Each chamber is lined with a filter cloth to retain the solids. During the filling phase, free water is released and passes through the cloth. As the chamber fills with solids, pressure builds and the consolidation phase begins. During consolidation, terminal pressure is reached and filtrate flow rate declines. The plates are supported on a structural frame with a shifting mechanism to separate or accordion the plates one at a time.
Large presses have automatic plate shifting systems.
During filtration, the plates are squeezed by a hydraulic ram that seals the cloths on the plates and resists the filtration pressure developed by the filter feed pump. DryVac diaphragm plates can be inflated with steam. The internal plate pressure balloons the wall of the plate against the cake, releasing more free liquid from the space between the cake particles. Air can also be blown through the cakes to assist in removing more free liquid. Larger presses are usually mounted above a conveying system or containers that receive the finished product.