Installing a 280-metre-long GFRP pipe liner with a 1500 diameter and only ten millimetre thickness is quite a feat. And to pull it all off under a river with the sewer separated from the river's water by only one metre of earth – that is something else entirely. That is what Brandenburger Liner from Landau accomplished in Krakow, Poland, in August under somewhat difficult circumstances.
Numerous pedestrians, cyclists and joggers make use of the banks alongside Poland's longest river, the Vistula. Some of them may know that the Vistula is normally five to six metres deep, nine metres if there is flooding, at this part of Krakow. But most of them would not know that four sewers, now sixty years old, pass under the river there. Completed in 1954, since then they have transported sewage from one side of the city with a population of 760,000 to the other.
One of them needed rehabilitation. The challenge: installing the 26-tonne-heavy liner across the entire width of the river; in other words over a length of 280 metres with a diameter of 1.5 metres. Brandenburger Liner GmbH & Co. KG has risen to this great challenge and produced the liner on the new, larger production line.
Under the management of Marc Albrecht for the application engineering team from Brandenburger Liner GmbH & Co. KG, along with the employees from AKWA Sanierungstechnik GmbH managed by Piotr Grawżym, they dug down eight metres into the sewer in Krakow. And they needed to go even deeper then during the crossing, because the culvert – a pressurised line for crossing under the river – drops a further two metres. It was not the culvert itself that proved the acid test of this construction site, but the other local and technical conditions.
A major, ambitious project of this kind in Poland's second largest city requires meticulous planning. Especially as certain toxic gases collect in the walls of this sixty-year-old sewer. After pumping out the sewer water and cleaning, the dirt was indeed gone, but the gases were still trapped in the concrete. According to Grzegorz Owczarek, managing director of AKWA, the sewer was vented for two months to let the gases escape. Before that, workers could only go into the sewer if they were wearing breathing apparatuses.
The sewer and its two accesses on the left and right of the Vistula needed to be prepared for the delivery of the liner. Employees of AKWA had previously dug out wide windows and a construction pit at the entrance, from where the liner could be drawn in later.
To ensure that no-one sank into mud in front of the shaft, teams from Brandenburger and AKWA heaped up minerals at the entrance on the first day of construction. The next steps were to smooth out sharp edges in the shafts with a power grinder, position the cable winches as well as the conveyor belt and finally draw in the foil over which the liner was to slide into the sewer.
Made to measure at the arrival of the liner
The arrival of the liner at the construction site the next morning was not an easy task, because the only access to the river is a narrow street in which an overlength lorry cannot turn around. The vehicle with the heavy wood crate from Landau had to turn around before the entrance and back up several hundred metres to the construction site entrance, much like threading a needle. Manoeuvring had to be done precisely to the centimetre until the lorry was situated in front of the conveyor belt.
Then the shock at ten o'clock: The sensor of the conveyor belt failed. With the help of the staff from Landau, Marc Albrecht was able to solve the problem quite quickly, allowing the folded liner to be drawn into the sewer without any further difficulties.
Luckily it only started raining once the liner was already in the sewer.
Lire la suite: http://www.akwa.eu/
There wasn't much of a wait for the next obstacle, however: The packer, i.e. the aluminium pot for the liner end, was too large for the narrow shaft, so it had to be disassembled and the parts transported down by the cable winch before it could be installed.
By the late afternoon the pipe liner was "inflated" and in position. Manuel Geißler, application engineer from Brandenburger Liner GmbH & Co. KG gave the go-ahead for the light chains with twelve UV lamps at a power of 1000 watt each, which were drawn through at 60 centimetres per minute to cure the materials.
Proud of what was accomplished
Inspection of the liner during the next morning confirmed: The construction project, worth 400,000 euro, could be completed successfully – thanks again to the good cooperation of Brandenburger Liner GmbH & Co. KG and P.P.U.H. AKWA. “We are quite proud that we could achieve the installation of a liner of this size”, Michael Schloder, managing director of Brandenburger Liner was glad to report. “Our employees have completed a big job and proven how important good preparation and flexibility is on site.” He gave special thanks also to the P.P.U.H. AKWA.
Grzegorz Owczarek, managing director of AKWA, was also happy with the successful conclusion of the major project, and reported that a member of the staff from the Krakow water works visited the construction site and complimented them on its successful completion.
Learn more about AKWA: www.akwa.eu