Risk assessments need to consider compressive rail stress

The derailment of a loaded coal train between Emerald and Rockhampton in Queensland in January 2018 highlights the need for track managers to develop, maintain and consult network hazard registers to identify locations at risk of buckling due to compressive rail stress, according to a new ATSB investigation.   

Derailment of a loaded coal train between Emerald and Rockhampton in Queensland

The day before the derailment, the affected track had been subject to ballast-cleaning operations. The track was then tamped, aligned, and stabilised, with a second and final pass of this work taking place the next morning.

That afternoon, as the nearly 2 km long train EF01 was descending a steep grade, the driver noticed a track buckle forming ahead of the train. After applying emergency braking the train came to a halt 65 seconds after the lead locomotive had passed over the track buckle.

The first wagon to derail travelled for over half a kilometre before the train stopped. Of the 17 wagons that derailed, 13 were extensively damaged and unlikely to be repaired. Just over half a kilometre of track on the down line and 54 m of track on the adjacent up line was damaged, with rails, sleepers and overhead line equipment needing replacement.

This investigation highlight the importance of developing, maintaining and consulting a network hazard register to identify locations at risk of buckling, and producing site-specific risk assessments that consider rail stress when planning track disturbing maintenance work.

The ATSB determined the accumulative effect of the track’s steep grade, with its proximity to a turnout and a high ambient temperature lead to the track to buckle. The ATSB also found the ballast cleaning operational plan did not consider compressive rail stress as a risk at this location.

”This investigation highlights the importance of developing, maintaining and consulting a network hazard register to identify locations at risk of buckling, and producing site-specific risk assessments that consider rail stress when planning track disturbing maintenance work,” said ATSB Director Transport Safety Dr Stuart Godley

“The accident also demonstrates that effective rail stress management is dependent on a knowledge of the rail stress free temperature and the identification of any variations from that stress free temperature.”

As a result of the accident, track manager Aurizon Network has changed its procedures to ensure a temporary speed restriction is applied to all work sites on which ballast undercutting has been performed. The restriction is to remain in place until rail adjustment or stress testing has been completed and it has been determined that the rail stresses are within accepted limits.

In addition, sites with a high risk of compressive rail stress will be identified and added to the site hazard map before conducting ballast cleaning.

Read the final report RO-2018-005: Derailment of coal train EF01, Duaringa, Queensland, on 24 January 2018

Last update 28 June 2019