In late 2017, Queensland Urban Utilities (QUU) investigated the rehabilitation of a DN 600 glass fibre reinforced plastic (GRP) trunk water pipeline at Redbank Plains. The utility identified a 1.8 km complex stretch that needed to be renewed; the section of pipe included two scour valves, two air valves and two 45° bends.
At the time, it was the longest and largest stretch of pipe relined using the Primus Line system in Australia.
As this particular section ran through a residential area and a park, QUU opted for a trenchless technology method to minimise disruption to the community and the environment. The utility also considered that relining could be faster and more cost-effective option than traditional open trench replacement for this project.
“The Primus Line system is a flexible lining system, which takes the internal pressure off the host pipe, but relies on the existing pipe having structural capacity to withstand external loading,” says QUU Water Network Program Director Gavin Flood.
“We inspected the pipe at Redbank Plains and confirmed it was structurally suitable for another 50 years, so we saw this as a great opportunity to trial Primus Line.”
Mr Flood says the utility considered a number of other trenchless methods for the rehabilitation, before settling on the product.
“We considered using sliplining, but our analysis found the Primus Line system would be more cost effective and have a smaller construction footprint in this case,” he says.
“The project was in a residential area, so relining meant we only had a small construction footprint and were able to minimise the impacts on the community, factors which are typically critical and limiting in pipeline renewal projects. Instead of our crew spending months digging up the existing main and replacing it with a new one, we completed the project in a matter of weeks.”
Rehabilitation system
The Primus Line® system is referenced in EN ISO 11295:2018-06 and EN ISO 11298-1:2018 for the renovation of underground water supply networks and complies with AS/NZS 4020:2005. The system consists of a Kevlar® reinforced liner and specifically developed end fittings.
The liner accommodates the operating pressure of the pipe, due to the reinforcement layer and because it does not bond to the host pipe. The liner is seamlessly manufactured at an ISO 9001 certified production plant in Germany and transported on reels to the site.
Due to the flexibility of the material, the liner can traverse angles of up to 45°, can be installed in lengths of more than 1,000 m in one pull and has an installation speed of up to 600 m/h.
Installation
To minimise the construction footprint, the relining was completed in three separate installations of approximately 600 m each. This also reduced the amount of time needed to set up the transport reels and pulling winches.
There were a total of eight excavation pits:
- Two start pits, sized 2.15 by 1.8 m, where a 1.75 m section was cut out of the host pipe.
- Four intra-pits, sized 2.9 by 1.8 m, where the valves and tees were located and a 2.5 m section of the host pipe was removed.
- Two destination pits, where the liner was pulled out at a flat exit angle of 10° to minimise the pulling forces.
Custom fittings were used to avoid the need for tapers, with DN 500 connectors delivered with a DN 600 flange on the outer sleeve, which was mounted to a DN 600 flange coupling adaptor at the host pipe. After the excavation pits had been created, the host pipe was inspected with CCTV and cleaned.
Following reinspection of the pipe, the installation process began and the pre-folded liner was inserted using a pulling winch. Once in place, the liner was returned to its original round shape by applying 0.5 bar of compressed air.
Once the end connectors had been installed, the renovated section was pressure-tested at 12 bar and disinfected. The rehabilitation extended the life of the water main by at least 50 years.
Self-performing
The trenchless rehabilitation was unique because the crew was one of the first to train in installing the Primus Line system in Australia.
“Our capital works crews were specifically trained to use the technology in the weeks leading up to the installation, so it was a learning process for us. Our crews were enthusiastic and picked up the technique quickly,” says Mr Flood.
“We had Primus Line trainers on site, from Germany, to supervise throughout the installation of the liner. I think it helped having their input along the way to highlight the criticality of each stage in the installation process.”
For more information visit the Primus Line website.
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