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Final Report

Summary

What happened

On 6 August 2015, TasRail northbound intermodal freight train 532, travelling from Boyer (near Hobart, Tasmania) to Burnie derailed on a section of track near Nala. The train consisted of two locomotives hauling 34 wagons. The train had an overall length of 557.8 m and a trailing mass 1,345.3 t. The driver was uninjured, but there was significant damage to rolling stock and about 200 m of track was destroyed.

What the ATSB found

The ATSB investigation determined that the leading wheelset on the front bogie of container wagon TQMF03G, derailed at the 95.185 km point south (kps). After the wagon derailed, the train travelled a further 2.3 km before it came to a stand.

Post-derailment measurements identified a series of track geometry defects in advance of the point of derailment (PoD). The largest defect exceeded safety limits specified in TasRail’s Track and Structure Maintenance Standard (INF-TS-211). A review of maintenance records found that a defect was identified (near the PoD) three days before the derailment. The defect was categorised as priority 1 requiring immediate attention, but did not result in the maintenance response specified by the standard.

The ATSB also identified that the track through the area had an elevated risk for geometry defects. Difficulty in maintaining track geometry through the area was probably related to poor track formation, ballast quality and the use of steel sleepers, which demand considerable maintenance effort to hold track alignment. However, there was no record of the track having been identified as a hazardous location, so it had not attracted greater analysis focus or maintenance attention.

Computer modelling showed that the TQMF wagons (compare to TQAY wagons) were more susceptible to derailment at a critical speed of 36 km/h, when traversing the track irregularity as existed at the derailment site.

What's been done as a result

TasRail have implemented a range of initiatives to reduce the risk of a similar occurrence including, changes to operational and maintenance procedures, enhanced strategies for responding to twist defects, and the consideration of fitting constant contact side bearers to the TQMF wagon fleet.

Safety message

Early detection, assessment and effective management of track defects are critical in minimising the risk of derailment and maintaining safe rail operations.

Derailed portion of train 532
Derailed portion of train 532
Source: ATSB

The occurrence

Context

Safety analysis

Findings

Safety actions

Sources and submissions

 
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