Case Studies

Manchester Gas Mains Replacement

  • Sector: Gas
  • Product: PE80 Pipe
  • Client: National Grid
  • Contractor: Balfour Beatty Utility Services

A project to maximise gas flow using trenchless installation methods on a critical stretch of the mains infrastructure in Manchester was hailed as a success thanks to GPS PE80 piping.

GPS PE Pipe Systems worked with the North West Gas Alliance, a partnership between National Grid and Balfour Beatty Utility Services, to carry out the work as part of an ongoing mains renewal programme.

The project, on Hathersage Road in Manchester, concerned a 328m stretch of gas main that serves an area close to the city’s general, maternity and children’s hospitals and the University of Manchester campus. The North West Gas Alliance specified 560mm SDR21 PE80 pipe to line the existing 24” Victorian cast iron pipes to maximise the internal bore, thereby enhancing capacity in the main without cost or disruption of open cut works.

Richard Scott, site manager for North West Gas Alliance said:

 “This is the first time we have used the 560mm PE pipe and previously for this application we would have had to specify 630mm, which would have been too large for the original pipe’s 600mm internal diameter, necessitating open cut works. That would have made the installation significantly more costly, caused greater upheaval over a longer period of time and had environmental implications in terms of removing and replacing road surfaces.  However, as a 500mm pipe would not have provided sufficient capacity, without the new 560mm size there would have been no alternative.  Thanks to the 560mm pipe we have successfully completed the mains renewal in a relatively short trenchless programme and the project will help us achieve our aim of guaranteeing safe and reliable gas delivery for the next 50 years.”

The pipe was supplied in 12m lengths which were butt-fused together to create a continuous string of pipe.  North West Gas Alliance engineers dug an insertion pit and a reception pit at either end of the 328m section and the pipe was inserted into the original cast iron main and pushed through using specialist equipment. 

Additional connections were made using electrofused Frialen couplers to provide back up capacity in the system. Valve connections were made at each end of the section using 560x500mm SlimFlanges, the unique GIS PL3 compliant PE flange adaptors that allow connection of PE pipe to a metal flange/valve of the same nominal bore.

To underpin the integrity of the pipe, the main pipe layer on the project attended a training course to ensure that the electrofusion process was carried out correctly.  The installation was then subjected to an integrity test before the final connection was made.

Bob Walters from GPS PE Pipe Systems commented:

“The use of SDR21 has provided further proof of the increased confidence in PE piping.  It is also a good example of specifying pipes for realistic pressure and achieving sizeable cost savings along the way. Successful completion of this project is another key milestone for the sector and a further demonstration of the versatility of our product range.”

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