Preventive Maintenance Subject to Equipment Unavailability

Preventive maintenance has received considerable attention in industries and the literature. Conventional preventive maintenance models often assume that equipment is always available for maintenance activities. However, in many mission-critical industries, equipment may not be available for scheduled maintenance due to busy operational schedules. Forced shutdown of the equipment may incur extra costs that cannot be offset by the benefits from preventively maintaining the equipment. In this paper, we propose innovative preventive maintenance policies to address the challenges caused by equipment unavailability. Maintenance models with possible rescheduling are developed for both time-based and condition-based maintenance policies, and the objective is to minimize the long-run cost rate of all maintenance activities. The proposed policies, with consideration of equipment unavailability for prescheduled PM, are compared with the policies that ignore this unavailability. Numerical examples are provided to illustrate the proposed policies.