Hierarchical maintenance policies based on two types of hazard rate functions

Hazard rate function (HRF) is always applied to make preventive maintenance (PM) decisions, and it is statistically estimated from failure time data. However, the classical HRF is not appropriate for systems under online monitoring, which is stopped to be checked and repaired when the monitored data exceed a predetermined threshold level. In this paper, based on two types of failure and corresponding two types of HRFs, two level checking and maintenance policy is constructed, which incorporates online monitoring and offline inspection. Finally, numerical examples are shown to verify the ideas of this paper.