XL-BY board-frame pressure oil filter mainly uses the lining filter paper (or filter cloth) between the filter frame and the filter board as a filtration medium, filtering impurities in oil. Meanwhile, using the water-absorption of filter paper can also filter part of moisture out of oil. Since the replacement of filter paper and stuffing are very convenient, this machine is particularly applicable to the various poor transformer oils, turbine oils, aviation hydraulic oils and other lubricants for pre-processing.