SOC installs France's largest inliner to date

The June 2009 project comprised the rehabilitation of an overall 481 metres of sewer in the municipality of Montaigu, south of Nantes. Rehabilitation was necessary due to several breaches in a rainwater collection drain carrying surface water from a main road and an industrial zone. The factors that decided the client, the Conseil Général de Vendée that manages public investment, in favour of a trenchless method were that the sewer was close to a relatively new and busy road, ran up to 14 metres below ground, and crossed under a former landfill. This measure also was an opportunity for the contractor to demonstrate that rehabilitation with light-curing liners is possible even for large diameters.

Liner was delivered to the construction site ready for installation

For SOC, the installation of a DN 1000 diameter was a first. The largest liner that the Nantes-based company had installed so far had a diameter of DN 600. The largest single item in the Montaigu project was the rehabilitation of a rainwater collection drain using a 156-metre section of liner with a wall thickness of 8.4 millimetres and a weight of eight tonnes – the biggest inliner ever installed in France. Additional items were the rehabilitation of 101 metres of a parallel sewer, and other sections measuring 136 and 88 metres, respectively. The liner used was an E-CR (ADV 120) glass-fibre reinforced plastic liner (GFRP) by Brandenburger. Prior to delivery to the construction site, the liner had been manufactured with ready-to-install dimensions and pre-impregnated with polyester resin at the Brandenburger factory in Landau, Germany.

Industry follows project with great interest

"A DN 1000 liner is quite an unusual thing", says David Veltz of Brandenburger, who was is charge of on-site technical support for the partner company. While traditionally water-curing technology used to get the lion's share, the French market has seen a development towards large GFRP inliners in recent times. "The benefits are less wall thickness and better stability. However, the technology first had to establish itself in the market." With the French rehabilitation industry watching the project with great interest, the installation was an important reference project for SOC.

Sewer outlets in the riverbed – a platform was required

As the outlets of the two parallel lines were both in a riverbed, a platform needed to be built. This not only provided safe working conditions; the platform and the route of the sewer also allowed the liner to be pulled into the sewer horizontally with a conveyor belt directly from the lorry – a clear advantage over installation through a shaft. In spite of these advantages, pulling eight tons of liner into the sewer was quite a challenge. "The main problem was tensile load", explains David Veltz. It was unusually large: The liner was pulled into the sewer using a winch situated above a shaft at the roadside end of the sewer, against the direction of flow and up a one-percent slope. However, the team came up with a simple and effective trick to solve the problem: 30 litres of vegetable oil were used to lubricate the liner, so that it could be drawn at a tensile load of only 2.2 tons. In comparable applications, the material had been subjected to up to 40 kilonewtons (kN) of force – equivalent to more than 4 tons. The preliner also made the pulling easier and protected the bottom of the heavy liner. "The installation of such a large liner is really difficult", comments Fabrice Merceron of SOC, who was in charge of the project. He says that the handling required a great deal of power, but the Brandenburger conveyor belt made it a lot easier. In spite of the fact that this was the first installation of a DN 1000 liner, no special preparations were necessary. "The liner is thicker and heavier, but aside from that, the process steps are the same as for any other inliner installation."

156 metres were cured in only six hours

After the liner had been pulled in, it was sealed with packers and pressurised with air for a tight form-fit with the wall of the old pipe. The entire section was cured in only six hours at a speed of 42 cm/min with a movable chain of nine UV lamps at 1000 Watts each that had been placed inside the liner. Brandenburger technology enabled the team to monitor the entire procedure on a screen and to document the curing process seamlessly with data on speed, pressure, temperature and the ignition of individual light sources.

The entire project was completed smoothly within two weeks. Considering the great success of this pilot project, an increase in the use of large-diameter GFRP inliners in France is to be expected. test

Contact and further Information

Brandenburger Liner GmbH & Co. KG
Taubensuhlstraße 6
D-76829 Landau / Pfalz
Telephone +49 6341 5104 0
Telefax +49 6341 5104 155
info@brandenburger.de

SOC
Avenue de Pagnot – BP 51
33166 SAINT-MEDARD-EN-JALLES
Telephone : 05 56 70 10 80
Telefax : 05 56 70 10 99
E.mail: soc@soc.fr
www.soc.fr

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