API STD 管道有关的焊接

1DateofIssue:July2007AffectedPublication:APIStandard1104,WeldingofPipelinesandRelatedFacilities,October2005.ERRATA/ADDENDUMPleaseinsertthefollowingchangestoStd1104:Section3.2.2,Change:“branchweld:Thecompletedweldjoiningabranchpipeorbranchfittingtoarunpipe.”to“branchweld:Thecompletedgrooveand/orfilletweldjoiningasetonorsetinbranchpipeorasetonorsetinbranchfittingtoarunpipe.”PleasereplaceAppendixAwiththefollowingattachment:47APPENDIXA—ALTERNATIVEACCEPTANCESTANDARDSFORGIRTHWELDSA.1GeneralTheacceptancestandardsgiveninSection9arebasedonempiricalcriteriaforworkmanshipandplaceprimaryimportanceonimperfectionlength.Suchcriteriahavepro-videdanexcellentrecordofreliabilityinpipelineserviceformanyyears.Theuseoffracturemechanicsanalysisandfitness-for-purposecriteriafordeterminingacceptancecriteriaisanalternativemethodandincorporatestheeval-uationofbothimperfectionheightandimperfectionlength.Typically,butnotalways,thefitness-for-purposecriteriaprovidemoregenerousallowableimperfectionlength.Additionalqualificationtests,stressanalysis,andinspectionarerequiredtousethefitness-for-purposecrite-ria.Performinganalysisbasedontheprinciplesoffitness-for-purposeisalternativelytermedengineeringcriticalassessment,orECA.Thefitness-for-purposecriteriainthepriorversionsofthisappendixrequiredaminimumCTODtoughnessofeither0.005or0.010in.andwereindependentofanyhighervaluesoffracturetoughness.Improvementsinweldingconsumablesandwithmorepreciseweldingpro-cedures,especially,withtheincreaseduseofmechanizedweldingdeviceshaveresultedinhigherandmoreuniformtoughnessandductilityinmostwelds.Atthesametime,toughnessvaluesbelow0.005in.havebeenobserved,par-ticularlywithmorestringentnotchingproceduresofCTODspecimensthanthoseinthepriorversionsofthisappendix.Weldswithtoughnessbelow0.005in.haveshowntoperformadequatelywhentheacceptancecriteriaareproperlyadjustedtoaccountforthelowertoughness.Theacceptancecriteriaarerevisedsothattheyarecom-mensuratewiththemeasuredtoughnessandappliedloadlevels.Thisappendixincludesthreeoptionsforthedetermina-tionofacceptancelimitsofplanarimperfections.Innumericalorder,theoptionsareincreasinglycomplexinapplicationbutofferwiderrangeofapplicability.Option1providesthesimplestmethodology.Option2allowsforthefullutilizationofthetoughnessofthematerialsthusprovidingamoreaccuratecriterionbutrequiresmorecal-culation.Thefirsttwooptionsweredevelopedwithasin-glesetofunderlyingproceduresbutarelimitedtoapplicationswithalowtomoderatefatigueloadingasdescribedinA.2.2.17.Option3isprovidedprimarilyforthosecaseswherefatigueloadingexceedsthelimitestab-lishedforthefirsttwooptions.Option3isnotprescriptiveanditsconsistencycouldbesignificantlylessthanOptions1and2.Option3shouldonlybeexercised,whenneces-sary,byskilledpractitionerswithdemonstratedknowledgeoffracturemechanicsandpipelineloadanalysis.Withthesethreeoptionsthiscurrentrevisionoftheappendixshouldprovideamorecompleteapproachtodetermineinspectionandacceptancelimitsforimperfections.ItisusuallyimpracticaltoqualifyindividualpipelineweldsforthealternativeacceptancelimitsafteradefectunderSection9isdetected,becausedestructivetestingisrequiredtoestablishtherequiredmechanicalpropertiesfortheweld-ingprocedureunderconsideration.Thisappendixprovidesprocedurestodeterminethemaxi-mumallowableimperfectionsizes.ItdoesnotpreventtheuseofSection9fordeterminingimperfectionacceptancelimitsforanyweld.Useofthisappendixiscompletelyatthecom-pany’soption.Inthisappendix,theuseofthephraseimperfectionaccep-tancelimitsandotherphrasescontainingthewordimperfec-tionisnotintendedtoimplyadefectiveconditionoranylackofweldintegrity.Allweldscontaincertainfeaturesvariouslydescribedasartifacts,imperfections,discontinuities,orflaws.Thesetermsarewidelyacceptedandusedinterchangeably.Theprimarypurposeofthisappendixistodefine,onthebasisofatechnicalanalysis,theeffectofvarioustypes,sizes,andshapesofsuchanomaliesonthesuitabilityofthewholeweldforaspecificservice.Thisuseofthisappendixisrestrictedtothefollowingconditions:•Circumferentialweldsbetweenpipesofequalnomi-nalwallthickness.•Nondestructiveinspectionperformedforessentiallyallwelds.•Nogrossweldstrengthundermatching,seeA.3.2.1.•Maximumaxialdesignstressnogreaterthanthespec-ifiedminimumyieldstrength(SMYS).•Maximumaxialdesignstrainnogreaterthan0.5%.•Weldsinpumpandcompressorstations,repairwelds,fittingsandvalvesinthemainlineareexcluded.A.2StressAnalysisA.2.1AXIALDESIGNSTRESSTousethisappendix,astressanalysisshallbeperformedtodeterminethemaximumaxialdesignstressestowhichthegirthweldsmaybesubjectedtoduringconstructionandopera-tion.Thestressanalysisshallincludestressesduringpipelineinstallationandstressesinducedbyoperationalandenviron-mentalconditions.Thesestressesmayreachtheirpeakvaluesatdifferenttimes.Themaximumaxialdesignstressisthemax-7Wang,Y.-Y.andLiu,M.,“AComprehensiveUpdateintheEvalua-tionofPipelineWeldDefects,”U.S.DOTAgreementNo.DTRS56-03-T-0008,PRCIContractNo.PR-276-04503,DraftreporttoDOTandPRCI,November2004.48APISTANDARD1104imumtotalaxialstressatanygiventimeduringthedesignlifeofthepipeline8.A.2.2C