ASMEB12051991GAGINGFORDRYSEALPIPETHREADS

ADOPTIONIIADOpTIrnNcrrIcE110June1992forASMEB1.20.5-199122Janw1991ANSIB120.5-197831October1980SUPERSEDINGASMEB1.2Q.5-1991wasadoptedon10June1992,andisapprovedforusebytheFederalagencies.TheAmricanSocietyofPkchanicalEngineers(ASME)preparedthis‘documntwhichwasapprovedbytheAmericanNationalStandardsInstitute(ANSI)asanAmricanNationalStxmdard.%thASMEandANSIhavefurnishedclearancesrequired.byexistingregulations.CopiesofthisdocumntarestmkedbytheS-zationDocumentsOrderDesk,Building4D,700RobbinsAvenue,Philadelphia,PA19111-5094tforissvletoDoDactivitiesonly.Allotherrequestorsmstobtaindocantsfrom:ThekwricanSocietyofMechanicalEngineersUnitedEngineeringCenter345East47thStreetNewYork,Ny10017-2392orTheflmericanNationalStandardsInstitute11Wst42ndStreetNewYork,NY10036-8002CivilCaxdimtionktivitiesr-m-Ac0GsA-7FxENAsA-m,LN!MilitaryCoordinatingActivity:DLA-ISCOPYRIGHTAmericanSocietyofMechanicalEngineersLicensedbyInformationHandlingServicesCOPYRIGHTAmericanSocietyofMechanicalEngineersLicensedbyInformationHandlingServices(INCH)ASMEBI.20.5=1991(REVISIONOFANSIB1.20.5-1978)TheAmericanSocietyofMechanicalEngineers~~~~~~345East47thStreet,NewYork,N.Y.10017-COPYRIGHTAmericanSocietyofMechanicalEngineersLicensedbyInformationHandlingServicesCOPYRIGHTAmericanSocietyofMechanicalEngineersLicensedbyInformationHandlingServices(s)orperson(s)affiliatedwithindustryisnottobeinterpretedasgovernmentorindustryendorsementofthiscodeorstandard.ASMEacceptsresponsibilityforonlythoseinterpretationsissuedinaccordancewithgoverningASMEproceduresandpolicieswhichprecludetheissuanceofinterpretationsbyindividualvol-unteers.Nopartofthisdocumentmaybereproducedinanyform,inanelectronicretrievalsystemorotherwise,withoutthepriorwrittenpermissionofthepublisher.CopyrightO1991byTHEAMERICANSOCIETYOFMECHANICALENGINEERSAllRightsReservedPrintedinU.S.A.COPYRIGHTAmericanSocietyofMechanicalEngineersLicensedbyInformationHandlingServicesCOPYRIGHTAmericanSocietyofMechanicalEngineersLicensedbyInformationHandlingServices(ThisForewordisnotpartofASMEBI.20.5-1991.)aIn1973,theAmericanNationalStandardsCommitteeB2,whichhadformerlybeenre-sponsibleforpipethreadstandards,wasabsorbedbyANSIStandardsCommitteeB1andreorganizedassubcommittee20.AcompleterewriteoftheB2.2-1968StandardonDrysealPipeThreadswascompletedwiththepublicationofANSIB1.20.3-1976forproductthreadsandtheANSIB1.20.5-1978StandardforGaging.TheproductthreadsfandardANSIB1.20.3establishestwoclassesofdrysealpipethreads:Class1andClass2.Theclassesdifferonlyininspectionrequirements.WithClass1threads,inspecti.onofrootandcresttruncationisnotspecified.Class2threadsareidenticaltoClass1threadsexceptthatinspectionofrootandcresttruncationisrequired.Thisgagingstandardincludes6-stepcrestandrootcheckgages,which,withintheirlimitations,shouldbehelpfulinestablishingthedegreeofconformanceofproductthreads.When6-stepcrestorrootcheckgagesaretobeused,itisnecessarytoclassifytheproductthreadsizeintoasizerange(minimum,basic,ormaximum)asshowninFig.1.Theuseof3-stepL1threadgagesforNPTFthreadsrequiresestimatingtheonethirdofaturn,plusorminus,fromthebasicnotchonthegagetoclassifythethreadasbasic.Useofthissameonethirdturnestimationisrequiredtodetermineminimumandmaximumranges.ThisStandardincludes4-steptaperthreadgagestoeliminatetheneedforestimatingtheonethirdturnde-viationfrombasicnecessarywith3-steporbasicstepgages.3-steptaperthreadgagesareincludedinAppendixAforthosewhomayprefertousethem.CrestandrootcheckgagesforNPTFthreadsarealsocoveredinthisStandard.