Optimal maintenance policies applicable to repairable systems onboard ships

Abstract

Maintenance, a key element of Integrated Logistics Support, plays a very vital role throughout an equipment/system planned life-cycle. Maintenance costs contribute a major portion of the life cycle costs of an equipment or system. Past historical records have shown that the cost associated with system maintenance is immense and usually takes up a large portion of the annual operating expenditure. Besides the costs, sound maintenance efforts contribute to better operational availability and reliability of a system. Therefore, the objective is to attain the proper balance of operations between performance and effectiveness, and logistics support, which largely includes maintenance, spares requirements, and the available budget. Adequate maintenance is essential to ensure the effective and economical support of an equipment or system. Therefore there is a need to design optimal maintenance policies to maximize appropriate measures of system effectiveness. These can be either to minimize operational and maintenance costs, to improve overall system reliability or to maximize operational availability. In this thesis, various maintenance scenarios are examined and the corresponding optimal maintenance actions are planned to take place at intervals chosen so as to maximize an appropriate measures of effectiveness. Preventive maintenance policies are also planned so that the overall reliability of the system is always kept above a specified minimum reliability level, while wither keeping the cost per unit time to a minimum or maximizing the operational availability, subject to cost constraints.