Understanding the third rail

Source: Rail Technology Magazine Aug/Sept 2012

Simon Green, chief engineer for Southern’s TRIME project, explains how a new maintenance prototype has the potential to significantly reduce damage to the third rail.

Damage to the third rail can lead to significant passenger disruption, and yet it remains difficult for rail operators to determine how problems with the interface between track and bogie arise.

A new project known as TRIME (Third Rail In-service Maintenance Equipment) seeks to improve this understanding and offer data and information on the interface behaviour.

Southern’s chief engineer Simon Green talked to RTM about the project, and how it could change the way maintenance is conducted.

Wrong place, wrong time

TRIME was developed in response to issues where trains lose shoes, resulting in damage to the equipment and potentially shorting out the power to the third rail. Southern set out to identify where excessive force is present on the network, to allow more targeted maintenance to be carried out by Network Rail.

Damage at the interface can lead to rail shoes being broken off, with the arm tearing and can even lead to the DC third rail supply being cut off.

“If it happens in the wrong place, at the wrong time, you’re talking thousands of minutes [of delays] which equates to huge amounts of passenger disruption,” Green said.

TRIME is expected to potentially save “several thousand minutes” a year, which saves money from penalty payments as well as improving delay management considerably.

Parameters for success

Previous research carried out by the University of Birmingham helped to provide measurements that Southern could use as an indicator of the condition of the third rail, based on contact between the conductor, the shoe and the rail.

Green explained: “They found the height that a shoe gets thrown in the air actually correlates pretty well with the force it experiences when it hits the ramp end of the conductor rail or in fact any feature on the conductor rail. Although we can measure lots of different parameters, that one gives us a really good indication of the interaction between the shoe and the conductor rail.”

The operating company then worked with Network Rail to transform this research into a functional system on board the train. Funding was achieved through an RSSB grant scheme and prototype equipment was installed on the train.

He said: “In essence, we installed an extra set of shoe gear on a bogie in the middle of the train, and pointing at the shoe arms is a laser measuring the position of the shoe arm.”

Because this system is relatively non-contact, it can remain in service for much longer than other damage measuring equipment, such as strain gauges.

Green commented: “It’s robust enough to be left in service without any risk of it breaking.”

These measurements are recorded by ontrain equipment saved onto a hard disk. Green said that a more sophisticated real-time data transfer would hopefully follow.

“The next thing we [need to] do is get that off automatically rather than in disk arrays.”

Targeted maintenance

The idea behind the scheme is to target maintenance much more efficiently. Once the data has been analysed, Network Rail can be alerted to locations that need some form of repair.

Green said: “It’s really successful; the worst locations are picked up on the network, and Network Rail can go and target that location, look for the defect and repair it. From their perspective it allows them to target locations where we can clearly demonstrate there’s a problem with the interface.”

The scheme could change the way Network Rail does its maintenance, and should, Grant told us, “give a pretty good indication of the condition and state of the conductor rail – to the point where you can think about targeting your maintenance interventions much more smartly, rather than sending people to go and look at a perfectly good conductor rail”.

The new Alliance between Network Rail (Sussex) and Southern, launched in June, has helped to facilitate the development of the project through joint funding, and collaborative working. Although the alliance with Southern doesn’t go as far as Network Rail’s ‘deep alliance’ deal with South West Trains – whose managing director Tim Shoveller has, since April, been responsible for both track and train on the route as the head of a joint Network Rail/ SWT management team – it still involves significant amount of collaboration and shared decision-making.

Green said: “The Alliance has clearly driven the work forward and will continue to do so because there is a mutual shared interest.

“By doing this together, we get the net benefit and we can demonstrate that both parties are working together for the benefit of our customers.”

From prototype to production

As the project is still in its early stages, prototyping has led to certain issues around implementation – but its potential has already been enough to see it shortlisted in the Engineering Innovation of the Year category in the National Rail Awards. Green described minor amendments and changes to install the equipment effectively.

He said: “We had a reasonable idea of what it would look like. Having said that, getting it integrated and onto a train is not necessarily that straightforward.”

Future development of the product would turn the prototype into a version that can be produced on a slightly larger scale, he added.

“We’d like a few trains running around with this sort of kit, but not necessarily in the form it currently is: it’s the nature of prototype.

“We’ve now demonstrated that it works, we need to take it forward with more trains measuring more of the time to get more data.”

Maintenance of the system was also an issue to consider, as there is no precedent demonstrating how long TRIME can continue to perform.

“These things have never actually run for any significant time,” Green said, and suggested that some further design modifications may be necessary in the future.

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