1/80
Equipment Efficiency:Availability, Performance
and MaintenanceOperations Analysis and Improvement
2010 Fall
Dr. Tai-Yue WangIndustrial and Information Management Department
National Cheng Kung University
2/80Dr. Tai-Yue Wang IIM Dept. NCKU
Presentation
The role of maintenance is to insure the survivability and proper functioning of all company hardware. Most maintenance departments are considered “a
necessary evil”. Investments required to improve production processes
usually take on a low priority.
3/80Dr. Tai-Yue Wang IIM Dept. NCKU
Presentation
Maintenance evolution, as well as maintenance technique evolution, has developed in parallel for many companies. Remediate hardware failures. Prevent future problems with the equipment. Incorporate basic maintenance tasks into their daily
production routine. Predicting equipment breakdowns.
4/80Dr. Tai-Yue Wang IIM Dept. NCKU
Introduction
Maintenance’s primary objective is to maintain, at a high operative level, the productive resources in order to assure their service at an expected cost.
Maintenance is the “machine’s medicine”. Determine the right moment to replace the
equipment. It may be better to simply unplug it.
5/80Dr. Tai-Yue Wang IIM Dept. NCKU
Introduction Elements that need maintenance.
Machines and tools. Facilities (compressed air, heating,
…) Buildings (walls, illumination,…) Information and transportation
systems.
20
1612119
7
14 5
4
8
15131019
18
17
6
1
2 3
Thinkingrevolution
The 5S
Standardoperations
One-Pieceflow
Poka-Yoke Jidoka
TPM
JUST IN TIME
Work
forc
e o
ptim
izatio
n
Vis
ual C
on
trol
LevelingProductionKanban
Multi-functionalworkers
SMED
6/80Dr. Tai-Yue Wang IIM Dept. NCKU
Introduction Some companies subcontract
maintenance. Is contemplated in both the
Just-in-time and the 20 keys (key number 9) for lean. Improves the availability and
performance rates of the equipment.
20
1612119
7
14 5
4
8
15131019
18
17
6
1
2 3
Thinkingrevolution
The 5S
Standardoperations
One-Pieceflow
Poka-Yoke Jidoka
TPM
JUST IN TIME
Work
forc
e o
ptim
izatio
n
Vis
ual C
on
trol
LevelingProductionKanban
Multi-functionalworkers
SMED
7/80Dr. Tai-Yue Wang IIM Dept. NCKU
Types of maintenance Corrective -> All industrial equipment is
exposed to transitory (wear) or definitive breakdowns (catastrophic failure). Affecting its functionality and performance. Can represent high costs for enterprises.
Preventive -> The maintenance mission cannot only be repairing the breakdowns. They should be able to get ahead of the breakdowns.
8/80Dr. Tai-Yue Wang IIM Dept. NCKU
Corrective maintenance Also called breakdown maintenance.
Up to the 1950s it was virtually the only maintenance.
Machine stoppages hardly affected productive time. Repairs were carried out in an effective way.
Equipmentperformance Substitution
Repair
Time until failure
Repair time
Time
9/80Dr. Tai-Yue Wang IIM Dept. NCKU
Types of corrective maintenance
Urgent repairs. Reestablishing the equipment into service. Repair is carried out is temperally. The remainder of the tasks will/can be
scheduled for a future time.
10/80Dr. Tai-Yue Wang IIM Dept. NCKU
Types of corrective maintenance
Scheduled corrective. Appears as a result of urgent repairs.
Determine an appropriate time to repair the machine completely.
After repairing the damaged component As good as new. At least as it was before.
11/80Dr. Tai-Yue Wang IIM Dept. NCKU
Repair problems
Repair tasks are performed quickly and under pressure, which can cause future problems.
Repair time can be very high because replacement part(s) may have to be ordered from a supplier.
12/80Dr. Tai-Yue Wang IIM Dept. NCKU
Repair problems Accidents can take place because of poor maintenance
safety measures. Corrective maintenance policy implies higher labor
costs. This policy can be justified in some cases.
Equipment with a frequent replacement policy. Like personal office computers.
When breakdown costs are small. Light bulbs fail.
13/80Dr. Tai-Yue Wang IIM Dept. NCKU
Types of preventive maintenance
The preventive maintenance has two variants. Systematic preventive maintenance. Conditional preventive maintenance or predictive
maintenance.
14/80Dr. Tai-Yue Wang IIM Dept. NCKU
Systematic preventive maintenance
1960s -> the General Electric Corporation systematized a new type of maintenance called planned maintenance.
Equipmentperformance
Substitution
Theoretical time until failure
Intervention duration
Time
Equipmentperformance Substitution
Repair
Time until failure
Repair time
Time
15/80Dr. Tai-Yue Wang IIM Dept. NCKU
Systematic preventive maintenance
Planned maintenance arrived to Japan. The bases of this systematic
preventive maintenance process were established.
Systematic substitution of some machine components.
Equipmentperformance
Substitution
Theoretical time until failure
Intervention duration
Time
Equipmentperformance Substitution
Repair
Time until failure
Repair time
Time
16/80Dr. Tai-Yue Wang IIM Dept. NCKU
Systematic preventive maintenance
Applied to general wear or use components. Know with precision the
component’s performance characteristics.
Equipmentperformance
Substitution
Theoretical time until failure
Intervention duration
Time
Equipmentperformance Substitution
Repair
Time until failure
Repair time
Time
17/80Dr. Tai-Yue Wang IIM Dept. NCKU
Systematic preventive maintenance
Replacement policy might call for a component to be replaced every week or in other ways such as, every 300 working hours or every 1000 parts produced. Equipment
performanceSubstitution
Theoretical time until failure
Intervention duration
Time
18/80Dr. Tai-Yue Wang IIM Dept. NCKU
Conditional preventive maintenance
Also called predictive maintenance.
Systematic preventive maintenance can become very expensive.
Equipmentperformance
Substitution
Theoretical time until failure
Intervention duration
Time
Inspections
Equipmentperformance
Substitution
Theoretical time until failure
Intervention duration
Time
19/80Dr. Tai-Yue Wang IIM Dept. NCKU
Conditional preventive maintenance
Conditional preventive maintenance is used to change components depending on their current state. The useful life for costly
components can be extended. This type of maintenance best
fits components where performance can be monitored.
Equipmentperformance
Substitution
Theoretical time until failure
Intervention duration
Time
Inspections
Equipmentperformance
Substitution
Theoretical time until failure
Intervention duration
Time
20/80Dr. Tai-Yue Wang IIM Dept. NCKU
Conditional preventive maintenance
ISO 14000 (environmental norm) requires that industry avoid systematic preventive maintenance when working with environmentally harmful products.
Equipmentperformance
Substitution
Theoretical time until failure
Intervention duration
Time
Inspections
Equipmentperformance
Substitution
Theoretical time until failure
Intervention duration
Time
21/80Dr. Tai-Yue Wang IIM Dept. NCKU
Conditional preventive maintenance
Predictive maintenance. Look for correlations between
multiple parameters and the degradation of a component.
Temperature (thermocouples), Noises (phonometer). Cracks (X-rays machine). Pressure losses (manometer).
QS9000 recommends predictive maintenance.
Equipmentperformance
Substitution
Theoretical time until failure
Intervention duration
Time
Inspections
Equipmentperformance
Substitution
Theoretical time until failure
Intervention duration
Time
22/80Dr. Tai-Yue Wang IIM Dept. NCKU
Maintenance program implementation
Almost all machines follow a similar lifecycle. Hidden small defects.
Difficult to detect and to observe -> It does not interfere with functionality.
Increase of friction in an axle.
Apparent small defects. Are more noticeable -> They are normally not
repaired. Small vibrations on a machine.
23/80Dr. Tai-Yue Wang IIM Dept. NCKU
Maintenance program implementation
Execution under expectations. The defects affect the equipment productivity. the standards of quality will be violated.
24/80Dr. Tai-Yue Wang IIM Dept. NCKU
Maintenance program implementation
Almost all machines follow a similar lifecycle. Intermittent stops.
The machine intermittently produces defect parts. Small repairs are performed.
Stops and breakdowns. Breakdowns are frequent.
Production equipment may not be as new as we would like them to be. “Stops and breakdown” stage.
25/80Dr. Tai-Yue Wang IIM Dept. NCKU
Maintenance program implementation
Production equipment typically becomes more sophisticated/complex. More expensive every year. It has greater economic impact.
Repairs should be done at a faster rate.
Working shifts can also represent an obstacle for maintenance interventions. Limits possible maintenance tasks and scheduling.
26/80Dr. Tai-Yue Wang IIM Dept. NCKU
Maintenance program implementation
The objective of maintenance is to efficiently oversee equipment throughout the equipment life cycle. Cover the entire lifecycle
Implementing an effective corrective maintenance. Preventive maintenance tasks. Implementing predictive maintenance strategies.
27/80Dr. Tai-Yue Wang IIM Dept. NCKU
Getting started
Become familiar with the resources that will require maintenance. Each maintained resource should be coded (resource
id#). Code the types of breakdowns and maintenance
tasks. In a historical data study -> Group failure causes.
28/80Dr. Tai-Yue Wang IIM Dept. NCKU
Getting started
Maintenance should have the following two documents. Facility Inventory.
Lists all equipments and their principle characteristics. Code, record number, equipment type,…
Equipment History Files. Data given by the equipment manufacturer. Information about the location in the plant. Types of spare parts needed. …
29/80Dr. Tai-Yue Wang IIM Dept. NCKU
Corrective maintenance implementation
Organize, in an effective way, the corrective maintenance procedures and actions. Breakdown occurs -> Fill out a breakdown work
order. If the worker can solve it -> fill a report. If not -> the work order will be sent to the maintenance
department. Work request order will be issued. Maintenance workers will either repair the machine immediately
or will schedule the repair. The repair can be provisional or definitive.
30/80Dr. Tai-Yue Wang IIM Dept. NCKU
Scheduled corrective maintenance
Variability in the corrective maintenance tasks duration can be problematic. Corrective orders and flow diagrams for repetitive repairs
must be developed. Materials and spare parts that should be utilized.
Maintenance workers’ tasks do not end with the equipment repair. They should gather all the breakdown information. Describe the process that was performed.
31/80Dr. Tai-Yue Wang IIM Dept. NCKU
Scheduled corrective maintenance
Each machine should have its own file with breakdown records. Analyze breakdown causes. Anticipate future problems. This file must be upgraded with each maintenance
intervention.
32/80Dr. Tai-Yue Wang IIM Dept. NCKU
Scheduled corrective maintenance
Corrective maintenance tasks do not only consist on changing the broken or malfunctioning components. Study the causes and the frequency of the
breakdowns.
33/80Dr. Tai-Yue Wang IIM Dept. NCKU
Preventive maintenance implementation
Avoid a breakdown of any resource, while keeping maintenance cost as low as possible.
Two types of actions. Inspections.
Observe and detect possible anomalies. Frequent checkups that follow a specific inspection plan.
Revisions. Scheduled equipment stops.
Systematic substitution of several machine components. Carried out during the weekend.
34/80Dr. Tai-Yue Wang IIM Dept. NCKU
Preventive maintenance implementation
Preventive maintenance tasks’ scheduling is mandatory in the ISO norms.
35/80Dr. Tai-Yue Wang IIM Dept. NCKU
Preventive maintenance implementation
These tasks can be planned daily, weekly, monthly or even annually. Scheduled at times when they do not affect the
factory’s production plan. Daily working problems force us to continuously
reschedule these tasks.
36/80Dr. Tai-Yue Wang IIM Dept. NCKU
Preventive maintenance implementation
Equipment preventive maintenance tasks are also called PM orders. Each PM order should be based on a study of the
equipment breakdown causes. FMEA tool described at the tools section.
37/80Dr. Tai-Yue Wang IIM Dept. NCKU
Autonomous maintenance
PM orders carried out by the production workers. Known as user maintenance orders.
They should be simple and graphically represented. Many inspection tasks should be carried out every
day.
38/80Dr. Tai-Yue Wang IIM Dept. NCKU
Autonomous maintenance
Significant amount of notices that could be easily handled by the production worker. It takes more time to fill out the request order than to
fix the problem
39/80Dr. Tai-Yue Wang IIM Dept. NCKU
Autonomous maintenance
Autonomous maintenance includes these small tasks and three daily preventive measures. Cleaning, lubricating and checking.
40/80Dr. Tai-Yue Wang IIM Dept. NCKU
Autonomous maintenance. Safety
Safety is one of the most important restrictions. Autonomous tasks apply only for simple repair
operations. Repair or maintenance should never be
performed if the knowledge required to fix the machine is high.
41/80Dr. Tai-Yue Wang IIM Dept. NCKU
Autonomous maintenance. Safety
It can be very challenging to convince production workers about the importance of maintenance tasks. They do not consider their responsibility.
42/80Dr. Tai-Yue Wang IIM Dept. NCKU
Autonomous maintenance
Autonomous maintenance implementation process has a specific methodology.
Initial cleaning1
Countermeasures to Sources of Contamination
2
Cleaning and Lubricating Standards
3
Overall inspections4
Autonomous Maintenance Standards5
Process Quality Assurance6
Autonomous Supervision7
43/80Dr. Tai-Yue Wang IIM Dept. NCKU
TPM - Total Productive Maintenance
In the 1970s, Nakajima developed in Japan TPM. New maintenance management philosophy.
English translation was not published until 1988. JIPM – Japanese Institute of Plants Maintenance.
Grants the PM prize to the TPM top excellent companies. 60% of the winning companies during the first 17 years are now part
of the Toyota Group or suppliers of this Group.
44/80Dr. Tai-Yue Wang IIM Dept. NCKU
TPM - Total Productive Maintenance
Nakajima combined preventive maintenance theories with the total quality concept. Nakajima developed the Overall Equipment
Efficiency ratio.
45/80Dr. Tai-Yue Wang IIM Dept. NCKU
TPM keys
Maximize the Overall Equipment Efficiency. Eliminating the six big losses.
Autonomous maintenance implementation. In order to terminate the “I operate, you repair”
mind set. Preventive engineering.
Improving the equipments’ maintainability.
46/80Dr. Tai-Yue Wang IIM Dept. NCKU
TPM keys
Training workers for maintenance improvements. Propose methods for increasing the equipment
availability. Initial equipment management. The objective of the TPM -> Zero Breakdowns.
Utilize tools such as the P-M analysis -> Explained in tools section.
47/80Dr. Tai-Yue Wang IIM Dept. NCKU
RCM - Reliability Centered Maintenance
RCM was created in the United States in the 1960s, to optimize the reliability of aeronautical equipment. RCM was not utilized in nuclear power stations
until the 1980s. Recently has been implemented in the industrial
world.
48/80Dr. Tai-Yue Wang IIM Dept. NCKU
RCM - Reliability Centered Maintenance
Needs a complete maintenance and breakdown record for each item of equipment. RCM objective is to determine the maintenance
tasks that are more effective for the critical components.
FMEA, reliability analysis, statistical techniques. It is necessary to have a preventive maintenance
program implemented and running properly.
49/80Dr. Tai-Yue Wang IIM Dept. NCKU
FMEA for equipment
All defects have a root cause, and to eliminate future defects an action must be carried out. Defect -> Gap between two elements Cause -> Lack of lubrication or a loose fastener. Action -> Grease or tighten the lose element.
50/80Dr. Tai-Yue Wang IIM Dept. NCKU
FMEA for equipment
To determine a good preventive maintenance plan, all the possible breakdowns, their causes and their corrective actions must be analyzed. The main tool to carry out this type of analysis is the
FMEA for equipment (Failure Mode and Effects Analysis).
Is a guide to analyze, in an organized manner, causes of possible equipment breakdowns.
A group of workers is gathered to study the problems and failures
51/80Dr. Tai-Yue Wang IIM Dept. NCKU
EQUIPMENT CARRIED OUT BY DATE
PAGE OF
Equipmentfunctions Failure modes Faiulre efects Failure causes
Actualcontrols
Recommendedactions Responsible
FMEA for equipment
52/80Dr. Tai-Yue Wang IIM Dept. NCKU
FMEA for equipment
Equipment functions. The functions that the equipment carries out.
Provides compressed air during specific conditions.
Failure modes. All the possible ways that the equipment can be
forced to stop. Breaks, blockage, leaks, etc.
EQUIPMENT CARRIED OUT BY DATE
PAGE OF
Equipmentfunctions Failure modes Faiulre efects Failure causes
Actualcontrols
Recommendedactions Responsible
53/80Dr. Tai-Yue Wang IIM Dept. NCKU
FMEA for equipment
Failure effects. All possible consequences of each failure are
analyzed in detail. Severity (S).
1 being not very serious. 4 very serious or 10.
EQUIPMENT CARRIED OUT BY DATE
PAGE OF
Equipmentfunctions Failure modes Faiulre efects Failure causes
Actualcontrols
Recommendedactions Responsible
54/80Dr. Tai-Yue Wang IIM Dept. NCKU
FMEA for equipment
Failure causes. The origin of the failure is analyzed. Identify the anomaly that can lead to the failure.
Probability (P). 1 not very frequent. 4 very frequent or 10.
EQUIPMENT CARRIED OUT BY DATE
PAGE OF
Equipmentfunctions Failure modes Faiulre efects Failure causes
Actualcontrols
Recommendedactions Responsible
55/80Dr. Tai-Yue Wang IIM Dept. NCKU
FMEA for equipment
Actual controls. If, at the present time, some kind of control is carried
out. Detection (D)
1 if the control does not always detect the cause 4 if it always detects or 10.
EQUIPMENT CARRIED OUT BY DATE
PAGE OF
Equipmentfunctions Failure modes Faiulre efects Failure causes
Actualcontrols
Recommendedactions Responsible
56/80Dr. Tai-Yue Wang IIM Dept. NCKU
FMEA for equipment
After the first part of the FMEA table has been completed, the Risk Priority Number (RPN) is calculated. The product of the three quantified variables (S,
P and D). Ranking failures by RPN.
Analyze the causes that do not represent any threat. Special attention must be paid to those effects that
have been considered critical.
57/80Dr. Tai-Yue Wang IIM Dept. NCKU
FMEA for equipment
The chosen plan of action and the employee responsible for carrying out this plan are registered in the same table utilized in the FMEA. After a FMEA application arises, the necessity
of developing a preventive maintenance plan is recommended.
58/80Dr. Tai-Yue Wang IIM Dept. NCKU
FMEA for equipment
Preventive maintenance intervention periods (T). Know the component damage/wear behavior
curve. Breakdowns and the time when the breakdowns
occurred -> Mean Time Between Failures (MTBF). T is based on the corrective percentage that the
company would like to support (K).
Equipmentperformance
Substitution
MTBF
MTTR
Time
T = K·MTBF
59/80Dr. Tai-Yue Wang IIM Dept. NCKU
Reliability
Reliability is defined as the probability that an equipment will work satisfactorily, during a certain period of time under some specific working conditions.
Reliability is a probability. Relative frequency of breakdowns.
60/80Dr. Tai-Yue Wang IIM Dept. NCKU
Reliability
All production equipment should work satisfactorily. Failure can be triggered by an abrupt change in the
component characteristic or by progressive damage. Work satisfactorily for a specific period of time.
Maintain quality standards during a reasonable period of time.
RELIABILITY = QUALITY + TIME
61/80Dr. Tai-Yue Wang IIM Dept. NCKU
Reliability
The component life or equipment life duration depends on working conditions. Environmental (temperature or humidity). Operational (continuous starts and stops,
electrical strain).
62/80Dr. Tai-Yue Wang IIM Dept. NCKU
Reliability
The system state depends on the primary group of elements that makes it work properly. Each element has a random lifetime.
Estimate the lifetime of the components.
Reliability -> MBTF (Mean Time Between Failure)
failuresof Number time Operating
MTBF
63/80Dr. Tai-Yue Wang IIM Dept. NCKU
Reliability and Maintainability
Maintainability -> probability that it must be repaired in a predetermined time following a specific repair procedure.
failuresof Number time total Failures
MTTR
64/80Dr. Tai-Yue Wang IIM Dept. NCKU
Reliability and Maintainability
Maintainability depends on different factors. Machine factors.
Accessibility or interchangeability among components. Organizational factors.
Maintenance staff knowledge, documentation availability,… Operative factors.
Ability of the manpower.
Is quantified through the MTTR (Mean Time To Recovery).
failuresof Number time total Failures
MTTR
65/80Dr. Tai-Yue Wang IIM Dept. NCKU
Reliability and Statistical availability
Average between the middle time used in the equipment and the required production time
If the different times between breakdowns as well as each repair duration time are graphically represented this process.
tTBF1 TBF2 TBF3
TR1 TR2 TR3
MTTR MTBFMTBF
ty availabili lstatistica
66/80Dr. Tai-Yue Wang IIM Dept. NCKU
Reliability - the Bathtub curve
Is a graphic representation of the failure rate (t). Probability that an element fails depending on its
life use stage or status. ZONE I. Infant period. ZONE II. Useful period. ZONE III. Waste period.
time
(t)
ZONEI
ZONEII
ZONEIII
67/80Dr. Tai-Yue Wang IIM Dept. NCKU
Reliability – The bathtub curve: Zone I
Equipment set up and debug process. Goes downhill because, as time moves
forward, the probability of a component failure decreases.
The problems in this area can be avoided by making intensive tests or by exchanging troublemaker elements at an early stage adjustment period.
time
(t)
ZONEI
ZONEII
ZONEIII
68/80Dr. Tai-Yue Wang IIM Dept. NCKU
Reliability – The bathtub curve: Zone II
Zone II. Failures randomly appear. Electronic systems.
The curve formed is virtually horizontal.
In mechanical systems. The curve normally has a slightly
positive slope.
time
(t)
ZONEI
ZONEII
ZONEIII
time
(t)
ZONEI
ZONEII
ZONEIII
69/80Dr. Tai-Yue Wang IIM Dept. NCKU
Reliability – The bathtub curve: Zone III
Zone III. Failures come from components far
more quickly. Critical components replacement is
strongly recommended.
time
(t)
ZONEI
ZONEII
ZONEIII
time
(t)
ZONEI
ZONEII
ZONEIII
70/80Dr. Tai-Yue Wang IIM Dept. NCKU
P-M Analysis
Defects reasons. Sporadic(零星 ) losses. Chronic(慢性 ) losses.
Sporadic losses can be corrected using tools already studied.
Defects
Time
sporadic losses
zero losses
chronic losses
71/80Dr. Tai-Yue Wang IIM Dept. NCKU
P-M Analysis
The P-M analysis is responsible for eliminating chronic losses. Considered “natural” according to their root sources. P - > Phenomenon. M - > Mechanism.
Defects
Time
sporadic losses
zero losses
chronic losses
72/80Dr. Tai-Yue Wang IIM Dept. NCKU
P-M Analysis
Reliability that has been studied has two aspects to consider. Intrinsic reliability.
Due to the design and production of the component. Operative reliability.
Due to the component use and the maintenance process.
Defects
Time
sporadic losses
zero losses
chronic losses
73/80Dr. Tai-Yue Wang IIM Dept. NCKU
P-M Analysis
P-M analysis should be applied after conventional improvement.
Six sigma is also suitable to carry out this type of study.
Defects
Time
sporadic losses
zero losses
chronic losses
74/80Dr. Tai-Yue Wang IIM Dept. NCKU
Maintenance management
A maintenance department should properly manage and control their costs.
Unlimited number of indicators that can be used for maintenance department performance. Manpower performance, hours dedicated to urgent
work, repair cost, availability,...
75/80Dr. Tai-Yue Wang IIM Dept. NCKU
Maintenance management
Maintenance management is a difficult task because it frequently does not have management’s support. As long as the maintenance department does not
exceed its assigned budget, no one pays much attention to the maintenance department activities or expenses.
76/80Dr. Tai-Yue Wang IIM Dept. NCKU
Maintenance costs
Using economic terms, maintenance management helps to control deviations in the firm’s budget and also to determine investment needs to reduce the costs.
77/80Dr. Tai-Yue Wang IIM Dept. NCKU
Maintenance costs
There are two alternatives or opposing costs. Non-maintenance costs.
Opportunity costs, quality costs, production manpower cost, etc.
Maintenance costs. Breakdown prevention costs, anomalies detection cost,
inspection resources costs, etc.
78/80Dr. Tai-Yue Wang IIM Dept. NCKU
Maintenance costs
(1) -> Maintenance investment increases the equipment availability and at the same time
(2) -> An increase of the availability, supposes large investments.
Cost
Availability
Non-maintenancecosts
Maintenance costs
Total costs
0 % 100 %
21
79/80Dr. Tai-Yue Wang IIM Dept. NCKU
Summary
This chapter has provided an overview of maintenance activities, a critical aspect of Lean Manufacturing. Maintenance planning and monitoring activities are critical factors for Lean Enterprise efficiency.
80/80Dr. Tai-Yue Wang IIM Dept. NCKU
Summary
Unfortunately, maintenance is normally perceived as a necessary evil, and is not always seen as a critical engineering activity. This chapter has outlined some of the maintenance policies and procedures that can be used to obtain the goal for any production system: operate as efficient as possible at the lowest cost.