焊接轮廓用于疲劳改善Word格式.docx
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焊接轮廓用于疲劳改善Word格式.docx
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MethodsofFatigueBehaviorImprovement
by
WeldprofilingandNDEusedforCNOOCPanyu4-2/5-1Jackets
ByCharlieChinChanChong
ASQCCertifiedQualityEngineer,ASNTNDTLevelIIIJM1715,
MICorr,SenAWeldI,EuropeanWeldingInspector
NACESeniorCorrosionTechnologist.
ADiscussionontheMethodsofFatigueBehaviorImprovement
byweldprofilingforPanyu4-2/5-1Jackets
Synopsis:
ThispaperpresentsadiscussiononvariousmethodswhichContractormayusetoperformtheweldprofilingactivitiesonDesignerdesignatedfatiguesensitivejoints.
EvenintheabsenceofDesignerdesignation,theWeldingInspectorshouldensuretheweldprofilescomplywiththeAWSD1.1Table2.7requirementsLevelIIasaminimum,appliestopre-qualifiedTKYjointsforintermediateandheavysectionswherethecoderequiresdifferentlevelweldprofiling.
1.Introduction:
Forfatiguebehaviorimprovementbyweldprofiling,itisimportantthattheactivitiesarecarriedoutbythefabricatorincorrectmanners.Followingisawrite-upsummaryofAPI2AWSDandAWSD1.1requirementsandproposalsthatmayassistthefabricatorinachievingthisobjective.
2.Discussion.
2.1TheCodes.
AcceptableoffshorepracticesusuallycallforeitherAWSD1.1orAPI2AWSDrequirementsonweldprofiling.TheDesignershouldspecifytheapplicablecode.API2AWSDSection11.1.3dwastheapplicablesectioncalledbyDesigner.
2.1.1API2AWSDSection11.1.3d
ThesectionstatedthatwherecontrolledweldprofilinghasbeenconsideredtheweldsurfaceshouldmergessmoothlywiththeadjoiningbasemetalandapproximatestheconcaveprofileshowninFigure11.1.3eitherasweldorwithprofilegrinding.
Therequiredprofilecheckisbyaprofilediskwithdiameterequalorgreaterthanthebracethicknessandthenotchesrelativetothedesiredweldprofileareconsideredunacceptableifthereisa0.04
in.(1mm)gapbetweenthediskofthespecifiedradiusandtheweld,eitheratthetoeoftheweldorbetweenpasses.
TheweldtoesshouldalsobeMPItestedtocheckforsurfaceandnearsurfacedefect.
2.1.2AWSD1.12.36.6.6
TheapplicableProject’sweldingcodeisAWSD1.1.ForT-,Y-,andK-connections,twolevelsoffatigueperformanceareprovidedforinTable2.7.LevelIandLevelII.
Dependingonthelimitingbranchmemberthickness,fourtypesofweldprofilerequirementsarespecified,namely
1.StandardflatweldprofileinconformancewithFigure3.8
2.ProfilewithtoefilletinconformancewithFigure3.9
3.Concaveprofile,aswelded,conformancewithFigure3.10withdisktestper2.36.6.6
(1)
4.ConcavesmoothprofileconformancewithFigure3.10fullygroundper2.36.6.6
(2)
ThedesignershalldesignatewhenLevelIistoapply;
intheabsenceofsuchdesignation,andforapplicationswherefatigueisnotaconsideration,LevelIIshallbetheminimumacceptablestandard.AWSD1.1Section2.36.6.7
ItisthereforeimportanttonotethatevenintheabsenceofDesignerdesignation,theWeldingInspectorshouldensuretheweldprofilescomplywiththeTable2.7requirementsLevelIIasaminimum.
TherequiredConcavesmoothprofilesasshowninFigure3.10are
Oneshouldnotethefollowingclause
Itisimportanttonotethattheweldprofilesfor2.36.6.6
(2)shallbesmoothandfullyground.
FollowingistheAWSD1.1sectionC2NonMandatoryCommentaryonFatigueBehaviorImprovementbyweldprofiling.(C2.36.6.6FigureC2.20)
Thefiguregivesdescribe2typesofweldprofilegrindingrequirementsnamely;
1.Concaveprofile,aswelded,conformancewithFigure3.10withdisktestper2.36.6.6
(1)
2.ConcavesmoothprofileconformancewithFigure3.10fullygroundper2.36.6.6
(2)
TheAWSD1.1sectionC2.36.6.6,NonMandatoryCommentaryonFatigueBehaviorImprovementbyweldprofilingwasproposedtoensuremoreeffectiveinmaintainingClassX1fatigueperformanceoverawiderangeofthicknesses.Howeverthecommentaryalsorecognizesitshortfall,sayingthatevenbygrindingwiththepermissiblenotchdepthfurtherreducedto0.01in.(0.25mm);
ifitmerelyflatteningthetopsoftheindividualweldpasses,whileleavingsharpcanyonsinbetween,doeslittletoimprovethefatigueperformance,eventhoughitwouldmeettheletterofthedisktest.
Atighterrequirementwassuggested.ItwassuggestedbytheC2.36.6.6commentarythatitmaybemoreeffectivetogrindtheentireweldprofilesmoothforbothfatiguecategoryIandII.
(WholeoftherelevantsectionofcommentarywasattachedforfurtherreadingAppendixII).
2.2NDE
Forconformancewiththecodesrequirements,thecodescallforthedetectionofsurfacebreakingandnearsurfacebreakingsignificantdiscontinuities.AWSandAPIcodesbothcallforMPIdetectionofsurfacediscontinuities.Asthegrindingdirection
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