Ice on the line

December is an in-between month so far as weather goes. Hopefully the worst of the delays caused by ‘leaves on the line’ are over, and the ‘wrong sort of snow” normally hasn’t arrived yet. However, there is one problem that can disrupt services at this time of year – and that’s ice. Sanding equipment, which is fitted to most trains, can keep the wheels turning, but what happens when ice collects on an electrical conductor rail?

If icing is bad then the collector shoe stands off from the conductor and no electrical supply reaches the train. If there is a thinner or intermittent covering of ice then some power can get through. However, when the train starts to move and demand reaches a peak then the available current can be insufficient and the train stalls.

The University of Birmingham has been looking into the problem. A team of final-year students under Dr Clive Roberts built a test rig consisting of a static shoe on a rotating disc which simulates the moving conductor rail. Placing the complete mechanism in a cold room and adding water produced a workable similarity to the Home Counties in winter. Spinning the ‘conductor rail’ at up to 50mph allows the effectiveness of various anti-icing and de-icing products to be tested under varying conditions – everything from chemical sprays and brushes to heated rails.

And it is the latter technique which is now seeing service. Network Rail has worked with specialist suppler Eltherm UK Ltd to attach 16,000 metres of specialist heating strips to the third rail across Kent as part of a county-wide trial to improve reliability of train services during harsh winter weather conditions.

Novel solution

Eltherm is a well-established manufacturer of trace heating cables, flexible heated hoses and heated jackets based in Burbach in North Rhine-Westphalia, Germany. Over many years it has gained an extensive level of knowledge and expertise in the manufacture of trace heating cables and tapes (self-regulating and constant power types) and control systems for a wide range of industries from chemical and process through to construction. It also services both heavy rail and light rail applications, including de-icing systems for rubber-tyred metros. Eltherm UK Ltd has recently been set up to serve the British market.

Its solution to Network Rail’s problem is a flat heating cable called El-Rail. This contains six conductors, insulated by PTFE and embedded in a silicone jacket, which can be laid along the side of the conductor rail. Held in place by special stainless steel clips they use the same power supply as the rail itself, although connection is via a separate control panel.

El-Rail’s large flat surface supported by a rigid cover gives good thermal contact between the cable and the rail, so minimising losses, while the spring clips enable installation to be carried out swiftly without the need to block the line for extended periods. Most of the work is being carried out at night.

Real-world application

Three routes in Kent were selected for the first trial. Stations and points on the Hastings-Grove Park, Ashford-Maidstone and Tonbridge-Orpington lines were identified for the installation of heating strips. By the end of the year, heating elements will have been installed at 42 key locations across the Kent route, primarily at locations where trains come to a halt.

Dave Ward, Network Rail’s route director for Kent, explained the thinking behind the trials. “We are pioneering this new technology in Britain to further improve the reliability of train services during harsh winter weather conditions. We have analysed weather patterns over the last ten years to identify the most vulnerable areas and it is here that we are concentrating the trial of the heating strips. “Last winter was the most severe for 30 years. Although the railway coped relatively well compared to other forms of transport, we have used the experience to try and make the railway more robust so we can deliver a better and more reliable service for passengers.”

Technical ins and outs

The sections of El-Rail cable are initially controlled individually. It takes a considerable time to heat up a long section of rail to around +10C and, because of this thermal inertia, an automatic temperature-sensitive switch is not the answer. So use is made of weather forecasts and other local information in the same way that councils send out road gritters before an expected cold night. However Network Rail is looking at ways of switching them remotely from a central point using Wi-Fi.

Similar projects are planned for other parts of the railway in the south-east which use the third rail power system, particularly East and West Sussex, Surrey and Hampshire.

Rail heating is not a complete solution. The new initiatives will complement Network Rail’s established winter contingency plans during harsh weather conditions. Maintenance teams will still check hundreds of points at key junctions to prevent equipment from freezing and a fleet of specialist anti-icing trains will also operate across the affected areas, spraying heated anti-freeze onto the rails. However, at 42 locations in Kent, even a cold frosty night shouldn’t stop the trains due to ‘ice on the conductor’.