On 11 August 2011, a scheduled Melbourne to Sydney Express Passenger Train (XPT) partially separated as it passed over a dip in the track near Broadmeadows, Victoria. The train suffered a total loss of power and was unable to continue its journey.
What the ATSB found
The ATSB found that the tail pin in the draft gear between the lead power car and first carriage failed as a result of a brittle overstress fracture that was initiated by fatigue cracking. Recent routine ultrasonic testing had not detected the presence of the fatigue crack and post incident material testing established that the mechanical properties of the tail pin were below the required standard.
Following this incident, the ultrasonic testing procedure was revised to improve the detection of smaller cracks in the tail pin. However, the separation of another XPT near Seymour, Victoria, on 1 August 2012 in similar circumstances highlighted the fact that the ultrasonic testing regime was still not detecting all small fatigue cracks in critical areas of the tail pin.
This investigation did not examine how the track irregularities near Broadmeadow may have contributed to the partial separation of train ST24, why the track condition deteriorated significantly in the 6 weeks between when it was last rehabilitated and the day of the partial separation or why the inspection and maintenance regimes in place at the time did not detect the deterioration in track conditions. These issues will be considered as part of the broader safety issue investigation RI-2011-015 Safety of rail operations on the interstate rail line between Melbourne and Sydney.
What's been done as a result
A new batch of tail pins has been manufactured to an upgraded standard which includes improved quality control and acceptance testing and RailCorp, the operator of the XPT fleet, is currently in the process of fitting these new tail pins. RailCorp has also further revised the tail pin inspection regime with the aim of improving its effectiveness.
It is important that components are fit for purpose and meet the appropriate requirements for service and that inspection regimes are effective in providing assurance of continuing equipment reliability.