Pipes that have seen better days made as good as new
When pressure pipes are past their best the Thermopipe System - which can be installed quickly and under difficult conditions - can give a length of piping a new lease of life, with disruption and carbon footprint kept to a minimum.
The system is one of several lining products from Institiform Technologies.
It is a polyester-reinforced, polyethylene structural lining system that offers advantages for the rehabilitation of pressure mains. The liner system stops leakage by bridging and sealing holes and faulty joints, improves the quality of water, reduces carbon footprint, and, says Insituform, is a cost-effective way of extending the life of water-supply infrastructure systems with its 50-year design life. The system provides an independent structural lining with an internal pressure rating of 12 bar (16b for 100mm through 200mm diameter). It is available for installations in pipe diameter from 60-300mm.
According to the company, a major advantage of the system is that it offers the ability to rapidly install up to 300m (1,000 linear feet) in just a few hours, while being able to negotiate multiple bends in the host pipeline. This minimises the need to break down projects into individual straight installation lengths.
The 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 two main access pits required for an installation. Once winched into place, the liner system uses air pressure and steam - that is applied to the inside of the liner - to revert it to its round shape within the host pipe.
Once inflated and heated, the liner forms a close-fit within the host pipe, creating a joint-less, leak-free lining system able to carry the internal design pressure, independent of the structural strength of the host pipe.
The installation process is simple and most installations can be completed within eight hours.
The system carries recognised approvals including:
- Certification by NSF International as complying with the requirements of NSF/ANSI standard 61
- UK DWI Approval
- Manufactured under a Quality Management System approved to ISO 9000
The route of the 150mm diameter cast-iron pipe runs under the river bed for about 100m 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. Subsequent CCTV camera inspection revealed that it would be possible to effectively renovate the water main and affordably bring it back into service.
The main water feed across the Ness was maintained because there are four separate water mains that cross the river. 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 Thermopipe system.
Project manager Jim Rafferty explains: "Rather than replacing the pipe we were able to insert a new one inside it. 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."
At the time of year that the work was to be undertaken, Inverness is a very popular tourist destination in Scotland and the town's riverside is particularly popular. Scottish Water designed its programme of work in a way that would minimise disruption.
This was one of the operational reasons behind the choice of the system, as only a small working area was required on the riverbank. A minor lane closure was needed on the Ness Bank Church side for the project's duration.
There was, however, some minor disruption to water supplies in the area during the course of the work. Overall, the lining operation was completed without any problems - other than some minor disruption on the west side of the river.
In terms of the liner pull in, this operation took just 90 seconds to achieve over the 100m length.
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.
Over the coming three years, Scottish Water expects to invest £154M in the Highland Council area to maintain 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 HMP - the Holleran and Mouchel Parkman joint venture - and as part of the Southern Water K4 Rising Main Replacement Programme, ITL completed another installation using the system at Hildern Park School.
The pipeline serving the school had experienced a number of bursts 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 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, while offering a speedy installation.
The renovation work comprised two separate pipe-lining operations. The pipes in question were of asbestos cement construction and at 225mm diameter, over lengths of 310m. 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 worksite footprint considerably.
The advantage of using the 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. Commenting on the Thermopipe system, John Beech, business development manager for ITL, says: "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 community, while operating in limited space and to a limited timeframe, which in modern times makes it another very powerful part of ITL's portfolio."