Axial bearing offloading in fluid processing machines

Abstract

The axial reaction force generated by a subsea pump or compressor is partially counteracted by a pressure differential in a barrier fluid across a thrust element. The pressure differential is created using impellers or other structures on the thrust element that increases the barrier fluid pressure on one side of the thrust element when the main shaft of the pump or compressor is rotated. The pressure differential across the thrust element partially offloads the bearing surface of the thrust element.

What is claimed is: 
     
         1 . A fluid pressure increasing machine, comprising:
 a fluid processing chamber configured to contain a process fluid and including an inlet and an outlet;   a first member rotatable about a central longitudinal axis;   a motor system mechanically engaged to the first member so as to rotate the member about the longitudinal axis in a rotation direction;   a plurality of impellers being fixedly mounted to the first member and exposed to the process fluid within the fluid processing chamber such that when the first member is rotated in the rotation direction the impellers act on the process fluid thereby increasing pressure of the process fluid towards the outlet and a reaction force is imparted on the first member in an axial direction from the outlet toward the inlet; and   a first rotating element surrounded by a barrier fluid and fixedly attached to the first member, the rotating element having a higher pressure surface exposed to the barrier fluid at a higher pressure and a lower pressure surface exposed to the barrier fluid at a lower pressure, the difference between the higher and lower pressures acting on the respective higher and lower pressure surfaces generating a force on the first member that at least partially counteracts the reaction force.   
     
     
         2 . The fluid processing machine of  claim 1  wherein the difference between the higher and lower pressure is at least partially caused by structures on the first member configured to increase the barrier fluid pressure when rotating the first member. 
     
     
         3 . The fluid processing machine of  claim 2  wherein the structures include a plurality of impellers mounted on said first member. 
     
     
         4 . The fluid processing machine of  claim 2  wherein the structures are of a type selected from a group consisting of impellers, vanes, pump rings, labyrinths and grooves. 
     
     
         5 . The fluid processing machine of  claim 1  wherein the difference between the higher and lower pressures of barrier fluid is at least 10 bars. 
     
     
         6 . The fluid processing machine of  claim 1  wherein the generated force on the first member counteracts at least 25% of the reaction force. 
     
     
         7 . The fluid processing machine of  claim 1  wherein the first member is a thrust member having a bearing surface configured to bear the reaction force that is not counteracted by said force generated by the difference between the higher and lower pressures of the barrier fluid. 
     
     
         8 . The fluid processing machine of  claim 1  wherein the machine is a subsea compressor. 
     
     
         9 . The fluid processing machine of  claim 8  wherein the machine is subsea wet gas compressor, and the process fluid is a wet hydrocarbon gas being produced from a subterranean rock formation. 
     
     
         10 . The fluid processing machine of  claim 1  wherein the machine is a multiphase pump configured to be deployed in a subsea environment and the process fluid contains multiple phases. 
     
     
         11 . The fluid processing machine of  claim 10  wherein the multiple phases include solid particles and/or hydrates. 
     
     
         12 . The fluid processing machine of  claim 1  wherein the machine is an electrical submersible pump deployable within a wellbore. 
     
     
         13 . The fluid processing machine of  claim 1  wherein the first member includes a hub on which the plurality of impellers are mounted in a plurality of rows, and the machine further comprising:
 a second member rotatable about the central longitudinal axis, the second member including a sleeve; 
 a second motor system mechanically engaged to the second member so as to rotate the second member about the longitudinal axis in a second rotation direction which is opposite to the rotation direction of the first member; and 
 a plurality of second impellers being fixedly mounted to the sleeve of the second member in a plurality of second rows such that the second rows interleave with the rows of impellers on the hub of the first member, the second impellers being exposed to the process fluid within the fluid processing chamber such that when the second member is rotated in the second rotation direction the second impellers act on the process fluid thereby increasing pressure of the process fluid towards the outlet and a second reaction force is imparted on the second member in an axial direction from the outlet toward the inlet; and 
 a second rotating element surrounded by the barrier fluid and fixedly attached to the second member, the rotating element having a higher pressure surface exposed to the barrier fluid at a higher pressure and a lower pressure surface exposed to the barrier fluid at a lower pressure, the difference between the higher and lower pressure acting on the respective higher and lower pressure surfaces generating a force on the second member that at least partially counteracts the second reaction force. 
 
     
     
         14 . The fluid processing machine of  claim 1  wherein the difference between the higher and lower pressures fluid is at least partially caused by a barrier fluid pump. 
     
     
         15 . The fluid processing machine of  claim 14  wherein the barrier fluid pump includes a plurality of impellers fixedly attached to the first member. 
     
     
         16 . The fluid processing machine of  claim 14  wherein the barrier fluid pump is powered by a second motor. 
     
     
         17 . The fluid processing machine of  claim 1  wherein the barrier fluid is less wear-inducing than the processing fluid. 
     
     
         18 . A method of increasing pressure of a process fluid comprising rotating with a motor system a first member including a shaft and a hub about a central longitudinal axis so as to cause a plurality of impellers mounted to the hub to engage and increase fluid pressure of the process fluid along a first axial direction thereby causing a reaction force to be imparted on the hub and shaft in a second axial direction opposite to the first axial direction, the first member also including a first rotating element surrounded by a barrier fluid and having a lower bearing surface that bears a part of the reaction force, the first rotating element also having structures that increase barrier fluid pressure by rotating the first member thereby causing a pressure differential in the barrier fluid wherein a higher pressure surface of the first rotating element is exposed to a higher pressure barrier fluid and a lower pressure surface of the first rotating element is exposed to a lower pressure barrier fluid, the pressure differential in the barrier fluid acting on the respective higher and lower pressure surfaces generating a force on the first rotating element that partially counteracts the reaction force and off-loads the lower bearing surface. 
     
     
         19 . The method of  claim 18  wherein the structures include a plurality of impellers mounted to an outer edge of the first rotating element. 
     
     
         20 . The method of  claim 18  wherein the process fluid is a hydrocarbon effluent and is produced from a subterranean rock formation. 
     
     
         21 . The method according to  claim 18  wherein the first rotating element is a thrust disk. 
     
     
         22 . The method according to  claim 18  wherein the method is carried out in a subsea environment.