ASME B16.5 - 2003.pdf
Pipe Flanges and
Flanged Fittings
NPS
1/2 Through NPS 24 Metric/Inch
Standard
FOREWORD
In1920,theAmericanEngineeringStandardsCommittee[latertheAmericanStandardsAssocia-
tions(ASA)]organizedSectionalCommitteeB16tounifyandfurtherdevelopstandardsforpipe
flangesandfittings(andlaterforvalvesandgaskets).Co-sponsorsoftheB16Committeewere
theAmericanSocietyofMechanicalEngineers(ASME),theHeatingandPipingContractors
NationalAssociation[nowMechanicalContractorsAssociationofAmerica(MCAA)],andthe
ManufacturersStandardizationSocietyoftheValvesandFittingsIndustry(MSS).Co-sponsors
werelaterdesignatedasco-secretariatorganizations.
TheCommitteesoonrecognizedtheneedforstandardizationofsteelpipeflanges.InMay,
1923,Subcommittee3wasorganizedtodevelopsuchstandardsforpressuresinthe250psito
3200psirangeandforelevatedtemperatures.ActiveworkbeganinOctober,includingsteel
flangedfittings.ThefirstproposedstandardwassubmittedtotheCommitteeinApril1926and
approvedbyletterballotinDecember.Afterfavorablereviewbythethreesponsororganizations,
theStandardwasapprovedasAmericanTentativeStandardB16einJune1927.
ExperienceinusingtheStandardshowedtheneedforhubdimensionsofcompanionflanges
andforotherchanges,includingreratingof250lband1350lbflangesanddevelopmentof
flangedfittingswithintegralbases.Aninvestigationwasmadeintothefactorsdetermining
stiffnessofflangesandflangehubs.TherevisededitionwasapprovedasASAB16E-1932.
Arevisionwasinitiatedin1936,stimulatedbysuggestionsfromCommitteemembersand
industrialusers.Theresulting1939editioncontainedstandardsforweldingneckflanges(com-
pletedinMarch1937),1500lbflangesinthe14in.through24in.range2500lbflangesand
flangedfittingsinthe 1
⁄
2 in.through12-in.range,anddimensionsforafulllineofringjoint
flangesdevelopedbytheAmericanPetroleumInstitute.Pressure-temperatureratingsforalloy
steelflangesandfittings,developedbySubcommittee4,wereincludedforthefirsttime.
InAugust1942,theWarProductionBoardrequestedareviewofmeasurestoconservevital
materialsinpipingcomponents.AspecialWarCommitteeofB16wasappointedand,operating
underWarStandardProcedure,developedrevisedpressure-temperatureratingsforallmaterials
andallpressureclasses.TheratingswerepublishedasAmericanWarStandardB16e5-1943.In
1945,undernormalprocedures,Subcommittees3and4reviewedthe1939standardandthe
1943ratings,andrecommendedadoptionofthewartimeratings.Theirreportwasapprovedas
SupplementNo.1toB16e-1939andpublishedasASAB16e6-1949.Inadditiontoratings,the
supplementupdatedmaterialspecificationreferencesandaddedatableofmetalwallthickness
forwelding-endvalves.
Subcommittee3thenbeganarevisionoftheentirestandard.Technically,the1949Supplement
wasabsorbed,newmaterialswererecognized,ageneralratingmethodwasdevelopedand
addedasanappendix,andweldingendpreparationswereexpanded.Editorially,anewstyleof
presentationwasworkedout,includingtablesrearrangedforeasieruse.ApprovalbySectional
Committee,cosponsors,andASAresultedinpublicationofASAB16.5-1953(designationchanged
fromB16e).
Worksoonbeganonfurtherrevisions.ClassBratingsweredeletedandClassAratingswere
clarifiedasthestandard.Anappendixdefinedqualificationsforgaskets,otherthanringjoint,
whichwouldmerittheratings.Anotherappendixdefinedthemethodforcalculatingboltlengths
(includingmeasurementofthelengthofstudboltsbetweenthreadendsinsteadofbetween
points).Pressure-temperatureratingsforseveralnewmaterialswereadded,thetableofwelding
enddimensionswasexpanded,andthetemperaturesusedindeterminingratingswereredefined.
Theresultingnewedition,afterapproval,waspublishedasASAB16.5-1957.
ThemoremodestrevisionapprovedasASAB16.5-1961changedthetexttoclarifytheintent
ortomakerequirementseasiertoadminister.Thenextrevisionbeganin1963withnearly100
commentsandsuggestions.Nofundamentalchangesweremade,butthetextwasfurtherclarified
andwallthicknesseslessthen 1
⁄
4 in.forflangedfittingswererecognizedinthe1968edition.