Abstract:

Inspections are common activities in most preventive maintenance (PM) programs. The models for optimizing the inspection interval using the two-stage delay time have been presented by many researchers. However, the three-stage failure process introduced by Wang is closer to reality corresponding to the actual industrial applications. When the minor defective stage is identified at an inspection, the inspection interval is halved. However, whether this measure is optimal is not explained. In order to solve this problem, an inspection optimization model is proposed to minimize the expected cost per unit time with the inspection interval and shortening proportion of the inspection interval after identifying the minor defective stage as the decision variables. A numerical example is presented to illustrate the applicability of the proposed model.