Report 01/2022: Derailment and fire involving tank train at Llangennech, Carmarthenshire


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At approximately 11:04 p.m. on August 26, 2020, train 6A11, the 9:52 p.m. service from Robeston (Milford Haven) to Theale, carrying 25 loaded tank cars, derailed near Llangennech, Carmarthenshire. The resulting derailment and damage to the cars resulted in a major fuel spill and a major fire. The driver, who was not injured, reported the accident to the flagman. A subsequent examination of the site revealed that ten carriages (positioned third to twelfth in the train) had derailed and approximately 446,000 liters of fuel had escaped.

The spilled fuel has caused significant environmental damage in an area which is both a Site of Special Scientific Interest (SSSI) and a Special Area of ​​Conservation (SAC), including hull banks, natural mudflats and wetlands.

The derailment occurred because a set of wheels on the train’s third car stopped rotating while in transit. The axle had locked up, likely due to a fault in the third car’s brake system, due to faulty component design and maintenance. The slipping of the locked wheel along the rail head damaged the tread profile. This meant the wheels were unable to safely negotiate Morlais Junction, near Llangennech, damaging the switch and derailing the third carriage. The following cars derailed on the damaged track. Some of the derailed tank cars broke off in the crash and the spilled fuel ignited.


The RAIB made nine recommendations. These relate to a review of the actions taken by the owner of the wagons following this accident and previous accidents, and the improvement of maintenance processes at the places where the wagons involved in the accident are maintained and revised. The probable mode of failure of the braking system and the lessons learned from the reconstruction tests led to recommending that the manufacturer of certain components of the braking system undertake a revision of their design. A recommendation has been made to the bodies providing oversight and certification of entities in charge of the maintenance of rail freight vehicles to review their processes. Two other recommendations were made to improve the management of wagon maintenance on Britain’s railways and to review the technology and systems used to alert on-board staff, flagmen and rail control offices to faults wagons that could cause a derailment. The final recommendation concerns a review of the regulatory oversight arrangements of entities in charge of maintenance and certification bodies that are not based in the UK.

Simon French, Chief Rail Accident Inspector said:

“Trains carrying dangerous goods play an important role in the UK economy, but the risks of operating them need to be properly controlled. The consequences when things go wrong can be disastrous, as we saw in Llangennech in August 2020. Luckily no one was injured, but people were evacuated from their homes and the damage, both to the environment that to people’s livelihoods, will take years to put right. The accident also shut down the railway line for over six months while the railway was rebuilt and engineers worked to minimize damage to the local environment.

“The railway industry’s approach to the safe maintenance of freight wagons needs to be improved. In this investigation, we found that maintenance practices were inadequate and the importance of proper attachment of the various components of the tank car braking system was not appreciated. This is not the first time that we have investigated an accident where the RAIB has identified serious maintenance problems with a freight train. Over the past decade, we have identified poor car maintenance as a factor in more than ten investigations, including ill-adjusted suspension, undetected frame twist and worn bogie pivot linings.

“In our report, we have recommended a review of the technology and systems currently in use in the UK and other European countries to identify how improvements can be made to the railway’s ability to detect a fault railcars that can lead to derailment, such as dragging brakes Smarter use of wayside technology to warn the railway that a train is endangering its infrastructure is a familiar theme at RAIB; our previous investigations have recommended greater use of wheel impact load sensing data to identify uneven wheel loads.The RAIB would like to see more work in this area focused on how trackside systems could be used to reliably detect dragging brakes, but also how this data can be used intelligently to benefit both real-time operations and fleet maintenance management.

“The majority of our recommendations following our in-depth investigation into the Llangennech derailment relate to the improvement of freight wagon maintenance processes. a comprehensive program of measures designed to promote improved maintenance of freight wagons in the UK This is a collaborative effort, which is appropriate given the potential benefits of greater sharing of information across the industry.

“I would like to underscore the importance of getting it right. It is time for freight railcar maintenance practices to come under scrutiny and for the industry to consider how best to fulfill its legal obligation. and morality to present cars suitable for running in the cities of the country.The price for obtaining this right is improved safety, better reliability and the respect of the legal obligations of the freight sector – and all at a reasonable cost.

“As the RAIB has been concerned about the quality of the maintenance of freight wagons for many years, I welcome the actions taken by the ORR to strengthen its supervision of the entities in charge of maintenance. This will provide greater visibility of the important work of maintainers and verify the extent to which the important role of ECMs is correctly understood and applied in the UK freight sector, and the adequacy of oversight undertaken by certification bodies (whether they are based in the UK or the EU).

“I have been struck by the extent to which the safety status of freight railcars is critically dependent on providing people with the tools and training they need to perform difficult work, very often in harsh conditions. dark, damp and cold workplaces. So I urge freight operators and maintainers to think carefully about who is doing the hands-on work and what things could be done to build the capacity of the workforce.

Notes to Editors

  1. The sole purpose of RAIB investigations is to prevent future accidents and incidents and to improve railway safety. The RAIB does not establish fault, liability and does not take legal action.
  2. The RAIB operates, as far as possible, in an open and transparent manner. Although our investigations are completely independent of the railway industry, we maintain close liaison with the railway companies and if we discover any issues that could affect railway safety, we ensure that the information to their topic is broadcast to the right people as soon as possible. , and certainly well before the publication of our final report.
  3. For media enquiries, please call 01932 440015.

News date: January 13, 2022

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