Membrane Filter Elements
Status: 06/2001/01 Operating Manual 39
6.4 Cake washing
Cake washing is an additional process step during separation. The original filtrate or mother
liquor is replaced with a washing medium.
Two different methods are used for cake washing decribed in the following (Chapter 6.4.1
and 6.4.2).
The required filtration or washing pressure is generally determined by the dewatering
characteristics of the suspension.
The maximum permissible pressure depends on:
• the permissible operating pressure of the press frame
• the permissible pressure and temperature stress of the membrane filter elements.
Read off the permissible filtration and washing pressure in Graph 11 or 12 (page 62).
• The pressure-temperature limits shown were determined in practice. However, please
note that in a few isolated cases upward or downward corrections are required.
Caution
• If a reservoir tank is provided for the squeeze water, ensure a sufficient geodetic
height difference.
- The water level must never be above the lower edge of the filter elements, as
additional water accidentally flowing into the membrane chambers will lead to
malfunctions.
- The geodetic height should not exceed the vapour pressure of the water, as
evaporation disturbs the pumping off of the squeeze water.
• The drain line must always be below the water level of the reservoir tank to prevent
air from entering the system and destroying the suction effect during draining.
• To prevent disturbances during filtration resulting from residual water in the filter
elements, open the drain valve during filtration.
CAUTION
