PERFORMANCE EVALUATION OF REPAIRABLE SYSTEMS WITH PREVENTIVE MAINTENANCE AND PRIORITY QUEUE REPAIR POLICIES

Abstract

The following paper is a detailed performance analysis of repairable systems that follow a preventative maintenance and a priority repair queue policy. The system is comprised of several repairable units that malfunction randomly with preventive maintenance measures being built into them to minimize the severity of the failures as well as enhance the overall reliability of the system over time. The number of repair facilities is one, and the critical units are assigned priorities in the repair in order to reduce the downtimes of the system. Semi- Markov processes and regenerative point techniques are used to model the stochastic behaviour of the system, and explicit expressions are derived of the key performance measures. These are the mean time to system failure (MTSF), steady-state availability, busy period of the repair facility, number of repairs per expected repairs, and long-run expected profit. Numerical analysis is done on the effects of the frequency of preventive maintenance, the rules of repair priority and the rate of failures and repairs on the performance of the system. Findings indicate that a combination of preventive maintenance and priority queue repair policy can be very effective in improving the availability of a system and its profitability and lessen the congestion of repair. The proposed model offers practical information to the system designers and maintenance planners in the process of optimizing maintenance and repair plans of complex engineering systems.