Page 426 - Intro Predictive Maintenance

World-Class Maintenance 417

Figure 18–5 Preventive maintenance to keep acceptable performance.

and brought back up to a high level. A good detection system catches degrading
performance before it ever reaches this level.

Quality. For the same general reasons discussed previously, good preventive mainte-
nance helps ensure quality output. Tolerances are maintained within control limits.
Productivity is improved, and the investment in preventive maintenance pays off with
increased revenues.

Support to Users. If properly publicized, preventive maintenance tasks help show
equipment operators, production managers, and other equipment users that the main-
tenance function is striving to provide a high level of support. Note that an effective
program must be published so that everyone involved understands the value of per-
formed tasks, the investment required, and individual roles in the system.

Cost–Benefit Ratio. 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 produc-
tion revenues.

Disadvantages
Despite all the good reasons for doing preventive maintenance, several potential prob-
lems 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 procedures. Unfortunately,
low-reliability people 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 results in 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 the materials that are already in use. Replacement parts are