8

MAINTENANCE MANAGEMENT
CHAPTER OUTLINE
8.1 Introduction and Meaning 8.6 Maintenance Schedule Techniques
8.2 Objectives of Maintenance 8.7 Total Productive Maintenance (TPM)
8.3 Types of Maintenance Exercises
8.4 Maintenance Planning Skill Development
8.5 Maintenance Scheduling

8.1 INTRODUCTION AND MEANING

Past and current maintenance practices in both the private and Government sectors would imply
that maintenance is the actions associated with equipment repair after it is broken. The dictionary
defines maintenance as the work of keeping something in proper condition, upkeep." This would
imply that maintenance should be actions taken to prevent a device or component from failing
or to repair normal equipment degradation experienced with the operation of the device to keep
itin proper working order. Data obtained in many studies over the past decade indicates that most
private and Government facilities do not expend the necessary resources to maintain equipment
in proper working order. They wait for equipment failure to occur and then take whatever actions
are necessary to repair or replace the equipment. Nothing lasts forever and all equipment has
associated with it some predefined life expectancy or operational life.
8.2 OBJECTIVES OF MAINTENANCE
Equipments are an important resource which is constantly used for adding value to products. So,
downtime and
It must be kept at the best operating condition. Otherwise, there will be excessive
equipments
also interruption of productionif it is used in a mass production line. Poor working of
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willleadto quality related problems. Hence, it is an absolute necessity to maintain the equipments
in good operating conditions with economical cost. Hence, we need an integrated approach to
minimize the cost of maintenance. In certain cases, the equipment will be obsolete over a period
of time. If a firm wants to be in the same business competitively, it has to take decision on
whether to replace the equipment or to retain the old equipment by taking the cost of maintenance
and operation into account.

8.3 TYPES OF MAINTENANCE

The design life of most equipment requires periodic maintenance. Belts need adjustment, alignment
needs io be maintained, proper lubrication on rotating equipment is required, and so on. In some
cases, certain components need replacement, e.g., a wheel bearing on amotor vehicle, to ensure
the main piece of equipment (in this case a car) last for its design life. Different approaches have
been developed to know how maintenance can be performed to ensure equipment reaches or
exceeds its design life. In addition to waiting for a piece of equipment to fail (reactive maintenance)
the other approaches are preventive maintenance, predictive maintenance, or reliability centered
maintenance.

8.3.1 Breakdown (Reactive) Maintenance

Breakdown maintenance is basically the 'run it till it breaks' maintenance mode. No actions
or efforts are taken to maintain the equipment as the designer originally intended to ensure
design life is reached. Studies as recent indicate that, this is still the predominant mode of
maintenance.
Advantages to breakdown maintenance can be viewed as a double-edged sword. If we are
dealing with new equipment, we can expect minimal incidents of failure. If our maintenance
program is purely reactive, we will not expend manpower or incur capital cost until something
breaks. Since we do not see any associated maintenance cost, we could view this period as
saving money. In reality, during the time we believe we are saving maintenance and capital cost,
we are really spending more money than we would have under a different maintenance approach.
We are spending more money associated with capital cost because, while waiting for the equipment
to break, we are shortening the life of the equipment resulting in more frequent
replacement. We
may incur cost upon failure of the primary device associated with its failure causing the failure
of a secondary device. This is an increased cost we would not have
experienced if our maintenance
program was more proactive.
Our labour cost associated with repair will probably be higher than
failure will most likely require more extensive repairs than would have been normal because the
of equipment had not been run to failure. Chances are the piece of required if the piece
hours or close to the end of the normal workday. If it is a critical equipment willfail during of
to be back on-line quickly, we will have to pay piece of equipment that needs
run equipment to
maintenance overtime cost. Since we expect to
failure, we will require a large material inventory of repair parts. This is a
we could minimize under a different cost
maintenance strategy.
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Advantages
1 Involves low cost investment for
maintenance.
2. Less staff is required.
Disadvantages
1 Increased cost due to
unplanned downtime of equipment.
2 Increased labour cost, especially if
overtime is needed.
3 Cost involved with repair or replacement of equipment.
4. Possible sccondary cquipment or
process damage from equipment failure.
5. Inefficient use of staff resources.

8.3.2 Preventive Maintenance

Preventive maintenance can he defined as, "Actions performed on atime or
schedule that detect, preclude, or mitigate degradation of a machine-run-based
component or system with the aim of
sustaining or extending its useful life through controlling degradation to an acceptable
Preventive maintenance is a means to increase the reliability of their level."
expending the necessary resources to conduct maintenance activities intended equipment. By simply
by the equipment
designer, equipment life is extended and its reliability is increased. In addition to an increase in
reliability, lot of amount will be saved over that of a program just using reactive maintenance.
Studies indicate that this savings can amount to as much as 12% to 18% on the average.
Advantages
1. Cost effective in many capital intensive processes.
2. Flexibility allows for the adjustment of maintenance periodicity.
3. Increased component life cycle.
4. Energy savings.
5. Reduced equipment or process failure.
6. Estimated 12% to 18% cost savings over reactive maintenance program.

Disadvantages
1. Catastrophic failures still likely to occur.
2. Labour intensive.
3. Includes performance of unneeded maintenance.
4. Potential for incidental damage to components in conducting unneeded maintenance.
Depending on the facilities current maintenance practices, present equipment reliability, and
facility downtime, there is little doubt that many facilities purely reliant on reactive maintenance
could save much more than 18% by instituting a proper preventive maintenance program.
While preventive maintenance is not the optimum maintenance program, it does have several
advantages over that of a purely reactive program. By performing the preventive maintenance
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as the equipment designer envisioned, we will extend the life of the equipment closer to design
This translates into dollar savings. Preventive maintenance (lubrication, filter change, etc.) will
generally run the cquipment more efficiently resulting in dollar savings. While we will not prevent
equipment catastrophic failures, we will decrease the number of failures. Minimizing failures
translate into maintenance and capital cost savings.
8.3.3 Predictive Maintenance
Predictive maintenance can be defined as "Measurements that detect the onset of a degradation
mechanism, thereby allowing causal stressors to be eliminated or controlled prior to any significant
deterioration in the component physical state. Results indicate current and future functional
capability":.
Basically,predictive maintenance differs from preventive maintenance by basing maintenance
need on the actual condition of the machine rather than on some preset schedule. Preventive
maintenance is time-based. Activities such as changing lubricant are based on time, like calendar
time or equipment run time.For example, most people change the oil in their vehicles every 3,000
to 5,000miles travelled. This is effectively basing the oil change needs on equipment run time.
No concern is given to the actual condition and performance capability of the oil. It is changed
because it is time. This methodology would be analogous to a preventive maintenance task. If.
onthe other hand, the operator of thecar discounted the vehicle run time and had the oil analyzed
at some periodicity to determine its actual condition and lubrication properties, he may be able
to extend the oil change until the vehicle had travelled 10,000 miles. This is the fundamental
difference between predictive maintenance and preventive maintenance, whereby predictive
maintenance is used to define needed maintenance task based on quantified material/equipment
condition.
There are many advantages of predictive maintenance. A well-orchestrated predictive
maintenance progran will eliminate catastrophic equipment failures. Schedule of maintenance
activities can be made to minimize or delete overtime cost. It is possible to minimize inventory
and order parts, as required, well ahead of time to support the downstream maintenance needs
and optimize the operation of the equipment, saving energy cost and increasing plant reliability.
Past studies have estimated that a properly functioning predictive maintenance program cm
provide asavings of 8% to12% over aprogram utilizing preventive maintenance alone. Depending
on afacility's reliance on reactive maintenance and material condition, it could easily recognize
savingsopportunities exceeding 30% to 40%. Independent surveys indicate the following industrial
average savings resultant from initiation of a functional predictive maintenance program:
1. Return on investment-10 times
2. Reduction in maintenance costs-25% to 30%
3. Elimination of breakdowns-70% to 75%
4. Reduction in downtime-35% to 45%
5. Increase in
production-20% to 25%.
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Advantages
1. Increasedcomponent operational lifelavailability
2. Allows for pre-emptive corrective actions.
3. Decrease in equipment or process downtime.
4. Decrease in costs for parts and labour.
5. Better product quality.
6. Improved worker and environmental safety.
7. Improved worker moral.
8. Energy savings.
9 Estimated 8% to 12% cost savings over preventive
maintenance prograrm.
Disadvantages
1. Increased investment in diagnostic equipment.
2. Increased investment in staff training.
3. Savings potential not readily seen by management.
Concept of Reliability in Maintenance
Reliability is the probability of survival under a given operating environment. For exampie. the
time between consecutive failures of a refrigerator where continuous working is required is a
measure of its reliability. If this time is more, the product is said to have high reliability
In a textile mill, generally the light is maintained at a minimum specified level. To achieve
this, let us assume that there are 100bulbs in use and the guaranteed life time of these buibs
is 5000 hours. If we collect statistics about the number of bulbs survived till 5000 nours, we can
compute the reliability of the bulbs. In this case,
Number of bulbs survived till the specified time limit
Reliability = Failurerate = Number of bulbs used
rehabiity is
If the number of bulbs survived till 5000 hours is 80, then we can say that the
0.8 (i.e., 80/100)
The reliability of railwaysignalling system, aircraft, and power plant are some of the interesang
a tailure will lead to heavy
examples for demonstrating the reliability concept. In these cases,
penalty.
Generally, prvttsequipmens
The concept of reliabilitycan be matched with systems conwept.
serial relationship or purllel relationship. So.
WIll have many components which may function with reliability of the prduct. Hee, cRugh attenion
the individual component's reliability affects the
produc's eliability is maxnized. The 0st of
must be given at the design, stage such that the whilemprovng it.
maintenance is also to be considered along with the reliability
pattern of any product is given in Fig. 8.. This is called bath-tub cuve
Ihe general failure failures in the carly period. This is mainly due to hOn
In ig. .1, there will be large number of high
shipping the product, or misfit while manutaCuring (assembling). r Ven
alignment while
initial friction between noving parts, etc.
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MANAGEMENT
Useful life

-Early failures Rare failures -Normal failures

Time

Fig. 8.1 Product failure rate

Reliability Improvement
The reliability of asystem/product depends on many factors. So, we should concentrate at the
grassroot level to improve product's reliability.
Some of the ways of improving systems reliability are listed below:
Improved design of components
" Simplification of product structure
Usage of better production equipments
" Better quality standards
" Better testing standards
Sufficient number of standby units
Usage of preventive maintenance if necessary at
appropriate time.
8.4 MAINTENANCE PLANNING
Planning of maintenance jobs basically deals with
of the iob: 'what activities are to be answering two questions, 'what' and ow
done?" and 'how those jobs and activities are to be done?
While answering these two questions, other
'where the jobs is to be done? and 'why the job supplementary
is
questions are to be answered, e.g
in developing 'what' and "how' of the to be done? etc., but all these will be helping
he applied extensively to job. It is very essential that engineering
knowledge must
maintenance jobs for development of appropriate job plans using
suited techniques, tools materials and special facilities etc. most
As the job planning forms the basic
actions depends, persons responsible for job foundations, over which the
planning should have efficiency and cost of
knowledge about jobs and available techniques, facilities and adequate capabilities, such as,
resources, analytical ability,
logical ability and judgmental courage ec. Conceptual
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Steps of Job Planning
The main steps to be followed for
1 Knowledge base: It proper job planning are:
materials and facilities. includes knowledge about equipment, job, available techniques,
Jobinvestigation at site: lt
2 ldentify and document the gives
work:
a clear perception of the total
Knowing the
jobs.
noeds of preventive, predictive and other earlier two steps and knowing the
4. Development of repair plan: maintenance jobs.
Preparation of step by step procedures which would
accomplish the work with the most economical
5. Preparation tools and facilities list use of time, manpower and material.
facilities needed. indicating the needs of special tools, tackles and
6.Estimation of time required to do the job with work
critical path analysis. measurement technique and
8.5 MAINTENANCE SCHEDULING
Scheduling is the function of coordinating all of the logistical issue around the issues regarding
the execution phase of the work. Scheduled of maintenance jobs basically deals with answering
two questions-Who' and 'When' of job, i.e., "who would do the job" and "when the job would
be started and done".
Effective scheduling essentially needs realistic thinking. based on substantial data and records.
Majority of scheduling work necds to occur in areas such as overhead labour hours safety and
toolbox meetings, break times and training times ete. Addition of corrective and approved
improvement actions as dictated by the prioritization system and operations plan etc.
Requirements for Schedulers
A scheduler should also have knowledge about job, techniques, facilities, analytical ability and
judgmental courage. The scheduler must obtain knowledge/information about following ability and
judgmental courage. The scheduler must obtain information about following facts, before starting
his job:
1. Manpower availability by trade, location, shift, crew arrangement and permissible overtime
limitetc.
2. Man hour back log on current or unfinished jobs.
3. Availability of the equipment or area where the work has to be performed.
other required
4. Availability of proper tooBs, tackles, spares, consumables, structural and
materials.
these may be from other shops/
S. Availability of external manpower and their capabilities;
departments of the plant or from contractors (local, nearby, ancillary etc).
special lifting and handling facilities and
6. Availability of special equipments, jigs/fixtures,and time saving devices like pneumatic
cranes etc. This should also include labour
hammers and excavators etc.
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7. Starting date of the job: also often completion time of total job is predetermined and i
that case, resources are to be arranged accordingly.
8. Past schedules and charts (updated) if the same job has been done earlier, etc.
8.6 MAINTENANCE SCHEDULE TECHNIQUES
Different types of schedules are made suiting the respective job plans and different technigques
used for making and following those schedules. The first step of all scheduling is to breal
the job into small measurable elements,called activities and to arrange them in logical sequences
considering the preceding, concurrent and succeeding activities so that a succeeding activity
should follow preceding activities and concurrent activities can start together.
Arranging these activities in different fashion makes different types of schedules. They are
as follows:
1. Weekly general schedule is made to provide weeks worth of work for each employee
in an area.

2. Daily schedule is developed to provide a day's work for each maintenance employee
of the area.

3. Gantt charts are used to represent the timings of tasks required to complete a project.
4. Bar charts used for technical analysis which represents the relative magnitude of the
values.

5. PERTCPM are used to find the time required for completion of the job and helps in
the allocation of resources.