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©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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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.
ISO/CD6358‐5:2018
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
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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
ISO/CD6358‐5:2018
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
ISO/CD6358‐5:2018
5
andReynoldsnumbers,andiswellrepresentedby α=Pr½forlaminarflowandbyα=Pr⅓forturbulentflow.”