A GENERALIZED GROUP MAINTENANCE POLICY

This paper proposes a two-phase maintenance policy for a group of iden tical repairable units. We define the time-interval (0, T] as the firs t phase, and the time interval (T, T + W] as the second phase. As indi vidual units fail individual units have two types of failures. Type I failures (minor failures) are removed by minimal repairs (in both phas es), whereas Type II failures (catastrophic failures) are removed by r eplacements (in the first phase) or are left idle (in the second phase ). A group maintenance is conducted at time T + W or upon the kth idle , whichever comes first. The optimal policy is to select T, W* and k* to minimize the expected cost per unit time for an infinite time span . Various special cases are considered. Numerical examples are given t o illustrate the method.