Method and apparatus for lubricating a screw pump system

Abstract

A pump system includes inlet chambers, an outlet chamber, and rotors disposed inside the inlet chambers and the outlet chamber to pump a process fluid from the inlet chambers to the outlet chamber and to direct the process fluid to a separator. A gear chamber is configured to receive a portion of the process fluid from the separator. First and second sets of pump bearings are coupled to the rotors and lubricated by the portion of the process fluid flowing from the gear chamber. A conduit is configured to direct the portion of the process fluid from the pump bearings back to the gear chamber. Some of the portion of the process fluid lubricating the pump bearings is permitted to leak to the inlet chambers. Additional process fluid is continually added to the portion of the process fluid to compensate for fluid leaking to the inlet chambers.

1 . A method for operating a pump system, comprising:
 directing a process fluid into an inlet chamber of a pump casing at a first pressure;   rotating a plurality of rotors disposed inside the pump casing to pump the process fluid from the inlet chamber to an outlet chamber of the pump casing at a second pressure;   directing the process fluid from the outlet chamber to a separator;   directing a first portion of the process fluid from the separator downstream;   directing a second portion of the process fluid from the separator to a gear chamber of the pump at a third pressure;   directing the second portion of the process fluid to lubricate a first set of pump bearings;   directing the second portion of the process fluid to lubricate a second set of pump bearings; and   joining a flow from the second set of pump bearings to a flow of the second portion of the process fluid prior to directing a combined flow into the gear chamber.   
     
     
         2 . The method of  claim 1 , wherein a plurality of gears in the gear chamber are each coupled to an end of each of the plurality of rotors. 
     
     
         3 . The method of  claim 1 , wherein the second pressure is greater than the first pressure. 
     
     
         4 . The method of  claim 3 , wherein the third pressure is greater than the first pressure and the second pressure is greater than the third pressure. 
     
     
         5 . The method of  claim 1 , comprising leaking a portion of the process fluid from the first pump bearing to a first inlet chamber and leaking a portion of the process fluid from the second pump bearing to a second inlet chamber. 
     
     
         6 . The method of  claim 5 , wherein directing a second portion of the process fluid from the separator to a gear chamber of the pump at a third pressure comprises directing about 15% of a total flow of process fluid from the separator to a pressure reducer prior to joining the flow from the second set of pump bearings to compensate for the leaking of process fluid from the first and second pump bearings. 
     
     
         7 . The method of  claim 1 , wherein directing a first portion of the process fluid from the separator downstream comprises directing about 80% to 90% of a total flow of process fluid from the separator to a downstream unit. 
     
     
         8 . The method of  claim 1 , wherein the separator separates particulate matter from the process fluid, and wherein process fluid having reduced particulate matter content comprises the second portion of process fluid directed to the gear chamber. 
     
     
         9 . A method for operating a pump system, comprising:
 pumping a fluid from a pump inlet to a pump outlet;   separating a lubricating portion of fluid flow from the pump outlet; and   pumping the lubricating portion of fluid flow through a circulation path that includes a gear pump coupled to rotors of the pump, a first pump bearing and a second pump bearing.   
     
     
         10 . The method of  claim 9 , comprising allowing an amount of the lubricating portion to flow from the first and second pump bearings into an inlet side of the pump; and adding fluid to the lubricating portion circulating through the circulation path to compensate for the amount of the lubricating portion flowing from the pump bearings into the inlet side of the pump. 
     
     
         11 . A pump system, comprising:
 inlet chambers;   an outlet chamber;   rotors disposed inside the inlet chambers and the outlet chamber to pump a process fluid from the inlet chambers to the outlet chamber and to direct the process fluid to a separator;   a gear chamber configured to receive a portion of the process fluid from the separator;   first and second sets of pump bearings coupled to the rotors and lubricated by the portion of the process fluid flowing from the gear chamber; and   a conduit configured to direct the portion of the process fluid from the pump bearings back to the gear chamber;   wherein some of the portion of the process fluid lubricating the pump bearings is permitted to leak to the inlet chambers, and wherein additional process fluid is continually added to the portion of the process fluid to compensate for fluid leaking to the inlet chambers.   
     
     
         12 . The system of  claim 11 , wherein an outlet chamber pressure is greater than an inlet chamber pressure, and wherein pressures in the pump bearings are greater than the inlet chamber pressure. 
     
     
         13 . The system of  claim 11 , comprising gears in the gear chamber, wherein each gear is coupled to a respective end of a rotor and the gears are configured to circulate the process fluid as a lubricant through the pump bearings. 
     
     
         14 . The system of  claim 11 , wherein a pump bearing is coupled to each end of each of the rotors. 
     
     
         15 . The system of  claim 11 , wherein the portion of the process fluid from the separator directed to the gear chamber comprises about 10% to 20% of a total flow of process fluid from the separator. 
     
     
         16 . The system of  claim 11 , comprising a pressure reducer that receives the process fluid from the separator and directs the process fluid to the gear chamber to compensate for the process fluid leaking to the inlet chambers. 
     
     
         17 . The system of  claim 11 , wherein the separator separates particulate matter from the process fluid, and wherein process fluid having reduced particulate matter content is directed to the gear chamber. 
     
     
         18 . A pump system, comprising:
 inlet chambers;   an outlet chamber;   rotors disposed inside the inlet chambers and the outlet chamber and configured to mesh with one another to direct a multiphase process fluid from the inlet chambers to the outlet chamber; and   an inlet disposed adjacent to the inlet chambers and configured to direct the multiphase process fluid generally tangentially into the inlet chamber and to swirl the multiphase process fluid to reduce a settling of particulate matter from the multiphase process fluid in the inlet chambers.   
     
     
         19 . The system of  claim 18 , comprising a gear chamber configured to receive a portion of the multiphase process fluid from the outlet chamber after a separating of the multiphase process fluid by a separator. 
     
     
         20 . The system of  claim 19 , wherein a separated multiphase process fluid is received by the gear chamber and is pumped by gears in the gear chamber to lubricate pump bearings. 
     
     
         21 . The system of  claim 19 , comprising pump bearings configured to receive a portion of a separated multiphase process fluid from the gear chamber, wherein some of the portion of the separated multiphase process fluid from the pump bearings is configured to leak to the inlet chambers.