Insituform Technologies Ltd. offers as part of its extensive pipe rehabilitation portfolio the Thermopipe® system, a polyester reinforced, polyethylene structural lining system that offers major advantages for the rehabilitation of pressure mains.
The system provides an independent structural lining with an internal pressure rating of 12 bar (16 bar for 100 mm through 200 mm diameter). It is available for installations in pipe diameter from 60 to 300 mm.
One of the major advantages of the system is that it offers the ability to rapidly install up to 300 m (1,000 linear feet) in just a few hours whilst being able to negotiate multiple bends in the host pipeline, so minimising the need to break down projects into individual straight installation lengths.
The Thermopipe® system is designed for the rehabilitation of distribution water mains and other pressure pipe systems such as sewer force mains, fire water mains and industrial pressure applications. It is supplied as a factory-folded 'C' shape liner, which is winched into the host pipe from a reel located at one of just two main access pits required for an installation. Once winched into place, the liner system utilises air pressure and steam which is applied to the inside of the liner to revert it to its fully round shape within the host pipe. Once inflated and heated, the liner forms a close-fit within the host pipe, creating a jointless, leak-free lining system able to carry the full pipe system internal design pressure, independent of the remaining structural strength of the host pipe. The installation process is simple and most installations can usually be completed within an 8 hour time period.
CROSSING THE NESS RIVER
In April 2007, Scottish Water undertook a renovation project in the town of Inverness designed to bring back into full service a 100 year old water main running under the River Ness.
The route of the 150 mm (6 in) diameter cast iron pipe runs under the river bed for a distance of about 100 m between the Ness Bank Church on the east side of the river and St Andrew's Cathedral on the west side. In 2005, the pipe was taken out of use when it became damaged by, what was believed to be, natural movement of the riverbed over previous decades. However, subsequent CCTV camera inspection revealed that it would be possible to effectively renovate the water main and bring it back into service with minimum expenditure.
The main water feed across the Ness River was maintained because there are four water separate mains that cross the River Ness at various points. The supply network can be adjusted so that different parts of Inverness can be fed from either Loch Ashie to the south or Glen Convinth to the west.
For the project, Scottish Water decided to use the tried and tested Thermopipe® system. Project manager Jim Rafferty explained: "Rather than replacing the pipe we were able to insert a new one inside it. Since taking the main out of service, we have still been able to supply the west side of Inverness but it made sense to bring it back into use if it were technically and economically feasible. It will provide yet another option for the already robust supply network and could help improve water pressure to 286 properties at peak times when households draw large volumes from the system."
At the time of year that the work was to be undertaken, Inverness is a very popular tourist centre in Scotland and the town's riverside is particularly popular. Scottish Water therefore designed its programme of work in a way that would minimise disruption not just to the visiting tourists but to the town as a whole. This was one of the operational reasons behind the choice of the Thermopipe® system as only a small working area was required on the riverbank on the Cathedral side and only a minor lane closure was needed on the Ness Bank Church side over the whole of the project duration.
There was, however, some minor disruption to water supplies in the area during the course of the work which took around four weeks to complete. Overall the lining operation was completed without any problems other than some minor disruption on the west side of the river where some new ductile iron pipe had to be laid.
In terms of the actual Thermopipe® liner pull in, this operation took just 90 seconds to achieve over the 100 m lining run length, with the folded liner being provided off a pipe coil. Overall the client was very pleased with how the lining operation was achieved and its ultimate result.
Looking to the future, Scottish Water is considering a further water main to cross the river and the Caledonian Canal, which will depend on Highland Council's chosen route to complete the Southern Distributor Road which could involve bridges or an aqueduct.
Over the coming three years Scottish Water expects to invest £154 million in the Highland Council area to maintain already high drinking water quality and sewage treatment, lay new pipelines and increase capacities to enable the growth of communities.
On another project, this time for client Southern Water, working through the water company's main contractor, Holleran Mouchel Parkman Joint Venture and as part of the Southern Water K4 Rising Main Replacement Programme, ITL completed another installation using the Thermopipe® system at Hildern Park School.
The pipeline serving the school had experienced a number of burst incidents over previous years and was in need of renovation or replacement. However, the location of the existing pipe and its routing beneath the school building meant that an open cut option was simply not viable, so a trenchless solution was needed. Also, because of the need to maintain flows through the renovated pipeline, any solution had to minimise any capacity losses. The solution also had to minimise the disruption to the location whilst offering a speedy installation. It was therefore decided to use the Thermopipe® system.
The renovation work comprised two separate pipe lining operations. The pipes in question were of asbestos cement construction and at 225 mm diameter, over lengths of 310 m. To minimise disruption to the operations of the school the work was scheduled to be completed during the summer holiday break.
In the end, the lining works proceeded without incident. Again the folded liner was pulled into the host from a pipe coil trailer, which helped to minimise the working site footprint considerably.
The advantage of using the Thermopipe® system in this case was that it achieved all the requirements of the project in terms of minimum capacity loss, time on site and ultimately longevity of the newly restored pipeline without any interruption to the running of the school.
John Beech, business development manager for ITL, said in respect of the Thermopipe® system: "These projects both show just how efficient and versatile the Thermopipe® system can be. This product enables our engineers to work with minimum disruption to the local community, whilst operating in limited space and to a limited timeframe, which in modern times makes it another very powerful part of ITL's portfolio."