The derailment of a 1953-built Drewry locomotive near Teepookana, Tasmania, was caused by an under-lubricated axle box horn guide, according to a new report.
On December 9, 2014, locomotive 71SG travelled from Regatta Point to Dubbil Barril, to collect an empty passenger carriage for transfer back to Regatta Point.
The train’s operator, West Coast Wilderness Railway, was collecting the empty carriage in preparations for the planned commencement of passenger services along the line on December 15, 2014.
The 27 tonne, 7.6 metre locomotive left Dubbil Barril with the empty carriage in tow at around 11:36am on December 9. Roughly 40 minutes later, the train’s crew radioed in to report the locomotive had derailed all wheels.
One member of the three-person crew suffered minor injuries, described by the Australian Transport Safety Bureau (ATSB) as bruising and stiffness. Damage to the locomotive was described as minor, and the empty passenger carriage remained on the track.
An investigation by West Coast Wilderness Railway found the track condition and geometry did not contribute to the incident. Crew interviews and a review of the damage done ruled out the possibility that the train was exceeding the enforced 10km/h speed limit on the historic line.
Instead, mechanical examination of the locomotive found the cause of derailment to be the front-right-hand axle box horn guide, which had jammed due to a lack of lubrication.
“The jammed horn guide had restricted axle articulation while the locomotive was negotiating a slight left-hand curve, causing the leading wheel on the right side to climb the rail head and derail to the right,” the ATSB reported on April 8.
West Coast Wilderness Railway operates three diesel locomotives like Train 71SG, and uses them primarily for shunting as well as the occasional freight service.
While the locomotives receive regular maintenance, the ATSB found they can spend long periods idle, often outside, thus exposing them to “the harsh environment of Tasmania’s west coast.”
As a result of the investigation, West Coast Wilderness Railway has advised the ATSB that it will investigate its examination and recording methods, as well as the possibility of improving the lubricating delivery message for its machines.
“This incident highlights to operators and maintainers the importance of continually monitoring and reassessing risks to the safe operation of rolling stock,” the bureau concluded, “particularly with respect to low utilisation operating scenarios.”