Models of inspection, routine service, and replacement for a serviceable one-component system

Routine service (RS), inspection manually or aided by condition monitoring and preventive replacement are four types of preventive maintenance (PM) activities often observed in industry, but very few considered to model them together in a maintenance model. This paper proposes such a model for a serviceable one-component system to jointly model the effect of RS and inspection with replacement on the basis of the delay-time concept. The delay-time is a concept that divides a system failure process into two stages: from new until the point of an identifiable defect, and then from this point to failure. The first stage is called the normal stage and the second stage is called the failure delay-time stage. In this paper, we assume RS as the activity which can prolong the normal stage of the system and the replacement as the activity which can renew the system. The replacement could be either failure based or inspection based if the failure delay-time is identified at an inspection. The concept of age reduction is used to model the effect of RS and two inspection models are considered, e.g. without and with condition monitoring. A numerical example is shown to validate the modeling development.