Critical and emergency spares

There are various ways to determine optimal stock size, for stocks composed of either (i) non-repairable or (ii) repairable parts. Optimization criteria considered are minimization of costs, maximization of availability, and maximization of stock reliability (i.e., probability that a spare part request will not be rejected due to lack of spare units in stock). For the last of these, we can perform instantaneous and interval reliability calculations. We have integrated several models into a prototype software package, and have applied the software in industry projects in utilities and mining.