Experience has clearly shown that some confusion does exist over just what people mean when they use the term preventive maintenance. One significant factor stems from the evidence that a vast majority of our industrial plants and facilities have been operating for extended periods, years in many cases, in a reactive maintenance mode. That is to say that the maintenance resources have been almost totally committed to responding to unexpected equipment failures. Corrective, not preventive, maintenance is frequently the operational mode of the day, and this tends to blur what is preventive and what is corrective.
In one actual extreme case, a plant developed an entire culture that fostered a feeling of pride in people's ability to fix things rapidly and under pressure when a forced outage occurred. Plant personnel viewed their actions as preventive in the sense that they were able to "prevent" a long outage because of their highly efficient and effective reactive and corrective actions. What the plant staff did not consciously recognize (or acknowledge) was that they were the highest cost per unit producer among their peers.
Tip provided by Anthony "Mac" Smith, Author, RCM - Gateway to World Class Maintenance, Butterworth-Heinemann, ISBN-10: 075067461X