Taking the base idea from the process developed in Canada, Nu Flow in Australia have carried out considerable work on adaptation of the system to suit the wide range of Australian conditions. The process involves the insertion of custom made resin impregnated felt liner into cleaned pipes to effectively seal off any damage, broken joints or even to replace crushed or non existent original pipe.

During this research program, the problem of relining of lateral connections was brought to the fore when looking at several jobs that are sometimes used as part of the research development process.

After considering several approaches to achieve a better quality repair on these connections, the company carried out a number of test relines to analyse the time and cost effectiveness of the various methods proposed.

There are a variety of names applied to these junctions such as lateral connections, junctions, house service lines (HSLs) or house service connections (HSCs) but whatever its name, the point where two pipes intersect is a common weak spot in any drainage system.

In a mainline rehabilitation project the junctions are lined over and then re-instated using a robotic cutter, thereby creating a weak point in the continuous mainline liner. In domestic drains, an inspection opening is often built into a junction for cleaning purpose and where this connects, it can be a weak spot for roots to enter.

Junctions are also subject to stress fracture from varying ground pressures on the main and branch line. Junctions can be damaged by external forces such as excavators.

In order to have a complete and secure lining system there is a need to be able to repair and seal every part of a drainage network, from straight pipes of varying diameters to bends, trap reducers and of course, junctions.

It was not immediately obvious that there was an easy solution to this problem. However, Nu Flow pipelines, through an extensive program of research and development based at their Queensland facility became committed to working out a solution so as to strengthen this companies commitment to being the most versatile relining system available in Australia.

As a result of many months of trials with a diligent process of analysis being applied to each innovation, it soon became clear that it was possible to build a single unit repair liner.

Several applications were also looked at as it was important to be able to use variable lengths up the branch line and/or the mainline.

Another factor was that the system perfected had to be a full wrap on the mainline, not simply a top hat section.

The installation of the Nu Flow LCL is a little more involved than the installation of a conventional straight liner., and needs a higher skill level. This system relies on stringing two pull lines upstream, one in the mainline, the other to go up the branch.

The pre-formed T- or Y-shaped resin impregnated lining felt is then secured into position using the pull lines. Once in place, the liner is inflated and bonds to the existing pipe walls. The application can also be used on vertical shafts, using a calculated pull system.

Whilst other sizes have been experimented with, the majority of uses for the newly developed LCL are in 150 mm to 100 mm junctions, but 100 x 100 and 150 x 150 have also been lined.

This is another case of Australians showing their acclaimed innovative ideas and using a diligent and dedicated work and research program to achieve a beneficial result.

Flow-Thru system

Whilst working on the development of the lateral connection relining process, Nu Flow Technologies have also developed a Flow-Thru system especially for mainline application, where the flow is constant and cannot be interrupted.

These mostly apply to drains of 150 mm and upwards, as most 100 mm pipe systems have low flows and can be stopped during cure time needed to effectively reline the damaged pipe.

The system consists of two accurately machined alloy end bullets with an open centre core that allows flow through during the relining process. These ends are joined by a high pressure suction hose, the diameter and length of which is adjusted to suit the pipe to be repaired. A 50 mm hose is used for 150 mm drains and lengths up to 10 metres can be managed. The normal relining materials together with the resin impregnated felt are used to complete the Nu Flow developed package.

In the process of perfecting this system, Nu Flow has carried out extensive R&D in live sewers with excellent results.

If necessary, flow through systems of an overall length of 2 metres were used to apply 1.5 metre patches in both 150 mm and 225 mm sewers. An example was demonstrated with a 225 mm sewer that had a pumped flow from an upstream collection well of 5,000 litres at 20 minute intervals. The Australian developed and perfected ‘Flow-Thru’ system performed to highly accepted standards even at inflation pressures as low as 8 psi. During the interesting demonstration the system was installed through a variety of manholes, including some 6 metres deep. No operator manhole entry was necessary for either insertion or retrieval.

This patented innovation for the Nu Flow relining process to be called Flow-Thru will see other applications such as installing multiple patches in the one line and as the mainline bladder in other continuing Australian relining developments.