Designation:D1988−20StandardTestMethodforMercaptansinNaturalGasUsingLength-of-StainDetectorTubes1ThisstandardisissuedunderthefixeddesignationD1988;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1Thistestmethodcoversarapidandsimplefielddeter-minationofmercaptansinnaturalgaspipelines.Availabledetectortubesprovideatotalmeasuringrangeof0.5to160ppmbyvolumeofmercaptans,althoughthemajorityofapplicationswillbeonthelowerendofthisrange(thatis,under20ppm).Besidestotalmercaptans,detectortubesarealsoavailableformethylmercaptan(0.5to100ppm),ethylmercaptan(0.5to120ppm),andbutylmercaptan(0.5to30mg/M3or0.1to8ppm).NOTE1—Certaindetectortubesarecalibratedintermsofmilligramspercubicmetre(mg/M3)insteadofpartspermillionbyvolume.Theconversionisasfollowsfor25°C(77°F)and760mmHg.mg/M35ppm3molecularweight24.45(1)1.2Detectortubesareusuallysubjecttointerferencesfromgasesandvaporsotherthanthetargetsubstance.Suchinter-ferencesmayvaryamongbrandsbecauseoftheuseofdifferentdetectionprinciples.Manydetectortubeswillhaveapre-cleanselayerdesignedtoremoveinterferencesuptosomemaximumlevel.Consultmanufacturer’sinstructionsforspe-cificinterferenceinformation.Hydrogensulfideandothermercaptansareusuallyinterferencesonmercaptandetectortubes.SeeSection6forinterferencesofvariousmethodsofdetection.1.3Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafety,health,andenvironmentalpracticesanddeter-minetheapplicabilityofregulatorylimitationspriortouse.Forspecifichazardstatements,see8.3.1.4Thisinternationalstandardwasdevelopedinaccor-dancewithinternationallyrecognizedprinciplesonstandard-izationestablishedintheDecisiononPrinciplesfortheDevelopmentofInternationalStandards,GuidesandRecom-mendation...
