Varying Repair Capacity in a Repairable Item System

Expensive parts of machines do not have to be discarded when broken. Instead they can be repaired and put back into stock, forming a repairable item system. Lots of methods are known to determine stock levels, the number of backordered parts and waiting times in repairable item systems. Some of these methods consider limited repair capacity, but assume the capacity to be constant. In industrial practice, however, the capacity in the repair shop varies due to vacation times of the workers, reducing it temporarily. At the end of the vacation times the backorders of unrepaired, broken parts in the repair shop and unfulfilled part requests at the depot have to be diminished. Furthermore, the varying capacity influences the performance of the spare parts provisioning, incurring the need for higher stock levels. The impact of varying repair capacity on a system for repairable items is analyzed in this paper. It is shown how the stock levels have to be adjusted to guarantee a maximum backorder level of waiting request during the entire year.