FMEA, monitoring, retrofit and redesign of insulated rail joints

Abstract

Insulated rail joints (IRJ) are a fundamental component of railway signalling that ensure train protection using “track circuits”. A track circuit is a section of line delimited by rail joints electrically insulated, powered at one end with an electric power supply to establish a different voltage that is checked at the other end with a so-called “track circuit relay”. When the section is short-circuited by an axle the relay drops, and the section is defined as “occupied”. IRJ are subjected to continuous and dangerous failures as they represent a singularity in the rail continuity. Continuous battering produces the classical train impact noise while damage in the rail accumulates until the IRJ fails with extremely unpleasant consequences. The paper discusses the main failure modes of an IRJ starting from a historical perspective, showing how an appropriate failure analysis would have prevented a catastrophic accident that recently occurred in Italy. Several countermeasures are shown and a completely new IRJ potentially completely solving the issue is introduced.