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Insituform Continues Product Expansion with Leak-Tight Lining Technology
Over the past 30 years Insituform Technologies has developed a reputation for the installation of CIPP pipe linings that are inverted using water. But alongside this world-renowned system the company has also been involved with the development and introduction of a variety of other innovative pipeline rehabilitation systems.
 Normal Cured-In-Place-Pipe lining systems have the potential that, once cured, the liner may develop an annulus between the host pipe wall and the outer skin of the lining material. Whilst this slight shrinkage of the liner is not normally an issue in most sewer rehabilitation works there are circumstances in which it might be desirable that the resulting annulus is eliminated from the rehabilitated pipe. Situations such as sewers with high infiltration rates due to external ground water pressures or where lateral connections cause the mainline to be opened, beneath the water table to take the connection are such cases.
Many systems have tried to overcome this potential problem in a variety of different ways, but now Insituform Technologies Ltd (ITL) of Ossett, West Yorkshire has launched a new lining product that guarantees a tight fit, no annulus lining process.
Known as the ‘Leak Tight’ liner system, the new product utilises an established epoxy resin system, developed by a leading, world-renowned specialist resin supplier, as the basis of the lining process. The resin used effectively reduces liner shrinkage to nil during the curing process when used in conjunction with Insituform’s standard non-woven fabric liner tube. The liner tubes, depending on the circumstance of the lining operation, the curing process used and the final product requirements, are available with either polypropylene, polyurethane or polyethylene inner coatings.
 In August 2006, in order to fully establish the ‘Leak Tight’ claims of the product and the effectiveness of its installation, ITL undertook infiltration testing of the liner. The installation and infiltration testing of the lining was witnessed by WRc as part of an ongoing, 18 month long test programme for Thames Water that has been looking at various lining systems and their infiltration characteristics post lining and curing.
Using a test rig, designed by Don Ridgers of Thames Water, sample linings are installed and cured whilst a 3 m head of water pressure is applied to the test rig using simulated leaking defective joints and a lateral connection. Once the liner is cured in the ‘pipeline’ this test pressure is increased to a 5 m head of water. Any leakage between the host pipe and the liner is then measured.
On the ITL tests, two lining runs were completed. The first comprised the installation of a test liner using water inversion and hot water cure techniques and the second utilised compressed air inversion and steam curing, a technique recently added to the ITL liner installation portfolio.
The results of the tests showed that, in both cases, the liner could be installed with no leakage between the host pipe and the liner. That is to say there was no percolation of infiltration water along the liner/host pipe interface bond, proving the cured liner produced the close fit lining claimed by ITL’s new Leak Tight liner product.
LEAK TIGHT LINING
 The new Leak Tight lining product is currently available in a range of diameters from
100 mm upwards. It can be installed over lengths of up to 200 m. Further advantages for the
Leak Tight lining system are that it is odour free during installation and does not produce styrene or other volatile solvents on application. A further advantage of the steam cure option is that linings of up to 375 mm diameter can be installed and cured in as little as 3 hours under the right conditions.
A representative of the resin supplier said: “We have been very happy to work with ITL on the new steam cure lining process. Our engineers have worked hard to specially formulate the resin used in the system to work with the steam curing process. This ensures that the final lining product meets with all current industry requirements and performs to the levels expected in the modern wastewater utility sector. We also had representatives on site during the Thames Water/WRc test runs and were extremely happy with the results obtained.”
 For WRc, Kevin Adams said: “The infiltration test has been designed as an arduous examination of a lining system by the wastewater industry itself and it has been independently witnessed by WRc. The test in some instances has proved that water will track between the host pipe and lining where there is a path left by the lining installation process, thereby only moving the point of infiltration rather than stopping it. The test is a quantitative assessment of a lining’s ability to stop or reduce infiltration to the levels currently required by the water industry. The success of a lining system in this test will therefore give contractors proof of the performance being asked for by the asset owners. Insituform’s Leak Tight tests, for both the hot water and stream cure versions, showed no measurable infiltration from between the lining and the host pipe, showing that the lining had successfully bonded to the host pipe.”
WRc witnessed the ITL installation and infiltration testing and has issued a letter to ITL detailing the system materials and processes and confirming the success of both curing methods for the lining.
Commenting on the success of the new lining system for ITL, John Beech, Business Development Manager said: “Thames Water has utilised and refined the test procedure used on our Leak Tight liners for some 18 months now, so we know that it is very rigorous. In reality most sewer pipelines do not operate in ground water of 5 m static pressure head, so a test such as this really does show how effective our liners are once installed. We are also delighted that our association with our new resin supplier now allows us to offer an even greater range of lining products, with application to a much broader range of challenging ground conditions, to our existing and potential customer base.”
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