Published: 8th April 2014
The Rail Accident Investigation Branch has issued its report into a serious derailment in Manchester that happened on 23 January 2013. Class 47 diesel locomotive No. 47500 which was at the tail end of a five coach train became derailed and a severed fuel pipe leaked diesel which ignited and caused a major incident, in front of a major TV news studio.
The diesel was derailed on a tight curve approaching Ordsall Lane Junction in Salford, Manchester, while running from Ardwick depot a few miles away, to Carnforth where the train is based. The engine and carriages had been sent to the depot for wheel reprofiling. This is something all railway wheels undergo as routine maintenance and ensures that the wheels remain compatible with the rails which are maintained to a certain profile.
The train continued for around 70 metres before coming to a stand causing significant track damage and to the locomotive which caught fire. There were no injuries but it could have been worse if a train had been passing on the adjacent line. Both tracks run along tight curves on a viaduct or embankment in this area.
The curve where the derailment occurred has a radius of 178 metres and just after the derailment, the curve eases on a transitional section of track which is to be rebuilt as part of a huge Network Rail (NR) investment scheme.
Siemens owns and operates Ardwick depot which for three years, has provided a reprofiling service to West Coast Railways who own No. 47500.
The train was hauled from Ardwick by diesel No. 47854 and the train had a crew of four staff to operate it. After the wheel work, the crew checked the work and carried out what is called a rotational test to make sure all wheels turned correctly on the rails which they did.
RAIB report that the cause was the lack of a checkrail which meant ‘the lateral forces acting at the wheel-rail interface, as the locomotive negotiated the curve, were sufficient to cause the leading right-hand wheel to climb the rail’
Track is inspected at regular intervals and is subject to well documented standards and despite being mandated by these standards, there was no checkrail on the curve. The purpose of this is to restricted the lateral displacement of wheels preventing a derailment.
Most curves have a lubricant applied by a flange lubricator which as the name suggests, splashes a small amount of grease on a wheel flange to aid travel around the curve. RAIB reports that the dry and clean state of the inside face of the outer rail on the curve that enabled high levels of wheel-rail contact friction to occur and recently-modified arrangements for lubricating the rails did not prevent this action.
The wheel reprofiling removed all lubricant and contaminant from the locomotive wheels which RAIB say may have helped negotiate the tight curve reducing contact friction levels. The track gauge had also widened slightly from the normal distance between the rails on the curve and these factors combined to create the conditions necessary for derailment, but significantly, none of these factors involved non-compliance with applicable standards.
The rail industry accepts that derailment risk on curves is minimised by what are called traditional features, such as check rails and trackside rail lubricators.
RAIB has made three recommendations to Network Rail.
1. To ensure that non-compliances with currently prescribed requirements for check rails are identified and mitigated;
2. understanding any changes to infrastructure management processes that have increased derailment risk on small radius curves, and the need to take actions to reduce this risk; and
3. determining when it is necessary to bring existing track assets in line with latest design standards.
The West Coast Main Line between Crewe and Carlisle has had its gauge tightened by a few millimetres which provides a smoother ride for Pendolinos and other fast services but this had led to considerably increased wheel and flangewear on other trains, specifically charter services and steam locomotives.
Rails are also ground to prevent cracking and are also made of harder steel to increase their life which also increases tyre wear.
The owners of LMS ‘Duchess’ No. 46233 Duchess of Sutherland has used a Eurostar solution to solve the problem, they have fitted graphite sticks to their wheels to lubricate tyres and this which has cured the problem.