Designation:D4888−06(Reapproved2015)StandardTestMethodforWaterVaporinNaturalGasUsingLength-of-StainDetectorTubes1ThisstandardisissuedunderthefixeddesignationD4888;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1Thistestmethodcoversaprocedureforrapidandsimplefielddeterminationofwatervaporinnaturalgaspipelines.Availabledetectortubesprovideatotalmeasuringrangeof0.1to40mg/L,althoughthemajorityofapplicationswillbeonthelowerendofthisrange(thatis,under0.5mg/L).Atleastonemanufacturerprovidestubesthatreaddirectlyinpoundsofwaterpermillioncubicfeetofgas.SeeNote1.1.2Detectortubesareusuallysubjecttointerferencesfromgasesandvaporsotherthanthetargetsubstance.Suchinter-ferencesmayvaryamongbrandsbecauseoftheuseofdifferentdetectionmethods.Consultmanufacturer’sinstructionsforspecificinterferenceinformation.Alcoholsandglycolswillcauseinterferencesonsomewatervaportubesbecauseofthepresenceofthehydroxylgrouponthosemolecules.1.3Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafetyandhealthpracticesanddeterminetheapplica-bilityofregulatorylimitationspriortouse.2.SummaryofTestMethod2.1Thesampleispassedthroughadetectortubefilledwithaspeciallypreparedchemical.Anywatervaporpresentinthesamplereactswiththechemicaltoproduceacolorchangeorstain.Thelengthofthestainproducedinthedetectortube,whenexposedtoameasuredvolumeofsample,isdirectlyproportionaltotheamountofwatervaporpresentinthesample.Ahand-operatedpistonorbellows-typepumpisusedtodrawameasuredvolumeofsamplethroughthetubeatacontrolledrateofflow.ThelengthofstainproducedisconvertedtomilligramsperlitreofH2Obycomparisontoacalibrationscalesuppliedbythemanufacturerforeachboxofdetectiontubes.Thesystemisdirectreading,easilyportable,...
