Operations Operations ManagementManagement

Maintenance and ReliabilityMaintenance and Reliability保養維護與可靠程度保養維護與可靠程度

Chapter 17Chapter 17

OutlineOutline GLOBAL COMPANY PROFILE: NASA THE STRATEGIC IMPORTANCE OF

MAINTENANCE AND RELIABILITY RELIABILITY

Improving Individual Components Providing Redundancy

MAINTENANCE Implementing Preventive Maintenance Increasing Repair Capability

TOTAL PRODUCTIVE MAINTENANCE TECHNIQUES FOR ESTABLISHING

MAINTENANCE POLICIES

Learning ObjectivesLearning Objectives

When you complete this chapter, you should be able to :

Identify or Define: Maintenance Mean time between failures Redundancy Preventive maintenance Breakdown maintenance Infant mortality

Learning Objectives - continuedLearning Objectives - continued

When you complete this chapter, you should be able to :

Describe or Explain: How to measure system reliability How to improve maintenance How to evaluate maintenance performance

NASANASA Maintenance of space shuttles Columbia:

86,000,000 miles on odometer 3 engines each the size of a VW expected to make dozens more launches

Maintenance requires 600 computer generated maintenance jobs 3-month turnaround More than 100 people

All activities involved in keeping a system’s equipment working

Objective: Maintain system capability & minimize total costs

© 1995 Corel Corp.

Maintenance ManagementMaintenance Management

The Strategic Importance of The Strategic Importance of Maintenance and ReliabilityMaintenance and Reliability

Failure has far reaching effects on a firm’s operation reputation profitability customers product employees profits

Maintenance Procedures

Employee Involvement

Maintenance PerformanceMaintenance Performance

© 1995 Corel Corp.

© 1995 Corel Corp.

Maintenance PerformanceMaintenance Performance

Good Maintenance & Reliability Good Maintenance & Reliability StrategyStrategy

Requires: Employee involvement Maintenance and reliability procedures

To yield: Reduced inventory Improved quality Improved capacity Reputation for quality Continuous improvement

Employee InvolvementEmployee Involvement

Information sharing Skill training Reward system Power sharing

© 1995 Corel Corp.

Maintenance & Reliability Maintenance & Reliability ProceduresProcedures

Clean and lubricate Monitor and adjust Minor repair Computerized records

Maintenance Procedures

© 1995 Corel Corp.

Lower operating

costs

Continuous improvement

Faster, more dependable throughput

Higher productivity

Improved quality

Improved capacity

Reduced inventory

Maintenance

Maintenance BenefitsMaintenance Benefits

Tactics forTactics for Reliability and Maintenance Reliability and Maintenance

Reliability Tactics improving individual components providing redundancy

Maintenance Tactics implementing preventive maintenance increasing repair capabilities

System Reliability -System Reliability - Components in Series Components in Series

Average Reliability of all Components (Percent)

Relia

bility

of t

he S

yste

m (P

erce

nt)

100

80

60

40

20

0

100 99 98 97 96

n=1

n=10

n=50

n=100

n=200

n=300n=400

Reliability ofReliability of Components in Series Components in Series

R = R1 * R2 * R3 * ...

Reliability Probability that an item will function for a given time

Mean time between failures (MTBF) Average time between failures of a repairable item

Failure rate Reciprocal of MTBF

Evaluating MaintenanceEvaluating Maintenance

Failure Rate (%)Failure Rate (%)

Number of failures FR(%) = * 100% Number of units tested

Lifetime Failure RatesLifetime Failure Rates

Infantmortality

andimproper use

failure

“normal” failure Wearoutfailure

Failurerate

Lifetime

Failures Per Operating HourFailures Per Operating Hour

Number of Failures FR(n) = Operating Time

Mean Time Between FailuresMean Time Between Failures

1 MTBF = FR(N)

Providing RedundancyProviding Redundancy

Probability of first

component working

Probability of second component working

+

Probability of needing second component

* = P(R)

How much preventive & breakdown maintenance Who performs maintenance

Centralized, decentralized, operator etc. Contract or in-house

When to replace or repair How much to replace

Individual or group replacement

Maintenance DecisionsMaintenance Decisions

Preventive Breakdown

Routine inspection & servicing

Prevents failures Bases for doing

Time: Every day Usage: Every 300 pieces Inspection: Control chart

deviations

Non-routine inspection & servicing

Remedial Basis for doing

Equipment failure

Types of MaintenanceTypes of Maintenance

Mean Time Between Failure and Mean Time Between Failure and Preventive MaintenancePreventive Maintenance

Frequencyof failure

Mean Time Between Failure

Candidate for preventivemaintenance will have

distribution with lowvariability

Centralized maintenance department Does all maintenance (PM & breakdown)

Decentralized maintenance department Useful if different equipment used in different areas of

company Contract maintenance

Used if little equipment or expertise Operator ownership approach

Organizing theOrganizing the Maintenance Function Maintenance Function

Operator does preventive maintenance Equipment condition is their responsibility Learns equipment better Increases worker’s pride Reduces repair time & PM costs

Maintenance department is backup Handles non-routine problems Provides maintenance training Has plant-wide responsibilities

Operator-Ownership ApproachOperator-Ownership Approach

A Computerized Maintenance SystemA Computerized Maintenance System

Maintenance Commitment

Cost

Preventive Maintenance CostTotTotal Maintenance Cost

Breakdown Cost

Optimal

Maintenance CostsMaintenance CostsTraditional ViewTraditional View

Maintenance CostsMaintenance CostsFull Cost ViewFull Cost View

Maintenance Commitment

Cost

Optimal

Total costs

Full cost of breakdowns

Preventive maintenance costs

Contract for Preventive Contract for Preventive MaintenanceMaintenance

Compute the expected number of breakdowns without the service contract

Compute the expected breakdown cost per month with no preventive maintenance contract

Compute the cost of preventive maintenance Compare the two options

Increasing Repair Capabilities:Features Increasing Repair Capabilities:Features of A Good Maintenance Facilityof A Good Maintenance Facility

Well-trained personnel Adequate resources Ability to establish a repair plan and priorities Ability and authority to do material planning Ability to identify the cause of breakdowns Ability to design ways to extend MTBF

Operations Manager Must Determine Operations Manager Must Determine How Maintenance Will be PerformedHow Maintenance Will be Performed

Operator Maintenance Department

Manufacturer’s field service

Depot Service (return equipment)

Competence is higher as we more to the rightPreventive maintenance costs

less and is faster as we move to the left

Total Productive MaintenanceTotal Productive Maintenance Additional requirements of:

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

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

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

Training workers to operate and maintain their own machines

A Key To SuccessA Key To Success

High utilization of facilities, tight scheduling, low inventory and consistent quality demand reliability - total preventive maintenance is the key to reliability.

Techniques for Establishing Techniques for Establishing Maintenance PoliciesMaintenance Policies

Simulation - enables one to evaluate the impact of various maintenance policies

Expert systems - can be used by staff to help diagnose faults in machinery and equipment