A project in Didcot, UK was part of a gas mains relining scheme, in which Radius Subterra used its Rolldown® close-fit lining technology. The gas main needing to be relined was a 12 in (300mm) diameter cast iron medium pressure gas main, located on the outskirts of Didcot, Oxfordshire, UK in what is currently a rural location that is in the process of
being developed into a large housing estate. The length to be lined was a total of 960 m.
This main had a recent burst history, with some 40 m having already been replaced. Rolldown® was the chosen technique for the relining project, using 315 mm diameter SDR21 co-extruded PE100 pipe, supplied by Radius Systems via its framework agreement. The Radius Subterra lining technology was more cost-effective than replacing the ageing pipeline using the open-cut installation technique. Radius Subterra was called upon to clean the host main and insert the liner, after carrying out the diameter reduction. This was followed by reversion of the pipe and pressure testing of the system. This particular project, managed by John Williams from the company’s Hilcote Office, was undertaken for the local gas distribution network.
The Radius Subterra Team Leader Graham Lockett was supported by Stephen Bain and a three-man team from White Utilities Ltd. The Subterra element of work commenced on 1 September 2020, with the work taking just three weeks to complete. Graham Lockett said: “We are happy to say that the project is now finished and the main has been recommissioned! Our customer was very happy with the outcome and is currently looking at other similar projects where Rolldown® can be used, in the near future.”
Concentric reduction of the liner pipe diameter is the key to the Rolldown® operation
Water main replacement
On a further project, when an ageing water pipeline reached the end of its service life and needed replacing to prevent further water quality and pressure issues, asset owner South East Water and construction company The Clancy Group engaged Radius Subterra to explore the feasibility of lining the main to restore its structural integrity and avoid disruption. The cast iron raw water pipeline which links a borehole to a service reservoir was not only heavily encrusted with tuberculation, but also 900 m of the 8 in (200 mm) and 6 in (150 mm) diameter sections located in Tilford Road and Tower Road in Hindhead, Surrey, UK ran under a busy carriageway and through private gardens where access was difficult, bringing further challenges to this replacement project.
Tony Pipe, Project Manager at Radius Subterra explained: “These particular pipeline sections were in fact ideal to replace using a No-Dig technique. We initially explored rehabilitation using our fast-setting spray-liner, Subcote® FLP, however, the number of excavations needed would have hampered entry to properties, which was required at all times. The location and the length of the 6 in (150 mm) diameter section in particular, was the main focus point. What is more, it was critical for South East Water that the 6 in (150 mm) diameter section of the pipeline retained maximum capacity. That is why we established that using Rolldown® to install a PE liner would be the best option.”
Working in partnership with partners White Utilities, Radius Subterra used its Rolldown®
close-fit lining technology with 160 mm diameter SDR17 polyethylene pipe supplied by Radius Systems to rehabilitate the 6 in (150 mm) diameter pipe section.
The gas main liner awaiting installation
Rolldown® can be used for the renovation of weakened and damaged steel, ductile iron, cast iron, asbestos cement and other pipelines to restore structural integrity and maintain pipe capacity and pressure requirements. It uses a PE pipe as a liner, which once inserted and pressurised, forms a close-fit inside the existing pipework. First, the polyethylene pipe is pushed through a set of rollers to concentrically reduce its diameter by around 10% for easy insertion into the host main. Once inserted, the PE pipe is pressurised to revert it to its original diameter, forming a close-fit inside the main. Compared to other lining
techniques, longer lengths of pipe can be inserted in one pull with Rolldown® , making it the ideal solution for the renovation of pipelines crossing roads, rivers, lakes and designated nature sites or for pipework laid in urban areas or congested ground.
Supplied in 12 m lengths, Radius Systems PE100 pipe for the Surrey project was butt-fused into one long 150 m length and inserted in one pull into the host pipe, then reverted to its original diameter. For the 8 in (200 mm) diameter section, Radius Subterra inserted
the 160 mm PE liner using the established slip-lining technique.
The pipeline was then tested and commissioned successfully, and finally reconnected to the existing network. Steve White, District Manager at The Clancy Group commented: “We are really pleased with the outcome of the project, which was undertaken by a team of not only skilled technicians, but also very helpful and hard working.”
Jeremy Dufour, Project Manager at South East Water added: “This project has definitely been a success and on behalf of South East Water, I thank the Radius Subterra team for their work. This scheme was essential to ensuring reliability and longevity of this crucial part of our infrastructure that serves our customers.”
The project which started in July 2020 with an estimated nine week programme. Ultimately the project was completed a week ahead of schedule. www.subterra-pipelines.com
