油液污染度检测仪 激光油液颗粒计数器ISO标准的改变对测试的影响

1ImpactofChangestoISOStandardsonContaminationControlProgramsbyLeonardBensch,PallCorporationABSTRACTFluidcontaminationisgenerallyconsideredtheprimarycauseofhydrauliccomponentwearandreductioninsystemreliabilityandperformance.Becauseofthis,mostcompanieshavesometypeofcontaminationcontrolprograminplace,whichincludestheapplicationoffiltrationandfluidconditionmonitoringbyparticlecounting.TheimpendingadoptionoffourneworrevisedISOfluidpowerstandardsisgoingtohaveamajorimpactonsuchcontaminationcontrolprograms.TheprimarychangesareresultingfromtheobsolescenceofACFineTestDust(ACFTD),atestcontaminantthathasbeenutilizedforseveraldecadesforprimarycalibrationofautomaticparticlecountersandforfiltertesting.Althoughtherearereplacementdusts,noneofthemhaveanidenticalparticlesizedistributiontoACFTD,therefore,allassociatedtestresultsaresomewhatdifferent.Thispaperpresentstypicalchangesfoundwiththenewdustsincludingtheimpactonautomaticparticlecountercalibration,resultantparticlesizesandcounts,andfilterperformance-bothefficiencyofparticlecaptureanddirtcapacity.Itshouldbepointedoutthat,althoughlaboratoryresultsandperformanceinterpretationswillchange,thisisanartifactofthetestingonly,andfilterperformanceandactualcontaminationlevelsinthefieldwillremainthesameasbefore.INTRODUCTIONANDHISTORICALBACKGROUNDPriortodetailingtheimpactofthechangesthatwilloccur,thissectionpresentsbackgroundinformationandthepreviousstatusofthevariousparametersandtestprocedures.PARTICLECOUNTING––Thefirstmethodofcountingparticlesinahydraulicfluidsamplewasmostlikelythroughtheuseofamicroscope.Thistechnique,whichisstillinusetoday,involvesfilteringasampleofthefluidthroughafinemembranefilterthenexaminingitunderamicroscope.Particlesaresized,usuallybasedontheirlongestchorddimension,andcounted.Theresultsaregenerallyreportedasnumberofparticlesperunitvolumeoffluidinaspecificparticlesizerange.Liquidopticalautomaticparticlecounterscameintobeingforhydraulicfluidanalysisinthelate1960sandtheirusehasgraduallyreplacedmicroscopictechniquesinmostindustries.Suchautomaticparticlecounters,termedAPCs,generallyfunctionthroughtheprincipleoflightobscuration.Alightbeam,mostcommonlyfromalaserdiodesource,istransmittedthroughthefluidpassingthroughtheAPCsensor.Particlesinthefluidsampleabsorborscatterlightinproportiontotheirsize.Thetransmittedorscatteredlightismeasuredbyaphotodectorandtheresultingsignalstrengthisusedtodeterminetheparticlesize.Inthelate1960saprojectwasinitiatedtodevelopacalibrationprocedurewiththegoaltoensurethatparticlecountsobtainedwithanAPCagreedascloselyaspossiblewithcountsobtainedbyopticalmicroscopy.Thecalibrationprocedure,whichultimatelybecameaninternationalstandard,ISO4402[1],isstillinusetodaybymostfluidpowerlaboratoriesaroundtheworld.ItisbasedonmicroscopicsizingandcountingwhichwasperformedonACFineTestDustusingthelongestchorddimension.ThiscalibrationproceduregaveusersconfidenceintheuseofAPCsandtheyarecurrentlyutilizedinlaboratoriesandthefieldtomeasuretheparticlesizedistributionofafluidsample,eitheron-lineorcollectedfromtheoperatingsysteminasamplebottle.AIRCLEANERFINETESTDUST–ThemostcommonlyusedtestdustinthefluidpowerindustrywasAirCleanerFineTestDust,alsocalledACFineTestDustorACFTDwhichwasoriginallysoldbytheACSparkPlugDivision(latertheACRochesterDivision)ofGeneralMotorsCorporation.Itwasmanufacturedbycollectingdust,primarilysilica,fromacertainareainArizonathenballmillingandclassifyingitintoaconsistentparticlesizedistributionincludingparticlessizesfromroughly0-100µm.BecauseoftheconsistentparticlesizedistributionofACFTDanditsirregularparticleshape,believedtoberepresentativeofcontaminantsfoundintypicalhydraulicsystems,itwaschosenin1969-1970forthedevelopmentofthepreviouslymentionedcalibrationprocedureforautomatic,liquidborne,opticalparticlecounters.TheparticlesizedistributionforACFineTestDustdefinedinISO4402andshowngraphicallyinFigure1isusedtosettheelectronicthresholdlevelsthatdefinetheparticlesizesmeasuredinaparticlecounter.InadditiontoAPCcalibration,ACFineTestDustaswellasothersimilardustslikeACCoarseTestDustwereusedformanyotherpurposesinthecontaminationcontrolfield.Asanexample,ACFTDwasusedforfilterperformancetestingtomeasureboththeefficiencyanddirtcapacityofhydraulicandlubeoilfilters.Itwasalsousedeitherasreceivedor2afterseparatingintospecificparticlesizeintervalsfortestingthecontaminantsensitivityofhydrauliccomponents.In1992,ACRochesterdiscontinuedmanufacturingtheseACDusts,andSAEandISOTechnicalCommitteeTC22startedeffortstofindreplacementdusts.1101001,00010,000Particlesize,µmParticles/µgsize123510154020Logvs.log-squaredplotFigure1.ACFineTestDustSizeDistributionBasedonLongestChordDimensionFLUIDCLEANLINESSCLASSIFICATIONSTANDARDS-TheISOCleanlinessCode,ISO4406,1987[2]isthemostwidelyusedInternationalstandardforrepresentingthecontaminationlevelofindustrialfluidpowersystems.TheISO4406classificationisatwonumbercode,e.g.,14/12,basedonthenumberofparticlesgreaterthan5µmand15µmrespectively.ItwasexpandedtothreenumbersinISODIS4406,1996[3]bytheadditionofacodenumberrepresentingthenumberofparticles