Depending on the fall height and the associated water pressure, the remaining, quantitative grain size is critical for wear. The less suspended solids there are in the water, the less wear there is on the pipe and turbine components. This increases the service life and economic efficiency. Under no circumstances, not even when using a Coanda rake, should a Desander be omitted, since in addition to its function of additional cleaning, it also calms the water to such an extent that the water level can be used to control the turbine. The water level in the Desander is scanned by a pressure sensor so that the power plant control system can use it to control the available water supply and thus the nozzle control so that the turbine can optimally process the inflowing water at any time. Another often underestimated function of the Desander is a pressure surge, which can occur at any time, for example, in the event of an EMERGENCY STOP of the turbine. In this case, the Desander, with its aeration and deaeration valves and volume, acts as a pressure equalization vessel . Through this mechanism, it prevents a pipe rupture and continuously reduces the pressure surge.
The connecting flange is connected to the supply line from the reservoir/rake. The water flows into the metal body and hits the lamellae packages with an undefined flow velocity. Here, the kinetic energy is extracted from the water until it approaches zero. The water is slowed down by the deflector lamellas to such an extent that the sediments contained in the water settle in front of the flushing openings. Precisely defined baffles prevent further transport of the sediments. At regular intervals, the flushing pipes are alternately opened by means of an electrically operated valve and the sediments are discharged in a controlled manner. The flushing process is so short that the turbine loses only a small amount of power and remains in operation compared to conventional Desander systems. The cleaned water leaves the Desander via chamber 2 in the direction of the pressure pipe. To prevent turbulence and air pockets from occurring when the water enters the pressure pipe, an inlet cone is fitted at the end of the Desander. Air pockets could lead to cavitation and thus to destruction of the pressure pipe, and in any case reduce the output
The level in the Desander is regulated by a pressure sensor and the power plant control system connected to the pressure sensor so that the water level in the Desander moves within the factory-calculated operating range. Thus, the Desander level is used as a constant parameter for turbine control. Several aeration and deaeration valves on the top of the Desander ensure safe operation. A lockable access dome is installed in each Desander for inspection and control work. To prevent rusting, the entire outer surface of the Desander is painted with an elastic plastic paint specially designed for underground use. We provide a 15-year rust warranty on our Desander, and up to 30 years if a maintenance contract is signed. Each Desander is supplied, as is our custom, with detailed operating instructions and inspection book.
