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What happened

On 14 May 2014, train 4413 – a bulk iron ore service operated by Aurizon, derailed on the Defined Interstate Rail Network (DIRN) between Stewart and Bonnie Vale, about 54 km west of Kalgoorlie in Western Australia. As a result of the derailment there was significant damage to track and rolling stock. There were no injuries.

What the ATSB found

The ATSB determined that the derailment of train 4413 was most likely initiated by lateral harmonic vehicle oscillation induced by a combination of minor cyclic cross-level and lateral track irregularities just in advance of the point of derailment. As a result of these irregularities, it was likely that the roll of wagon WOE33548K caused the left hand wheels to unload at a time when the leading left wheel came into contact with the left rail face – resulting in flange climb and derailment.

While the wagon type that derailed (WOE class) had passed prescribed dynamic performance testing, and the wagons and track complied with mandated engineering requirements, post-derailment computer modelling showed the onset of lateral harmonic wagon oscillation of sufficient magnitude to increase the likelihood of derailment at this location. Simulations showed that iron ore wagons, with their short length, react more severely to 22 m wavelength cyclic irregularities (as evident at this site) than do the typically longer intermodal wagons. The ATSB concluded that undertaking computer modelling when changing rolling stock and/or track working conditions offers rail transport operators an opportunity to identify potential areas of risk exposure before implementing new service arrangements.

Track maintenance and inspection was found to be in compliance with engineering requirements, however the track leading into the derailment site was known (to train drivers) as an area of rough ride. It was found that the systems in place between the train operator and track maintainer for the reporting of track irregularities (in particular the rough riding of trains) was ineffective, and hence the opportunity was lost to check for uncharacteristic track qualities through the derailment site – before such qualities contributed to a derailment.

While not influencing the derailment, it was noted that the loss of the train’s brake pipe integrity (loss of air), including activation of the end-of-train monitor, had not resulted in the immediate and full automatic activation of the train brake.

What's been done as a result

Brookfield Rail and Aurizon have developed enhanced procedures for reporting track irregularities and have jointly committed, through the Rail Industry Safety and Standards Board, to ongoing industry support and research into the cause of this type of derailment. Aurizon is examining, with the intent of rectifying, the train braking irregularity (brakes not activating) that occurred following the loss of brake pipe integrity.

Safety message

To reduce the potential for unforeseen dynamic stability issues affecting the safety of rolling stock operations, it is essential that train operators and track maintainers:

Appropriately test and model rolling stock dynamic characteristics and the effects of changed track conditions before implementing new service arrangements.

Develop proactive interface management strategies that promote the prompt reporting, capture and feedback of uncharacteristic track qualities.

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The occurrence

Context

Safety analysis

Findings

Safety issues and actions

Sources and submissions

 
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Preliminary report release 28 August 2014

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 Preliminary report. As such, no analysis or findings are included in this report.

The occurrence

At 0100[1] on 14 May 2014, train 3416, a scheduled bulk iron ore service, departed from the Binduli Triangle (650 km[2]), Western Australia, for Koolyanobbing East (458 km). The train, crewed by two drivers,[3] travelled empty to Koolyanobbing East.

On arrival at Koolyanobbing East, the train was loaded with iron ore and made ready for departure as train 4413. At 0755, it departed Koolyanobbing East for the port of Esperance.

En route, train 4413 crossed with the Prospector passenger train at Beckwith (470 km) and then with train 3033 at Mount Walton (534 km). It continued on its journey towards Esperance, stopping at the Wallaroo loop (562 km) to cross with empty ore train 4414.

Figure 1: Location map – Western Australia

RO-2014-008_Fig1
Source: NatMap Railways of Australia

 

 At 1010, train 4413 departed the Wallaroo loop. The passage of the train through to Stewart (587 km) was uneventful. As the train entered the Stewart to Bonnie Vale section, the driver gradually accelerated towards 90 km/h, the maximum permitted track speed for ore trains in this section. From the 596 km to 599 km mark the track descended slightly. To limit the train from exceeding 90 km/h, the driver put the train into light dynamic braking,[4] to maintain a speed of about 85 km/h.

At about 1048, just after traversing a culvert at 600.657 km, the locomotive shuddered. The train travelled a further 600 m when the driver felt a series of jerks of increasing severity throughout the train. Almost immediately, he observed that the end-of-train monitor[5] was showing a zero reading. He did not observe a decrease in the train’s brake pipe pressure or hear any audible alarm which would normally accompany a train parting event.[6]

The driver looked back in the rear vision mirror and observed clouds of dust and realised that the rear portion of the train had probably derailed. He slowed the train, bringing it to a stand about 3 km beyond the initial point of derailment (PoD). He then advised the train controller that the train was at stop within the Stewart to Bonnie Vale section, had probably derailed and that the second driver was going back to investigate.

Figure 2: Train 4413 End of Train – Derailed Ore Wagons

RO-2013-021_Fig2
Source: ATSB

Events post derailment

The second driver walked towards the rear of the train and progressively reported to the driver the extent of the derailment and associated damage (Figure 2). The driver relayed the information to the train controller.

The Stewart to Bonnie Vale section was subsequently closed and recovery personnel were dispatched from Kalgoorlie. The two drivers were also relieved and returned to Kalgoorlie.

On 15 May, track and train maintenance crews commenced recovery and restoration works. The track was re-opened to traffic on 17 May.

Context

Location

The derailment occurred between Stewart and Bonnie Vale, about 54 km west of Kalgoorlie, at 600.729 km on the Defined Interstate Rail Network (DIRN) in Western Australia (Figure 1). The DIRN through this area runs in an east-west direction and links Western Australia with the eastern States.

Environmental conditions

The environmental conditions leading up to the incident were not considered exceptional and were unlikely to have contributed to the derailment.

Train and train crew information

Train 4413 was a regular Aurizon iron ore service that operated between Esperance and Koolyanobbing East. The train was configured as a distributed power unit[7] (DPU) and comprised two locomotives at the head of the train (AC4301 leading and ACB4404 trailing) followed by 106 wagons then two locomotives mid-section (Q4017 leading and AC4304 trailing) followed by a further 54 wagons. The train had an overall length of 1,792 m and a gross mass 14,731 t.

Rolling stock

Examination of the derailed wagons primarily focused on wagon WOE33548K, which was considered as the first wagon to have derailed. It was evident that the leading wheel-set of its lead bogie had derailed to the left (in the direction of travel) and had travelled about 2.5 km past the PoD.

The wagon was examined by the ATSB both on site and at Aurizon’s West Kalgoorlie maintenance facilities and found to be in compliance with maintenance specifications and operationally fit for purpose.

The ATSB concluded that there was no obvious indication of any mechanical deficiency with the train that may have contributed to the derailment. However, post derailment braking performance requires further examination because the available evidence indicates that the loss of brake pipe integrity (loss of air) did not result in immediate brake activation.

Train crew

The train crew comprised two drivers. The driver at the time of the derailment had about 14 years train driving experience. The second driver had 9 years train driving experience. Both drivers held the required qualifications to operate the train, were route certified and assessed as medically fit for duty.

Following the derailment both drivers underwent mandatory drug and alcohol testing, the results of which were negative. The available evidence also indicates that the performance of the drivers was not affected by fatigue.

Track Information

The track from Koolyanobbing East through to West Kalgoorlie substantially comprised a single line (bi-directionally signalled) with crossing loops strategically located throughout its length.

The track through the derailment site was standard gauge (1,435 mm) and consisted of 60 kg/m continuously welded rail[8] (CWR). The rail was fixed to concrete sleepers at approximately 667 mm spacing and secured by resilient fastenings.[9] It was supported on a bed of ballast having a nominal depth of 300 mm under the sleepers. The track had been relayed with new 60 kg/m rail about 1 year earlier.

The track leading into the derailment site was straight (tangent track) with a slight downgrade of about 0.2% in the direction of travel.

Track condition

An examination of the track at the PoD showed evidence of flange climb on the left side running rail (direction of travel) and witness marks over a distance of about 5 m which indicated that the wheel flange crossed over the rail head (Figure 3).

Figure 3:   Witness marks caused by a wheel flange at PoD (600.729 km) shown by line of stones on rail head

 RO-2014-008_Fig3

Source: ATSB

Damage to sleepers was observed only after the point where the wheel(s) subsequently dropped off the rail head. Beyond the drop off point, the wheels and bogies of derailed wagons advancing along the sleepers, progressively damaged the track structure both within the four foot[10] and on the field side of the rail (left side direction of travel). This resulted in the loss of track structural integrity and the subsequent destruction of the track, with rolling stock ploughing into the ballast and resulting in the multi-wagon pile-up (Figure 2 and 3).

There was no evidence of spread in the section of track leading up to the PoD, so gauge widening was not considered to have been a factor in the derailment. Similarly, there were no signs of any broken/fractured rail immediately at or before the PoD.

Although the track structure leading into/out of the derailment site appeared to be in good condition, there were signs of lateral vehicle oscillations along the length of track leading up to PoD. This was characterised by flange contact wear along the head of the rails at regular intervals. There was also evidence of a vertical twist defect immediately after a culvert at 600.657 km.

The potential influence of the observed track conditions were supported by:

  • Statements from the train drivers, who both indicated that the track was rough (side-to-side oscillations) leading into the derailment site and that the train had kicked heavily at or near the PoD
  • Forward facing video evidence from train 4414[11] which had passed through the site earlier that morning (about 0940) and showed evidence of a sizeable track misalignment at or near the PoD
  • Rear facing video from train 4413 (mid-section trailing locomotive AC4304) showing evidence of a substantial sideways kick as wagons behind locomotive AC4304 passed over the PoD.

Derailment - summary

The available evidence, as detailed above, indicates that the derailment of ore train 4413 near Bonnie Vale in Western Australia was the result of flange climb.

There was evidence of lateral track vehicle oscillations along the length of track leading up to the PoD and a twist defect immediately after the culvert at 600.657 km. Although the locomotives and ore wagons appeared to be in good condition it is considered that the vehicle oscillations may have been of sufficient magnitude to cause the leading wheel of wagon WOE33548K to unload, mount the rail head at 600.729 km and derail.

Ongoing investigation activities

The ATSB investigation is continuing and will focus on:

  • The dynamic behaviour of WOE class wagons.
  • Train braking performance, in particular when configured with mid-power locomotives.
  • Track inspection and maintenance procedures, including defect reporting processes used by the infrastructure manager and the rolling stock operator.


[1]     The 24-hour clock is used in this report and is referenced from Western Standard Time (WST), UTC + 8.0 hours.
[2]     Distances are track kilometres measured from Perth terminus.
[3]     Two drivers operate alternately as a driver/observer pair.
[4]     The trains’ electric traction motors are used for regenerative/electric braking.
[5]     The end-of train monitor works in conjunction with an end-of-train marker, a device fitted to the trailing end of the last vehicle of a train. The system is used to indicate that the train is intact by monitoring brake pipe pressure.
[6]     A train parting event normally results in a loss of brake pipe integrity and an associated loss of brake pipe pressure.
[7]     The placing of additional locomotives at intermediate points within a train and remotely controlling these locomotives from the lead locomotive.
[8]     Continuous welded rail (CWR) – Track where the rail is joined by welding (and other non-moveable joints such as glued insulated joints) in lengths greater than 300 metres.
[9]     A fastening that provides a degree of elasticity between the sleeper and rail with the aim of avoiding the loosening of the fastening due to vibration, as well as enhancing the ability of the fastening system to resist longitudinal creep forces and buckling forces associated with continuously welded rail (CWR).
[10]    The area between the rails of a standard gauge railway.
[11]    Forward facing video evidence was not available from train 4413, train that derailed, due to a technical failure of the train’s forward facing video recorder.

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Safety issues

RO-2014-008-SI-01 - RO-2014-008-SI-02 - RO-2014-008-SI-03 - RO-2014-008-SI-04 -  

WOE class wagon, dynamic performance

When travelling at speeds near 90 km/h on track having particular track irregularities, the WOE class wagons appear to be susceptible to harmonic oscillations of sufficient magnitude to produce wheel unloading, flange climb and derailment.

Safety issue details
Issue number:RO-2014-008-SI-01
Who it affects:All rail transport operators throughout Australia
Status:Safety action pending


 

Increasing train speed

After re-railing the track, permitted train speed was increased without due consideration of the effects of cyclic track irregularities on the dynamic performance of the WOE class wagon.

Safety issue details
Issue number:RO-2014-008-SI-02
Who it affects:All rail transport operators throughout Australia
Status:Safety action pending


 

Driver reporting and cab ride arrangements

The frequency of driver reporting and locomotive cab rides by track inspectors had been insufficient for identifying rough track through the derailment site.

Safety issue details
Issue number:RO-2014-008-SI-03
Who it affects:All rail transport operators throughout Australia
Status:Safety action pending


 

Train braking performance

The loss of brake pipe integrity during the derailment event did not result in the train brakes automatically activating.

Safety issue details
Issue number:RO-2014-008-SI-04
Who it affects:All rail transport operators throughout Australia
Status:Safety action pending

 
General details
Date: 14 May 2014 Investigation status: Completed 
Time: 1048 WST Investigation type: Occurrence Investigation 
Location   (show map):Bonnie Vale   
State: Western Australia  
Release date: 27 March 2015 Occurrence category: Accident 
Report status: Final Highest injury level: None 
 
Train details
Line operator: Brookfield Rail 
Train operator: Aurizon 
Train registration: 4413 
Type of operation: Derailment - Running Line 
Sector: Freight 
Damage to train: Serious 
 
 
 
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Last update 23 December 2016