Comparative Research On Delay-Time-Based Inspection Models In Case Of Non-Homogeneous Defect Arrival Rate

This paper is mainly concerned on problems of revising the basic inspection model and optimizing the preventive maintenance interval of equipment in the case of the Non-Homogeneous Poisson Process (NHPP) of defect arrivals and non-negligible failure downtime. Firstly, the concept of delay time and its maintenance theory are introduced, and then a basic inspection model for complex system is established using delay time maintenance theory. In modeling this inspection model, it is based on the case that failure downtime is short compared to inspection cycle, and the case of Homogeneous Poisson Process(HPP) of defect arrivals, therefore, assuming that defects arriving in HPP continue to arise during failure downtime. Obviously, this assumption is not suit to the case that failure downtime is not sufficiently small and the case of NHPP of defect arrivals. So this paper assumes that defects arriving in NHPP only occurred in operation time of equipment, the basic inspection model is revised, the expected number of failures over inspection cycle is given by the revised inspection model. Finally, a case study is also proposed to highlight the differences. The revised downtime model is a more sensitive model with which to determine the actual downtime and optimal inspection interval.