A connection between cake thickness hc, filtrate volume V and filter area A can be derived out of a mass balance of the filter cake and the filtrate, aside from this being dependent on the porosity ε and the densities of the solids and the liquid:
Old design of leaf filters (1905), employed for fine filtration (fine filter) and usually works with overpressure. The Kelly filter possesses vertical, rectangular filter blades, which are installed in sequence in a lying pressure tank. For the filtration it will be filled entirely with the suspension to be separated. The filtrate discharge is performed for each filter element through the lid. After the ending of the filter process the filter container is pulled away from the plate package, which is to be cleaned. The overpressure in Kelly filters lies usually at several bars. At difficult to filter suspensions one can work with filter aids.