Intro Predictive Maintenance 2E英文原版机械工程与材料科学教材教程

Intro Predictive Maintenance 2E英文原版机械工程与材料科学教材教程 (1)all monfailure modeshave distinctvibration frequencyponents thatcanbeisolated andidentified,and (2)the amplitudeof eachdistinct vibrationponentwill remainconstant unlessthe operatingdynamics ofthe machine-train change.These facts,their impacton machinery,and methodsthat willidentifyand quantifythe rootcause offailure modesare developed in moredetail inlater chapters.ImpactofMaintenance5Predictive maintenanceusing processefficiency,heat loss,or othernondestructivetechniques canquantifythe operating efficiencyof nonmechanicalplantequipmentorsystems.These techniquesused inconjunction withvibration analysiscan providemaintenancemanagers and plant engineerswith informationthat willenable themtoachieve optimumreliability andavailability fromtheir plants.Five nondestructivetechniques arenormally usedfor predictivemaintenancemanagement:vibration monitoring,process parametermonitoring,thermography,tribology,and visual inspection.Each techniquehas aunique dataset thatassists themaintenancemanager indetermining theactualneedfor maintenance.How doyou determinewhich techniqueor techniquesare requiredin yourplant?Howdo youdetermine thebest methodto implementeach ofthe technologies?How doyouseparate thegood fromthe bad?Most prehensivepredictivemaintenancepro-grams usevibration analysisas theprimary tool.Because mostnormal plantequip-mentismechanical,vibration monitoringprovides thebest toolfor routinemonitoringand identificationof incipientproblems;however,vibration analysisdoes notprovidethe datarequired onelectrical equipment,areas ofheat loss,conditionoflubricatingoil,or otherparameters thatshould beincluded inyour program.1.1.4Other MaintenanceImprovement MethodsOverthe past10years,a varietyofmanagementmethods,such astotal productivemaintenance(TPM)and reliability-centered maintenance(RCM),have beendevel-oped andtouted as the panaceafor ineffectivemaintenance.Many domesticplantshave partiallyadopted oneof thesequick-fix methodsin anattempt topensate forperceivedmaintenance shortings.Total ProductiveMaintenanceTouted asthe Japaneseapproach toeffectivemaintenancemanagement,the TPMconceptwas developedby Deminginthelate1950s.His concepts,as adaptedby theJapanese,stress absoluteadherence tothe basics,such aslubrication,visualinspec-tions,and universaluseofbest practicesin allaspects ofmaintenance.TPM isnot amaintenancemanagementprogram.Most ofthe activitiesassociatedwith the Japanese managementapproach aredirected at the productionfunction andassumethat maintenancewillprovidethe basictasks requiredto maintaincritical pro-duction assets.All ofthe quantifiablebenefits of TPM arecouched interms ofcapac-ity,productquality,and totalproduction cost.Unfortunately,domestic advocatesofTPM havetried toimplement itsconcepts asmaintenance-only activities.As aresult,few of these attemptshave beensuessful.At thecore ofTPM isa newpartnership amongthe manufacturingor productionpeople,maintenance,engineering,and technicalservices toimprove whatis calledoverallequipment effectiveness(OEE).It isa programof zerobreakdowns andzero6An Introductionto PredictiveMaintenancedefects aimedat improvingor eliminatingthe followingsix cripplingshop-floorlosses:?Equipment breakdowns?Setup andadjustment slowdowns?Idling andshort-term stoppages?Reduced capacity?Quality-related losses?Startup/restart lossesAconcisedefinition ofTPM iselusive,but improvingequipment effectivenessesclose.The partnershipidea iswhat makesit work.In theJapanese modelfor TPMarefive pillarsthat helpdefine howpeople worktogether inthis partnership.Five PillarsofTPM.Total productivemaintenance stressesthe basicsofgoodbusi-ness practicesas theyrelate tothemaintenancefunction.The fivefundamentals ofthisapproach includethe following:1.Improving equipment effectiveness.In otherwords,looking for the sixbig losses,finding outwhat causesyour equipmentto beineffective,andmaking improvements.2.Involving operatorsin dailymaintenance.This doesnot necessarilymeanactually performingmaintenance.In manysuessful TPMprograms,oper-ators donot haveto activelyperform maintenance.They areinvolved inthemaintenance activityintheplan,intheprogram,and inthe partner-shipbut not necessarily inthe physicalactofmaintaining equipment.3.Improving maintenanceefficiency andeffectiveness.In mostTPM plans,though,the operatoris directlyinvolved insome levelofmaintenance.Thiseffort involvesbetter planningand schedulingbetter preventivemainte-nance,predictivemaintenance,reliability-centered maintenance,spareparts equipmentstores,and toollocationsthe collectivedomain ofthemaintenance departmentand themaintenance technologies.4.Educating andtraining personnel.This taskis perhapsthemostimportantin theTPM approach.It involveseveryone inthe pany:Operators aretaughthow to operate theirmachines properlyand maintenancepersonnelto maintainthem properly.Because operatorswill beperforming someofthe inspections,routine machineadjustments,andotherpreventivetasks,training involvesteaching operatorshow todo thoseinspections andhowto workwith maintenanceinapartnership.Also involvedis trainingsuper-visors onhow tosupervise ina TPM-type teamenvironment.5.Designing andmanaging equipmentfor maintenanceprevention.Equip-mentiscostly andshould beviewed asa productiveasset forits entirelife.Designing equipmentthat iseasier tooperate andmaintain thanpreviousdesigns isa fundamentalpartofTPM.Suggestions fromoperators andmaintenancetechnicians helpengineers design,specify,and procuremoreeffective equipment.By evaluatingthecostsof operatingand maintainingImpactofMaintenance7the newequipment throughoutits lifecycle,long-term costswill bemini-mized.Low purchaseprices donotnecessarilymean lowlife-cycle costs.Overall equipmenteffectiveness(OEE)isthebenchmark usedfor TPMprograms.TheOEE benchmarkis establishedby measuringequipment performance.Measuringequipment effectivenessmust gobeyond justthe availabilityor machineuptime.Itmust factorin allissues relatedto equipmentperformance.The formulafor equip-menteffectivenessmust lookattheavailability,the rateof performance,and thequalityrate.This allowsall departmentstobeinvolved indetermining equipmenteffectiveness.The formulacould beexpressed as:Availability?Performance Rate?Quality Rate=OEEThe availability istherequired availabilityminus thedowntime,divided bytherequired availability.Expressed asa formula,this wouldbe:The requiredavailabilityisthe timeproduction istooperatethe equipment,minus themiscellaneousplanned downtime,such asbreaks,scheduled lapses,meetings,and thelike.The downtimeistheactual timethe equipmentis downfor repairsor changeover.This isalso sometimescalled breakdowndowntime.The calculationgives thetrueavailability oftheequipment.This numbershould beused inthe effectivenessformula.The goalfor most Japanese panies is greaterthan90percent.The performancerate isthe idealor designcycle timeto producethe productmulti-plied bythe outputand divided bytheoperating time.This willgive aperformancerate percentage.The formulais:The designcycle timeorproductionoutput isinaunit of production,such aspartsper hour.The outputisthetotal outputforthegiven timeperiod.The operatingtimeis theavailability valuefromtheprevious formula.The resultisapercentage ofper-formance.This formulais usefulfor spottingcapacity reductionbreakdowns.The goalformostJapanesepanies isgreaterthan95percent.The qualityrate isthe productioninput into the process or equipmentminus thevolume ornumber ofquality defectsdividedbythe productioninput.The formulais:Production InputQualityDefectsProduction InputQualityRate-?=100Design CycleTime OutputOperatingTimePerformance Rate?=100Required AvailabilityDowntimeRequiredAvailabilityAvailability-?=1008An Introductionto PredictiveMaintenanceThe productioninput isthe unitof productbeing fedintotheprocess orproductioncycle.The qualitydefects arethe amountofproductthat isbelow qualitystandards(not rejected;there isa difference)after theprocessorproduction cycleis finished.The formulais usefulin spottingproduction-quality problems,even whenthe cus-tomer aeptsthe poor-qualityproduct.The goalfor Japanesepaniesishigherthan99percent.Combining thetotal fortheJapanesegoals,it isseen that:90%?95%?99%=85%To beabletopete forthe nationalTPM prizein Japan,equipment effectivenessmustbe greaterthan85percent.Unfortunately,equipmenteffectivenessin mostU.S.panies barelybreaks50percentlittle wonderthat thereis somuch roomforimprovement intypical equipmentmaintenancemanagementprograms.Reliability-Centered MaintenanceAbasic premiseof RCMisthatall machinesmust failand havea finiteuseful life,but neitheroftheseassumptions isvalid.If machineryandplantsystems areproperlydesigned,installed,operated,and maintained,they willnot fail,and theiruseful lifeisalmost infinite.Few,if any,catastrophic failuresare random,and someoutside influ-ence,such asoperator errororimproperrepair,causes allfailures.With theexceptionof instantaneousfailures caused by grossoperator errororatotally abnormaloutsideinfluence,theoperatingdynamics analysismethodology candetect,isolate,andprevent systemfailures.Because RCMis predicatedonthebelief thatall machineswill degradeand fail(P-F curve),most ofthe tasks,such asfailuremodesand effectsanalysis(FMEA)andWeibull distributionanalysis,are usedtoanticipatewhen thesefailures willour.Both ofthe theoreticalmethods arebased onprobability tablesthat assumeproperdesign,installation,operation,and maintenanceofplantmachinery.Neither isable toadjustfor abnormaldeviations inany ofthese categories.When theRCM approachwas firstdevelopedinthe1960s,most productionengineersbelieved thatmachinery hada finitelife andrequired periodicmajor rebuildingtomaintain aeptablelevels ofreliability.In hisbook Reliability-Centered Maintenance (1992),John Moubraystates:The traditionalapproach toscheduled maintenanceprograms wasbased ontheconcept thatevery itemonapiece ofplex equipmenthasarightage atwhich pleteoverhaul isnecessary toensure safetyand operat-ing reliability.Through theyears,however,it wasdiscovered thatmanytypes offailures couldnot beprevented oreffectively reducedby suchmaintenanceactivities,no matterhow intensivelythey wereperformed.Inresponse tothis problem,airplane designersbegan todevelop designfeatures that