MAINTENANCE POLICIES FOR A TWO-UNITS SYSTEM: A COMPARATIVE STUDY

Abstract

This paper considers the age-based maintenance of a two-identical components system with economic dependences. Two existing approaches are presented and compared. One is a maintenance policy of (N,n)-type. It is very close to the optimal policy among all possible policies but difficult to optimize: Policy Iteration Algorithm is needed. The aim of the paper is to investigate if there are cases for which a simpler policy than those of (N,n)-type can be sufficient in terms of maintenance cost. A second approach proposed in literature (derived from the time-based block replacement one) is simpler but not sufficient in any situations. Some numerical experiments and an analysis of the stochastic behavior of the two-identical components system allows us to propose a third policy (Policy P). This third maintenance plan is simplified from the second one. It compensates for its weak point which is to be very expensive when the cost of replacement for one component is close to the cost of replacement for both components. Moreover it is possible to generalize this third policy from a two-identical components system to a n-identical components system. The performances analysis of the policy is based on numerical experiments.