Patent ID: 8435020
Filing Date: 2013-05-07
Classification: F01C,F04C

Abstract:
1. An oil-free screw compressor comprising: a compressor main unit having a pair of male and female screw rotors that are disposed horizontally, with shafts of the screw rotors being supported by bearings; an oil supply tank that stores oil; an oil supply line that supplies the oil in the oil supply tank to oil injection portions including the bearings of the compressor main unit; and an oil recovery line that collects the oil supplied to the oil injection portions to the oil supply tank, wherein the screw compressor further comprises: shaft-sealing portions that are placed on two sides of a compressor chamber of the screw rotor in an axial direction thereof, and prevent the oil supplied to the oil injection portions from being mixed into the compressor chamber of the screw rotor, as well as preventing a process gas from leaking from the compressor chamber; a suction port return line that allows the shaft-sealing portion on a discharge side of the compressor chamber and a suction port of the compressor main unit to communicate with each other; a supply process gas communication line that allows the suction port of the compressor main unit and an upper portion of the oil supply tank to communicate with each other; and an inside/outside shaft-sealing portion that separates an inside of the compressor main unit from atmospheric air.