All aboard: The concrete batching section of the Hops train
Britain is playing catch-up on rail electrification. The country placed its faith in diesel trains while overhead electricity cables spread across other European rail networks.
The Scottish Executive published a programme of electrification in 2006, the year after Hurricane Katrina caused a sharp increase in oil prices, but in 2007 a Department for Transport white paper declared that the case for electrification was “not made yet”. The breakthrough came in 2009 when the then transport secretary Lord Adonis announced electrification of the core section of the Great Western main line (westwards from London Paddington) and several lines west of Manchester. The coalition government has added the Midland main line (northwards from London St Pancras), the Valley Lines in South Wales, a short link in north-east London, and the Electric Spine, for freight movements between Southampton and the North.
The final section of the Electric Spine into Southampton will feature overhead electricity supply along a route currently electrified at ground level using a ‘third rail’, a system widely regarded as inferior. This raises the possibility that the dense railway network south of the Thames will be converted progressively from third-rail to overhead electrification.
To erect the wires west of Manchester, Network Rail is using ad hoc methods that involve shutting lines at weekends and bank holidays, to the annoyance of passengers who find themselves displaced onto buses.
On the Great Western main line, such disruption would affect many more people, generate negative headlines and cost Network Rail a small fortune in compensation, payable to train operators for each cancelled train. Therefore Network Rail hatched the concept of delivering all the materials, components, equipment and staff to each work site on a purpose-built factory train, which would double up as a safety barrier to allow trains in normal service to pass the workforce on the adjacent line.
Preparing for engineering work, and the later process of handing back the railway for use, accounts for a large proportion of the time in a typical ‘possession’ or line closure. The self-contained nature of the High Output Production System (Hops), as the factory train is known, will greatly reduce that unproductive time. That will make it feasible to carry out electrification work in eight-hour nocturnal possessions through the week. This will close half of the main line at the work site, but the other half will provide sufficient capacity for the relatively sparse night-time traffic.
Windhoff, a German company specialising in manufacture of rail machinery, is supplying the Hops at a cost of almost £40 million. The system will consist of 14 self-powered multi-purpose vehicles (MPVs) with driving cabs and nine wagons. These will be deployed in various combinations, according to each night’s work schedule.
Some of the MPVs are configured for driving any number of Hops vehicles, coupled to form a train, at up to 60mph on lines open to normal traffic. On arrival at the site, the train will divide. Driving cabs on each module will enable staff to move their equipment and materials along the work site, at up to 20mph. The on-board machines, including cranes and pile drivers, will function without being removed from their host rail vehicles.
Each module will handle a distinct stage in the process. First comes a module for piling, using two Movax vibratory pile drivers, one at each end of the wagon that carries the steel piles. For ground conditions where vibration is insufficient, the module will include a vehicle with a hydraulic percussion hammer. Other vehicles, carrying an excavator and cement mixing plant, are for concrete mast foundations.
German manufacturer Windhoff has supplied similar rail-mounted machines to other countries
Next down the track will be a module for erection of the steel masts to hold up the overhead cables. This will be followed by a module for installing the feeder and earth cables towards the top of the mast and the small-part steelwork, such as cantilever, to hold in position contact and catenary wires above track.
The next module will deliver the two above-track cables: the tensioned cable from which trains will draw power, and the catenary above it. Both are installed simultaneously. Traditionally each length of overhead conductor is tensioned after installation, but the Hops has a tension control system which enables the wires to be anchored at the start of the wire run and installed already at final tension. This drastically reduces the time required. Previously each fixing point and dropper would require adjustment after the wire run was tensioned, having been temporarily attached on the first pass.
A module for measuring newly installed equipment will bring up the rear of the Hops. This will feature a contactless measuring system and raisable platforms for close-up inspection of the installation.
The modules will be based in Swindon. During the day they will be serviced, and configured and stocked for the coming night’s work. The modules for the earliest processes will be marshalled at the front of the train for nights when the work will progress away from Swindon, or at the rear when work progresses towards Swindon. On site, as one module completes its task and moves on, the following module will take its place to attach the next components.
If piled foundations could be provided for each of the 17,000 masts, all of the modules could be deployed as one train. The inevitable requirement for some concrete mast foundations dictates that the first module will work a month or more ahead of the others, allowing time for the concrete to cure. Foundations will also be installed at this time using traditional methods at stations, where access by road is usually straightforward.
Robbie Burns, Network Rail’s regional director of infrastructure projects, says the target is to install 1.2km to 1.5km of electrification equipment each night. This equates to one complete length of tensioned conductor cable. The overall time required to electrify the Great Western should be halved, at least. It needs to be, as the government has announced the commencement of electric services to Oxford, Newbury and Bristol in 2016, Cardiff the following year and Swansea in 2018. The economics of this scheme, especially the Swansea extremity, also rest on the financial savings that the Hops will deliver through superior efficiency.
Pinning so much on new technology looks at first sight like a gamble, but Manfred Schmitz, Windhoff’s managing director (technical), says his company has supplied the various rail-mounted machines to other railways around the world. Windhoff’s principal innovation for Network Rail is the system of enabling work to proceed while the adjacent track remains open to passenger trains.
Locks will prevent equipment arms or steelwork straying outside the safety envelope at the site. The Hops vehicles will form a barrier between the danger from passing trains and workers on the ground.
The benefit of the Hops’ self-sufficiency is clear when one considers that 430km of the busy Great Western route are to be electrified. Supplying materials by road would be impractical or require negotiations with numerous landowners and construction of temporary access points.
The first Hops modules will arrive in England in October. Amey will operate the factory trains.