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Inflatable pipe plugs provide a method of surge flushing that can be easily installed and used. They can be installed in the manhole shaft without major structural modifications [FI-HST]. During a dry weather spell, the plug is rolled up and stored in the manhole above the sewer flow. (Image: Inflatable pipe plugs - designed to back up sewer flows at low water levels) (Image: Wastewater volume activated flushing system - Inflatable pipe plug) |
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To produce the characteristic surge wave, the plug is abruptly deflated through a cylinder valve. The hose is entirely bled of air by the backed up wastewater. After the flushing procedure is completed, the flushing hose is rolled back into its initial position. (Video: Automatically inflatable pipe plug) |
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Another further development in the field of surge flushing is the rotating elbow, which has not yet found a wide demand in the industry [FI-Kasap]. (Video: Rotating elbow) Video: Rotating elbow [FI-Kasap] [Image: visaplan GmbH]. This interactive object is only visible online. |
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(Image: Rotating elbow) (Image: Rotating elbow) Images: Rotating elbow [FI-Kupcz]. |
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Investigations revealed that extensive and partially solidified deposits with critical erosion shear stresses up to 14 N/m2 could be eliminated up to a channel length of approximately 300 m. Sedimentation of the mobilised deposits was prevented up to a length of 700 m. These results were confirmed by an analysis of the surge wave in a large diameter sewer [Lützn96]. (Image: Rotating elbow - Surge flushing analysis of the erosion shear stresses in a … |
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The following surge flushing methods will now be presented in more detail:
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Jul 20, 2012 Flushing systems with a tipping bucket are used for the automatic cleaning of stormwater storage basins (e.g. stormwater sewer, stormwater overflow basin etc.). The flushing water is stored in a relatively small reservoir in the form of a tipping bucket or pivoting drum, from where it is released abruptly in order to form the surge wave. (Image: Tipping bucket detail) |
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Jul 20, 2012 The emptying of the water reservoir is automatically triggered by a shift in its centre of gravity as it reaches the maximum filling level. The cleaning phases phases of the tipping bucket system are shown below. According to [FI-UFT], the gradient of the individual flushing lanes should be between 1% and 5%. (Image: Tipping bucket process - Filling phase) (Image: Tipping bucket process - Flushing phase) (Image: Tipping bucket process - End of flushing) |
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Jul 20, 2012 For the dimensioning and selection of the drum, the manufacturer provides dimensioning diagrams that are based on the Brombach formula [FI-UFTa] (Equation A / Equation B). (Equation A) (Formula: Spülkippe - Bemessung und Auswahl A) with:
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Jul 20, 2012 The shape parameter that was also introduced by Brombach has to be empirically checked and determined for the individual drum shapes by each manufacturer. An example for such a diagram with a flushing lane gradient of 2 % is shown. (Image: Design diagram for the dimensioning of a tipping bucket with a flushing lane gradient of 2 %) |
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Flushing systems using a flushing chamber serve to clean stormwater sewers and stormwater tanks. The flushing chamber is a specially designed structure capable of storing stormwater during flood events and back up flushing during cleaning operations. Depending on the type of the sealing device, a distinction is made between the:
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(Image: Flushing chamber schematic - initial stage (Biogest-System)) Phase 1 (Image: Retention phase of a vacuum stormwater tank system (Biogest-System)) Phase 2 (Image: Retention phase of a vacuum stormwater tank system (Biogest-System)) Phase 3 (Image: Retention phase of a vacuum stormwater tank system (Biogest-System)) Phase 4 (Image: Flushing chamber schematic - release of the flushing water) Phase 5 Images: Flushing of a stormwater tank vacuum chamber … |
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The cleaning effect of this system depends on the capacity of the flushing chamber and the specific local conditions, e.g.:
The chart shows empirically determined values for the required specific capacities of the flushing chamber and different filling heights [Loren1998] |
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In the case of the flushing chamber with a flush gate, the lower opening of the flushing chamber is closed by means of a flush gate. The filling of the chamber depends on how the sewage flow is guided and can, for example, be implemented by arranging a restrictor or via check flap gates in the chamber walls. Depending on the operation mode the system type, the opening of the gate is triggered either by a water level measurement (with auxiliary energy) … |
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The following flushing chamber dimensioning diagram from the company HST-Systemtechnik GmbH [FI-HST], illustrates that the required size of the flush chamber is inversely proportional to the base slope and proportional to the flush lane length. (Image: Required flushing chamber volume [m³/m] for the cleaning procedure of stormwater tanks depending on the flushing length and the invert gradient) |
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Surge manhole flushing systems are self-activating systems that are operated without auxiliary energy to automatically and regularly flush non-accessible sewers (DN 200 and DN 400). They are generally installed in the upper sections of the sewer line [FI-Funke]. (Image: Surge manhole flushing systems) |
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(Image: Surge manhole) The surge manhole "FABEKUN system" consists of a 1.0 m high precast concrete section that is placed on an ordinary manhole base. It contains two DN 150 water inlets at the top and a large outlet at the bottom, along with a ventilation/overflow pipe. The flush valve is located in a chamber bellow the outlet opening, and is activated by a floating ball that rises and sinks with the water level in the manhole.
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