Failure Analysis of Ethylene Cracking Tube

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1、JFail.Anal.andPreven.(2009)9:316–322DOI10.1007/s11668-009-9259-5CASEHISTORYPEER-REVIEWEDFailureAnalysisofEthyleneCrackingTubeV.TariÆA.NajafizadehÆM.H.AghaeiÆM.A.MazloumiSubmitted:23December2008/inrevisedform:28April2009/Publishedonline:12May2009ÓASMInter

2、national2009AbstractRadianttubesofanethanefurnaceatapetro-temperature(approximately1100°C).Normalservicelifechemicalplantfabricatedfromanausteniticheatresistantofthesecoiledtubesisapproximately100,000h,butdoessteelcasting(HPgrade)failedalonglongitudinal

3、directiondependsontheserviceconditionandcouldvaryfromafterafractionofanticipatedservicelife.Tostudythe30,000to180,000h[1].causeoffailure,microstructuresofas-receivedandusedEthylenecrackingreactionproducesfreecarbonthattubeswereinvestigatedbyopticalandsc

4、anningelectrondepositsontubesurfaceasadherentcoke.Thisacceleratesmicroscopyandthemicrochemicalcompositionoftubescarbondiffusionintubematerial,especiallyduringtheandprecipitatedcarbideweredeterminedbyenergydis-decokingperiod[2].Carburizedmaterialintheinn

5、erwallpersiveX-ray(EDS).Also,themorphologyofdepositedoftheradianttubehasahigherthermalexpansioncoeffi-cokeparticleswasdeterminedbySEM/EDS.Finallytocientandtendstoincreaseinvolumeandplacestressesonmeasuretheextentofcarbonpenetration,hardnesstestingthetube

6、.Thesethermalstressesmakethetubemoresus-wasperformedontheinnerandoutersurfaceoftube.Theceptibletocreepfailure[3].experimentalresultsshowthattheimpropercokingandThedepositionofthecokeathightemperatureisgen-decokingcyclesremovetheprotectiveoxidelayer(Cr2O

7、3)erallyinhibitedbythepresenceofaCr2O3layeronthethatformsontheexposedsurfacesandthat,withthislayerinnersurfaceofthetube.Whenthisfilminpresentcarbonremoved,thecokecouldeasilydepositoninner,non-pro-diffusionintothetubeisretarded.However,duringdeco-tectedsu

8、rface.Thecarbondiffusionintothemetalwasking,thetubemaybesubjectedtoseverethermalshockacceleratedwithdepositedcokeandcausedmicrostructuralthatresultsinremovaloftheCr2O3layer,sothecarburi-degradationanddrasticallyreducedtheductilit