Rail Industry Focus

Melting point

Sitting back and hoping for warm winters is not an option: something has to be done to make the railways more resilient to ice and snow. RTM speaks to Network Rail’s Mark Ellerby about the steps it has been taking in south east England.

The electrified third rail network south of the Thames has been particularly badly affected by extreme winter weather in recent years, as ice and snow on the conductor rail can interfere so badly with traction.

A trial of conductor rail heating strip technology was done last winter, on 29km of track across Kent and Sussex, using a constant wattage strip supplied by German company Eltherm and switches from Hove’s LC Switchgear. Network Rail is now confident this type of technology is the best way forward and this winter has extended conductor rail heating across 106km of track across the south east.

Commercial scheme sponsor Mark Ellerby of Network Rail spoke to RTM about the work, which is part of a wider package of resilience measures.

He said: “It’s been a two-year programme, spread over two phases. Phase 1 was spread across Kent and Sussex, and was effectively a widescale trial of third rail heating, to see that it would actually work. That was last winter, when in total, we installed 29km, across Kent and Sussex. That’s all installed and up-and-running.

“The switch operation is literally manual, people go out and switch on each of the installations. We’ve now proven the technology can work; it’s been quite successful, and we’ve been able to iron out some of the creases as well.”

Roll-out

This year, the technology has been installed on a much larger portion of the network, and using more sophisticated systems.

Across the South East, the winter has seen the installation of third rail heating across 46km of track in Kent, 27km in Sussex, and 4km on the Wessex route, meaning that on top of last winter’s 29km, there is now a total of 106km of heated rail.

The locations chosen have been those that tend to be affected the worst by icy weather, both because of their importance in the local network, and because of the geographic conditions that can make achieving traction more difficult. Kent has got the bulk of the conductor rail heating purely because of weather patterns and the history of train failures caused by ice in the county, whose geography makes it particularly susceptible.

Getting to 30mph

Ellerby explained: “The principle is to allow a train to accelerate under its own traction up to 30mph. It’s to give it that chance to get away from the station, or a signal location where we might stop a train in normal service, or indeed in perturbated service, and key junctions, sidings and stations.

“It’s enough heating strip below an eightcar train and in front of it to allow it to get up to 30mph, as at that speed its shoe is naturally able to act as its own ice scraper and take traction.

“We’re now looking at additional sites, to see if we can bolt anything else onto the programme – which is an extra challenge. But the biggest challenge, quite frankly, was getting to the point where we had technology we could use.

“The most interesting part of the technology we have installed this year is the remote switching technology. In phase 1, it was literally on-off, nothing fancy. For phase 2, we’ve introduced some different switching technology. 

“It works firstly on ambient temperature, so the panel itself senses the outside temperature. When it drops, it switches on the heating; it works like a thermostat at home, which is quite neat.

“But, the next part to it, which we’re testing and we’re going to bring in this year, is a remote switch. It means that from our control centres, using weather alerts, we can hit the over-ride and switch the heating on, making absolutely certain there’s no ice on the rail at those locations. We can know via those alerts, ahead of the ambient control sensor, that there’s going to be heavy snow tonight in the Dover area, for example. We’ll switch it on, a couple of hours before service starts, and then we know we’ve got that system in operation rather than just the local control. The system itself has no in-built forecasting technology, so it can’t possibly ‘guess’ what weather is coming.”

Self-regulating heating strips

As well as the temperature sensor and remote switching technology, Network Rail has also experimented with a ‘self-regulating’ strip, produced by Heat Trace, based in Cheshire.

Of the 46km of heated strip in Kent, 16.5km has been of this type.

Ellerby said: “Heat Trace has primarily been a points heating supplier for us, so this is a new application. We think it will use less electricity, because it’s selfregulating. It’s not constant wattage, so not always on. It works by using two wires opposite each other, with a semi-conductor between them. As it gets hotter and colder the semi-conductor allows less or more electricity through. It is therefore its own control measure, which is a great piece of technology, so it keeps itself at a constant temperature.

“It shouldn’t be on unnecessarily, is the thinking: it won’t be constantly running, heating up the railway. But we need to test that technology, and it does have some other characteristics we’re wrestling with as well.”

Ready for the future

As RTM went to press, the winter of 2011/2012 had not seen extreme snow and ice on the scale of 2010 or 2009, with gales and storms having the bigger impact on the railways. But obviously, the technology needs to be in place in advance so the network is ready for whatever comes.

Ellerby said: “Since October, we haven’t had anything extreme. We’ve had some frost, but nothing that we would expect to have desperately strained the network. Last year was the big test, between Tunbridge and Hastings. Based on the success of that trial – it was successful in terms of clearing the rail – we knew it was worth rolling out further.

“Ultimately, this is about getting trains from point A to the end point at point B. It’s about getting trains moving through the system. It’s not a scattergun approach, it’s about lines of route, so that’s why we’ve tended to focus on Tunbridge to Hastings, so a train can get from its starting point at Hastings all the way up to, for example, Grove Park, and that means trains keep moving and the system flows.

“The roll-out this year has been a further extension to that, on this line of route basis.

“Last year the problem was that we didn’t necessarily have the capability to unblock the whole of the system, and that’s what this year’s work has been about.

“There are a range of measures that have been implemented; not just conductor rail heating in isolation. This on its own will not keep the system moving. We’ve also brought in snow and ice treatment trains, MPV modifications, and other measures. They form part of a package that keeps the system moving.

“You’d have to heat the rail between Dover and Charing Cross pretty well the whole way if you didn’t have all the measures we’re introducing as well.” 

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