Coating the underside of the bridge

In what is being described as a world first, electric resistant paint combined with voltage-controlled clearance (VCC) has helped make a Victorian railway bridge safe to use by new electric trains.

Electrification of the railway between London and Cardiff was completed last year. To get the necessary overhead wires and cables installed usually means many structures have to be reconstructed. However, a new coating technology that has been developed with the University of Southampton may have changed all that.

Richard Stainton, Network Rail engineering expert (yes, that really is his official job title), said: “Intersection Bridge – situated in the centre of Cardiff, on the Wales route – is a prime example. The structure is too low to safely fit all the kit required. Ordinarily, this would force Network Rail to demolish it and rebuild it at a greater height to keep electric trains a safe distance away from the bridge as they pass under, and stop them from electrifying the bridge itself, or anything on it.”

In this case, however, Network Rail coated the underside of the bridge with electric-resistant paint. It was used alongside specially developed lineside kit, including: surge arresters and insulated bridge arms, to insulate the bridge from electricity and make it safe for electric trains to pass under.

The paint was combined with voltage-controlled clearance (VCC) which allowed the electrical clearance gap to be reduced by 20mm from the overhead line equipment (OLE) to the bridge, and 70mm from the OLE to the trains roofs.

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This meant around £40m of savings as the bridge did not need to be knocked down to start from scratch.

Peter Smith-Jaynes, regional asset manager, electrification, Wales & Western, said: “It’s a really complex situation at Cardiff Intersection Bridge. It’s a very busy rail-over-rail bridge, with a canal underneath that, and it’s surrounded by high-rise buildings. Just accessing the bridge would have been difficult but knocking it down and rebuilding it would have been nearly impossible. We had to find another solution.”

Richard Stainton added: “Typically, a third of electrification project expenditure is on reconstruction and modifying of civils structures – tunnels, bridges and stations – to allow the installation OLE with the necessary clearances.

“This solution will create enormous efficiencies; allowing future electrification projects to be installed and energised without multi-million-pound expenditure – potentially saving the tax-payers as much as £100m.

“It will also significantly reduce the number of rail closures – for access – lowering the disruption to passengers, road networks, and railway neighbours.”

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