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Derailment at Ordsall Lane Junction, Salford, 23 January 2013

The RAIB is investigating a derailment that occurred on the line between Deansgate Station, in Manchester city centre, and Ordsall Lane Junction, Salford, on Wednesday 23 January 2013.

At 14:34 hrs, a locomotive that was being hauled at the rear of train 5Z47 derailed on the curve approaching Ordsall Lane Junction. The train was made up of a class 47 locomotive pulling five empty coaches and the derailed vehicle, another class 47 which was being dead hauled. The train was en-route from Ardwick train maintenance depot in Manchester, to Carnforth, Lancashire. It was travelling at 18 mph (29 km/h) at the time of the derailment.

The class 47 locomotive, 47500, ran derailed for around 70 metres and caught on fire. No one was injured, but the line was closed for repairs and recovery for two days.

(http://www.raib.gov.uk/cms_resources/Ordsall%20Lane%20Jn.jpg)
The derailed locomotive

The RAIB^s investigation will examine the sequence of events leading up to the accident and the cause of the derailment. This will include consideration of the design, maintenance and condition of both the track and the derailed locomotive.

The RAIB^s investigation is independent of any investigation by the safety authority (the Office of Railway Regulation).

The RAIB will publish its findings, including any recommendations to improve safety, at the conclusion of its investigation. This report will be available on the RAIB website.

Summary

At 14:34 hrs on 23 January 2013 a class 47 diesel electric locomotive derailed on a small radius curve, approaching Ordsall Lane Junction in Salford, and caught fire. The locomotive derailed to the outside of the curve. It was being hauled on the rear of an empty train, which was formed of another class 47 locomotive and five coaches.

The cause of the derailment was that 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. Despite being required by standards, there was no check rail on the curve. This safeguard would have restricted the lateral displacement of the wheels and prevented the derailment.

The RAIB found that the following factors had resulted in the lateral forces being high enough to initiate wheel climbing conditions:
- 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 be established; recently-modified arrangements for lubricating the rails did not prevent this.
- Machining work that had recently been undertaken to restore the wheel profiles on the locomotive; this removed any pre-existing lubricant and contaminant from the locomotive wheels that would otherwise have helped reduce wheel-rail contact friction levels.
- The relatively low angle of contact between the wheel and rail associated with the newly-restored wheels on the locomotive; this reduced the locomotive^s ability to resist the climbing forces acting at the wheel-rail interface.
- The wider than normal distance between the rails (track gauge) that had developed on the curve.

The above combined to generate the conditions necessary for derailment, but none of these factors involved non-compliance with applicable standards.

Although it was found that the reprofiling of the wheels had left the wheel surface slightly rougher than specified, the RAIB decided not to investigate this factor any further. This was because the surface was only marginally non-compliant and there is contradictory evidence regarding its effect on wheel-rail friction.

The basic approach to managing the risk of derailment on small radius curves on the national network relies on vehicles and track complying with separate technical standards. However, because these standards do not require consideration of the worst possible combination of conditions, there remains a residual risk of derailment. It is generally recognised by the railway industry that the level of this residual risk is reduced by certain traditional features, such as check rails and trackside rail lubricators. Therefore, although not generally relied upon, RAIB observed that any change in the provision of such features has the potential to reduce the overall level of derailment safety.

The RAIB has directed three recommendations to Network Rail. They are concerned with:
- ensuring that non-compliances with currently prescribed requirements for check rails are identified and mitigated;
- 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
- determining when it is necessary to bring existing track assets in line with latest design standards.