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TRACK TECHNOLOGY


The process


Ahead of the TRS itself comes a Quattro RRV, digging holes for ballast from under a short section of track around four sleepers long to be moved into. This short section, with sleepers hanging in the air, is where the TRS starts its real work, after the clips have been knocked out.


With the new rail lying next to the track, the old rail is cut, and the new rail picked up by the machinery and ‘threaded’ over the old rail into place, as rotating ‘forks’ scoop the old sleepers out of the ground and away, replacing them with new ones delivered via high-speed gantry cranes from the wagons. At the joint the new rail is joined to the existing track – laid the previous night – using temporary clamps at first, and welded properly later.


While TRS2 depends on a road-rail vehicle behind it to move the old rail and drop it into the cess, TRS4 – which has only been in use for two years – has its own rail manipulator rollers/arms underneath, which automatically feed the old rail into the cess.


“We’re looking at those modifications to TRS2 to see if it’s worthwhile,” Brooks said.


Other teams and machines finish the process – welders, a tamper and a regulator. Network Rail has a fleet of eight tampers and five regulators, which work with the five pieces of high output plant.


The final job is re-connecting signalling and


other trackside equipment. 80mph handback


A big advantage of the high output plant and the tamping method is that the track delivery team can hand back the line at 80mph, instead of 30/50.


Brooks explained: “None of our conventional contractors are certified to use the 80mph clamping mechanism that Amey Colas uses: that’s a function of the fact that these guys are full-time professionals and we have a lot of confidence in their ability.”


A second pass of the Plasser and Theurer tamper the following night, with its Dynamic Track Stabilisation technology, brings the line speed back up to its maximum – 110mph in this case.


Resilience and recovery Planning ahead


As with any engineering operation depending on multiple pieces of heavy machinery working simultaneously in busy environments, often at night, problems do arise. But the high output plant is a reliable renewal method, Brooks said, especially since recovery after a fault is so much easier.


He explained: “Our ability to recover if we have a problem on this site is far better than having a 500-yard hole when we are renewing conventionally, if for example the crane that was due to install all the sleepers had failed. You’d then have a massive problem. This is a


While the high output team is part of Infrastructure Projects under Simon Kirby, Brooks and his three counterparts on other routes also have a ‘dotted line’ report directly into the route managing directors, highlighting how devolution is working in practice.


As Brooks put it: “I’m as much a part of the LNE and East Midlands route teams, under Phil Verster and Martin Frobisher, as I am part of Steve Featherstone’s track team.”


Cont Overleaf > rail technology magazine Dec/Jan 13 | 29


much more reliable renewal method.


“The risk on this piece of kit, in terms of failure and the impact on passengers, is minimal, because if this kit broke down now, we’d just stop work, take it out of the ground, move it out of the way, and then we’d only have a five-yard piece of railway without sleepers in it.”


Much of the work during overnight possession windows is in preparing and exiting the site – the machine itself is only running for a few hours, around two and a half the night RTM visited.


It has a ‘planned operating speed’ of 350 metres per hour, and a peak speed of 550 metres per hour, but that’s limited by the speed of the P2RL turntable gantry and the Fastclipper device, Network Rail says. Each sleeper wagon, carrying five pallets of 24 sleepers each, has enough to lay 78 metres of track.


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