More reline firsts for Lanes

Lanes for Drains notched up a double industry first by relining the foul water main suspended beneath the Conwy road bridge in North Wales.

The sewer, which serves the historic castle town, was a pressurised pumped sewage main — a type which has not been relined before. And, to add to the challenge, the 300mm diameter pipe changed shape after 58 metres, from round to rectangular then back to round again.

Andy Brierley, managing director of Lanes’ sewer renovation division, explains why this reline project is so important for the industry:

“Only gravity (non-pressurised) sewage pipes have been successfully renovated before using the reline, or ‘no-dig’ method. And, to my knowledge, although we have installed liners in boxed pipes before, lining one that changes shape part way is another first. The boxed section also contains an ‘S’ bend as well as three air release valves, but we were confident that we could do it.”

The pioneering project came about because Daniel Contractors, in partnership with United Utilities, was looking for a solution to the problem of the deteriorating sewer on behalf of Welsh water utility, Dwr Cymru. Daniel’s design manager, Martin Williams, explains:

“The pipe was quite badly eroded inside and bird guano was eating through the metal from the outside. Something needed to be done promptly, because there were environmental concerns about possible leakage into the water below but replacing the pipe completely would have been a last resort: from a health and safety point of view we didn’t want to have people working on mezzanine platforms suspended 200 feet above the estuary, but also the cost would be prohibitive.”

Fortunately, Martin knew that Lanes was looking at the possibilities of relining pressurised sewers using a reduced thickness liner, and, although it had not been done before, Daniel Contractors, United Utilities and Dwr Cymru, were all keen to take Lanes’ innovative option.

Together they scoped the project and a schedule of work was agreed. Lanes imported the special glass reinforced liner from Belgium, and every last detail was planned meticulously. For Martin, the project was a resounding success:

“Beforehand we carried out all the preparation work and set up overpumping to ensure continuity of service during the works. On the day, Lanes reline crew began mixing the resin at 6 am, and the liner was installed, cured and finished off by 4pm — just 10 hours from start to finish. It could not have run more smoothly.”

Lanes used an air inversion unit to force the glass fibre weave liner through the pipe after it had been impregnated with the special 2-pack epoxy resin. Through a CCTV camera crawler unit, the team was able to watch the liner moving through the pipe — especially important once the liner reached the boxed section.

Says Andy Brierley:

“The reduced thickness of the liner meant less chance of creasing at the bends and helped the material take the shape of the host pipe: it was just a matter of adjusting the pressure to force the liner outwards. And it worked like a dream.”

Once it gone through the full 161-metres, the liner was steam cured for around three hours before the boiler was turned off and cool air pumped through for a further two.

Finally, the reline crew cut down the liner and inserted the sealing bands before handing the project back over to Daniel Contractors, whose client was delighted with the results — and the considerable cost saving of relining the pipe instead of replacing it.

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