Investigation of a Bridge Crane Derailment with Limited Subject Parts

Abstract

A derailment investigation of a large capacity overhead bridge crane was conducted based upon the only accessible and remaining physical evidence, a separated wheel flange. A metallurgical evaluation limited to visual examination and optical microscopy of the separated wheel flange in conjunction with 3D modeling based upon nominal track and wheel dimensions confirmed that the root cause of the crane derailment was the result of aggressive operation. The wheel fracture contained fracture morphology, indicating that a crack initiated at the interface between the wheel tread and the flange as a result of impact loading with the side of the rail head. After initiation, the crack at the base of the flange propagated as a result of repeated loading events. Having progressed to a critical crack length, the compromised wheel flange was driven into the rail, bending the flange outward resulting in the observed wear groove that matched the gauge corner of the crane rail. The flange eventually separated from the wheel resulting in a derailment. Utilizing scene documentation and information provided by both the crane operator and crane manufacturer, it was possible to determine that operation of the crane resulted in heavy loading events necessary to initiate cracking at the base of the wheel flange.