In pneumatic technology, air filter, reducing valve and oil mist called pneumatic three large pieces. In order to obtain multiple functions, these three air source processing elements are usually assembled together in order, which is called pneumatic triplet. For air source purification, filtration, pressure reduction and lubrication. The installation sequence of the three large pieces is air filter, pressure reducing valve and oil mist device according to the air inlet direction. Three parts is an indispensable air source device in most pneumatic systems, installed near the gas equipment, is the final guarantee of compressed air quality, its design and installation, in addition to ensure the three parts of their own quality, but also consider saving space, easy installation, can be arbitrarily combined and other factors. From import flow of compressed air, a guide plate was introduced, on the guide plate has a uniform distribution of similar fan blade helical, forcing high-speed flow of compressed air along the tangent direction of the tooth to the rotation of the strong, mixed liquid water in the air, oil, and the larger impurities in powerful under the action of centrifugal force, to the glass on the inner wall of the flow to the bottom of the cup. The compressed air that removes liquid water and oil and the larger impurities is further filtered through the filter core to remove the tiny solid particles, and then the clean compressed air is exported from the outlet. Umbrella water baffle plate will be divided into two parts, the lower part of the pressure to maintain the static zone, can prevent the high-speed rotation of the air sucked up the bottom of the cup of water and oil. The water and oil gathered at the bottom of the cup is drained from the drain valve and the air filter must be installed vertically down the cup.