Reliability-Centered Maintenance of the Electrically Insulated Railway Joint via Fault Tree Analysis: A Practical Experience Report

Maintenance is an important way to increase system dependability: timely inspections, repairs and renewals can significantly increase a system's reliability, availability and life time. At the same time, maintenance incurs costs and planned downtime. Thus, good maintenance planning has to balance between these factors. In this paper, we study the effect of different maintenance strategies on the electrically insulated railway joint (EI-joint), a critical asset in railroad tracks for train detection, and a relative frequent cause for train disruptions. Together with experts in maintenance engineering, we have modeled the EI-joint as a fault maintenance tree (FMT), i.e. a fault tree augmented with maintenance aspects. We show how complex maintenance concepts, such as condition-based maintenance with periodic inspections, are naturally modeled by FMTs, and how several key performance indicators, such as the system reliability, number of failures, and costs, can be analysed. The faithfulness of quantitative analyses heavily depend on the accuracy of the parameter values in the models. Here, we have been in the unique situation that extensive data could be collected, both from incident registration databases, as well as from interviews with domain experts from several companies. This made that we could construct a model that faithfully predicts the expected number of failures at system level. Our analysis shows that that the current maintenance policy is close to cost-optimal. It is possible to increase joint reliability, e.g. by performing more inspections, but the additional maintenance costs outweigh the reduced cost of failures.