maint reliab

© 2006 Prentice Hall, Inc. 17 – 1

Henry Awuku-AsanteHenry Awuku-AsantePurchasing & GS ManagerPurchasing & GS ManagerBarry Callebaut Ghana Ltd,TemaBarry Callebaut Ghana Ltd,TemaM.Gh.I.E.M.Gh.I.E.B.Sc.(Hons) Mechanical EngineeringB.Sc.(Hons) Mechanical Engineering


Operations ManagementChapter 17 – Maintenance and Reliability

© 2006 Prentice Hall, Inc.

PowerPoint presentation to accompanyPowerPoint presentation to accompany Heizer/Render Heizer/Render Principles of Operations Management, 6ePrinciples of Operations Management, 6eOperations Management, 8e Operations Management, 8e


OutlineOutline

Impact of Maintenance Impact of Maintenance The Strategic Importance Of The Strategic Importance Of

Maintenance And ReliabilityMaintenance And Reliability ReliabilityReliability

Improving Individual ComponentsImproving Individual Components Providing RedundancyProviding Redundancy


Outline – ContinuedOutline – Continued

MaintenanceMaintenance Implementing Preventive MaintenanceImplementing Preventive Maintenance Evaluation of Maintenance EffectivenessEvaluation of Maintenance Effectiveness Increasing Repair CapabilityIncreasing Repair Capability

Total Productive MaintenanceTotal Productive Maintenance Techniques For Establishing Techniques For Establishing

Maintenance PoliciesMaintenance Policies


Learning ObjectivesLearning ObjectivesWhen you complete this chapter, you When you complete this chapter, you should be able to:should be able to:Identify or Define:Identify or Define:

MaintenanceMaintenance Mean time between failuresMean time between failures RedundancyRedundancy Preventive maintenancePreventive maintenance Breakdown maintenanceBreakdown maintenance Infant mortalityInfant mortality


Learning ObjectivesLearning ObjectivesWhen you complete this chapter, you When you complete this chapter, you should be able to:should be able to:Describe or Explain:Describe or Explain:

How to measure system reliabilityHow to measure system reliability How to improve maintenanceHow to improve maintenance How to evaluate maintenance How to evaluate maintenance

performanceperformance


Impact of MaintenanceImpact of Maintenance Maintenance costs constitute a major part of the Maintenance costs constitute a major part of the

total operating costs of all manufacturing plants. total operating costs of all manufacturing plants. Depending on the specific industry, maintenance Depending on the specific industry, maintenance cost can represent between 15% and 60% of the cost cost can represent between 15% and 60% of the cost of production. of production. For example, in the food related industries, average For example, in the food related industries, average maintenance cost represent about 15% whereas in maintenance cost represent about 15% whereas in the heavy industries such as mining, iron and steel, the heavy industries such as mining, iron and steel, it represents up to 60% of the total production cost it represents up to 60% of the total production cost

Recent surveys of maintenance management Recent surveys of maintenance management effectiveness indicate that one- third(33%) out of effectiveness indicate that one- third(33%) out of every dollar (of all maintenance cost) is wasted as a every dollar (of all maintenance cost) is wasted as a result of unnecessary or improperly carried out result of unnecessary or improperly carried out maintenance.maintenance.


Impact of MaintenanceImpact of Maintenance The losses of production time and product quality The losses of production time and product quality

due to ineffective maintenance management by due to ineffective maintenance management by industries have a significant impact on their industries have a significant impact on their competitiveness on the world marketcompetitiveness on the world market

Courtesy: An Introduction to Predictive MaintenanceCourtesy: An Introduction to Predictive Maintenance By: R. Keith MobleyBy: R. Keith Mobley


Strategic Importance of Strategic Importance of Maintenance and ReliabilityMaintenance and Reliability

Failure has far reaching effects on a Failure has far reaching effects on a firm’sfirm’s OperationOperation ReputationReputation ProfitabilityProfitability Dissatisfied customersDissatisfied customers Idle employeesIdle employees Profits becoming lossesProfits becoming losses Reduced value of investment in plant and Reduced value of investment in plant and

equipmentequipment


Maintenance and ReliabilityMaintenance and Reliability The objective of maintenance and The objective of maintenance and

reliability is to maintain the reliability is to maintain the capability of the system while capability of the system while controlling costscontrolling costs Maintenance is all activities involved Maintenance is all activities involved

in keeping a system’s equipment in in keeping a system’s equipment in working orderworking order

Reliability is the probability that a Reliability is the probability that a machine will function properly for a machine will function properly for a specified timespecified time


Important TacticsImportant Tactics

ReliabilityReliability1.1. Improving individual componentsImproving individual components2.2. Providing redundancyProviding redundancy

MaintenanceMaintenance1.1. Implementing or improving Implementing or improving

preventive maintenancepreventive maintenance2.2. Increasing repair capability or speedIncreasing repair capability or speed


Strategy and ResultsStrategy and ResultsEmployee InvolvementEmployee Involvement

Information sharingSkill trainingReward systemPower sharing

Maintenance and Reliability Maintenance and Reliability ProceduresProcedures

Clean and lubricateMonitor and adjustMinor repairComputerize records

ResultsResults

Reduced inventoryImproved qualityImproved capacityReputation for qualityContinuous improvementReduced variability

Figure 17.1Figure 17.1


ReliabilityReliability

Improving individual componentsImproving individual components

RRss = R = R11 x R x R22 x R x R33 x … x R x … x Rnn

wherewhere RR11 = reliability of component 1= reliability of component 1RR22 = reliability of component 2= reliability of component 2

and so onand so on


Overall System ReliabilityOverall System Reliability

Reliability of the system

R

eliability of the system

(percent)(percent)

Average reliability of all components (percent)Average reliability of all components (percent)

| | | | | | | | |

100100 9999 9898 9797 9696

100 100 –

80 80 –

60 60 –

40 40 –

20 20 –

0 0 –

n = 10

n = 1

n = 50

n = 100n = 200n = 300

n = 400



RRss

RR33

.99

RR22

.80

Reliability ExampleReliability Example

RR11

.90

Reliability of the process isReliability of the process is

RRss = R = R11 x R x R22 x R x R33 = .90 x .80 x .99 = .713 or 71.3%= .90 x .80 x .99 = .713 or 71.3%


Product Failure Rate (FR)Product Failure Rate (FR)Basic unit of measure for reliabilityBasic unit of measure for reliability

FRFR((%%) ) = x = x 100%100%Number of failuresNumber of failuresNumber of units testedNumber of units tested

FRFR((NN)) = = Number of failuresNumber of failuresNumber of unit-hours of operating timeNumber of unit-hours of operating time

Mean time between failuresMean time between failures

MTBF =MTBF = 11FRFR((NN))


Failure Rate ExampleFailure Rate Example2020 air conditioning units designed for use in air conditioning units designed for use in NASA space shuttles operated for NASA space shuttles operated for 1,0001,000 hours hoursOne failed after One failed after 200 200 hours and one after hours and one after 600600 hours hours

FRFR((%%)) = (100%) = 10%= (100%) = 10%222020

FRFR((NN)) = = .000106 = = .000106 failure/unit hrfailure/unit hr2220,000 - 1,20020,000 - 1,200

MTBF MTBF = = 9,434 = = 9,434 hrshrs11.000106.000106


Failure Rate ExampleFailure Rate Example2020 air conditioning units designed for use in air conditioning units designed for use in NASA space shuttlesNASA space shuttles operated for operated for 1,0001,000 hours hoursOne failed after One failed after 200 200 hours and one after hours and one after 600600 hours hours

FRFR((%%)) = (100%) = 10%= (100%) = 10%222020

FRFR((NN)) = = .000106 = = .000106 failure/unit hrfailure/unit hr2220,000 - 1,20020,000 - 1,200

MTBF MTBF = = 9,434 = = 9,434 hrhr11.000106.000106

Failure rate per trip

FR = FR(N)(24 hrs)(60 days/trip)FR = (.000106)(24)(60)FR = .152 failures per trip


Providing RedundancyProviding Redundancy Redundancy for a system may be provided in one of Redundancy for a system may be provided in one of

the following waysthe following ways One for One RedundancyOne for One Redundancy N + X RedundancyN + X Redundancy Load SharingLoad Sharing


Providing RedundancyProviding Redundancy

Provide backup components to Provide backup components to increase reliabilityincrease reliability

++ xxProbability Probability

of first of first component component

workingworking

Probability Probability of needing of needing

second second component component

Probability Probability of second of second

component component workingworking

(.8)(.8) ++ (.8)(.8) xx (1 - .8)(1 - .8)= .8= .8 ++ .16 = .96.16 = .96


Redundancy ExampleRedundancy ExampleA redundant process is installed to support A redundant process is installed to support the earlier example where Rthe earlier example where Rss = .713= .713

RR11

0.90.900 0.90.900

RR22

0.80.800 0.80.800

RR33

0.90.999

= [.9 + .9(1 - .9)] x [.8 + .8(1 - .8)] x .99= [.9 + .9(1 - .9)] x [.8 + .8(1 - .8)] x .99= [.9 + (.9)(.1)] x [.8 + (.8)(.2)] x .99= [.9 + (.9)(.1)] x [.8 + (.8)(.2)] x .99= .99 x .96 x .99 = .94= .99 x .96 x .99 = .94

Reliability has increased

from .713 to .94


MaintenanceMaintenance Two types of maintenanceTwo types of maintenance

Planned or Preventive maintenance – routine Planned or Preventive maintenance – routine inspection or monitoring and servicing to keep inspection or monitoring and servicing to keep facilities in good repairfacilities in good repairSystematic or Fixed Time Maintenance Systematic or Fixed Time Maintenance Maintenance carried out based on a fixed Maintenance carried out based on a fixed

time schedule (ie Hours, days or Months)time schedule (ie Hours, days or Months)Predictive or Condition-Based MaintenancePredictive or Condition-Based Maintenance

Maintenance carried out based on pre-Maintenance carried out based on pre-determined key performance indicators of determined key performance indicators of the system (ie vibration, temperature, the system (ie vibration, temperature, Pressure, Current, noise level, thickness) Pressure, Current, noise level, thickness)

Unplanned or Breakdown maintenance – Unplanned or Breakdown maintenance – emergency or priority repairs on failed emergency or priority repairs on failed equipment. equipment. Also known as Run to FailureAlso known as Run to Failure


Why Machines failWhy Machines fail Machine failure may be caused by defects in any of Machine failure may be caused by defects in any of

the following stages of the machine life cyclethe following stages of the machine life cycle Design stageDesign stage Manufacturing stageManufacturing stage Transportation StageTransportation Stage Installation sageInstallation sage Type of maintenance practices and operating Type of maintenance practices and operating

conditionsconditionsThus, the ultimate life span of a machine will be Thus, the ultimate life span of a machine will be determined by the precision with which the above determined by the precision with which the above factors are carried out.factors are carried out.


Implementing Preventive MaintenanceImplementing Preventive Maintenance Need to know WHAT to maintain :Thus identify and Need to know WHAT to maintain :Thus identify and

compile a facility register (list of all equipment to be compile a facility register (list of all equipment to be maintained with given IDs)maintained with given IDs)

Need to know WHO to maintain: Thus which Need to know WHO to maintain: Thus which equipment has to be serviced in-house or out-equipment has to be serviced in-house or out-sourced and by which discipline( ie Mechanical, sourced and by which discipline( ie Mechanical, electrical, instrumentation or civil) This decision will electrical, instrumentation or civil) This decision will be based on level of skills and capacity of in-house be based on level of skills and capacity of in-house staffstaff

Need to know HOW to maintain:Need to know HOW to maintain:Decide on type of PM to apply for each facilityDecide on type of PM to apply for each facility


Implementing Preventive MaintenanceImplementing Preventive MaintenancePrepare a maintenance checklist for each facility Prepare a maintenance checklist for each facility

with the help of equipment manual and with the help of equipment manual and experience.experience.

A maintenance checklist is a comprehensive A maintenance checklist is a comprehensive list list of all maintenance activities to be performed of all maintenance activities to be performed at at various periods (eg running hours, months or various periods (eg running hours, months or a a set measurement limit) in the life of an set measurement limit) in the life of an equipment equipment as recommended by the manufactureras recommended by the manufacturer

Need to know WHEN a system requires service or is Need to know WHEN a system requires service or is likely to fail: Thus provide an annual maintenance likely to fail: Thus provide an annual maintenance programme or service forecast indicating all programme or service forecast indicating all equipment and when they are due for servicingequipment and when they are due for servicing


Implementing Preventive MaintenanceImplementing Preventive Maintenance

Good reporting and record keeping can aid the Good reporting and record keeping can aid the decision on when preventive maintenance should be decision on when preventive maintenance should be performedperformed



High initial failure rates are known as infant mortality. High initial failure rates are known as infant mortality. Occurs during the early stages of a machine life and Occurs during the early stages of a machine life and may be due to :may be due to :Design or manufacturing defectsDesign or manufacturing defectsInstallation defectsInstallation defectsOperational adjustments or fine tuningOperational adjustments or fine tuning

The useful life generally constitutes the longest The useful life generally constitutes the longest phase of the machine life cycle. Here the failure rate phase of the machine life cycle. Here the failure rate is lowest and constant with time. The length of this is lowest and constant with time. The length of this cycle vary from machine to machine even with cycle vary from machine to machine even with similar ones and depends on the effectiveness of the similar ones and depends on the effectiveness of the maintenance policy practicedmaintenance policy practiced



The end of life or the wear-out life is the last phase of The end of life or the wear-out life is the last phase of a machine life cycle. It is at the end of its useful life a machine life cycle. It is at the end of its useful life and that is when a decision to replace must be taken.and that is when a decision to replace must be taken.During this stage strength and reliability is greatly During this stage strength and reliability is greatly

reduced by wear/corrosion, material properties reduced by wear/corrosion, material properties change for the worse.change for the worse.

High maintenance cost due to frequent failuresHigh maintenance cost due to frequent failures


Evaluation of Maintenance EffectivenessEvaluation of Maintenance Effectiveness Availability = Availability = Total Machine Hrs Wkd Total Machine Hrs Wkd x 100%x 100%

Total Hrs ConsideredTotal Hrs Considered Total Machine Hrs =Total Hrs – Engineering DowntimeTotal Machine Hrs =Total Hrs – Engineering Downtime Utilization of Available Machine Hrs = Utilization of Available Machine Hrs = Production HrsProduction Hrs x 100% x 100%

Machine HrsMachine Hrs MTBF = MTBF = Total Machine HrsTotal Machine Hrs No. of FailuresNo. of Failures MTBF: Mean Time Between Failures MTBF: Mean Time Between Failures MTTRMTTR = = Total Machine HrsTotal Machine Hrs

No. of FailuresNo. of Failures MTTF: Mean Time To Repair/ MTTF: Mean Time To Repair/ Failure Failure Availability = Availability = MTBFMTBF x 100% x 100% FR = FR = No. of FailuresNo. of Failures

MTBF + MTTR Total Machine HrsMTBF + MTTR Total Machine Hrs

FR : Failure RateFR : Failure Rate Maintenance Index MI = Maintenance Index MI = Production HrsProduction Hrs

Production Hrs + Machine Hrs Production Hrs + Machine Hrs Manpower Utilization = Manpower Utilization = Machine HrsMachine Hrs

Total Man Hrs AvailableTotal Man Hrs Available


Computerized Maintenance Computerized Maintenance Management SystemManagement System

This is the use of Information Technology to manage This is the use of Information Technology to manage Maintenance operations in the areas of :Maintenance operations in the areas of :Work order ManagementWork order ManagementEquipment Planning and SchedulingEquipment Planning and SchedulingAsset ManagementAsset ManagementInventory ManagementInventory ManagementPurchasingPurchasingReports and AnalysesReports and Analyses



Some of the known software for maintenance Some of the known software for maintenance systems are:systems are:MaximoMaximoMain TrackerMain Tracker

The Need for CMMSThe Need for CMMSEnables large volumes of data to be stored and Enables large volumes of data to be stored and processed in an accurate and timely mannerprocessed in an accurate and timely mannerEnhance management decision makingEnhance management decision making




Output ReportsOutput Reports

Inventory and purchasing reports

Equipment parts list

Equipment history reports

Cost analysis (Actual vs. standard)

Work orders– Preventive

maintenance– Scheduled

downtime– Emergency

maintenance

Data entry– Work requests– Purchase

requests– Time reporting– Contract work

Data FilesData Files

Personnel data with skills, wages, etc.

Equipment file with parts list

Maintenanceand work order

schedule

Inventory of spare parts

Repair history file


Maintenance CostsMaintenance Costs The three main elements maintenance The three main elements maintenance

costs are:costs are: Direct costDirect cost Indirect costIndirect cost Capital costCapital cost

Direct costDirect costCosts which are primarily due to Costs which are primarily due to maintenance activities and comprises of:maintenance activities and comprises of:

Labour costLabour cost


Maintenance CostsMaintenance Costs Spare parts costSpare parts cost Equipment costEquipment cost Training costTraining cost Service contractsService contracts Maintenance AdministrationMaintenance Administration

Indirect costIndirect costThese are costs incurred when a plant These are costs incurred when a plant /equipment unavailable for production due to a /equipment unavailable for production due to a breakdown. They include:breakdown. They include: Production lossesProduction losses


Maintenance CostsMaintenance Costs Delivery Delays-payment of penaltiesDelivery Delays-payment of penalties Work accidents-higher insurance premiumsWork accidents-higher insurance premiums Poor quality products/servicePoor quality products/service Personnel de-motivationPersonnel de-motivation Company ImageCompany Image Environmental disastersEnvironmental disasters

Capital costsCapital costsThe depreciation cost of facilities associated The depreciation cost of facilities associated with maintenance eg:with maintenance eg: Standby equipmentStandby equipment


Maintenance CostsMaintenance Costs Standby equipmentStandby equipment Workshop/Utility equipmentWorkshop/Utility equipment Stock of spare partsStock of spare parts Material handling equipmentMaterial handling equipment


Maintenance CostsMaintenance Costs The traditional view attempted to The traditional view attempted to

balance preventive and breakdown balance preventive and breakdown maintenance costs maintenance costs

Typically this approach failed to Typically this approach failed to consider the true total cost of consider the true total cost of breakdownsbreakdowns InventoryInventory Employee moraleEmployee morale Schedule unreliabilitySchedule unreliability


Maintenance CostsMaintenance Costs

Figure 17.4 (a)Figure 17.4 (a)

Total Total costscosts

Breakdown Breakdown maintenance maintenance costscosts

Cost

Cost

ss

Maintenance commitmentMaintenance commitment

Traditional ViewTraditional View

Preventive Preventive maintenance maintenance costscosts

Optimal point (lowestOptimal point (lowestcost maintenance policy)cost maintenance policy)


Maintenance CostsMaintenance Costs

Figure 17.4 (b)Figure 17.4 (b)

Cost

Cost

ss

Maintenance commitmentMaintenance commitment

Full Cost ViewFull Cost View

Optimal point (lowestOptimal point (lowestcost maintenance policy)cost maintenance policy)

Total Total costscosts

Full cost of Full cost of breakdownsbreakdowns

Preventive Preventive maintenance maintenance costscosts


Maintenance Cost ExampleMaintenance Cost ExampleShould the firm contract for maintenance Should the firm contract for maintenance on their printers?on their printers?

Number of Number of BreakdownsBreakdowns

Number of Months That Number of Months That Breakdowns OccurredBreakdowns Occurred

00 2211 8822 6633 4

Total: Total: 2020

Average cost of breakdown Average cost of breakdown = $300= $300


Maintenance Cost ExampleMaintenance Cost Example1.1. Compute the expected number of Compute the expected number of

breakdownsbreakdownsNumber of Number of

BreakdownsBreakdownsFrequencyFrequency Number of Number of

BreakdownsBreakdownsFrequencyFrequency

00 2/20 = .12/20 = .1 22 6/20 = .36/20 = .3

11 8/20 = .48/20 = .4 33 4/20 = .24/20 = .2

∑∑ Number of Number of breakdownsbreakdowns

Expected number Expected number of breakdownsof breakdowns

Corresponding Corresponding frequencyfrequency== xx

= (0)(.1) + (1)(.4) + (2)(.3) + (3)(.2)= (0)(.1) + (1)(.4) + (2)(.3) + (3)(.2)= 1.6= 1.6 breakdowns per month breakdowns per month


Maintenance Cost ExampleMaintenance Cost Example1.1. Compute the expected breakdown cost per Compute the expected breakdown cost per

month with no preventive maintenancemonth with no preventive maintenance

Expected Expected breakdown costbreakdown cost

Expected number Expected number of breakdownsof breakdowns

Cost per Cost per breakdownbreakdown== xx

= (1.6)($300)= (1.6)($300)= $480= $480 per month per month


Maintenance Cost ExampleMaintenance Cost Example1.1. Compute the cost of preventive Compute the cost of preventive

maintenancemaintenance

Preventive Preventive maintenance costmaintenance cost

Cost of expected Cost of expected breakdowns if service breakdowns if service contract signedcontract signed

Cost of Cost of service contractservice contract

==++

= (1= (1 breakdown/month breakdown/month)($300) + $150)($300) + $150/month/month= $450= $450 per month per month

Hire the service firm; it is less expensive


Increasing Repair Increasing Repair CapabilitiesCapabilities

1.1. Well-trained personnelWell-trained personnel2.2. Adequate resourcesAdequate resources3.3. Ability to establish repair plan and Ability to establish repair plan and

prioritiespriorities4.4. Ability and authority to do material Ability and authority to do material

planningplanning5.5. Ability to identify the cause of Ability to identify the cause of

breakdownsbreakdowns6.6. Ability to design ways to extend MTBFAbility to design ways to extend MTBF


How Maintenance is How Maintenance is PerformedPerformed


OperatorOperator Maintenance Maintenance departmentdepartment

Manufacturer’s Manufacturer’s field servicefield service

Depot serviceDepot service(return equipment)(return equipment)

Preventive maintenance costs less and is faster the more we move to the left

Competence is higher as we move to the right

Should maintenance be in-house or out-sourced?Should maintenance be in-house or out-sourced?


Total Productive Total Productive Maintenance (TPM)Maintenance (TPM)

Designing machines that are reliable, easy to Designing machines that are reliable, easy to operate, and easy to maintainoperate, and easy to maintain

Emphasizing total cost of ownership when Emphasizing total cost of ownership when purchasing machines so that service and purchasing machines so that service and maintenance are included in the costmaintenance are included in the cost

Developing preventive maintenance plans that Developing preventive maintenance plans that utilize the best practices of operators, utilize the best practices of operators, maintenance departments, and depot servicemaintenance departments, and depot service

Training workers to operate and maintain their Training workers to operate and maintain their own machinesown machines


Establishing Maintenance Establishing Maintenance PoliciesPolicies

SimulationSimulation Computer analysis of complex Computer analysis of complex

situationssituations Model maintenance programs before Model maintenance programs before

they are implementedthey are implemented Expert systemsExpert systems

Computers help users identify Computers help users identify problems and select course of actionproblems and select course of action

maint reliab

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