Report 01/2022: Derailment and fire at Llangennech
Derailment and fire involving a tanker train at Llangennech, Carmarthenshire, 26 August 2020.
Summary
At about 23:04 hrs on 26 August 2020, train 6A11, the 21:52 hrs service from Robeston (Milford Haven) to Theale, conveying 25 laden tank wagons, derailed near Llangennech, in Carmarthenshire. The derailment and the consequent damage to the wagons resulted in a significant spillage of fuel and a major fire. The driver, who was unhurt, reported the accident to the signaller. Subsequent examination of the site found that ten wagons (positioned third to twelfth in the train) had derailed, and that around 446,000 litres of fuel had escaped.
The spilled fuel caused major damage to the environment in an area which is both a site of special scientific interest (SSSI) and a special area of conservation (SAC), including cockle beds, natural tidal mud flats and wetlands.
The derailment occurred because one set of wheels on the third wagon in the train stopped rotating during the journey. The wheelset had become locked, probably because of a defect in the braking system on the third wagon, arising from deficiencies in the design and maintenance of components. The sliding of the locked wheel along the railhead caused damage to the profile of the wheel treads. This meant that the wheels were unable to safely negotiate Morlais Junction, near Llangennech, damaging the pointwork and causing the third wagon to become derailed. The following wagons derailed on the damaged track. Some of the derailed tank wagons were ruptured in the accident, and the spilling fuel ignited.
Recommendations
RAIB has made nine recommendations. These cover a review of the actions taken by the owner of the wagons following this and previous accidents, and improvements to the maintenance processes at the locations where the wagons involved in the accident are maintained and overhauled. The probable failure mode of the braking system and the lessons learned from reconstruction tests have led to a recommendation to the manufacturer of some of the braking system components to undertake a review of their design. A recommendation has been made to the organisations who carry out surveillance and certification of entities in charge of maintenance of rail freight vehicles to review their processes. A further two recommendations have been made to improve the management of wagon maintenance on the railways in Great Britain, and to review the technology and systems used to alert traincrew, signallers and railway control offices to wagon defects that may lead to derailment. The final recommendation is for a review of the arrangements for regulatory oversight of entities in charge of maintenance and certification bodies that are not based in the UK.
Response to recommendations:
- RAIB will periodically update the status of recommendations as reported to us by the relevant safety authority or public body
- RAIB may add comment, particularly if we have concerns regarding these responses.