Reliability optimization problem with the mixed strategy, degrading components, and a periodic inspection and maintenance policy

Redundant components stored in the standby mode degrade over time due to harsh environmental conditions. A proper inspection and maintenance plan is, therefore, required to combat performance degradation while maintaining system reliability. The present study presents a new reliability model for a system composed of simultaneously active and standby components with the standby ones prone to degradation. In this model, a periodic inspection and preventive maintenance policy is adopted for the standby components that needs to be duly scheduled. Thus, not only should the optimal component types be identified but the number of active and standby components in each subsystem needs to be determined as well. The objective function is to find optimal inspection intervals that ensure maximum system reliability with system constraints duly considered. For this purpose, a model is proposed for the problem at hand and a genetic algorithm is developed for its solution. Finally, a numerical example and an industrial case study are presented to verify the efficiency of the proposed model through sensitivity analysis in the presence and absence of the inspection policy.