UNITED OSD, with the ability of the production of 40m3/min-80m3/min screw type air compressor manufacture, is one of the few air compressor manufacturing enterprises which can provide water cooling, air cooling and high voltage in the industry. The large diameter rotor is used and it operates at a lower speed. The operating noise of the unit is reduced and the numbers of parts are decreased but using the integrated structure to increase the reliability and reduce the maintenance cost.