Successful renovation of large-profile pipes in Dortmund / Germany and the accompanying challenges, big and small
Dortmund / Germany, March 2020 – Nowadays, lining sewerage and drainage networks with cured-in-place pipes as specified in DIN EN ISO 11296-4 is standard practice. However, egg-shaped profiles with a cross-section of 1800 mm present a far greater challenge and call for specialist expertise. The project in Dortmund involved the trenchless lining of no fewer than four large-profile sections with a total length of approx. 285 metres, running straight through a busy residential area in the east of the city.
In this case, iMPREGLiner GL16, egg-shaped profile 1200/1800, was selected as the most suitable product for the task. Due to the material’s high degree of robustness and the structural requirements the linings had to meet, wall thicknesses of between 14.6 and 17.3 mm were used.
The supervising engineering firm was S&P Consult GmbH from Bochum; during the planning phase for the rehabilitation work, they conducted a comprehensive assessment and evaluation of the brick sewers’ condition in order to check their structural stability and computed the statics for the liners that were to be installed.
The construction work was contracted to Swietelsky-Faber GmbH Kanalsanierung and presented the firm’s Blomberg branch with several challenges to be overcome. Swietelsky-Faber GmbH Kanalsanierung is a pioneer in the field of UV-cured liners and currently operates 12 trucks equipped with the necessary UV technology in Germany. In the light of its 20 years of experience in this field, the company opted for liners from manufacturer iMPREG GmbH for this project.
The city of Dortmund values certification and quality assurance
When it comes to the city’s drains and sewers, Dr.-Ing. Christian Falk, chief technical officer of Dortmund’s municipal wastewater services, counts on the quality guaranteed by the RAL-GZ-961 label – i.e. excellent references, the certification awarded by Güteschutz Kanalbau (The German Quality Audit Association for the Fabrication and Maintenance of Drains and Sewers – Quality Protection Sewer Construction), a wealth of experience and the reliability of both the contractor and the materials technology deployed. Dortmund also pursues a policy of sustainable investment management in terms of the proper operation and asset maintenance of the network.
Intensive preparation of the site was required before the actual lining work could begin. The TV inspection, the underground preparation of the sewers and the safeguarding of the utility lines that crossed the construction site all had to be organised prior to the commencement of works. This rehabilitation project was extremely urgent and called for swift action because some sections of the original brick sewers were assessed as being in poor condition (Condition III according to the German DWA-A 143-2 national standard). As a result, the structural stability of the host pipe system had to be restored in some places. In order to prevent further deterioration, the rehabilitation work was to be conducted as soon as possible – not least of all for economic reasons.
Flexibility despite heavy rain
The weather gods did their best to wreck the timetable for starting the rehabilitation work – unusually heavy rainfall events meant it had to be rescheduled. However, thanks to the flexibility of all those involved, the construction work could be resumed again quickly.
Challenging conditions due to corona
The prevailing corona pandemic had an impact on this project too. In Germany, wastewater management is classified as an essential service, the sewer system counts as critical infrastructure and it is imperative to keep the wastewater network running smoothly. A long interruption or even worse a construction freeze would have been inacceptable to both the operator and the local residents. As a result, it was possible to execute the project even in this exceptional situation. Swietelsky-Faber GmbH Kanalsanierung issued updated risk assessments and safety-relevant instructions that were monitored for efficacy by both management and a safety team, including on-site inspection. The iMPREGLiners were ready to install and were inserted in three stages.
The high groundwater level and resulting infiltration of the pipe sections that needed to be rehabilitated presented another challenge. Therefore, as well as sealing measures for the manholes and in the sewer, the liners were also equipped with an additional factory-applied outer foil as a precaution.
Two GL16 liners with an egg-shaped profile 1200/1800, a wall thickness of 14.6 mm and a length of approx. 78 m and 90 m were inserted and cured quickly. In one section, the bottom of the sewer cascaded for approx. 0.5 metres, with the result that a special manhole connection had to be hand-laminated using resin with GRP fibres. This complicated the installation of the extremely heavy liner considerably, but the experienced team mastered the challenge to achieve a flawless result.
When it came to inserting the third liner (GL16, egg-shaped profile 1200/1800, length approx. 112 m), the thickness of the walls (17.3 mm) and the heaviness of the packers were also challenging in terms of both transport and installation.
Precise planning, cooling of the liners during transport, short storage times and swift installation were essential for this project because, due to the thickness of their walls, the liners contained peroxides as a catalyst.
All sewers successfully rehabilitated
The installation of the liners by Swietelsky-Faber GmbH Kanalsanierung ran smoothly and without incident. ProKasro Jumbo cores with an output of 12,000 watts were used to cure the liners.
“We’re delighted that we were able to work at all in these difficult times, and even more so that everything went so smoothly and quickly despite the heightened safety measures,” says project manager Harald Müller.
The excellent final result is a reflection not just of the team’s successful collaboration with the client, the engineering firm and the liner supplier, but also of its many years of experience.