The Parkville grain train that derailed in 2016 was caused by a fractured yoke, an Australian Transport Safety Bureau report finds

On April 6, Pacific National 5422N train left Werris Creek and fell off the rails when a fractured yoke on the fifth wagon allowed the pin to fall out, and the coupler shank disengaged from the wagon.

The shank fell onto the tracks and ripped through the doors underneath the next ten carriages as they charged over it.

The driver told the network control officer he experienced a sudden loss of air from the train which led him to believe the train had derailed, an Australian Transport Safety Bureau report shows.

The second person on the train jumped out to do an inspection, and radioed the driver to say he could not see the remainder of the train.

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The detached wagons were eventually found and the handbrakes applied on all wagons, while the driver secured the locomotives and front wagons of the train.

An Australian Transport Safety Bureau report shows the 13^th wagon came off the rails and travelled 45 metres before coming to a stop – damaging a number of sleepers in its path.

Pacific National identified this kind of yoke was susceptible to fatigue failure, and had replaced the part across their entire grain wagon fleet – but the 5422N train that derailed in Parkville was overlooked.

These types of yokes were unable to withstand fatigue, according to Pacific National, and had been replaced across the fleet with higher tensile steel and rounded design to withstand high stress.

The pre-1980 design yoke that broke was not complaint with the Pacific National maintenance standard, the train was inspected but went back into service undetected.

It’s likely the yoke was the original yoke fitted to the wagon in 1971.

Both the driver and second person were drug and alcohol tested following the derailment and sent home from the rest of their shift – both returned a negative result.

The clean up began at 3pm, with the damaged wagons and spilled barley cleared from the site, the derailed wagons were then put back on the tracks.

The train was travelling from Werris Creek to the Carrington Grain Terminal near Newcastle on the Main North Line, at more than 600 metres long, weighing 3040 tonnes excluding the locomotives.

Since the incident, Pacific National has issued a notice to their maintenance teams mandating that all yokes in the grain wagon fleet be checked to ensure no other faulty yokes have remained in service.