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Trenchless technology


InsituMain proves main answer


Open trenching was not an option when a fire main needed replacing. The solution came in the shape of the InsituMain CIPP system.


THE INSITUMAIN system is a cured-in-place pipe (CIPP) technology specifically engineered for pressure pipelines.


Building on


40 years of experience and more than 300km of trenchless pressure pipeline installations, InsituMain system,


an innovative


solution for fully structural pressure pipe renewal. One area of pressure pipe rehabilitation that is of increasing interest appears to be that of fire mains. An example of such an application that Insituform undertook


recently and


successfully completed is a pressure pipe rehabilitation project on a fire main at the Esso Fawley Oil Refinery. The fire main system totals 35.4km in length and has some 12,000 operational valves in service.


Comprising a deteriorated old cast iron pipe, the fire main was in need of replacement and the client was seeking an alternative structural solution other than


traditional trenching.


Renewal After


considering various


options it was decided to undertake the rehabilitation of a 240mm diameter, 250m long section of the fire main using the InsituMain system.


Given the circumstances


and operating requirements of the Fawley fire main and after careful calculation of the Fawley fire main system, ITL recommended a liner thickness of just 6mm. For the Fawley work, the liner was installed using a water-driven gravity pressure head with the inversion and curing operations taking place as described above.


In addition to the Fawley project, other ITL projects have included the rehabilitation


of pressure


pipelines for another large oil refinery, rising mains for Severn Trent Water and Southern Water and


InsituMain can negotiate bends up to 45° and offers a long-term internal pressure rating of between 3bar and 10bar depending on the diameter. The system is capable of withstanding a maximum surge pressure of -0.9bar.


Installation lengths of more than 600m have been achieved on straight pipe lengths and installation around multiple bends is possible depending on the bend type. The duration to install and cure an InsituMain liner depends on the liner thickness, diameter and length.


not


Typically it is 12+ hours, including


unforeseen circumstances.


The system is also designed with the ability to bridge over corrosion holes, pinholes and joint gaps in


14 | WET News | December 2013 open


pressure pipe rehabilitation for the Sheffield Forge Masters steel plant. The


InsituMain system


is suitable for the renewal of rising mains and both distribution


and trunk


water mains ranging in diameter from 150mm up to 1500mm. DWI certification is currently being sought for the system.


Should a


circumstance arise where height, space or access is limited, other inversion systems are available that enable the inversion pressure to be applied without the need for a tower structure.


the host pipe on a long-term basis. The


solution,


InsituMain system not only provides a structural


it


also offers the additional benefits of protecting the host pipe from internal corrosion, sediment build- up or further tuberculation as well as improving flow characteristics due to reduced surface friction provided by its polypropylene inner surface. With these design characteristics, the InsituMain system can be considered equivalent to replacing the existing infrastructure with a new pipe without the disruption and cost of traditional dig and replace methods.


Host pipe


The InsituMain system is a composite material of polyester fibre, fibreglass and a new specially formulated


resin system


which has been developed by Insituform and resin suppliers specifically for the clean water market. Liner thickness, starting with a minimum of 5mm up to 45mm, depends on the design for the internal pressure and external forces when there is no internal pressure in the pipe.


As the process does not rely on any bond with the existing host pipe, it is suitable for rehabilitation in all types of host pipes including cast iron, ductile iron, steel, asbestos cement, reinforced concrete pipe and


thermoplastic. Standard The


InsituMain system has also been certified as complying with the requirements of ANSI/NSF


61


and UK and European requirements.


Engineered to restore existing


pipelines, and the


InsituMain system is one of few CIPP designs that can withstand both internal pressure loadings,


whilst


external also


eliminating leakage and corrosion associated with


the deteriorated host pipe. In support of the increasing demand for pressure pipe rehabilitation


using CIPP


liners in the area of drinking water supply, Insituform has also developed a new resin system specifically for potable water pipeline applications, which is undergoing DWI approval in the UK.


With the InsituMain system, the first step is to provide access to the existing host pipe by setting up a bypass / over pumping system and excavating pits. Access pits are required at all end termination points, branches, valves and other ‘in-line’ fittings. Pit size will depend on the pipe diameter but generally a 3m x 2m excavation is required. It is common practice to locate inversion access pits at these locations to minimise digging.


The internal diameter of the host pipe is then confirmed and a CCTV survey undertaken to ascertain the pipe condition and the extent to which cleaning of the host pipe is required.


The existing host pipe is then cleaned using the most appropriate any fittings.


method and


New flanged spools with 0.5m length pipe pieces and locking rings are fitted at the inversion and final termination points as well as on either side of all valves and branches prior to lining.


Before the


of the liner, the site crew conducts


another


installation pre-


lining CCTV survey of the length of pipe to be relined to ensure the pipe is clean and clear of any potential obstructions to the passage of the liner and is suitable for lining. The


InsituMain system is installed using a water generated, gravity pressure head. This pressure head is produced by suspending the


liner from a working platform or inversion tower.


The InsituMain liner emerges at the reception pit after inversion into the host fire main pipe on the Fawley project


The tower structure used to provide the water pressure head to complete the inversion of the liner into the host pipe at Fawley


The InsituMain liner emerges at the reception pit after inversion into the host fire main pipe on the Fawley project


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