SPARE PROVISIONING POLICY BASED ON MAXIMIZATION OF AVAILABILITY PER COST RATIO

A method, based on the stochastic continuously reviewed fixed reorder quantity policy (Q, r), is proposed. The values of Q and r are chosen to minimize a modified cost function representing the ratio between the inventory expected costs per unit time and a spare parts availability measure. A probabilistic inventory model, in which the lead time is assumed to be log-normally distributed, is used. The demand during the lead time is defined by the probability of having a certain number of failures within useful life. A complete formulation of the spare provisioning optimization problem is presented together with an efficient selective search technique for obtaining an exact optimal solution.