Sewer rehabilitation
The term sewer rehabilitation refers to process engineering and measures to restore or improve existing drainage systems. Sewers must be planned, built, maintained and operated in such a way that the structural condition is maintained over their useful life. Reports on incidents such as canal collapses, floods and water pollution, as well as previous studies, allow conclusions to be drawn about the type of possible impairment of the performance of existing drainage systems. The sewer rehabilitation can restore the functionality of the drainage system and extend the service life. Sewer rehabilitation is divided into repair, renovation and renewal.
Possibilities and limits
The area of application of the sewer rehabilitation is given comprehensively through the repair, renovation and renewal. The sewer rehabilitation measures necessary to meet the performance requirements should be included in a rehabilitation plan. In the area of repair and renovation in particular, modern process technologies for "trenchless sewer rehabilitation" have been developed. The European standard (EN 15885 German version 2010) specifies a system for the classification of techniques for the renovation and repair of sewers and sewers outside of buildings that are operated under gravity or pressure and include pipes, connections and manholes. It defines and describes technology groups and various general processes and materials.
Procedural groups
The sewer rehabilitation is divided into three process groups, repair, renovation and renewal, which result from the DIN EN 752 drainage systems outside of buildings - German version 2008 and the leaflet of the German Association for Water Management, Sewage and Waste eV (DWA) M 143, renovation of Drainage systems outside of buildings - August 2004 with parts 1 to 20. This classification can also be found in the leaflets of the Rohrleitungssanierungsverband e. V. (RSV) again, where detailed requirements, quality assurance, tests and applicable regulations and standards are described for many processes.
Almost all rehabilitation processes require access to the lines. If there are no shafts, a temporary construction pit or shaft must be created (costs). In general, pipe lining has clearly established itself as the most frequently used rehabilitation method. It is also possible to work from an access in / on the house (inspection opening) to the main sewer. However, if there are arches and / or inlets along the way, trenchless renovation may not be possible or only partially possible. Careful planning and a lot of know-how are required here.
Repair procedure
Such methods are used for localized damage. In the case of leaky sleeves, cracks (axial and radial) and damaged or faulty inlets, very good renovation successes can be achieved. However, it must be taken into account that repairs can cause new damage to adjacent pipes. For all procedures, a robot is almost always required beforehand for the preparation, such as B. necessary for milling off roots or protruding inlets.
Renovation process
Renovation methods are used for localized, repetitive damage and extensive damage. In this case, single or multiple sections lying one behind the other (channel sections between two manholes) can be processed in one operation. Coating processes are of secondary importance in the wastewater sector. Assembly methods are only used in large dimensions (> DN 1000 mm) due to the need to walk on them. A basic distinction is made between renovation processes with or without an annular space (close-fit or tight-fit). The most typical representatives of the renovation processes are the pipe lining processes. In addition, pipe lining processes are also used - here, among other things, the so-called "deformation process". These are lining pipes (mainly made of PE and PVC) with the same outside diameter as the inside diameter of the pipe to be rehabilitated, the cross-section of which is reduced for installation, deformed and then re-deformed after installation. An alternative or a useful addition to this is the TIP process (tight in pipe). Here, statically self-supporting new pipes made of PP-HM are installed as individual pipes or a pipe string in the sections to be renovated. This method can also be used for old pipe condition III, accompanied by fragmentation, deformation, misalignment. With the aid of a calibration sleeve, the duct is calibrated out during the pipe installation. The circular state as well as the pipe statics are restored. Milling work on the old pipe is not necessary due to the process. Another rehabilitation method is the wound tube method. A liner pipe is created in the old pipe by processing profiled plastic strips made of PVC or PE with winding machines, which are either positioned stationary in the shaft or moved through the sewer while the pipe is being wound. Depending on the system, the liner pipes are either fixed in the old pipe using grouting mortar or their diameter expanded within the sewer until the outer diameter of the liner clings to the inside wall of the old sewer pipe. The processed profile strips can also be reinforced with steel if there is a static requirement.
Renewal procedure
The renovation is divided into the trenchless method and the open construction method. The latter is conventional underground pipeline engineering. A distinction can be made between renewal with removal of the old line (remove old line, lay new line) and without removing the old line (new route). In the case of trenchless renewal, the pipe-eating process ( pipe jacking ( microtunnelling ) with the removal of the old line) or the burst lining process (destruction and displacement of the old line into the surrounding soil) can be used to lay the new line.
Shaft rehabilitation
The shaft rehabilitation comes into consideration with almost every rehabilitation measure of a pipe and is almost always necessary. The manholes are either completely renovated from the bottom (channel) up to and including the cover or only partially. Only the channel and tread, the crampons, the shaft walls or the cover. Either mineral materials or lining with GRP or other plastics are used.
House connection renovation
The rehabilitation of small sewers (≤ DN 250), especially property drainage, is a specialty in several respects:
- In the case of house connection sewers, the sewer operator (house owner - owner of the public sewer) changes over the course of the line, depending on the communal requirements.
- The house connection sewer has inspection shafts on the private property as standard. The integration into the main sewer usually takes place via fittings on the main line, i.e. without a direct connection to the shaft systems.
- The renovation can be carried out by renewing the pipes using the open construction method or using trenchless renovation methods. The pipe liner process has proven to be particularly efficient in trenchless rehabilitation.
The pipe liner is installed in the house connection renovation using the so-called inversion process. In the inversion process, the hose soaked with synthetic resin is, so to speak, "turned inside out" with a water column or pressure chamber using water or air pressure. As a result, nothing except the pipe to be rehabilitated comes into contact with the synthetic resin. After a specified curing time, the pressure can be released and a tube has formed in a tube. Small nominal sizes from DN 50 and changes of direction can also be managed.
Certified sewer rehabilitation consultant
Certified sewer rehabilitation consultants are trained in Germany by the Association of Certified Rehabilitation Consultants (VSB) and the Association for the Rehabilitation of Drainage Systems. The specialists trained in this way have the special expertise and the ability to select and plan the optimal renovation option from the technical and the economic.
The course had 1200 participants in the first 15 years up to 2012.
Others
Although a satisfactory number of regulations, standards and guidelines have been developed and published recently, customers and planners are still largely inexperienced. This is especially noticeable when it comes to the comparability of processes and their effectiveness in relation to the construction of new pipelines.
For various reasons, pipe rehabilitation usually has a very complex, short execution period.
Sewer rehabilitation costs
Sewer rehabilitation costs may be added. The amount of the cost depends on various factors. This includes, for example, the length and diameter of the sewer pipes, the length of the sewer, necessary pipe cleaning, the extent of branches or the obligation to have a pressure test carried out by the municipality.
If necessary, the costs of the renovation will be covered by the residential building insurance.
Individual evidence
- ↑ VSB website [1]
- ↑ Website of the funding association www.ZKS-Berater.de
- ↑ Press release from September 13, 2012