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.
We use the following definition of preventive maintenance (PM):
Preventive maintenance is the performance of inspection and/or servicing tasks that have been preplanned (i.e., scheduled) for accomplishment at specific points in time to retain the functional capabilities of operating equipment or systems.
The word "preplanned" is the key element in developing a proactive maintenance mode and culture. In fact, this now provides us with a very clear and concise way to define corrective maintenance (CM):
Corrective maintenance is the performance of unplanned (i.e., unexpected) maintenance tasks to restore the functional capabilities of failed or malfunctioning equipment or systems.As viewed by the authors, the entire world of maintenance activity is fully encompassed in these two definitions.
However, there are two troubling factors that people frequently question which give rise to some of the confusions over the "PM or CM" discussions. The first of these involves the games that people play with the terminology. These games can be driven by such diverse nontechnical factors as accounting practices or political (regulatory) pressures. For example, some plants, in addition to planned outages and forced outages, have a third category known as a maintenance outage (MO).
The MO occurs as a result of an unexpected equipment problem which hasn't quite yet reached the full failure state but will do so very soon. So the plant management will delay the shutdown until some off-peak period when the plant outage is more tolerable, and hope that the equipment will hold out until then.
Now from an operational point of view, this is a very smart thing to do — but, as a rule, MOs are not counted when it comes to reporting the plant forced outage rate. Somehow they seem to wind up in the preplanned category ("after all, we planned to fix it next Saturday!"). Make no mistake about it, an MO is a forced outage and should be labeled as such when measurements are made. You are only kidding yourself to do otherwise.
Please also read:
Develop Good Strategies For Effective Preventive Maintenance (2/2)
Source: Anthony M. Smith and Glenn R. Hinchcliffe (Plant Engineering - November 1, 2005)
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.
We use the following definition of preventive maintenance (PM):
Preventive maintenance is the performance of inspection and/or servicing tasks that have been preplanned (i.e., scheduled) for accomplishment at specific points in time to retain the functional capabilities of operating equipment or systems.
The word "preplanned" is the key element in developing a proactive maintenance mode and culture. In fact, this now provides us with a very clear and concise way to define corrective maintenance (CM):
Corrective maintenance is the performance of unplanned (i.e., unexpected) maintenance tasks to restore the functional capabilities of failed or malfunctioning equipment or systems.As viewed by the authors, the entire world of maintenance activity is fully encompassed in these two definitions.
However, there are two troubling factors that people frequently question which give rise to some of the confusions over the "PM or CM" discussions. The first of these involves the games that people play with the terminology. These games can be driven by such diverse nontechnical factors as accounting practices or political (regulatory) pressures. For example, some plants, in addition to planned outages and forced outages, have a third category known as a maintenance outage (MO).
The MO occurs as a result of an unexpected equipment problem which hasn't quite yet reached the full failure state but will do so very soon. So the plant management will delay the shutdown until some off-peak period when the plant outage is more tolerable, and hope that the equipment will hold out until then.
Now from an operational point of view, this is a very smart thing to do — but, as a rule, MOs are not counted when it comes to reporting the plant forced outage rate. Somehow they seem to wind up in the preplanned category ("after all, we planned to fix it next Saturday!"). Make no mistake about it, an MO is a forced outage and should be labeled as such when measurements are made. You are only kidding yourself to do otherwise.
Please also read:
Develop Good Strategies For Effective Preventive Maintenance (2/2)
Source: Anthony M. Smith and Glenn R. Hinchcliffe (Plant Engineering - November 1, 2005)
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