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the maintenance manager often controls the spare parts inventory, authorizes the use
of outside contract labor, and requisitions millions of dollars in repair parts or replace-
ment equipment. Therefore, one goal of the maintenance organization should be effec-
tive use of these resources.

18.8.4 Optimum Equipment Life
One way to reduce maintenance cost is to extend the useful life of plant equipment.
The maintenance organization should implement programs that will increase the
useful life of all plant assets.

18.8.5 Minimum Spares Inventory
Reductions in spares inventory should be a major objective of the maintenance orga-
nization; however, the reduction cannot impair the ability to meet goals 1 through 4.
With the predictive maintenance technologies that are available today, maintenance
can anticipate the need for specific equipment or parts far enough in advance to
purchase them on an as-needed basis.

18.8.6 Ability to React Quickly
All catastrophic failures cannot be avoided. Therefore, the maintenance organization
must maintain the ability to react quickly to unexpected failures.

18.9 THREE TYPES OF MAINTENANCE
There are three main types of maintenance and three major divisions of preventive
maintenance, as illustrated in Figure 18–4.

18.9.1 Corrective Maintenance
The little finger in the analogy to a human hand used previously in the book repre-
sents corrective (i.e., emergency, repair, remedial, unscheduled) maintenance. At
present, most maintenance is corrective. Repairs will always be needed. Better
improvement maintenance and preventive maintenance, however, can reduce the need
for emergency corrections. A shaft that is obviously broken into pieces is relatively
easy to maintain because little human decision is involved. Troubleshooting and diag-
nostic fault detection and isolation are major time consumers in maintenance. When
the problem is obvious, it can usually be corrected easily. Intermittent failures and
hidden defects are more time-consuming, but with diagnostics, the causes can be iso-
lated and corrected. From a preventive maintenance perspective, the problems and
causes that result in failures provide the targets for elimination by viable preventive
maintenance. The challenge is to detect incipient problems before they lead to total
failures and to correct the defects at the lowest possible cost. That leads us to the
middle three fingers—the branches of preventive maintenance.