Optimizing Preventive Maintenance Policies: A Hydroelectric Power Plant Case Study

Optimizing preventive maintenance (PM) policies consists of determining the optimal times for carrying out maintenance actions to minimize the process's total cost. The longer the time interval between preventive maintenance, the lower the corresponding cost. On the other hand, longer intervals between PMs increase the expected number of failures and, consequently, the need for corrective actions that increase the overall maintenance cost. Preventive maintenance actions are associated with a level of interventions, which can be defined as a weighted average of the number of tasks performed, the execution time, and the number of items replaced in the maintenance plan. Therefore, the objective of this work is to propose a method to determine the preventive maintenance intervals and the efficiency of these maintenance actions to minimize the total cost of a fixed horizon planning process. In general, the level of interventions is treated as a variable dependent on preventive maintenance time, which means that the longer the time interval between PMs, the greater the level of intervention of the maintenance action should be, in theory, and consequently, the greater its cost. In the optimization process proposed in this work, however, the level of interventions is treated as an independent variable of PM intervals, representing a contribution of this paper, and providing greater flexibility in the creation of maintenance plans. To validate the proposed method, it is applied to the preventive maintenance policies of a hydroelectric power plant in southern Brazil. Results show that optimizing maintenance intervals can significantly reduce the total cost of maintenance.

Keywords: Preventive maintenance, Imperfect maintenance, Hydroelectric power plant.

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