Imperfect Preventive Maintenance Policy of Deteriorating Systems Based on Failure Limit

Maintenance problems of deteriorating systems have been studied in the past several decades. Since most systems after maintenance are somewhere between as good as new and as bad as old, this paper developed Kijima's virtual age model to describe the imperfect preventive maintenance. A new improvement factor was proposed to evaluate the age restoration after the maintenance, which was the function of the system's age and the preventive maintenance cost rate. Life of the system was assumed to follow two parameters Weibull distribution since it was one of the most commonly adopted distributions to fit cumulative failure problems. Two models were given in this paper. By minimizing the maintenance cost rate, the optimal maintenance time interval was obtained. The numerical example show the benefits of the model based on failure limit policy, which can also provide decision support for the operation.