Inthissection,thebehaviourduetoaxi-symmetricloads,i.e.tension,torque,internalandexternalpressureloadswillbeexplainedintermsofananalyticalapproachassumingthatthecylindricalstraightpipeshapeiskeptduringdeformation.Itisnotedthatwithrespecttoexternalpressurel...[继续阅读]

    1.PrimaryeffectsByconsideringallsteellayersandneglectingthecontributionfromtheplasticlayers,pureaxialequilibriumyields:whereNaisthenumberofcontributinglayers,Tpisthetruewalltension,njisthenumberofwiresinlayerj,σ11jistheaxialstressinthelayer,Ajisthewirecro...[继续阅读]

    Excessivetorsionmaygivelock-upofthewirescausingbird-cagingorexcessiveyielding.Thisisnotaverylikelyfailuremodeundernormaloperationalconditionswherethetorqueloadsaresmall.However,therehavebeencasesofexcessivetorsionduringpipeinstallation,whichhavecausedfail...[继续阅读]

    Burstingofapipebyexcessiveinternalpressurecanoccurifthepipeisnotproperlydesigned,orifthemaximuminternalpressureisconsiderablyunderestimated.However,iftheinternalpressureisknownthisfailuremodeisnotlikelytooccur.Thedesignpressureincludesoperatingpressureand...[继续阅读]

    Thebendingbehaviourofflexiblepipesisamorecomplexphenomenontoanalysethantheaxi-symmetricloadcase.Theflexuralresponseshowsapronouncedhysteresisbehaviour.Thisisillustratedbythemoment/curvaturerelationinFigure4.16.Thehysteresisbehaviourofnon-bondedpipesmaybee...[继续阅读]

    Excessivebendingcanleadtolocalbucklingdestructionofthepipeastheinterlockingelementsorhelicalarmourelementsinterfereandtoucheachotheraswellasplasticlayeroverstraining.(API,2008b)definestheminimumbendradiusfromtheconceptsofminimumstorageradius,ρs,andthemini...[继续阅读]

    AccordingtoEq.4.10,thestaticreferencestresslevelinthetensilearmourisgivenbythemeanstaticeffectivetensionandassociatedinternalandexternalpressures.Thisgivesameanaxialstressandassociatedcontactpressurethatgovernsthefrictionmoment.Inaflexibleriserthetensiona...[继续阅读]

    Withrespecttobendingstressesinthepressurearmour,therearetwosignificantcontributionstoconsiderwithreferencetoFigure4.1:(1)Bendinginducedlongitudinalσ11stressesinthehoopdirection;(2)Stressesintroducedinthecross-sectionplane,primarilyσ22,σ23andσ33stresses.1....[继续阅读]

    Excessiveexternalpressuremayleadtocollapseofthepipe.Collapseusuallyinvolvesflatteningofthepipewhichimpedestheflowthroughit.However,thisisnotconsideredtobeacriticalfailuremodesincethedesigndepthisusuallywelldefined.Thisisalsoreflectedindesignrecommendation...[继续阅读]

    1.GeneralDuringinstallationandshut-downconditionswherethepipeboreisexposedtoexternaloverpressure,thetensilearmourwillbeincompression,eveniftheeffectivetensionispositive.Thismayleadtolocalradialandtransversebucklingofthetensilewires,leadingtooveralltorsion...[继续阅读]