Operations management by stevenson 9th ch15s

15S

Maintenance

McGraw-Hill/Irwin

Copyright © 2007 by The McGraw-Hill Companies, Inc. All


Learning Objectives
 Explain the importance of maintenance in
production systems
 Describe the range of maintenance activities
 Discuss preventative maintenance and the
key issues associated with it
 Discuss breakdown maintenance and the
key issues associated with it
 State how the Pareto phenomenon pertains
to maintenance decisions
15S-2


Introduction
 Maintenance
 All activities that maintain facilities and
equipment in good working order so
that a system can perform as intended

 Two basic categories
 Building and grounds
 Equipment maintenance

15S-3


Goal of Maintenance
 To keep production systems in good working
order at minimal cost
 Reasons for maintenance





To avoid production or service disruptions
To not add production or service costs
To maintain high quality
To avoid missed delivery dates

15S-4


Breakdown Consequences





Operations capacity reduced
No output, but overhead continues
Quality issues – output may be damaged

Safety issues – employees or customers
may be injured

15S-5


Reactive vs Proactive
Reactive Maintenance:
 Breakdown maintenance
 Reactive approach; dealing with breakdowns or
problems when they occur

Proactive Maintenance:
 Preventive maintenance
 Proactive approach; reducing breakdowns
through a program of lubrication, adjustment,
cleaning, inspection, and replacement of worn
parts
15S-6


Maintenance Reasons
 Reasons for keeping equipment running





Avoid production disruptions
Not add to production costs

Maintain high quality
Avoid missed delivery dates

15S-7


Breakdown Consequences
 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
15S-8


Total Maintenance Cost
Table 14S.1

Cost

Total Cost

Preventive
maintenance cost

Breakdown and
repair cost
Optimum Amount of
preventive maintenance
15S-9


Preventive 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
15S-10


Example S-1
Frequency of breakdown
Number of breakdowns
Frequency of occurrence

0
1
2

3
.20 .30 .40 .10

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?
15S-11


Example S-1 Solution
Number of
Breakdowns
0
1
2
3

Frequency of
Occurrence
.20
.30
.40
.10
1.00

Expected number of
Breakdowns
0
.30

.80
.30
1.40

Expected cost to repair = 1.4 breakdowns per month X $1000 = $1400
Preventive maintenance = $1250
PM results in savings of $150 per month
15S-12


Predictive 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

15S-13


Breakdown 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
15S-14


Replacement
 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?
15S-15