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Operation & maintenance manual, Drum filter HDF 12/16/20/24 -series
7. FUNCTION
7.1 Intended use
The filter is designed and manufactured to remove solid particles in unpressurised water flow
systems. The filter is not a pressure vessel.
7.2 Non-intended use
Unless approved in writing by Hydrotech, the filter must not be used to filter liquids other than
water. The filter must not be installed in an environment with an explosive atmosphere or
another risk of explosion, such as high concentrations of dust.
7.3 Filtration and backwash process
1. The water to be filtered flows with gravity from the inside of the filter drum out through the
filter elements.
2. Solid particles are separated from the water by the filter fabric that is mounted on the outside
of the filter elements, while the clean water passes through the fabric to the outside of the drum.
3. Operating mode AUTO – The solid particles entrapped on the inside of the filter fabric gradual-
ly reduce the water flow through the drum. The water level on the inside of the drum begins to
rise. Once the water reaches the level sensor, drum rotation and backwashing begin. Operating
mode HAND – Drum rotation and backwash are continuous.
4. The backwash nozzles spray clean wash water from the outside of the filter drum. The solid
particles that accumulate are washed away from the filter elements to the sludge trough, at the
same time as the drum rotates.
5. With the help of gravity, the removed particles run out from the filter along with the backwash
water.
