| Abstract: | This paper derives the optimal block replacement policies for four different operating configurations of induced draft fans. Under the usual assumption of higher cost of repair or replacement on failure compared to preventive replacement, the optimal preventive replacement interval is found by minimising the total relevant cost per unit time. Specifically, this paper finds optimal preventive maintenance strategies for the following two situations. 1. (i)|Both the time to failure and time to carry out minimal repair or replacement are exponentially distributed. 2. (ii)|The time to failure follows the Weibull distribution and there is no possibility of on-line repair or replacement. For both situations closed form expressions are derived whose solutions give optimum preventive maintenance intervals. |
