Barthels Hof in Leipzig is a historic building complex with shops, other commercially used premises, apartments as well as the restaurant of the same name in the heart of the city and also one of the most important tourist attractions in the Saxony city. Baroque parts of the ensemble of buildings from the 18th century have remained preserved to this day.
The rehabilitation of the waste water pipes in Barthels Hof is the last part of extensive renovation work on and in the building complex. The so-called in-house rehabilitation has been ongoing since September 2020 and is expected to be concluded by the end of this year. “No single pipe in Barthels Hof will be left out during the work – from the DN40 shower pipe to the DN 200 main pipe,” says Thomas Miller, managing director of Pipe Bull GmbH, which was awarded the tender for the pipe rehabilitation work. The recently founded company from Landau in the Palatinate region specialises in the rehabilitation of property and building drainage pipes using different methods including preliminary work such as TV inspection and sewer cleaning. Its employees, who are now 19 strong, operate throughout Germany.
At the outset, the client also considered replacing the downpipes, collecting and main pipes using an open construction method. That proved disadvantageous for several reasons, however: “A particular feature of this project was the difficult accessibility to the pipe shafts spanning multiple floors. These are concreted on three sides and partly bricked in on one side,” explains Sven Heuermann from the engineering firm responsible, Drews Gebäudetechnik from Berlin. “In addition, the shafts between the individual storeys are open, meaning that accessible floors would have to have been installed in case of entire rehabilitation using open construction,” Heuermann goes on to say. Added to this is the fact that trenchless rehabilitation proved to be more cost-effective than an open replacement of the pipes.
The pipe length needing to be rehabilitated amounts to a considerable 1.2 km. A challenge when it comes to rehabilitation are the many bends in the pipe run, which are often encountered in Germany. “Sometimes we find six to seven 90-degree bends on the DN50 pipes over a length of just two metres,” says Miller describing the situation in Barthels Hof, “and the DN 100 downpipes do not run straight from top to bottom, but instead also have another five to six 90-degree bends over approximately 40 metres. This requires good preparation and plenty of skill,” says Miller. And the many and often unexpected changes in dimensions do not make the rehabilitation work any easier either.
Over recent years, Barthels Hof has had to battle with water damage. A TV inspection revealed the extent of the damage: “The plain-end pipes installed are extremely damaged and show signs of burst pipes, cracks and severe corrosion,” describes Heuermann. Among the damage profiles, there are also cracks measuring several centimetres or even broken pipes in places.
Due to the pipe runs and the damage profiles, Pipe Bull adapted its own milling tools for the rehabilitation preparation work. It has now been and is possible to easily use them in pipes with bends as well as in the highly damaged grey cast iron pipes, without them breaking apart. Extremely corroded pipes, some of which broke off as part of the preliminary work, were “bridged” using short liners for stabilisation purposes during the previous course of rehabilitation. “In this respect, a change of plan at short notice was necessary,” says Miller.
As part of the pipe rehabilitation in Barthels Hof, Pipe Bull mainly opted for the Brawoliner® HT, specially developed for rehabilitation inside buildings and approved for this by the DIBt. Besides this, the brush coating method as well as open construction in many places are also used – the latter for instance for suspended pipes, which are directly accessible, or for changes in dimension that appeared unnecessary.
Pipe Bull has been working closely with the Brawoliner® manufacturer, BRAWO® SYSTEMS, since the company was founded in 2017 and has been impressed by the quality of the Brawoliner® ever since. The seamless textile hose with seamless film coating is suitable for the rehabilitation of pipes with nominal widths from DN 50 to DN 400. For the Barthels Hof project, its flexibility and the resulting possible applications in defective pipes with bends up to 90° and up to two changes in dimension are decisive benefits.
The liners previously impregnated with epoxy resin are inverted with compressed air using so-called liner cannons and then cured using steam or ambient temperature. “The liner cannons are connected to each other by a pressure measurement probe or a Bluetooth monitoring box, which constantly measure the air pressure where compressed air remains in the liner for a certain time for curing purposes. If the pressure drops, the monitoring equipment sends a warning by SMS,” Miller explains.
The Brawoliner® HT is installed with an open end (open-end method): calibration hoses and liner end caps are sometimes used. Once the liners have cured, the inlets are opened. Pipe Bull makes do here completely without pneumatic milling robots and instead uses compact, electrically operated vortex cutters for all inlets, for which no compressor is needed. “In this respect it is a pilot project for us,” says Miller. “But so far it has worked very well – despite the complicate pipe runs.”
Wherever the Brawoliner is unable to be used, for example on DN40 pipes, or where the damage is not so serious, Pipe Bull in Leipzig employs the brush coating method up to DN 100. This is a brush coating system from Picote Solutions, with which epoxy resin is applied to the pipe via a hose and rotating brushes attached to it. “The hose is pushed into the pipe in the flow direction. Whilst moving backwards, two to three brushes distribute the resin evenly onto the pipe wall,” says Miller describing the process. An important aspect here, he says, is that the brushes are always bigger than the internal dimension of the pipe, meaning that the resin touches the inner pipe wall along every centimetre.
Because Barthels Hof is located directly in the inner city, it is only possible to deliver the materials little by little in smaller quantities. On the other hand, an empty commercial unit was available for equipment at Barthels Hof. Work is carried out on site in three groups: “The first group is responsible for the preliminary work. The second group performs the rehabilitation, whereby the choice of the respective method is down to the project manager. Finally, the third group is responsible for the acceptance inspection and repairs any faults if necessary,” Miller explains.
During an in-house rehabilitation, the acceptance of the owners or tenants in the building for the measures and hence their willingness to cooperate are factors that should not be underestimated. After all, the rehabilitation company works in very sensitive areas. Although relatively unproblematic in Scandinavia, in these parts much more persuasive effort is usually needed. That is why, according to Miller, great emphasis has been placed on the communication with the tenants before and during the rehabilitation process. Alongside this, Thomas Miller also points out the importance of time management: “From the pipe cleaning up to the final inspection, certain time windows are clearly specified, which with regard to the acceptance of the in-house rehabilitation among the tenants also have to kept to at all costs.”
In the meantime the project has largely been completed; work is currently being carried out on the fifth of six inlets. Pipe Bull reckons it will finish the in-house rehabilitation by the end of this year.
Published on 12.08.2021 on bi-medien.de: https://bi-medien.de/fachzeitschriften/umweltbau/kanalsanierung/inhouse-sanierung-im-barthels-hof-gelinert-und-gebrushed-bis-in-die-letzte-leitung