Final Report

Summary

What happened

On 6 April 2016, Pacific National (PN) grain train 5422N parted at Parkville on the Main North Line. A fractured yoke on the trailing end of the fifth wagon allowed the yoke pin to fall out and the coupler shank to disengage from the wagon. The coupler shank fell into the four foot of the track and damaged the underbelly discharge doors on 10 wagons as the train progressed over the coupler. Approximately 10 tonnes of barley was released from the wagons as a result. The trailing wheelset on the thirteenth wagon was derailed, then ran in a derailed state for approximately 45 metres causing damage to several track sleepers before the train came to a stop. Regular services were able to continue under caution past the incident site via the adjacent crossing loop. Wagon recovery and track repairs was completed without any further incident.

What the ATSB found

A draftgear component (the yoke), that was not compliant with a PN maintenance standard, was not identified during a maintenance inspection and re-entered service undetected. The yoke was an earlier design and susceptible to fatigue failure. PN had identified the issue and completed a programme to replace this yoke design across their grain wagon fleet however, the yoke on this wagon had been overlooked.

What's been done as a result

PN issued an additional Rolling Stock Notice to their maintenance teams to advise of the incident and to mandate that all yokes in the grain wagon fleet were checked to ensure no yoke of this design remained in service.

Safety message

Maintenance systems must ensure that when a non-compliant component is identified as needing replacement, all such units are located and replaced.

Figure 1: 5422N at Parkville

Figure 1: 5422N at Parkville. Source: ATSB

Source: ATSB

The occurrence

Context

Safety analysis

Findings

Safety issues and actions

Sources and submissions

Appendices