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Innovative composite materials repair ageing pipes

Image shows damaged pipe

Infrastructure owners and managers now have the option of composite cured-in-place pipe repair technology (CIPP) which does not require costly and disruptive excavation.

Since 1910, more than 300,000km of steel-reinforced concrete pipes have been laid in Australia and New Zealand in drainage, road culvert, sewer and pressure pipe applications. Cured-in-place

photo demonstrates the innovative pipe repair process using composite materials

A resin-saturated liner is pulled into a damaged pipe through an upstream access point. Source: allnex

pipe (CIPP) technology offers a cost effective and non-destructive repair solution for the relining of old and damaged water, sewer, gas or chemical pipelines.
Concrete pipes of today have a long history of excellent performance as a durable product for storm water drainage and sewer applications. While continuous research and development has enabled increased reliability, at some point concrete pipes, especially old ones, will fail and need repair. Digging up old pipelines can be destructive, expensive and time consuming.

A more cost effective solution is offered by CIPP, a cured-in-place pipe system using FRP composites to repair leaking or structurally unsound pipelines. It is a jointless, seamless, pipe-within-a-pipe that can effectively reduce infiltration and leaks without digging. The first CIPP technology was applied in London in 1971 and later commercialised by Insituform Technologies in 1977. The technology entered the public domain in 1994.

As a trenchless technology, CIPP does not require excavation. The liner is often installed through a manhole or other existing access point. A resin-saturated felt tube, made of polyester, fibreglass cloth or other materials suitable for resin impregnation, is inverted or pulled into a damaged pipe through an upstream access point. The liner can be inverted using water or air pressure. The resin, usually polyester, is then cured by hot water, UV light or steam to form a tight-fitting, jointless and corrosion-resistant replacement pipe. In sewer lines, lateral connections can also be restored without excavation via a remote controlled device that drills a hole in the liner at the point of the lateral connection.

Although CIPP offers a great solution, it also has some limitations. Except for very common sizes, liners are not usually stocked and must be made specifically for each project. Curing may take from one hour to 30 hours depending on pipe diameter and curing system, and must be carefully monitored, inspected and tested. Obstructions in the existing pipeline such as protruding laterals must be removed prior to installation. While CIPP can repair a pipe with bends, special design considerations must be taken into account to prevent wrinkling and stretching. The more flexible the liner, the more care needs to be taken during inversion to ensure the liner remains on the correct alignment. Testing of CIPP installations is required to confirm that the materials used comply with the site and engineering requirements.

In its Botany, NSW laboratory, allnex has developed a resin specifically designed for CIPP applications. Polyplex 916 has been formulated to facilitate high cross link density in the cured composite liner. This improves overall chemical and hydrolysis resistance and can result in faster cure rates and shorter curing cycles, dependent on sufficient heat input during the CIPP fabrication process.
“In comparison to other conventional unsaturated polyester resins typically used in CIPP applications, this resin offers various technical and performance advantages, including excellent tensile and flexural properties, high heat distortion temperature and high tensile elongation. This combination of properties typically results in increased toughness and durability in the cured composite liner.” Dean Voice, Technical Service & Business Development Manager at allnex.

To demonstrate suitability for CIPP applications, Flexural Creep modulus properties of CIPP composite liners made using Polyplex 916 were independently evaluated and qualified to meet CIPP industry requirements according to ASTM D2990-09.

Infrastructure owners and managers now have the option of composite cured-in-place pipe repair technology (CIPP) which does not require costly and disruptive excavation.
More information: Contact allnex T: 1800 789 607