Trenchless rehabilitation of drinking water networks

Installation of Nordipipe liner.

Installation of Nordipipe liner.

In the ever expanding urban areas of Asia, Australia and New Zealand, a reliable drinking water supply is of utmost importance, however, this often presents technical, economic and organisational challenges to water authorities, says Sekisui Ribloc.

With the number of people competing for limited water resources increasing, supply infrastructure must maintain effective and uninterrupted delivery. Persistent water losses from leaking pipes are unacceptable and relatively easy to eliminate using a CIPP (cured-in-place pipe) system. Modern trenchless rehabilitation technologies such as CIPP guarantee water-tight pipe systems and maximum utilisation of the available water quickly, economically and permanently. Furthermore, they reliably protect the conveyed water from external contamination.

The CIPP systems Nordipipe and Tubetex from Sekisui Pipe Rehabilitation (SPR) Asia Pacific have proven themselves in drinking water networks across the globe. Since the two systems were certified for use with drinking water in Australia and New Zealand in 2011, they have greatly contributed to sustainable water management in the Asia Pacific region.

Requirements of CIPP systems for potable water

CIPP systems for potable water pipe rehabilitation differ from non-pressure applications with respect to the liner composition and installation. The design of the installed liner needs to cater for both internal and external pressures and materials used must be approved and certified for contact with drinking water. The CIPP liner can function either as an internal pressure-resistant lining or as a statically self-supporting ‘pipe within the pipe’ based on a fully deteriorated design.

The right solution for every problem

One of the leading manufacturers of CIPP systems is Sekisui NordiTube, a subsidiary of the global SPR Group. Sekisui NordiTube produces two CIPP systems for pressure pipes which cater for highly diverse requirements and have been tried and tested in a broad spectrum of applications worldwide.

Tubetex is a semi-structural liner that has an internal pressure rating up to PN 32 for the rehabilitation of locally deteriorated gas and drinking water pipelines in diameters of 200 to 1,000 mm. Currently lengths of up to several hundred metres can be installed per installation. The basis of Tubetex is a seamlessly circular woven tube made of polyester yarn with a single-sided coating of polyethylene which forms the inside of the liner when installed. The high flexibility of the system allows installation in curves and bends. The liner, impregnated with a thermo-reactive epoxy resin developed by Sekisui NordiTube, is inverted by air pressure out of a mobile pressure drum into the open and previously cleaned pipeline. This method permits long installation lengths and ensures that the tube forms an intimate close fit with the host pipe. The liner is then ready for use after it has been cured, end sealed and reconnected to the distribution system.

The Nordipipe installation system is very similar, but differs considerably from Tubetex in terms of materials and properties of the finished liner. With diameters of 150 to 1,200 mm the range of uses of Nordipipe is slightly broader. The internal pressure resistance of this fully structural stand-alone system is dependent on diameter and allows applications in network systems PN 10 to PN 16. Nordipipe has also been installed in lengths of up to several hundred metres and is the ideal choice when the overall structural properties of pipelines are weakened but expected to withstand internal pressure and heavy external live loads.

Due to the tubular structure this system offers a good static loading factor and is self-supporting (equivalent to a new pipe). The liner owes these properties to the composition of individual components: a polyester needle felt tube which serves as the actual resin carrier is combined with at least one layer of fibreglass. It is this fibreglass layer that is largely responsible for the static qualities of the Nordipipe liner. Internally there is a polyethylene layer in contact with the potable water that also dramatically improves the hydraulic capabilities of the pipe. For large diameter liners with thick walls the typical drum and air inversion steam cure method is substituted with water column inversion where water and not air is used to invert and hot water and rather than steam is used to cure.

Nordipipe and Tubetex case studies

Both CIPP systems have been used successfully in the rehabilitation of a number of difficult pipelines.

In Hong Kong, the Nordipipe liner was used to rehabilitate a 600 m long potable water pipe. This pipe was rehabilitated in two weeks with minimal disturbance to traffic. The DN600 line was divided into three sections. Each section was then lined with Nordipipe and steam cured. The NSF 61 certified liner and resin was designed for internal pressure and all external loads.

Another example of the CIPP application was the rehabilitation of a century-old drinking water supply network in the old part of Montreal, Canada. Open trench renewal of the pipelines in the city was out of question due to the traffic density and the adverse effects it would have on businesses. With Nordipipe all these problems were solved. For example, a main intersection in downtown Montreal was relined with installations of up to 152 m without any obstruction of traffic. Since 2003 more than 28 km of drinking water pipelines in Montreal’s old town alone have been replaced by local contractor Aqua Rehab.

Official approval to AS/NZS Standard 4020:2005

The above examples illustrate the considerable problem-solving potential of the Nordipipe and Tubetex technologies and the key role they will play in the future maintenance of infrastructure in the Asia-Pacific region. This is particularly true when considering that in July 2011 the two systems received official certification to AS/NZS Standard 4020:2005 for use in the drinking water sector. The liners and their respective resin systems successfully passed testing in all six relevant categories.

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