temperature of the rubber after vulcanization and also to maintain the temperature of the calendars and platen presses. The production of carbon black, a crucial ingredient of rubber (rubber tires contain about 1/3 lb of carbon black per pound of rubber) requires between 4 and 14 gal per lb.

Water is also used for cooling in the process of initial compounding of crude rubber, reclaimed

MAY 1957 J. A. RUSSELL 119

rubber, carbon black, and other ingredients. Temper­ature control during this process is extremely im­portant for quality. Cooling water is also required for the rolling mill of a rubber plant. The magnitude of water use, however, for this process is flexible. Sub­stantial savings may be obtained by the substitution of evaporative condensers for ordinary water cooling.

5. The effect of weather elements on the properties of certain materials that are widely used in industry * Iron and steel are essential materials in the produc­

tion of all transportation equipment. The effect of weather conditions on these is treated in Paper III, but the nonferrous metals and plastics are particularly used in the industries being considered here. Mention of them, and of iron and steel articles, is also made wherever pertinent in other sections of this paper. i. Copper. The properties of copper and copper alloys which exist under normal room conditions also seem to exist under the extreme atmospheric conditions which have been recorded upon the earth's surface. The tendency exists for the following to occur m copper with a lowering of temperatures [16]:

1. Static stress resistance increases. 2. Yield stress resistance has an upward tendency. 3. Ductility appears to be little altered. 4. Notched-bar impact resistance is undiminished

[9]. 5. Electrical conductivity decreases but never

attains supra-conductivity.

Copper and copper rich alloys show high resistance to corrosion through atmospheric exposure [8, 17]. ii. Aluminum. Evidence exists that wrought alumi­num and some aluminum alloys exhibit practically the same physical characteristics at extremely low temperatures as at normal room temperature [4, 8, 9, 16]. Aluminum has a susceptibility to corrosion in marine atmospheres although this is not evident in experience with nonmarine atmospheres [8]. iii. Lead. Data concerning the behavior of lead when exposed to the extremes of atmospheric conditions is not conclusive, but there is evidence that its properties which exist at room temperatures will also be apparent at the lowest temperatures encountered upon the earth's surface [10, 16]. Lead exhibits an extremely high resistance to corrosion [8, 10]. iv. Tin. Although tin offers good resistance to non­marine atmospheric corrosion it appears to be suscep­tible to corrosion by marine atmosphere [8]. A unique problem exists concerning the exposure of tin and tin

*From material prepared by J. W. Waters.

alloys to even moderately low temperatures [16]. At SSF a transformation begins to take place which in­volves a structural change of crystal lattice from simple tetragonal to simple cubic (i.e., from white tin to grey variety). This is accompanied by an alteration in specific gravity from 7.3 to 5.75. This change may result in complete disintegration [16]. The change, however, does not take place under natural conditions unless undercooling occurs or tin of the grey variety is present. Presence of small quantities of other metals changes both the rate of change and the temperature of its inception. The transformation can be avoided to at least - 58F if there is a 1 per cent solution of bismuth, lead, and antimony in the tin [16].

v. Zinc. Zinc exhibits a low resistance to atmospheric corrosion, especially corrosion induced by marine atmospheres [8]. Also zinc rich alloys exhibit extreme brittleness at only moderately low temperatures [16]. An abrupt decrease in notched-bar impact resistance occurs between 50 and 14F [1, 16].

vi. Magnesium. Although magnesium and magnesium alloys are not immune to low temperature increase of brittleness, the desirable properties which exist at room temperature will generally exist also at the lowest temperatures which occur on the earth's sur­face [16]. This is not particularly significant, however, since magnesium has a very low impact resistance at room temperature.

vii. Nickel. Nickel does not suffer from cold em­brittlement; there is no loss of notched-bar impact resistance with decrease in temperature [16]. This includes high nickel alloys and austenitic nickel steel and ferro-nickels which have over 45 per cent nickel [9]. Nickel is susceptible to corrosion [8], but only at very slow rate [18]. Exposed nickel fogs at approxi­mately 70 per cent relative humidity; a continual exposure to high humidity results in permanent cor­rosion. This condition can be remedied by coating the nickel with chromium [18].

viii. Plastics. Generalizations which pertain to the behavior of plastics when exposed to extremes of atmospheric conditions are not of great value quanti­tatively because of the heterogeneity of the material items which are included in the category "plastics" [7, 12] and also because usually more than one climatic element exerts a strong influence over the behavior of a plastic when it is exposed to the atmos­phere. Some of the more important mechanical and physical properties which must be quantitatively evaluated for each plastic material in terms of specific usage requirements are [2, 7]:

120 METEOROLOGICAL MONOGRAPHS VoL. 2, No.9

1.

2. 3. 4. 5. 6. 7. 8. 9.

10. 11.

Tensile, flexural, compressive, and shear strengths Stiffness and rigidity Ductility Impact resistance Creep and stress endurance Fatigue characteristics Dimensional stability Abrasion resistance Stability of electrical characteristics Stability of optical characteristics Stability of thermal characteristics

The weather elements which most affect the behavior of these properties are temperature, humid­ity, and sunlight. A qualitative description of the effect of these elements upon plastic materials follows. (1) Temperature. The range of temperatures to which any material might possibly become exposed as the result of extreme conditions of the surface atmosphere is very great. For some purposes [2] a range of -60 to 160F is considered routine since metal equipment standing in the sun can easily become that hot. Generally, the temperature range within which the properties of materials remain relatively constant is much narrower for plastics than for metals.

Significant changes that occur in the stress-strain relationship, as the ambient temperature varies, follow [2]:

1. As temperature decreases "brittleness" in­creases.

2. Magnitude of the maximum stress at yield point changes. It decreases as the temperature increases and it increases as the temperature de­creases. However, at very low temperatures the ductility may be so low that rupture would occur well down on the linear portion of the stress-strain curve before the maximum potential stress can be attained.

3. The point of rupture tends to move along the stress-strain curve toward higher values of strain as the temperature increases, or toward lower values as the temperature decreases.

When exposed to low temperatures, organic plastics undergo changes which may be temporary (reversible) or permanent (irreversible). Reversible effects usually include dimensional changes due to thermal contrac­tion and loss of moisture, increased modulus of elasticity, increased yield and ultimate strengths, decreased ductility, and most frequently, although not in every case, decreased resistance to impact. Irreversible effects may include dimensional changes due to change in state, physical failure due to lack of

sufficient ductility to respond to dimensional changes, crystallization, and freezing of plasticizers or of absorbed water [14]. Thus a prolonged exposure to subzero temperatures has relatively little effect on the strength properties of most plastics unless crack­ing or checking or crazing occurs, or unless a slowly­reversible crystallization takes place [2]. Because the linear shrinkage of plastics is generally consider­ably greater than that of metals, problems exist in designing items in which .combinations of these two must sustain atmospherically induced volumetric changes. In some instances a temperature differential of as low as 18F may influence the choice of one material over another. That the problem of differential thermal contra-ction ratios can be overcome is demon­strated in polystyrene which possesses a very low coefficient of thermal contraction combined with excellent dimensional stability [ 14].

The electrical properties of plastics may vary con­siderably with temperature so that use conditions must be considered carefully in choosing a plastic insulation material [5]. Generally, however, plastics are good insulators of both heat and electrical energy.

In plexiglass forming, low temperature causes chill lines to form when the hot plexiglass is taken from the furnace; plexiglass has been formed at SOF, but with many difficulties; the ideal temperature is be­tween 70 and 80F. One estimation was that at 28F there would be a 50 to 60 per cent efficiency loss in the plexiglass operation.

A highly significant problem exists in the behavior of elastomers at low temperatures (i.e., plastics in which the rubber-like property is desirable). Experi­ence has shown that at temperatures high enough to produce a Young's modulus of 10,000 lb per sq in., plastic rather than rubber-like properties predominate in this type of material. Consequently the temperature at which a given material reaches this strength is used as a low temperature serviceability index. For a natural rubber gum compound this is about -67F whereas a ~imilar GRS compound (i.e., a synthetic rubber) reaches this strength at -58F [13]. Prior to World War II very little was known concerning the behavior of elastomers at low temperatures because the only well-known one (natural rubber) retained its flexibility over a wide range of temperatures to -70F or even lower [13]. The change in property of a plastic from elastic to brittle has not been explained to the satisfaction of all workers in the field [6]. This temperature of transition can be altered in elastomers within limits by varymg the type and amount of plasticizer [14]. (2) Humidity. Temperature alone is not the only major factor responsible for the behavior of plastic

MAY 1957 J. A. RUSSELL 121

materials in variable atmospheric conditions. Many organic plastics are hygroscopic in some degree. Normal seasonal variations in the moisture content of the atmosphere are large and will produce large variations in the moisture content of exposed hygro­scopic materials. Water acts as a powerful plasticizer for many plastics, and tends to reduce strength and modulus, but to increase ductility and toughness [2]. Where both temperature and relative humidity are changed, the effect on strength may be even more pronounced [2].

At low humidity hygroscopic plastics tend to be­come brittle, shrink, have greater dimensional stability under load (i.e., creep), and have less impact resistance and greater strength [6]. In all cases the desirable atmospheric condition is constancy of both temper­ature and humidity, since most plastics can be designed for any specified humidity, but only a few for highly variable humidities.

(3) Sunlight. Continuous exposure to light will cause chemical change in almost any organic material, including plastics. The ultraviolet part of the spectrum is especially active in this respect. The change may vary in kind and severity from slight yellowing to complete disintegration. The principal effects of irradiation on mechanical properties are linked with the chemical degradation of the polymeric compound, appearing as reduced strength, reduced ductility, and increased fragility. No general rules of behavior have been formulated. Each plastic must be studied individually to determine its sensitivity to degrada­tion by light [2].

(4) Oxidation. Like all organic materials, plastics are subject to oxidation. High temperature and light accelerate the effects, but over long periods of time oxidation can take place even at room temperature. Natural rubber is notoriously subject to oxidation with resultant stiffness and embrittlement, and eventual loss of strength and elasticity. In the main, synthetic elastomers are more resistant to oxidation than rubber, some sufficiently so that they cannot be evaluated adequately by tests used for natural rubber. Rigid plastics are, in general, resistant to oxidizing agents under mild conditions [2].

REFERENCES

1. Anderson, E. A., 1946: The corrosion of rolled zinc in the outdoor atmosphere. Symposium on Atmospheric Exposure Tests on Non-Ferrous Metals, A.S.T.M., 2-15.

2. Carswell, T. S. and H. K. Nason, 1944: Effect of environ­mental conditions on the mechanical properties of organic plastics. Symposium on Plastics, A.S.T.M., p. 22.

3. Danse, L. A., 1952: General Motors Corp., Conservation Conference. Michigan Department of Conservation, Hig­gins Lake, Michigan.

4. Dix, E. H., Jr. and R. B. Mears, 1946: The resistance of aluminum-base alloys to atmospheric exposure. Sympo­sium on Atmospheric Exposure Tests on Non-Ferrous Metals, A.S.T.M., 57-75.

5. Field, R. F.: The Behavior of Dielectrics over Wide Ranges of Frequency Temperature and Humidity. Cambridge, Mass., General Radio Company.

6. Findley, W. N., 1953: Plastics, their mechanical behavior and testing. Applied Mechanics Review, 6, 49-53.

7. Findley, W. N.: Department of Theoretical and Applied Mechanics, University of Illinois. Statement to the author.

8. Finkeldey, W. H., 1934: The early interpretation of test results in the atmospheric corrosion of non-ferrous metals and alloys. Symposium on the Outdoor Weathering of Metals and Metallic Coatings, A.S.T.M., p. 86.

9. Gillett, H. W., 1941: Impact Resistance and Tensile Properties of Metals at Sub-atmospheric Temperatures. Philadelphia, Project No. 13 of the joint A.S.M.E. and A.S.T.M. Re­search Committee on Effect of Temperatures on the Properties of Metals, p. 105.

10. Hiers, George 0., 1946: The use of lead and tin outdoors. Symposium on Atmospheric Exposure Tests on Non-Ferrous Metals, A.S.T.M., 46-55.

11. Jordan, Harry, 1946: Industrial requirements of water. J. Amer. Water Works Assoc., 38, part 1, 65-68.

12. Kline, G. M., 1944: Introduction to summary of properties, uses and salient features of families of plastics. Symposium on Plastics, A.S.T.M., p. 136.

13. Liska, John W., 1950: Low temperature properties of elas­tomers. Symposium on Effects of Low Temperature on the Properties of Materials, A.S.T.M., p. 37.

14. Nason, H. K., T. S. Carswell and C. H. Adams, 1950: Low temperature behavior of organic plastics. Symposium on Effects of Low Temperature on the Properties of Materials, A.S.T.M., p. 3.

15. Olchoff, Maurice, 1950: Conservation program halves water cost. Factory Management and Maintenance, 108, part 2, 120-121.

16. Teed, P. L., 1950: Properties of Metallic Materials at Low Temperatures. Chapman and Hall, pp. 98, 111.

17. Tracy, A. W., 1946: Resistance of copper alloys to atmos­pheric corrosion. Symposium on Atmospheric Exposure Tests on Non-Ferrous Metals, A.S.T.M., p. 43.

18. Wesley, W. A., 1946: The behavior of nickel and monel in outdoor atmospheres. Symposium on Atmospheric E;x­posure Tests on Non-Ferrous Metals. A.S.T.M., p. 16.

19. Wolfington, Del, 1951: Saving $13,000 a year on water. Factory Management and Maintenance, p. 85.

METEOROLOGICAL MONOGRAPHS

Vol. 1, No. 1. Wartime Developments in Applied Climatology by W. C. Jacobs. August, 1947. $1.00

No. 2. The Observations and Photochemistry of Atmos­pheric Ozone and Their Meteorological Significance by R. A. Craig. September, 1950. $2.50

No. 3. On the Rainfall of Hawaii: a group of contributions by L. B. Leopold; H. Landsberg; C. K. Stidd and L. B. Leopold; T. C. Yeh, C. C. Wallen, and J. E. Carson; and T. C. Yeh, J. E. Carson, and J. J. Marciano. June, 1951. $2.50

No. 4. On Atmospheric Pollution: a group of contributions by J. H. Carter, C. A. Gosline, E. W. Hewson, H. Landsberg; M. L. Barad; G. W. Brier; W. C. L. Hemeon; P. H. Lowry; P. H. Lowry, D. A. Mazzarella, M. E. Smith; H. F. Poppendiek; H. Rouse; R. H. Sherlock; M. E. Smith. November, 1951. $4.50

No. 5. Forecasting in Middle Latitudes by H. Riehl; and J. Badner; J. E. Hovde; N. E. La Seur; L. L. Means; W. C. Palmer; M. J. Schroeder; L. W. Snellman; and others. June, 1952. $8.50

Vol. 2, No. 6. Thirty-Day Forecasting: a review of a ten-year ex­periment by Jerome Namias. July, 1953. $8.50.

No. 7. The jet Stream by H. Riehl, M. A. Alaka, C. L. Jordan, and R. J. Renard. August, 1954. $3.50.

No. 8. Recent Studies in Bioclimatology: a group by C. W. Thornthwaite and J. R. Mather; W. G. Wellington; J.D. Findlay; L. P. Herrington; H. F. Blum; C. Monge M.; G. and B. Duell; F. Sargent, II; H. Landsberg; K. Buettner; J. M. May; J. H. Foulger. Edited by F. Sargent, II and R. G. Stone. October, 1954. $5.00.

No. 9. Industrial Operations under Extremes of Weather by J. A. Russell; W. W. Hay; J. W. Waters; H. E. Hudson, Jr.; J. Abu-Lughod, W. J. Roberts, and J. B. Stall; A. W. Booth; and E. F. Taylor. Edited by J. A. Russell. May, 1957. $6.00.

Orders for the above publications should be sent to: THE AMERICAN METEOROLOGICAL SOCIETY

3 JOY ST., BosTON 8, MASS.

Continued from Cover 2

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