Optimization of Maintenance Schedule for Safety Instrumented Systems

Abstract Preventive maintenance plays an important role in the reliability of safety instrumented systems (SIS). In this paper, an approach is proposed for the optimization of maintenance schedule of SIS. The basic idea is to regard a SIS with preventive maintenance tests as a switched linear system with state jumps. Then the problem of finding the optimal time instants for maintenance tests is formulated as an optimal control problem of Bolza form. The average probability of failure on demand (PFD) is taken as the objective function. The proposed approach is able to take into account different types of maintenance tests and redundancy architecture. Examples are given to illustrate the proposed approach.