Three-grade Preventive Maintenance Decision Making*

A complex repairable system generally adopts multi-grade preventive maintenance. The optimization of maintenance decision making is usually regarded as a complex mathematical problem. This study proposes a three-grade preventive maintenance optimization method for complex repairable system based on field failure data. Specifically, all failures are classified into three categories: minor, moderate and major failures according to two factors, the downtime and repair cost. Different failure categories are introduced to optimize different grades preventive maintenance. Cumulative failure numbers of three categories are used as condition variables to represent the failure intensity. The relations between the condition variables and operating time can be represented by a random failure point process model to the setup of maintenance decision making optimization models. An empirical case is used to illustrate the effectiveness of the proposed method. Based on the field failure data, an optimal period (or optimal cumulative failure number) of a certain grade preventive maintenance is determined, which can support maintenance decision-making.