Germany’s Largest UV-CIPP Liner Installed in Karlsruhe

Administration for Civil Engineering contracts Jeschke Umwelttechnik to rehabilitate a 220-meter long (722 feet) section of the main collector Landgraben with DN 1750 – Alphaliner1800H produced by RELINEEUROPE fulfills all requirements

The Landgraben, 9.5 kilometers (5.9 miles) long, spans Karlsruhe from east to northwest and is older than the city itself. It was built in the 16th century as a drainage channel, connecting Durlach, which is nowadays a neighborhood of Karlsruhe, with the river Rhine. From 1878 to 1895 Karlsruhe worked on the "correction" of the then still open-faced trench, converting it into a main sewer canal, which it still is today. Its dimensions came close to those usually only found in metropolitan cities such as Paris back then, as this main collector not only had to accommodate both waste- and rainwater, but also drain the wetlands located to the east of the town. At its widest point, the canal is an impressive 5.2 meters (17 feet) high and 3.6 meters (12 feet) wide. It was built using red sandstone and clay bricks and is nowadays listed as an architectural monument.

Germany’s Largest UV-CIPP Liner Installed in Karlsruhe - Members of the crew inside of the cured Alphaliner DN 1750
Germany’s Largest UV-CIPP Liner Installed in Karlsruhe - Members of the crew inside of the cured Alphaliner DN 1750

Hydraulic Properties of the Main Collector Must Remain Intact

One of the key specifications for these rehabilitation measures was that the hydraulic properties of the Landgraben must remain unchanged. Zinn and Schäfer explained that several different rehabilitation approaches, such as e.g. short pipe lining, had all been considered and then rejected, because they would have narrowed down the cross section of the canal far too much. Even open construction had been taken into consideration. For this option, the long construction period and the high costs ended up being the main criteria for exclusion. This approach would have required the installation of "a bypass" to permanently reroute the flow. "During heavy rains and storms, large quantities of water come through here. During such periods, we need the full capacity of this canal with its entire cross section of DN 1750," the civil engineering experts explained. Ultimately, this was the reason why the Department for Municipal Water Treatment decided to take a second, closer look at UV-CIPP lining: "Since it has now become possible to use UV-curing for dimensions for which this was once inconceivable." Due to the short construction times required for this method, it was possible to work with a temporary, aboveground bypass for a limited period of time.

Up until now, in Germany, only pipes with a dimension of up to DN 1600 had been successfully rehabilitated using UV-CIPP liners. "Specialized expertise and the appropriate equipment to install larger dimensions can only be provided by very few professional companies," states a notice published by the Administration for Civil Engineering. For this reason, the rehabilitation job was tendered as "restricted according to VOB/A". The bid was won by company Jeschke Umwelttechnik from Stutensee, near Karlsruhe, who had already completed several rehabilitation projects for the municipal water treatment authorities in Karlsruhe over the past years. They used the Alphaliner1800H, made by RELINEEUROPE, which is DIBt certified and one of the leading liners in the world, thanks to its outstanding mechanical properties. The liner is graded in the highest material category, Group 25, according to DWA-M 144-3. Due to its excellent mechanical resilience, this liner can be used for projects with very high structural demands and large wall thicknesses. Its laminate can be cured using nothing but UV-light, if suitable high-performance UV-curing equipment is employed.

UV-CIPP Liner Rehabilitation with XXL Dimensions

In 2019, Thomas Boos, who is now in charge of running Jeschke Umwelttechnik's business, planned the largest rehabilitation project in the company's history, in cooperation with the - then still - managing director and founder of the company, Stephan Jeschke. "Since 2017, RELINEEUROPE has been supplying its Alphaliners, ranging from diameters larger than DN 1300 to DN 1800, all around the globe. Based on this experience, we were confident we could handle such large dimensions, too," said Boos. "We were very pleased that, as experts for large profile rehabilitation with GRP liners and UV-equipment, we were now also able to assist Jeschke Umwelttechnik, who have been our customers for many years, in making such a large-scale project possible," added Philipp Martin, who heads RELINEEUROPE's sales in Europe. Even though this rehabilitation method and technology has its roots in Germany, people here are still reluctant to use it for very large profiles. In France and Eastern Europe, on the other hand, these large dimensions are already very much 'business as usual'. "The fact that the, so far, largest Alphaliner ever to have been installed in Germany will be located right in front of our own doorstep, makes us even happier," said Martin. Once the contract had been awarded, every single detail of the project was planned in close cooperation. The installation was scheduled for the third week of July 2020.

Managing Director Thomas Boos explained: "When rehabilitating DN 1750 using a UV-CIPP liner, everything has to have XXL dimensions." The liner for the Landgraben project needed the capacity to support huge loads. The structural calculations showed that the job required an Alphaliner1800H with a composite wall thickness of 17.0 mm, specifically designed for such large profiles. "Using RELINEEUROPE's REE4000 UV-curing equipment with its powerful UV-core and a total output of 24.000 watts, such a wall thickness can still be cured using only UV light, without the need to add peroxide and maintaining the associated cold chain," described Martin, highlighting the advantages of this technology. Jeschke Umwelttechnik had already invested in the most modern curing technology and their new REE4000 had been delivered to the company in May. Since then, they had already used it to rehabilitate several large profiles.

RELINEEUROPE produced the two Alphaliner, each with a length of 110 meters (361 feet), a week before they were to be installed. The two shipping crates destined for the project in Karlsruhe weighed around 25 tons each. An extra-wide heavy transport truck took the liners to Karlsruhe on the evening before installation. At the job site, a 120-ton crane was waiting and ready to maneuver the heavy boxes along a path of about 30 meters (100 feet), right to the installation pit which was located alongside the road.

At the job site, the civil engineering office Hartlieb from Bruchsal, also near Karlsruhe, had already prepared the large excavation pit and secured it with sheet pile walls, making certain it could withstand even the heaviest storms. At the installation pit, the shaft dropped about 5 meters (16 feet) deep. At its exit point, the excavation pit was still almost two meters (6.6 feet) deep. At both ends, a specialized company had already cut away the approximately 30-centimeter thick (1 foot) cement vault, which before had covered the Landgraben canal. Retaining the flow played a key role. During the rehabilitation job, wastewater was rerouted via a 230-meter long (755-feet) pipe bridge with a redundant layout and DN 400 HDPE pressure pipes. The pumps with a displacement of 400 liters/sec (105 gallons/sec) were also designed redundantly.

„Once the Installation of the Liner has Started, You Have to Keep it Moving Because of its Weight"

„As is always the case with large profile rehabilitation jobs, we once again took a holistic approach," Philipp Martin described the installation strategy. The liner manufacturer had been involved in the planning of the project right from the very beginning. All components employed at the job site were specifically selected to enhance each other's performance and make the job as efficient as possible. To pull the liner into the pipe, the newest heavy-duty conveyor belt with an automatic folding device, specifically designed for large profiles, was used. Foldable, three-piece packers as well as the equipment to firmly fix them in place, which is necessary to secure them against blow-out due to extremely high pressures inside the liner, were also supplied by RELINEEUROPE. On site, three application engineers supported Jeschke Umwelttechnik's installation crew during installation: Silvio Weiss, Jeschke's most veteran site manager, supervised the job. RELINEEUROPE's Mario Saalow orchestrated the installation process.

„Once you have started the process of installing the liner, you have to keep it moving because of its weight," Saalow outlined one of the risks which needed to be avoided. A winch with a tractive power of 10 tons, of which about 4 tons were effectively needed, was installed. The pulleys were fixed to the wall of the canal with extra-long nails. The largest slide protection foil available in the market, with a width of three meters (10 feet), was drawn into the pipe.

Curing 17 Millimeters Wall Thickness with 24.000 Watts of UV-Power at 0.27 Meters (0.89 Feet) per Minute

Once everything had been properly prepared, the liner pulling head was shaped using joint forces. Afterwards, it was lowered into the pit with the help of an excavator. At both ends of the pipe, the gang installed large dimension packers and secured them firmly in place using special equipment. It goes without mentioning that the packers were secured using special ratchet straps specifically designed to withstand such immense forces. The compressor used during calibration had the size of a minibus van. Combining two radial compressors, the liner was inflated from both ends until it reached an interior pressure of 200 millibar (2.9 psi) and lay flush against the walls of the host pipe. Now, curing could begin.

The REE4000 UV-curing system with its steplessly extendable, electricity-powered UV core and a power output of 6 x 4,000W, was specifically designed to cure even the largest liner dimensions. According to Martin, special control devices monitor and ensure that the required power to properly cure the liner all the way through is supplied by the UV-lamps at all times. The curing process, with all its relevant parameters such as pressure, temperature, curing speed, and the actual power output of the UV-lamps, is precisely recorded and documented in the curing protocol. In the case of this 110-meter long (361 feet) Alphaliner1800H with 17.0 millimeters wall thickness, the curing table specified a curing speed of 0.27 meters (0.89 feet) per minute. So, the crew could now take a five-hour break to relax after a long, hard day of work, since UV-curing is basically a fully automated process. After midnight, the first section had been completed. Following the same procedure, the crew went on to install the second, 110-meter (361-foot) long, section of Alphaliner just a few days later. The Landgraben canal in Karlsruhe is now good to go for the next 50 years to come.

Contact and Additional Information

Tiefbauamt Karlsruhe
Lammstraße 7
76133 Karlsruhe, Germany
Phone: +49 721 133-7411
E-Mail: stadtentwaesserung@tba.karlsruhe.de

Jeschke Umwelttechnik GmbH
Helmholzstraße 1c
76297 Stutensee-Blankenloch, Germany
Phone: +49 7244 205 18-0
E-Mail: office@jeschke-umwelttechnik.de

Große Ahlmühle 31
D-76865 Rohrbach, Germany
Phone: +49 6349 93934-0
E-Mail: info@relineeurope.com