The oil which comes out of the expeller contains lot of foots, suspended practical’s of seed and cake. This oil requires filtration before it is stored in stored in storage tanks. This filtration takes place by pumping the oil to the filter press, where it passes through a layer of the filter cloth. The liquid oil passes through the filter cloth and solid matter deposits on the filter cloth.
There are two important types of filter presses, generally used in oil mill industry.

• Recessed plate or chamber types filter press.
• Plate and frame type filter press.
• Recessed Plate types Filter Press

This consists primarily of a series of cast iron plates. These plates are recessed and have a raised rim round the periphery of each face, so that when two plates are brought together the dis-hed centers from a chamber in between them. While the press is open a filter cloth is laid over each plate, hanging down on both sides and extending beyond the edges. Through the centre of each plate there is a circular feed hole and there are corres-ponding holes in the filter cloth. The filter clothes are secured round the central feed hole by special tightening nuts. When all the plates and clothes are assembles together and tightened, the cloth forms a tight joint between the mach-ined edges of the plate. The tightening of these plates is effected by means of rack and pinion arrangement. The pinion is rotated by means of a Tommy bar, inserted in the holes round its flange. The crude oil to be filtered is pumped into the press and while passing through the central feed holes, fills in all the cham-bers between the plates. The only outlet for the liquid are the pores of the clothes. The faces of the plates are cast with certain types of grooves so that while the cloth is supported, a series of intersecting chambers are formed over the whole surface, allowed the flow of oil without any hindrance. The oil trickles down into a gutter forms along the plates, just above the lower raised edge. Each plate then discharges through a plane spout or bob cock into a collection tray.

Plate and frame type filter press :

In this type of filter press the edge of the plates are all finely machined and are almost in level with the filtering surface. An independent frame is used between these plates to form a chamber. The plate and the frames are arranged alternatively and the filter cloth is simply hung over. The clothes are nipped between the edges of the plates and the frames when they are closed together The plates have special recess to form the fitting surface and for drainage. The filter oil is discharged by means of bib spout or cocks. This type of filter press has an advantage over recessed plate type filter press in capacity. These can hold more quantity of sediments, so more oil can be filtered at a time without opening the filter press.
The foots separated by the filter press are generally mixed with the oil seed fed to the expeller.