A survey of maintenance policies of deteriorating systems

In the past several decades, maintenance and replacement problems of deteriorating systems have been extensively studied in the literature. Thousands of maintenance and replacement models have been created. However, all these models can fall into some categories of maintenance policies: age replacement policy, random age replacement policy, block replacement policy, periodic preventive maintenance policy, failure limit policy, sequential preventive maintenance policy, repair cost limit policy, repair time limit policy, repair number counting policy, reference time policy, mixed age policy, preparedness maintenance policy, group maintenance policy, opportunistic maintenance policy, etc. Each kind of policy has different characteristics, advantages and disadvantages. This survey summarizes, classifies, and compares various existing maintenance policies for both single-unit and multi-unit systems. The emphasis is on single-unit systems. Relationships among different maintenance policies are also addressed.