Selection of optimum maintenance strategies based on a fuzzy analytic hierarchy process

This paper aims to evaluate different maintenance strategies (such as corrective maintenance, time-based preventive maintenance, condition-based maintenance, and predictive maintenance) for different equipment. An optimal maintenance strategy mix is necessary for increasing availability and reliability levels of production facilities without a great increasing of investment. The selection of maintenance strategies is a typical multiple criteria decision-making (MCDM) problem. To deal with the uncertain judgment of decision makers, a fuzzy modification of the analytic hierarchy process (AHP) method is applied as an evaluation tool, where uncertain and imprecise judgments of decision makers are translated into fuzzy numbers. In order to avoid the fuzzy priority calculation and fuzzy ranking procedures in the traditional fuzzy AHP methods, a new fuzzy prioritization method is proposed. This fuzzy prioritization method can derive crisp priorities from a consistent or inconsistent fuzzy judgment matrix by solving an optimization problem with non-linear constraints. A specific example of selection of maintenance strategies in a power plant with the application of the proposed fuzzy AHP method is given, showing that the predictive maintenance strategy is the most suitable for boilers. As demonstrated by this case study, the fuzzy AHP method proposed in this paper is a simple and effective tool for tackling the uncertainty and imprecision associated with MCDM problems, which might prove beneficial for plant maintenance managers to define the optimum maintenance strategy for each piece of equipment.