Vacuum filters are simple and reliable machines and therefore have gained wide acceptance in the chemical, food and pharmaceutical industries.
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The filtration areas for standard machines are:
The various types of vacuum filters may be grouped as follows: |
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There are two concepts in layout design:
Generally industrial vacuum pumps such as the liquid-ring or the rotating-vanes type operate at a vacuum of 500-600 mmHg. Hence in barometric leg layouts the filter is mounted 8-9 meters above ground level to ensure that the liquid level in the leg will not flood the filtrate receiver. This applies to liquids with a specific gravity of 1 however for heavier liquids the filter elevation with regard to the ground level may be lowered. Barometric leg layouts require therefore a structure for the filter but the advantage is that the filtrate pump operates under a positive suction head. On the other hand, floor mounted layouts require a receiver mounted filtrate pumps of special low NPSH design to effectively deliver the filtrate under the full vacuum on the suction side. The scheme below also shows a floor mounted layout with a partitioned receiver and two one-way flaps that open and close by solenoid controlled air balancing pipe. However, although this design uses a conventional positive suction head pump, it is rarely used owing to the moving parts of the receiver and the risk of vacuum leakages from the flap seals.
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The block diagram for a typical filter station and its components may look
like this:
The advantages and disadvantages of vacuum filtration compared to other
separation methods are:
Advantages
Disadvantages