High output… and high value
Network Rail’s High Output Ballast Cleaning trains have revolutionised this aspect of track maintenance over the past decade, earning it a National Rail Award for Sustainable Development. BEN JONES discovers how the trains work and what benefits they deli
At around half-a-mile long, they are the biggest trains on the British rail network (longer even than Eurotunnel’s Le Shuttle trains), performing a vital function away from the public gaze.
Network Rail’s award-winning fleet of High Output Ballast Cleaning System trains (HOBCS) has been steadily growing since 2005, allowing the organisation to increase the sustainability and efficiency of track maintenance, reduce its consumption of new ballast, and improve safety at work sites.
Greater demand for train services over the past 20 years has presented NR with the conflicting requirements to keep railways open for longer while undertaking more frequent track maintenance and renewals.
The network owner’s Infrastructure Projects (IP) division has a dedicated High Output team tasked with renewing track and ballast efficiently and with as little disruption as possible. The HO team now carries out around 70% of Britain’s track renewal work, with a budget of £ 700 million. And its teams are active on the railway every night, carrying out vital renewals overnight that used to occupy entire weekends.
Ballast is quite literally the foundation upon which our railways run. It requires regular attention to ensure it is performing as it should - supporting the sleepers and rails and providing effective drainage to prevent ‘wet spots’ that can lead to poor ride quality and broken rails.
Over its 20-year life, ballast gradually loses its effectiveness as the individual pieces of stone are ground down by vibration movement, creating smaller particles known as ‘fines’.
Mixed with water, these ‘fines’ can eventually create a concrete-like substance that further reduces the ability of the ballast base to disperse water and support the track. While NR’s stoneblower fleet has done much to eliminate gaps and weak spots under the track across the network, there comes a time when more fundamental action is required.
Main line track is expected to have a 40-year working life, twice that of the ballast, and it is the responsibility of NR’s High Output team to regularly clean the ballast without replacing the whole track. One of HO’s priorities is to remove the ‘fines’, requiring the ballast to be thoroughly cleaned while at the same time removing damaged stones that have lost their angularity.
HOBCS trains excavate ballast from beneath the track while the track is held in position by hydraulic arms. The machine scoops out the excavated material and passes it through large vibrating screens, removing any damaged ballast and returning larger pieces to the track.
Ballast is fed into the track immediately behind the excavating cutter bar, bringing forward new ballast from the loaded wagons. Integrated tamping and Dynamic Track Stabiliser machinery improves the track geometry as the whole system moves along the track, making use of track geometry management systems to replace the track very precisely.
Because there is no need for wagons on the track alongside the machine, the adjacent line can remain open, thus minimising disruption. The removed spoil is taken back to a High Output Operations Base (HOOB) for processing and then on to specialist facilities to be recycled as roadstone.
Costing £40m-£ 50m each, the five RM900 RT trains, delivered by Austrian on-track plant specialist Plasser & Theurer in 2005, 2007, 2010, 2013 and 2017, are part of a £ 300m investment in high output equipment over the past 12 years.
For example, the 800-metre 2008 train cost £41.7m and is capable of cleaning 550 metres of track per eight-hour shift. NR now has the third largest fleet of such trains in the world, behind Germany’s Deutsche Bahn and Austrian maintenance contractor Swietelsky.
Each train has 22 wagons fitted with conveyors for ballast waste and another 22 loaded with fresh ballast, as well as diesel power cars that allow the trains to move under their own power on site, ballast cleaning, plus integrated tamping and Dynamic Track Stabliser (DTS) machinery.
Of the 44 material conveyor/hopper wagons, 36 are MFS-D through-loading vehicles and eight are MFS-SB wagons with a conveyor belt that can be slewed for unloading. Cleaning output is 900 cubic metres or 400m of track per hour.
Freightliner has the contract to transport the HOBCS sets to and from worksites. Two Class 66 locomotives top-and-tail the trains, which are based at strategic locations on NR’s Western, Anglia, Scotland, Wales, London North Western and South East routes.
The latest train (BCS5) was delivered by Plasser & Theurer in 2017 at a cost of £ 50m, and incorporates the latest technology, fully automatic wagons, reduced fuel consumption and emissions. BCS5 enables a further
100,000 tonnes of ballast material to be reused every year.
To meet environmental targets it also uses biodegradable oils, diesel particulate filters to cut noxious gas emissions, and eliminates no fewer than 44 diesel generators from the material handling wagons. Dust is also reduced by spraying a fine mist of water across the materials.
BCS5 is also the first HOBCS train equipped with a double bank consolidation machine and new ballast manipulators designed specifically for working on Southern Region 750V DC third-rail lines.
A major advantage of HOBCS over traditional ballast cleaning methods is greatly increased safety for lineside staff and operators. All working positions are in safe locations, while noise-insulated cabs increase safety and reduce exposure to noise and dust, as well as eliminating any need for working at height. BCS5 takes this to a new level with fully automatic materials handling wagons, removing the need for staff on the track.
HO employs around 1,200 people on frontline work and in its York and Birmingham offices, plus seven operations bases ranging from Millerhill in Edinburgh to Taunton and Eastleigh in the south of England. It also has five delivery depots at Newcastle, Doncaster, Crewe, Bletchley and Swindon.
In March 2015 Network Rail took greater control of its HO operations by bringing more than 500 AmeyColas contractor staff in-house - the largest intake of staff since maintenance activities were brought in-house in 2005.
HO planners ensure that the machines are in the right place at the right time to make the most of possessions. A 24-hour cycle includes preparing the trains, removing lineside equipment (and replacing it afterwards), transport to sites, and bringing back and unloading the old materials.
On a typical night, possession of the track is taken at 2230 and handed back at 0600, with the HOBCS working from 0030 to 0200. While this sounds a surprisingly short window of activity, the rest of a possession is taken up by isolating signalling and electrical equipment, digging entry holes, disconnection of cables from track, and putting it all back afterwards.
Due to the high volume - and cost - of ballast, Network Rail aims to reuse as much as possible. HOBCS has allowed it to reuse approximately 2.6 million tonnes of ballast over the past decade, providing both environmental and economic benefits.
The trains help Network Rail’s IP division to meet strict targets for reducing carbon emissions, waste to landfill, and consumption of resources.
Ballast cleaners avoid the unnecessary disposal of reusable ballast, which represents around 40% of the material excavated. This alone has saved £ 9m over traditional methods of removing old ballast.
Prior to the arrival of the newest train in 2017, the four HOBCS trains averaged 70 linear kilometres per annum, which equates to approximately one million tonnes of ballast.
Of that, 400,000 tonnes was re-used on site, minimising unnecessary waste. And more than 95% of the remaining 600,000 tonnes was recycled by NR’s National Supply Chain and sold on for other uses such as road building, further helping to offset costs. However, on occasions all the material excavated is rejected and removed from site to landfill or re-processing. Some sites have higher quality ballast, and around 60%-70% is cleaned and returned to the track.
Recycling also cuts costs and environmental impact by reducing the quantity of ‘virgin’ material required from quarries such as Mountsorrel in Leicestershire.
Importantly, HOBCS also allows the affected lines to be handed back to operators at higher line speeds, ensuring capacity is maintained and reducing energy costs from braking and accelerating at temporary speed restrictions.
Complex and capable machinery such the HOBCS does not come cheap, but the efficiencies it can bring to the maintenance and renewal of busy railway lines should not be underestimated. Its recognition by RAIL’s National Rail Awards judges this year shows that it is playing a significant role in helping Network Rail to deliver effective, high-quality maintenance in a sustainable, responsible manner.
A major advantage of HOBCS over traditional ballast cleaning methods is greatly increased safety for lineside staff and operators.