Rail Safety Investigation - Defective axle bearing leading to fire on passenger train SN68 - Yerrinbool - 13 October 2020

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What happened

On 13 October 2020, TrainLink passenger service SN68, was operating from Moss Vale to Campbelltown, NSW with approximately 20 passengers on board.

The train driver stopped the train at Yerrinbool Station after being alerted to a small fire at the rear of the train. The fire was identified as coming from the vicinity of an axle bearing on the rear wheelset of the train.

The passengers were evacuated onto the platform and the driver attempted to extinguish the fire using an on-board fire extinguisher.

The fire was subsequently extinguished by Fire and Rescue NSW. As a result of the fire, parts of the axle box were heat affected and sustained significant damage to the speed sensor and rubber suspension components.

There were no reported injuries.

What we found

The investigation determined that the fire was the result of a collapsed axle bearing on wheel 8 on the trailing bogie on car 2811, the end of the train.

The axle bearing failed when the axle end cap bolts loosened and one fractured which caused the collapse of the bearing and frictional heat to be generated. The resulting fire was fuelled by grease, oil and rubber suspension components in the immediate vicinity of the axle box.

It is likely that during the last overhaul of bogie NJA31, the locking plate tabs retaining the axle end cap bolts were not fitted correctly against the sides of the bolts. The axle bearing installation process was not sufficient to ensure the tabs on the locking plate were installed correctly during a refurbishment three months before the incident. A wayside monitoring system at Burradoo on the Down Main line detected an elevated temperature on one bearing, but the temperature recorded was below the threshold for an alarm to be sent to network control.

What has been done as a result

Following the occurrence Sydney Trains, which is the maintenance provider for NSW Trains, initiated an inspection of similar axle boxes in the fleet and undertook an audit of the contracted maintainer’s practices.

Sydney Trains have advised the following actions have taken place to prevent a recurrence:

• improvements have been made to the contracted maintainer’s quality assurance processes to ensure that bolts and locking tabs are correctly installed
• an improved process was implemented to review and retain the contracted maintainer’s certificate of completion checklists.

Safety messages

Bearing failures continue to occur within the Australian rail network.

This occurrence emphasises the significance of having adequate bearing installation processes and ensuring that axle bearings are correctly maintained and monitored throughout their operational life.