A Multi-attribute Approach to Simultaneous Determination of Preventive Replacement Times and Order Quantity of Spare Parts

One of the most important activities in preventive maintenance is replacement of spare parts prior to failure. The aim of this paper is to propose an approach which determines jointly the preventive replacement interval and the spare parts inventory by considering different criteria and interacting with decision makers. In this approach, preventive replacement intervals, determined by experts of production and maintenance, are ranked by the analytical hierarchy process (AHP). Criteria such as cost per unit of time, availability, remaining lifetime, and reliability are used. Then, a mixed integer nonlinear multi-objective model is presented that simultaneously specifies the period of preventive replacement and the required number of spare parts. This model considers the mentioned criteria and the inventory control costs of spare parts as different objective functions. Since the solution of the problem depends on the decision maker's strategy, it needs to interact with the decision-makers, and consequently the proposed model could be solved using the goal programming approach. The applicability of the proposed approach is illustrated by two numerical examples. The effect of key parameters on the optimal decisions is investigated for the examples.