TABLE OF CONTENTS I long to accomplish great and noble tasks, but it is my chief duty to accomplish humble tasks as though they were great and noble. The world is moved along, not only by the mighty shoves of its heroes, but also by the aggregate of the tiny pushes of each honest worker
Helen Keller
The previous chapter provided a brief introduction to Preventive Maintenance. Generally speaking, preventive maintenance is also pro-active but differs from predictive maintenance by the fact it typically includes an invasive task.
For instance, I might use vibration analysis as a predictive task up to the point that I am convinced a bearing is starting to fail. At that point, I will pro-actively change the bearing before a failure can occur. If I was involved with the maintenance of a large fleet of equipment using the same bearing in the same application after a number of similar experiences, I would be satisfied that the component has a specific life. (Here one might use Weibull analysis to determine the usable life.) Once the usable life has been determined it would become possible to perform preventive maintenance at the appropriate time. By doing so, I would prevent the majority of failure and at the same time, harvest most of the usable life.
In that last sentence, I introduced two limitations. I said I would prevent "most" of the failures and I would harvest "most" of the life. In attempting to harvest most of the usable life, I must...
