Vacuum Filter was one of the first products of oil filtration systems. These systems are of the precoat type. Therefore, a filtering aid layer, wood flour or other filtering material is used as a filtering medium, which is applied on a special cloth mounted on a rotating support called the drum. The depression between the upstream and downstream of the drum keeps the pre-stress on the canvas and makes the suction of the oil to be filtered.
By passing the product through the precoat the dirt is retained by the coating while the oil passes through the porosity thereof. A steel blade cuts a pin at every turn of the drum, dropping the dehydrated dirt and cleans the filtering surface clean. This is a product version of a higher filtration yield. An insulation of the machine is also provided to keep the oil temperature constant.