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Derailment warning not spotted

NZ NewswireNZ Newswire 13/04/2016

Advanced acoustic equipment picked up problems with a railway wagon 20 times in the days before it derailed but the technology was so new KiwiRail didn't recognise there might be a problem, an investigation has found.

The Transport Accident Investigation Commission has released its report into the derailment of two wagons, part of a freight train carrying hazardous goods, at Mercer, south of Auckland, in September 2013.

One wagon spilled its contents onto State Highway 1 and the other fell onto the other set of tracks.

The report says things could have been much worse but the accident happened at 40km/h hour and the 3am time meant there was little traffic on the road.

A failed wheel bearing, which was completely destroyed, caused the derailment.

The TAIC report noted KiwiRail should have been alerted to a problem because of the number of times the brakes had been replaced. A binding brake can heat the wheel which transfers the heat to the bearings.

TAIC said there was a lesson to be learned about properly introducing new technology so staff knew what to look for.

In 2012 KiwiRail finished installing three RailBAM (bearing acoustic monitor) systems, near Christchurch, Tauranga and Palmerston North.

The system listens to passing trains and can acoustically detect the signature sounds of a problem bearing.

In the 23 days before the derailment, the RailBAM near Tauranga generated 20 fault records for the wheelset which failed.

However, nothing was done because KiwiRail staff didn't believe the noise reached the threshold for concern.

Since the accident, KiwiRail has created a dedicated position of RailBAM analyst.

TAIC noted that 90 per cent of wagons now pass RailBAM sites regularly and annual derailments had dropped from 55 to seven over 10 years.

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