Using geometric processes to study maintenance problems for engines

In this study, first the sequential survival times and the sequential repair times of an engine were modelled by using a non-increasing geometric process and a non-decreasing geometric process respectively. Secondly the values of model parameters were estimated by applying special statistical methods. Finally the means of the sequential survival times and the means of the sequential repair times of an engine were estimated, and the optimum policy for the replacement of the engine determined. Significance: The performance of an engine decreases because of ageing and accumulated wear. The effects of ageing and accumulated wear are assumed to be irreversible, so that after a repair an engine will not work as well as it did when new. Consequently the survival time of an engine becomes shorter and shorter and the repair time of the engine becomes longer and longer. After a certain number of failures, an engine can still work but is no longer maintainable in a cost effective way. At this epoch, the engine should be replaced with a new one.