Root Cause Failure Analysis失效原因分析技术教程英文原版材料科学教程教

RootRoot CauseCause FailureFailure AnalysisAnalysis失效原因分析技术教程英文原版材料科学教程教失效原因分析技术教程英文原版材料科学教程教 ROOT CAUSE FAILURE ANALYSISI ROOT CAUSEFAILURE ANALYSIS PLANTENGINEERING MAINTENANCSERIESVibration FundamentalsR Keith MobleyRoot Cause Failure AnalysisR Keith MobleyMaintenance FundamentalsR Keith MobleyROOT CAUSEFAILURE ANALYSISR Keith MobleyNewnes BostonOxford AucklandJohannesburg MelbourneNew DelhiNewnes is an imprintof Butterworth Heinemann Copyright01999by Butterworth Heinemann aA memberof theReed Elseviergroup Allrights reserved No part of thispublication may be reproduced stored in a retrievalsystem or transmittedin anyform orby anymeans electronic mechanical photocopying recording or otherwise with out theprior writtenpermission of the publisher Recognizing theimportance ofpreserving whathas beenwritten Butterworth Heinemann printsits bookson acid free paperwhenever possible Library ofCongress Cataloging in Publication DataMobley R Keith 1943 Root causefailure analysis by R Keith Mobley Includes index ISBN0 7506 7158 0 alk paper 1 Plant maintenance p cm Plant engineeringmaintenance series 2 System failures Engineering I Title 11 Series TS192 M6251999658 2 024 2198 32097CIP British Library Cataloguing in Publication DataA cataloguerecord forthis bookis availablefrom theBritishLibrary The publisheroffers specialdiscounts onbulk ordersof thisbook For information please contact Manager ofSpecial SalesButterworth Heinemann225Wildwood AvenueWoburn MA01801 2041Tel 781 904 2500Fax 781 904 2620For informationon allNewnes publicationsavailable contact ourWorld WideWeb homepage at newnespress IO9876543Printed in the UnitedStates ofAmerica CONTENTSPart IIntroduction toRoot CauseFailure AnalysisChapter1Introduction Chapter2General Analysis Techniques Chapter3Chapter4Safety Related Issues Chapter5Regulatory ComplianceIssuesChapter6Process PerformanceRoot CauseFailure Analysis Methodology Part I1Equipment DesignEvaluation Guide Chapter7Chapter8Chapter9Chapter10Chapter II Chapter12Chapter13Chapter14Chapter15Chapter16Chapter17Chapt er18Pumps Fans Blowers and FluidizersConveyors CompressorsMixers andAgitators DustCollectors ProcessRolls GearboxesReducersSteam TrapsInverters ControlValves Sealsand Packingi3613586773757707112173137153164171187193302 20vi ContentsPart IIIEquipment TroubleshootingGuideChapter19Chapter20Chapter21Chapter22Cha pter23Chapter24Chapter25Chapter26Chapter27Chapter28Chapter2 9Chapter30Chapter31Pumps Fans Blowers and FluidizersConveyors CompressorsMixers andAgitators DustCollectors ProcessRolls Gearboxesor ReducersSteam TrapsInverters ControlValves Sealsand PackingOthers Listof AbbreviationsGlossary ReferencesIndex23723924625125426426626927127627828028228528 8291305306PartIINTRODUCTION TOROOT CAUSEFAILURE ANALYSISINTRODUCTION Reliabilityengineering andpredictive maintenancehave two major objectives pre venting catastrophicfailures of critical plantproduction systemsand avoidingdevia tions fromaeptable performancelevels thatresult in personal injury environmental impact capacity loss or poorproduct quality Unfortunately these eventswill ourno matterhow effective the reliabilityprogram Therefore a viableprogram also must includea processfor fullyunderstanding and correcting the root causes that lead to eventshaving animpact on plant performance This bookprovides a logical approachto problemresolution The methodcan be used to aurately definedeviations fromaeptable performancelevels isolate the root causesof equipmentfailures and developcost effective correctiveactions thatpre vent recurrence This three part setis apractical step by step guidefor evaluatingmost recurringand seriousincidents that may ourin a chemical plant Part One Introduction toRoot CauseFailure Analysis presents analysistechniques used to investigateand resolvereliability related problems It provides the basicmethodology forconducting aroot causefailure analysis RCFA The proceduresdefined in this sectionshould befollowed for all investigations Part Twoprovides specificdesign installation and operatingparameters forparticu lar typesof plantequipment This information is mandatoryfor all equipment related problems and it is extremelyuseful for other eventsas well Since many of thechronic problems that ourin processplants aredirectly or indirectly influencedby theoperating dynamicsof machineryand systems this partprovides invaluableguidelines foreach typeof analysis Part Threeis atroubleshooting guidefor mostof the machine typesfound in achemi cal plant This partincludes quick reference tablesthat define the monfailure or34Root CauseFailure Analysisdeviation modes These tableslist themon symptomsof machineand process related problemsand identifythe probablecause s PURPOSE OF THE ANALYSISThe purposeof RCFA is to resolve problems that affectplant performance It should not be an attempttooperating performancedeviations economic perfor mance issues safety and regulatorypliance issues GENERAL ANALYSISTECHNIQUES A number ofgeneral techniques are usefulfor problemsolving While many mon or overlapping methodologies areassociated with these techniques there alsoare differences This chapterprovides a brief overviewof themore monmethods used to performan RCFA FAILURE MODEAND EFFECTSANALYSIS Afailure mode and effectsanalysis FMEA is adesign evaluation procedureused to identify potentialfailure modesand determine theeffectof eachon systemperfor mance This procedureformally documentsstandard practice generates ahistorical record and servesas abasis forfuture improvements The FMEAprocedure is a sequence of logicalsteps starting withthe analysisof lower level subsystemsor ponents Figure2 1illustrates atypical logic tree that results with a FMEA The analysis assumes a failure pointof viewand identifiespotential modesof fail ure alongwith theirfailure mechanism The effectof eachfailure modethen istraced upto the system level Each failuremode andresulting effectis assigneda criticality rating basedon the probabilityof ourrence its severity and itsdelecta bility For failuresscoring highon thecriticalityrating design changesto reduceit areremended Following thisprocedure providesa morereliable design Also suchcorrect useof theM EA processresults intwomajorimprovements 1 improved reliabilityby antici pating problemsand institutingcorrections priorto producingproduct and 2 improved validityof theanalyticalmethod which resultsfrom strictdocumentation of the rationalefor everystep in the decision making process 6General AnalysisTechniques7 q disciplinesFigure2 1Failure modeand effectsanalysis FMEA flow diagram I i AeptfailureeffedL Two majorlimitations restrictthe useof FMEA 1 logic treesused forthis typeof analysis are basedon probabilityof failureattheponent leveland 2 full applica tionisvery expensive Basing logictrees onthe probabilityof failureis a problem becauseavailable ponentprobability dataare specificto standardconditions andextrapolation techniquescannot be used tomodify thedata forparticular applications FAULT TREE ANALYSISFault tree analysisis a method of analyzing systemreliability andsafety It providesan objectivebasis foranalyzing systemdesign justifying systemchanges performing trade off studies analyzing monfailure modes and demonstratingpliance withsafety andenvironment requirements It isdifferent fromafailuremodeandeffect analysisin that it isrestricted toidentifying systemelements andevents that lead toone particularundesired event Figure2 2shows thesteps involvedinper forminga fault tree analysis Many reliabilitytechniquesareinductive andconcerned primarilywith ensuringthat hardwareaomplishes itsintended functions Fault tree analysisisadetailed deduc rive analysisthat usuallyrequires considerableinformation about the system It ensuresthat allcritical aspects of a system areidentified andcontrolled This methodrepresents graphicallythe Booleanlogic associated with a particular systemfailure 8Root CauseFailure Analysisrn Defiop eventEstablish boundariesm Understandsystem7Construct fault tree1I Analyze tree Take correctiveaction Figure2 2ljpical fault tree process called thetop event and basicfailures orcauses called primaryevents Top eventscan bebroad all enpassing systemfailures orspecific ponentfailures Fault tree analysisprovides optionsfor performingqualitative andquantitative reli ability analysis It helps the analystunderstand systemfailures deductivelyand pointsouttheaspectsof a systemthatareimportant withrespect to the failure of interest The analysisprovides insightinto systembehavior A fault tree modelgraphically andlogically presentsthe variousbinations ofpos sible eventsourring in a systemthatleadto thetop event The termevent denotesa dynamihange ofstate that ours in asystemelement which includeshardware software human and environmentalfactors A faultevent is an abnormalsystem state Anom1event isexpected toour The structure of afaulttreeis shown in Figure2 3 The undesiredevent appearsas thetop event and islinked tomore basicfault eventsby eventstatements andlogic gates General AnalysisTechniques9 L Pnmry FuseFailure Closed 7 i Pnmary WhgFadwe Shorhd t A Figure2 3Example ofafault tree logictree CAUSE AND EFFECT ANALYSISCause and effect analysisisagraphical approachto failure analysis This alsois referredto asjshbone analysis a namederived from the fish shaped patternused to plot therelationship betweenvarious factors that contributeto a specific event Typi cally fishbone analysisplots fourmajor classifications of potential causes i e human machine material and method but caninclude anybination ofcatego ries Figure24illustrates asimple analysis Like mostof the failure analysismethods this approachrelies onalogicalevaluation ofactions or changes thatleadtoaspecificevent such asmachine failure The onlydifference betweenthis approachandothermethods is the useof thefish shaped graphtoplotthe cause effect relationship between specificactions orchanges and the end resultor event This approachhas oneserious limitation The jshbonegraph providesno clearsequenceofevents that leads tofailure Instead it displaysall thepossible causesthat10Root CauseFailure AnalysisFigure2 4ljpicalfishbone diagramplots fourcategories ofcauses may have contributed to the event While thisis useful it doesnot isolatethe specificfactorsthat caused the event Other approachesprovide themeans toisolate specifihanges omissions or actionsthatcausedthe failure release aident or otherevent being investigated SEQUENCE OF EVENTS ANALYSISA numberof softwareprograms e g Microsoft s Visio can be usedtogenerate asequence ofevents diagram As part of theRCFA program select appropriatesoft ware touse develop astandard format see Figure2 5 and be sure toinclude each event thatis investigatedinthe diagram Using sucha diagramfrom thestart of an investigationhelpsthe investigator organizethe informationcollected identify missingor conflictinginformation improve hisor herunderstanding byshowing therelationshipbetweenevents and the incident and highlightpotentialcausesof the incident The sequence of events diagramshould be a dynamicdocument generatedsoon afteraproblem is reportedand continuallymodified untilthe eventis fullyresolved Figure2 6isanexample ofsuchadiagram Proper useof thisgraphical toolgreatly improvesthe effectiveness of the problem solving teamand theauracy of the evaluation To achievemaximum benefitfrom General AnalysisTechniques11EVENTS I Y I Root CauseFailure AnalysisMethodology19In mostcases thefailedmachine mustbe replacedimmediately tominimize itsimpact onproduction If thisisthecase evaluating thesystem surroundingtheinci dent maybe beneficial Operating PerformanceDeviations inoperating performancemay ourwithout thephysical failureofcriticalproduction equipmentor systems Chronic deviationsmay justifythe useofRCFAasameans ofresolving therecurring problem Generally chronic productquality andcapacity problemsrequire afull RCFA How ever care mustbe exercisedto ensurethat theseproblems arerecumng andhaveasignificant impactonplantperformance beforeusing thisproblem solving technique Product QualityDeviations infirst time through productquality areprime candidatesfor RCFA which can beusedto resolvemost quality related problems However theanalysisshould notbeusedfor allquality problems Nonrecumng deviationsor thosethat haveno significantimpactoncapacity orcosts arenot cost effective applications Capacity RestrictionsMany ofthe problemsor eventsthatouraffect aplant s abilityto consistentlymeet expectedproduction orcapacity rates These problemsmaybesuitable forRCFA but furtherevaluation isremended beforebeginning an analysis After theinitialinvestigation iftheeventcanbefullyqualified anda cost effective solutionnot found then afullanalysisshouldbeconsidered Note thatananalysisnormally isnotperformedon random nonrecumng eventsor equipmentfailures Economic PerformanceDeviations ineconomic performance such ashigh productionor maintenancecosts often warrantthe useofRCFA The decisiontree andspecific stepsrequiredtoresolve theseproblems varydepending onthe typeofproblemand itsforcingfunc tionsorcauses Safety Anyevent thathas apotential forcausing personalinjury shouldbe investigatedimmediately While eventsinthisclassification maynot warrantafullRCFA they mustbe resolved as quickly as possible Isolating therootcauseof injury causing aidentsor eventsgenerallyismore diffi cult thanfor equipmentfailures andrequiresadifferent problem solving approach The primaryreason forthis increaseddifficulty isthatthecause oftenis subjective 20Root CauseFailure AnalysisRegulatory ComplianceAny regulatorypliance eventcan haveapotentialimpactonthe safetyof work ers the environment as wellas thecontinued operationoftheplant Therefore any eventthatresultsinaviolation ofenvironmental permitsorotherregulatory pli ance guidelines eg Oupational Safetyand HealthAdministration Environmental ProtectionAgency and stateregulations shouldbeinvestigated andresolvedasquicklyaspossible Since allreleases andviolations mustbe reported and theyhaveapotential forcurtailed productionor finesor both this typeofproblemmust receivea highpriority DATA GATHERINGThe data gathering stepshould clarifythe reportedeventorproblem This phaseofthe evaluation includesinterviews withappropriate personnel collecting physicalevi dence and conductingother research suchasperformingasequence of events analy sis which isneeded toprovideaclear understandingoftheproblem Note thatthis sectionfocuses primarilyon equipmentdamageorfailure incidents Interviews Theinterview processistheprimary methodusedtoestablish actualboundary condi tionsofanincidentand isa keypartofany investigation It iscrucial fortheinvestiga tor tobeagood list