1. Process EngineeringEquipment HandbookClaire SoaresMcGraw-HillNew York Chicago San Francisco Lisbon London MadridMexico City Milan New Delhi San Juan SeoulSingapore Sydney Toronto

2. Library of Congress Cataloging-in-Publication DataSoares, Claire.Process engineering equipment handbook / Claire Soares.p. cm.Includes index.ISBN 0-07-059614-X (acid-free paper)1. Chemical plantsEquipment and supplies. I. Title.TP157.S658 2002660.283dc21 2001045228McGraw-HillCopyright 2002 by The McGraw-Hill Companies, Inc. All rights reserved. Printed in theUnited States of America. Except as permitted under the United States Copyright Act of1976, no part of this publication may be reproduced or distributed in any form or by anymeans, or stored in a data base or retrieval system, without the prior written permission ofthe publisher.1 2 3 4 5 6 7 8 9 0 CCW/CCW 0 7 6 5 4 3 2 1ISBN 0-07-059614-XThe sponsoring editor for this book was Kenneth P. McCombs, the editing supervisor wasStephen M. Smith, and the production supervisor was Sherri Souffrance. It was set in NewCentury Schoolbook by Best-set Typesetter Ltd., Hong Kong.Printed and bound by Courier Westford.McGraw-Hill books are available at special quantity discounts to use as premiums and salespromotions, or for use in corporate training programs. For more information, please write tothe Director of Special Sales, McGraw-Hill Professional, Two Penn Plaza, New York, NY10121-2298. Or contact your local bookstore.This book is printed on acid-free paper.Information contained in this work has been obtained by The McGraw-Hill Companies, Inc.(McGraw-Hill) from sources believed to be reliable. However, neither McGraw-Hill nor itsauthors guarantee the accuracy or completeness of any information published herein andneither McGraw-Hill nor its authors shall be responsible for any errors, omissions, or damagesarising out of use of this information. This work is published with the understanding thatMcGraw-Hill and its authors are supplying information but are not attempting to renderengineering or other professional services. If such services are required, the assistance of anappropriate professional should be sought. 3. ContributorsAASME SpecificationsASME: 345 East 47 Street, New York, NY 10017 USAAbrasivesAbrasive Technology, Inc.: 8400 Green Meadows Drive, Westerville, OH 43081USASandusky-Chicago Abrasive Wheel Co., Inc.: 1100 W. Barker Avenue, MichiganCity, IN 46360 USANational Metal Abrasive, Inc.: P.O. Box 341, Wadsworth, OH 44282 USAAcid RainEnvironment Canada: Environment Canada Enquiry Centre, Ottawa, OntarioK1A 0H3 CanadaAcoustic Enclosures, TurbineAltair Filters International Limited: Omega Park, Alton, Hampshire GU342QE EnglandActuatorsJ.M. Voith GmbH: P.O. Box 1940, D-89509 Heidenheim, GermanyVoith Turbo GmbH & Co., KG: P.O. Box 1555, D-74555 Crailsheim, GermanyAir FiltrationAltair Filters International Limited: see aboveAir Pollution ControlAlstom (formerly ABB Power Generation): Finspong 61282 Sweden;Hasselstrasse 16, CH-5401 Baden, Switzerland; 5309 Commonwealth CenterParkway, Midlothian, VA 23112 USABBearingsDemag Delaval: 840 Nottingham Way, Trenton, NJ 08638 USARevolve Magnetic Bearings, Inc.: Calgary, Alberta, CanadaBoilersEnvironment Canada: see aboveBrakesJ.M. Voith GmbH: see abovexv 4. CCFD (Computational Fluid Dynamics)Fluent Inc.: Lebanon, NH USACarbon; Carbon-Graphite Mix ProductsAdvance Carbon Products: 2036 National Avenue, Hayward, CA 94545 USACarbon Dioxide (CO2); CO2 DisposalVatenfall: S162 87 Stockholm, SwedenCement; Portland CementEnvironment Canada: see aboveCentrifugesDorr-Oliver Inc.: 612 Wheelers Farm Road, Milford, CT 06460 USAChemical Complex; (Petro)Chemical Complex; Chemical PlantPetrochemcial Company of Singapore: SingaporeChemicalsARCO Chemical Company: 3801 West Chester Avenue, Newton Square, PA19073-2387 USAChemicals (Toxic), HandlingARCO Chemical Company: see aboveChillers; Crystallizers; Chemical Separation Method; Alternative to Distillation/Fractional DistillationArmstrong Engineering Associates: P.O. Box 566M, West Chester, PA 19381-0566 USACogenerationAlstom: Finspong 61282 SwedenCompressorsSulzer-Burckhardt: Winterthur, SwitzerlandDemag Delaval: see aboveAerzener Maschinenfabrik, GmbH: D2358 Aerzen, GermanyCondensersAlstom: Hasselstrasse 16, CH-5401 Baden, Switzerland; D6800 Mannheim 1,GermanyCondition Monitoring (CM); Condition-Monitoring System(s) (CMS); Engine Condition Monitoring (ECM); EngineConditionMonitoring System(s) (ECMS)Claire Soares Inc.: P.O. Box 540213, Dallas, TX 75354 USAControl Systems; ControlsSulzer-Burckhardt: see aboveVoith Turbo GmbH & Co., KG: P.O. Box 1555, D-74555 Crailsheim, GermanyVoith Safeset A.B.: Ronningev. 6, S-82434 Hudliksvall, SwedenControls, RetrofitPetrotech Inc.: 108 Jarrel Drive, P.O. Box 503, Belle Chase, LA 70037 USADemag Delaval: see aboveJ.M. Voith GmbH: see abovexvi Contributors 5. ConveyorsContributors xviiSandvik Process System, Inc.: USABloch, H., and Soares, C. M., Process Plant Machinery, 2d ed., Butterworth-Heinemann, 1998.Coolant; Engine CoolantARCO Chemical Company: see aboveCooling; Cool, Products That (Air Conditioners); Liquid-Cooled Air ConditionersThermoelectric Cooling America Corporation (TECA): USACooling TowersThe Marley Cooling Tower Company: Marley and Lone Elm Roads, Olathe, KS66061 USADDryingARCO Chemical Company: see aboveEEcological Parks; Industrial Ecological ParksEnvironment Canada: see aboveEcosystemEnvironment Canada: see aboveElectric Motors; Electric Motor ControlsReliance Electric Company: Cleveland, OH USAEmissions; Air EmissionsEnvironment Canada: see aboveEngines, GasCooper-Bessemer Reciprocating: Grove City, PA USAEnvironmental AccountabilityKodak: USACultor: FinlandEnvironmental EconomicsAssiDomn: SwedenExhausters, Centrifugal GasAnsaldo: Milan, ItalyExpansion JointsTownson Expansion Joints: United KingdomExplosion; Explosion Hazard Analysis; Explosion HazardsEutech Engineering Solutions Ltd.: Billingham, Cleveland TS23 4YS EnglandH.M. Principal Specialist Inspector, Health & Safety Executive, Quay House, QuayStreet, Manchester M3 3JB England 6. FFans, CentrifugalAnsaldo: see aboveBloch, H., and Soares, C. M., Process Plant Machinery, 2d ed., Butterworth-Heinemann, 1998.FiltersPeerless Manufacturing Company: 2819 Walnut Hill Lane, Dallas, TX 75229USAForest ProductsAssiDomn: see aboveFuel Gas Conditioning System(s)Peerless Manufacturing Company: see aboveFuel Systems; Fuel Flow ControlJ.M. Voith GmbH: see aboveWhittaker Controls, Inc.: 12838 Saticoy Street, North Hollywood, CA 91605 USAFuels, Alternative; Fuels, Gas TurbineBechtel Power Corporation: Gaithersburg, MD 20878 USAGGenerators; TurbogeneratorsAlstom: see aboveHHeat ExchangersArmstrong Engineering Associates: see aboveHeat Pumps; Heat Pumps, Geothermal; Heating Systems with a Renewable Energy SourceEnertran: CanadaLLife-Cycle Assessment (LCA) (of Turbomachinery)Claire Soares Inc.: P.O. Box 540213, Dallas, TX 75354 USALiquid Natural Gas (LNG)Peerless Manufacturing Company: see aboveLubricationDemag Delaval: see aboveMMeasurementDemag Delaval: see aboveMetallurgy; Metallurgical Repair; Metallurgical RefurbishmentLiburdi Engineering: Hwy. 400, Dundas, Ontario, Canadaxviii Contributors 7. OOil Sands; Synthetic Crude; Tar Sands; ShaleSyncrude Canada Limited: Ft. McMurray, Alberta, CanadaOxygen AnalysisRosemount Analytical: Orville, OH USAOzoneEnvironment Canada: see aboveContributors xixPPollutants, Chemical; Pollutants, (from) Chemical Processes; Pollutant Indicators; Pollutants, Toxic; Pollutants,Toxic ChemicalsEnvironment Canada: see abovePower TransmissionDemag Delaval: see aboveMAAG Gear Company: SwitzerlandJ.M. Voith GmbH: see abovePulp and PaperAssiDomn: see abovePulsation DampenersPeerless Manufacturing Company: see abovePumpsBloch, H., and Soares, C. M., Process Plant Machinery, 2d ed., Butterworth-Heinemann, 1998.Demag Delaval: see aboveSulzer Pumps: USAGoulds Pumps: USARRefineries, PetroleumEnvironment Canada: see aboveSSeals; Gas SealsRevolve Magnetic Bearing, Inc.: see aboveSeparatorsPeerless Manufacturing Company: see aboveStacksAltair Filters International Limited: see aboveTTanksA.O. Smith Engineered Storage Products Company: 2101 S. 21st Street,Parsons, KS 67357 USAEnraf: England 8. Turbines, GasAlstom: see aboveASME: see aboveTurbines, SteamDemag Delaval: see abovePeerless Manufacturing Company: see aboveTurbochargersDemag Delaval: see aboveTurboexpandersDemag Delaval: see aboveUUltrasonic CleaningSonics: USAVVaporizers; Vaporizor ApplicationsArmstrong Engineering Associates: see aboveWWaste ManagementEnvironment Canada: see abovexx Contributors 9. About the AuthorA registered professional engineer in Texas and Alberta, Canada, Claire Soaresgraduated with a B.Sc.Eng. in 1972 and an M.B.A. in 1993. Her career began incomputational fluid dynamics working for Brian Spalding in Imperial College,London, on the COBALT project. She then spent about two years working ondeveloping structural patents for the marine and the power distribution industriesin England and Canada. Her rotating machinery career began in earnest at the oilsands Syncrude site in Fort McMurray, Alberta, in 1975. Four years later, shemoved to Esso Resources and conventional oil and gas production until the oilpatch sat on its tail at the end of 1981. She then accepted a three-year commissionwith the Canadian Air Force as Propulsion Systems Manager for all transportationengines in the Department of Defence Transport Command in Canada. She tookcharge of six helicopter engine fleets, as well as projects related to selectingreplacements for two of those fleets. After that, she moved to the United States tostart work as a senior engineer for Ryder Airline Services Division (ASD was alsocalled Aviall and, before that, CooperAirmotive). At that point ASD was the largestindependent overhaul facility for airline engines in the world, with a shop capacityof about 1000 engines a year. She ran technical support on second shift for 250mechanics and their supervisors on the JT8D, JT3D, and CFM 56 engine lines.Three years later, she was made manager of the V2500 engine repair program, atthat time the first and only designated facility for this engine in the United States.Two years later, after the engine line was up and running, she left to become anindependent consultant, trainer, and writer. She has now lived and worked on fourcontinents. Ms. Soares organizes one to two conference sessions annually for theInternational Gas Turbine Division of the American Society of MechanicalEngineers (ASME) and has done so since 1985. In May 2001 she was appointed toFellow grade by ASME.Process Engineering Equipment Handbook is her fourth book. The first, ProcessPlant Machinery, Second Edition, was coauthored with Heinz Bloch, P.E. This workand Environmental Technology and Economics: Sustainable Development inIndustry helped provide the present handbook with its broad perspective.Turboexpanders and Process Applications, her third book, also coauthored withHeinz Bloch, was released in 2001. All her books are used when appropriate ascourse instruction material for her own and others courses. Ms. Soares writesextensively for technical journals, such as Petroleum Economist, Asian Electricity,and International Power Generation.She also writes for more general audiences, with some television screenplays andarticles for various international newspapers and magazines to her credit. Apublished photographer, she writes poetry and has staged multimedia performancesof her work for organizations such as the city of Dallas. She is a scuba diver andlicensed commercial pilot, and also enjoys swimming and hiking.In-30 10. PrefaceIf you picked up this book you are probably one of those lucky people who run plants.Either a thinly spread engineer (branch of specialty is irrelevant), a newly promotedtechnical manager, or a harassed technologist or senior mechanic, who just was told:See that plant out there? Youre in charge of making it work! Even if youve beenin plants for years, thats enough to make your innards rumble. If you have juststepped out of school, into your first plant, or into a totally different plant from theprevious one you were at, your reaction might be more severe, especially if youbelong to one of the numerous organizations with no budget for rotating machineryspecialists (who look after what moves a process through its paces) orenvironmental specialists (who make certain you dont get fined or jailed, goodintentions notwithstanding, as you run your plant). At this point, I should explainwhere I fit in with your agenda.Twenty-some years ago, some heated arguments on the subject of how much Iwanted to be a rotating machinery specialist took place in Canadas wild and woollynorth. I was fencing with my boss, a process engineer, who was recommending Ijoin his field. It was what my company needed, he asserted. I thought it neededboth of us doing what we loved best. My career bears witness to the fact that I wonthe match, in the short- and long-term.Time since has brought a few things forcibly home to me. To start with, the moreI dealt with plant machinery in any form, the more I accepted that processconditions could affect the performance of that machinery at least as much as actualmechanical characteristics. In operations, repair and overhaul, or retrofit designand reengineering, what keeps people like me a step ahead of the manufacturersfield service representatives is knowledge of the process and familiarity with thecontrols that govern the entire system. In turn, the process engineer who getshanded a plant to run must acquire some basic knowledge of my bread and butter,the machinery that makes everything move up, down, or around. In large facilities,such as the ones I was fortunate enough to spend time in, there generally are in-houserotating machinery specialists. Often, though, the process engineer is notthat lucky and gets everythingprocess components, machinery, controls, and all.Life handed me an education (after formal degree acquisition) in rotatingmachinery specialization and the environmental technology that goes with it (yes,we machinery cranks run the stuff that turns out arguably 80 percent of the gunkin the universe). While doing this, I worked with scores of process engineers, controlengineers, and various other specialists on a variety of projects that were amongthe most high profile in the world in their own right. It was arranging to be in theright placean operating plantto get the best education in the best school in theworld.After all, curriculum, undergraduate or otherwise, is not necessarily any comfort.In my day they rarely taught this stuff to process, chemical, or mechanical engineersxi 11. at universities. They still dont. That leaves all the young engineers in the sameboatwithout any practical guide for reference.My editor at McGraw-Hill was keen that they should have one, and one that waseasy to read. We soon found we were on the same page on the subject of readability.We do not like technical material that sounds more intellectual than it absolutelyhas to, and we do like many diagrams, photographs, tables, and figures.I add two other ingredients to my books and courses: (1) information on items(such as condition monitoring and specialized controls) that will help the engineeroptimize cost-effective operations and (2) information that will help the engineerstay out of trouble with legislators, particularly environmental legislators(regardless of whether the legislation is current or impending). Fines levied forignoring emissions or pollutant statutes may not be high enough to be a deterrentin themselves when weighed against a process plants gross production revenue.They can, however, whittle away at profits while adding to overall costs peroperating hour. Frequently, though, environmental equipment can actually resultin machinerys attaining longer times between overhauls. Also, the loss of goodwillthat priceless commodity on annual reportsis immense if environmentalstandards are not followed.In this competitive age, plants do vie for national, state, or provincial qualitycontrol awards. Clever managers can turn those into longer customer lists.Attaining these awards is not something that many accountants, lawyers, andMBAs, who run major corporations but may have little or no technical exposure,can pull off without their engineers. It is the engineers who are likely to be the keyfigures in putting together the action framework for what will buy their firm newor continued goodwill. Environmental accounting plans, holistic management ofresources and waste products, environmental policy, waste and toxic managementthey mean pretty much the same thing and they are not a feature at all in manyother process engineers reference books.It is painfully evident that the emphasis given to waste and toxic managementvaries globally. It reaches a high in Sweden and Norway, England is fast developingan aggressive proactivity in this vein, and Canada has excellent technology, whichmay or may not get enforced to the appropriate extent depending on the politicalbalance of power at any time. The United States has some large loopholes that aresurprising for a country so advanced; shared emissions legislation is one. And yet,its in the area of waste and toxic management that companies receive the mostvocal and widespread media coverage (and loss of business) when exposed. Some ofthe worlds youth appear to have a sense of resources running low and therefore aneed to conserve them. In these days of increasing international joint ventures, thegaps between all these preferences is fast diminishing and the stable point for theresultant system can tend to reflect the highest standards among the partners.One could argue that subjects that infringe on environmental and wastemanagement turf belong in another handbook and with another kind of engineer.That is not entirely true though this is becoming a specialist field. The reasons forthis statement are rooted in profit margins. If environmental considerations andwaste products can be integrated into production in a way that what might havebeen a hazard or waste now contributes to revenue, this is obviously preferableto that hazard or waste being isolated with its own disposal/neutralization systemthat does not contribute revenue. Some examples are biomass waste in pulp andpaper production, formerly disposed of, that can be converted to gaseous fuel for aturbine (see Pulp and Paper) and chemical by-products in complex downstreampetrochemical plastics production, otherwise waste, that can now also be used asturbine fuel. The controls and system modifications that assist incorporation ofthese profitable adaptions into process plants are given some space.xii Preface 12. Preface xiiiI have also included some basic information on specific controls and monitoringsystems. They are a fact of life on a process engineers turf; the ones I havehighlighted have a proven track record for adding profit margins to processes byminimizing downtime or fluctuations.Similarly, a process engineer may have to make decisions related toturbomachinery performance or capacity that are affected by metallurgicalprocesses. Included is some information on common critical alloys used in todaysplants.This book contains information on the major components and basic systems,including instrumentation and controls, and some optimization techniques that Iwish I had had when I landed, albeit happily, in my first major plant. It also containsexamples, drawn from knowledgeable sources, of action plans that have keptvarious process companies in good standing and high esteem with their public andgovernments worldwide. Selected extracts of the technology that are the bases ofthese policies are also included. These examples and technology extracts arefrequently missing from engineering handbooks; I would be doing users of thishandbook a disservice to leave out this information.Increasingly process plants are becoming small power producers. Governmentsare now beginning to offer incentives to small power producers. The Thaigovernment, which buys the excess power from Essos Sriracha refinery, is just onesuch example. The Alberta, Canada, government buys excess power from SyncrudeCanada Limited, which produces 170,000 barrels of crude oil a day. The Britishpower network buys excess power from Elf Acquitaines Flotta terminal, whichcollects North Sea petroleum products.In other words, this book aims to provide a process engineer with: Knowledge of the basics the process engineer will meet up with Enough knowledge to help the process engineer optimize operation safety,efficiency, and profit margins Information about environmental systems and avoiding trouble with the law Tools to integrate the plants operation with other services, such as powerproduction and waste management, to further optimize profits and minimizelosses due to interruptions in services provided by external companiesClaire Soaresclaire_soares@compuserve.com 13. IntroductionThe contemporary process engineer has to be an all-around generalist. Thishandbook contains basic information on items that cause or assist chemicalreactions, such as chillers. In todays environment, information on additionalsectors is also required to help the plant engineer function.To begin with, besides the components in a plant that produce required chemicaland physical state changes, such as fractionating distillation columns and reactors,the plant engineer needs to know the process plant machinery that transports anddelivers raw material and products. It is this machinery that is very often the baneof the engineers existence. The good news is that with a little knowledge one cankeep most of it running.When that happens, the process plant engineer may have to troubleshootequipment if the plant does not have a rotating machinery engineer. That may bewhy so many of the process plant engineers I talked with asked me to includematerial on condition monitoring and life-cycle (of machinery components)assessment. These two items alone can save a plant a huge amount of its costs perplant operating hour, if properly utilized. I have included some of my notes fromtwo of my basic courses on these subjects.Interestingly enough, plant problems are common at system interfacesatexpansion joints, rather than at what they connect, and at gearboxes, couplings,and torque measurers, rather than the parent items of machinery they link. Also,certain accessories can be weak points if improperly applied. Air filtration canprotect a machine from icing and erosive particles or it might build up excessivepressure drop and penalties on turbine output power. The quantity of informationprovided on these items, such as air filtration and power transmission equipment,reflects this fact.Environmental technology and economics is another area now integral to aprocess engineers world. Without this knowledge, the company could be fined andmanagement imprisoned. Even if this is not an issue, environmental savvy can buya corporation an inestimable amount of goodwill and a high profile in proactivecommunity service. It has resulted in national quality control awards and otherrecognition. This may mean that corporation is preferentially selected as a productor services supplier. Environmentally sound cohabitation of industrial real estatein what are termed ecological industrial parks can also save utility costs.Most importantly, however, taken over the life of a plant, environmentally soundmethodology saves in overall operating costs per unit time. What seems likecleanliness and politically correct extras saves in parts longevity. This is notcommon knowledge in the engineering world. In fact, one common motivation forfitting environmental accessories is that operators are aware that if they wait untilxxi 14. use of same is forced upon them, retrofits of items such as flue gas desulphurizationcost as much as 300 percent more than installation with initial construction.Process plant engineers will probably also have to run their own in-house powerplant at some point. They will have to manage interfaces with the power plant andtheir main process facility. The power is primarily for their own needs, but theyfrequently sell their excess power to the national grid. Even more interesting is thefact that process fluids that would otherwise be waste can sometimes be used asfuel. Examples include flue gas from a mining process used as a heat source andwaste biomass from pulp and paper production gasified to use for steam productionfor running a steam turbine. In turn, waste heat from turbines is used for processpurposes. Excess steam from the heat recovery steam generator in the independentpower plant at Kuala Langat, Malaysia, is used in the owners neighboring mill.Heat recovery schemes in Alberta, Canada, are being used to provide heat tovegetable greenhouses.This cooperative effort between power generation and process technology isunderlined by three major factors. First, the major oil companies, such as Shell,Amoco, and Esso, are now actively involved in major independent power productionas a policythe fuel they produce has a certain market as power production fuel.Second, the drive toward environmentally economic technology to dampen thestrain on the worlds sagging natural resources has played a major part inintegrating the process engineers world with that of power production. Last butnot least, internal power production gives process engineers a much better handleon avoiding the brownouts, fluctuations, and power cuts that an external utilitysupplier can cause. They can also have the flexibility to use products within theplant for unusual fuel when they work with manufacturers who will accommodatetheir requirements. The contemporary competitive business environment is makingit much easier for an engineer to negotiate this adaptability from a manufacturer.With this complex, mobile, and fascinating framework, know that one could neverfit representative information on everything a process engineer might need in onevolume. The compromise I have struck is to cover the basics succinctly and spendeffort on items that the process engineers I talk to and work with have very littleinformation on, but ask about all the time. Not surprisingly, these items can costthe most in terms of cost per operating hour. Costs include lost production time,machinery problems, troubleshooting efforts, useless expense in overdesignedmachinery condition monitoring systems, premature parts replacement, and powersupply problems.Then there was the matter of highly specialized process sectors, such as pulp andpaper, agriculture, and food processing. This book hits the highlights with theseindustries and others, and a specifications and standards section is provided for theprocess engineer to use in conjunction with this book. All the common items in anyprocess industry, such as pumps, motors, couplings, controls, and so forth, are inthis book. As terminology for an item varies so much between industries, it is agood idea to read through the Contents and the Index a few times to get the mostout of this book.Last, but not least, although this book might be more for process engineers inplant operations, I have included some design information where I felt it wouldassist logic. Design and specification work gains from operations and maintenanceexposure.xxii Introduction 15. ContentsPreface xiContributors xvIntroduction xxiA A-1ASME Specifications A-1Abrasives A-1Accident Management A-9Accountability, Environmental (see Environmental Accountability)Acid Rain A-9Acoustic Enclosures, Turbine A-10Actuators A-37Aerfoils; Airfoils (see Metallurgy; Turbines)Agitators A-38Agriculture; Agricultural Product Processing A-48Air Filtration; Air Inlet Filtration for Gas Turbines A-49Air Pollution Control A-83Air Purification; Air Sterilization A-101B B-1Balancing; Onspeed Balancing of a Rotor B-1Balancing Problems, Troubleshooting (Turbomachinery) (see Condition Monitoring)Batteries (see Cells)Bearings B-1Blades and Vanes (for a Turbine) (see Metallurgy; Turbines)Boilers B-11Borescopes B-11Brakes B-11Brick-Lined Process Equipment B-23Briquette Machines B-28C C-1CAD/CAM C-1CFD (Computational Fluid Dynamics) C-1Carbon; Carbon-Graphite Mix Products C-7Carbon Dioxide (CO2); CO2 Disposal C-13Castings (see Metallurgy)Cells C-22Cement; Portland Cement C-22Centrifuges C-34Ceramics C-38v 16. Chemical Cleaning C-38Chemical Complex; (Petro)Chemical Complex; Chemical Plant C-38Chemicals C-41Chemicals (Toxic), Handling C-42Chillers; Crystallizers; Chemical Separation Method; Alternative to Distillation/Fractional Distillation C-62Chimneys (see Stacks)Cleaning C-78Clutches (see Power Transmission)Coatings (see Ceramics; Metallurgy)Cogeneration C-78Coker (see Oil Sands)Color Coding C-81Columns (see Towers and Columns)Combustor(s); Low NOx Combustor (see Turbines)Compressors C-81Condensers C-233Condition Monitoring (CM); Condition-Monitoring System(s) (CMS); EngineCondition Monitoring (ECM); Engine ConditionMonitoring System(s) (ECMS) C-253Control Regulators (see Actuators)Control Systems; Controls C-331Controls, Retrofit C-354Conversion Tables (see Some Commonly Used Specifications, Codes, Standards,and Texts)Conveyors C-408Coolant; Engine Coolant C-408Coolers, Dairy C-412Cooling; Cool, Products That (Air Conditioners); Liquid-Cooled Air Conditioners C-413Cooling Towers C-423Corrosion; Anticorrosion Coatings C-426Couplings (see Power Transmission)Crushers C-426D D-1Dampeners (see Pulsation Dampeners)Desalination D-1Dialysis; Electrodialysis D-2Distillation; Fractional Distillation D-2Diverter; Diverter Damper; Diverter Valve; Flapper Valve D-3Doctor D-3Drives D-3Drum; Knock-Out Drum; Knock-Out Vessel (see Separators)Drying D-4Ducting; Ducting and Joints D-18E E-1ECM (Engine Condition Monitoring) (see Condition Monitoring)ECMS (Engine ConditionMonitoring Systems) (see Condition Monitoring)Ecological Parks; Industrial Ecological Parks E-1Ecosystem E-1Ejectors E-2Electric Motors; Electric Motor Controls E-3Emergency Power Generation (Packages) (see Engines, Gas)Emissions; Air Emissions E-36Engines, Gas E-38Environmental Accountability E-40vi Contents 17. Environmental Air Monitoring (see Emissions)Environmental Economics E-49Evaporative Coolers (see Chillers; Coolers, Dairy)Exhaust Stacks (see Stacks)Exhausters, Centrifugal Gas E-56Expansion Joints E-57Explosion; Explosion Hazard Analysis; Explosion Hazards E-67Extraction, Liquid-Solid E-87F F-1Fans, Centrifugal F-1Filters F-5Flare Stacks F-12Floating Covers F-12Fluidized Bed F-12Forest Products F-12Fuel Gas Conditioning System(s) F-24Fuel Systems; Fuel Flow Control F-29Fuels, Alternative; Fuels, Gas Turbine F-37G G-1Gas Turbine Cleaning or Washing (see Turbines)Gas Turbines (see Turbines)Gearboxes (see Power Transmission)Gears (see Power Transmission)Generators; Turbogenerators G-1Grinding (see Abrasives; Some Commonly Used Specifications, Codes, Standards,and Texts)Grinding Wheels (see Abrasives)H H-1Hazards (see Color Coding; Explosion; Some Commonly Used Specifications,Codes, Standards, and Texts)Heat Exchangers H-1Heat Pumps; Heat Pumps, Geothermal; Heating Systems with a Renewable EnergySource H-1Heat Treatment (see Metallurgy)Heaters, Electric H-6High-Speed Drive Systems (see Power Transmission)Hot Isostatic Pressing (or HIPing) (see Metallurgy)Hydraulic Filters (see Filters)I I-1Industrial Ecological Park (see Ecological Parks)Industrial Ecology (see Ecological Parks)Inlet Ducts and Silencers (see Acoustic Enclosures, Turbine; Air Filtration; Ducting)Instrumentation (see Condition Monitoring; Measurement)Insulation (see Some Commonly Used Specifications, Codes, Standards, and Texts)Irradiation, Food Product I-1L L-1LCA (see Life-Cycle Assessment)LNG (see Liquid Natural Gas)Laser Cutting, Drilling, Machining,Welding (see Metallurgy)Contents vii 18. Life-Cycle Assessment (LCA) (of Turbomachinery) L-1Liquid Eliminators (see Separators)Liquid Natural Gas (LNG) L-21Lubrication L-24M M-1Magnetic Bearings (see Bearings)Measurement M-1Metallurgy; Metallurgical Repair; Metallurgical Refurbishment M-31Metering, Fluids; Metering Pumps (see Fuel Systems)Mist Eliminators (see Separators)Mixers (see Agitators; Centrifuges)Monitoring (see Condition Monitoring)Motors (see Electric Motors)N N-1Noise and Noise Measurement (see Acoustic Enclosures, Turbine)Noise Silencing and Abatement (see Acoustic Enclosures, Turbine)Nondestructive Testing (FP1, MP1, X Ray) (see Metallurgy)Nozzles N-1O O-1Oil Analysis O-1Oil Sands; Synthetic Crude; Tar Sands; Shale O-1Oxygen Analysis O-1Ozone O-4P P-1Packaging P-1Paper (see Pulp and Paper) P-1Pipe (see Some Commonly Used Specifications, Codes, Standards, and Texts) P-1Plastics P-1Pollutants, Chemical; Pollutants, (from) Chemical Processes; Pollutant Indicators;Pollutants, Toxic; Pollutants, Toxic Chemicals P-7Portland Cement (see Cement) P-72Power Production; Power Production In-House; IPP; SPP P-72Power Transmission P-73Pulp and Paper P-204Pulsation Dampeners P-214Pumps P-214R R-1Reactors; Chemical Reactors R-1Refineries, Petroleum R-1Refrigerant(s) R-10Regenerator R-19S S-1Seals; Gas Seals S-1Separators S-10Snubbers (see Pulsation Dampeners)viii Contents 19. Stacks S-29Steam Generator and Steam Supply S-38T T-1Tanks T-1Temperature and Pressure Sensors (see Measurement)Thermal Insulation (see Some Commonly Used Specifications, Codes, Standards,and Texts)Thin-Film Processors (see Chillers)Torque Converters, Measurements, and Meters (see Power Transmission)Towers and Columns T-40Toxic Substances (see Pollutants, Chemical)Transportation, of Bulk Chemicals, of Large Process Equipment T-40Triple Redundancy T-41Turbines, Gas T-43Turbines, Steam T-76Turbochargers T-112Turboexpanders T-114U U-1Ultrasonic Cleaning U-1V V-1Valves (see Control Systems)Vanes (see Metallurgy)Vaporizers; Vaporizer Applications V-1Vents and Flame Arrestors V-31Vibration Measurement (see Condition Monitoring)W W-1Waste Heat Recovery (see Cogeneration)Waste Management W-1Welding (see Metallurgy)Some Commonly Used Specifications, Codes, Standards, Texts Sp-1Index In-1Contents ix 20. AASME SpecificationsA list of specifications available from the American Society of Mechanical Engineersis available in the section Some Commonly Used Specifications, Codes, Standards,and Texts at the end of the book before the index. This list provides additional detailon items that may not be covered in great depth here.AbrasivesAbrasives is a term given to various materials with different physical formats (suchas aggregate, grains, shot, particles bonded with an adhesive, and so forth) that areused to wear down surfaces to desired dimensions or surface finishes or for someother purpose. They may be used in their raw state, such as with shot or glass inshot or glass-bead peening operations. Or they may be used in conjunction withadhesives and fillers to make belts, wheels, and tool surfaces.Sometimes peening operations address more than surface finish. Glass-beadpeening has been used to add a compressive stress layer to the surface of gas-turbinecompressor wheels to bring the net tensile stress level down to tolerablelevels. As alloy metallurgy improved, machinery component operation totally underthe stress endurance curve was possible, and such applications were phased out.They are worth mentioning, however, as they can contribute to puzzling failuremodes if they are wrongly applied during design or repair and overhaul.Abrasives may also be combined with adhesives to make grinding wheels, belts,or other components for precision grinding in sophisticated manufacturing or repairmachinery such as a blade-tip grinder. A blade-tip grinder is basically a combinationof a grinder and a computer or some form of computer numerical control (CNC) thatis used to grind airfoil blade tips to arrive at precise turbine-wheel-assemblydimensions.Product improvements now have produced superabrasives for high-precisionprocesses that are generally used in conjunction with CNC and computer-aideddesign/computer-aided manufacturing (CAD/CAM) programming and equipment.Different types of grinding materials allow larger depths of cut (decreased worktime) with less metallurgical workpiece (heat soak) damage. This lowers overallproduction costs.In the continued drive for improved environmental impact in production, somecompanies are using water coolants rather than oil coolants.The applications of abrasives in process technology are too numerous to mention;however, some basic information on the common facets of abrasives in various statesand process formats follows. Sources are as acknowledged.CNC Applications*Precision-plated grinding wheels are now replacing standard wheels (that useadhesive bonding with abrasive grit) in some applications. These are suitable forA-1* Source: Abrasive Technology, Inc., USA. Adapted with permission. 21. use on nickel- and cobalt-based superalloys, engineered ceramics, and standardferrous alloys. (See Figs. A-1 to A-3.) Advantages of these wheels include: The ability to manufacture tight-tolerance complex forms. Lower initial cost, compared to vitrified and metal bonded superabrasive wheels. Freer cutting, resulting in higher material removal rates, less power, and reducedthermal damage to the workpiece. The ability to hold form or profile from first to last cut. Reduction or elimination of time associated with dressing, setups, and wheelchanges. Safe, high-speed operation due to a steel core. The ability to strip and replate the core.Precision techniques are required to measure the finished products, includingCNC coordinate measuring machine (CMM) capability with associated CAD/CAMfeatures, laser micrometers, form-scan geometry gauge, optical comparators, andother digital gauges.A-2 AbrasivesFIG. A-1 Physical characteristics of specific abrasives. (Source: Abrasive Technology, Inc.)FIG. A-2 CAD/CAM workstation. (Source: Abrasive Technology, Inc.) 22. Standard Grinding Wheels*Technical data standard on abrasivesWheel symbols and markings. All responsible grinding-wheel manufacturers use amarking system established by the American Standards Association. This markingsystem describes the makeup of an abrasive wheel in a manner somewhat similarto the way a chemical formula describes the nature of a chemical compound. Itindicates by a standard system of letters and numbers the important elements usedin the manufacture of the wheel and, to a degree, the amounts and manner of theircombination.Any change in the marking represents a change in wheel characteristics andproduces a corresponding change in the action of the wheel.Familiarity with wheel markings, along with an understanding of thecharacteristics of the material to be ground, helps to determine the kind of workthat a particular wheel is capable of grinding.Elements of the marking system and their significance. (See Table A-1.) The firststation specifies the particular type of abrasive material in the wheel. A completeline of abrasive grains suitable for grinding practically any material are available.The chief difference in the types of abrasive involve their toughness and theirfriability. The dictionary definition of friable is easily crumbled or reduced to apowder; certainly abrasives are not easily crumbled or reduced to a powder. Thedifference is one of degree and both tough and friable types have their applications.YA 51A Tough aluminum oxide for heavy-duty work. Best general purposegrain.AA 52A Semifriable. Frequently specified for precision grinding on averagesteels.TA 53A Practically pure aluminum oxide. White color, friable, and cool cutting.50A Combination of semifriable and white friable grain.Abrasives A-3FIG. A-3 Coordinate measuring machine (CMM). (Source: Abrasive Technology, Inc.)* Source: Sandusky-Chicago Abrasive Wheel Co., Inc., USA. 23. TABLE A-1 Summary of Major Abrasive-Type CharacteristicsSandusky TA 60 K 5 V EandChicago 53A 60 K 5 V BHSandusky and Chicago Grain Bond Sandusky and ChicagoAbrasive Types Sizes Grades Structure Process Bond CodesAAT 54A Combination of tough and friable. Used on fairly heavy work but ofprecision character.32A 55A Gray color polycrystalline grain. Excellent for surface and tool andcutter grinders.PA 12A Light pink colored grain. Gives superior results on problem highalloy steels.RA RA High chrome, ruby colored. Surface grinding and internalwheels.WTC WTC Ceramic abrasive with polycrystalline microstructure. High stockremoval rates and long life with vitrified or resin bonds.ZA ZA Zirconium oxide abrasive. High stock removal on mild, stainless, andhigh alloy steels.C 49C Black silicon carbide. Standard for grinding most nonferrous andnonmetallic materials. Best material for use on ordinary cast irons.GC 49CG Green silicon carbide. A little more friable than regular black.Usually used in carbide tool grinding.CA CA Combination of aluminum oxide and black silicon carbide and aresin bond. Used in plugs and cones when grinding a variety ofmaterials including both steel and cast iron with the same grindingwheel.A-4 AbrasivesFALUMINUM OXIDE 16 2 VVitrified VITRIFIEDdense Aluminum OxideYA Regular 51A 20 G 3 High heatAA Semifriable 52A 24 H R Red ATA Friable 53A 30 I 4 std. BResin E Clear BHBB Off white 36 J E+ Blue 32A Gray 55A 46 K 5 R+ Dark red PA Pink 12A 60 L 6 RRubber Low heatopenRA Ruby RA 70 M 7 Red VAAT 54A 80 N 8 Clear BCombinations 50A 90 O Silicon Carbide100 P 9 A Clear CSILICON CARBIDE 120 Q 10 very RESINOIDAluminum OxideC Black 49C 150 R 11 porous B Brown B1B2GC Green 49CG 180 S 12 BXF220 T Silicon CarbideB Brown B5320 U B15REINFORCED RESINBF Brown BRRUBBERHR Hard HRSR Soft SR 24. Abrasives A-5The second station specifies the grit size. This represents the approximate numberof openings per linear inch in the final screen used to size the grain. Obviouslythe larger the number, the finer the grain. For example, 60 grit size is one that willpass through a screen with 27 openings per inch and be held on a screen with 33openings per inch. The most commonly used grit sizes fall in the range of24 to 120.The third station in the wheel marking is a letter that specifies the grade orrelative holding power of the bond that holds the grains in place. With a given typeof bond it is the amount used in the wheel that determines the wheels grade orhardness. When the amount of bond is increased, the size of the globules of bond(bond posts) connecting each abrasive grain to the adjacent ones is increased. Thislarger bond post is naturally stronger, thereby increasing the hardness of thewheel. The term hardness with respect to abrasive wheels has nothing to do withthe hardness of the abrasive material itself, but rather with the relative shearingand impact forces necessary to dislodge a grain from the wheel. Both soft andhard wheels are necessary and have their specific uses.The ideal grade for any particular grinding application is the one that will holdthe grains in place until they become dull or glazed and then release them allowingnew sharp grains to take their place. This may be any place on the scale betweenthe very soft G, H, or I grades to the very hard S, T, or U grades depending uponthe material being ground, the nature of the results desired, and the variousconditions of speed, pressure, etc., coincident to the operation.The fourth station in the marking system describes the structure (relativebulk density) of the wheel. When the abrasive grains are tightly pressed togetherand interlocked the wheel has a denser structure, which is indicated by a lowerstructure number, such as 3 or 4. When the wheel is rather loosely pressed and hasa more porous nature (more free cutting but necessarily less durable), it has ahigher structure number, such as 7 or 8.The standard structure at which most small wheels are manufactured is 4. Thisstandard density is supplied when the structure number is omitted from the wheelmarking. Structure numbers higher (more open) than 8 require the addition of aburnout material to the grinding wheel mix. Open structure wheels are soft andshould only be used when necessary on difficult to grind materials.The fifth station in the marking system specifies the basic type of bond used inthe wheel. These are:V Vitrified: A glass or porcelain fired to a high temperature.B A synthetic resin: Usually a phenolic thermosetting type. (B originates fromthe old term Bakelite.)R Rubber: Either natural or synthetic oil resistant type.E Shellac: The natural material. Has very limited applications.The sixth station is used to designate the particular bond used in the wheel. Theseare designed with various characteristics to give the resulting wheel certainphysical properties desirable for the different applications.Fundamentals of wheel selection. There are many factors that enter into the properselection of a wheel. Probably the most important things to consider when choosinga wheel for the first time on any job are:A. Material to be ground and its hardness.B. Amount of stock to be removed.C. Finish required.D. Wheel speed or tool speed. 25. E. Area of grinding contact.F. Whether grinding is done dry or with a coolant.G. Severity of the grinding operation.H. Type and condition of grinding machine being used.A. The material being ground affects the selection of the type of abrasive, the gritsize, and the grade.Aluminum oxide is used to grind steel and steel alloys. If the material is heatsensitive or a high-speed steel, use friable grain. For difficult materials, such astool steels high in vanadium, pink or ruby grain is suggested.Silicon carbide is used to grind cast iron, nonferrous metals, and nonmetallicmaterials such as glass.Very hard and brittle materials require relatively fine grain, soft or ductilematerials a coarser grain.Use soft grade wheels on hard materials. A harder grade may be used on moreeasily penetrated materials, which have a lesser dulling effect on the grain.B. Amount of stock to be removed affects the choice of grit size and bond.Use coarse grit for rapid stock removal and finer grits for harder materials. Usevitrified bond for fast cutting and resinoid or rubber for high-speed machines andhigher finish.C. Finish required influences selection of bond and grain size. Generally speakinga resin-bonded or rubber-bonded wheel gives a better surface finish but not as gooddimensional accuracy as a vitrified wheel.Grain size is a major factor in the surface finish but the method of dressing thewheel also plays an important part. Fine finishes can be obtained with relativelycoarse wheels if the wheel is dressed carefully with a diamond and grinding infeedis properly adjusted. A poor finish can result even with a fine wheel if the grindingtechniques used are wrong.A general rule of thumb relating required RMS finish with grit size under averageconditions is as follows.RMS Finish Grit Size32 462032 541520 601015 80D. Wheel speed affects the choice of bond. Vitrified wheels are not to be run inexcess of 6500 surface feet per minute except in very special cases. High speedsrequire resin or rubber bonds.E. Area of grinding contact affects the choice of grit size and grade. Large contactarea indicates coarse grit size and small contact area a finer size. Small contactarea requires a harder grade, the smaller the harder.F. Grinding wet or dry influences the choice of grade. If coolant is used, wheelsone or two grades harder may be used without burning the work. Much dependson the amount and efficiency of coolant reaching the area of contact.G. The severity of the grinding operation influences the choice of abrasive typeand to some extent the wheel grade. A tough abrasive, regular aluminum oxide,would be used for grinding steel under severe conditions. A milder friable abrasivewould be used for light grinding on hard or heat-sensitive steels. IntermediateA-6 Abrasives 26. Abrasives A-7types, semifriable or a combination, would be used under conditions of averageseverity. Where rough conditions such as deburring or removing rough scale exist,it is usually necessary to use a harder grade and coarser grit than the nature ofthe material would call for under normal grinding conditions.H. The type and condition of the machine being used will influence the choice ofbond and grade. If the machine is of a portable type one may assume that the wheelwill have rougher usage than if used on a fixed base machine. If, in addition, it isa high-speed machine, a resin-bonded wheel is mandatory. Generally speaking,portable machines require harder grade wheels than permanently fixed machines.Peening; Shot Peening*For illustrative purposes, some standard information on certain types of shotfollows.An example of standard product informationStandard abrasive meets Society of Automotive Engineers (SAE) requirements forsize, chemical composition, hardness, microstructure, and physical properties.Size: See previous chart.ChemistryCarbon .85%1.20%ManganeseS70S110 .35%1.20%S170 .50%1.20%S-230 and larger .60%1.20%Silicon .40%1.50%Sulfur .05% maxPhosphorus .05% maxHardnessS-40/48RCM 48/55RCHH 55/62RCFH 63/68RCMicrostructure: Uniform martensite tempered to a degree consistent with thehardness range with fine, well-distributed carbides, if any.Physical characteristics: Reference SAE J-827.Specialty productsPrecise media for the most exacting requirements, including roll etch grit for thesteel industry, special cutting grit for the granite industry, and military specificationshot (MIL-13165-C) for precision peening applications, and customized products tomeet a customers unique requirements.PackagingDrums: Nonreturnable 55-gallon steel drums palletized on expendable woodenpallets.* Source: National Metal Abrasive, Inc., USA. Adapted with permission. 27. Shot 2000 lb netGrit 1667 lb net sizes G-12 through G-401500 lb net sizes G-50 through G-120Bags/cartons: 50 lb net, multiwall paper bags40 bags per carton (2000 lb net)strapped to disposable wooden pallets.Bulk: Custom bulk packaging available.Typical material safety data sheetSECTION I PRODUCT IDENTIFICATIOND-U-N-S No.: 14-421-8252Product Names: Perma-Steel Shot Common Name: Cast Steel ShotPerma-Steel Grit Cast Steel GritChemical Family: FerrousSECTION II HAZARDOUS INGREDIENTSCHEMICAL NAME CAS NUMBER %WEIGHT OSHA ACGHIPEL TWA TLV TWAIron 1309-37-1 96 10 mg/m3 5 mg/m3as oxide fume as oxide fumeManganese 7439-96-5 0.351.3 C* 5 mg/m3 C* 5 mg/m3as dust as dustC* 5 mg/m3 C* 1 mg/m3as fume as fumeCarbon 1333-86-4 0.81.3 None Noneestablished establishedSilicon 7440-21-3 0.41.2 15 mg/m3 10 mg/m3(as nuisance dust)SECTION III PHYSICAL DATAMelting Point: 13711482C Vapor Pressure: Not ApplicableEvaporation Rate: Not Applicable Vapor Density: Not ApplicableBoiling Point: 28503150C Percent Solid by Weight: 100%Specific Gravity (at 60F): 7.6 pH: Not ApplicableSolubility in Water: Not ApplicableAppearance and Odor: Shot is near spherical. Grit is angular. Both are gray to bluein color with slight metallic odor.SECTION IV FIRE AND EXPLOSION HAZARD DATAFlash Point: Not Applicable Flammability Limits: Not ApplicableAutoignition Temperature (solid iron exposed to oxygen): 930CCast Steel Shot and Grit will not burn or explode. The solid form of material is notcombustible. Fire and explosion hazards are moderate when material is in the formof dust and exposed to heat or flames, chemical reaction, or contact with powerfuloxidizer.Fire Extinguishing Method: Use dry chemicals or sand to exclude air.A-8 Abrasives*C means ceiling limit, limits that shall not be exceeded, even for a short time. 28. Accident ManagementAccidents are generally categorized according to levels of severity. These levelswould be as follows or subdivisions thereof, depending on the nature of the process.The accident may be one that:1. Results in death for nonplant personnel (public fatality).2. Kills one or more plant personnel (major accident).3. Kills the operator (plant fatality).4. Injures personnel (time loss) and/or damages property (asset loss).5. Is prevented by operators action (near miss).6. Is prevented by policy/legal area restrictions and personnel procedures and/ormanually activated equipment.7. Is prevented by automatic systems/equipment. The systems may provide passive(monitoring) capability or active real-time control.When a process engineer provides information to help determine a plantsinsurance premiums, he or she will find that those premiums decrease as theaccident level goes from 1 to 7 in the previous list. Planning to avoid accidentsis thus a major function of the process engineers duties. Any manualactions/procedures, such as training on plant simulators, required to help avoidaccidents should also be practiced or drilled until they become easy to follow whenactually required.To help avoid the possibility of human error, automation in plant-safety systemsis now an area of practicing triple redundancy. Triple redundancy was formerlyobserved only with control of high-performance military aircraft systems. Now,increasingly, it pays off with land-based control systems that are safety, operational,or control in scope. See Triple Redundancy.Accountability, Environmental (see Environmental Accountability)Acid RainAcid rain is precipitation polluted by acidification with atmospheric pollutants.These pollutants include emissions of oxides of nitrogen (NOx), oxides of sulfur(SOx), and hydrogen chloride radicals. Various strengths of nitric acid, sulfuricacid, and hydrochloric acid result. Key indicators of acid rain include emissionlevels of NOx and SOx, wet sulfate deposits, and trends in acidity in lakesand other freshwater bodies. An increase in emissions that increases the level ofany of these indicators will bring environmental, regulatory, and potentially publicand special-interest group pressures to bear on a plant. Sample measurementsof these indicators on a national or provincial scale are illustrated in Figs. A-4to A-7.Reference and Additional Reading1. Soares, C. M., Environmental Technology and Economics: Sustainable Development in Industry,Butterworth-Heinemann, 1999.Acid Rain A-9 29. A-10 Acoustic Enclosures, TurbineFIG. A-4 United States and eastern Canada SOx emission trends. (Source: Environment CanadaSOE 96-2, Spring 1996.)Acoustic Enclosures, TurbineEnclosures around noisy rotating machinery, particularly gas turbines, provideprotection against noise and help contain risk from situations such as small gasleaks. The design of acoustic gas turbine enclosures is summarized in this sectionin text extracts from two papers on the subject. These extracts give the readerall the salient points to watch for if specifying or buying an acoustic enclosure. Italso provides the reader with basic knowledge of how acoustic sound intensitymeasurements are conducted generally (i.e., for any kind of equipment). Note alsothat these designs were built for offshore applications where weight has to beminimized. 30. Applications of Sound Intensity Measurements to Gas Turbine Engineering*NomenclatureA = total absorption in receiving roomI, I0 = intensity, pW/m2L1, L2 = sound pressure levels, dBLI = sound intensity level, dBAcoustic Enclosures, Turbine A-11FIG. A-5 United States and Canada acid rain NOx emission trends. (Source: Environment CanadaSOE 96-2, Spring 1996.)* Source: Altair Filters International Limited, UK; also, this section is adapted from extracts from apaper published in ASME Journal of Engineering for Gas Turbines and Power, Vol. 113, October 1991. 31. A-12 Acoustic Enclosures, TurbineFIG. A-6 Wet sulfate deposits: eastern North America. (Source: Environment Canada SOE 96-2,Spring 1996.)LK = reactivity indexP, P0 = pressure, PaPa, Pb = pressure, PaS = surface area of the test panel, m2W, W0 = power, pWr, Dr = distance, mt = time, s 32. Acoustic Enclosures, Turbine A-13FIG. A-7 Trends in lake sulfate levels (North America). (Source: Environment Canada SOE 96-2,Spring 1996.)u = particle velocity, m/sr =density, kg/m3Gas turbines that are supplied to the oil and power industries are usually givenextensive acoustic treatment to reduce the inherent high noise levels to acceptablelimits. The cost of this treatment may be a significant proportion of the total costof the gas turbine installation. In the past it has been difficult to determine if theacoustic treatment is achieving the required noise limits because of a number of 33. A-14 Acoustic Enclosures, Turbineoperational problems. These problems include: the presence of other nearby, noisyequipment, the influence of the environment, and instrumentation limitations.Traditionally, sound measurements have been taken using a sound level meter thatresponds to the total sound pressure at the microphone irrespective of the originof the sound. So, the enforcement of noise limits has been difficult because ofuncertainties concerning the origin of the noise.Recent advances in signal processing techniques have led to the development ofsound intensity meters that can determine the direction, as well as the magnitude,of the sound, without the need for expensive test facilities. These instrumentsenable the engineer to determine if large equipment, such as gas turbine packages,meet the required noise specification even when tested in the factory or on sitewhere other noise sources are present.There are, of course, limitations in the use of sound intensity meters, and thereare some differences of opinion on measurement techniques. Nevertheless, theacoustic engineers ability to measure and identify the noise from specific noisesources has been greatly enhanced.In this section, the differences between sound pressure, sound intensity, andsound power are explained. Measurement techniques are discussed with particularreferences to the various guidance documents that have been issued. Some casehistories of the use of sound intensity meters are presented that include field andlaboratory studies relating to gas turbines and other branches of industry.Fundamental conceptsSound pressure, sound intensity, and sound power. Any item of equipment thatgenerates noise radiates acoustic energy. The total amount of acoustic energy itradiates is the sound power. This is, generally, independent of the environment.What the listener perceives is the sound pressure acting on his or her eardrumsand it is this parameter that determines the damaging potential of the sound.Unlike the sound power, the sound pressure is very dependent on the environmentand the distance from the noise source to the listener.Traditional acoustic instrumentation, such as sound level meters, detects thesound pressure using a single microphone that responds to the pressure fluctuationsincident upon the microphone. Since pressure is a scalar quantity, there is no simpleand accurate way that such instrumentation can determine the amount of soundenergy radiated by a large source unless the source is tested in a specially builtroom, such as an echoic or reverberation room, or in the open air away from soundreflecting surfaces. This imposes severe limitations on the usefulness of soundpressure level measurements taken near large equipment that cannot be moved tospecial acoustic rooms.Sound intensity is the amount of sound energy radiated per second through a unitarea. If a hypothetical surface, or envelope, is fitted around the noise source, thenthe sound intensity is the number of acoustic watts of energy passing through 1 m2of this envelope (see Fig. A-8). The sound intensity, I, normal to the sphericalenvelope of radius, r, centered on a sound source of acoustic power, W, is given by:(1)IWr=4p 2Clearly, the total sound power is the product of the sound intensity and the totalarea of the envelope if the sound source radiates uniformly in all directions. Sincethe intensity is inversely proportional to the distance of the envelope from the noisesource, the intensity diminishes as the radius of the envelope increases. But as this 34. Acoustic Enclosures, Turbine A-15FIG. A-8 The intensity level from a point sound source. (Source: Altair Filters InternationalLimited.)distance increases, the total area of the envelope increases also, so the product ofthe intensity and the surface area (equal to the sound power) remains constant.When a particle of air is displaced from its mean position by a sound wave thatis moving through the air there is a temporary increase in pressure. The fact thatthe air particle has been displaced means that it has velocity. The product of thepressure and the particle velocity is the sound intensity. Since velocity is a vectorquantity, so is sound intensity. This means that sound intensity has both directionand magnitude.It is important to realize that sound intensity is the time-averaged rate of energyflow per unit area. If equal amounts of acoustic energy flow in opposite directionsthrough a hypothetical surface at the same time, then the net intensity at thatsurface is zero.Reference levels. Most parameters used in acoustics are expressed in decibelsbecause of the enormous range of absolute levels normally considered. The rangeof sound pressures that the ear can tolerate is from 2 10-5 Pa to 200 Pa. This rangeis reduced to a manageable size by expressing it in decibels, and is equal to 140 dB.The sound pressure level (SPL) is defined as:= PP20 log ( 2 10- 5) 10SPL dB re. Pa0Likewise, sound intensity level (SIL) and sound power level (PWL) are normallyexpressed in decibels. In this case,II2 = 10 ( ) 10 logSIL dB re. 1 pW mWW0PWL dB re. pW0= 10 ( 1 ) 10 log 35. A-16 Acoustic Enclosures, TurbineThe relationship between sound pressure level and sound intensity level. When thesound intensity level is measured in a free field in air, then the sound pressure leveland sound intensity level in the direction of propagation are numerically the same.In practice most measurements of the sound intensity are not carried out in a freefield, in which case there will be a difference between the sound pressure andintensity levels. This difference is an important quantity and is known by severalterms, such as reactivity index, pressureintensity index, P-I index, phase index,or LK value. This index is used as a field indicator to assess the integrity of ameasurement in terms of grades of accuracy or confidence limits. This will beconsidered in more detail later in this section.InstrumentationSound intensity meters. A sound intensity meter comprises a probe and an analyzer.The analyzer may be of the analog, digital, or FFT (fast Fourier transform) type.The analog type has many practical disadvantages that make it suitable only forsurveys and not precision work.Digital analyzers normally display the results in octave or 1/3 octave frequencybands. They are well suited to detailed investigations of noise sources in thelaboratory or on site. Early models tended to be large and heavy and requireelectrical main supplies, but the latest models are much more suited to siteinvestigations.FFT analyzers generate spectral lines on a screen. This can make the displayvery difficult to interpret during survey sweeps because of the amount of detailpresented. Another disadvantage of FFT-based systems is that their resolution isgenerally inadequate for the synthesis of 1/3 octave band spectra.Sound intensity probes. There are several probe designs that employ either anumber of pressure microphones in various configurations or a combination of apressure microphone and a particle velocity detector. The first type of probe usesnominally identical pressure transducers that are placed close together. Variousarrangements have been used with the microphones either side by side, face to face,or back to back. Each configuration has its own advantages and disadvantages.If the output signals of two microphones are given by Pa and Pb, then the averagepressure, P, between the two microphones is:(2)P = 1 ( P + P )2a b The particle velocity, u, is derived from the pressure gradient between the twomicrophones by the relationship:(3)uprdtu( P - P)b a dtr1= - = -r1r DSince sound intensity, I, is the product of the pressure and particle velocity,combining equations 2 and 3 gives the intensity as(4)I+ P P( - ) 2rDb a = -a b P P dtrFigure A-9 shows a two microphone probe, with a face-to-face arrangement,aligned parallel to a sound field. In this orientation the pressure difference is 36. Acoustic Enclosures, Turbine A-17FIG. A-9 The finite difference approximation of sound intensity for a two microphone configuration.(Source: Altair Filters International Limited.)FIG. A-10 Schematic representation of a pressure/velocity probe. (Source: Altair FiltersInternational Limited.)maximized, and so is the intensity. If the probe is aligned so that the axis of thetwo microphones is normal to the direction of propagation of the sound wave, thenthe outputs of the two microphones would be identical in magnitude and phase.Since the particle velocity is related to the difference between the two pressures,Pa and Pb, then the intensity would be zero.The second type of probe combines a microphone, to measure the pressure, andan ultrasonic particle velocity transducer. Two parallel ultrasonic beams are sentin opposite directions as shown in Fig. A-10. The oscillatory motion of the air causedby audio-frequency sound waves produces a phase difference between the twoultrasonic waves at their respective detectors. This phase difference is related tothe particle velocity component in the direction of the beams. This measure ofparticle velocity is multiplied directly by the pressure to give the sound intensity.Guidelines and standards in sound intensity measurements and measurement techniqueGuidelines and standards. Work began in 1983 on the development of aninternational standard on the use of sound intensity and the final document isabout to be issued. Further standards are expected dealing specifically withinstrumentation. 37. A-18 Acoustic Enclosures, TurbineTABLE A-2 Uncertainty of the Determination of Sound Power Level (ISO/DP 9614)Octave Band 1/3 Octave Standard Deviations, dBCenter Band CenterFrequencies, Hz Frequencies, Hz Class 1 Class 2 Class 363125 50160 2 3 4250500 200630 1.5 2 410004000 8005000 1 1.5 46300 2 2.5 4A-Weighted (506300 Hz) 1 1.5 4NOTES:1. Class 1 = Precision Grade, Class 2 = Engineering Grade, Class 3 = Survey Grade.2. The width of the 95% confidence intervals corresponds approximately to four times the dB values in thistable.In the absence of a full standard the only guidance available was the draft ISOstandard (ISO/DP 9614) and a proposed Scandinavian standard (DS F88/146).The ISO document ISO/DP 9614 specifies methods for determining the soundpower levels of noise sources within specific ranges of uncertainty.The proposed test conditions are less restrictive than those required by theInternational Standards series ISO 3740-3747, which are based on sound pressuremeasurements. The proposed standard is based on the sampling of the intensitynormal to a measurement surface at discrete points on this surface. The methodcan be applied to most noise sources that emit noise that is stationary in time andit does not require special purpose test environments.The draft document defines three grades of accuracy with specified levels ofuncertainty for each grade. Since the level of uncertainty in the measurements isrelated to the source noise field, the background noise field, and the sampling andmeasurement procedures, initial procedures are proposed that determine theaccuracy of the measurements. These procedures evaluate the Field Indicatorsthat indicate the quality of the sound power measurements. These field indicatorsconsider, among other things: The pressureintensity index (or reactivity index) The variation of the normal sound intensities over the range of the measurementpoints The temporal variation of the pressure level at certain monitoring pointsThe three grades of measurement accuracy specified in ISO/DP 9614, and theassociated levels of uncertainty, are given in Table A-2.The Scandinavian proposed standard (DSF 88/146) was developed for thedetermination of the sound power of a sound source under its normal operatingconditions and in situ. The method uses the scanning technique whereby theintensity probe is moved slowly over a defined surface while the signal analyzertime-averages the measured quantity during the scanning period.The results of a series of field trials by several Scandinavian organizationssuggested that the accuracy of this proposed standard is compatible with theEngineering Grade, as defined in the ISO 3740 series.The equipment under test is divided into a convenient number of subareas thatare selected to enable a well-controlled probe sweep over the subarea. Guidance isgiven on the sweep rate and the line density. Measurement accuracy is gradedaccording to the global pressureintensity index, LK. This is the numericaldifference between the sound intensity level and the sound pressure level. If this 38. Acoustic Enclosures, Turbine A-19field indicator is less than or equal to 10 dB then the results are considered to meetthe engineering grade of measurement accuracy. As this field indicator increases invalue, the level of uncertainty in the intensity measurement increases. When theLK value lies between 10 and 15 dB the measurement accuracy meets the Surveygrade.Measurement techniques. The precise measurement technique adopted in aparticular situation depends on the objectives of the investigation and the level ofmeasurement uncertainty that is required.(A) Subareas. It was mentioned earlier that the total sound power is the productof the intensity and the surface area of the measurement envelope around thenoise source. In practice, most noise sources do not radiate energy uniformly in alldirections so it is good practice to divide the sound source envelope into severalsubareas. Each subarea is then assessed separately, taking into account its areaand the corresponding intensity level. The subarea sound powers can then becombined to give the total sound power of the source.The number, shape, and size of each subarea is normally dictated by twoconsiderations: the physical shape of the source and the variations in intensity overthe complete envelope. Subareas are normally selected to conform to componentsof the whole source such that the intensity over the subarea is reasonably constant.It is important that the subareas are contiguous and the measurement envelopetotally encloses the source under investigation.(B) Sweep or point measurement. Should one measure the intensity levels at discretepositions, with the probe stationary, or should the probe be swept over the subarea?This controversy has occupied much discussion time among practicing acousticians.For precision grade measurements, discrete points are used, but for lower gradework, sweeping is acceptable.If discrete points are used then the number and distribution of the measurementpoints must be considered in relation to the field indicators.In surroundings that are not highly reverberant and where extraneous noiselevels are lower than the levels from the source under investigation, relatively fewdiscrete points may be used, distributed uniformly over the surface. The distancefrom the source may be as great as 1 m.As the extraneous noise levels increase and/or the environment becomes morereverberant, measurements must be made progressively closer to the source inorder to maintain an acceptable level of uncertainty in the measurements. This alsorequires more measurement points to be used because of the increase in the spatialvariation of the intensity distribution.If sweeping is used then other factors must also be considered. The speed withwhich the probe is swept across the subarea must be uniform, at about 300 mm/sec,and the area should be covered by a whole number of sweeps with an equalseparation between sweep lines. Care must be taken that excessive dwell time doesnot occur at the edges of the subarea when the probes direction of sweep is reversed.The operator must also be careful that his or her body does not influence themeasurements by obscuring sound entering the measurement area as he or shesweeps.(C) Distance between source and probe. Generally, the greater the extraneous noiseand the more reverberant the environment then the closer should be the probe tothe source. In extreme cases the probe may be only a few centimeters from thesource surface in order to improve the signal-to-noise ratio. This is normallyfrowned upon when using conventional sound level meters because measurements 39. A-20 Acoustic Enclosures, Turbineof sound pressure, taken close to a surface, may bear little relation to the pressuresoccurring further away from the surface. This discrepancy is not due simply to theattenuation with distance that normally occurs in acoustics.The region very close to a surface is called the near field. In this region the localvariations in sound pressure may be very complex because some of the sound energymay circulate within this near field and not escape to the far field. Thisrecirculating energy is known as the reactive sound field. The sound energy thatdoes propagate away from the surface is called the active sound field because thisis the component that is responsible for the acoustic energy in the far field.Since sound intensity meters can differentiate between the active and reactivesound fields, measurements of intensity taken close to noise sources can faithfullyindicate the radiated sound energy. However, using a conventional sound levelmeter near to a noise source may indicate higher sound power levels than occur inthe far field because these instruments cannot differentiate between active andreactive fields.Some advantages and limitations in sound intensity measurementsBackground noise. One of the main advantages of the sound intensity method ofmeasurement is that accurate assessments of sound power can be made even inrelatively high levels of background noise. But this is only true if the backgroundnoise is steady (i.e., not time varying). Using conventional sound pressure levelmethods the background noise level should be 10 dB below the signal level ofinterest.Using sound intensity techniques the sound power of a source can be measuredto an accuracy of 1 dB even when the background noise is 10 dB higher thanthe source noise of interest. Figure A-11a shows a noisy machine enclosed by ameasurement surface. If the background noise is steady, and there is no soundabsorption within the measurement surface, then the total sound power emittedby the machine will pass through the measurement surface, as shown.FIG. A-11 The effect of sound sources inside and outside the measurement surface. (Source: AltairFilters International Limited.) 40. Acoustic Enclosures, Turbine A-21If, however, the noisy machine is outside the measurement surface, as shown inFig. A-11b, then the sound energy flowing into the surface on the left hand side willbe emitted from the right hand side of the measurement surface. When the soundintensity is assessed over the whole measurement surface the net sound powerradiated from the total surface will be zero.Effects of the environment. When the sound power of a noise source is evaluated inthe field using sound pressure level techniques, it is necessary to apply a correctionto the measured levels to account for the effects of the environment. Thisenvironmental correction accounts for the influence of undesired sound reflectionsfrom room boundaries and nearby objects.Since a sound intensity survey sums the energy over a closed measurementsurface centered on the source of interest, the effects of the environment arecancelled out in the summation process in the same way that background noise iseliminated. This means that, within reasonable limits, sound power measurementscan be made in the normal operating environment even when the machine underinvestigation is surrounded by similar machines that are also operating.Sound source location. Since a sound intensity probe has strong directionalcharacteristics there is a plane at 90 to the axis of the probe in which the probe isvery insensitive. A sound source just forward of this plane will indicate positiveintensity, whereas if it is just behind this plane the intensity will be negative (Fig.A-12).This property of the probe can be used to identify noise sources in many practicalsituations. The normal procedure is to perform an initial survey of the noise sourceto determine its total sound power. The probe is pointed toward the source systemto identify areas of high sound intensity. Then the probe is reoriented to lie paral-lelto the measurement surface and the scan is repeated. As the probe moves acrossa dominant source the intensity vector will flip to the opposite direction.Testing of panels. The traditional procedure for measuring the transmission loss,or sound reduction index, of building components is described in the series ofFIG. A-12 Sound source location using the intensity probe. (Source: Altair Filters InternationalLimited.) 41. A-22 Acoustic Enclosures, TurbineFIG. A-13 Comparison of the pressure and intensity methods for measuring the sound reductionindex of panels. (Source: Altair Filters International Limited.)standards ISO 140. The test method requires the panel under investigation to beplaced in an opening between two independent, structurally isolated reverberationrooms, as shown in Fig. A-13.Sound is generated in the left hand room and the sound pressure levels in thetwo rooms are measured. Assuming that the sound energy in the right hand roomcomes through the panel then the sound reduction index (SRI) of the panel is givenby:(5)SRI = L1 - L2 + 10 * log10 (S A) dBFor this method to give accurate results, flanking transmission (sound bypassingthe test panel) must be minimal and both rooms must be highly reverberant.If the measurements in the right hand room are carried out using sound intensity,then it is necessary to reduce the amount of reverberation in this room. Since theprobe can measure the sound intensity coming through the panel then flankingtransmission is no longer a limitation.For these reasons one can dispense with the second reverberation roomaltogether. The sound reduction index is then given by:SRI = L1 - LI - 6 dB (6)If the panel contains a weak area, such as a window, the sound reduction indexof the window can be assessed separately. But this will only work if the panel is agreater sound insulator than the window.Measuring tonal noise sources. Measuring the sound power of tonal noise sourcespresents difficulties using traditional techniques (ISO 3740, 1980). Unfortunately,using sound intensity techniques on such sources is also fraught with problems.This is because the spatial distribution of the intensity is very sensitive to smallalterations in source position and the presence of nearby sound reflective objects.Case studies of the use of sound intensityGas turbine package witness testing. Gas turbine packages are normally assembledin large factory buildings or in the open air between factory buildings. In eithercase, the environment is totally unsuitable for reliable acoustic tests to be carriedout using sound level meters alone. Sound intensity techniques are especiallyrelevant in these situations because of the location in which the tests are to becarried out and because some components, such as the compressor test loop, may 42. Acoustic Enclosures, Turbine A-23FIG. A-14 Sound pressure and sound intensity levels for a gas turbine package during witnesstesting. (Source: Altair Filters International Limited.)TABLE A-3 Rank Ordering of Components in Terms of the A-WeightedSound Power LevelsDescription of Measured Item Measured Sound Power Levels, dB(A)Combustion air intake 110Combustion air plenum and silencer 104Turbine comp. vent. air breakout 104Turbine enclosure 103Compressor casing 103Gearbox 103Breakout from temporary exhaust 96not be contract items. By surveying each component with a sound intensity meterthe sound power for each component can be determined separately.Figure A-14 shows a typical gas turbine driving a compressor. The figures on thedrawing indicate the sound pressure and sound intensity levels that were measuredduring a particular witness test on an RB211 gas turbine package. The soundpressure levels in close proximity to the package were between 89 and 103 dB(A),with the higher levels dominating. Even so, reliable values of the intensity levelswere obtained from which the sound power levels were determined. These valuesare given in Table A-3. Since the sound intensity level is numerically equal to thesound pressure level in free field, the average sound intensity over a given surfacearea of a gas turbine package provides a direct indication of the average soundpressure level from that surface in free field conditions.Referring again to Fig. A-14, the sound intensity level measured by the casingof the ventilation fan was 94 dB(A). It would not normally be possible to measurethe output from this fan accurately, using a sound level meter, in this situationbecause of the relatively high sound pressure level in this area due to othersources.During the testing of another package, the sound power levels from theventilation fan casing and the fan motor were measured separately. The fan motorwas found to be noisier than the manufacturers stated levels. Discussions with themotor manufacturer revealed that the wrong cooling fans had been fitted to themotors, which accounted for this increase in noise level. The correct cooling fanswere subsequently fitted. 43. A-24 Acoustic Enclosures, TurbineTABLE A-4 Comparison of the Sound Levels from Two Roller MillsDescription Machine A, dB(A) Machine B, dB(A)Total sound power for machine 96 94Sound pressure level by machine 92 89Sound power level of the motor 93 85This example clearly illustrates the benefits of sound intensity measurements tocheck compliance with noise specifications when the test items are very large andare sited in acoustically undesirable areas.Comparison of two nominally identical production machines. This example is takenfrom an extensive survey of a production department that had many, relativelysmall, machines close together in a highly reverberant factory room. The twomachines were nominally identical roller mills, as used in many production linesin the paint, flour, and confectionary industries. The drive motors were situated onthe top of the machines. A routine sound intensity survey was carried out on eachmachine during normal production because it was not possible to run the machinesin isolation. The two machines are identified as machine A and machine B.Table A-4 gives the overall, A-weighted sound pressure levels and sound powerlevels for each machine, and the sound power levels of the motors. The total soundpower levels of the machines agreed very well with the values obtained by themanufacturer using sound pressure measurements to derive the sound powerlevels (ISO 3740, 1980). This technique can only give the total sound power of amachine; it cannot obtain the sound power levels of parts of a machine.At the time of the survey two machines were each in areas of high noise levelsand their total sound power levels were 96 and 94 dB(A). But comparing the motorsound power levels revealed a difference of 8 dB(A) in their respective levels eventhough both motors were classified as the low noise type and cost more thanthe standard motors. This is just one example where a significant degree of noisecontrol might be achievable by selecting the correct one of two nominally identicalelectric motors. However, using the traditional method of sound pressure levelmeasurement would not reveal any difference between the motors.The acoustical properties of flexible connectors. Heavy-duty flexible connectors areused to join separate components of a gas turbine package. When high-performanceacoustic hardware is used it is imperative that these flexible connectors do notcompromise the total acoustic performance of the package. This is particularly soin the gas turbine exhaust system where multilayered flexible connectors areexposed to high temperatures and severe buffeting from exhaust gases. In someexhaust systems overlapping metal plates are inserted inside the flexible connectorsto reduce the buffeting of the flexible material. If additional sound attenuation isrequired, a heavy, fibrous mat, or bolster, is inserted between the plates and theflexible connector.For the acoustics engineer, these flexible connectors are a problem because thereis very little data on their acoustical performance, and the designs do not lendthemselves to simple theoretical prediction. A brief laboratory investigation wascarried out to compare the performances of seven types of flexible connectors withand without plates and bolsters. The tests were carried out in Altairs acousticallaboratory, which was designed to test materials using sound intensity techniques.The samples were physically quite small so the low-frequency performances were 44. Acoustic Enclosures, Turbine A-25FIG. A-15 Sound reduction index of a flexible connection. (Source: Altair Filters InternationalLimited.)probably distorted by the small size of the samples. Nevertheless, the exerciseyielded much valuable information and led to a simple engineering method ofpredicting a flexible connectors acoustic performance from a knowledge of its basicparameters.Figure A-15 compares the sound reduction indices of a typical, multilayeredflexible connector tested alone, with plates and with bolster and plates. All of thetest results showed a sharp increase in performance at 250 Hz due to the plates.No satisfactory explanation can be offered at this stage for this effect, which maybe related to the small size of the samples. But in the middle and high frequenciesthe results were generally as expected with the plate giving an additionalattenuation of about 5 dB compared to the compensator alone. The combination ofthe plate and bolster gave an additional attenuation of between 10 and 15 dBcompared to the flexible connector alone.Sound source location. During two noise surveys the sound power levels from twodifferent designs of lube oil console were measured using the sound intensity meter.The overall sound power levels were 93 dB(A) and 109 dB(A). The two consoles hadelectrically driven pumps and both emitted strong tonal noise. In the first case thetonal noise was centered on 8 kHz; using the sound intensity probe it was possibleto home in on the pump suction pipe as a major noise source. This was confirmedby vibration velocity measurements.In the second survey the pump outlet pipe gave the highest sound intensityreading. Since this was a relatively long pipe, which was rigidly attached to theframe of the console, it was a dominant source both in its own right and because itwas exciting the framework. In these cases the sound intensity meter was a usefultool in identifying dominant sources among a large number of small, closely packednoise radiators.This section has discussed the concepts of sound intensity, sound power, andsound pressure. It has shown how sound intensity meters have given the acousticsengineer a very powerful diagnostic tool. Noise specifications for large, complexmachinery can now be checked without the need for special acoustics rooms.The advantages, and limitations, of sound intensity have been discussed in somedetail and several applications have been illustrated by case histories taken fromsurveys carried out in the process and gas turbine industries. 45. A-26 Acoustic Enclosures, TurbineThe superiority of sound intensity meters over sound level meters is clearlyapparent. Certain types of laboratory studies can also be carried out more costeffectively using intensity techniques.Although there are some limitations in the use of sound intensityinstrumentation, when used intelligently, it can yield valuable information ondominant noise sources, which, in turn, should provide more cost-effective solutionsto noise control in the oil and power industries.Acoustic Design of Lightweight Gas Turbine Enclosures*Nomenclaturea, b = panel dimensions, R1 = flow resistivitym index or transmissionB, Bx, By, Bxy = bending and loss, dBtorsional stiffnesses R = sound reductionc = speed of sound in S = stiffnessair, m/s a = attenuation constantd = fiber diameter, mm for the material, dB/mf = frequency, Hz h = dampingf1 = first panel lm = wavelength ofresonance, Hz sound in thefc, fcx, fcy = coincidence absorptive layer, mfrequency, Hz v = Poisson ratiol = thickness of r0 = density of airabsorptive layer, m rm = density of absorptiveln = natural logarithm layerm = mass per unit area, t = transmission coefficientkg/m2 w = angular frequencyGas turbines are used extensively in onshore and offshore environments for powergeneration, but their use introduces a number of potential hazards. To reduce therisks caused by fire and high noise levels, enclosures, with intake and exhaustsilencers, are fitted around the turbines. These enclosures and silencers must becapable of withstanding large static loads produced by equipment sited on top ofthem and large dynamic loads due to wind.Traditionally these enclosures are heavy and expensive, especially when stainlesssteel or aluminum is required for offshore use. This has led to a consideration ofmore cost-effective designs that still comply with the stringent demands of the oiland gas industry.One approach that is proving successful is the use of a corrugated enclosuredesign, which employs a thinner steel wall than