Case study Railway signal wire insulation investigations and monitoring of degradation undertaken by London Underground

Abstract

Signalling systems on London Underground date from the 1940s onwards and consequently a wide range of polymeric insulated wire and cable is present. The investigations reported centre on the chlorinated diene rubber insulation surrounded by a lacquered glass braid used on earlier vital signalling equipment. Results of accelerated aging tests at 100°C have been combined with observations of degradation in service in an Arrhenius type analysis. This permits the lifetime of insulation in given time-temperature conditions to be estimated.