The ageing of signalling equipment and the impact on maintenance strategy

Research projects of SNCF (French railway) aim at reducing the costs of infrastructure possessions and improving the operational equipment availability and safety. This permanent search for a better regularity led the SNCF to analyse the maintenance approach of signalling equipment in detail. Until now, it was commonly acknowledged that signalling equipment, which consists of many electronic devices, is not subject to ageing. In this study, Weibull and Bertholon lifetime model, able to describe an ageing phenomenon are used and they can be shown that the deterioration is statistically significant. The validity of the model is tested. We also analyse the influence of environmental covariates. We simulate different scenarios in order to investigate the impact of several maintenance strategies as well as on future maintenance costs, on the amount of components to replace based on the mean age of the network. It can be shown that in most cases a systematic replacement strategy offers the best solution. The tools developed allowed to treat all the electronic signaling devices to optimize their renewal strategy. The results give the SNCF the possibility to define new reliability requirements for the future signalling equipment.