Page 58 - Intro Predictive Maintenance

Role of Maintenance Organization 49

Figure 3–2 Preventive maintenance to keep acceptable performance.

• Cost–benefit relationship. Too often, organizations consider only costs
without recognizing the benefit and profits that are the real goal. Preventive
maintenance allows a three-way balance between corrective maintenance,
preventive maintenance, and production revenues.

Disadvantages. Despite all the good reasons for doing preventive maintenance,
several potential problems must be recognized and minimized:

• Potential damage. Every time a person touches a piece of equipment,
damage can occur through neglect, ignorance, abuse, or incorrect proce-
dures. Unfortunately, low-reliability people often service much high-
reliability equipment. The Challenger space shuttle failure, the Three Mile
Island nuclear power plant disaster, and many less-publicized accidents have
been affected by inept preventive maintenance. Most of us have experienced
car or home appliance problems that were caused by something that was
done or not done at a previous service call. This situation gives rise to the
slogan: “If it works, don’t fix it.”
• Infant mortality. New parts and consumables have a higher probability of
being defective or failing than exists with the materials that are already in
use. Replacement parts are too often not subjected to the same quality assur-
ance and reliability tests as parts that are put into new equipment.
• Parts use. Replacing parts at preplanned preventive maintenance intervals,
rather than waiting until a failure occurs, will obviously terminate that part’s
useful life before failure and therefore require more parts. This is part of the
trade-off among parts, labor, and downtime, of which the cost of parts will
usually be the smallest component. It must, however, be controlled.
• Initial costs. Given the time-value of money and inflation that causes a dollar
spent today to be worth more than a dollar spent or received tomorrow, it
should be recognized that the investment in preventive maintenance is made
earlier than when those costs would be incurred if equipment were run until
failure. Even though the cost will be incurred earlier—and may even be
larger than corrective maintenance costs would be—the benefits in terms of
equipment availability should be substantially greater from doing preven-
tive tasks.
• Access to equipment. One of the major challenges when production is at a
high rate is for maintenance to gain access to equipment in order to perform