The award was presented at the International No-Dig 2010 gala dinner held in Singapore on 9 November. This is a significant step for the Australasian industry as it is the first time an Australian pipeline contractor has won the international award.
Chairman of the ISTT, Dr Sam Ariaratnam, presented the annual award, which is judged by members of the ISTT.
The No-Dig Awards raise the profile and status of the industry by promoting the science, practice and advancement of Trenchless Technology worldwide.
A world first
Interflow produced the world’s largest and longest spiral wound pipe ever made – measuring 2,400 mm in diameter and 706 m in length.
The spirally wound pipe was produced as part of the NGRS sewer rehabilitation project in Sydney, Australia for Sydney Water.
Sydney Water awarded Interflow the contract to reline and renew sections of a 2,520 mm diameter sewer trunk main – totalling 5,438 m in length. The project commenced in June 2008 and was completed in May 2010.
A unique set of challenges
The major engineering challenges associated with this project were:
- 1. To produce a liner capable of withstanding the applied loads at such a diameter (2,520 mm diameter host pipe)
- 2. To achieve the required structural strength and maintain an internal diameter of at least 2,400 mm
- 3. Reline pipes with distances between manholes of up to 706 m
- 4. Execute the project without bypassing the sewer
- 5. Execute the project without excavation.
The technology developed to meet this criteria was based on the Ribline product from Sekisui Rib Loc.
Ribline is a spiral-wound PE/steel composite pipe that has an extremely high strength-to-weight ratio.
In order to achieve the required strength at an internal pipe diameter of 2,400 mm a new profile was designed by Sekisui Rib Loc that allowed the structural design to be met using a profile with an overall thickness of only 31 mm. In order to do this the thickness of the steel sections had to be increased by 25 per cent over anything that had been previously attempted.
“To put the strength of this profile in perspective, had a standard CIPP liner been designed for this situation it would have needed to be greater than 50 mm thick,” Interflow said.
To achieve the structural requirement with a liner of 31 mm thickness meant that the liner needed to be installed with an annular space no greater than 58 mm to meet the minimum diameter specification.
This was a significant reduction in the typical allowance that is made when attempting to spiral wind liners of this size.
The process for spirally winding the Ribline liner
Ribline profile from a spool, above ground, was fed into a hydraulically powered winding machine positioned inside an existing access chamber.
The strips of profile were extrusion welded together inside the winding machine to form a high-strength, light-weight, water tight pipe. As more profile was fed into the machine the newly-formed pipe corkscrewed its way to the next access chamber.
“Up until this project the practical limitation for the maximum length and size of pipe that could be produced using this spirally wound technique was governed by the torque of the winding machine and its ability to overcome the weight and frictional forces of the newly wound pipe as it rotates inside the host pipe,” Interflow said.
In order to produce a 706 m length of pipe liner with a 2,400 mm internal diameter and an annulus of only 58 mm in a single shot, this existing limitation had to be overcome.
The key to meeting this challenge was developing new flotation technology.
The use of flotation to assist spiral-wound liners is not new; however controlling the flotation forces in situations where the flows in the pipe are highly variable presents a more complex challenge.
As such, Interflow’s goal was to develop a flotation technology that was capable of controlling the flotation forces by diverting flows between the inside of the liner and the annular space.
As a result, the volume of water inside the newly formed pipe and the amount flowing between the new pipe and the host pipe was able to be distributed – enabling the newly formed pipe to have neutral buoyancy at all times, irrespective of the changing flow conditions in the sewer system.
In doing this, the frictional limitation on the maximum length of pipe that can be produced was eliminated.
Using flow and buoyancy calculations, Interflow engineered a novel diversion device that enables buoyancy to be controlled as the pipe is being produced.
Using this device, a continuous length of liner of 706 m was able to be produced. Despite having 706 m of pipe continuously rotating (a mass of over 120 tonnes) the torque levels on the winding machine were very low, indicating that the maximum possible length is much longer still than the 706 m achieved in this project.
New innovations for an innovative industry
Interflow believes that this technology has made a significant advancement to these limits, which will open up new opportunities for the industry.
Managing Director Geoff Weaver said, “This international achievement is a testament to the strength and experience of the trenchless industry here in Australia. Sydney Water, like many other Australian Water Authorities, actively encourages innovation by challenging contractors to provide solutions to problems with an ever-increasing complexity.
“It is this culture which drives the development of new technologies and new methods in pipe rehabilitation,” Mr Weaver said.
This achievement is another example of how an Australian company and Australian technology can make a significant contribution to the advancement of the trenchless industry on the world stage.
In accepting the award Interflow’s Managing Director Geoff Weaver thanked the key contributors to this success, including:
- Sydney Water, for providing Interflow with the opportunity by recognising the value of Trenchless Technology in the management of their assets
- Sekisui Rib Loc for almost twenty years of partnering with Interflow to constantly push the boundaries of spiral wound technology, and
- The team at Interflow for working together to ensure that every project undertaken by Interflow adds to its reputation for honesty, reliability, competence and value for money.
