Availability optimization of periodically inspected production systems generating environmental damage

This paper deals with a condition-based maintenance policy for single-unit production systems which generate damage to environment as they degrade and get older. The system is submitted to periodic inspections to assess the generated environmental damage. In case an inspection reveals that the environmental degradation level has exceeded a critical level, the system is considered in a failed state and will have generated significant environmental damage. It is stopped during a certain time necessary to perform a corrective maintenance (CM) action and to eventually clean the environment. In order to prevent such an undesirable situation, a lower threshold level is considered to trigger a preventive maintenance (PM) action which takes less time than the corrective one. A mathematical model and a numerical procedure are developed to determine simultaneously the PM threshold level and the inspection period which maximize the stationary availability of the system. Numerical calculations are performed to illustrate the proposed model.