TURBOMACHINERY IHANDBOOK

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Reprinted from HYDROCARBON PROCESSING o Gulf Publishing Company o @ 1974 . $t.ZS

TURBOMACHINERY HANDBOOK

Published by HYDROCARBON PROCESSING

This reference manual has

issues of HYDROCARBONmanuals in the series are:

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Table of Contents

TURBOMACHINERY HANDBOOK

Page No.

Centrifugal Compressor Performance TestingBetter mechanical testing can improve compressor reliabilityTest compressor performance-in the shopTest compressor performance-in the field

Maintenance Techniques .......How to improve compressor and maintenancelmprove machinery maintenWhy clean turbomachinesA closer look at turbomachHot alignment too complicated

i

I

Turbines using too much steanl"? ...Better pump grouting .1.....

Centrifugal Pumps .. !-. i..

5

6

11

14

17

18

24

28

31

35

3841

45

46

49

56

61

62

66

71

72

76

83

How to improve pump

How to control purnp vibrationHow to prevent pul

Turboexpanders ..1

New develop hot gas

Turboexpanderssystems

Turbotmachinery

Critical. Related

Are couplingsHow

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GasS histories ofConiprq$sor prol

and C

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Centrifugal Compressor

Performance Testing

Better mechanical testing can

improve compressor reliability

Vendor shop testing of critical

process compressors can reveal

mechanical problems prior to

field installation. Here are

some points to consider when

pertorming compressor mec hanical

tests

Douglos F. Neole, Union Carbide Corp.-Chemicalsand Plastics, South Charleston, W. Va.

Conrpnrsson MEoHANTcAL tests have proven effectivein identifying design and fabrication deficiencies. If these

deficiencies are identified before shipment of the com-pressor corrections can be made and verified under opti-mum shop conditions.

The value of compressor mechanical tests is limited bythe absence of significant gasJoad and the low energyinvolved. The tests are most effective if API test standardsand the customer's supplementary test specifications arestrictly enforced as a minimum requirement, Revised andnew API Standards relating to compressors and oil sys-

tems will significantly strengthen test requirements. Thestandards will also increase the obligations of vendors withregard to test facilities and data acquisition.

Test obiectives. Table 1 is a brief list of specific objec-tives of compressor mechanical tests. Note that onlypartial verification of the considerations listed on thetable is claimed. Even the most sophisticated mechanicaltest falls short of complete and prolonged simulation ofactual operation under full gas-load and power.

6

TABLE l-Objectives of centrifugal compressormechanicaltests

Partial verification of:oThe quality of over-all unit assembly

o Fieedom from internal rubs

r Bea ring fit, alignment and adequacy of lubrication

o Rot or-bearing system dynamic stability and calculated critical speed

oVibration levels

o Cor rectness of assembly and tightness of shaft oil seals

o Drive coupling fit-up and balance

o Lub rication system cleanliness and performance

oTrain component compatibility (optional)

o Noise (optional)

API test slqndqrds. The Second Edition of API Stand-ard. 617, "Centrifugal Compressors for General RefineryServices,"'has provided an accepted basis for mechanicalspin tests since 1963. Most manufacturers and purchasers

added to the requirements of API 617 as new technologydeveloped. Many of these additional requirements will be

reflected in the Third Edition of API 617, scheduled forpublication this year.2

Table 2 summarizes key differences between the old andnew API Standard 617. The new standard provides a

significant step toward beter defined, more uniform andmore rigorously verified centrifugal compressors, but thereare areas where the purchaser must define and exercise

his rights 'andf or preferences.

Righf to wilness. The purchaser reseryes the right toobserve testing, dismantling, inspection and reassembly ofeQuipment "when specified." The vendor must provide"sufficient notice" when shop inspection by the purchaseris required. Sufficient notice is to be defined by mutualconsent of the purchaser and vendor. We have foundthat vendors frequently cannot be counted on to maintain

BETTER MECHANICAT TESTING

TABLE 2-APl Standard 617lor centrifugalcompressor mechanical tests

Second Edition (1963) Third Edition (Planned issue)Essentially same

Purchaser reserves the right toobserve tests

lncrease speed f rom 0-100[ MCSin 10ft increments

Run at MGS for 4 hours

Use contract shaft seals and bearings during test

Not required (except lube)

The actual first critical shall bedetermined

Vibration:

Essentially same

Perform and record vibrationsweeps

Use purchased vibrationprobes

Run spare rotors ordered withc0mpress0r

Essentially same but include ad-ditional data on lube and sealoil systems, and rotor dynamics

Mandatory hydro tests

lnquiry specifications and ordershall specify tests requiring witness

lncrease speed in undefined in-crements from 0-110[ MCS

Run at MCS for 4 hours,

uninterrupted

lnstall oil seals after test andmanually turn

Demonstrate control systems(E.G.; inlet guide vanes) to theextent practical

Make every effort to determinefirst critical of flexible shafts, shortof opening case and unbalancing

Vibration:

Record throughout operatingspeed range

Not required

Not required

Not required

Vendor to provide certified detailedlogs including vibration and oiltemperature data

records of all required inspections or to provide adequateadvance notice of inspections. Notification is frequentlytoo late to permit the most knowledgeable machineryspecialist to be assigned and made familiar with hisassignment. The alternative is for the purchaser to con-tinually stress during negotiations and order coordinationmeetings, the requirement for responsible and timely ven-dor notification, and to follow up with frequent checks

by his own inspection/expediting personnel.

Tesl speeds qnd durqtion. The Third Edition of API617 is strengthened by the inclusion of a definition of theincrements of increasing speed during mechanical tests.

The four-hour maximum continuous speed run apparentlyis less rigorous, as an uninterrupted run is no longerrequired. However, we specify successful completion ofan uninterrupted four-hour run, and a repeat uninter-rupted run if bearings, seals or balance require modifica-tion of the test.

Verificqtion of shoft seqls. A significant improvementin the Third Edition of API 617 is the requirement thatcontract bearings and shaft end seals be installed duringthe mechanical test and that the oil leakage from eachseal be measured with approximate design differentialpressures across the seals. Although not required by theSecond Edition, many have imposed this requirement forsometime. More widespread testing with seals in placewill occur following the issue of the Third Edition. It willbe easier for purchasers to gain confidence in the me-chanical adequacy of seals.

Conlrol syslem checks. As indicated in Table 2, theSecond Edition of API 617 required control systems to be

REPRINTED FROM HYDROCAflBON PROCESSING

demonstrated "to the extent practical." For centrifugalcompressors, we have interpreted this to relate to lube oilsystems and inlet guide vane actuators. The Third Editionof API 617 does not contain a comparable requirement.

The new API oil system requires that "the completedoil system shall be shop run to test operations," etc., butit is only by rather liberal interpre_t21i6n that this coversinlet guide vane actuators.3 Within the past two years,we have experienced several startup difficulties frommiscalibrated or mechanically unsound guide vane link-ages. Guide vanes will receive more, not less, attention.

Delerminqtion of criticol speeds. The new edition ofAPI Standard 617 requires that "for flexible-shaft com-pressors, the actual first critical speed shall be deter-mingd-" whereas the Second Edition required "everysff611-16 determine the actual first critical speed-shortof opening the casing to create rotor unbalance." Ourspecifications have independently paralleled the evolutionof the API Standard 617 and have avoided forcing criti-cals. Present thinking is toward mandatory identificationof criticals as required by the Third Edition.

Vibrqtion qnd beqring temperqture meqsuremenlqnd qnqlysis. The revised issue of API Standard 617reflects the progress made during the past 10 years onvibration measurement and analysis. For example, asweep of vibration amplitudes at frequencies covering aminimum range of 25 percent of synchronous to twicevane passing frequency is now required. This is inter-preted to mean multiples of number of vanes times sta-tionary parts such as discharge nozzles or diffuser vanes.Additionally, purchased vibration probes and detectorsshall be used during the mechanical running test. Wehave preferred this practice for several years.

Requirements or recommended practices relating to use

of bearing metal temperature sensors during test are notstated in the API Standard. These detectors have becomestandard for our critical rotating machinery and shouldbe better covered by APL

Spore rotors. Because of the need for reliableprocess compressors, a mechanical run test of spare rotorsordered with the compressor is now mandatory. The prac-tice has been valuable by not only ensuring a properlybalanced rotor, but by avoiding situations where the spare,

although properly balanced, just wouldn't fit in the ma-chine without extensive diaphragm or thrust bearingadjustments.

Vendor tesl dqto. The Third Edition of API 617 re-quires submittal of more extensive test data to the pur-chaser. The more stringent data requirements reflect theimproved scope of the tests as previously discussed. Addi-tional data includes seal oil temperatures, pressures andleakage rates; rotor balancing and critical speeds, andmore extensive vibration data.

Optionol tesls. Optional tests which may now be speii-fied in the purchaser's inquiry or order include hydraulicperformance, complete unit tests, tandem tests, gear tests,

helium leak tests, sound level tests and post-test inspec-

tions. We consider performance tests on an individualbasis as a function of the extent to which the design has

been proven by analogous machines, the degree to which

TABLE 3-AP! Standard 614* for lubrication,shaft-sealing, and control oil systems-

summary of inspection and test requirements

o Purchaser has right of inspection

oPurchaser's inspector furnished specifications, material certifications, andrunning test data

oPurchaser shall specify whether purchased oil system shall be used duringmain equipment shop test

oComponent hydrostatic tests comparable to previous API Standard-617,Second Edition

o Four-hour shop test under normal system operating conditions

o System checked for leaks and proper functioning of controls and alarms

.System capable of riding out filter-cooler and oil pump changeovers

. System cleanliness criteria defined

+ Planned issue

TABLE 4-Vendor test plans

Test installation

Shop and contract equipment included in the test trainXnown limitations in driver power and/or speedMeasuring instrumentsPressure and/or temperature control systemsSeal and lube oil console limitations

Test procedure

Duration of each speed runShop data sheets

Special procedures to avoid excessive temperatures or other limitationsPost-test inspections

Report outlineScheduled issue dateData to be reportedDisbussion subject headings

final operating conditions can be synthesized, the criti-cality of the machine, the time schedule and the cost.

Gears are also subjected to running tests. When duplicategears are ordered, they are subjected to full speed, fulltorque load and back-to-back tests. Following the test, afull bearing and tooth-contact inspection is performed.The gear undergoes a standard four-hour shop runningtest on reassembly. Complete unit, tandem, or shop sound

level tests are seldom justified.

Lube, seol ond conlrol oi! systems. A properly de-signed and functioning oil system is a prerequisite for areliable compressor train. Thus a discussion of compressormechanical tests should include consideration of the oilsystem that will support the train. This consideration is

facilitated by the new API Standard 614 entitled "Lubri-cation, Shaft Sealing, and Control Systems for Special-Purpose Applications."s

Table 3 briefly summarizes key features of oil system

tests as specified by API 614. The right of inspection andreceipt of finished specifications, material certificationsand running test da[p are established. It is the purchaser'sresponsibility to specify whether the purchased oil system

shall be used during the compressor test. Our normalpractice has been to require cleaning, flushing and ship-ment preservation of oil systems. Operation of the con-tract oil console during mechanical testing of the com-pressor has been required only infrequently. Ifowever,some purchasers are requiring tests to be run with thecontract oil console and this appears to have some advan-tages. The design and fabrication of oil systems seem tobe a sideline with many compressor manufacturers, and

8

startup problems are not uncommon. Furthermore, themandatory use of the system for test will provide a signifi-cant incentive to thoroughly clean the systems in thevendor shops.

Additional points in API Standard 614 bear considera-tion. Filter and cooler changeovers shall be accomplishedwithout the system's delivery pressure dropping to theautomatic start setting of the standby pump. The capa-bility of the control valve shall be demonstrated by start-ing, running and stopping a second pump (main orstandby) without the delivery pressure dropping below 75

percent of the differential between normal and shutdownpressures. The valve shall also be capable of holding oilpressure at minimum oil flow (normal bearing and seal oilplus steady state control oil flows).

Problems with new systems could have been avoided bythe foregoing types of checks. For instance, we frequentlyuse shaft-driven main oil pumps. After starting a unit onthe electric motor-driven auxiliary pump, the main pumpis operated briefly in parallel with the auxiliary, andthe recycle control valve is wide open. When the auxiliaryoil pump is tripped off, the valve response was too slow toprevent a drop in header pressure and subsequent trip ofthe compressor train. Some vendors have resolved thisproblem through more responsive and better tuned con-trols. Other vendors have provided a manually controlledrecycle line from the auxiliary pump which can be opened

to effectively remove the pump from the system prior toits shutdown. We have made similar last minute modifica-tions in the field. Proper exercising of oil systems duringtest can avoid these costly and time-consuming nuisances.

Test plans ond preporolions. The latest API Stand-ards provide good general definitions of test requirements.It is only in limited instances, however, that the standardsrequire vendor submittal of a detailed plan for each spe-

cific compressor system test. We have found that this is aserious omission. Some vendors stop short of full compli-ance with API requirements. For several years we haverequired the vendor to submit detailed test plans forreview prior to testing of critical machinery.

The contents of an ideal test plan are listed in Table 4.

Advance review of the test setup will avoid surprises toinspectors andf or machinery specialists when they reportto the vendor's shop. These setups normally have suffi-cient drive turbine power available to attain specifiedsystem speeds. It is common, however, to encounter limi-tations with electric motor drives. The unavailability of amotor with properly rated speed and the inability to varyspeed result in less than adequate tests. The developmentof excessive casing gas temperatures during tests havealso compromised tests. Prior knowledge of these circum-stances can permit corrections or alternatives to beimplemented in a timely manner. Situations where thepurchaser is forced to compromise his test specifications orlose his scheduled time on the test stand can be avoided.

The proposed test procedures should define the basis fordetermining when the compressor undergoing test has

stabilized and when the test operator is free to move on toanother point. Normally, the temperature of oil leavingthe bearings is the last indicator to stabilize. The pur-chaser's insistence on stabilization of oil temperatures ateach point seldom extends the test significantly. It is

desirable, however, for the vendor to know in advance

that this requirement will be made.

BETTER MECHANICAL TESTING

The planned shop data sheet (or typical automatic data

center printout) provides practical insights into the ex-tent of data to be taken. A quick scan of these sheets can

identify unacceptable omissions. For example, it is com-

mon to find that seal oil leakages are not to be recorded,

or are to be recorded at static conditions or at reduced

speeds and oil temperatures. Every effort should be made

to simulate design speeds and operating temperatures toget the best possible insight into actual operating per-formance.

The poor legibility of vendor test report forms is a

source of frequent frustration. Specifications call for leg-

ible data sheets, but it seems some will have to be rejected

before satisfactory quality can be attained.The lack of interpretation of test results is also of con-

cern. Most vendors will provide a formal test report withbare data. Ordinarily, interpreted d.ata are supplied onlyif required by the purchase order. This is a worthwhilerequirement; prior consideration of the characteristics ofa compressor can be valuable when diagnosing a real orapparent problem on the midnight shift!

VENDOR TEST INSTAI.I.ATIONS

Purchaser emphasis on the reliability of compressors has

led to a general upgrading of vendor test installations. Ithas become the exception when major vendors are unableto comply with the older API test requirements.

Vibrqtion ond temperqlure monitoring. Significantprogress has been made in using the purchaser's ownproximity probe holders and probes during mechanicaltesting" In the past, vendors were slow to accept thefeasibility of shop installation of the probes----especially

two per journal that could be adjusted and replaced whilethe machine was in operation. The contract probes werefrequently not available for the test so temporary shop

probes and holders were used. Part of the value of shop

mechanical tests as a reference for startup problem diag-nosis was lost because surfaces observed by the shop

probes differed from surfaces observed by permanentlyinstalled probes,

It is still a challenging task to develop mutually accept-able proximity probe installations. Vendor's ability toutilize probes during test has improved, however. Manyvendors have installed variable frequency filters, real time

About lhe qulhorDoucLAs F. NsAr,E is mo,nager---ltrocessmacldnerg appl;ication for (Jnion Car-bide Corp.--4hemicals and Plastics,South Charleston, W.Va. He i,s respon-sible for the sTtecifi,cation antl processdesi,gn of large machinerg systems forcapital erpansions and deaelopment ofnew technology in this area. P,r'i,or er-perience with Union Carbide Corp. in-cludes plant process design and a oari,etyof engineet'ing nxanag enxent as sign-

ments. Mt'. Neale holds a B,S. degree i,n mechanical eng,ineer-ing from Rensselaer Polgtechnic Institute and, a M.S. degreei,n meclu,nical engineering from Massachusetts Institute ofTechnology. He is a registered prof essional engineer in WestVirgina and, a member of A.S.M.E.

spectrum ama)yzerc, X-Y plotters and oscilloscopes to per-

mit any probe or set of probes to be read, analyzed and

displayed. Multichannel tape recorders are becoming in-creasingly cornmon for simultaneous recording and subse-

quent display of many data channels. Some vendors have

even installed "run-out subtractors" to electronically mask

vibration or excessive rotor or probe surface runout. One

major rnanufacturer recently commissioned a minicom-puter system to simultaneously analyze multiple data

inputs and print results within minutes of test completion.Progress has not been so great with regard to bearing

metal temperatures. We are strongly committed to using

bearing metal temperature sensors on critical machines

but have found that even more extensive vendor liaison

is required than with proximity probes. Test installationsfor reading out the sensors are frequently vendor impro'vised and may not be available during the test unless

requested in advance.

Couplings. Common test stand practice is to use shop

couplings except for possibly one hub, during compressor

mechanical tests. We have accepted this practice in the

past. However, recent experiences indicate that couplings

are one of the more troublesome machinery train com-

ponents. Many coupling manufacturers apparently do not

enforce standards for residual unbalance and vibrationcomparable to those of compressor manufacturers. Addi-tionally, coupling manufacturer's use, during balancing, ofcoupling spool and sleeve surfaces that were eccentric tothe gear tooth pitch circle has led to "cranking" and

excessive vibration.The use of the contract coupling is being increasingly

specified for tests of critical machines for several reasons:

o The contract coupling will permit the closest practicalsimulation of the final field installation with respect torotor dynamics.

o The mechanical test can confirm coupling balanceand provide an indication of machining quality.

o The use of the contract coupling reduces the tempta-

tion for vendor shop personnel to "touch ,p" the shop

coupling to compensate for minor rotor unbalance.

The added expense and time required to adapt the

contract coupling to test service is well justified.

CONDUCT OF TESIS

The strengthened API standards supplemented by the

preparations discussed in this paper will contribute to

effective mechanical testing of centrifugal compressors.

The following additional recommendations are made,

however:

o A competent machinery engineer experienced in startupand maintenance problems should witness the tests. On-the-spot interpretations and decisions will materially influ-ence the effectiveness of the test and assure satisfactoryperformance of the compressor.

a Rotor residual unbalance data sheets and run-out maps

should be reviewed prior to the test. The knowledgegained can alert the test engineer to the possibility of rubs

or abnormal noises.

o The vendor's calculations of expected casing tempera-tures during tests should be reviewed. There are too many

REPRINTED FROM HYDROCARBON PROCESSING

instances where failure to plan a vacuum test has resultedin termination of the run before planned speeds arereached.

o The use of electronic rotor run-out subtractors in con-junction with proximity vibration probes should not bepermitted. Vendors should machine probe surfaces wellenough to avoid the need for these corrections.

. Insist that actual rotor critical speeds be identified. Ifit is necessary to "force" the critical, the removal of. acoupling bolt will normally suffice. If the coupling is tooclose to a bearing, it may be necessary to open the case

and add internal weights.

o Compressor design and manufacturing deficiencies be-come apparent with the passage of time. Therefore, dq-mand an uninterrupted four-hour maximum continuousspeed run regardless of the test stand problems encoun-tered. If it is a hardship to keep the machine operatingfor four hours on the test stand, it is likely that the same

condition will prevail in the field.

o Be certain that the contract or shop drive coupling isremoved prior to rotor rebalance. It can be a costly errorto permit rotor or coupling unbalance to be camouflagedby correction of an adjacent removable part.

o A previously stored or idle rotor should be run at a

speed sufficient for self-correction of bow or "set" beforebeing rebalanced. Recently one of our machinery engi-neers refused to accept the vendor's suggestion to balanceand then test. During the initial run, apparent unbalancedisappeared. The vendor's proposal to save time by priorbalancing would have resulted in recurring unbalanceafter the "set"of the rotor was spun out.

Our vendor inspectors and test engineers always checkthe compressor bearings and shaft end seals following atest. The case is not opened unless unexplained noise orvibrations are encountered.

Value of tesls. ft was stated earlier that compressor

mechanical tests only partially accomplish the specificobjectives listed in Table 1. The degree of accomplish-ment is limited by the inherent shortcomings of a minimalgas-load, low energy operation. It is influenced by theextent to which operating temperatures, pressures andflows are simulated and by the quality and quantity ofrecorded measurements.

Our experience indicates that mechanical tests areeffective in confirming the quality of assembly of com-pressors primarily with regard to:

o Adequacy of clearances and alignment of shaft andwheel labyrinth seals

o The absence of Ieaks in lubrication and seal oil passages

o Bearing fit, alignment and lubrication

o Rotor balance

o Rotor-bearing stability and avoidance of criticals.

Several instances of labyrinth seal rubs, bearing mis-alignment and damaged thrust bearing shoes were iden-tified. In another instance, a wiped journal bearing wasdiscovered. The wipe was explained by the vendor as theresult of a "somewhat tight" bearing, and scraping was

10

proposed. Our engineer insisted that a new bearing be

installed and the test rerun. The same situation occurred.It was found that the bearing housing was undersized andcaused excessive bearing crush. If scraping of the bearinghad been permitted, the plant would have inherited achronic problem that would arise each time new bearingswere installed.

Not unexpectedly, there have been instances of unde-tected deficiencies in assembly. In one instance, a casingsupport plate was improperly aligned relative to themachine's centerline. At mechanical spin test tempera-tures, casing expansion was insuficient to permit detec-tion. The problem became apparent when the machinewas placed in normal operation. A misbored thrust bear-ing housing had gone undetected until placed in opera-tion. The axial forces placed on the rotor during themechanical test were insufficient to "seat" the rotor thrustcollar and cause the shaft deflection and vibration ob-served later in full-load operation.

An error in the pattern drawing used for the upper halfof the diaphragms of one machine went undetected. Thisdefect permitted hot discharge gas to bypass the balancepiston and recycle to suction through the balance pistonvent line. A performance test would have provided twoindicators of this deficiency: (1) reduced capacity and(2) higher-than-planned gas temperatures. A simple cal-culation of the predicted mechanical test air dischargetemperature might have identified the problem.

Mechanical tests provide significant insight into rotor-bearing dynamic stability, especially in Iight of thelimited gas dampening provided by the unloaded condi-tions established for mechanical tests. Excessive vibrationwas noted on one of our machines. Touch-up balancingwas performed on the rotor before it and a duplicatedcoupling were reinstalled and the test rerun. When thevibration persisted, the rotor was stripped for total rein-spection, a potentially disastrous flaw was found, andthe shaft was junked.

Mechanical tests of compressors with seals in place havealso been effective. fn one instance, excessive seal leakage

was evident. The seal O-rings appeared to fit but were notas specified. In addition, an out-of-round outer seal bush-ing (floating ring) and incorrect spacing of parts atassembly were found. The vendor replaced the defectiveparts and reworked the seals to obtain a satisfactorilyperforming system.

Lube oil consoles have not been tested with the associ-

ated compressor, and pump noise and vibration have been

encountered in several instances during startup. These

faults are usually corrected by field realignment of thepump and piping. Control system deficiencies hav.e been

more common and commissioning cleanup is always aheadache. Specification of a more extensive workout inthe vendor's shop is increasingly justified. Testing of theoil console and compressor together is becoming a neces-

sary requirement.

ACKNOWLEDGMENT

l'[dii"l,c-,Yl:48ii:1,ffi ::is;"ur'"r,"]l:

LITERATURD CITEDr API 617-Ccntrifugal Compressors for General Refinery Service, Seond

Edition, 1963, Amerien Petroleum Institute, Washington, D. C.zAPI 617-Third Edition, planned issue.t API 61,!-Lubrication, Sbaft-Sealing, and Control OiI System for Special-

Pupose Applications, planned issue. I

Test compressor

performance

-in the shop

Compression equipment must pertorm as

expected. Failure to do so can result

in many startup and operation

difticulties. Here's what can be done

to avoid problems betore the machinery

is installed

Royce N. Brown, Dow Chemical U.S.A., Houstol

RncrNrr,v there has been much written about thcmechanical reliability of compressor trains. There is noquestion as to the importance of a high degree of rnechau-ical reliability since it generally results in a "go" or"no go" situation. Good performance attainability is gen-erally not as consequential, because partial load operationmay be possible with a deficient compressor. A fact notgenerally realized is that the subject of performance is arequirement for reliability! For a machine to be truly reli-able it rnust not only run well mechanically but mustperform at 100 percent of its capacity whenever calledupon. It is then very desirable to test prove performanceprior to receiving a machine, o.r as an alternative, to fieldtest shortly after installation prior to enterins prodrrction.

AS'YIE TEST CODE

The basis for code testing is the ASME Powcr TestCode PTC 10-1965 Compressors and Exhausters.l Severalspecific points made in the Code were intended as guidingprinciples, yet are often misunderstood. The followingfacts must be considered:

o The Code establishes the rules for a test, includingthe definitions of Code or Non-Code.

o The Code is not a textbook on testing.

o The Code has to assume that the gas properties oithe gases involved are known. It recosnizes that this is

Fig,_1-Allowable departure from specified design parametersfor Class ll and Class lll tests.

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