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IS 13736-2-1 (1993): Classification of environmentalconditions, Part 2: Environmental conditions appearing innature, Section 1: Temperature and humidity [LITD 1:Environmental Testing Procedure]

IS 13736 ( Part 2/Set 1 ) : 1993 IEC Pub 721-2-l ( 1962 )

WJWT 1 8TWTq 8-k 8l’TiFi’T

Indian Standard

CLASSIFICATION OF ENVIRONMENTAL CONDITIONS

PART 2 ENVIRONMENTAL CONDITIONS APPEARING IN NATURE

Section 1 Temperature and Humidity

UDC 621.38.038 : 620.193.23

@ BIS 1993

BUREAU OF INDIAN STANDARDS MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

October 1993 Price Gronp 11

Environmental Testing Procedures Sectional Committee, LT 02

NATIONAL FOREWORD

This Indian Standard, which is identical with IEC Pub 721-2-l ( 1982 ) ‘Classification of environ- mental conditions - Part 2 : Environmental conditions appearing in nature, temperature and humidity’, issued by the International Electrotechnical Commission, was adopted by the Bureau of Indian Standards on the recommendation of the Environmental Testing Procedures Sectional Committee ( LTD 02 ) and approval of the Electronics and Telecommunication Division Council.

The text of the IEC standard has been approved as suitable for publication as Indian Standard without deviations. Certain conventions are, however, not identical to those used in Indian Standards. Attention is particularly drawn to the following:

Wherever the words ‘International Standard’ appear, referring to this standard, they should be read as ‘Indian Standard’.

The concerned technical committee has reviewed the provisions of IEC 721-1 ( 1981 ), referred in this standard and has decided that they are acceptable for use in conjunction with this standard.

Part 1 of this Indian Standard deals with classification of environmental parameters and their severities. The subsequent parts are intended to deal with the following:

a) Environmental conditions appearing in nature

b) Classification of groups of environmental parameters and their severities

Amendment No. 1 issued to IEC Pub 721-2-1 ( 1982 ) is given at the end.

Only the English language text in the International Standard has been retained while adopting it in this Indian Standard.

IS13736( Part YSec 1):1993 IEC Pub 721-2-l(1982) -

Indian Standard

CLASSIFICATION OF ENVIRONMENTAL CONDITIONS

PART 2 ENVIRONMENTAL CONDITIONS APPEARING IN NATURE

Section 1 Temperature and Humidity

1. Scope

This part of the standard presents types of open-air climate in terms of temperature and humidity. It is intended to be used as part of the background material when selecting appro- priate temperature and humidity severities for product applications.

The climates cover all areas of the world, excluding the Central Antarctic and high altitudes (above 5 000 m).

This presentation may be used as background material when issuing climatic environ- mental classes for product applications.

When selecting temperature and humidity severities for product applications, the values given in I EC Publication 721-l: Part 1: Classification of Environmental Parameters and Their Severities, should be applied.

2. Object

To define a limited number of types of open-air climate, in terms of temperature and humidity, which satisfactorily represent the conditions most frequently met by products while being transported, stored, installed and used.

3. General

Electrotechnical products are used in almost all areas of the world under varying climatic conditions and have to meet the stresses imposed by severe climatic: conditions with the neces- sary reliability. A Jetailed knowledge of the climatic conditions to which the product will be subjected must be available in the design stage.

Data on open-air temperature and humidity have been collected and statistically processed for many years throughout the whole world. Such data can be conveniently represented in climatograms.

In addition to the open-air temperature, the temperature stresses on a product depend on a number of other environmental parameters, for example solar radiation, air velocity, heating from adjacent equipment, etc.

The effects of humidity depend on temperature, temperature changes, impurities in the humid air, etc.

In many cases the extremes of temperature and humidity are of great importahce even if they occur a short time only during the day. In other cases, where large time constants for heat or water penetration are involved, the mean values of temperature and humidity over a cer- tain period may be more important.

1

IS 13736 ( Part 2/Set 1) m: 1993 IEC Pub 721-2-l(1982)

It has therefore been considered useful to present here both the-mean value over many years of the annual extreme values of temperature and humidity, which will occur only for short periods (a~few hours), and the mean value over many years of the extreme daily mean values of temperature and humidity, which will occur for longer periods.

In order to cover cases where rare events have to be taken into account, the absolute extreme temperatures and humidities, observed over a period of many years, have also been presented.

This standard does not take into account reliability aspects and therefore only the extreme values of temperatures and humidities and combinations thereof are given. For reliability purposes it is also necessary to have information on the total statistical distribution on tem- peratures and humidities. Such data may also be needed when considering the diffusion of moisture through materials.

4. Principles behind the presentation of statistical data of temperature and humidity

4.1 Statistical open-air climates

For the application of a product in a locally restricted geographical area, the open-air tem- perature and humidity can be taken from the statistical climatogram for that area. This per- mits the product to be designed for its application in this climate.

The different open-air temperature and humidity conditions of the world are therefore pre- sented by defining a limited number of climatic types, hereinafter referred to as “statistical open-air climates”, covering the climatic conditions of the world.

4.2 Groups of statistical open-air climates

For the application of a product in several geographical areas with different climatic types, the appropriate statistical open-air climates are brought together in four main groups.

The restriction to four groups is made in order to limit the temperature and humidity classes applied to products intended for a more general use.

5. Presentation of statistical open-air climates

5.1 Environmentalparameters

In this presentation, statistical open-air climates are defined by the values of the following environmental parameters:

- air temperature;

- relative air humidity.

The relative humidity at a certain temperature is defined as the ratio between the actual vapour pressure and the saturation vapour pressure at the same temperature.

At a fixed air pressure the absolute air humidity, defined as the actual mass of water per unit of air volume, is given by the air temperature and the relative air humidity.

IS 13736 (Part 2/Set 1) : 1993 IEC Pub 721-2-l(1982)

5.2 Climatograms

5.2.1 General

The climatograms presented in Figures 1 to 9, pages 18 to 26, define limits of statistical open-air climates. Three boundary lines are given in the diagrams, one defining the mean value of the annual extreme daily mean values, the second defining the mean value of annual extreme values and the third defining the absolute extreme value.

5.2.2 Boundary lines representing the mean value of the annual extreme daily mean values of tem- perature and humidity

The boundary lines representing the mean value of the annual extreme daily mean values are obtained by plotting for each day the mean value of air temperature and associated rela- tive humidity occurring at one place representative of the geographical area, in a diagram with air temperature on the x-axis and relative air humidity on the y-axis. A boundary line is then drawn through the extreme plots appearing in the diagram.

The boundary line in a climatogram is the mean line between the boundary lines obtained by the procedure for each of many years (at least ten years). The boundaries have been slightly simplified so that they are kept parallel to constant air temperature, constant relative air humidity or constant absolute air humidity.

The probability is rather high (about 5%) that a product will, for short periods (a few hours per occasion), be subjected to temperatures and humidities and combinations thereof which are more extreme than those represented by the boundary lines. However, if a long-term expo- sure is needed for the product to attain the temperature of the surrounding air, it is unlikely that the product will be affected by these short-period exposures to more severe temperature conditions than those represented by the boundary lines.

5.2.3 Boundary lines representing the mean value of annual extreme values of temperature and humidity

The boundary lines representing the mean value of annual extreme values are obtained by plotting all values of air temperature and associated relative humidity during one year, occurring at done place representative of the geographical area, in t!-e same diagram as in Sub- clause 52.2. A boundary line is then drawn through the extreme plots appearing in the diagram.

The boundary line in a climatogram is the mean line between the boundary lines obtained by the procedure for each ofmany years (at least ten years). The boundaries have been slightly simplified so that they are kept parallel to constant air temperature, constant relative air humidity or constant absolute air humidity.

Although the extreme boundary values of air temperature, relative air humidity and abso- lute air humidity, which can be read from the diagrams, do not exactly represent the mean value of the annual extreme values, this can be assumed for the practical use of the climato- grams.

The probability of a product being exposed to combinations of air temperatures and rela- tive~air humidities outside the boundary line deoends on for how long the product is exposed to open-air conditions. A product which is permanently placed outdoors for several years can be expected to be temporarily exposed to more extreme air temperatures and more extreme combinations of air temperatures and relative humidities than those indicated by the bound- ary line.

If a product is exposed to open-air conditions for shorter periods only, the probability is small that the product will be subjected to more extreme air temperatures and humidities than those given by the boundary lines.

IS 13736 ( Part Z/Set 1) : 1993 IEC Pub 721-2-l(1982)

The annual extreme value of low temperature normally occurs for a period of approxi- mately 10 h, whilst the annual extreme value of high temperature normally occurs for a shorter period, approximately 5 h. The statistical occurrtilce could therefore be taken as approximately 0.1% for the low temperature value and approximately 0.05% for the high tem- perature value.

5.2.4 Boundary lines representing the absolute extreme value of temperature and humidity

The boundary lines representing the absolute extreme value are obtained by plotting all values of air temperature and associated relative humidity during many years (more than ten years), occurring at .one place representative of the geographical area, in the same diagram as in Sub-clause 5.2.2. A boundary line is then drawn through the extreme plots appearing in the diagram. The boundary line in a climatogram representing the absolute extreme value is then identical to this line.

The boundaries have been simplified so that they are kept parallel to constant air tempera- ture, constant relative air humidity or constant absolute air humidity.

The absolute extreme values which occur very seldom and for short periods only are included for special applications, for example, the efficient operating of devices for telecom- munication under worst-case conditions.

5.3 Identification of the statistical open-air climates

The following tables present the types of climate defined as the statistical open-air climates.

In Table I the mean value of the annual extreme daily mean values of temperature and humidity is given for each type of climate. In Table II the mean value of annual extreme values of temperature and humidity is given for each type of climate. In Table III the absolute extreme value of temperature and humidity~is given for each type of climate.

All figures are based on observations over a period of not less than ten years. An increase in the observation period may result in wider extremes in Table III.

TABLE I

Types of climate by extreme daily mean values

Mean value of the annual extreme daily mean values of temperature and humidity

Type of climate Highest Chmatograms

Low High temperature Highest are given

temperature temperature with absolute ,humidity

in Figure

r.h. L 95%

Extremely Cold (except the Central Antarctic)

Cold Cold Temperate Warm Temperate Warm Dry Mild Warm Dry Extremely Warm Dry Warm Damp Warm Damp, equable

(“C) (“C) (“C) (gsm -3)

-55 +26 +I8 14 1

-45 +25 +13 12 2 -29 +29 +I8 15 3 -15 +30 +20 I7 4 -10 +35 +23 20 5

0 +35 +24 22 6 +8 +43 +26 24 I

+12 ’ +35 +28 27 8 +17 +33 +31 30 9

15 13736 ( Part 2/Set 1) : 1993 IEC Pub 721-2-lf1982)

TABLE II

Types of climate by annual extreme values

Type of climate

Extremely Cold (except the Central Antarctic)

Cold Cold Temperate Warm Temperate Warm Dry Mild Warm Dry Extremely Warm Dry Warm Damp Warm Damp, equable.

Mean value of the annual extreme values of temperature and humidity

Low High temperature temperature

(“C) (“C)

-65 +32

-50 +32 -33 +34 -20 +35 -20 +40

-5 +40 +3 +55 +5 +40

+13 +35

TABLE III

Highest temperature

with r.h. 195%

Highest l-l Climatograms

absolute are given

humidity in Figure

(“Cl (g- m-‘)

+20 I7 I

+20 18 2 +23 20 3 +25 22 4

Types of climate by absolute extreme value

Type of climate

Extremely Cold (except the Central Antarctic)

Cold Cold Temperate Warm Temperate Warm Dry Mild Warm Dry Extremely Warm Dry Warm Damp Warm Damp, equable

r Low

temperature

Highest High temperature

temperature with r.h. 195%

(“C)

-75

(“C) (“C)

+40 +24

-60 +40 -45 +40 -30 +40 -30 +45 -15 +45 -10 +60

0 +45 +4 +40

Highest absolute humidity

(g. m-3)

Absolute extreme value of temperature and humidity

r ( Zlimatograms

are given in Figure

20 I

+27 22 2 +28 25 3 +2s 25 4 +30 27 5 +31 30 6 +31 30 7 +35 36 8 +37 40 9

The climatograms for the statistical open-air climates are given in Figures 1 to 9, pages 18 to 26.

5.4 Grouping of Statistical Open-Air Climates

The Statistical Open-Air Climates are grouped into four groups, identified as below:

4

b)

4

dl

Restricted Open-Air Climates limited to the Warm Temperate Climates;

Moderate Open-Air Climates including Cold Temperate, Warm Temperate, Warm Dry and Mild Warm Dry Climates;

General Open-Air Climates Including all Statistical Climates except Extremely Cold and Extremely Warm Dry Climates;

World-Wide Open-Air Climates including all Statistical Climates.

5

IS 13736 ( Part 2lSec 1) : 1993 mc Pub 721-2-l(1982)

In Table IV the mean value of the annual extreme daily mean values of temperature and humidity is given for each group of climates. In Table V the mean value of the annual extreme values of temperature and humidity is given for each group of climates. In Table VI the abso- lute extreme value of temperature and humidity is given for each group of climates.

TABLE IV

Group of climates by extreme daily mean values

Mean value of the annual extreme daily mean values of temperature and humidity

Group of climates

Restricted Moderate General World-Wide

-Low /Highest

High temperature Highest

temperature temperature with absolute

r.h. 195% humidity

(“C) (“C) (“C) (g a m-s)

-15 +30 +20 17 -29 +35 +24 22 -45 +35 +3t 30 -55 +43 +31 30

TABLE V

Group of climates by annual extreme values

Mean value of the annual extreme values of temperature and humidity

I 1

Group of climates

Low High temperature temperature

TABLE VI

T

Highest temperature

with r.h. 195%

Highest absolute humidit:

(“9 (g. m-9

+25 22 +21 25 +33 36 +33 36

Group of climates by absolute extreme value

I Absolute extreme value of temperature and humidity

I I I I

Group of climates

Low High temperature temperature

I .

Highest temperature

with r.h. h 95%

Highest absolute humidity

I I (“C) I (“C) I (“C) (g. m-3) I I I

I 1 I Restricted Moderate General World-Wide

-30 +45 -45 +45 -60 +45 -75 +60

+28 25 +31 30 +3-l 40 +37 40

I I I I I

6

IS 13736 ( Part 2/Set 1) : 1993 IEC Pub 721-2-l(1982)

Absolute air humidity g-m-3

‘:7’: Y TWN 000 OQbb

7 0

-7; bo 0

77’; NrnLn

f xxz 7 777 0 - Nrnul - NC7 Lo

1W 8

Mean value of the annual

Mean value of annual extreme values

-80 _jo

FIG. 1. -

-40 -30 -20 -10 0 10 20 30 40 50 69

Airtemperature “C

Statistical open-air climate. Extremely Cold (except the Central Antarctic).

IS 13736 ( Part t/Set 1) : 1993

IEC Pub 721-2-l(1982)

Absolute atr humldlty gem-3 “7” N NcyN .y I 7-Y -7

100

90

80

70

ap 60.

g 0 E .z L 50 m

5 5 B

40

30

20

Mean value of annual extreme values

-80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60

Air temperature “C

FIG. 2. - Statistical open-air climate. Cold.

IS 13736 ( Part 2/set 1) : 1993 IEC Pub 721-2.l(1982)

-80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60

Alrtemperature “C

FIG. 5. - Statistical open-air climate. Warm Dry.

11

IS 13736 ( Part t/Set 1) : 1993 IE :C Pub 721-2-l(1982)

I t

_

_

_

z _ _ _ _ I _ _ t _ _ _ \ _ . > _

\

1 ___ \- \ Y

\ \

\ ---

-80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40

Air temperature “C

FIG. 6. - Statistical open-air climate. Mild Warm Dry.

12

IS 13736 (Part 2/Set 1) : 1993 IEC Pub 721-2-l(1982)

Absolute air humldlty g-m-3 mc?p? N N”” 7 7-Y ‘;

80

xtreme values

I

Air temperature “C

FIG. 7. - Statistical open-air climate. Extremely Warm Dry.

13

IS 13736 ( Part Z/Set 1) : 1993 IEC Pub 721-2-l(1982)

Absolute arr humldlty g.m-3

80

AIM temperature “C

FIG. 8. - Statistical open-air climate. Warm Damp.

14

IS 137-36 ( Part Z/Set 1) : 1993 IE(I: Pub 721-2-l(l982)

Absolute air humidity gem-3

“:TT N NNN 7 7;; 000 bbbb 0 00 0 -7TC - L;cc - cumm 7 hlml.0 ;- xxz 7 Nrn U-J

Mean value of the annual -extreme daily mean values

-80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60

Air temperature “C

FIG. 9. - Statistical open-air climate. Warm Damp, equable.

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IS13736( Part2/Secl): 1993 IEC Pub 721-2-l(1982)

IEC 721-2-1

AMENDMENT No.1

December I987

Page 2

5. Presentation of statistical open-air climates

5.1 At the end of this sub-clause, add thefollowing note:

Note. - The basic constitutional diagram for humid air is described in Appendix B.

Add thefollowing new sub-clause:

5.5 Geographical survey~of statistical open-air climates

A survey of the occurrence of statistical open-air climates in geographical a:eas of the world is presented in two coloured maps in Appendix A.

After page 17 add the following new appendices A and B:

APPENDIX A

GEOGRAPHICAL SURVEY OF STATISTICAL OPEN-AIR CLlMATES

Al. Scope

This appendix presents a survey of the occurrence of statistical open-air climates in geo- graphical areas of the world.

The presentation consists of two coloured maps, one referring to types of climate and combinations thereof, and the other referring to groups of climates. Types of climate and groups of climates are defined in Sub-clauses 5.3 and 5.4.

A2. Object

To show the occurrence of statistical open-air climates in geographical areas of the world by using different colours to distinguish each type of climate or group of climates.

The coloured maps enable the user of this standard to obtain a general survey of the geo- graphical distribution of open-air climatic conditions most frequently met by products while being stored, transported, installed and used.

IS 13736 ( Part Z/See 1) : 1993 IEC Pub 721-2-l(1982)

A3. General

Basic information for the layout of the maps concerning statistical open-air climates and their geographical distribution has been obtained from:

- the summary of replies to a questionnaire on application of statistical open-air climates to geographical areas, sent to all National Committees,

- meteorological data which have been collected from meteorological services all over the world for 20 years, and which have been evaluated by meteorologists and engineers.

A4. Presentation of open-air climates

A4.1 General considerations

Each type of climate, or each group of climates, as marked by a certain colour, is character- istic of the climatic conditions in the area concerned.

The geographical transition from one climate to another is not of a distinct shape. Furthermore, there are large areas where the severities of one type of climate are exceeded and where the combination of two types of climate meets the rra\ situation in a better way. For this reason, combinations of two types of climate are given and marked where necessary.

Precise data for any location within a marked geographical area should be obtained from the local meteorological services.

A4.2 Markings applied in both maps

Fields with narrow hatching mark altitudes greater than 2000 m above mean sea level. The climates of these areas are colder than the climates shown for the areas in the vicinity but generally have the same characteristics.

Dotted fields are used to mark areas with a distinct seasonable alternation between two contiguous climates (alternating climate in the figures), especially between Warm Damp and Warm Dry types of climate.

Fields with a broad hatching distinguish areas with periodically extreme climatic colrcli- tions of temperature and humidity (hygrothermic area in the figures). These are mainly restricted to the combined Warm Damp/Mild Warm Dry types of climate but may also be found in the Extremely Warm Dry type of climate.

A4.3 Map representing types qfclimate (Figure A 1)

One colour is used to represent one type of climate, or a combination of two types of climate where necessary.

The combination of two types of climate means that the climate occurring in this geo- graphical area is a mixture of the two types of climate concerned. In these areas, the severities of both types of climate are essential for product design, building construction, testing, etc.

Table Al lists the types of climate and combinations thereof, marked on the map with a certain colour.

A4.4 Map representing groups of climates (Figure A2)

For the presentation of the groups of climates the same system is used as in Sub-clause 5.4, that is the more comprehensive group includes the less comprehensive one.

2

IS 13736 (Part 2/Set 1) : 1993 IEC Pub 721-2-l(1982)

Therefore, an additive system is applied for the colouring of the map. This means that the total geographical area covered by a group of climates is marked by:

- one colour for Restricted Open-Air Climate,

- two colours for Moderate Open-Air Climates,

- three colours for General Open-Air Climates,

- four colours for World-wide Open-Air Climates.

TABLE AI

Types of Open-Air Climate and combinations thereof

Type of Open-Air Climate

Designation Symbol

Combination of two types of Open-Air Climate

Designation Symbol Included in group of Open-Air Climates

Extremely Cold (except the Central Antarctic)

EC

Cold C

Cold Temperate CT

Warm Temperate WT

Warm Dry WDr Warm dry/ Cold Temperate

WDr/CT

Restricted

Moderate

Mild Warm Dry MWDr Mild Warm Dry/ Cold Temperate

Mild Warm Dry/ Warm Temperate

MWDr/CT

MWDr/WT

Moderate

Moderate

Extremely Warm Dry

Warm Damp

EWDr

WDa Warm Damp/ Cold Temperate

Warm Damp/ Mild Warm Dry

WDa/CT

WDa/MWDr

General

General

Warm Damp, equable WDaE Warm Damp, equable/ Mild Warm Dry

WDaE/MWDr General

3

1s 13756 ( I’m-t Z/Set 1) : -1993 IEC Pub 721-2-l(1982)

APPENDIX B

CONSTITUTIONAL DIAGRAM FOR HUMID AIR

B 1. General

This appendix describes the constitutional diagram as applied in the publications of IEC Technical Committee No. 75. The diagram shows the relationship between temperature and humidity at normal atmospheric pressure (~Figure Bl) and is based on the set of formulae given in Clause B3. It should be noted that the set of formulae (2) and (3) is one of several sets of approximate formulae for this relationship.

It is recommended that the diagram be applied as far as possible in work with classification or evaluation of environmental conditions.

B2. Application

The constitutional diagram may be used to specify the climatic environment, for example when establishing climatograms. It may also be used for determining the absolute humidity of air at a certain temperature and relative humidity, or for determining the dew point at a drop of temperature. For exact values, reference should be made to more detailed diagrams or mathematical calculations.

B3. Description

The diagram (Figure Bl) has three scales as follows:

a,J absollrte air humidity in grams per cubic metre is given on the scale along the top horizontal axis,

b) relative air humidir_yin percent is given on the scale along the left vertical axis,

c) air temperature in degrees Celsius is given on the scale along the bottom horizontal axis. This scale also applies when determining the dew point. that is the temperature at a relative humidity of 100% at which condensation occurs.

The relationship between relative humidity in percent, temperature in degrees Celsius and absolute humidity (water content) in grams per cubic metre is given by the curves of the diagram.

Theses curves are based on the following formulae.

The absolute humidity (water content) e is a linear function of the density of water vapour at 0 “C and 1 Pa, of the temperature and of the water vapour pressure:

Q (t,cp) = 0.007932 t :‘2’;:4 6 - e. (p/l00

e- q/100 or simplified: e(t,cp) = 2.167 t + 2,3 16 g/m3 (1)

where:

e is the saturation water vapour pressure, in pascals cp is the relative humidity, in percent I is the temperature, in degrees Celsius

The saturation water vapour pressure, e, has been calculated using the following formulae, given in Linke-Baur: Meteorologisches Taschenbuch, II. Band, 2. Auflage, Leipzig 1970, Page 476, Table 46, modified by a factor of 100 to account for the use of the pressure unit Pascal in place of millibar. To simplify the formulae, the absolute temperature Tin kelvins, where T- t + 273.16, has been introduced.

IS 137% (Part YSec 1) : 1993 IEC Pub 721-2-l(1982)

The following formulae. apply, for thermodynamic equilibrium:

- with liquid water, e,, for temperatures above 0 9c, - with ice, ei, for temperatures equal to or below 0°C.

e,(T) = 100.lOn

where:

n- -1.90298 (

373.16 373.16 - -1 + 5.028081og -

T ) T

+8.1328.10-3iI0 -3'49'49(F-t)-l~ +log1013.246

ei(T) = 100. 10m

(2)

(3)

where:

m=-9.09718(?-I)-3.56654log F +0.876793(1-&)+log6.107,4

B4. Example

An example of application is given in Figure B2.

- To find the absolute humidity at the low air temperature and high relative humidity of Class 3-K2 of climatic conditions of IEC Publication 72 I-3-3:

Starting at relative humidity of 75% on the vertical scale and at + 15 “C on the bottom horizontal scale, a point of intersection X is reached. Following a curve upwards and parallel to the curve for constant absolute humidity closest to this point, the top horizontal scale is intersected at 9.5 g/m3 giving the absolute humidity.

- To find the dew point for this condition:

Following a vertical line down from the value of absolute humidity, the air temperature of + 10°C is reached. This is the dew point.

d 1

5

IS 13736 ( Part Z/Set 1) : 1993 IEC Pub 721-2.l(1982)

4bsolute air humidity (g/m’)

g ggz 6 2z :: 9 0 0

cum m 0 00 0

d o- o- o- 0‘ o- d o- 2 6 6 cj ; w‘ L-5 m- 0 2 9 g 9 6 g

::p’c 100

I, ‘. ‘I I I ’ I I ’ I

ju I I l’i Y I Y

I I I I I \ \ \ \ \

I ‘.I I I I ‘i II I I I

I I II \ I, ---;t. ~\‘I,\

I \ Y 1

i \

I 70-- l \ I \ I I , \ \, \ \, \ \,

\ \ \ \ \ \ I\ I, \, \, \ \

I

I I \I\ I

\ 1 \

\,

\

1 \ \

I I \ 60

II

I IJ I i1 t \ \ \ 1

I \ L \ \, \ 50 I I.1 ‘Ill I II\

\ \\\ \ \ \ -y! \ c-2 \, \ \ E ’ \ I \ 6 \I\ I \,\ \

I\ \ \ \ \ \ \ \

40-- I 1 \ \ 1, 1, \ 1, \, \, \ \, \ 1, \

1 4

i i \ \ ‘,

\, \, \ \, ‘\, \, \\ \ ‘\, \,

\

\ 30 \ \ \ \ \ \ \ \ \

-80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60

Air temperature (‘Cl

FIG. Bl. - Constitutioorial diagram for humid air.

6

IS 13736 ( Part USec 1) : 1993 IEC Pub 721-2-l(1982)

ADsolute air humidity (g/ma)

\\\ \\\ ‘. I\\ 1 \ \\ \ \, \,

\ \\ \ \

\ \, \, \, \, ‘, \ ‘, \,

\ \ \ \

\ \ \ \ \ \ \ ‘. 1,

\\\ ’ \,\\ \ 1 I\‘\ \ . ! - i-L-_ \

\ 1 \ \ \\\ ‘, \\\. \_

\\vA’\\‘\lL \ \\\ \\\\‘, \ \ l,

‘\ \

-7A re. -0” -4v -xl _-L” -IV v / 10

Dew point temperature at 100% relative humidq

30 40 50 60

Air temperature (OC) 795/87

FIG. B2. - Constitutional diagram for humid air. Example of application.

.

printed at Dee Kay Printers, New Q&i-l 1@)15, Indip