Optimal quasi-periodic preventive maintenance policies for a two-unit series system with dynamic maintenance plan

Abstract

Most research on preventive maintenance (PM) assumed that a PM interval is a fixed value. However, practical PM actions usually are affected by some internal and external random factors, which make the PM interval become a limited random value rather then a fixed value. Few of the existing research consider this situation for two-unit system in their models. In this paper, a quasi-periodic PM policy for one type of two-unit series system with a dynamic maintenance plan is proposed, in which PM for U1 is perfect whereas for U2 is imperfect, and the dynamic PM plan is executed in each implemented period, and PM activities are performed through competing results of the dynamic PM plan and a catastrophic failure of U2. The optimal implemented period of PM and PM number is obtained which minimizes the excepted cost per unit time of the system in long run. Finally, a numerical example is given to illustrate the proposed model. © 2014 Springer-Verlag.