The polluted medium flows from outside to inside through the metallical, cylindrical filter element. Dirt particals which are bigger than the slot of the element, stick on the surface of the element. These particles will be removed with the scraper-blade by turning the element and the dirt sinks to the filter sump. From there the dirt can be purged in intervals manually with ball-valves or automatically by sluices (with minimum loss of medium). The cleaning and discharge occur without interruption of the flow. This ensures a continuous use of our self-cleaning filters. For gel-like and fibrous particles special laser drilled or perforated elements are available. Those were developed especially for applications where conventional slot tubes could not be used e.g. the filtration of algae, fibres etc. out of water.