Filter press

Rather, when throughput flow rates drop to an unacceptable level, the cycle is ended. The last most common usage of the filter press is as a "variable volume" filter through the use of a filterplate known as a diaphragm or membrane plate. This type of plate has a flexible drain-field which when sealed around the edges forms an integral bladder or diaphragm that may be inflated to physically press additional liquid from the filter cake. This process can significantly reduce the typical elapsed time for a press cycle and produce a dryer cake product or more uniform cake dryness from cycle to cycle.

In these applications the press is not sized for the quantity of solids holding capacity but for maximum filtration area and hydraulic throughput. When used as a polishing filter, generally a dry filter cake is not developed.

The filter press may also be used as a "polishing" filter to remove minute quantities of solids from an influent stream.