The main function of the hydraulic oil filter is to filter the hydraulic oil, and various impurities inevitably appear in the hydraulic system. The main sources are: mechanical impurities remaining in the hydraulic system after cleaning, such as rust, casting sand, welding slag, iron filings, paint, paint skin and cotton yarn scraps, etc., and impurities entering the hydraulic system from outside, such as through the oil filler and Dust entering the dust ring, etc.; impurities generated during the working process, such as the debris formed by the hydraulic action of the seal, the metal powder generated by the relative wear of the movement, the colloid, asphaltene, carbon residue, etc. generated by the oil due to oxidation and deterioration . After the above impurities are mixed into the hydraulic oil, with the circulation of the hydraulic oil, it will play a destructive role everywhere, seriously affecting the normal operation of the hydraulic system, such as making a small gap (in terms of) between the relatively moving parts in the hydraulic components and throttling. Small holes and gaps are stuck or blocked; destroy the oil film between the relatively moving parts, scratch the surface of the gap, increase internal leakage, reduce efficiency, increase heat, aggravate the chemical action of the oil, and make the oil deteriorate. According to production statistics, more than 75% of the failures in the hydraulic system are caused by impurities mixed in the hydraulic oil. Therefore, it is very important for the hydraulic system to maintain the cleanliness of the oil and prevent the pollution of the oil.