1984 Volume 10 Issue 4 Pages 499-505
The purpose of this study is to propose a maintenance schedule method based on condition to decide optimum starting point of diagnosis of parts in periodical scheduled maintenance.
In this study, the mechanical fault diagnosis model is used to obtain the optimum maintenance schedule of parts in operation stage. The model assumes that each part has two failure stages. The first stage of failure is an occurrence of symptoms such as malfunction, small crack and many other defects. The second stage of failure causes the occurrence of catastrophic disaster in plant units. In addition, detection time of symptoms and repair time of parts are considered in this model. The optimum schedule is obtained by minimizing the sum of the costs of maintenance and expected disaster damage under tolerable risk using the proposed model.
In a numerical example, two-parameter gamma distribution failure models having different shape parameters from each other at two stages are treated for one part, and a two-parameter gamma distribution is used for the probability density function of both detection time and repair time. The results show that this maintenance model has a trade-off relation between maintenance cost and expected disaster damage cost. Useful methods of optimizing the maintenance schedule and minimizing the total cost are shown in the periodical scheduled maintenance period.