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TRENCHLESS TECHNOLOGY

Designer liner proves perfect solution for pump station

The Danish infrastructure firm Per Aarsleff’s new pipe division has carried out a cost-effective – and environmentally friendly – lining project in Suffolk. UK managing director, Terry Bolsher, explains the process

coast. The deformed and leaking cast iron pipeline was quickly restored with an Aarsleff cured-in-place resin impregnated polyester thin walled one piece liner, forming a joint free, leak proof smooth bore pipe within a pipe. Bawdsey land drainage pumping station and its 450mm diameter discharge pipeline were built in the late 1950s to serve an agricultural catchment of nearly 13km2, half of which lies at (or below) mean sea level. The station automatically controls water levels and discharges surface water drainage through the pipeline, under a flood defence embankment and into the tidal estuary of the River Deben. The overall pipe is about 30m long, but the 22m long section, from the pumping station to the outfall, has deformed under the weight of the embankment and sunk about 250mm into a shallow ‘U’ shape. When the pump operates at its flow of 0.45m3/s and pressure head of 5m, water is forced out of the damaged pipe’s open joints, jeopardizing the integrity of the flood defences. A swallow hole appeared in the embankment, forcing the Environment

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Agency, which is responsible for the embankment, and the East Suffolk Internal Drainage Board (ESIDB), responsible for Bawdsey Pumping Station, to act quickly. The ESIDB is one of a consortium of five boards making up the Water Management Alliance (WMA), which together protect about 1,220km2 of East Anglia. There was an acute risk of an embankment breach and the WMA looked at alternative repair options. “We had to act quickly and considered various alternatives, including

replacing the entire section of pipe, but that would have required major invasive surgery to the embankment,” says WMA district engineer Ian Hart. “Instead we opted for a less invasive option of relining the pipe without the need for any excavation, in the spirit of modern, keyhole surgery. “I contacted Aarsleff and they confirmed the feasibility of repairing the pipeline insitu with a tailor made liner. We then appointed the local civil

18 Water & Wastewater Treatment May 2010

er Aarsleff’s recently formed pipe technologies division has successfully completed its first pipeline repair on a damaged pumping station discharge pipeline at Bawdsey, on the East Suffolk

engineering contractor Breheny to oversee the repair as they had rebuilt the pumping station in 2003/4. Aarsleff purpose made the liner to suit and installed it in a very slick and professional operation.” Breheny provided clear unobstructed access to the pump house,

removed the pipeline inspection cover within the pumping station and opened the outfall flap valve to allow Aarsleff to make a start on the lining during low tide. A thin plastic pre-liner, with a blanked end, was first inserted into the damaged pipeline using compressed air to protect the main resin- impregnated polyester liner during installation. The main liner was designed and made by Aarsleff’s in-house designers

to withstand the positive and negative pressures and the high flow rates generated when the pump operates. It was made inside out from resin impregnated thin layers of special needle felt so that the outside surface eventually became the inner smooth bore surface when the liner was inverted into the damaged pipeline. The main liner was packed in flake ice during delivery from the factory to site to prevent premature curing. At the pump house the liner was wound into the special inversion drum, which was positioned close to the pump house entrance. A length of liner, twice the distance from the drum to the pipeline manhole, was pulled out of the drum. This protruding section was then turned back on itself so the inside of the liner was now on the outside. It was pushed onto the outlet nozzle of the inversion drum and held in place with special clamping bands. The liner was then lowered down into the manhole and guided by hand a short distance into the pre-liner and into the entrance of the damaged 22m long pipeline. The inversion drum was then pressurised with compressed air, which

forced the liner, with its closed end, to rapidly unwind from the drum and unfold and invert itself through and out of the open end of the damaged pipeline. The inversion process only took a few seconds with the air pressure forcing the liner through the prelined damaged pipe and against the wall, which effectively acted as a former for the new lining. Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64