Designation:D7278−21StandardGuideforPredictionofAnalyzerSampleSystemLagTimes1ThisstandardisissuedunderthefixeddesignationD7278;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.INTRODUCTIONLagtime,asusedinthisguide,isthetimerequiredtotransportarepresentativesamplefromtheprocesstaptotheanalyzer.Samplesystemdesignshaveinfiniteconfigurationssothisguidegivestheuserguidance,basedonbasicdesignconsiderations,whencalculatingthelagtimeofonlinesampledeliverysystems.LagtimeoftheanalyzersamplesystemisarequiredsystemcharacteristicwhenperformingsystemvalidationinPracticeD3764,D6122,orD8321andingeneraltheproperoperationofanyonlineanalyticalsystem.Theguideliststhecomponentsofthesystemthatneedtobeconsideredwhendetermininglagtimeplusameanstojudgethetypeofflowandneedformultipleflushesbeforeanalysisonanysample.1.Scope*1.1Thisguidecoverstheapplicationofroutinecalculationstoestimatesamplesystemlagtime,inseconds,forgas,liquid,andmixedphasesystems.1.2Thisguideconsidersthesourcesoflagtimefromtheprocesssampletap,tapconditioning,sampletransport,pre-analysisconditioningandanalysis.1.3Lagtimesareestimatedbasedonapredictionofflowcharacteristics,turbulent,nonturbulent,orlaminar,andthecorrespondingpurgerequirements.1.4Mixedphasesystemspreventreliablerepresentativesamplingsosystemlagtimesshouldnotbeusedtopredictsamplerepresentationofamixedphasestream.1.5Thevaluesstatedininch-poundunitsaretoberegardedasstandard.OtherunitsofmeasurementareincludedinthisstandardandAppendixX1exampleswherenormallyseeninindustry.1.6Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafety,health,andenvironmentalpracticesanddeter-minetheapplicabilityofregulatorylimitationspriortouse.1.7Thisinternationalstandardwasdev...
