01.02.19
RAIB issues warning over brakes and wheel safety following derailment incident
The RAIB has published a warning about the maintenance of freight vehicles and the safety of wheel and braking systems on trains which can lead to derailment.
In a safety digest published following an investigation into the derailment of a rail head treatment train (RHTT) on 29 October 2018, the RAIB has issued a number of recommendations regarding freight transport safety.
The incident saw a Class 67 locomotive and two specialised wagons travelling between Inverness and Perth derail just after passing Dunkeld and Birnam.
The report said that both wheelsets of the fourth carriage derailed at a set of trailing points and ran for 100m, causing “significant track damage” before rerailing at the next set of trailing points.
The RAIB said the cause of the accident was a technical issue with the wheels when at some point in the journey the wheelset began to slide rather than rotate, which created a ‘large wheel flat’ on both wheels.
This caused the left-hand wheel to become trapped between the stock and the switch rail, pushing the two sets of wheels apart and directly leading to the derailment.
The RHTT train, which is deployed in autumn to combat leaf fall on the line, caused extensive track damage, including broken rails which resulted in a signalling fault.
The investigation warned that the accident demonstrates the danger of the formation of these large wheel flats leading to derailment, and the RAIB has issued a number of recommendations as a result.
Operators of RHHTs must now closely monitor the condition of wheels and braking systems when in low adhesion conditions, and maintainers of freight wagons have a process in place to control these incidents where handbrake interlocks.
Operators of freight trains must now undertake suitable roll-by examinations on departure from yards to detect non-rotating wheels. Staff are also recommended to prepare trains for departure by ensuring the handbrakes are fully released.