Predictive maintenance – the strategy that predicts when ... · PDF filePredictive...
Transcript of Predictive maintenance – the strategy that predicts when ... · PDF filePredictive...
Predictive maintenance – thestrategythatpredictswhenmachinerywillrequiremaintenance
Edition04/2016
2
“Damage can always be prevented if appropriate steps are taken in due time.” There’s no better way of describing the main benefit of predictive maintenance.The principle is based on three pillars:1. Permanently monitoring the condition of a “healthy”
system to detect wear or variations from the normal condition early on – fluid condition monitoring
2. If a variation is detected, in the simplest case only an alert is issued, but a better option is to determine and output the remaining service life of a component or a subsystem – as per Industry 4.0
3. On the basis of this “condition” of the system, costly downtime can now be reliably avoided and inexpensive maintenance can be scheduled.
This type of “condition-based” strategy creates the conditions for enabling negative changes in hydraulic and lubrication systems to be detected early on and countermeasures to be initiated in due time. Virtually every fluid system comes with a multitude of ways to consistently monitor the condition of the fluid and save on unnecessary costs.
Inhydraulicandlubricationsystems,friction,wear,leaksandexcess temperatures can contribute to the operating fluidbecoming contaminated,with solid particle contaminationorwater, forexample.Thiscontaminationthengoesontocauseerrorsincomponentsandsubsystemsandultimatelyinthesystemasawhole.Furthermore,thenormalageingprocessof thefluidcausesperformance losses thatoftenresult insystemdowntime. Inorder toprevent thesetime-consumingandcostlyconsequences,monitoringtheconditionoftheoperatingfluidisofmajorsignificance.Theconditionoftheoperatingfluidiscomparabletoa“fingerprint”oftheoverall condition of the system.Systems for permanentlymonitoring fluids (online fluid conditionmonitoring) in this
contextbecomeacrucialsystemcomponent.Theysupportbothmachine owners andmanufacturers in their effortsto increasemachine availability, performonly scheduledmaintenancewhen possible, and ultimately reduce theoverall cost of themachines over theirworking life. Fornumerousproductionplantsandinfleetmanagement,thecost-baseddecision-makingcriteriafornewinvestmentsisnolongerjusttheprocurementcostofamachine.Whatisalsoevaluatediswhatisreferredtoasthelifecyclecost(LCC),orthecostoverthemachine’sentireservicelife.Inadditiontoprocurementcosts,thisLCCalsoincludesthecostsforoperationanddisposal.Thisultimatelyreducestheactualoverallcostperunitinordertostaycompetitiveintheglobalmarket.Add to thiscertaincustomer requirementsthathavechangedovertime.Currentcustomerrequirements,usingtheexampleofmobileminingequipment:
zHigherproductivity zGreaterbreakoutforces zHigherefficiency
Tomeet these demands, the industry increasingly reliesontheuseofthefollowing(inadditiontoothermeasures):
zElectro-hydraulics zHighersystempressures zTightertolerances (nowinthesingleanddouble-digitµ-range)
Aninevitableside-effectofthistrendisthefactthatmachinesarebecomingincreasinglysensitivetocontaminationintheoil.Ifthecleanlinesslevelisnotmonitoredandeffortsforimprovementnotmadeearlyenough,wearand tearcangraduallyreducethesystemefficiency.Sometimesthesys-temefficiencycanfallby20%beforethemachineoperatorevennoticesaproblem.
Edition04/2016
Predictive maintenance – the strategy that predictswhenmachinerywillrequiremaintenance
zContinuousmonitoringofthemachineryviatheconditionofthefluidandthefluidconditioningcom-ponents
zIntegralpartofapredictivemaintenanceplan
zMaintenanceintervalscanbeplannedaccordingtoneed
zHelpstorevealdefectsanddevelopingdamageinduetime
zHelpstopreventunplannedmachinestoppages
Fluid Condition Monitoring at a glance:
zIncreasesavailability,safetyandproductivity
zIncreasesefficiency,becausecomponentsnolongerhavetobeover-sized
zAspartoftheLifeCycleManagement,costscanbesaved
This canbepreventedbyusingefficientFluidConditionMonitoring(FCM)sensorsandsubsystems.Thesedetectthedeviationsatanearlystageandenabletheusertotakepredictivecorrectiveactioningoodtime.
Market requirementsThe currentmarket requirements for productionmachinesareshowninFig.1.Theseapplygenerallytobothstationaryandmobilemachines.Twobasicrequirementsare:
z Immediatealarmintheeventofseriouserrors zReductionintheunitcostsofaproduct (where“product”canrefertoamachine-producedpartorahauledtonnageperhour)
In order tomeet these requirements, themachinesmustalwayshavethecharacteristicsinFig.1.
Customer specification Fluid condition sensor
Alarm for (fatal) errors Monitoring of the zplannedfluidoperationproperties(temperature,purity,etc.) z installedfluidconditioningcomponents(cooler,filter,etc.)
Reduced unit costs Reduced life cycle cost zProcurementcosts zOperatingcosts zDisposalcosts
Increases in zAvailability zReliability zEfficiency&productivity
Full utilisation of the service life of critical machine parts
Fig. 1
Fig. 2
Failu
re ra
te
Cause:initialcontamination
Cause:severecontamination ofthefluidduringoperation
Cause: long-termwear
Operating time
Initialstart-upphase Usagephase Fatiguephase
Maintenance timing: Tooearly ToolateOptimum
Preventive Condition-based Reactive
Maintenance management strategy:
Total costs
Costs, planned service
Costs, unplanned service
Reactive maintenancePreventive maintenanceCondition-based maintenance
Investment in Fluid Condition Monitoring
Costs, production
stoppage
100%
80%
60%
40%
20%
0%
Fig. 3
Currentmarketrequirementsforproductionmachines
Typicalservice-lifecurveofafluidsystem Typicalmaintenancecostdistribution ofthethreesystems
3
Edition04/2016
4
Condition-based, predictive maintenance strategyInordertomeettheabove-mentioneddemands,anappropri-atemaintenancemanagementconceptmustbeestablished.“Reactive”strategies(operationuntilfailure)and“preventive”strategiesareunabletominimisethetotalcostsfordowntime,maintenanceandcomponentexchange(seeFig.3,page3).Thechoicemustbefora“predictive”concept,whichistheonlyonethatallowstheservicelifeofallcriticalmachinepartstobefullyutilised,bydetectinga“rise”inlevels(“optimum”inFig.2,page3)whichindicatesthestartofa(fluid)deviationfromthenormalcondition.Thisisthebasisofasubstantialreduction in operating costs by cutting out orminimisingexpensive and unplannedmaintenance and stoppages.As soonas the beginnings of a variation are detected, itis possible to estimate howmuch service life remains forthecorrespondingparameterorcomponentandtousethisservice life inacontrolledmanner forongoingproduction.Meanwhile,sparepartscanbeprocuredandmaintenancewithminimalcostscanbescheduled.
Toclarifythispointfurther,theadvantagesanddisadvan-tagesofdifferentmaintenancemanagementconceptscanbedifferentiatedasfollows:
z In the reactivemodel, the biggest cost factors areunplannedmaintenanceandproductionstoppage. z In the preventivemodel the biggest cost factor is thehigh proportion of plannedmaintenance.Moreover,componentsarerejectedwhichcouldcontinuetobeused. z Inthepredictivemodel,therearesomesmalladditionalcostsinitiallyfortheFluidConditionMonitoringSystem,butthetotaloperatingcostsandthereforetheLCCarethelowest.
The typical cost distributions of the threemaintenancemanagementstrategiesarecomparedinFigure3.AsuitableFluidConditionMonitoring(FCM)Systemalwaysformsthebasisofpredictivemaintenancemanagement.Inpractice,twotypesofFCMcanbeimplemented,asshowninTable1:
Edition04/2016
Predictive maintenance – the strategy that predictswhenmachinerywillrequiremaintenance
Periodic / offline Continuous / onlineImplementation Servicecrewwithportableequipment IntegrationofsensorsFeatures • Oilsampling,measurementsusingparticlecounters
• Monitoringthemeasurementsoverlongertimeperiods• Variationsresultinspecificmeasures
• Permanentsensorinstallation• Definitionoflimits/alarmthresholds• Remotedatatransmissiontomonitoringcentres orcontrolrooms viaintranet/Internet/GSM/satellite• Variationsresultinimmediate specificservicemeasures
Examples
Table 1
Fig. 4
1. Optical particle counter 1. Inductive particle counter 2., 5. Δp sensor 3. Water sensors 4. Oil ageing sensors
Typicalformsoffluidconditionsensors
FormsofFluidConditionMonitoring(FCM)
5
Increase in efficiencyAfurthercostadvantageofFluidConditionMonitoringisob-tainedrightfromthedesignstagebecauseofthepossibilityofimprovingthesizingofthecomponents:
zComponents no longer need to be over-sized andthereforemoreexpensive. zThe risk of components being operated at the limit iseliminated. zThesystemhasahigherefficiencyasaresult.
Online fluid condition sensorsThegreatestbenefitofpermanentlyinstalledfluidconditionsensorsandsubsystemsisthefacilitytomonitorthefluidcondition
zonacontinuousbasis zpracticallyinreal-time.
The key systemcharacteristics to bemonitoredand theappropriate sensors (to complement the conventionalsensorsforpressure,temperature,flowrateetc.)arelistedinorderofpriorityinTable2.
Forimplementationinapredictivemaintenanceconcept,theelectricalsensoroutputsmustbeconfiguredaccordingtothefollowingguidelines:
zEssentially, the output signalsmust enable the systemortheoperatortoestimatetheremainingservicelifeofacomponentoraprocesstocarryoutplannedmaintenance. zSwitch outputs alone are usually adequate for slowprocesses. zAnalogueordigitalbusoutputsshouldideallybeusedforhighlytransientprocesses.
Edition04/2016
Table 2
System characteristic Fluid condition sensor
Wear 1.Solidparticlesensor
Fluid cross-contamination after addition of incorrect fluid or leakage
2.Differentialpressuresensorforfilters
Water ingress through condensation or leakage 3.Sensorforfreeordissolvedwater
Fluid ageing condition on basis of hydrolysis or oxidation 4.AN(acidnumber)sensor5.Differentialpressuresensorforfilters
Typicalapplicationsforfluidconditionsensors
Fluid technology, hydraulics, electronics and service. Worldwide.
Withover8,000employees,45overseascompaniesandmorethan500salesandservicepartners,HYDACisyourreliablepartnerworldwide.Oursupplyprogrammeincludes hydraulicaccumulators,fluidfilters,processfilters,coolers,electrohydrauliccontrols,industrialvalves,sensorsystemsforpressure,encodermeasurementandsolenoidtechnology,cylinders,pumps,mountingtechnology,armatures,conditionmonitoringandmuchmore.Wedesignandsupplyready-for-usehydrauliccontrolanddrivesystems,includingelectronicopen-loopandclosed-loopcontrolsformobileandstationarymachinesandplantsforawidearrayofindustries.
6
Edition04/2016
Predictive maintenance in practice
Inaviationtheguaranteedservicelifeforhydraulicpumpsisnormally10years.Thisleadstointensivequalitytestsandasaresult,higherwarrantycostsoverthewholelifecycleofthepumps.
Task Toreduceboththecostsofinspection(previouslycarriedoutmanually,withindividualoilsamplingandanalysis) andthewarrantycosts.
Solution Thenumberofwearparticlesproducedduringthefunctiontestisameasureoftheservicelifeofeverypump.Thereforeonlineparticlesensorsweretriedoutonthetestrigsandintroducedasonlinequalitytesting.
Result Inspectionandwarrantycostsreducedby>10%.
Aviation – hydraulic aircraft pumps
Intheminingindustryavailabilityandefficiencyareparamount.
Task Reduceunscheduledmaintenance,extendtheservicelifeofcriticalcomponentsandoils,increaseavailabilityandefficiency.
Solution Useofportableparticlecountersandofflinefiltration,bothperiodicallyandwhenlimitvaluesareexcee-ded.Dependingonthelocalcircumstances,samplebottles,portableparticlecountersandonlinesensorsareusedtodetectexcessivelyhighcontaminationlevels.
Result Unplannedmaintenanceworkwasreduced,availabilityandcomponentservicelifewasincreased (availability+10%,reliability+35%,unplannedrepairs-35%)
Mobile industry – mining vehicle fleets
Task Monitoringoftherequiredoilcleanlinessforwearpreventionandwateringressintothelubricatingoilofthrusterdrivesviaseals
Solution Installationofonlinefluidsensorsintheformofaready-for-connection,application-specificall-in-onesolutionResult zRequiredthrusteravailability
secured zDrydockwaitingtimes reducedby>60%
Marine/offshore industry
ThefollowingpracticalexamplesshowwaysthatFluidConditionMonitoringcanbeusedtoreducecosts:
Task Tomonitorthegearboxlubricationsystemonlineinordertopreventsecondarydamageandalsoproductionstoppages(electricitygeneration).
Solution InstallationofaMetallicContaminationSensor(MCS)forfull-flowmonitoringofthelubricationcircuit.Result zAstheimageshows,aMetallicContaminationSensor
(MCS)wasusedtodetectabearingfailure. z Thecurveshowsthenumberofaccumulatedparticles,i.e.theamountofmetaldetachedfromthedrivinggear.Eachjumpcorrespondstooneormoredetectedmetalparticles. z Thefirstwarningwasconfirmedbyavisualinspectionbecausethemainbearingshowedslightdamagebutthiswasclassedasnon-critical.Consistentwiththis,arepairwasplannedanduntilthenthewindturbinecouldcontinuetobeoperatedat80%capacity(thelowercurveinthegraphshowsthepowergenerated). z Theprogressofthedamagewasmonitoreduntilthebearingrepairwasperformed. zNounplannedmaintenanceordowntimewasrequiredandthecostsforanewgearbox(roughly€360,000)couldbeavoided.
ConclusionTheexampleslistedclearlyshowthatusingFluidConditionMonitoringincombinationwithapredictivecondition-basedmaintenancesystemandappropriatemeasurescanhelptoconsiderablyreducethemaintenanceandthecorrespondinglifecyclecostofproductionmachines.Furtheradditionalbenefitsare:
zRapidnotificationwhenfatalerrorsoccur zOpportunitiesforoptimisingcomponentandsystemservicelife
FluidConditionMonitoringisthereforeanefficientsystemdesignelementforreducingthelifecyclecostofmodernproductionmachines,predestinedforthedesignofpredictivemaintenancestrategies.
7
Edition04/2016
Inrollingmillstheoperatingfluidforcontrollingtherollsisexposedtoveryhighratesofsolid-particleandwateringress. Thisisinherenttotheconditionsofhot/coldrollingprocesses.
Task Toreduceunplannedmaintenanceanddowntimecostsbyinstallingfluidsensors.Solution StandardisationofaFluidConditionMonitoringsubsystemanditsintegrationinthehydrauliccircuit.
Thesubsystemconsistsofavisualparticlesensor,awatersensorandadata-loggingdevicewithdisplay.Result Themaintenanceand
downtimecosts couldbesignificantly reduced.
Wind energy – wind turbine gearbox
Steel industry – rolling mills
Roll adjustment in steel works
Planned maintenance
Unplanned maintenance
Before (no FCM)After (with FCM)
FCM
Production stoppage
20% 20%
30% 10%
0% 2%
50% 30%
100%
80%
60%
40%
20%
0%
2000 35000
30000
25000
20000
15000
100005000
0
18001600140012001000800600400200
008.05.08 08.05.28 08.06.17 08.07.07
Date
Part
icle
cou
nt, a
ccum
ulat
ed
Pow
er p
er d
ay [k
Wh]
08.07.27 08.09.05 08.06.17 08.09.25
Total costs
100% 62%
HeadOffice Industriegebiet HYDACINTERNATIONAL 66280Sulzbach/Saar GMBH Germany
Telephone: +496897509-01 Fax: +496897509-9046
E-mail:[email protected] Internet:www.hydac.com
4
E10.113.1.0/01.10
Global Presence.Local Expertise.www.hydac.com
CoolingSystems57.000
Electronics180.000
Accessories61.000
Com
pactHydraulics53.000
FilterS
ystems79.000
ProcessTechnology77.000
FluidFilters70.000
Accum
ulators30.000
Edition04/2016
HYDACHeadquartersHYDACCompaniesHYDACSalesandServicePartners