BIERI VERTICAL SAND FLUSHING SYSTEM

In run-of-river type hydropower projects, suspended particles in water taken by intake cross the conveyance line and cause severe wearings on turbines, nozzle valves, control devices and pressure pipes and incur very high repairs. The wear on the turbine is mainly influenced by the size of particles remaining in the water, the particle distribution, shape and hardness of the suspended solids and the net fall heights. To remove sand deposits in desanding basins, two different horizontal and vertical flushing system is used. The horizontal flushing system which is conventiaonally used in Turkey is the Buchi system that requires a flushing gate at the end of the basin and capable of only partial flushing of the sediment deposits in front of the gate. Since the whole basin should be completely emtpy during the flushing process, hydropower plant operators can not make production due to lack of water in the corresponding basin. In buchi system, the sediment deposits sometimes could not be removed completely from the sytem by flushing and requires stuff and equipment to remove the sediment which results in loss of time and money. The Bieri flushing system which works with the vertical flushing principle is the best sand removal system that could be used in a hydropower project. 

      HOW BIERI VERTICAL SAND FLUSHING SYSTEM WORKS?

The water flows through in the longitudinal direction. The overfall (7) at the end of the basin maintains a sufficient water level and a regular flow through the basin. A calming rack (4) at the entrance of the basin calms turbulence. When sufficient sand has collected inside the flushing unit (5), the flushing unit at the base opens hydraulically in accordance with preset opening dimensions and flushing times. The sand is vertically flushed through the openings into the flushing channel (10) from where it is flushed back into the river. A sand flushing unit (5) consists of 2 aperture plates, one over the other, horizontally arranged against each other on the bottom of the basin. The lower plate is rigidly fixed to the concrete structure and the upper plate is moved by 2 hydraulically operated servomotors (6) in the direction of the desander axis. By opening the flushing unit (upper plate), the flushing operation takes place through pre selected openings of max. 180 - 190 mm (two openings per 1 m length). The flushing is initiated at predetermined intervals or by the level of the accumulated sand. This means a minimum of flushing water is used and there is almost no interference in the production capacity of the turbines. The system can also be manually activated in emergency cases or for special purposes. Outlet flushing gates for each basin (13, if installed) are fully opened during the flushing operation and serve as the closing unit for the flushing channel (10).

The BIERI desander with its optimised control system requires a minimum of flushing water. Flushing is only activated if the deposit of sand in the basin has reached a pre-determined volume. This is usually about every 2 to 24 hours, but can sometimes be at even longer intervals, weeks or months. The duration of the flushing time may be only 2 to 3 minutes, including the opening and closing of the flushing units but depends on the total length of the flushing channel. The quantity of deposited sand is measured in each basin individually.  Flushing is only performed, therefore, for those units having acquired the predetermined sand deposit level. The flushing is executed in stages (only one unit open at a time), so that the water quantity for the turbines is only marginally influenced.

      ADVANTAGES OF BIERI SYSTEM

  • Amortisation of the installation in a short period of time due to minimal production stops,

  • Approx. 50 % less flushing water required compared to a  horizontal flushing  desander,

  • Continuous use of flushing water not required,

  • Higher economical efficiency of the turbine system,

  • Selective flushing only if the sand height of each separate desanding section in the basin has reached the predetermined level,

  • Strong local flushing flow due to the construction of the sluices (opening every 0,5m),

  • Vertical flushing assures a strong flow of water over the numerous sluice openings providing a highly effective flushing of even tough sediment,      

  • Possibility to adapt the system to the local constrains,

  • No obstruction of the sliding mechanism,

  • Self-cleaning desanding,

  • Reduction of the repair-cycles of the turbines.

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To get detailed information about BIERI flushing system and budget quote for your project please contact us.