Reliability Calculation for Dormant k-out-of-n Systems with Periodic Maintenance

Abstract

In this paper, a dormant k-out-of-n systems redundancy calculation will be introduced. Dormant failure is a failure that cannot be detected when it occurs because of the nature of the failure characteristic. Therefore, a dormant failure becomes the blind point to the design for reliability and maintainability because of its inability to be detected. The most popular approach in detecting a dormant failure is to carry out a scheduled periodic inspection, test or maintenance activity. The scheduled periodic maintenance is applied to prevent and reduce the unexpected dormant failures that could lead to safety consequences, or costly corrective maintenance. This paper will introduce a methodology on how to calculate the reliability parameter such as Mean Time Between Failure (MTBF) for the dormant k-out-of-n redundant systems. The mathematical relationship between the effective MTBF and the scheduled periodic inspection/maintenance interval is also elaborated. Case studies are adopted to illustrate how to apply the developed reliability calculation methodology in the mass transit train reliability and safety design.