(S - 1, 5) Spare-Part Inventory Policy for Fleet Maintenance

In the operation and maintenance of a fleet of equipments which can be modeled as a closed queueing network, it is sometimes preferable to use one-for-one-ordering (S - 1, S) policy for the low-demand or high-cost spare parts. However, the basic (S - 1, S) inventory model is derived from and applies to the infinite fleet size. This paper presents heuristic methods to correct for the finiteness of the fleet size. By computing the open queueing network equivalent part demand rate, the basic (S - 1, S) inventory model can be used to decide the optimum stock level. The first, rough estimate of the optimal value of the stock level S can be determined easily. Then successively correcting for the average part demand rate, final value of the S* can be obtained. A computer program based on the heuristic algorithm is included.