maintenance copyright © 2015 mcgraw-hill education. all rights reserved. no reproduction or...
TRANSCRIPT
Maintenance
Supplement 14
Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.
14S-2
Supplement 14: Learning Objectives
You should be able to:LO 14S.1 Explain the importance of maintenance in
production systemsLO 14S.2 Describe the range of maintenance activitiesLO 14S.3 Discuss preventive maintenance and the key
issues associated with itLO 14S.4 Explain breakdown maintenance and name
the key issues associated with itLO 14S.5 State how the Pareto phenomenon pertains to
maintenance decisions
14S-3
The goal of maintenance is to keep the production system in good working order at minimal cost
Reasons for wanting to keep equipment and machines in good operating condition:1. Avoid production or service disruptions2. Not add to production or service costs3. Maintain high quality4. Avoid missed delivery dates
Maintenance Goals
LO 14S.1
14S-4
1. Operations capacity is reduced, and orders are delayed
2. There is no output, but overhead continues, increasing the cost per unit
3. There are quality issues Output may be damaged
4. There are safety issues Employees or customers may be injured
Breakdown Consequences
LO 14S.1
14S-5
Reactive:Breakdown maintenance
Dealing with breakdowns or problems when they occur
Proactive:Preventive maintenance
Reducing breakdowns through a program of lubrication, adjustment, cleaning, inspection, and replacement of worn parts
Maintenance Options
LO 14S.2
14S-6
The goal of preventive maintenance is to reduce the incidence of breakdown or failures in the plant or equipment to avoid the associated costs Loss of output Idle workers Schedule disruption Injuries Damage to other equipment, products, or facilities Repairs
Inventories of spare parts Repair tools and equipment Repair specialists
Preventive Maintenance
LO 14S.3
14S-7
It is periodicIt can be scheduled according to the availability
of maintenance personnel and to avoid interference with operating schedules
Maintenance is scheduled using some combination of1. The result of planned inspections that reveal a need for
maintenance2. According to the calendar (passage of time)3. After a predetermined number of operating hours
Preventive Maintenance Schedule
LO 14S.3
14S-8
Preventive Maintenance: FrequencyThe goal is to strike a balance between the
cost of preventive maintenance and the cost of breakdown
The amount of preventive maintenance, therefore, is a function of the expected frequency of breakdown, the cost of breakdown, and the cost of preventive maintenance
LO 14S.3
14S-9
Frequency: Example 1 The frequency of breakdown of a machine per month is
$1,000 and the cost of preventive maintenance is $1,250 per month. If preventive maintenance is performed, the probability of a machine breakdown is negligible. Should the manager use preventive maintenance, or would it be cheaper to repair the machine when it breaks down?
Number of breakdowns 0 1 2 3
Frequency of occurrences .20 .30 .40 .10
LO 14S.3
14S-10
Frequency: Example 1
4.1)10(.3)40(.2)30(.1)20(.0breakdowns of
number Expected
Number of breakdowns 0 1 2 3
Frequency of occurrences .20 .30 .40 .10
$150
$1,250 - )1.4($1,000
emaintenancpreventive ofCost
breakdownofcost Expected
emaintenanc preventiveofbenefit Expected
LO 14S.3
14S-11
Suppose the average time before breakdown is normally distributed with a mean of 3 weeks and a standard deviation of .60 weeks. If breakdown cost averages $1,000 and preventive maintenance costs $250, what is the optimal maintenance interval?
Find the number of standard deviations from the mean represented by an area under the normal curve of .25
Using the standard normal table, it is -0.67Use this value to determine the maintenance interval
Frequency: Example 2
25.000,1$
250$
costBreakdown
cost Preventive
weeks2.598)(-.67)(.603deviation) (standard Mean z
LO 14S.3
14S-12
Predictive maintenance An attempt to determine when best to perform
preventive maintenance activitiesIdeally, preventive maintenance will be performed
just prior to a breakdown or failure because this will result in the longest possible use of facilities or equipment without a breakdown
Total productive maintenance JIT approach where workers perform preventive
maintenance on the machines they operate
Maintenance Approaches
LO 14S.3
14S-13
Approaches to dealing with breakdowns:Use of standby or backup equipmentInventories of spare parts are maintainedUse operators who are able to perform at least
minor repairs on the equipment they operateHave repair people who are well trained and
readily available to diagnose and correct problems
Breakdown Programs
LO 14S.4
14S-14
When breakdowns become frequent and/or costly:What is the cost of replacement compared to
continued maintenance?Issues:
Predicting breakdownsTechnological changeSystem disruptionsTraining employees on the use of new equipmentForecast of future demand
Replacement
LO 14S.4
14S-15
Breakdown programs are most effective when they take into account the degree of importance of a piece of equipment has in the operations system, and the ability of the system to do without it for a period of time.
The Pareto phenomenon exists in such situations: Few pieces of equipment will be extremely important to
the functioning of the systemThese justify considerable effort and/or expense
Some will require moderate effort and/or expense Many will justify minimal effort and/or expense
Pareto Phenomenon & Maintenance
LO 14S.5