液压系统中液压油的水污染对油质的危害很大，它是造成油质氧化的主要原因之一。液压系统工作时油箱液面会随时发生变化，当液面下降时油箱外的空气被滤清器过滤后，进入吸湿器，吸湿器内干燥剂吸收空气中的水分，干燥后的空气推开进气单向阀进入油箱，同时油箱外大气关闭放气单向阀。当油箱内液面上升时油箱内的空气关闭进气单向阀同时打开放气单向阀直接排出大气。 The water pollution of oil running in the hydraulic system is a bad jeopardize to its quality that is the all-important cause of making the oil oxidation. As the hydraulic system works, the capacity of oil box will change at any moment. When the capacity decreases, the air will enter the moisture absorption after filtered. The desiccant in the absorption sorbs the moisture, then the desiccated air bursts through the entry single way valve and comes into the oil box, at the same time the atmosphere outside the oil box will close the deflated single way valve. When the capacity increases, the atmosphere inside the oil box closes the entry single way valve simultaneously opening the deflated single way valve where atmosphere is directly expelled.