The Rail Accident Investigation Branch has released Urgent Safety Advice after a freight train derailed and set on fire near Llangennech in South Wales.
At 23:15 on the 26th August 2020, 6A11 21:52 Robeston to Theale with 25 tank wagons derailed on the Up line near Llangennech. The derailment and damage to the wagons caused a significant fuel spillage and a major fire, with the investigation finding that 10 wagons had derailed, and around 330,000 litres of fuel had been spilt.
The primary inspection by the RAIB found that the third wagon's wheels had become locked at some point, but were running properly when it left Robeston. At some point in the journey, the brakes on all wheels of this wagon had applied and remained applied until the train derailed. Although the brakes were dragging, the wheels continued to turn, however, the leading axle ceased to rotate at all (as seen by the photo above at Pen-y-Bedd level crossing).
The axle locked, and caused a wheel flat and also a false flange on the wheel so when it reached the nearby Morlais Junction, the right-hand wheel caught points and a converging stock rail. The locomotive and two front wagons went to the right over the points, but the third wagon went straight ahead and derailed, and the nine other wagons followed.
An inspection of the third wagon found that the relay valve was loose on the pipe bracket. A sealing ring from one of the ports found in the mating face had moved and had become lodged between the two other ports, which probably created a space for the air to pass through, producing the brakes coming on.
The Entities in Charge of Maintenance (or ECM) could not identify with any certainty where and when the fastenings had last been disturbed; however, this may have taken place during routine repairs in the sidings at Robeston or during maintenance elsewhere. There was no record of any checks on the fastings, and no process requiring these checks must be taken out.
The Urgent Safety Advice by the RAIB means that ECMs should review the system for the inspection of wagons that carry dangerous goods, like fuel, to make sure they have the arrangements in place to manage the safety risk. This should include an assessment of:
- facilities, tools and equipment at all maintenance locations
- systems for assuring the competence of those involved
- management systems and instructions for assuring the quality of work undertaken
- methods for initial and ongoing assurance of the security of fastenings
- processes for the identification and tracking of safety-critical components.
You can read all our coverage of the incident on the Llangennch page here.
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