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What happened

At about 0800 on 26 July 2014, Genesee & Wyoming Australia (GWA) freight train 6DA2 derailed at the 1036.541 km mark near Marryat, South Australia.

The train was travelling at about 80 km/h when it derailed. The trailing locomotive, crew van and 17 wagons derailed, with the train separating into two portions that came to a stand about 108 m apart. The wagons (consisting of 35 platforms) and 340 m of track were significantly damaged.

There were no injuries sustained by the driving train crew or drivers resting in the derailed crew van.

What the ATSB found

The ATSB found the train had derailed on a section of 80 lb/yd rail, while travelling over a flash-butt welded joint that had fractured through a pre-existing defect in the rail foot. The defect most likely occurred during the flash-butt welding process, which subsequently led to crack propagation and brittle fracture that extended vertically through the rail web.

Metallurgical evidence indicated that the fracture had propagated slowly from the initiating defect and had likely been in existence for some time, remaining undetected during track inspections and the passage of trains for a period up to 30 years.

Due to the 80 lb/yd rail’s age, smaller section size and surface condition, all trains travelling those sections of track were speed restricted to 80km/h. While the rail through the area of the derailment had been subject to periodic visual and non-destructive inspections across its lifetime, it was evident that the inspection regime had not been effective in detecting and/or assessing some internal rail defects. Several of those defects had the potential to pose an immediate threat to the safety of rail services.

What's been done as a result

Following the derailment, the track manager (GWA) immediately slowed train speed over 80 lb/yd rail to 40 km/h for passenger trains and 50 km/h for freight trains. GWA then carried out a detailed continuous ultrasonic ‘cleansing test’ of the 80 lb/yd rail between Northgate and Alice Springs. To increase the sensitivity of the inspection, the ultrasonic intensity was increased by 6 dB and the test vehicle operating speed was slowed to between 10-12 km/h.

This inspection detected another broken rail at a flash-butt weld at the 975.244 km mark. This fracture had also initiated from the rail foot and required immediate plating and repair. Another 31 rail defects were found requiring various levels of response.

GWA advised that the continuous ultrasonic inspection frequency of 80 lb/yd rail has been increased to a minimum of four inspections per year and a programme to replace all 80 lb/yd rail is being evaluated.

Safety message

Railway owners and managers should ensure that their inspection and maintenance processes, for sections of rail that have a high incidence of defects, are an appropriate and effective management strategy for mitigating the risk of failure under the passage of a train.

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The occurrence

Context

Safety analysis

Findings

Safety issues and actions

Sources and submissions

 
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Prelimianry report released 23 September 2015

The occurrence

At about 0800[1] on 26 July 2014, the crew of Genesee & Wyoming Australia (GWA) freight train 6DA2 carried out a crew change near Hugh River, Northern Territory. The train then continued its journey south before crossing the South Australia – Northern Territory border. At about the 1056 km mark[2] the train entered a section of track that had a permanent speed restriction of 80 km/h.

Figure 1: Map of derailment location

RO2014014_Fig1

Source: FreightLink (annotated by ATSB)

The crew reported that train had been handling well when the driver reduced the speed with throttle and dynamic brake applications to enter the 80 km/h section (Figure 1). At about the 1036.530 km mark, the driver had just acknowledged the vigilance indication and was verifying the train’s speed when a ‘large bang’ was heard and the crew felt the lead locomotive jar. The crew commented that the ‘bang’ may have been their passage across a broken rail. The crew looked in the rear view mirrors and could see large volumes of dust rising from derailed wagons about 200 m behind the driver’s cab. At this time, the locomotives started shuddering and the driver made an emergency brake application and moved the throttle back to idle. The lead locomotive stopped about 360 m from the point of derailment.

Events after the derailment

The second driver alighted from the locomotive to check that the crew resting in the crew van were uninjured. When walking back to the crew van, the second driver observed that the wheelsets of the leading bogie on the trailing locomotive and the wheelsets of the trailing bogie on the crew van had also derailed.

Further inspection of the train found that it had separated into two portions, with the locomotives, locomotive refuelling wagon, crew van and one loaded container flat wagon remaining coupled. There was a gap of about 108 m between the front portion of train and the first of the derailed wagons. Various wagon types, freight and containers were scattered either laterally or vertically, for about 250 m along the rail corridor. The rear 930 m of the train, extending north beyond the point of derailment, remained on rail.

The train crew was uninjured during the event, however a number of rail vehicles, containers, freight goods and track infrastructure had sustained significant damage.

Context

The location

The derailment occurred near Marryat (1036.530 km) on the Tarcoola to Darwin railway, about 28 km south of the Northern Territory - South Australia border (Figure 1).

Train and train crew information

Train 6DA2 was a freight service operated by GWA between Darwin and Adelaide. The train consisted of two locomotives (GWU 006 leading and ALF 23 trailing), hauling an in-line fuel wagon, a crew van and 42 freight wagons (including 14 multi-platform wagons). The train was 1543.3 m long and had a trailing mass of 2540.9 t.

Train 6DA2 departed from the Berrimah Freight Terminal, Northern Territory at about 0920 on 25 July with a crew of four drivers. The drivers worked the train in pairs, operating in rotating relay shifts. The drivers operating the train at the time of derailment had about 2.5 and 7 years rail industry experience respectively.

Preliminary examination of the train and locomotive data indicated that there were no anomalies with the train handling or mechanical condition before the derailment. A review of video and audio recordings extracted from leading locomotive GWU 006 supported the drivers report of a ‘large bang’ when they travelled over what they thought was a broken rail (Figure 2).

Figure 2: Location of rail defect & minor ballast displacement near 1036.530 km mark

 RO2014014_Fig2

Source: Genesee & Wyoming – Locomotive GWU 006 video camera

Environmental conditions

The Bureau of Meteorology weather stations nearest the derailment were located at Kulgera (47 km NNW) and Ernabella (120 km E). On the morning of 26 July, overnight minimum temperatures at these stations were 10.4 °C and 9.4 °C respectively. No rainfall was recorded and winds were light, generally from a northerly direction. On this basis, it was considered unlikely that environmental conditions had contributed to the derailment.

Track information

The track infrastructure is owned and maintained by GWA, with the movement of rail traffic controlled from the GWA’s Transport Control Centre located at Dry Creek in South Australia.

The standard gauge (1435 mm) track at the derailment location consisted of 80 lb/yd rail fastened to concrete sleepers by resilient clips. The track formation comprised sand/clay based soil, topped with a capping layer and overlaid with ballast to a nominal design depth of 250 mm. The track bed supported prestressed concrete sleepers spaced at 667 mm centres.

Approaching the derailment site from Kulgera, the track was tangent[3] and the terrain slightly undulating. The derailment occurred within a 68 km section of track where the maximum track speed was 80 km/h.

Rail examination

The ATSB’s examination of the track leading into the derailment site determined the most likely contributor to the derailment was a break in the east rail near the 1036.530 km mark. An inspection of the mating ends from two broken rail sections strewn near the point of derailment identified variable oxidisation levels across the fracture surfaces and a localised feature that was characteristic of an internal material defect (Figure 3).

Figure 3: Broken rail fracture surface

 RO2014014_Fig3

Source: ATSB

The oxidisation that extended across the rail foot and through the web was noticeably greater than on the fracture surfaces through the rail head. This was consistent with the rail break originating in the rail foot and propagating vertically through the rail web.

Evidence of iron oxide bleed on the top surface of the foot suggested that the fracture had propagated slowly and been in existence for some period – potentially remaining undetected during track inspections and the passage of previous trains.

The rail head at the point of initial fracture showed light battering from train wheels that had traversed the break, before the rail breakup extended into multiple other sections - each about 700 mm long.

The ATSB quarantined four pieces of the broken rail for the purposes of laboratory metallurgical examination and analysis, including:

  • Magnetic particle testing to identify and characterise any surface features of relevance to the failure
  • Ultrasonic testing to assess internal quality (steel cleanliness) to the relevant standards
  • Residual stress measurements on the failed rail section/s (including a like-sample section of rail taken from store stock)
  • Examination and characterisation of the fracture surfaces
  • Chemical analysis and mechanical testing to assess material properties.

Ongoing investigation activities

The ATSB’s investigation is continuing and will focus on:

  • The inspection and maintenance practices for rail and track infrastructure between North Gate, South Australia and Alice Springs, Northern Territory
  • The findings from laboratory tests of the quarantined and sample rail sections
  • A review of rail and track defects reported by train operators and track inspection staff before the derailment of 6DA2.


[1]     The 24-hour clock is used in this report and is referenced from Central Standard Time (CST), UTC + 9.5 hours.

[2]     Distance in kilometres from the reference point located at Coonamia, South Australia.

[3]     Straight track with no applied cant.

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Safety issues

RO-2014-014-SI-01 - RO-2014-014-SI-02 -  

Detection of rail defects

The scheduled ultrasonic tests conducted in November 2013 on the 80 lb/yd rail between Northgate and Alice Springs had been ineffective in detecting and quantifying the significant defects present at 1036.541 km and 975.244 km locations.

Safety issue details
Issue number:RO-2014-014-SI-01
Who it affects:All rail track managers
Status:Adequately addressed


 

Special locations

Contrary to the requirements of procedure IN-PRC-020, GWA had not established a list of specific locations known to have an increased likelihood of failure, such that particular attention may be applied in those locations during inspections.

Safety issue details
Issue number:RO-2014-014-SI-02
Who it affects:All rail track managers
Status:Safety action pending

 
General details
Date: 26 July 2014 Investigation status: Completed 
Time: 0936 CST Investigation type: Occurrence Investigation 
Location   (show map):near Marryat  
State: South Australia  
Release date: 28 October 2015 Occurrence category: Accident 
Report status: Final Highest injury level: None 
 
Train details
Line operator: Genesee & Wyoming Australia 
Train operator: Genesee & Wyoming Australia 
Train registration: 6DA2 
Type of operation: Mixed Freight 
Sector: Freight 
Damage to train: Serious 
Departure point:Darwin, NT
Destination:Adelaide, SA
 
 
 
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Last update 19 November 2015