A multistage geared multishaft turbo compressor, comprising:
- a central transmission housing, including a central gear bearing set, a first bearing set and an additional bearing set;
- drive means including a central gear supported by said central gear bearing set and a drive for driving said central gear;
- a first pinion shaft with a pinion engaged with said central gear, said first pinion shaft being supported by said first bearing set, said first pinion shaft extending out of said transmission housing on each side of said transmission housing to provide a first pinion shaft end at one side of said transmission housing and a second pinion shaft end at another side of said transmission housing, said first pinion shaft being unsupported between said first end of said first pinion shaft and said first bearing set and said first pinion shaft being unsupported between said second end of said first pinion shaft and said bearing set to provide an overhung first pinion shaft first end and to provide an overhung first pinion shaft second end;
- a first low pressure stage including a volute housing with an axially extending intake at an end of said first pinion shaft, a first stage individual impeller, said first stage individual impeller being connected to one end of said first pinion shaft;
- a second low pressure stage including a volute housing and a second stage individual impeller, said second stage individual impeller being connected to another end of said first pinion shaft;
- an additional pinion shaft extending parallel to said first pinion shaft with a pinion engaged with said central gear, said additional pinion shaft being supported by said additional bearing set, said additional pinion shaft extending out of said transmission housing on each side of said transmission housing to provide a first additional pinion shaft end at one side of said transmission housing and a second additional pinion shaft end at another side of said transmission housing, said additional pinion shaft being unsupported between said first end of said additional pinion shaft and said first bearing set and said additional pinion shaft being unsupported between said second end of said additional pinion shaft and said bearing set to provide an overhung additional pinion shaft first end and to provide an overhung additional pinion shaft second end;
- a high pressure stage group including a high pressure stage first impeller and a high pressure stage second impeller, said high pressure stage first impeller and said high pressure stage second impeller being disposed adjacent to each other, arranged one behind the other, at said first additional pinion shaft end;
- a high pressure stage housing including means defining an axial intake for said high pressure stage first impeller and means defining an outlet adjacent said high pressure stage first impeller, a disk diffuser connected to said outlet and a return ring connecting said disk-shaped diffuser to an inlet adjacent said high pressure stage impeller, said high pressure stage housing having no bearings for supporting said first impeller and said second impeller, said high pressure stage housing being flangedly connected to said transmission housing, said high pressure stage housing defining a direction of flow from said one end of said additional pinion shaft toward said transmission housing.