Pipe Liner Installed in Record Time

When rehabilitating mixed water channels in the Rethmar district of Sehnde in Lower Saxony, it was primarily all about speed. The damaged pipelines lay along the busy B 65 motorway, the town’s main road.

In an open construction method, this building measure would have resulted in months of blockages and thus considerable traffic obstructions. The Sehnde Municipal Utilities issued an invitation to tender for rehabilitation using the trenchless in-liner procedure. The order included the renewal of 911 m of mixed water channel in the dimensions of DN 250 to DN 1,200. The contract was awarded to Rohrsanierung Jensen from Bordesholm, which was able to demonstrate in its references numerous successful rehabilitation projects, especially with pipe liners with large dimensions. In May 2012, the channel was rehabilitated in 10 sections, under the direction of Dipl. Ing. Andreas Josef.

The biggest challenge of the project was formed by one section measuring 205 m long and in the dimension of a DN 1,200 circular profile. The partial blockage of the motorway required for the building measure should be reduced to a minimum. This long section was rehabilitated in a single work step. Due to the damage, the structural engineers calculated a required composite wall thickness without wear resistant layer of 12.1 mm for the GFRP “Alphaliner” pipe liner from RELINEEUROPE that was being used here. In order to install a pipe liner with this wall thickness within a reasonable time, to date only the use of so-called “pipe liners with combination curing,” which work with combined UV light curing and thermal curing, came into the question. As in the case of pure thermal curing, the disadvantage of this technology lies within the time-consuming logistical process. In order to prevent premature curing of the resin, the liner material must be transported and stored in cool containers. On the construction site, too, a considerable amount of additional work is required compared with pure UV light curing.

Stefan Jensen, managing director of the rehabilitation company, decided for this project to install the “Alphaliner1500” type GFRP pipe liner that was newly developed by liner manufacturer RELINEEUROPE. This pipe liner is characterized by a further developed, especially high level of transparency of the glass resin complex. In combination with a UV-curing technology coordinated to this liner type, Alphaliner1500 pipe liners with wall thicknesses measuring more than 10 mm can be quickly and completely cured using pure light curing.

On May 2, the 205-m long liner was delivered to the construction site on the B65 in Sehnde at 10 a.m. The transport case, which measured 6 m long and 2.5 m in length and width, came to the weight of almost 20 tonnes. A heavy-duty crane was therefore on hand to unload the liner from the lorry to the downcast manhole. Four hours later, the pipe liner was inserted into the channel on a sliding foil with the help of a conveyor belt, and the packers were positioned on both ends of the liner.

“For the curing process, we used the light source that RELINEEUROPE developed especially for rehabilitating large profiles and has a curing performance of 12 x 1,000 watts,” reports Stefan Jensen. The entrepreneur invested in this high-performance curing technology back in 2011. He explains that the technology has already proven itself on many construction sites when it comes to quickly curing liners with large wall thicknesses. Once the liner had been positioned and calibrated within one hour using compressed air, the installation team specialized in the installation of large liners was able to start the curing process at 3 p.m. With the powerful UV light source, a curing speed of around 50 cm per minute (up to 30 m/hour) was possible. The curing process was therefore completed at 10 p.m. after around seven hours. At 3 a.m., the specialists had completed all the rework, such as the milling out of the supply lines and the rehabilitation of the connections. In the morning, drivers came to their places of work in Sehnde without experiencing any traffic congestion. Claudia Pechtheiden–Meier of Sehnde Municipal Utilities, who monitored the project as the contracting body’s construction manager, was also satisfied. Jensen undercut the agreed time frame by 20 percent.

“This globally unique curing performance enables a considerably faster and more reliable installation of pipe liners, even when rehabilitating large cross sections with high static loads,” says up Jensen. For him, with the Alphaliner1500, the well-known benefits of light curing are “therefore transferrable on a one-to-one basis for the rehabilitation of large profiles.”

This article was submitted by RELINEEUROPE.
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