Abstract: Aiming at the problem that the traditional sequential maintenance strategy is difficult to operate in practice, a phased sequential maintenance model of the equipment is proposed. In order to make the sequential maintenance strategy more operational in practice, the maintenance process of the equipment is divided into three stages, and the maintenance interval of each stage is equal. After three stages of maintenance, the preventive replacement of the equipment is carried out. The mixed failure rate function of service life improvement factor and failure rate increasing factor are used to describe the degradation process of the equipment. Considering the sudden failure cost, preventive maintenance cost, replacement cost and shutdown loss cost in the maintenance period, and the equipment reliability is not lower than a certain level, the optimization objective is to minimize the total maintenance cost rate in the maintenance period. In this model, the maintenance interval and maintenance times of three stages are solved by nonlinear constraint optimization tool. An example shows that the maintenance cost can be reduced by about 15%, which verifies the effectiveness of the model.

Key words: sequential maintenance, reliability constraint, mixed failure rate, maintenance interval, maintenance times