The breather valve is installed above the hydraulic oil tank. It is mainly used to balance the air pressure inside and outside the hydraulic oil tank during the output and inflow of hydraulic oil from the oil tank. At the same time, the breather valve also has the function of filtering the dust and other impurities in the atmosphere to ensure that the cleanliness of the hydraulic oil is not polluted by external dust. Because the breather valve is equipped with a special breather valve filter element. The filter element of the breather valve can filter the air entering the hydraulic oil tank. Prevent dust from entering the fuel tank. This will prevent the hydraulic oil from deteriorating. If the oil tank is sealed without the breathing filter element or the breathing filter element is blocked, the normal operation of the hydraulic system will be affected.