14s-1 Maintenance

William J. Stevenson

Operations Management

8th edition

14s-2 Maintenance

CHAPTER14s

Maintenance

McGraw-Hill/IrwinOperations Management, Eighth Edition, by William J. StevensonCopyright © 2005 by The McGraw-Hill Companies, Inc. All rights

reserved.

14s-3 Maintenance

IntroductionIntroduction

Maintenance All activities that maintain facilities and equipment in

good working order so that a system can perform as intended

Breakdown maintenance Reactive approach; dealing with breakdowns or

problems when they occur Preventive maintenance

Proactive approach; reducing breakdowns through a program of lubrication, adjustment, cleaning, inspection, and replacement of worn parts

14s-4 Maintenance

Reasons for keeping equipment running Avoid production disruptions Not add to production costs Maintain high quality Avoid missed delivery dates

Maintenance ReasonsMaintenance Reasons

14s-5 Maintenance

Production capacity is reduced Orders are delayed

No production Overhead continues Cost per unit increases

Quality issues Product may be damaged

Safety issues Injury to employees Injury to customers

Breakdown ConsequencesBreakdown Consequences

14s-6 Maintenance

Total Maintenance CostTotal Maintenance Cost

Breakdown andrepair cost

Optimum Amount of preventive maintenance

Co

st

Total Cost

Preventivemaintenance cost

Table 14S.1

14s-7 Maintenance

Preventive maintenance: goal is to reduce the incidence of breakdowns or failures in the plant or equipment to avoid the associated costs

Preventive maintenance is periodic

Result of planned inspections

According to calendar

After predetermined number of hours

Preventive MaintenancePreventive Maintenance

14s-8 Maintenance

Frequency of breakdown

If the average cost of a breakdown is $1,000, and the cost of preventative maintenance is $1,250 per month, should we use preventive maintenance?

Example S-1Example S-1

Number of breakdowns 0 1 2 3Frequency of occurrence .20 .30 .40 .10

14s-9 Maintenance

Number ofBreakdowns

Frequency ofOccurrence

Expected number ofBreakdowns

0123

.20

.30

.40

.101.00

0.30.80.30

1.40

Expected cost to repair = 1.4 breakdowns per month X $1000 = $1400Expected cost to repair = 1.4 breakdowns per month X $1000 = $1400Preventive maintenance = $1250Preventive maintenance = $1250PM results in savings of $150 per monthPM results in savings of $150 per month

Example S-1 SolutionExample S-1 Solution

14s-10 Maintenance

Predictive MaintenancePredictive Maintenance

Predictive maintenance

An attempt to determine when best to perform preventive maintenance activities

Total productive maintenance

JIT approach where workers perform preventive maintenance on the machines they operate

14s-11 Maintenance

Breakdown ProgramsBreakdown Programs

Standby or backup equipment that can be quickly pressed into service

Inventories of spare parts that can be installed as needed

Operators who are able to perform minor repairs

Repair people who are well trained and readily available to diagnose and correct problems with equipment

14s-12 Maintenance

ReplacementReplacement

Trade-off decisions Cost of replacement vs cost of continued maintenance New equipment with new features vs maintenance Installation of new equipment may cause disruptions Training costs of employees on new equipment Forecasts for demand on equipment may require new

equipment capacity When is it time for replacement?