Sustainable FFU on Kent’s Military Canal & Blockhouse Bridges
Sekisui celebrates 10 years since the first installation of its synthetic wood on network rail and over 44 years of use worldwide.
Since 1980, Sekisui has engineered and manufactured synthetic wooden sleepers made from Fibre-reinforced Foamed Urethane (FFU). In 2014, Network Rail engineers installed the first FFU baulks and cross-sleepers as replacements for traditional hardwood on Military Canal & Blockhouse Bridges in Kent. Since then, FFU has been used to provide track support on more than 65 railway bridges in the UK & Ireland.
The FFU product was first introduced on Japanese Railways in 1980 and early installations are still performing to specification. FFU is now widely used on railway infrastructure in 33 countries globally to support track on bridges, decking for level crossings, plain line sleepers, and Switch and Crossing (S&C) bearers.
Recently, Sekisui was invited back to site in Kent to meet with Network Rail’s Track Maintenance Engineers (TMEs) Greg Harrison and Paul Furnival. The pair were responsible for fitting out the two railway bridges on the Ashford to Hastings line, with longitudinal baulks and cross-sleepers manufactured from FFU.
Accepting the challenge
Sekisui learned that the Military Canal was built between 1805-1809 as a defensive structure designed to protect against possible invasion by Napoleon’s Army. Such an attack never happened, but the canal still acts as an essential form of irrigation and provides drainage to much of the surrounding marshland. The bridges over these waterways provided a great location for the first Network Rail installation of FFU.
During September 2014, the TMEs completed the FFU installations at Military Canal Bridge 1800A (ELR: ATH 62miles72 chains) & Blockhouse Bridge 1800B (ELR: ATH 62miles 75 chains). The bridges are of an open steel-framed construction, and both have twin tracks. The Military Canal bridge has a length of 29.5 metres and Block House bridge has a length of 13 metres. In total, six pairs of FFU longitudinal baulks, measuring 410mm x 370mm x 7.45 metres, were used to replace the life expired timber waybeams.
The FFU product was manufactured in Japan to the required tolerances for precise installation. The cross-sleepers were then positioned on top of the longitudinal baulks and milled to achieve predefined track geometry prior to re-fitting the baseplates and rails.
Sekisui was honoured to be invited back to site to gain some feedback from a customer’s perspective some 10 years after Network Rail replaced the timber with the synthetic product. Paul said that people were very sceptical about the options when he first mentioned the need to find an alternative to wood, but he felt repeatedly renewing in hardwood every 15 to 20 years was a thankless task. FFU was recommended by Network Rail’s head of track and at that time a trial site was needed. Greg and Paul were in the right place at the right time.
Greg and Paul told us they were proud to accept the challenge of installing this cutting-edge material and to have this project on their portfolios. There was a lot of learning and concerns to be addressed prior to the install, because this was the first of a kind in the UK. Now they both reflect positively on the decision for Network Rail’s Kent track maintenance team to become the trailblazers for FFU in the UK. Following their success, the FFU product has subsequently been installed on many more bridges on Network Rail infrastructure.
After this successful trial, Sekisui was issued with full Network Rail Product Acceptance Certification PA05/06576 for the installation of FFU to support track systems over bridges, including run on and run off sleepers, bearers for guard rails, and gathering rail panels. Sekisui welcomes the opportunity to work with designers to provide solutions for each individual bridge asset. The FFU baulks can be fabricated & milled to meet structure specific geometry requirements, including providing holes, notches, pockets, and variable cross level to individual baulks.
As good as new
The key benefits over hardwood include: longevity with over 50 years’ service life; FFU is form retentive, not prone to splitting or absorption of water; and it also does not rot, or deteriorate in sunlight, and therefore contributes significantly to asset ‘whole life cycle cost reduction’ by reducing maintenance and renewal interventions. The product does not require maintenance inspectors to complete micro-drilling during service life and is fully recyclable.
Paul and Greg told us that the track over the bridges had been maintenance free for the last 10 years, other than for lifting and packing the run on and run off sleepers into the ballasted track. As the photos show, the FFU product has not deteriorated in form and other than some minor fading of the paint.
Greg said: “the material still looks almost as good as new, contrary to how timber looks after 10 years of service when splitting and rotting is often evident”.
The TMEs believed the use of FFU offered Network Rail reduced whole life cost and, by reducing interventions, renewal would not need to be considered for at least 50 years. There was also a view that the annual frequency of inspection of the longitudinal system could be doubled due to the improved reliability of the assets. Based on their experience with FFU on bridges, the TMEs are keen to install FFU level crossing surfaces on their numerous farm and foot crossings. In addition, they are keen to install FFU sleepers and S&C bearers in the future. When hardwood is phased out by Network Rail the engineers think using FFU would naturally become their synthetic choice.
(Right) Paul Furnival
Sekisui would like to thank Greg Harrison (TME Ashford) and Paul Furnival (TME Tonbridge) for choosing FFU in 2014, facilitating the recent site visit, and contributing to this article.
Background
Developed in conjunction with Japanese National Railways, FFU synthetic sleepers are made using a pultrusion process. Continuous glass fibres are soaked and mixed with polyurethane and then hardened at a raised temperature, moulded, pulled, and cut to length. This creates a high-quality material that has the life expectancy of plastic and the weight of natural wood, which can be worked like natural wood.
First installed in Japan in 1980 and adopted for standard sleepers since 1985, FFU has subsequently been installed on numerous projects in Europe over the past 20 years, particularly turnouts and bridges. Up to the end of 2023, there was more than 1,950km of track with FFU sleepers around the world.
Tests of the original 1980 sleepers undertaken by the Railway Technical Research Institute in 2011 predicted that the FFU sleepers could safely continue in use for another 20 years, giving a total life of at least 50 years. FFU sleepers have also been certified by Germany’s Federal Railway Office for use on tracks operating at up to 230km/h and 22.5t axle load.
All photos credit: Sekisui
