Method for filtering and purifying hydraulic oil

A method for filtering and purifying hydraulic oil comprises the steps of (1) using an electrical heating system for heating oil to 60 DEG C; (2) performing primary filtering through a first filtering device which comprises novel high-gradient electromagnetic filters connected in parallel so as to filter ferromagnetic corrosion products in the oil and macromolecules generated by oxidation during usage of the hydraulic oil; (3) performing secondary filtering through a second filtering device to remove large solid particles; (4) subjecting the oil to tertiary filtering through a third filtering device which comprises common parallelly-connected filters high in filtering accuracy to form redundancies; (5) opening exhaust valves which are mounted after filtering of all stages to remove gas impurities in the oil and bubbles generated during filtering; (6) removing moisture in the oil through an oil-water separation system; (7) monitoring the oil cleanliness class in real time through a contamination particle counter, and closing a solenoid valve of an oil return pipe when the purification class requirement is reached.