Optimization of Non-Periodic Preventive Maintenance Cost in Series-Parallel Systems Using Importance Measures of Components

Abstract

This study aims to construct an optimization algorithm to solve the non-periodic preventive maintenance (PM) model of a series-parallel system. The failure limit policy is employed to perform PM. Under such policy, the maintenance components and their maintenance times are determined to minimize total maintenance cost. From the viewpoints of maintenance, the constructed optimization algorithm evaluates the extent to which maintaining components benefit the series-parallel systems. Furthermore, due to some drawbacks or limitations for past developed importance measures, two importance measures of components including the unit-cost mean time to failure (UCMTTF) and the unit-cost extended life (UCEL) are developed to facilitate determining the maintenance policy. The UCMTTF measure mainly evaluates the extent to which maintaining a component extends MTTF for sub-parallel systems. While the UCEL measure mainly evaluates the extent to which maintaining components improve the UCEL for the series-parallel system. On the basis of UCMTTF and UCEL measures, this study constructs an optimization algorithm to minimize total maintenance cost subject to a threshold value of system reliability for the non-periodic PM model in a series-parallel system. Three simulated cases demonstrate the effectiveness and the practicality of the proposed method in optimizing the non-periodic PM model of a series-parallel system.