Since its introduction, the ‘fold and formed’ system has been in continual use. Fold and formed is the generic name given to the range of liners that are deliberately deformed prior to insertion and then reverted to their original shape once in position.

The technique involves folding the liner into a ‘U’ or ‘C’ shape prior to insertion, and then using heat and/or pressure to form it back to a circular shape in intimate contact with the host pipe.

The process is available in polyethylene and PVC, although for sewer main applications the use of polyethylene material is now limited, mainly because of its inferior strength and thermal expansion properties compared to PVC.

In the case of the Ex-method, the liner is produced in Australia by Vinidex Pty Ltd as a PVC pipe which is coiled straight from the extruder onto a spool in a flattened state. The spool is then transported to site where it is heated by steam to soften the Ex material so that it can then be easily and quickly winched into the sewer from one access point to the next.

Steam circulation is continued for a short time to ensure the entire length is completely flexible and then the internal pressure is increased in a controlled manner until the reversion process is complete. The line is then cooled under pressure, and finally the ends are trimmed to complete the installation. Ex-method is offered in 150, 225 and 300 mm diameters, and because of the short installation period involved it is not uncommon to finish three linings in a single day.

PVC is the material of choice for new sewer pipes and the Ex-method simply provides the same strength and durability of a new PVC pipe without the need for excavation.

Sydney Water Corporation operates and maintains sewer lines throughout the Sydney area. In previous years they have let annual contracts for sewer rehabilitation works from selective tenders received from a panel of prequalified tenderers.

Deviating from the annual sewer rehabilitation contracts, Sydney Water invited tenders for the SRP 2006-09 (Sewer Rehabilitation Program 2006-09) from the selective tenderers registered in the prequalified panel, to procure delivery of the rehabilitation works over a three year period with an option to extend the contract(s) for a further year.

The major activities involved in this contract are the design, manufacture, supply, installation and testing of structural liners for approximately 242 km of sewer pipes of 150 – 750 mm diameter over the three year period at different locations within Sydney Harbour, Georges River and the Hawkesbury/Nepean and Illawarra Wastewater areas.

Kembla Watertech is one of two companies to be awarded a term contract under the SRP 2006-09.

The major portion of the length of sewer to be rehabilitated is in the 150 – 300 mm range where Ex provides the most cost effective solid wall solution.

Kembla has been working on Package 1 of the SRP 2006-09 since November 2006 and already, some 23 km of Ex lining has been installed. This rate is programmed to continue and so in the next few months the total length of Ex installed throughout Australia will pass the 1,000 km mark.

This is an important milestone for a No-Dig pipeline rehabilitation system that was specifically developed to suit Australian conditions and has now been used successfully from Cairns to Perth and most places in between.