Preliminary report published: 20 June 2018
At approximately 0015 on 21 April 2018, Pacific National intermodal freight train 6MP4 derailed between Mt Lofty and Belair, South Australia. Train 6MP4 was travelling from Melbourne, Victoria via Adelaide, South Australia to Perth, Western Australia. Train 6MP4 was approximately 1,499 m long with a trailing weight of 2,853 t, and consisted of three locomotives and 26 single and multi-platform wagons.
The train crew reported that apart from a level crossing near miss with a vehicle forcing an emergency stop near Lillimur, Victoria, the journey towards Mt Lofty was uneventful. At approximately 2358 on 20 April 2018, 6MP4 passed Mt Lofty, South Australia and commenced travel on the downhill grade towards Belair (Figure 1).
Image shows ARTC track from Mount Lofty Railway Station to Glenalta Railway Station in green, with red markers for km points, and 6MP4 stopped position of both portions in yellow. A red star marker indicates the initial point of derailment, and key wagon debris / track evidence indicated with a white marker. Source: Google Earth annotated by ATSB
Multi-platform 5-pack wagon RRYY01X was the eighth wagon behind the locomotives. At approximately the 28.6 km point (Figure 1), the trailing axle from the bogie shared between platform 2 and 3 derailed. The axle continued in a derailed state for a further 1.58 km, making intermittent contact with the ground, track fastenings and sleepers.
At the 27.02 km point, components underneath the derailed bogie collided heavily with a concrete sleeper dislodging the constant contact side bearer pads and breaking the centering bogie pin (Figure 2). The collision moved the bogie towards the rear of the train fouling with the leading end structure of platform 3 (wagon RRYY01X). The derailed rear axle travelled for a further 3.96 km making more frequent contact with the ground, track fastenings and sleepers.
As the derailed bogie passed over 20 Points at the entrance to the Belair crossing loop (23.06 km point - Figure 1), components underneath the derailed bogie collided with components of 20 points. About 10 m later, the derailed axle re-railed at the V-crossing for the crossing loop. The collision with the points components and the axle re-railing likely dislodged the coupler pin (Figure 2) allowing platforms 2 and 3 (wagon RRYY01X) to uncouple and separate.
Image shows an intact combined wagon coupler pin and centre bogie pin from a RRYY class wagon, alongside the wagon coupler pin from wagon RRYY01X with missing bogie centre pin. Source: ATSB Annotated.
Separation of the two platforms resulted in breaking of the brake air pipe, which automatically applied the train brakes and brought both portions of train 6MP4 to a stop. The leading end of the front portion of 6MP4 stopped at approximately the 19.7 km point near Glenalta, and the leading end of the rear portion of the split 6MP4 stopped at the 20.84 km point (Figure 3). The front and rear portions of the split train 6MP4 were separated by approximately 450 m.
Image shows ARTC track in green, with red markers for km points, and 6MP4 stopped position of both portions in yellow. Source: Google Earth annotated by ATSB
There was substantial damage to a bogie and two platforms from 5-pack wagon RRYY01X (Figure 4), plus minor damage to rail infrastructure. There were no injuries reported.
Image shows the final position of the bogie involved in derailment with platform 2 and 3, after train 6MP4 came to a stop near Glenalta. Source: Wagon drawing - Pacific National annotated by ATSB, and photos - ATSB.
Post derailment inspection identified an underframe structural failure within platform 2 of RRYY01X 5-pack wagon. The failure originated from a crack between the join of the bottom centre sill plate and pull rod opening in the wagon’s underframe (Figure 5).
Image shows underframe cracks and their location in platform 2 of 5-pack wagon RRYY01X. The underframe cracks and derailed bogie were located at the trailing end of platform 2 of 5-pack wagon RRYY01X. Source: Wagon drawing - Pacific National annotated by ATSB, and photos - ATSB.
Following this incident, Pacific National issued a Rolling Stock Notice in relation to its RRYY class wagon fleet. The notice required that:
- all RRYY class wagons are inspected for underframe cracking
- all RRYY class wagons exhibiting any cracking around the underframe to be red carded for repairs
- magnetic particle inspection or dye penetrant inspection of welded connections is to be conducted during scheduled preventative maintenance
- a fleet assessment of RRYY class wagons is to be undertaken.
The ATSB investigation is continuing, and will include the following:
- gathering further information from involved parties
- examination of wagon RRYY01X
- examination of inspection and maintenance processes, and historical records relating to RRYY class wagons
- review of train loading and examination processes with respect to RRYY class wagons.
The information contained in this preliminary report is released in accordance with section 25 of the Transport Safety Investigation Act 2003 and is derived from the initial investigation of the occurrence. Readers are cautioned that new evidence will become available as the investigation progresses that will enhance the ATSB's understanding of the accident as outlined in this web update. As such, no analysis or findings are included in this update.
- CST – Central Standard Time, UTC +9.5hrs.
- The downhill grade between Mt Lofty and Belair varies between 1:45 and 1:48.
- 5 Pack – Refers to an articulated wagon comprising five platforms, with the adjacent ends of individual units being supported on a common bogie and permanently connected by a device, which permits free rotation in all planes. Source: RISSB Glossary of Railway Terminology, Version 1 dated 3 December 2010.
- V-Crossing – A track component that enables a wheel travelling along one rail to pass through the rail of a track which crosses its path. Source: RISSB Glossary of Railway Terminology, Version 1 dated 3 December 2010.
- Coupler pin – In the case of a RRYY class 5-pack wagon, the pin used to couple two platforms of a 5-pack wagon together. Note: the centring pin and coupling pin are joined to each other in a RRYY class wagon.
- Rolling Stock Notice – A Pacific National publication advertising changes to, details of, and new requirements related to Pacific National rolling stock.
- Red card – A card placed in the waybill clip of a wagon to notify all concerned that the particular vehicle is NOT fit for traffic and must be repaired prior to returning to traffic. Source: RISSB Glossary of Railway Terminology, Version 1 dated 3 December 2010.