Heizer/Render 11e

Maintenance and ReliabilityPowerPoint presentation to accompany Heizer and Render Operations Management, Eleventh EditionPrinciples of Operations Management, Ninth Edition

PowerPoint slides by Jeff HeylAdditional content from Gerry Cook17 2014 Pearson Education, Inc.17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #OutlineGlobal Company Profile: Orlando Utilities CommissionThe Strategic Importance of Maintenance and ReliabilityReliabilityMaintenanceTotal Productive Maintenance17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #2Learning ObjectivesWhen you complete this chapter you should be able to:Describe how to improve system reliabilityDetermine system reliabilityDetermine mean time between failure (MTBF)Distinguish between preventive and breakdown maintenance17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #3When you complete this chapter you should be able to:

Learning ObjectivesDescribe how to improve maintenanceCompare preventive and breakdown maintenance costsDefine autonomous maintenance17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #4

Orlando Utilities CommissionMaintenance of power generating plantsEvery year each plant is taken off-line for 1-3 weeks maintenanceEvery three years each plant is taken off-line for 6-8 weeks for complete overhaul and turbine inspectionEach overhaul has 1,800 tasks and requires 72,000 labor hoursOUC performs over 12,000 maintenance tasks each year 2014 Pearson Education, Inc.17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #5

Orlando Utilities CommissionEvery day a plant is down costs OUC $110,000Unexpected outages cost between $350,000 and $600,000 per dayPreventive maintenance discovered a cracked rotor blade which could have destroyed a $27 million piece of equipment 2014 Pearson Education, Inc.17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #6Strategic Importance of Maintenance and ReliabilityThe objective of maintenance and reliability is to maintain the capability of the system17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #7Strategic Importance of Maintenance and ReliabilityFailure has far reaching effects on a firmsOperationReputationProfitabilityCustomer satisfactionReducing idle timeProtecting investment in plant and equipment17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #8Maintenance and ReliabilityMaintenance is all activities involved in keeping a systems equipment in working orderReliability is the probability that a machine will function properly for a specified time17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #9Important TacticsReliabilityImproving individual componentsProviding redundancyMaintenanceImplementing or improving preventive maintenanceIncreasing repair capability or speed17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #10Maintenance ManagementEmployee InvolvementPartnering with maintenance personnelSkill trainingReward systemEmployee empowermentMaintenance and Reliability ProceduresClean and lubricateMonitor and adjustMake minor repairKeep computerized recordsResultsReduced inventoryImproved qualityImproved capacityReputation for qualityContinuous improvementReduced variabilityFigure 17.117 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #11ReliabilitySystem reliabilityImproving individual componentsRs = R1 x R2 x R3 x x RnwhereR1= reliability of component 1R2= reliability of component 2

and so on17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #12Overall System ReliabilityReliability of the system (percent)Average reliability of each component (percent)|||||||||10099989796100 80 60 40 20 0 n = 10n = 1n = 50n = 100n = 200n = 300n = 400Figure 17.217 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #13RsR3.99R2.80Reliability ExampleR1.90Reliability of the process isRs = R1 x R2 x R3 = .90 x .80 x .99 = .713 or 71.3%17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #14Product Failure Rate (FR)Basic unit of measure for reliabilityFR(%) = x 100%Number of failuresNumber of units testedFR(N) =Number of failuresNumber of unit-hours of operating timeMean time between failuresMTBF =1FR(N)17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #15Failure Rate Example20 air conditioning units for use in the international space station operated for 1,000 hoursOne failed after 200 hours and one after 600 hoursFR(%) = (100%) = 10%220FR(N) = = .000106 failure/unit hr220,000 - 1,200MTBF = = 9,434 hrs1.00010617 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #16Failure Rate Example20 air conditioning units for use in the international space station operated for 1,000 hoursOne failed after 200 hours and one after 600 hoursFR(%) = (100%) = 10%220FR(N) = = .000106 failure/unit hr220,000 - 1,200MTBF = = 9,434 hrs1.000106Failure rate per tripFR = FR(N)(24 hrs)(6 days/trip)FR = (.000106)(24)(6)FR = .0153 failure/trip17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #17Providing RedundancyProvide backup components to increase reliability+xProbability of first component workingProbability of needing second component Probability of second component workingRS =(.8)+(.8)x(1 - .8)= .8+.16 = .96=17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #18Redundancy ExampleA redundant process is installed to support the earlier example where Rs = .713R10.900.90R20.800.80R30.99RS= [.9 + .9(1 - .9)] x [.8 + .8(1 - .8)] x .99= [.9 + (.9)(.1)] x [.8 + (.8)(.2)] x .99= .99 x .96 x .99 = .94Reliability has increased from.713 to .9417 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #19Parallel RedundancyIncreased reliability through parallel redundancyR10.950.95R40.975R20.975R3Reliability for the middle path= R2 x R3 = .975 x .975 = .9506Probability of failure for all 3 paths= (1 0.95) x (1 .9506) x (1 0.95)= (.05) x (.0494) x (.05) = .00012Reliability of new design = 1 .00012 = .9998817 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #MaintenanceTwo types of maintenancePreventive maintenance routine inspection and servicing to keep facilities in good repairBreakdown maintenance emergency or priority repairs on failed equipment17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #21Implementing Preventive MaintenanceNeed to know when a system requires service or is likely to failHigh initial failure rates are known as infant mortalityOnce a product settles in, MTBF generally follows a normal distributionGood reporting and record keeping can aid the decision on when preventive maintenance should be performed17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #22Computerized Maintenance SystemFigure 17.3Output ReportsInventory and purchasing reportsEquipment parts listEquipment history reportsCost analysis (Actual vs. standard)Work ordersData FilesPersonnel data with skills, wages, etc.Equipment file with parts listMaintenanceand work order scheduleInventory of spare partsRepair history file

17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #23Maintenance CostsThe traditional view attempted to balance preventive and breakdown maintenance costs Typically this approach failed to consider the full costs of a breakdownInventoryEmployee moraleSchedule unreliability

17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #24Maintenance CostsFigure 17.4 (a)Total costsBreakdown maintenance costsCostsMaintenance commitmentTraditional ViewPreventive maintenance costsOptimal point (lowestcost maintenance policy)17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #25Maintenance CostsFigure 17.4 (b)CostsMaintenance commitmentFull Cost ViewOptimal point (lowestcost maintenance policy)Total costsFull cost of breakdownsPreventive maintenance costs17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #26Maintenance Cost ExampleShould the firm contract for maintenance on their printers?NUMBER OF BREAKDOWNSNUMBER OF MONTHS THAT BREAKDOWNS OCCURRED02182634Total :20Average cost of breakdown = $30017 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #27Maintenance Cost ExampleCompute the expected number of breakdownsNUMBER OF BREAKDOWNSFREQUENCYNUMBER OF BREAKDOWNSFREQUENCY02/20 = .126/20 = .318/20 = .434/20 = .2Number of breakdownsExpected number of breakdownsCorresponding frequency=x= (0)(.1) + (1)(.4) + (2)(.3) + (3)(.2)= 0 + .4 + .6 + .6= 1.6 breakdowns / month17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #28Maintenance Cost ExampleCompute the expected breakdown cost per month with no preventive maintenanceExpected breakdown costExpected number of breakdownsCost per breakdown=x= (1.6)($300)= $480 per month17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #29Maintenance Cost ExampleCompute the cost of preventive maintenancePreventive maintenance costCost of expected breakdowns if service contract signedCost of service contract=+= (1 breakdown / month)($300) + $150 / month= $450 / monthHire the service firm; it is less expensive17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #30Increasing Repair CapabilitiesWell-trained personnelAdequate resourcesAbility to establish repair plan and prioritiesAbility and authority to do material planningAbility to identify the cause of breakdownsAbility to design ways to extend MTBF17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #31Increasing Repair CapabilitiesFigure 17.5Operator(autonomous maintenance)Maintenance departmentManufacturers field serviceDepot service(return equipment)Increasing Operator OwnershipIncreasing ComplexityPreventive maintenance costs less and is faster the more we move to the leftCompetence is higher as we move to the right17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #32Autonomous MaintenanceEmployees accept responsibility forObserveCheckAdjustCleanNotifyPredict failures, prevent breakdowns, prolong equipment life17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #Total Productive Maintenance (TPM)Designing machines that are reliable, easy to operate, and easy to maintainEmphasizing total cost of ownership when purchasing machines, so that service and maintenance are included in the cost17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #34Total Productive Maintenance (TPM)Developing preventive maintenance plans that utilize the best practices of operators, maintenance departments, and depot serviceTraining for autonomous maintenance so operators maintain their own machines and partner with maintenance personnel17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #35More on Maintenance A simple redundancy formulaProblems with breakdown and preventive maintenancePredictive maintenancePredictive maintenance toolsMaintenance strategy implementationEffective reliabilitySupplemental Material17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #Providing Redundancy An Alternate FormulaThe reliability of one pump =The probability of one pump not failing = 0.8P(failing) = 1- P(not failing) = 1 - 0.8 = .2 P(failure of both pumps) =P(failure) pump #1 x P(failure) pump #2P(failure of both pumps) = 0.2 x 0.2 = .04P(at least one pump working) = 1.0 - .04 = .96If there are two pumps with the same probability of not failing17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #3737Problems With Breakdown MaintenanceRun it till it breaksMight be ok for low criticality equipment or redundant systemsCould be disastrous for mission-critical plant machinery or equipmentNot permissible for systems that could imperil life or limb (like aircraft)

17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #3838Problems With Preventive MaintenanceFix it whether or not it is brokenScheduled replacement or adjustment of parts/equipment with a well-established service lifeTypical example plant relampingSometimes misappliedReplacing old but still good bearingsOver-tightening electrical lugs in switchgear17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #3939Another Maintenance StrategyPredictive maintenance Using advanced technology to monitor equipment and predict failuresUsing technology to detect and predict imminent equipment failureVisual inspection and/or scheduled measurements of vibration, temperature, oil and water qualityMeasurements are compared to a healthy baselineEquipment that is trending towards failure can be scheduled for repair17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #4040Predictive Maintenance ToolsVibration analysisInfrared ThermographyOil and Water AnalysisOther Tools:Ultrasonic testingLiquid Penetrant Dye testingShock Pulse Measurement (SPM)17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #4141Predictive Maintenance Vibration AnalysisUsing sensitive transducers and instruments to detect and analyze vibrationTypically used on expensive, mission-critical equipmentlarge turbines, motors, engines or gearboxesSophisticated frequency (FFT) analysis can pinpoint the exact moving part that is worn or defectiveCan utilize a monitoring service17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #4242Predictive Maintenance Infrared (IR) ThermographyUsing IR cameras to look for temperature hot spots on equipmentTypically used to check electrical equipment for wiring problems or poor/loose connectionsCan also be used to look for cold (wet) spots when inspecting roofs for leaksHigh quality IR cameras are expensive most pay for IR thermography services 17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #4343Predictive Maintenance Oil and Water AnalysisTaking oil samples from large gearboxes, compressors or turbines for chemical and particle analysisParticle size can indicate abnormal wearTaking cooling water samples for analysis can detect excessive rust, acidity, or microbiological foulingServices usually provided by oil vendors and water treatment companies

17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #4444Predictive Maintenance Other Tools and TechniquesUltrasonic and dye testing used to find stress cracks in tubes, turbine blades and load bearing structuresUltrasonic waves sent through metalSurface coated with red dye, then cleaned off, dye shows cracksShock-pulse testing a specialized form of vibration analysis used to detect flaws in ball or roller bearings at high frequency (32kHz)17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #4545Maintenance Strategy ComparisonMAINTENANCE STRATEGYADVANTAGESDISADVANTAGESRESOURCES/ TECHNOLOGY REQUIREDAPPLICATION EXAMPLEBreakdownNo prior work requiredDisruption of production, injury or deathMay need labor/parts at odd hoursOffice copierPreventiveWork can be scheduledLabor cost, may replace healthy componentsNeed to obtain labor/parts for repairsPlant relamping, machine lubricationPredictiveImpending failures can be detected & work scheduledLabor costs, costs for detection equipment and servicesVibration, IR analysis equipment or purchased servicesVibration and oil analysis of a large gearbox17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #4646Maintenance Strategy ImplementationBreakdownPreventivePredictive12345678910Year100%80%60%40%20%0%Percentage of Maintenance Time by Strategy17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #4747Is Predictive Maintenance Cost Effective?In most industries the average rate of return is 7:1 to 35:1 for each predictive maintenance dollar spentVibration analysis, IR thermography and oil/water analysis are all economically proven technologiesThe real savings is the avoidance of manufacturing downtime especially crucial in JIT17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #Predictive Maintenance and Effective ReliabilityEffective Reliability (Reff) is an extension of Reliability that includes the probability of failure times the probability of not detecting imminent failureHaving the ability to detect imminent failures allows us to plan maintenance for the component in failure mode, thus avoiding the cost of an unplanned breakdownReff = 1 (P(failure) x P(not detecting failure))

17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #4949How Predictive Maintenance Improves Effective ReliabilityExample: a large gearbox with a reliability of .90 has vibration transducers installed for vibration monitoring. The probability of early detection of a failure is .70. What is the effective reliability of the gearbox?Reff = 1 (P(failure) x P(not detecting failure))Reff = 1 (.10 x .30) = 1 - .03 = .97Vibration monitoring has increased the effective reliability from .90 to .97!

17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #5050Effective Reliability CaveatsPredictive maintenance only increases effective reliability if:You select the method that can detect the most likely failure modeYou monitor frequently enough to have high likelihood of detecting a change in component behavior before failureTimely action is taken to fix the issue and forestall the failure (in other words you dont ignore the warning!) 17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #5151Increasing Repair CapabilitiesWell-trained personnelAdequate resourcesProper application of the three maintenance strategiesContinual improvement to improve equipment/system reliability 17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #5252All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. Printed in the United States of America.

17 - # 2014 Pearson Education, Inc. 2014 Pearson Education, Inc.17 - #