Gas compressor

A vertical axis gas compressor comprises a rotor arrangement which includes a vertical axis shaft 1 with an impeller 5 and bearing 3 mounted thereto, the compressor further comprising a stationary bearing arrangement 10 having a seat, the rotor arrangement being axially insertable into the compressor as an integral unit so as to seat the rotor bearing 3 onto the stationary bearing seat. The rotor may include an armature winding 2 of an electric motor mounted on the shaft 1. The rotor and stator bearings 3, 10 may have complimentary conical surfaces and may be separated by gas supplied by the compressor.