Preventive Maintenance Plan Guide

Preventive maintenance is a schedule of planned maintenance actions aimed at the prevention of breakdowns
and failures. The primary goal of preventive maintenance is to prevent the failure of equipment before it actually
occurs. It is designed to preserve and enhance equipment reliability by replacing worn components before they
actually fail. Preventive maintenance activities include equipment checks, partial or complete overhauls at
specified periods, lubrication changes, and lubrication checks. In addition, workers can record equipment
deterioration so they know to replace or repair worn parts before they cause system failure. Recent technological
advances in tools for inspection and diagnosis have enabled even more accurate and effective equipment
maintenance. The ideal preventive maintenance program would prevent all equipment failure before it occurs.

Value of Preventive Maintenance:
There are multiple misconceptions about preventive maintenance. One such misconception is that PM is unduly
costly. This logic dictates that it would cost more for regularly scheduled downtime and maintenance than it
would normally cost to operate equipment until repair is absolutely necessary. This may be true for some
components; however, one should compare not only the costs but the long-term benefits and savings associated
with preventive maintenance. Without preventive maintenance, for example, costs for lost production time from
unscheduled equipment breakdown will be incurred. Also, preventive maintenance will result in savings due to
an increase of effective system service life.

Long-term benefits of preventive maintenance include:
Improved system reliability.
Decreased cost of replacement.
Decreased system downtime.

Long-term effects and cost comparisons usually favor preventive maintenance over performing maintenance
actions only when the system fails.

When Does Preventive Maintenance Make Sense:
Preventive maintenance is a logical choice if, and only if, the following two conditions are met:

Condition #1: The component in question has an increasing failure rate. In other words, the failure rate of the
component increases with time, thus implying wear-out. Preventive maintenance of a component that is assumed
to have an exponential distribution (which implies a constant failure rate) does not make sense!
Condition #2: The overall cost of the preventive maintenance action must be less than the overall cost of a
corrective action. (Note: In the overall cost for a corrective action, one should include ancillary tangible and/or
intangible costs, such as downtime costs, loss of production costs, lawsuits over the failure of a safety-critical
item, loss of goodwill, etc.)

If both of these conditions are met, then preventive maintenance makes sense.