Lenntech Water treatment & purification Lenntech Water treatment & purification

Automatic hydraulic selfcleaning screenfilter

Automatic hydraulic self-cleaning screenfilters are applied in cooling towers, heat exchange protection, ion exchange protection, industrial waterwater recycling, effluent polishing, water supply, filtration for micro irrigation.  The automatic hydraulic selfcleaning screenfilters normally put in the place of the sandfilter. Op deze pagina wordt er ingegaan op de werking van de hydraulisch zelfreinigende screenfilter, technische aspecten en de voor- en nadelen van deze filter.

You can read about technical aspects, operation and the advantages and disadvantages of the screenfilter.

Technical aspects:

- Max water temperature: 65o C, high temperature till 95 oC available
- Max flow: 30 m3/h till 200 m3/h
- Filtration: 120 micron (available   from 10 till 3000  micron)
- Water use: 8 liter per backwash
- Backwashtime: 10 seconds
- Needed pressure: min 2 bar and maximum 10 bar, pressure loss at backwash  0,1 bar
- Minimum flow: 70 liter


Water enters the filter through the inlet (1) and passes through the coarse screen (2) that functions as a first stop for rough particles. Water then reaches the fine screen (3) which further purifies the flow by separating smaller particles from the water. As more water flows through, impurities build up on the fine screen. As impurities on the screen accumulate, a pressure imbalance is build up between the internal section of the fine screen (3) and its external section.

When the difference in pressure reaches the preset value on the differential pressure indicator (11), a series of events is triggered while water continues to flow to the system units. The controller transmits a signal for a ten second flushing cycle. The flushing valves (4) opens, pressure is released from the hydraulic piston (5) and water flows outside. Pressure in the hydraulic camber (6) and the dirt collector (7) is significantly lowered resulting in a suction process via the suction nozzles (8) to the dirt collector (7) and from there to the hydraulic chamber (6) through the flushing valve (4) outside. The hydraulic motor (9) simultaneously rotates the dirt collector (7) around its axis. The pressure is released from the piston (5) and the high pressure inside the filter causes lineair movement of the dirt collector. The combination of the lineair movement and rotation efficiently cleans the entire internal screen (3) surface.

At the end of the ten second cycle the flushing valve (4) closes and the operation of the hydraulic motor (9) is stopped. The increased water pressure returns the hydraulic piston (5) to its initial position. The filter is now ready for the next cycle, with clean and filtered water flowing through the outlet (10).

The ten second flushing cycle resumes operation whenever the difference in pressure reaches the preset pressure value set on the differential pressure indicator. If the pressure difference remains unchanged after one cycle, another cycle will start after a delay of ten seconds.



  • The filter needs 2 bar for operation.
  • The filter can treat water with contains a lot of mud.
  • The filter is able to reduce the amount of mud from 10% to 1%.
  • The filter is able to reduce particles with a size of 10 micron and bigger.


  • Biological filtration can not take place.
  • Chemical filtration can not take place so iron removal is not possible.


More information about automatic electric selfcleaning screenfilter.

Here you can find an overview of filtersystems.

Overview filtration-subjects.

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