Calendar-time-based and age-based maintenance policies with different repair assumptions

Abstract

Traditional maintenance models usually assume that the time duration required for conducting corrective repairs is negligible for mathematical tractability. In this paper, we propose two new preventive maintenance policies that take non-negligible repair time into consideration: One is a calendar-time-based maintenance policy in which a system should be preventively replaced at either of two predetermined calendar time instants, depending on the system state; and the other is an age-based maintenance policy in which a system should be preventively replaced at a predetermined age. Under both policies, if any failure occurs before replacement, then the system will be repaired. In particular, four repair assumptions—perfect, imperfect, minimal, and worse-than-minimal—that correspond to different repair effectiveness, are considered. We derive the long-run average cost rates for the two maintenance policies under different repair assumptions, respectively, and investigate the existence and uniqueness of the solutions of optimal maintenance decisions. Numerical studies are then conducted to compare the two maintenance policies, providing guidelines on which policy should be adopted by system operators in various scenarios.