Northern Gas Networks (NGN)
Monkwray Brow 6″ main rehabilitation
Products
160 mm SDR17.6 PE80 gas pipe
Background
North of England’s gas distributor Northern Gas Networks (NGN) identified a section of a 6” main at Monkwray Brow in Whitehaven that needed rehabilitating as part of their gas mains replacement programme. The traditional open-cut installation method was initially selected as NGN wanted to retain the pipe capacity.
This particular section of pipe, however, was partly buried under one of the main thoroughfares of Whitehaven and the pipe rehabilitation works would have led to road closures and significant disruption to NGN’s customers. A feasibility study was consequently carried out to determine the suitability of alternative ways of replacing large diameter cast iron gas mains using trenchless pipe installation methods.
The Details
Working closely with Radius Subterra, NGN investigated the use of their Rolldown® relining technique, where a PE pipe’s diameter is concentrically reduced and inserted into the host main. This technique was of particular interest to NGN as once inserted, the PE liner is reverted back to its original size forming a close-fit within the main, providing maximum flow capacity, which was crucial to this particular project.
A 160mm fully structural PE pipe supplied in 100 m coils by Radius Systems was selected as the ideal diameter for the works. The coils were first welded together using Radius electrofusion couplers and inserted in seven sections into the host main. The rehabilitation was carried out successfully, reducing the overall project duration by 6 weeks.
Steve Jones, construction services area manager at NGN commented: “we know that no one likes roadworks and we’re always looking for innovative ways of working to minimise the disruption caused to customers as a result of our works.
“The Radius Subterra lining technology allowed us to renew the ageing metal pipe in Whitehaven without the need to dig a trench which meant that we completed the job much quicker than using traditional methods.
“We are one of the first gas utility companies to use this technology and we’re delighted with the results. We’ll certainly be looking to adopt the approach on similar projects and we’ll be sharing the results with the rest of the industry.”
