文献翻译-在化工设备设计中对防腐蚀的考虑

文献翻译InchemicalplantdesignconsiderationsofcorrosionAbstract:Thiswilldiscussanti-corrosionstructure,parametersandmeasuresandsecurity-relatedissuesofsometypical,whichareinvolvedinthedesignofchemicalequipment.Keywords:thedesignofchemicalequipmentcorrosionresistantsafety.Inthedesignofchemicalequipment,itneedstoconsidercorrosionandassociatedmediaflow,storageproductandthecorrespondingmaterialselectionan-dheatprocessingrequirements.Inthenormaldesignprocess,thesefactorsshouldbetakenfullaccountbydesignersintheareofdeviceandrelatedprofessional,andthecorrespondingtechnicalrequirementsofthedesignshouldbeworkout.However,inrecentyears,intheenvironmentofthedesignofneweconomicmarket,manynon-chemicalengineeringdesign,andmanufacturingcorporationsareinvolvedinthedesignofchemicalequipment.Becauseofvariousobjectiveconditions,inthesenewcorporationsenteredinthedesignofchemicalequipment,thereexistssuperficialstudyandsoill-consideredproblemsinthechemicalcorrosion,thisleadstosafetyproblemsandaccidents.ThisworkwilllistanddiscusessometypicalproblemswhichIencounteredInrecentyears.Bydoingthistoraisetheattentionofpeoplerelated.1Anti-corrosionstructure.(1)InthestructureofaU-tubeheatexchanger,whichisdesignedbyacorporation,thetubeplateandshellareweldedasawholeone(thisheatexchangerstructureitselfIsunreasonable).Thedesignerthinksthatthebundleinsertedintotheshellnolongerneedtopullout,soonlytwoSkateboard-orientedaredesignedinthebottomofthetubebundle,withoutdesigningslideorstand.Skateboard-orienteddirectcontactswiththehousingwall,formingagapbetweentheU-tubebundleandthetwoSkateboard-orientedandtheshell,thisgappronetocrevicecorrosion.Crevicecorrosionwillcausepartoftheshellofheatexchangethinneratuniformrate,forthisdevice,sincethetubescannotberemovedperiodicallytochecktheinternalshell,onceformedtwoverticallocalthinnedareasalongtheSkateboard-orientedwouldendangerthesafeoperationofthisheatexchanger.Toavoidcrevicecorrosion,thegapshouldbeasmuchaspossibletoeliminateinthedesignofchemicalequipment.(2)Averticalcookingpotdesignedbyacorporation,itsimportandexportofaresetedonthecontainerwall,mediumflowsfromlowtohighlevel,anditsmediumiscornpaste.Designpressureis0.605MPa,thedesigntemperatureis200,theshellmaterialisQ235-C,andnominalthicknessis10mm.Astheofficersrelatedunknowntheconcreteuseandlackofdesignexperience,theymaydesignflushstructurebetweenthematerialinletandtheinternalshell,ignoringtheentireprocessflowsystemisaprocessofdecreasingpressure,andthefactorthatthecornpastemayentraingas.Thisresultsthattheupperpartofthecookingpotcylinderwallmaterialinlettubesuddenlytornmorethan1meterlongverticalcracks,boilinggritsejected,resultingin1deathandthreeinjuriesseriousaccidentsinthecontainerduringuse.Aftertheaccident,accidentinvestigationresultsshowthatthecookingpotmaterialinlettubetothetopofthecylinderwallhasbeenthinned0.40.9mm.Wallthinningofthedetailedmechanismneedsfurtherstudy,butanindisputablefactisthatanotherfactoryalsousethestructurewithaplug-intointhematerialinlettubeinthesameconditionasimportedmaterials,thereexcitesnoinspectioncertificatetoprovethephenomenonthatpartofvesselwallbecomesthinner.Thelessonofthisincidentrevealsthat,forpressurevesselusingliquidorgas(steam)asthemediaentranceofthemedium,avarietyofplug-instructurecanbeused,sothateffectivelyavoidlocalthinningofpressurevesselscausedbycavitations,flashing,erosion,wear,abrasionandotherreasons.Ortherearesecurityrisks.2Corrosionparameters2.1CorrosionallowanceCorrosionallowanceofchemicalequipmentisbasedonthedesignlifeofthecontainerandthemediumonthecorrosionrateofmetals.Thisisabasicconcept,butIcomeintocontactwiththesituationthatdifficulttojudgewhetherthecorrosionallowanceiscorrectornotinsomechemicalequipmentdrawings,leadingtohiddendangerdisturbsthesafeoperationofequipment.Forexample,insomechemicalequipmentdesigndrawingsanddesignconditions,itsmediaisexpressedwithsomecustomcode,thestartingpointmaybetotheprotectionofitsproprietarytechnology,anddesignersalsoignoretolearnthecorrosive,flammabletoxicityofthemedia.Insuchcircumstances,wesuggestthatcorrosion,flammable,toxicandotherpropertiesofchemicalmediumshouldbespeciallyfiguredoutinthetechnicalrequirementstoensurethesafeoperationofchemicalequipment.Theotherproblemofcorrosionallowanceisthatsomearecommissionednottotaketheappropriatecorrosionallowancebasedonthedesignlifeofnormalcontainer,onthecontrary,theyintendtotakelessornocorrosionallowance.Usuallythestartingpointisthattheprojectsinvestorshopetorecovertheinvestmentcostoftheprojectinashorttime.Theequipmentwillbedisposedafterbeingputtedintooperationin2to3years,thisistheso-calledshort-termbehavioroftheinvestment.Thedesignlifeofchemicalequipmentexceptrequiredspecialrequirements,towers,reactorsandothermajorcontainersaregenerallynotlessthan15years,thegeneralcontainers,heatexchangersandotherarenotlessthan8years.Correspondtothenormaldesignlifeofthecontainer,Article115andArticle116ofPressureVesselSafetyTechnologyprosecutionproceduresrespectivelyprovidedequipmentsofregularinspectionofpressurevesselatserviceandinternalandexternalinspectioncycle.Therefore,inthiscase,ifthedesignercannotconvincethepartytodesignthecontaineraccordingtolifeofthenormaldesignofchemical,thentherealdesignlifeofthecontainshouldbestatedspecificallyinthedrawingstoremindtheuserandsupervisor,andthentoavoidaccidents.2.2Theso-calledreferencemap“andstandards,“theproblemCurrently,manydesignworksworkedoutbypressurevesseldesigningcorporationhasaclearimitationofthedesignmarks.Designimitationisaneffectivewayoflearning.However,afirmhasalreadyattainedhisdesignqualificationofpressurevesseldesigning,iftheystayinthelevelofimitationofthedesignphase,andshallnotthoroughlyunderstandthetechnicalcontentoftheoriginalreferencemap,thentheremaybeproblems.Forexample,someofthepressurevesseldesignfirmsandmanufacturingfirmshavenorequirementsorheattreatmentforammoniapressurevesselwhosemediumisliquid.Whenaskedthereason,manypeoplecitethereferencethatthefigurefromtherefrigerationindustrydoesnotrequireheattreatmentasanexample.Differentindustryhasitsowncharacteristics.Generally,ithastheappropriatetechnicalstandard,JB/T6917-93refrigerationindustrystandardhascomprehensiverequirementsindesign,manufacture,inspectionandacceptanceinthepressurevesselwhosemediaisammoniainrefrigerationindustryasothersectorsofpressurevesseldesignandmanufacturingcorporationsshouldnotsimplycopyaparticulardesignrequirement.Todoso,therearesecurityrisks,andonceasecurityincidentappears,thedesignersshouldalsotakemaincontractorsresponsiblefordesigntechnology.Somepressurevesseldesigningcorporationsandmanufacturecopyaseriesofheatexchangeraccordingtoscandownwithoutmodification,andusethemasheatexchangerdesigndrawingsinvariousdesignconditions,useof.Inthiscase,ifthemediaistoocorrosiveoroperatingconditionschangetherearealsosecurityrisks.2.3MediumconcentrationChemicalmediaindifferentconcentrationsandtemperatureshavedifferentcorrosionproperties.ThisisparticularlyevidenttothemediaofNaOH,whichisquitecommon.Forcarbonsteelandlowalloysteelpressurevessel,iftheyarenottakenheattreatmenttoeliminatestressafterweldingorcodling,concentrationandtemperatureofNaOHhaveacertainlimit;itspurposeistopreventstresscorrosioncracking.However,inpressurevesseldesigndrawingsofferedbymanyfirms,inthetechnicalcharacteristicsofthetable,themediacolumn,justfillinthelyecharacter,theconcentrationofNaOHisneithermarkednorproposedheattreatmentrequirements.3CorrosionProtectionMeasuresInthetechnicalrequirementsintheGeneralPlanofliquefiedpetroleumgasstoragetanksandliquidammoniatankdrawingsofferedbysomefirms,thereisnoproposedheattreatmentrequirementafterwelding.Askedthereason,designersareeithernotclearabouttheneedforpost-weldheattreatmentortoavoidstresscorrosioncracking,orconsideritshouldbedonebythemanufacturingdepartments.Designdocumentsarethebasisofcreation,test,acceptance.Ifthedesignersofpressurevesseldonotknowitsmediapropertiesandproposecorrespondingtechnicalrequirements,thenisdifficultforthemanufacturingdepartmentstotaketheappropriatetechnicalmeasures.Themasterplanofpressurevesselhasfunctionofguidingmanufacturing,inspectionandacceptance,butalsoitisoftenthebasisofsigningmanufacturingandinstallationcontract.Thereforeitisproposedthatsecurityinvolvingpressurevesselsandsomeofitscostsdirectlyrelatedtomanufacturing,testing,heattreatmentandotheritemsofthecontentsofthetechnicalrequirementsintheGeneralPlanindicatedotherwise,motivatedbyprofit,andsomemanufacturingunits(sectors)mayintentionallyorLittledoordonotinadvertentlysomeoftheprojectsshouldbedone,resultinginsecurityrisks.SomeunitsNaOHtankdesign,selectionofanordinaryglasstubeliquidlevelmeter(board)typeliquidlevelmeter.ShouldbeselectedwithinPTFElinedglassliquidlevelgauge,orNaOHliquidwillerodeglass.Inshort,inthecurrentmarketenvironment,thechemicalindustryinthedesignofpressurevessels,somenewproblemsemerged,leadershipandrelevanttotheneedsofdesignersontheattentionandberesolved.StrengthcalculationprocessequipmentpackagesSW6-1998(v1.25)throughtheassessmentChemicalequipmentdesignbytheNationalOrganizationDevelopmentTechnologyCenterstationtoGB150,GB12337,JB4710,andHG20582SteelChemicalstrengthcalculationrules“forthemathematicalmodelofthestrengthcalculationprocessequipmentpackagesSW6-1998(v1.25),pressurevesselsbytheNationalStandardizationTechnicalCommitteeTechnicalCommitteeComputerTechnologyReviewexperts.ThroughtheprescribedprocedurescertifiedbytheNationalPressureVesselTechnologyStandardizationTechnicalCommitteereviewedandapprovedbytheStateQualityandTechnicalSupervisionBureauofBoilerandPressureVesselSafetyrecognitionCardrecord.AccreditationcertificatenumberD0011999.Theaccreditationcertificatesthenext5plasticremakeofphotoswillSW6-1998softwareisalsoavailabletotheuser.SW6-1998unitsofexistinguserswillsoonreceivetheNationalChemicalEquipmentDesignTechnologyCenterstationaccreditationcertificateplaced5plasticremakeofthepicture.Noticeisherebygiven.PressureVesselCertificateofComputerSoftwareTechnicalReviewNationalChemicalEquipmentDesignTechnologyCenter在化工设备设计中对防腐蚀的考虑摘要本文将化工设备设计中涉及防腐蚀结构、参数及措施并与安全有关的一些典型问题列出进行讨论。关键词化工设备设计防腐蚀安全。化工设备设计中需要考虑介质的腐蚀性及与之相关的流动、存积以及相应的选材、热处理等要求。在正常的设计过程中,这些因素由设备专业及相关专业的设计人员全面考虑并提出相应的设计技术要求。但是,在近几年新的市场经济设计大环境下,许多非化工专业设计、制造单位参与到化工设备的设计工作中。受各种客观条件限制,这些新加入的设计单位在化工设备的设计工作中存在着深度不够和在化工防腐等方面考虑不周等问题,造成了安全隐患和事故。本文将作者在近几年工作中碰到的一些典型问题列出,并进行讨论,以期引起有关同志对这一问题的重视。1防腐结构(1)某单位设计的一台U型管换热器,将管板与壳体焊为一体(这种换热器结构本身就是不合理的),设计者认为管束装入壳体后不再需要拉出来,所以在管束的下方只设计了两条导向滑板,没有设计滑道或支架。导向滑板与壳体内壁直接接触,在U型管束和两条导向滑板与壳体之间形成缝隙，容易产生缝隙腐蚀。缝隙腐蚀会使换热器壳体局部均匀减薄,对于这台设备而言，由于不能定期拆下管束进行壳体内部检查,一旦沿着导向滑板形成两条纵向局部减薄区,将危及这台换热器的安全运行。化工设备结构设计中应尽可能地消除缝隙,避免缝隙腐蚀。(2)某单位设计的立式蒸煮锅,进口和出口开在容器的侧壁,下进上出,介质为玉米糊。设计压力0.605MPa,设计温度200,壳体材料为Q235-C,名义厚度10mm。由于有关人员对使用情况不明及设计经验不足,而将物料进口管与容器内壁之间设计成平齐结构,忽视了整个工艺流系统是一个压力逐渐降低的过程,并且玉米糊中还可能夹带气体这一因素,结果在容器使用过程中,蒸煮锅物料进口管上部筒壁突然撕开1米多长的纵向裂纹,沸腾的玉米糊喷出,造成1人死亡,三人受伤的严重事故。事故发生后,事故调查结果表明,该蒸煮锅物料进口管上部筒体壁厚已经减薄至0.40.9mm。壁厚减薄的详细机理有待进一步研究,但一个不争的事实是另一家工厂同样工况的同样设备物料进口管采用了插入式接管结构,经测厚检查证明没有容器筒体壁局部减薄的现象发生。这个事故给我们的教训与启发是,对于以液体或气(汽)体为介质的压力容器介质入口采用各种插入式结构可以有效地避免由于汽蚀、闪蒸、冲刷、磨损、磨蚀等原因造成的压力容器壁厚局部减薄,否则存在着安全隐患。2防腐参数2.1腐蚀裕量化工设备的腐蚀裕量应根据容器的设计寿命和介质对金属材料的腐蚀速率确定。这是一个基本概念,但在笔者接触到的一些化工设备图纸中有时难以判断所标出的腐蚀裕量是否正确,给设备的安全运行留下隐患。例如一些化工设备图纸及其设计条件单中,将其介质用一些自定义的代号表达,其出发点可能是为了其专有技术的保护,而设计者也忽视了了解介质的腐蚀性、易燃性、毒性。建议,在这种情况下应将化工介质的腐蚀性、易燃性、毒性等特性在“技术要求”后面专门注明,以保证化工设备的安全运行。腐蚀裕量的另一方面问题是,有的甲方委托设计时不按正常的容器设计寿命取相应的腐蚀裕量,有意少取或不取腐蚀裕量。其出发点往往是项目的投资者想在短时间内收回整个项目的投资成本,设备投产运行23年后就打算把设备处置掉,即项目投资中的短期行为。化工设备的设计寿命除有特殊要求外,塔、反应器等主要容器一般不应小于15年,一般容器,换热器等不少于8年。与容器的正常设计寿命相对应,压力容器安全技术检察规程中的第115条和第116条中分别规定了在役压力容器定期检验要求和缩短内外部检验周期的要求。因此,在这种情况下,设计者如果不能说服甲方按正常的化工寿命进行设计的话,那么就应当实事求是地在图纸中专门注明该容器的设计寿命,经提醒其使用者和监督者,避免发生安全事故。2.2所谓“参考图”和“标准图”问题目前,许多压力容器设计单位的设计作品中带有明显的仿设计痕迹。模仿设计是一种有效的学习途径。但是,一个已经取得了压力容器设计资格的单位,他的设计水平如果总是停留在模仿设计阶段上,不吃透原参考图的技术内容,那么就有可能要出问题。例如,有的压力容器