Optimal inspection frequency

Maintenance management is expected to plan for all maintenance activities for the life of the equipment. It must be able to forecast and plan the future maintenance requirements of spares, man‐hours and total costs. As equipment ages and enters the wear‐out stage, with increasing failure rates, this forecasting becomes difficult. Maintenance management is faced with the dilemma of either resorting to high inventories, over‐planning and inflated budgets or of suffering stockouts, lengthy delays in repair and budget blowouts. A model for an optimal inspection frequency can help correct this. For an inspection frequency to be optimal, it must exactly match the failure rate of the equipment. Hence, with the use of a cost rate factor, the optimal inspection frequency can also be used as a tool for planning and forecasting maintenance costs. This paper develops an optimal model, ensuring that the inspection frequency is capable of matching the varying failure rates throughout the life of the equipment. It also demonstrates how this optimal inspection frequency can then be used to plan and forecast maintenance costs.