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Rehabilitation and upgrade of a leaking DN 225 uPVCClass 9 water main

Task:
The Lismore City Council was confronted with the rehabilitation of a leaking DN 225 uPVC Class 9 water main located at Elizabeth Street. The first section of the pipe runs downhill into a gully with a length of 170 m and a height difference of approximately 35 m where a scour valve is located. The second section runs from
the scour valve uphill with a total length of 290 m and a height difference of almost 50 m. The pipe coverage was up to 3.8 m and power supply lines were in proximity to the construction site. Therefore, the Lismore City Council was looking for a trenchless solution that could repair the leaking pipe, increase the pressure rating to 16 bar and maintain the hydraulic capacity.

Rehabilitation System:
The client opted to renew the leaking water main with the Primus Line® system, a proven solution for the trenchless rehabilitation of pressure pipes. The AS/NZS 4020:2005 certified three-layer composite liner consists of a PE inner coating, a Kevlar® core to accommodate the operating pressure, and an abrasion-resistant PE outer layer to protect the Kevlar® core during the installation process. The semi-structural solution is not bonded to the host pipe, can traverse bends of up to 45 degree, and can be inserted in lengths of 1,000 m and more in one single pull. Furthermore, due to the low wall thickness of only 6 mm compared to corresponding HDPE pipes, the hydraulic capacity is almost maintained.

Project Description:
Orion Group (now part of Mainmark Civil & Mining Services) was the successful bidder. The alternatively proposed sliplining with HDPE would have reduced the diameter to 147.2 mm. The installation was planned to be performed in two sections with 170 m and 290 m. In a first step, the pipe was secluded from the network, three excavation pits were erected, and the scour valve at the bottom was removed. A pipe cut-out of 2 m was created to get access to the host pipe.

Subsequently, a CCTV inspection was performed to assess the condition of the host pipe, but also produce the rope connection between the start pits and the destination pit. The condition assessment revealed two damaged sections of the uPVC host pipe that were repaired with patch liners. Furthermore, the inspection revealed multiple 15 degree bends in the route of the pipeline that were not accounted for in the as-built drawings. Due to the liner’s flexibility, the installation could commence without any variation. The liner with an OD = 203 mm, a corresponding ID = 191 mm and a nominal pressure rating of 35 bar, was manufactured in Germany and coiled pre-folded onto two timber transport reels.

The installation was realized with approximately 4 m/min. After the liner was tension-free, compressed oil-free air of 0.5 bar was applied to turn the liner into round shape. The four end fittings equipped with flanges AS 4087 PN 16 were installed under the supervision of a Primus Line technician and mounted to a flange coupling adaptor at the PVC host pipe. Finally, the line was disinfected, pressure tested and reintegrated into the water main network. The service life of this water main was extended by at least 50 years. 

Exhibitor: Rädlinger primus line GmbH

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