Inspection and replacement policy with a fixed periodic schedule

Abstract

We study an inspection and replacement policy for a system when maintenance actions are executed at times or “visits” with a fixed, periodic schedule. Then, the novel focus of the paper is not when to schedule maintenance but what maintenance to schedule at known times. Violations (defaults) may occur because time or resource is limited. The model is motivated by maintenance policy typically used for high-value, engineered systems e.g. windfarms, transportation systems, manufacturing lines. This motivation underlies the importance of the work. Inspections are modelled using the delay time concept. System lifetime is heterogeneous, so that early defects, due to say poor quality parts or installation, may occur. There is a lag between failure and corrective replacement and so we model the cost of downtime. We determine the cost-rate, system reliability and average availability of a policy with an initial inspection (preventive maintenance) phase followed by a wear-out (corrective maintenance) phase. A numerical example illustrates and investigates characteristics of the policy. Results indicate that the scheduled time for preventive replacement and the effective visit-frequency have the largest effect on policy performance. The policy is scalable to multi-component systems in a way that facilitates the study of grouping policies.