Abstract: A single screw, gate rotor machine in which compressible fluid is fed to the machine through a low pressure inlet and exhausts through a higher pressure outlet, in which an unloading valve is provided in the casing adjacent to the high pressure side of the gate rotor, or each gate rotor where there are two gate rotors.

Abstract: In a gas compression system employing a positive-displacement rotary compressor, liquid is injected into the compressor which is the liquid phase of the gas or vapour being compressed and the compressor temperatures are maintained at about the saturation temperatures of the gas or vapour. The quantity of liquid injected is sufficient to fill, at least partially, the internal compressor clearance gaps. An electric driving motor is contained with the compressor in another chamber of the same of casing and the motor windings are cooled by being bathed in the wet gas mixture leaving the compressor discharge.