CIPP relining success in Essex
A pipe relining project for Anglian Water involved cured-in-place technology, explains Philip Woodcock, Aarsleff Pipe Technologies' general manager
Per Aarsleff UK's specialist Pipe Technologies Division has successfully completed the relining of 2.8km of foul sewers in only 22 days, as part of Anglian Water's Basildon & Billericay Sewer Rehabilitation scheme in Essex. The different lengths of sewers, in various diameters at nearly 50 different locations, were quickly renewed with Aarsleff's CIPP cured- in- place resin- impregnated polyester felt liners, forming joint- free, leak- proof smooth bore pipes within a pipe.
Per Aarsleff was working for framework contractor Barhale Construction, as part of the @One Alliance delivery partnership for Anglian Water. One of Aarsleff's experienced installation teams came over from Denmark for the Basildon project to beat by nearly 40% the client's production target requirement of two liners a day.
They averaged 2.75 liners a day and on one day installed four liners. The required 46 liners ranged in diameter from 150mm to 450mm and lengths from 15m up to 136m. Aarsleff completed the lining in two visits and with an interval of two weeks. Prior to starting the lining, Aarsleff's Danish team had to go through a training programme to work in the UK. In addition its purpose built installation and steam curing equipment was tested and approved for working to UK health and safety requirements.
"Aarsleff is a very experienced outfit and has worked extensively throughout Europe, but had to adapt to UK requirements and legislation, which they did quite well," says Barhale contracts manger Richard Beecroft. "I found Aarsleff to be a very professional operation and the standard and quality of their plant and equipment and welfare was first class, setting a new benchmark for their UK competitors."
Aarsleff employed contractor JK Environmental to perform detailed CCTV inspections and initial cleaning to determine a programme ofrenovation. Typically at each installation, a thin plastic pre-liner, with a blanked end, was first inserted into the damaged pipeline using compressed air to protect the main liner during installation.
The main liner, manufactured by Aarsleff, was made inside out from special resin impregnated needle-felt, so that the outside surface eventually becomes the inner smooth bore surface when the liner is inverted into the damaged pipeline. The main liner was packed in flake ice during delivery from the factory to site to prevent premature curing.
A purpose-built lorry, fitted with the necessary installation equipment, including the boiler and compressors, was taken to site. The liner was wound into the special inversion drum, inside the lorry. A length of liner was pulled out of the drum and 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 pipeline.
The inversion drum was then pressurised with compressed air, which forced the liner, with its closed end, to unwind from the drum and unfold and invert itself through and out of the open end of the damaged pipeline. The inversion process forced the liner through the pre-lined damaged pipe and against the wall, which effectively acted as a former for the new lining. A steam pressure hose was then connected from a special boiler inside the lorry to the inversion drum to heat up the liner.
At the same time a steam exhaust pipe was also inserted into the exposed section of liner protruding from the exit manhole.
Temperature probes were attached to the liner, which was gradually heated by the steam to 110°C and, depending on the pipe diameter, held for specific periods to cure the liner. The entire liner inversion and curing process was controlled and monitored by a computer on board the lorry.
After curing and cooling, the ends of the new liner, which formed a selfsupporting pipe within a pipe, were cut off.