露点温度法测定气体燃料中蒸汽含量的试验方法

文档简介标准号：D1142-95标准全称应该翻译为：“露点温度法测定气体燃料中蒸汽含量的试验方法”ASTMD1142-95（2006）StandardTestMethodforWaterVaporContentofGaseousFuelsbyMeasurementofDew-PointTemperatureSignificanceandUseGenerally,contractsgoverningthepipelinetransmissionofnaturalgascontainspecificationslimitingthemaximumconcentrationofwatervaporallowed.Excesswatervaporcancausecorrosiveconditions,degradingpipelinesandequipment.Itcanalsocondenseandfreezeorformmethanehydratescausingblockages.Water-vaporcontentalsoaffectstheheatingvalueofnaturalgas,thusinfluencingthequalityofthegas.Thistestmethodpermitsthedeterminationofwatercontentofnaturalgas.1.Scope1.1Thistestmethodcoversthedeterminationofthewatervaporcontentofgaseousfuelsbymeasurementofthedew-pointtemperatureandthecalculationtherefromofthewatervaporcontent.Note1Somegaseousfuelscontainvaporsofhydrocarbonsorothercomponentsthateasilycondenseintoliquidandsometimesinterferewithormaskthewaterdewpoint.Whenthisoccurs,itissometimesveryhelpfultosupplementtheapparatusinwithanopticalattachmentthatuniformlyilluminatesthedewpointmirrorandalsomagnifiesthecondensateonthemirror.Withthisattachmentitispossible,insomecases,toobserveseparatecondensationpointsofwatervapor,hydrocarbons,andglycolaminesaswellasicepoints.However,ifthedewpointofthecondensablehydrocarbonsishigherthanthewatervapordewpoint,whensuchhydrocarbonsarepresentinlargeamounts,theymayfloodthemirrorandobscureorwashoffthewaterdewpoint.Bestresultsindistinguishingmultiplecomponentdewpointsareobtainedwhentheyarenottoocloselyspaced.Note2Condensationofwatervaporonthedew-pointmirrormayappearasliquidwaterattemperaturesaslowas0to10F（18to23C）.Atlowertemperaturesanicepointratherthanawaterdewpointlikelywillbeobserved.Theminimumdewpointofanyvaporthatcanbeobservedislimitedbythemechanicalpartsoftheequipment.Mirrortemperaturesaslowas150F（100C）havebeenmeasured,usingliquidnitrogenasthecoolantwithathermocoupleattachedtothemirror,insteadofathermometerwell.