1.0 INTRODUCTION This note is on
maintenance, which encompasses all these activities that relate to keeping facilities and equipment in good
working order and makes necessary
repairs when breakdowns occur, so that the system can perform as
intended. The general objectives for the
note
are set below.
2.0 OBJECTIVES By the end of this
note, you should be able to
(i) Explain the importance of maintenance in production
systems.
(ii) Describe the range of maintenance activities
(iii) Describe and differentiate between reactive and proactive
approaches to maintenance.
(iv) State how the pareto phenomenon pertains to maintenance
decisions.
3.0 MAIN CONTENT
3.1 An Overview of
Maintenance
Maintaining the
production capability of an organization is an important function in any production system. It is
through this that production equipment
are adjusted, repaired and kept in good operating conditions. The
reasons for keeping equipment and
facilities in perfect operating condition are not only to avoid interruption to production, but also to
keep production cost low, keep product
quantity high, maintain safe working conditions, and avoid late on late shipments to customers. When equipments malfunction in both
manufacturing and service industries,
the consequences have a direct impact on:
(i) Production capacity: Naturally, equipment sidelined by
breakdown cannot produce. This
way, the capacity of the system is reduced.
(ii) Production costs: Since machines are not functioning, workers
too would be made idle. This situation cause
labour costs per note to increase. Apart
from this, when machine malfunction causes scrap products to be produced, note labour and
material costs increase. Furthermore,
maintenance department budgets include such costs as the costs of providing repair facilities, repair
crew, preventive maintenance
inspections, standby machines, and spare parts.
(iii) Product and service quality: Usually, poorly maintained
equipment produces low -quality
products. (iv) Employee or customer
safety: Worn-out equipment is most likely to
fail at any moment while in operation. These failures can cause injuries to workers, as well as to customers
(especially in the services sector)
(v) Customers
satisfaction: Whenever production equipment breaks down, the initial after math is that products
cannot be produced according to the
master production schedules. In essence, customers may not receive products when promised.
For better maintenance management, maintenance department are
usually developed within organizations.
A maintenance manager is usually a plant
engineer, who reports to either a plant manager or a manufacturing
manager. Generally, the organizational
level of the department depends on the
importance of maintenance to a particular organization.
Maintenance activities are often organized into two
categories:
(1) buildings and grounds, and
(2) equipment maintenance.
Buildings and grounds is responsible for the
appearance and functioning of buildings, parking lots, Lawns,
fences, etc. The buildings and grounds
workers include electricians, welders,
pipe fitters, steamfitters, painters, glaziers, carpenters, janitors,
and grounds keepers. The equipment maintenance group is
responsible for maintaining machinery
and equipment in good working condition, and making all necessary
repairs.
This group can include such workers as machineries, mechanics,
welders, oilers, electricians,
instrument calibrators, and electronic technicians. The degree of technology of the production
processes, the amount of investment in
plant and equipments, the age of the buildings and equipment, and other factors will affect how maintenance
departments are organized, the required
workers skills, and the overall mission of maintenance departments.
3.2 Approaches to
Maintenance
Decision makers have two basic options with respect to
maintenance. The first is option
reactive and this is to deal with breakdowns or other problems when they occur. This is commonly referred to as
breakdown maintenance (B M). The second
option is proactive, the purpose of which is to reduce breakdowns through a programme of lubrication,
adjustment, cleaning, inspecting, and
replacement of worn parts. This is generally knows as preventive
maintenance (PM).
Usually a trade-off is made between these two basic options that
will minimize their combined cost. For
instance, with no preventive maintenance, breakdown and repair costs would be tremendous. In
addition, hidden costs, such as cost
production and the loss of wages while the equipment is not in service
must be considered. Cost injury and
damage to other equipment and facilities or to
other notes in production must also be taken into consideration.
However, beyond a certain point, the cost of preventive
maintenance activities exceeds the
benefit. The best approach really, is to seek a balance between preventive maintenance costs and breakdown
maintenance costs. This concept is
illustrated in Figure 20.1 
Figure 20.1
Amount of Preventive Maintenance
As figure 20.1 shows, some minimum amount of PM is necessary to
provide the mini mal amount of
lubrication and adjustment to avoid a complete and imminent collapse of the production system.
At this minimal level of PM, the cost of
breakdowns, interruption to production, and repairs is so high that total production, and repair is so high that the
production cost is beyond practical
limits.
This is mainly a remedial
policy, i.e., fix the machines only when they
breakdown or will not operate any longer. As the PM effort is
increased, breakdown and repair cost is
reduced. Note that the total maintenance cost is the sum of the PM and the breakdown and
repair costs.
Also observe that at some
point, for each piece of equipment, addition spending for PM is uneconomical because PM costs rise faster
than breakdown and repair costs fall.
Conceptually, operations managers seek to find the optimal level of PM where total maintenance costs are at a
minimum both for each piece of equipment
and the entire production system. Let us examine both the PM and BM into some detail.
3.2.1 Preventive Maintenance (PM)
As you must be aware by now, the goal of PM is to reduce the
incidence of breakdowns or failures in
the plant or equipment in order to avoid the
associated costs. These can include loss of output, idle workers,
schedule reduction; damage to other
equipment, products, or facilities, and repairs, which may involve maintaining inventories of
spare parts, repair tools and equipment,
and repair specialists.
In particular, PM can be an
important factor in achieving operation's strategies. For example, a PM program can be essential to
the success of a product focused
positioning strategy. In product-focused positioning strategies, standardized product designs are produced
along production lines where these are
little, if any in-process inventories between adjacent operations. Hence, if a machine breakdown at one operation, all other
downstream operations will soon run out of
parts of work on.
Therefore, an extensive PM programme in such system will reduce the frequency and
severity of machine breakdowns. PM
programmes are similarly essential in automated factories, where systems of automated machines operate continuously
without the need for production workers
(i.e. workless factories). In such an environment, a large number of maintenance workers would be needed to keep
the machines adjusted, lubricated, and
in good operating condition.
Very often, PM is periodic, and it can be programmed according to
the availability of maintenance
personnel as well as to avoid interference with
operating schedules. PM is generally programmed using some combination
of the following three options.
(i) The result of planned inspections that reveal a need for
maintenance
(ii) According to the calendar (passage of time)
(iii) After a pre-determined number of operating hours.
Normally, PM is performed just prior to a breakdown or failure
because this will result in the longest
possible use of equipment of facilities without a breakdown. Predictive maintenance is an
attempt to determine when to perform PM
activities. It is generally based on historical records and analysis of technical data to predict when a piece of
equipment or part is about to fail.
The effectiveness of PM
often depends on how good the predictions of failures are. A good PM effort relies on complete records
for each piece of equipment. Such
records must include information like date of installation, operating
hours, dates and types of maintenance
and dates and types of repairs. A new
concept, known as Total Preventive Maintenance (TPM) is being practiced in Japan.
Companies operating TPM usually have their workers Perform PM on the machines they operate,
rather than use separate maintenance
personnel for that task. The TPM is consistent with Just-In-Time (JIT) systems and lean production, where
employees are given greater
responsibility for quality, productivity, and the general functioning of
the system.
3.2.2 Breakdown Maintenance (BM)
Though the risk of a breakdown can be drastically reduced on by an
effective PM programme, occasional
breakdowns may still occur. Actually, firms with good preventive practices have some need for
breakdown programmes. It is obvious that
organisations that rely less on PM have an even greater need for effective ways of dealing with
breakdowns. Very much unlike PM,
breakdowns cannot be scheduled. Rather they must be dealt with on an irregular basis (i.e. as
they occur). The following approaches
are being used to deal with breakdowns:
(i) Standby or backup equipment that can be quickly pressed into
service
(ii) Inventories of spare parts that can be installed as needed,
thereby avoiding lead times involved in
ordering parts, and buffer inventories, so
that other equipment will be less likely to be affected by
short-term downtime of a particular
piece of equipment.
(iii) Operators who are able to perform at least minor repairs on
their equipment.
(iv) Repair people who are well trained and readily available to
diagnose and correct problems with
equipment.
The extent to which any organisation pursues any or all of these
approaches depends on how important a
particular piece of equipment is to the overall production system. At one extreme is the
equipment that is the focal point of a
system (e.g. vital operating parts of a car, such as brakes,
transmission, ignition and engines or
printing presses for a publishing house). At the other extreme is the equipment that is rarely used since it
does not perform any important function
in the system, and equipment for which substitutes are readily available.
What is the implication of this? Usually, breakdown programmes
are most effective when they take into
account, the degree of importance a piece of
equipment has in the production system, as well as the ability of the
system to do without it for a period of
time. For these types of situations, the Pareto
phenomenon exists: A relatively few pieces of equipment will be
extremely important to the functioning
of the system, thereby justifying considerable
effort and/or expense; some will require moderate effort or expense;
some will require moderate effort or
expense and many will justify little effort or
expense.
3.3 Replacement Decisions These are situations
when breakdowns become frequent and/or costly. The manager is thus faced with a trade-off
decision in which costs are important
consideration. What is the cost of replacement compared with the cost
of continued maintenance? At times, a
question like this is difficult to resolve,
most especially if future breakdowns cannot be readily predicted. The
manager may thus, need to examine
historical records in order to project future
experience. Another important
factor is technological change.
For instance, newer
equipment may have some features that favour replacement over
either preventive or breakdown
maintenance. At the same time, the removal of old equipment and the installation of new
equipment may cause disruptions to the
system, which may actually be greater than the disruptions caused
by breakdowns. In addition, employees
may have to be trained to operate the new
equipment. Finally, forecasts of future demand for the use of the
present or new equipment must be taken
into account.
3.4 Machine Reliability It is necessary for
you to know the concepts of reliability and their relationship to maintenance management. Machine
reliability is the likelihood of a machine
breaking down, malfunctioning, or needing repairs in a given time period
or number of hours of use. If machine
reliability can be increased, the incidence
of machine breakdowns and the cost of the havoc caused in production
by breakdowns can also be reduced.
There are three approaches to improving machine reliability:
over-design, design simplification, and
redundant components. All these take place by the time a machine is designed. Over design means
enhancing a design to avoid a
particular type of failure. For instance, if a machine has only a few
independent critical interacting parts,
then over design may be an effective way of
increasing machine reliability.
Design simplification implies a reduction in the number of
interacting parts in a machine. Since
there are now fever parts that can fail, machine reliability increases when the number of interacting part
s is reduced. Redundant components are
the building of backup components right into the machine so that if one part fails, its backing is
automatically substituted. These three
approaches can be sued together or separately to design more
reliable machines.
3.5 Secondary Maintenance Responsibilities As earlier mentioned, all maintenance departments are responsible
for the repair of buildings and equipment
and for performing certain preventive
maintenance inspections, repairs, lubrication, and adjustments. Additionally, some particular
responsibilities have traditionally been added to these departments. For instance,
housekeeping, janitorial, window cleaning,
ground keeping and painting services are now usually performed by maintenance departments.
These activities often embrace all areas of the facility, from restrooms to offices to
production departments to warehouses.
Within some plants, it is usual to find the area around each production
worker's immediate workplace being
cleaned by the worker, while the appearance and
cleanliness of all other areas are the responsibility of the
maintenance department. Again, in some organisations, additional activities
such as new construction, remodeling,
safety equipment maintenance, loss prevention, security, public hazard control. Waste disposal and recycling
and pollution control responsibilities
have been assigned to their maintenance departments.
3.6 Current Trends in Maintenance Management There is no doubt that production machinery today is far more
complex than it was some years ago. For
instance, computerised controls, robotic (especially in developed countries) new technology in
metallurgy, more sophisticated
electronic controls, new methods in lubrication technology and
other developments have resulted in the
way complex machines are maintained.
Consequently, special training programmes are being mounted to give maintenance workers the skills necessary to
service and repair today's specialised
equipment. In addition, subcontracting service firms have evolved to supply specialised maintenance services.
It is now common to see computers,
automobiles, office machines, and other equipment and facilities being serviced by outside subcontracting
firms. In particular, their specialised
training and fee structure, which is usually based on an as needed
basis, combine to offer competent
service at reasonable cost. Furthermore,
other technologies that reduce the cost of maintenance while improving the performance of production
machines are now available. An example
here is the network of computerized temperature - sensing probes connected to all key bearings in a machine
system. When bearings being to fail,
they overheat and vibrate, thus causing these sensing systems to
indicate that a failure is imminent.
Consequently, the massive damage to machines that could happen when bearings fail can therefore be
avoided. Another modern trend is the
application of computers to maintenance
management. There are at least five general areas in maintenance
that commonly use computer assistance.
These are:
(i) Scheduling maintenance projects
(ii) Maintenance cost reports by production department, cost
category and other classifications
(iii) Inventory status reports for maintenance parts and
supplies
(iv) Parts failure data, and
(v) Operations analysis studies, which may include computer
simulation, waiting lines (queuing
theory), and other analytical programmes.
In spite of the fact that computers, robots, and high-tech
machinery are important concerns in
maintenance management today, people concerns may actually be at the heart of better
maintenance.
Hence, one important trend is the
involvement of production workers in repairing their own machines
and performing PM on their own machines.
In this regard, widening the scope of
workers' jobs to include maintenance of their machines, would not
only improve maintenance, but may
actually result in numerous side benefits.
From this discussion, it is very clear that maintenance today in
production and operations management
(POM) means more than simply maintaining the
machines of production.
Since POM has broadened its perspectives from minimizing short range costs to other,
long-range performance measures such as
customer service, return on investment, product quality, and providing for workers' needs, maintenance too, has
broadened its own perspectives. Hence,
maintenance in the present day means that the prompt supply of
quality products and services is what is
maintained, not merely machines.
4.0 CONCLUSION
You have learned in this note, the importance of keeping
production equipment adjusted, repaired,
and in good operating condition. You also learned the direct impacts of equipment malfunctioning on both
manufacturing and service industries.
You were again thought that maintenance today means more than simply maintaining the machines of
production. In addition, prompt supply of
quality products and services is also maintained.
5.0 SUMMARY
Maintaining the productive capability of an organisation is an
important function. Maintenance includes
all of the activities related to keeping facilities and equipment in good operating order and
maintaining the appearance of buildings
and grounds.
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