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FUGITIVEEMISSIONCONTROLWorld51EmissionmeasurementsofindustrialvalvesaccordingtoTALuftandENISO15848-1Asthetitlesuggests,inthisarticleProfessorDr.-IngAlexanderRiedllooksintotheimplicationsofmeasuringemissionsaccordingtoTALuftandENISO15848-1andpointsoutsomeimportantconclusions.ProfessorDr.-Ing.AlexanderRiedl,UniversityofAppliedSciencesMuenster,GermanyTALuftInasmuchastheyrelatetoGermany,the“TechnischeAnleitungzurReinhaltungderLuft”(TechnicalGuidelinesforAirPollutionControl,orTALuftforshortandreferredtohereinafterasTALuft)[1]arelikealawincharacter.Amongotherthings,theypursuetheobjectiveofreducingemissionswithgasketsystemsasnormallyusedinthechemicalsandpetrochemicalindustries.TALuftonlygivesguidelinesinrespectofcompliancewithpermissibleleakagelimitsandreferstoregulationswhichdefinebasicconditionsforinspections.Forshutoffandregulatingvalves,thisaffectsVDI(AssociationofGermanEngineers)Guideline2440[2],whichmayberegardedasstate-of-the-artfromalegalperspective.VDI2440GuidelineVDI2440referstoaveragegas-likeemissionsfordifferinggasketsystemsbutthesearenotupperlimits(seeTable1).RiedlArticle(3pp)12/6/0710:59Page1World53Table1–Averagegaseousemissions(leakage)andvalvegaskets[1]GasketsystemLeakagerelatedtotheaveragesizeofthegasket[mg/(sxm)]Stuffingboxwithpacking1.0Stuffingboxwithcupleather,O-ring0.1Stuffingboxwithpacking,stuffingboxwithcupleather,0.01O-Ring(withTAAirCertificateaccordingtoVDI2440,Section3.3.1.3)Metallicbellows,sealed0.01Metallicbellows,sealed(withflatgasketpossessing0.001aTALuftCertificateaccordingtoVDI2440)Stuffingboxwithpackingandsealingmedium/suction,Noemissionmetallicbellows,weldedonbothsides(technicallyleak-proof)VDI2440referstotheuseofhigh-qualitymetallicbellowswithadownstreamsafetystuffingboxorequivalentgasketsystemsasaparticularlyeffectivemeansofreducingemissions.Inotherwords,metallicbellowsandso-called“equivalentgasketsystems”areestablishedasconformingtoTALuft.ThismeansthatonlythesekindsofgasketsystemsmaybeusedinGermanyonshutoffandregulatingvalveswhenaTALuftmediumissubsidised.Gasketsystemsmayberegardedasequivalentiftheyfulfilthefollowingconditions:(1)Theconstructionofthegasketsystemcanbeexpectedtopermititsregulationfunctionunderoperatingconditions.(2)Compliancewithspecificleakageratewithreferencetotheaveragesizeofthegasket,from10-4mbarxl/(sxm)attemperaturesoflessthan250°Candfrom10-2mbarxl/(sxm)attemperaturesonthegasketsystemofgreaterthan250°Cisprovenatthefirstinspection.Nospecificexplanationisgivenonconstructionunder(1)astowhythisguidelineisdifficulttounderstand.Ontheotherhand,thedeterminationofaleakageratetobecompliedwithunder(2)forallgasketsexceptmetallicbellowsiscrucialinordertogetvalvesthatfulfiltheconditionsofthiscertificateontothemarket.GuidelineVDI2440describesatestingprocedurewithwhichtheabove-mentionedcertificatecanbeshown.Theancillaryconditionshereare:(1)testingmedium:helium;(2)testingpressure:nominalpressure;(3)testingtemperature:permissibleoperatingtemperature;(4)beforethetest,arepresentativenumberofswitchingcyclesiscarriedoutdependingontheoperatingconditions(switchingrate);(5)test:withstaticandmovingspindle/shaft;(6)leakrate:leakageresultingafteratleast24-houradmissionflowwithheliumunderthegiventestingconditions.Iftheleakin(6)islessthan10-4mbarxl/(sxm)(upto250°C)or10-2mbarxl/(sxm)(over/thesameas250°C),thevalvemayberegardedasTALuftcompliantandmaybeusedwithTALuftmedia.ENISO15848-1ISOnormENISO15848-1[3]hasbeenvalidsince2006.Itrefersexclusivelytovalvesanddescribes,independentoftheguidelinesofTALuftandVDI2440respectively,detailedtestsfordeterminingleakageandthecreepbehaviourofvalves.ThenormwasdevelopedundertheoverallcontroloftheCEN/TC69“IndustrialValves”Committee.Thenormdistinguishesbetweenthefollowingparameters:(1)3gradesofimperviousnessforthespindle/shaft;(2)agradeofimperviousnessforthebodygasket;(3)2testingmedia(heliumandmethane);(4)3gradesoffirmness;(5)5gradesoftemperature;and1distinctionbetweenshutoffandregulatingvalves.Table2[3]showsthefollowinggradesofimperviousnessfordiespindleandtheshaft:Table2–Gradeofimperviousness/leakageareasGradeMeasuredleakageRemarksratemg/(sxm)ATypicallyachievedwithbellowsgasketsoranequivalent(heliumonly)≤10-6spindle/shaftgasketsystemforswivelvalves.B≤10-4TypicallyachievedwithpackingonaPTFEbasisorelastomerpacking.C≤10-2Typicallyachievedwithpackingonthebasisofflexiblegraphite.Therequiredimperviousnessforthebodygasket,measuredusingthesniffingmethod,maynotexceed50ppmv(1ppmv=1cm3x/m3).Inrespectofthemedia,thenormisnotintendedtoachieveanycomparability,butlessleakagemaybeexpectedthanwithhelium.However,thisstatementrequirestesting.Theleakagetestsareconductedbothatroomtemperatureandatmaximumoperatingtemperature,takingcyclesofdifferinglengths.Thegasketconnectionmayonlybere-tightenedtoalimitedextent.AtthemomenttheauthordoesnotknowwhetheranyEuropeancountryortheEUhasadoptedthenorminordertoconvertthelimitsdescribedhereintonationalorEuropeanlaw.Throughthepreciseguidelines,however,itisexpectedthatthiswillbeca