Reliability and risk in the safe operation of a rail vehicle subsystem

This study highlights the problem of modernisation using a practical example of a rail vehicle pivot and constitutes an analysis of the impact of preventive renewals on the reliability of the upgraded structural node. The damage that occurs to the rubber vibration damper and, as a consequence, to the pivot itself, is a dependent failure. The developed model takes into account the random nature of the values of the operating times to failure of the pivot and the vibration damper cooperating with it, as well as the damage relationship between them. The model also includes preventive renewals of the vibration damper performed at fixed intervals of the vehicle's mileage, as well as information on its technical condition derived from inspections performed at shorter mileage intervals. As the analysis of the risk of damage to the pivot system has shown, changing the preventive renewal period of the vibration damper makes it possible to seek an acceptable risk value for the operator and to achieve the required safety integrity level (SIL).