An index policy for scheduling group maintenance services

Group maintenance is an effective strategy for maintaining unreliable multiunit systems. This strategy benefits from economies of scale when the per unit maintenance time is negligible compared to the fixed setup time, which is typical in multiunit systems. The type of multiunit system that we are interested in corresponds to a production facility with identical machines operating in parallel, where each machine undergoes a Markov degradation process and incurs production losses as its condition deteriorates. We propose a practical index policy for scheduling the group maintenance services in a multiple facility setting with limited maintenance resources. This policy is derived from a restless bandits model, where the objective is to minimize the expected discounted production losses over an infinite horizon. We provide numerical results to illustrate the effectiveness of our policy.