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Llangennech derailment – Initial findings of the RAIB investigation
Yesterday the Rail Accident Investigation Branch published initial findings on the causes of the derailment, below is an extract from their release:
RAIBs preliminary examination found that, although all the wheels on the train were probably rotating freely when the train left Milford Haven, at some point in the journey the brakes on all wheels of the third wagon on the train had become applied, and remained so until derailment. While three of the four axles of this wagon continued to turn, although their brakes were dragging, the lead axle ceased to rotate altogether and consequently a flat spot around 230mm long developed on each of the wheels on this axle. This was a substantial ‘false flange’ ( a raised lip on the outer side of the wheel tread) associated with these flat spots.
When the train reached the crossover at Morlais junction, travelling at 30mph, the false flange on the right hand wheel caught on the converging stock rail and distorted the track, leading to derailment of both wheels. Around one hundred metres further on, the partly derailed wagon encountered facing points set to route the train to the right. The locomotive and the two leading wagons went to the right and the derailed third wagon went straight ahead.
The third wagon turned over onto its right side and became detached from the wagon in front of it. This caused the points and the track beyond them to be destroyed, and derailment of another nine wagons followed.
The locomotive and first two wagons came to a stop about 180 metres away from the third wagon and then moved some four hundred metres from the derailment where a fire had now started.
There is further work for RAIB to do.
However these early conclusions MAY imply maintenance or a component failure and not driver error or track failure.