Train derailment at a broken switch rail

Abstract

Two train rail elements at a switch location broke as part of a locomotive derailment. Preexisting cracks present in the elements most likely had developed as a result of wear in the switch system. The cracks were not the principal reason for the system failure, but they did define a plane of weakness. No other material defects were noted. The steel elements were severely deformed, but the final breaks included some brittle character, most likely a result of a high rate of loading during the incident. The rolling wheels were already outside of the constraints provided by the wheel flange and track configuration in order to cause the twisting and rolling deformation of the leading ends of the thin switch rails, which then led to breaking and separation of the pieces. Nondestructive examination was performed on an additional 199 switch rails. Cracks and/or linear indications were found on 27 switch points or switch point protectors. The flawed or damaged rails were removed, and spare rails that had passed the examination were substituted.