Comparison of Three Cumulative Damage Models

Abstract

Aged fossil-fired power plants are increasing greatly in Japan and they need the appropriate maintenance for their steady operations. The preventive maintenance (PM) of such systems is indispensable to avoid the serious trouble such as the emergency stop of power supply. To predict the lifetime of system and design a suitable maintenance, the cumulative damage models are applicable. This paper considers three cumulative damage models: (1) A unit is subjected to shocks and suffers some damage due to shocks. (2) The amount of damage due to shocks is measured only at periodic times. (3) The amount of damage increases linearly with time. The total damage is additive and the unit fails when the total damage has exceeded a failure level for three models. Models 2 and 3 would be actually used as the approximated ones of Model 1 and Models 1 and 2, respectively. As the preventive replacement policy, the unit is replaced before failure at a planned time. The expected cost rates of each model are obtained, and optimal policies that minimize them are derived. Further, optimal policies of each model are compared numerically when each model has the same mean amount of damage at any periodic times.