©ISO2017–Allrightsreserved

ISO/TC131/SC5N797Date:2018‐03‐13

ISO/CD6358‐5

ISO/TC131/SC5

Secretariat:AFNOR

Pneumaticfluidpower—Determinationofflow‐ratecharacteristicsofcomponentsusingcompressiblefluids—Part5:Testmethodtodeterminepowerlossinsteady‐stateflow

Transmissionspneumatiques‐‐Déterminationdescaractéristiquesdedébitdesélémentstraversésparunfluide compressible ‐‐ Partie 5:Méthodes de calcul des caractéristiques de débit pour des groupes decomposants

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Foreword

ISO(theInternationalOrganizationforStandardization)isaworldwidefederationofnationalstandardsbodies (ISOmember bodies). Thework of preparing International Standards is normally carried outthrough ISO technical committees. Eachmember body interested in a subject for which a technicalcommittee has been established has the right to be represented on that committee. Internationalorganizations,governmentalandnon‐governmental,inliaisonwithISO,alsotakepartinthework.ISOcollaborates closely with the International Electrotechnical Commission (IEC) on all matters ofelectrotechnicalstandardization.

The procedures used to develop this document and those intended for its further maintenance aredescribedintheISO/IECDirectives,Part1.Inparticularthedifferentapprovalcriterianeededforthedifferenttypesof ISOdocumentsshouldbenoted.ThisdocumentwasdraftedinaccordancewiththeeditorialrulesoftheISO/IECDirectives,Part2(seewww.iso.org/directives).

Attentionisdrawntothepossibilitythatsomeoftheelementsofthisdocumentmaybethesubjectofpatentrights.ISOshallnotbeheldresponsibleforidentifyinganyorallsuchpatentrights.DetailsofanypatentrightsidentifiedduringthedevelopmentofthedocumentwillbeintheIntroductionand/orontheISOlistofpatentdeclarationsreceived(seewww.iso.org/patents).

Anytradenameusedinthisdocumentisinformationgivenfortheconvenienceofusersanddoesnotconstituteanendorsement.

For an explanation on the voluntary nature of standards, the meaning of ISO specific terms andexpressionsrelatedtoconformityassessment,aswellasinformationaboutISO'sadherencetotheWorldTradeOrganization(WTO)principles intheTechnicalBarrierstoTrade(TBT)seethefollowingURL:www.iso.org/iso/foreword.html.

ThisdocumentwaspreparedbyTechnicalCommitteeISO/TC131,Fluidpowersystems,SubcommitteeSC5,Controlproductsandcomponents.

AlistofallpartsintheISO6358seriescanbefoundontheISOwebsite.

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Introduction

Inpneumaticfluidpowersystems,poweristransmittedandcontrolledthroughagasunderpressurewithinacircuit.Componentsthatmakeupsuchacircuitareinherentlyresistivetotheflowofthegasanditisnecessary,therefore,todefineanddeterminetheflow‐ratecharacteristicsthatdescribetheirperformance.

ISO6358:1989wasdevelopedtodeterminetheflow‐ratecharacteristicsofpneumaticvalves,baseduponamodelofconvergingnozzles.Themethodincludedtwocharacteristicparameters:sonicconductance,C,andcriticalpressureratio,b,usedinaproposedmathematicalapproximationoftheflowbehaviour.Theresultdescribedflowperformanceofapneumaticvalvefromchokedflowtosubsonicflow,basedonstaticpressure. Thisneweditionusesstagnationpressureinstead,totakeintoaccounttheinfluenceofflowvelocityonthemeasurementofpressures.

Experience has demonstrated thatmany pneumatic valves have converging‐diverging characteristicsthatdonot fit theISO6358:1989modelverywell.Furthermore,newdevelopmentshaveallowedtheapplication of this method to additional components beyond pneumatic valves. However, this nowrequirestheuseoffourparameters(C,b,m,andΔpc)todefinetheflowperformanceinboththechokedandsubsonicflowregions.

ThispartofISO6358describesatestmethodtodeterminethepowerlossofapneumaticcomponentusingmostofthetestequipmentanddataobtainedfromthetestconductedinPart1.Itisnecessarytoexpandtheequipmenttoobtainadownstreamtemperature;andtoobtainveryaccuratetemperaturedatabothupstreamanddownstream.

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Pneumaticfluidpower—Determinationofflow‐ratecharacteristicsofcomponentsusingcompressiblefluids—Part5:Testmethodtodeterminepowerlossinsteady‐stateflow

1 Scope

Thisdocumentspecifiesasteady‐statemethod fortestingpneumatic fluidpowercomponentsthatusecompressiblefluids,i.e.gases,andthathaveinternalflowpathsthatcanbeeitherfixedorvariableinsize,todeterminetheirflow‐ratecharacteristicsandpowerloss.Inadditionitdoesnotapplytocomponentsthatexchangeenergywiththefluidduringflow‐ratemeasurement,e.g.,cylinders,accumulators,etc.

ThistestmethodusesdataobtainedfromtheproceduresofPart1,boththeconstantupstreampressuretestandthevariableupstreampressuretest.

This document specifies requirements for the test installation, the test procedure and thepresentationofresultsforsteady‐statemethod.

Developmentoftheequationsforpowerloss,andanexamplecalculation,isgiveninAnnexA.

2 Normativereferences

Thefollowingdocumentsarereferredtointhetextinsuchawaythatsomeoralloftheircontentconstitutesrequirementsofthisdocument.Fordatedreferences,onlytheeditioncitedapplies.For undated references, the latest edition of the referenced document (including anyamendments)applies.

ISO1219‐1, Fluid power systems and components—Graphic symbols and circuit diagrams—Part1:Graphicsymbolsforconventionaluseanddata‐processingapplications

ISO5598,Fluidpowersystemsandcomponents—Vocabulary

ISO6358‐1,Pneumatic fluidpower—Determinationof flow‐ratecharacteristicsofcomponentsusingcompressiblefluids—Part1:Generalrulesandtestmethodsforsteady‐stateflow

3 Termsanddefinitions

Forthepurposesofthisdocument,thetermsanddefinitionsgiveninISO5598andISO6358‐1andthefollowingapply.

ISO and IEC maintain terminological databases for use in standardization at the followingaddresses:

— IECElectropedia:availableathttps://www.electropedia.org/

— ISOOnlinebrowsingplatform:availableathttps://www.iso.org/obp

3.1powerlosslossofenergyperunitoftime(expressedaswatts)forgaspassingthroughthecomponent

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4 Symbolsandunits

4.1 Thesymbolsandunitsused throughout thispartof ISO6358shallbe inaccordancewithTable1.

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Table1—Symbolsandunits

Reference Description Symbol Dimensiona SIunitb

6.3.4 Flowarea A L2 m2

3.4.3 Criticalback‐pressureratio b purenumber –

3.4.2 Conductance Ce L4TM‐1 m3/(s.Pa)(ANR)

3.4.2 Sonicconductance C L4TM‐1 m3/(s.Pa)(ANR)

3.4.4 Subsonicindex m purenumber –

6.3.4 Specificheatatconstantpressure Cp L2s‐2Θ‐1 J/kg∙K

6.3.4 Mass–forceconversion g' dimensionless Kg∙m/Ns2

‐ Absolutestagnationpressure p ML‐1T‐2 Pac

6.3.4 Inputpower(e.g.solenoid) P0 ML2T‐3 watt

‐ Massflowrate qm MT‐1 kg/s

‐ Volumeflowrateatstandardreferenceatmosphere qv L3T‐1 m3/s(ANR)

‐ Gasconstant(foraperfectgas) R L2T‐2Θ‐1 J/(kg.K)

‐ Absolutestagnationtemperature T Θ K

6.3.4 Absolutestatictemperature τ Θ K

3.4.5 Crackingpressure Δpc ML‐1T‐2 Pac

3.4.7 Pressuredependencecoefficient Kp M‐1LT2 Pa‐1

‐ Massdensity ρ ML‐3 kg/m3

a M=mass;L=length;T=time;Θ=temperatureb TheuseofpracticalunitsforthepresentationofresultsisdescribedinAnnexFofISO6358‐1.c 1Pa=1N/m2

4.2 Thenumeralsusedassubscriptsandtheasterisk(*)usedasasuperscripttothesymbolslistedinTable1shallbeusedasspecifiedinTable2.

Table2—Subscriptsandsuperscripts

Superscript Subscript Meaning

0 ConditionsofstandardreferenceatmospheredefinedinISO8778,i.e.:

T0=293,15K

p0=100kPa(1bara)

ρ0=1,185kg/m3

65%relativehumidity

1 Upstreamconditions

2 Downstreamconditions

* Conditionsduringchokedflowtests

a 1 bar = 100 kPa = 0,1 MPa; 1 Pa = 1 N/m2

5 Testinstallation

NOTE Figures1and2illustratebasiccircuitsthatdonotincorporateallthesafetydevicesnecessarytoprotectagainstdamage in theeventof component failure. It is important that those responsible forcarryingoutthetestgivedueconsiderationtosafeguardingbothpersonnelandequipment.

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5.1 Testcircuitforconstantupstreampressuretest

5.1.1 Ifpressure‐measuringtubescanbeconnectedontheupstreamanddownstreamsidesofthecomponentundertest,asuitabletestcircuitasshowninFigure1shallbeused.

NOTE SeeTable3forthekeytotestcircuitcomponents.

Figure1—Testcircuitforconstantupstreampressuretest

5.1.2 AnalternativetothistestcircuitisshowninISO6358‐1,AnnexA.

5.2 Testcircuitforvariableupstreampressuretest

Ifthecomponentundertesthasaconnectingportonitsdownstreamside,asuitabletestcircuitas shown in Figure2 shall be used. If the component does not have a connecting port on itsdownstreamside(suchassilencer),thetestcannotbeconducted.

NOTE SeeTable3forthekeytotestcircuitcomponents.

Figure2—Testcircuitforvariableupstreampressuretest

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Table3—KeytotestcircuitcomponentsshowninFigures1and2

Keyitemnumber

Relevantsubclauseorparagraph

DescriptionAdditionalrecommendationsand

requirements

1 5.3.2 Compressedgassourceandfilter

2 ‐ Adjustablepressureregulator

3 ‐ Shut‐offvalve Preferablywithastraightflowpath

4 ‐ Flow‐ratemeasuringdevice Mayalsobeplacedinposition4’(i.e.downstreamofthedownstreampressure‐measuringtube([item10]).

5 ‐ Temperature‐measuringinstrument Sensorlocatedonaxisoftheupstreampressure‐measuringtube(item6).See5.4.2and5.4.3

6 5.4 Upstreampressure‐measuringtube

7 5.5 Upstreamtransitionconnector Attachedtothepressure‐measuringtubeandcomponentundertest

8 ‐ Componentundertest

9 5.5 Downstreamtransitionconnector Attachedtothepressure‐measuringtubeandcomponentundertest

10 5.4 Downstreampressure‐measuringtube

11 ‐ Upstreampressuregaugeortransducer

12 ‐ Downstreampressuregaugeortransducer Adifferentialpressuregaugeortransducer,12’,maybeusedasanalternative.

13 ‐ Flowcontrolvalve Thesonicconductanceofthisflowcontrolvalveshallbeaboutfourtimeslargerthanthatofthecomponentundertest.

14 ‐ Barometer

15 5.6.3 Nipplea NotshowninFigures1and2;seeFigure4.

16 5.6.3 Closenipplea NotshowninFigures1and2;seeFigure4.

a Asanoption,asetofpush‐inconnectorsmayalsobeused.

5.3 Generalrequirements

5.3.1 Thecomponentundertestshallbeinstalledandoperatedinthetestcircuitinaccordancewiththemanufacturer’soperatinginstructions.

5.3.2 A filter shall be installed which provides a standard of filtration specified by themanufacturerofthecomponentundertest.

5.3.3 Atestset‐upshallbeconstructedfromtheitemslistedinTable3,exceptthatitem13isnotrequiredforthevariableupstreampressuretest.

5.3.4 All connections for pressuremeasurement shall be arranged so that entrained liquidcannotbetrappedorretained;adrainmaybeprovidedatanylocationswhereliquidcollects.

5.3.5 Theinletconnectoroftheupstreampressure‐measuringtubeshallhaveagradualprofiletoavoiddisturbanceoftheflow.

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5.3.6 Calibrate the flowmeter (seeAnnexB for information)beforeconducting the test.Fortestsconductedtodetermineorverifycataloguedata,theflowmetershallhavebeencalibratedinaccordancewiththebestpracticesofthelaboratory.

5.3.7 Performadeadweighttestofthepressurerecordinginstrumentationatleastannually.

5.3.8 Instrumentationinacircuitshouldnotbelocatedwherevibrationmayaffectitsaccuracy.

5.4 Pressure‐measuringtubes(items6and10)

5.4.1 Pressure‐measuringtubesthatconformtoFigure3shallbeused.Typicaldimensionsofthepressure‐measuring tubes are also specified inTable4.The tube shall be straight,with asmooth,circularinternalsurface,andaconstantdiameterthroughoutitslength.Thelongitudinalcentrelineofthetubeshall intersectwiththecentrelineoftheholes,andthecentrelineoftheholesshallbenormalto the longitudinalcentreline.The junctionof theholewiththe internalsurfaceofthetubeshallhaveasharpedgeandbefreefromburrs.Thereshallbenoobstructionorbranchconnectionotherthanthosespecified.

Key

1 Endthatconnectstotransitionconnector

2 Pressure‐tappinghole

3 Temperature‐tappinghole‐necessaryinthedownstreampressuremeasuringtubeforcalculatingthepowerloss;butnotrequiredinthedownstreampressuremeasuringtubetodetermineflowcharacteristics.Atemperaturetappingholeisnecessaryontheupstreampressure‐measuringtubeiftemperatureisnotmeasuredupstreamelsewhere.

Figure3—Pressure‐measuringtube

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Table4—Typicaldimensionsofpressure‐measuringtubes

Dimensionsinmillimetres

T2a d1 d2b d3c L1

b L2b L3

min. nom. tol. nom. tol. nom. tol.

G1/8 6 14,5 8 –0,040–0,076 5,5

0–0,2 1 7,5

0–0,4

G1/4 9 18,5 11 –0,050–0,093 6,5 0

–0,4 1,5 9,5 0–0,4

G3/8 12,5 22,5 14,5 –0,050–0,093 7,5 0

–0,4 1,5 10,5 0–0,4

G1/2 16 26,5 18 –0,050–0,093 9 0

–0,4 1,5 12 0–0,4

G3/4 22 32,5 24 –0,065–0,117 10,5 0

–0,4 1,5 13,5 0–0,4

G1 28 39 30 –0,065–0,117 11,5 0

–0,4 1,5 14,5 0–0,4

G11/4 36 49 38 –0,080–0,142 16,5 0

–0,4 2,5 21,5 0–0,4

G11/2 42 55 44,5 –0,080–0,142 17,5 0

–0,4 2,5 22,5 0–0,4

G2 53 68 56 –0,100–0,174 19,5 0

–0,4 2,5 24,5 0–0,4

G21/2 68 80 72 –0,100–0,174 23 0

–0,4 3 29 0–0,4

G3 81 91 84,5 –0,120–0,207 25,5 0

–0,4 3 31.5 0–0,6

a GthreadsinaccordancewithISO228‐1.

b GthreadlengthL1anddimensionsd2andL2inaccordancewithISO16030.

c Limitdeviationsoftoleranceclassd9inaccordancewithISO286‐2.

5.4.2 One temperature‐tapping holemay be provided on the upstreampressure‐measuringtubeinaccordancewithFigure3foratemperature‐measuringsensorthatdoesnotprotrudeintotheflowstream.

5.4.3 Because the location of the upstream temperature sensor does not have a significantimpact on the test results, the temperature sensor can be located in a convenient locationupstreamfromthecomponentundertest.Alternatelocationsofthetemperaturesensorshouldbe in a large‐diameter section of the supply system piping, away from any areas of suddenexpansion.

5.4.4 Whenconnectingpressuremeasuringinstruments,thedeadvolumeshallbelimitedasmuchaspossibletoavoidlongresponsetime.

5.5 Transitionconnectors(items7and9)

Transition connectors shall be made in accordance with the dimensions and requirementsdescribedinISO6358‐1.

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5.6 Specialrequirements

5.6.1 Whentheinletandoutletportsofthecomponentundertestaredifferentinstructureorsizefromthosedescribedabove,oraredifferentfromeachother,pressure‐measuringtubesandtransitionconnectorsthataresuitedtotherelevantportsshallbeused,buttheyshallconforminprincipletothedimensionsshowninISO6358‐1,5.5.

5.6.2 Pressure‐measuringtubesandtransitionconnectorsmaybejoinedorweldedtogetherbymeansotherthanshownifallinternaldimensionsintheflowpatharemaintained,andthepilotfitisusedbetweenthem.

5.6.3 Whenatransitionconnectorinterfereswiththebodyofthecomponentundertest,oranadjacent connector, the variable upstream pressure test shall be performed. In this case, atransitionconnector(item7)shallbeusedwithanipple(item15)orshorttubeconnectedtotheupstreamport.Aclosenipple(item16)shallalsobeinstalledtothedownstreamportasshowninFigure4.Theinsidediameterofthenippleandclosenipple(items15and16)shouldbeequaltotheinsidediameterd1ofthetransitionconnector.

NOTE SeeTable3forthekeytoidentifycircuitcomponents

Figure4—Testarrangementforcomponentwithportsthatareclosetoeachother

5.6.4 Allspecialrequirementsshallberecordedinthetestreport.

6 Testprocedures

6.1 Testconditions

6.1.1 Testfluid

6.1.1.1 Airshouldbeusedasthetestfluid. Ifadifferentfluidisused,itshallbestatedinthetestreport.

6.1.1.2 Thegasshallbefilteredandconditionedtocomplywiththerecommendationsofthemanufacturerofthecomponentundertest.

6.1.2 Checks

Periodicallycheckthatthepressure‐tappingholesarenotblockedbyliquidsorsolidparticles.

6.1.3 Testmeasurements

6.1.3.1 Eachsetof testreadingsshallberecordedaftersteady‐stateconditionshavebeenreached.Thevariationsofpressures,temperatureandflowrateindicationsshallnotexceedthelimitsgiveninthecolumn“Allowedtestconditionsvariation”ofTable5.

6 7 8

16

15

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6.1.3.2 Pressure, temperature and flow rate shall be measured within the measurementaccuracyspecifiedinTable5.Bothtemperaturesensorsshouldbeveryconsistenttoeachother,atleastinthespanofthemeasurement.

NOTE: Thermocouples, Thermistors andRTD’s are themost common types of temperaturemeasuringsensors.However,forthesetests,RTD’swouldbethebestchoicetoachievetheaccuracyrequired.

Table5—Measurementaccuracyandallowedtestconditionvariationofparameters

Parameter MeasurementaccuracyAllowedtest

conditionvariation

Temperature ±0,2K(forpowerloss)Seenoteinclause6.1.3.2

±2K

Pressure ±0,5% ±1%

NOTE SeeISO/IECGuide98‐3:2008andtheGuidetotheexpressionofuncertaintyinmeasurement(GUM:2008fromISO/IEC/BIPM).

6.1.3.3 Flowconditionsineachflowpathshallbemaintainedconstantwithinthecomponentwhiletakingmeasurementstoensurethereisnoinadvertentmovementofcomponentparts.

6.2 Measuringprocedures

6.2.1 Requirementsfortestingtopublishcatalogueratings

Ifdataistobeusedforpublishingratingsinacatalogue,asampleconsistingofaminimumoffivetestunitsselectedfromarandomproductionlotshallbetestedinaccordancewiththefollowingprocedures.

6.2.2 Selectionofmeasuringprocedure

Eithertheproceduredescribedin6.2.3ortheproceduredescribedin6.2.4shallbeselectedinaccordancewiththescopeofthispartofISO6358. IfthealternativetestcircuitinAnnexAofISO6358‐1isused,onlytheproceduredescribedin6.2.3shallbeselected,withthepressuresadjustedasdescribedinA.2andA.3ofISO6358‐1.

6.2.3 Measuringprocedureforconstantupstreampressuretest(seeFigure1)

6.2.3.1 Maintain a constant upstream pressure, p1, of not less than 500kPa (5bar) andpreferablyhigher.Adjustthepressureregulator(item2)asrequiredtomaintainp1ataconstantvaluethroughoutthetestforeachmeasuredpoint.Measuretheatmosphericpressureusingthebarometer(item14).

6.2.3.2 Decreasethedownstreampressure,p2,toitssmallestpossiblevaluebyopeningtheflowcontrolvalve(item13)toitsmaximumflowrate.Intheseconditions,mostcomponentsarechoked.Measureupstreamtemperature,T1*,downstreamtemperature,T2,upstreampressure,p1*,chokedmassflowrate,qm*,anddownstreampressure,p2*.

6.2.3.3 Partlyclose the flowcontrolvalve(item13)stepbysteptoobtain twomoredatapointsinthechokedflowregion.Recordthesameadditionaldataasin6.2.3.2. Allowsufficienttimebetweensettingsforthesystemtostabilize,becausethedatacannotberecordedwhentheflowratevariescontinually.

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6.2.3.4 Continueclosingtheflowcontrolvalve(item13)stepbysteptoobtainatleastfiveapproximatelyequally‐spaceddatapointsinthesubsonicflowregion.Foreachpoint,measureandrecordtheupstreamtemperature,T1,downstreamtemperature,T2,upstreampressure,p1,massflowrate,qm,anddownstreampressure,p2.Thisisadecreasingflowratetest.

6.2.3.5 Toobserveifthecomponentundertesthasdispersionorhysteresis,partlyopentheflowcontrolvalve(item13)stepbysteptomeasurefivepointsspreadoutoverthesubsonicflowregionofpressureratiop2/p1andthreepointsspreadoutoverthechokedflowregion.Thisisanincreasingflowratetest.

Foreachpointinthesubsonicflowregion,measureandrecordtheupstreamtemperature,T1,downstream temperature, T2, upstream pressure, p1, mass flow rate, qm, and downstreampressure,p2.

Foreachpoint inthechokedflowregion,measureandrecordtheupstreamtemperature,T1*,downstream temperature, T2, upstream pressure, p1*, choked mass flow rate, qm*, anddownstreampressure,p2*.

6.2.4 Measuringprocedureforvariableupstreampressuretest(seeFigure2)

6.2.4.1 Settheupstreampressure,p1,toapproximately500kPa(5bar)toensurethattheflow in the component under test is choked. Measure the downstream pressure, p2. If thedownstream transition connector cannot connect to the component under test, measure theatmosphericpressureas p2.

6.2.4.2 Measure the chokedmass flow rate,qm*, upstream temperature,T1*, downstreamtemperature,T2,upstreampressure,p1*,anddownstreampressure,p2*.

6.2.4.3 Adjustthepressureregulator(item2)toreducestepbysteptheupstreampressure,p1,toobtaintwomoredatapointsinthechokedflowregion.Recordthesameadditionaldataasin6.2.4.2. Allowsufficienttimebetweensettingsforthesystemtostabilize,becausethedatacannotberecordedwhentheflowratevariescontinually.

6.2.4.4 Continueadjustingthepressureregulator(item2)stepbysteptoobtainatleastfiveapproximately equally‐spaced data points in the subsonic flow region. For each data point,measure and record the upstream temperature, T1, downstream temperature, T2, upstreampressure,p1,massflowrate,qm,anddownstreampressure,p2.Thisisadecreasingflowratetest.

6.3 Calculationofpowerloss

Determine the power loss from the following equation: 

Powerloss= ompm PqCpApAg

Rq

21

2

22

2

2

11

12

'2

1  

 

See annex A for conversion of stagnation temperature to static temperature. 

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7 Presentationoftestresults

7.1 Allmeasurements,includingtheinsidediameterofthepressure‐measuringtube,andtheresultsofcalculationsshallbetabulatedbythetestinglaboratory.

7.2 Ifdataistobeusedforpublishingratingsinacatalogue,theaverageofresultsfromthetestunitsshallbereported.

7.3 Describethepowerlossasafunctionofvolumetricflowrate(seeexampleinAnnexA).

7.4 The record of the calibration of measuring devices shall be available. In addition, thecalibrationmethodfortemperaturesensorsshallbedescribed.

8 Identificationstatement(referencetothisdocument)

Use the following statement in test reports, catalogues and sales literature when electing tocomplywiththisInternationalStandard:

"Power loss of pneumatic componentsdetermined in accordancewith ISO6358‐5,Pneumaticfluidpower─Determinationof low‐ratecharacteristicsofcomponentsusingcompressiblefluids─Part5: Testmethodtodeterminepowerlossinsteadystateflow.”

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AnnexA(informative)

Powerlossandexampledatacalculation

Introduction

Theprincipleofthismethodistocreateaboundaryaroundthecomponentandaccountforallformsofenergycrossingtheboundary(inandout).

Considertheenergyboundary1‐2ofapneumaticvalvepassingairasshowninFig.A1:

Fig.A1–Energyboundaryofapneumaticvalve

TheenergyequationappliedtotheschematicinFig.A1,includinganenergyloss,wouldbe: (KE + PE + IE + flow work)in + Heat added + Shaft workin + EEin =

(KE +PE + IE + flow work)out + Shaft workout + Energy Losses For components such as valves, filters and piping the shaft work is zero, and the elevation difference (PE) between inlet and outlet is negligible. Also, heat is not added. Therefore, this equation becomes:  (KE+IE+flowwork)in‐(KE+IE+flowwork)out+EEin=EnergyLosses (A1)Thesetermscanbeexpressedasthefollowingforadifferentialelementoffluidmass:

)()()()(2

)()()(2 222222

22

111111

21 LossdEEddtVApdmIdm

VdtVApdmIdm

Vin

(A2)

Wherethesubscripts1and2representinletandoutlet,respectively.And: ψ=mass‐forceconversionunit: 1kg·m/Ns2

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Itisproposedthatthisinitialanalysiswillonlyconsidersteadystateconditions.Then,themassenteringthevalvewillbethesameasthemassleaving:dm1=dm2=dm.Equation(A2)thenbecomes:

)()()()(22 22211121

22

21 LossdEEddtVApVApdmIIdm

VVin

(A3)

Fromthecontinuityequationforadifferentialamountofmassflow: AVdt

dm =qm

Then: dmdtqm )( whereqmismassflowrateandisconstantforsteadystate.Substitutingtheseinto(A3):

) ()()()(22 22211121

22

21 LossdEEddtVApVApdtqIIdtq

VVinmm

(A4)

Equation(A4)resultsinanenergylossintermsofNewtonmeters.Unitscheck:

NmNmss

mm

Pam

N

kPa

PakPa

s

kg

kg

Nm

s

kg

mkg

Ns

s

m

22

32

2

2 10

1

Sincethereisnoshaftwork,itisproposedthattheenergylossbeconvertedtopowerloss.

Poweristherateofenergyuse,so:

t

dtLoss

)(

time

sEnergy Los=Power Loss (A5)

Forsteadystateconditions,allofthetermsinequation(I4)areconstant.Therefore:

)()()()(

22

1)(022211121

22

21 tPtVApVAptqIItq

VV

tt

dtLossmm

(A6)

Where:Po=electricalpowerinput(e.g.solenoids).Thenequation(A5)becomes:

Powerloss= omm PVApVApqIIqVV

22211121

22

21

22 (A7)

Inpneumatics,thedensityoffluidsenteringandleavingacomponentisnotconstant.And,consequently, thevelocityof the fluidsenteringand leavingcannotbeassumedtobe thesameeveniftheflowareasareequal.Fromtheperfectgaslaw:

pv=mRτand p/Rτ=m/v=ρ (A8)

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xiv ©ISO2017–Allrightsreserved

Fromthecontinuityequationatsteadystate:qm=AVρ;thenV=qm/Aρ=qmRτ/Ap (A9)(Iftheinletandoutletareasofacomponentarethesamesize,A1=A2=A.)Substitutingtheseintoequation(A7)

Powerloss= ommm Pq

ppII

pA

Rq

pA

Rq

2

2

1

121

2

22

2

2

11

1 )(2

1

(A10)

Powerloss= omm Pqp

Ip

IpApA

Rq

2

22

1

11

2

22

2

2

11

12

2

1

(A11)

Fromthermodynamics,itisrecognizedthatenthalpy, h=

p

I .Then(A11)becomes:

Powerloss= omm PqhhpApA

Rq

21

2

22

2

2

11

12

2

1

(A12)

Foraperfectgas:(h1–h2)=cp(τ1–τ2)

Where: cp= coefficientof specificheatat constantpressure.

Powerloss= ompm PqCpApA

Rq

21

2

22

2

2

11

12

2

1

(A13)

Avalvemustbe tested inorder toobtain thedatanecessary forequation (A13).Whenconductingsuchatest,thetemperaturemeasurementsobtainedaretypicallystagnationvalues. But, the temperature terms in equation (A13) are static temperatures so aconversion is necessary. This is described by equations (A14) and (A15); theirdevelopmentisdescribedinAnnexC:

K

KTTS 2

411 (A14)

Theconstantisdeterminedfrom:

1

2

2R

Ap

qK m (A15)

γ=1.4(adiabaticconstant)

WhereτS=statictemperatureTT = stagnation temperature

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15

Thefactorαisarecoveryfactor,dependentontheReynoldsandPrandtlnumbers.

d

q

d

dq

A

dqdVN mmm

R

4

42

andk

cN p

Pr (A16)

(Eq.(A9)usedinNR)Forlaminarflow(NR<2,100), PrN (A17a)

Forturbulentflow(NR>2,100), 3PrN (A17b)

TableA1:Variables for the recovery factor α 

Temp.  Dynamic viscosity 

μ 

Specific heat     

cp 

Thermal conduct.   

K 

°C  kg/hr.m  kJ/kg°K  J/hr.m°K 

‐10  0.0598 1.005 84.96

0  0.0616 1.005 87.48

10  0.0634 1.005 90.00

20  0.0652 1.005 92.52

30  0.0668 1.005 95.04

40  0.0684 1.005 97.56

50  0.0702 1.006 100.08

60  0.0720 1.007 102.60

70  0.0736 1.007 105.12

80  0.0752 1.008 107.64

90  0.0769 1.008 110.52

100  0.0785 1.009 113.04

Alldataforthistableisatatmosphericpressure.

Thedynamicviscosityandspecificheatcanbeassumedconstantwithpressure. Thethermalconductivity(at‐20°C),willincreaseapproximately1.8%from1barto10bar;at40°C,theincreaseisapproximately1.0%from1barto10bar.

Measured(stagnation)temperaturescanbeusedinthetable.PneumaticExample:ConsideratestofapneumaticvalveasshowninFig.A2:

Where:μ=dynamicviscosity

cp=specificheat

k=thermalconductivityofair

SeetableA1below.

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xvi ©ISO2017–Allrightsreserved

Fig.A2–Pneumaticvalveinatestcircuit

Sampletestdatafroma½portedvalvewasrecordedfromateston12Aug.2015,asshownin the Excel spreadsheet of Table A2. This test was conducted with RTD sensors fortemperaturemeasurement.Initialcalculationsareshownbelow:d=27.7mm A1=A2=A=(27.74)2(π/4)=604.2mm2 InterpolatingfromTableA1at26°C:μ=0.0662kg/hr.m cp=1.005kJ/kg°K k=94.03J/hr.m°KFromEq.(A16):

m

mm

R qkg

mm

m

mmkgq

d

qN

4.660,41

hr.m0662.0)7.27(

1000

1hr.

min.60

.min4

4

(AEx1)

Fromthedata,itisobservedthatqm>1,thereforealloftheflowisturbulent.Then,equation(I17b)isapplicable:

891.03

Khr.m03.94

10005.1

hr.m0662.0

3

33Pr

J

Kkg

Jkg

k

cN p

(AEx2)

Kp

q

Ns

mkgKkg

Nm

mPa

NPapmm

m

mm

s

kgq

R

Ap

qK m

m

m

10278.0

4.1

14.1

12

287

102.604

1

10

60

.min1

.min891.0

1

2

2

2

2

232

2

26

2

ValuesofKmustbecalculatedforboththeinletandoutletsides.Temperaturesforbothsidesarethencalculatedfromequation(A14).Finally,thepowerlossisdeterminedfromEq.(A13):

(AEx3)

ISO/CD6358‐5:2018

17

Nm

hrw

hr

kgq

KkJ

Nm

Kkg

kJ

N

mPa

Pa

K

ppNs

mkgs

mm

mmm

Kkg

Nmkgq

PL m

m

6

3

21

3

2

42

26

22

2

2

2

1

1

2

2

22

26

22

106.3

.10

.1

.min60

.min

)(10

005.1

1012

3600

.min1

10

12.604

287.min

Powerloss= mm qpp

q

21

2

2

2

2

1

12 75.165223.0 watts (AEx5)

Po=0(electricalpowerinput)isconsideredzeroforthisexample.TableA2showsthecalculationsfromanExcelspreadsheet.Volumetricflowrateatstandardconditionsisdeterminedfrom:

qm=AVρ=qvρ sinceρ=p/Rτ0=p0/Rτ0 wherethesubscript0denotesstandardconditions(p0=100kPa;τ0=20°C).

s

lq

m

l

Pam

NPa

KKkg

Nm

s

kgq

p

Rqqq mm

mmv 025.14

10

10100

202.273287

60

.min1

min 3

3

230

0

(AEx6)

AgraphoftheresultsisshowninFig.A3below.

Fig.A3–TestresultsforPowerLoss

0

50

100

150

200

250

300

350

400

450

500

0 50 100 150 200

Power loss ‐watts

Flow rate ‐ l/s

Power loss in ½" port air valve

8.5 bar nominal

5.7 bar nominal

3.8 bar nominal

(AEx4)

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xviii ©ISO2017–Allrightsreserved

TableA2alsohastwocolumnshighlightedinredandblue,demonstratingtheamountofpowerlossattributedtothekineticenergyportion(inred)andenthalpyportion(inblue).Thiscorrespondstothetermslikewisecolouredinequation(AEx5)repeatedbelow:Powerloss= watts (AEx5) Notethatthesearedifferencesbetweeninletandoutletconditions.AtestusingThermocouplesforthetemperaturesensorswasconductedon28Oct.2011,during the earlydevelopmentof this standard.The inaccuratedata required correctiveassumptionsonthedownstreamtemperaturereadingsinordertoavoidnegativeresults.Fig.A.4isagraphofresultsat3.5barnominalinletpressuredemonstratingthata½°CadjustmentiscomparabletotheresultsobtainedfromRTDsensors,unadjusted.

Fig.A.4ComparisonofthermocoupledatavsRTDdata.

Inthisgraph,thelegendshowsresultswhenadjustmentsaremadetothermocoupledata(e.g ‐0.5 T is a negative ½ °C adjustment made for thermocouple data; 0 RTD is noadjustmentmadetoRTDdata).TheuseofRTD’s inthistestgavemoreaccurateresultsthanobtainedfromthethermocouples.

‐40

‐20

0

20

40

60

80

100

120

140

160

180

0 20 40 60 80 100

Power Loss ‐Watts

Flow rate ‐ l/s

Power consumption of 1/2 port valve

3.5 bar   0 T

3.5 bar  ‐.25 T

3.5 bar   ‐0.5 T

3.5 bar   ‐1 T

3.5 bar   0 RTD

mm qpp

q

21

2

2

2

2

1

12 75.165251.0

ISO/CD6358‐5:2018

19

TableA2‐Testdataandcalculations

ISO/CD6358‐5:2018

1

AnnexB(informative)

Flowmetercalibration

B.1 General

Theflowmeterisadelicatemeasuringinstrumentandshallbecheckedfrequently.Aflowmetermayhavetwolevelsofcalibration:

a) Aprimarycalibration,performedinaccordancewithlegalmetrologyrules,resultinginacalibrationcurveassociatedwithameasurementuncertainty.Fromthis,acalibrationtableorasetoffunctionsisusedforcorrectionstotheflowmeterreadingswhenusedinalaboratory.

b) A secondary calibration checking performed by comparison to a primary device, which permitsverifying thatprecisionandbias continue tobeunderadequate control.Theseverifications canbemadefrequentlyandquicklyandcanusereferencedevicessuchasfixedorificeor,preferably,Venturinozzles.

B.2 Referencedevices

CriticalflowVenturinozzlesarewidelyusedasflowmeters,checkstandards,andtransferstandards.Thepopularityofthesedevicesisaresultoftheirexcellentlong‐termreproducibility,simplegeometricdesign,straightforwardapplication,andwellunderstoodphysics.

TheflowmetercalibrationcheckinthisannexcomparestheflowmeterreadingstothoseofthereferenceVenturinozzles.

ISO9300specifiesthegeometryandmethodofuse(installationinasystemandoperatingconditions)ofcriticalflowVenturinozzles(CFVN)usedtodeterminethemassflowrateofagasflowingthroughasystem.

B.3 Flowmetercalibrationcheckingprocedure

B.3.1 Atypicalset‐upforacalibrationisshowninFigureB.1,butotherarrangementsarepossible:

B.3.2 Recordthebarometricpressure.

B.3.3 Asflowpassesthroughthesystem,recordthepressuresandtemperatures.

B.3.4 Comparetheflowmeterreadingstothoseofthereferencedevice.

B.3.5 Preparecorrectionfactorstoapplytotheflowmeterreadingsforuseduringtesting.

ISO/CD6358‐5:2018

ii ©ISO2017–Allrightsreserved

Key

1 airsupply

2 flowmeterbeingcalibrated

3 referenceVenturinozzle

4 flowcontrolvalve

5 exhausttoatmosphere

FigureB.1—Circuitforflowmetercalibration

B.4 Applicationtotestdata

Applythecorrectionfactorstotheflowmeasurementsmadeduringatestrun,andusethecorrectedresultsasthefinaldata.

1 2 3 4 5

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AnnexC(informative)

Developmentofequationforconverting

StagnationtemperaturedatatoStatictemperature

C.1Introduction:

Temperaturemeasurementsinapneumatictestwithflowingairistypicallymeasuredbyaprobeintotheflow stream, or from a tap in the side wall of a conduit. This is considered a stagnation temperaturemeasurement because the flow stream has to come to a stop (or nearly so) at the sensor. But,thermodynamicequationsarebasedonthetemperatureofthefluidinmotion–asifathermometerweremovingalongwiththeflowstream.Thatisastatictemperature.

C.2Analysis:

Thebasicconceptforatemperaturemeasurementis(Ref.C.1): (C.1)

Modifyingthetermfordynamictemperature(Ref.C.2):

pc

V

2TT

2

svspi (C.2)

Fromthecontinuityequation:

AV=G andA

G=V (C.3)

Fromtheequationofstateforaperfectgas:

smRpv and

v

m

R

p

s

(C.4)

Substituting(C.4)into(C.3)andsquaring:

22

2

2sR

Ap

GV

(C.5)

Fromthermodynamics:

1R

cp (C.6)

Substituting(C.5)and(C.6)into(C.2):

Where:Tt=total(≈stagnation)temperature.

τs=statictemperature.

Tv=dynamictemperature

Tpi = equilibrium temperaturesensed byastationary,idealgeometry, adiabaticprobe.

α=recoveryfactor(dimensionless)

A=areaofflow

Cp = specific heat at constantpressure

G=massflowrate

pc

V

2TT

2

svst

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iv ©ISO2017–Allrightsreserved

R

R

Ap

GT s

spi

2

1222

(C.7)

Let:

1

2

2R

Ap

GK (C.8)

Equation(C.7)cannowbewrittenas:

02 piss TK (C.9)

Thisisaquadraticequationwhosesolutionis:

K

KTpi

s 2

411 (C.10) Thepositivesignischosenfortheradical.

Thisisthestatictemperaturetobeusedinthermodynamicequations,andisshownasequationA.14.Itisusedwithequation(C.8)forK,whichisalsoshownasequationA.15.

TherecoveryfactorαisdeterminedfromthePrandtlnumberandtheReynoldsnumbers:

k

cN p

Pr

d

G

d

Gd

A

dGdVNR

4

42

Forlaminarflow(NR<2,100), PrN

Forturbulentflow(NR>2,100), 3PrN

References:

C.1FundamentalsofTemperature,Pressure,andFlowMeasurementsbyRobertP.Benedict JohnWiley&Sons,Inc.1969;Equation(10.6).

C.2Ibid;Equation(10.9).C.3Ibid;p.135,Par.2whichisquotedasfollows:“InsummarywhenthePrandtlnumberofagasdiffers

fromone,orwhenanisentropicassumptionisnotjustified,totaltemperaturereducestoaconcept.Undertheseconditionseventheadiabaticprobewhichcompletelystagnatesarealgaslocallywillnotindicatethetotaltemperature(realgas,idealizedprobe);thatis,Tpi=τs+αTv≠Tt whereαistherecoveryfactorwhich,ifbasedonlocalvaluesofdirectedvelocityandstatictemperature(justclearoftheboundarylayer),isapproximatelyindependentoftheMach

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5

andReynoldsnumbers,andiswellrepresentedby α=Pr½forlaminarflowandbyα=Pr⅓forturbulentflow.”