Optimum Policies When Preventive Maintenance is Imperfect

This paper considers three models with imperfect preventive maintenance (pm), viz the unit after pm is not always like new; i) the unit is repaired upon failure, ii) the unit undergoes minimal repair at failure, and iii) the failed unit is detected only by perfect pm. Optimum preventive maintenance policies minimizing the s-expected cost rate for each model are discussed.