Subterra’s revolutionary Subline technology put to the test with ProFuse peelable pipe

Subterra’s revolutionary Subline technology put to the test with ProFuse peelable pipe

Subterra has successfully renovated an ageing 18" spun iron medium pressure gas main in Castleford using their innovative Subline diameter reduction close-fit pipe relining technology with Radius Systems' 450 mm ProFuse peelable pipe - a first in the UK.

Although the 18" spun iron pipe, located on one of the Castleford to Wakefield main roads, had already been earmarked for replacement using traditional open-cut installation, a nearby local housing development under construction prompted Northern Gas Networks (NGN) to take immediate remedial action on the main on safety grounds. The pipeline was buried under a busy highway and the infrastructure around the pipeline made it difficult to use traditional installation techniques. NGN had already seen the benefits of using the Subline technology and decided that this particular trenchless installation technique would greatly benefit this project by minimising disruption to the local community.

This innovative solution involves the concentric reduction of the diameter of a PE pipe through a set of specially designed profiled rollers. The original PE pipe diameter is selected to be slightly greater than the internal diameter of the existing main. It is butt-fusion welded into long strings, processed through the Subline machine and inserted into the prepared host main. Once the insertion is complete, the pipe is pressurised using cold water to regain its original size, forming a close-fit within the original gas main and providing maximum gas flow capacity.

Warren Iveson, construction services area manager at Northern Gas Networks said: "We wanted to do everything we could to minimise disruption to members of the public and limit traffic management and the Subline technology was the ideal solution. Using the technology has allowed us to be more efficient and reduce the project time, but also to investigate the potential application of this method on other schemes which would benefit NGN and our customers."

The reinstatement of the Castleford 18" main using ProFuse pipe required Subterra's engineers to carry out extensive development work to ensure the feasibility of processing the peelable pipe. They determined that ProFuse could be processed in the same way as a solid wall pipe by taking careful consideration when peeling the pipe ends for butt-fusion jointing and using a different gas industry approved lubricant during the operation. The 450 metre length of ageing cast iron main was successfully relined in two sections, minimising the number of excavations required and reinstatement costs. Using this innovative method, the overall project duration was shortened by four weeks, causing less disruption for road users and pedestrians as well as saving over 100 tonnes of environmental waste, improving efficiency and reducing costs.

Northern Gas Networks are investing £90 million per year in its gas mains replacement programme which will see around 3,800 km of old metallic gas mains replaced by 2021.

For more information on our Subline close-fit PE pipe lining solutions, please contact us on t: +44 (0)1773 582317, e: or visit our website