The fine screen forms the last stage of the mechanical water treatment chain before the pumps, and protects the latter. A regular, automatic cleaning mechanism is envisaged due to the narrow width of the gaps, which leads to a high build up of contamination to be removed.
For effective pump protection, we recommend gap width between 10 – 40 mm. Depending on the impeller size of the downstream pumps, gap widths of
- 20 – 40 mm for the main coolant circuits
- 10 – 20 mm for the auxiliary coolant circuits
have proven to be effective. The ultimate decision is specific to the project in question.
Water flows through the gaps in the fine screen, which retains macrofouling larger than the size of the gaps. When a pre-set level differential in the inlet and outlet of the screen is reached, initiated via a time switch or manually, an open bowl-shaped rake carriage moves from its highest position, its resting position, along lateral side rails as far as the channel floor. At the lowest point, the rake carriage closes and reaches into the gaps of the screen grid with its tooth comb.
Its wide opening angle facilitates acceptance of contamination accumulated in front of the screen grid. After passing through the air-water level, the rake carriage reaches a force-controlled scraper above the floor level which discharges the dirt from the rake carriage into a container or a gutter.