ESTIMATING PARAMETERS OF INTENSITY FUNCTION AND MAINTENANCE EFFECT FOR REPAIRABLE UNIT

A data-analytic procedure for successive inter-failure times (IFT) of repairable units is investigated. Specifically, a method of data analy sis for the estimation of parameters of the failure process and the ma intenance effect for repairable units is proposed. Malik's proportiona l age reduction (PAR) model for imperfect maintenance is utilized. The PAR model is reformulated in terms of the properties of non-homogeneo us Poisson processes (NHPP) with piecewise continuous intensity functi on. The joint distribution of the IFT's is also derived. Two parametri c families of intensity functions are considered, power-law and log-li near. Maximum likelihood method is employed to estimate the maintenanc e effect and the intensity function simultaneously, Two models are con sidered; one with effective corrective maintenance (CM) without preven tive maintenance (PM) and the other with effective PM with minimal CM. Simulation results are presented to illustrate the accuracy of the es timation and the properties of the models. An application example for a set of failure and maintenance data of a central cooler in a nuclear power plant is also presented. (C) 1996 Elsevier Science Limited.