Key to PipeWorks’ approach to CIPP installation is the application of robust management procedures that ensure health and safety, and that operational, quality and environmental performance meets industry best practice standards. The company’s systems and procedures are based on those of parent company, Fletcher Construction, the largest and leading infrastructure contractor in New Zealand.
In the last two years PipeWorks has carried out two major projects for Tauranga City Council involving the installation of approximately 1,700 metres of CIPP liner ranging from 375 mm to 900 mm in diameter. The rehabilitation of the pipelines was required due to severe erosion of the existing concrete pipes, resulting from sulphide attack.
Located in industrial areas, some alongside major arterial roads, rehabilitation of the pipes was a complex process, which involved bypassing trunk sewer flows of up to 300 litres per second.
Carrying out the CIPP process involves impregnating a polyester felt-liner tube with resin to ready it for installation into an existing host pipe. The installation is carried out using water pressure to invert the liner into the hosepipe. That water is then heated to cure the resin, resulting in a structural pipeline along the existing alignment. The finished product is a strong and durable stand-alone pipe, with a design life well in excess of 50 years.
Article continues below…For the Tauranga projects, the liners were wet out in Auckland the day before installation then trucked to Tauranga using open topped containers. Logistical preparation extended so far as to ensure that the trucking company taking the load had other vehicles available should mechanical failure occur en route.
When operating in larger diameter pipes such as these, a significant part of the process is bypass pumping of the sewage or stormwater flow. The largest flow that PipeWorks has bypassed is 650 litres per second. In Tauranga the dry weather flow to be bypassed was between 250 litres per second and 300 litres per second. Bypass pumping is a major challenge, as once a liner is installed, the process must run its course. Careful design of the bypass system was carried out in-house and sufficient redundancy was put in place to cover for any unavoidable mechanical failures.
Installation and curing of the liners took between 24 and 36 hours. This allowed for inversion, and then a long heating time to ensure proper curing followed by cool down and cut-out to complete the exercise. Post-lining CCTV inspection was carried out prior to the bypass being taken out.
The successful delivery of these major CIPP liners, and the ensuing satisfaction of the client, is testament to the experience and dedication of the PipeWorks team involved.
