Optimal maintenance policies for repairable systems with repair facilities not always available

Traditionally, in the literature about repairable systems, the repair facilities are always available. This communication considers a more general case in which the repair facilities are not always available, but are available only an interval of time of the working period. If the repair facilities are available and the system fails, the repair starts immediately. But if the repair facilities are not available and the system fails, the system remains in failed state until the beginning of the next working period when a planned replacement is performed. We assume that the repair facilities are available until T*, 0 <= T* <= T where (0, T] represents an entire working period. For this model, rewards and costs are associated with the operating and repair expected times. A cost is incurred if the system is down. The problem is to determine the optimum T* maximizing the expected reward of the system. If the repair rate of the system is non-decreasing, an optimal repair policy maximizing the expected reward is determined.