Page 12 - An Introduction To Predictive Maintenance

2 An Introduction to Predictive Maintenance

that have implemented more advanced manufacturing and maintenance management
philosophies.

The dominant reason for this ineffective management is the lack of factual data to
quantify the actual need for repair or maintenance of plant machinery, equipment, and
systems. Maintenance scheduling has been, and in many instances still is, predicated
on statistical trend data or on the actual failure of plant equipment.

Until recently, middle- and corporate-level management have ignored the impact of
the maintenance operation on product quality, production costs, and more important,
on bottom-line profit. The general opinion has been “Maintenance is a necessary evil”
or “Nothing can be done to improve maintenance costs.” Perhaps these statements
were true 10 or 20 years ago, but the development of microprocessor- or computer-
based instrumentation that can be used to monitor the operating condition of plant
equipment, machinery, and systems has provided the means to manage the mainte-
nance operation. This instrumentation has provided the means to reduce or eliminate
unnecessary repairs, prevent catastrophic machine failures, and reduce the negative
impact of the maintenance operation on the profitability of manufacturing and pro-
duction plants.

1.1 MAINTENANCE MANAGEMENT METHODS

To understand a predictive maintenance management program, traditional manage-
ment techniques should first be considered. Industrial and process plants typi-
cally employ two types of maintenance management: run-to-failure or preventive
maintenance.

1.1.1 Run-to-Failure Management
The logic of run-to-failure management is simple and straightforward: When a
machine breaks down, fix it. The “If it ain’t broke, don’t fix it” method of maintain-
ing plant machinery has been a major part of plant maintenance operations since the
first manufacturing plant was built, and on the surface it sounds reasonable. A plant
using run-to-failure management does not spend any money on maintenance until a
machine or system fails to operate.

Run-to-failure is a reactive management technique that waits for machine or equip-
ment failure before any maintenance action is taken; however, it is actually a “no-
maintenance” approach of management. It is also the most expensive method of
maintenance management. Few plants use a true run-to-failure management philoso-
phy. In almost all instances, plants perform basic preventive tasks (i.e., lubrication,
machine adjustments, and other adjustments), even in a run-to-failure environment.
In this type of management, however, machines and other plant equipment are not
rebuilt, nor are any major repairs made until the equipment fails to operate. The major
expenses associated with this type of maintenance management are high spare parts