Optimization of On-condition Thresholds for a System of Degrading Components with Competing Dependent Failure Processes

TL;DR

This paper develops an optimization model to determine the best on-condition failure thresholds and inspection schedules for systems with multiple degrading components experiencing dependent failure processes, aiming to minimize costs and prevent failures.

Contribution

It introduces a novel optimization framework for on-condition maintenance of multi-component systems with dependent degradation and failure processes, considering cost-effective thresholds and inspection intervals.

Findings

Optimal thresholds effectively prevent costly failures.

Trade-offs between threshold levels and component lifespan are identified.

Model demonstrated on multiple example systems.

Abstract

An optimization model has been formulated and solved to determine on-condition failure thresholds and inspection intervals for multi-component systems with each component experiencing multiple failure processes due to simultaneous exposure to degradation and shock loads. In this new model, we consider on-condition maintenance optimization for systems of degrading components, which offers cost benefits over time-based preventive maintenance or replace-on-failure policies. For systems of degrading components, this can be a particularly difficult problem because of the dependent degradation and dependent failure times. In previous research, preventive maintenance and periodic inspection models have been considered; however, for systems whose costs due to failure are high, it is prudent to avoid the event of failure, i.e., we should repair or replace the components or system before the failure happens. The determination of optimal on-condition thresholds for all components is effective to avoid failure and to minimize cost. Low on-condition thresholds can be inefficient because they waste components life, and high on-condition thresholds are risky because the components are prone to costly failure. In this paper, we formulated and solved a new optimization model to determine optimal on-condition thresholds and inspection intervals. In our model, when the system is inspected, all components are inspected at that time. An inspection interval may be optimal for one component, but might be undesirable for another component, so the optimization requires a compromise. The on-condition maintenance optimization model is demonstrated on several examples.