Modelling preventive maintenance for deteriorating repairable systems

This paper is concerned with practical methods for the analysis and modelling of data for repairable systems which are subject to preventive maintenance (PM) and still have an increasing rate of occurrence of failures. Aspects of testing for trend and fitting a nonhomogeneous Poisson process to data are discussed. Models for scheduling preventive maintenance to minimize cost or maximize availability are proposed. They show that the optimal PM cycle interval for these systems decreases with increasing equipment age. One-cycle and two-cycle finite-time-zone replacement models are also developed to decide the optimal time for replacing the equipment in current use.