The project was in co-operation with Swietelsky Faber Kanalsanierung GmbH from Alzey and BRG Lux GmbH from Holzthum, and involved the installation of two DN 1,000 mm ADV 75 type glass fibre reinforced polymer (GFRP) pipe liners.

The concrete sewer was integrated step-by-step into the public mixed water grid. As the pipe was also used for stormwater during heavy rains, it often reached hydraulic capacity.

Inspection showed that the sewer was in urgent need of renovation. Fractures, corrosion, displaced and rooted sleeves, as well as a variety of connection pieces that were not professionally installed turned the connection drain into a high-priority project.

Planners from Dahlem, Schroeder & Associés sarl, who had been commissioned by the municipality, realised that the problem could not be solved with an open-cut renewal.

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Both end manholes were located within open street renewal projects and could be renovated during the project. The collection drain itself, which connected two parallel streets, traversed a residential area, with parts situated underneath buildings.

Curing with light

The light curing process means pipe liners are not thermally hardened with hot water following calibration. Instead, the exposure of the pipes, which are impregnated with photo reactive UP resin, are given a specifically defined dose of UV radiation which enables the curing reaction.

Brandenburger said “This technology version, which is historically younger compared to the thermal hardening processes, has increasingly gained ground in recent years.”

The company said that the advantages include a fast cure time and comparatively sparse, but highly mobile construction site equipment.

A remarkable achievement of the project was relining a large DN 1,000 mm, as for many years, such diameters were typically matched with hydraulic process. The two conduits measured from 70 up to 122 m; quite significant dimensions had to be covered lengthwise and with wall thickness of 9.1 mm. This meant the 122 m liner weighed no less than 5.3 tonnes.

The liner installation was winched into both conduits and carried out through shaft structures that were demolished and reconstructed during the simultaneous road construction project. During the installation, the liner was protected against damage by a plastic foil that was laid out in the base of the drain.

The glass fibre tube was sealed at both ends with insulating sealers and then locked in the sewer with compressed air. Afterwards, one of the pressure locks was opened for a few minutes in order to install the UV lamp train, which had previously been tested.

The liner tolerates the temporary decrease in pressure without collapsing within the sewer. Furthermore, prior to the actual curing process, the liner is restored to the set internal pressure. The lamp train checks that the installed liner is properly fitted to the old pipe along its entire length and that it does not show any deformations. While it is pulled to the opposite sewer, where the actual curing begins, a small camera in the front of the lamp train records the internal state of the liner prior to the curing – thus, potential irregularities can be detected and corrected in time.

In the Pétange collection drain, the lamp train cured the UV reactive UP resin in the liner with 12 x 400 watt light output, at a velocity of the lamp train of 15 cm per minute. There is a direct link between light output, reaction temperature of the liner and the velocity of the run through the sewer.

All of these parameters are precisely pre-defined according to the geometry and wall thickness of the liner. Their compliance is precisely measured and recorded during the hardening. This gapless and fully automated process is a central element of quality assurance in the Brandenburger liner procedure.

In the end, it also produced the desired result in Pétange – a cured and watertight liner with a wall thickness installation of 8.4 mm. It ensures that the mixed water collection drain at Pétange can reliably perform its crucial role for several more decades.