Subsea centrifugal compressor with horizontal shaft and with only one axial thrust bearing

Abstract

A centrifugal compressor unit including a motor having a rotor, at least one compressor having a shaft driven by the rotor; and a set of bladed wheels fitted on the driven shaft, the motor and the compressor being mounted in a common watertight casing. It further includes cooling means for cooling the motor, the cooling means having a gas cooler outside the casing. In operation, the motor, the compressor and the casing having the motor and the compressor are arranged horizontally, one axial thrust bearing only being provided on a compressor side.

What is claimed is: 
     
         1 . A subsea centrifugal compressor unit, comprising:
 a motor having a rotor,   at least one compressor having a shaft driven by the rotor; and   a set of bladed wheels fitted on the driven shaft,   the motor and the compressor being mounted in a common watertight casing, and further comprising cooling means for cooling the motor, the cooling means having a gas cooler outside the casing,   wherein, in operation, the motor, the compressor and the casing having the motor and the compressor are arranged horizontally, and in that it further comprises one axial thrust bearing only on a compressor side.   
     
     
         2 . The subsea centrifugal compressor unit according to  claim 1 , wherein the rotor and the driven shaft form one common shaft, the compressor unit having a set of three radial bearings for supporting the shaft, two bearings being provided on the motor side and one bearing being provided on the compressor side. 
     
     
         3 . The subsea centrifugal compressor unit according to  claim 1 , wherein the rotor and the driven shaft are connected by means of a flexible coupling that is tortionally flexible and axially unflexible, and further comprising a set of four radial bearings for supporting each end of the rotor and the driven shaft. 
     
     
         4 . The subsea centrifugal compressor unit according to  claim 2 , wherein the radial bearings for supporting the driven shaft or the rotor are magnetic bearings. 
     
     
         5 . The subsea centrifugal compressor unit according to  claim 1 , wherein the axial bearing is a magnetic bearing. 
     
     
         6 . The subsea centrifugal compressor unit according to  claim 1 , wherein the gas cooler is part of a closed loop extending partly outside the casing. 
     
     
         7 . The subsea centrifugal compressor unit according to  claim 1 , comprising a seal between the motor, downstream the cooling means, and the compressor. 
     
     
         8 . The subsea centrifugal compressor unit according to  claim 1 , wherein the casing is pressurized.