mounted as shown in an upper bearing 19 and a lower bearing 20 the motor 8 the gear 10 and the compressor housing with the rotor are arranged as shown within a common pressure shell 21 within this pressure shell there is a common gas atmosphere the so called the drive atmosphere seals 17 and 18 delimit a compressor process atmosphere from compressor housing 13 runs an open flow line connection 22 as shown into pipeline 1 which flows into the separator 39 s gas chamber 4 and supplies a well stream to the separator flow line 22 exits from the compressor housing 13 below a balance piston 23 for the compressor 39 s drive shaft flow line 22 thus runs from the compressor process atmosphere to the pipeline 1 for the well stream between flow line 22 and a lube oil sump 25 runs a gas line 24 with a built in throttle 33 the lube oil sump has as shown at 26 an open communication with the interior of pressure shell 21 and is therefore a part of the drive atmosphere the lube oil sump 25 is at the same time a part of the lube oil circuit which comprises a lube oil pump 27 a lube oil cooler 28 and a lube oil flow line 29 which goes to the respective bearings in the motor gear and compressor the lube oil flow line 29 is distributed as shown into branch pipes to the various bearings although in this case not to the.