Sewer rehabilitation with SPR technology in Poland: Project wound to perfect close

In cases where sewers with very large diameters need to be rehabilitated in the middle of a busy town, spiral-wound pipe technology provides a time-saving and economical solution, without major hindrances for the residents or traffic. As a result, the town of Kety in Poland contracted to have the SPR™ spiral-wound pipe variant used for the trenchless rehabilitation of segments of two concrete sewers at the end of 2012. The town of Kety was intent on ensuring a good hydraulic function for the next decades and to take precautions against infiltrations. The special requirements of the two egg-shaped profiles made SPR™ spiral-wound pipe the obvious choice. The main collection sewer is located on Wzdluz Torow Street and feeds directly into Kety's treatment plant. The wastewater sewer on Slowackiego Street is located in the middle of a residential area. Because both of these sewers reach high peaks of wastewater flow distributed over the day, taking them out of operation for renewal was not an option. In principle, the concrete pipes with diverse inlets and bends could have been rehabilitated using CIPP lining; however, not in these dimensions and not with the special egg profile shape. For this project, SPR Europe took over the installation of the SPR™ liner in the two egg profile pipes; the first with diameters of 1000/1720 mm and a length of 420 metres, the second with diameters of 1400/2100 mm and a length of 93 metres.

The rehabilitation process

In the SPR™ spiral-wound pipe method, reliably applied since 1978, an endless PVC profile strip is wound into a pipe inside the sewer; the resulting pipe can measure several hundreds of metres in length and up to 5500 mm in diameter. A normal inspection manhole is sufficient to bring the winding machine and the PVC profile strip into the sewer. The rehabilitation equipment above ground, which includes the drums with the endless PVC profile strips and the rehabilitation vehicle, requires significantly less space than the equipment required for open-cut renewal. This benefited the installation team, because the sewer with diameters 1000 mm was located in the middle of a residential area and the sewer with diameters 1700 mm was located in a narrow street 500 metres in front of the treatment plant. In a period of less than 10 weeks, with controlled live flow in place, the steel-reinforced, endless PVC strips with key-and-slot joints were wound into a new waterproof pipe inside the existing sewer. The winding machine, which is installed in the existing pipe, moves continuously with the profile strip as the coils are joined together. The winding machine presses and locks together the edges at each wind, to ensure that water cannot leak through. Once a drum was used up, the new profile strip was joined to the existing strip in a portable butt welding unit. Since the winding machine was set to wind with annular space between the host pipe and the wound PVC profile, the bends in the two sewers were also no problem.

A fine conclusion

The bracing, grouting as well as the final opening of the connections of many inlets with 200/300 mm diameters were carried out by the Polish partner company INFRA. They bricked off the end terminations of the spiral-wound pipe to the concrete wall and sealed the edges between spiral-wound pipe and branches with glass fibre laminate. Annular space that had been intentionally left open between the new spiral-wound pipe and the existing pipe was then filled with high-strength grout, to ensure the static characteristics of the spiral-wound pipe. After some further civil engineering work, Strabag AG completed the entire rehabilitation project to the full satisfaction of the town of Kety.

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