Patent Application
20090035159
This invention relates in general to centrifugal pumps and in particular to a thrust bearing and intake chamber for a surface mounted centrifugal pump.
Electrical submersible pumps are commonly used in oil wells for pumping large volumes of fluids. The pump is centrifugal, having a large number of stages of impellers and diffusers. An electrical motor is attached to the pump for driving the pump.
This type of pump is also used for various surface applications, such as for injecting a fluid into the well. In the surface application, the pump is mounted on a skid. An intake chamber is mounted to the intake end of the pump. A thrust chamber having a thrust bearing located therein is mounted to the intake chamber. The electrical motor is mounted to the skid independently of the pump. The shaft of the electrical motor couples to the shaft extending through the thrust chamber.
The typical prior art surface pumps of this type utilize a thrust chamber that is filled with a clean lubricating oil for lubricating the thrust bearing. The working fluid being pumped, typically water, does not enter the thrust portion of the thrust chamber containing the lubricant. While this type of pump works well, the seal between the lubricant and the working fluid in the intake chamber must be replaced from time to time due to wear. This can be a difficult task because it requires removal of the entire thrust bearing assembly from the pump assembly. During removal time, the pump will be shut down and cannot be operated.
U.S. Pat. No. 5,957,656 discloses a surface mounted pump with a thrust chamber that utilizes a filtered portion of the working fluid for lubricating the bearings, rather than a clean lubricant. The thrust chamber mounts to the intake chamber. A line extends from the working fluid intake extends to a separator or filter, and from there to a small pump stage for pumping filtered fluid through the thrust chamber bearings. The filtered fluid then re-enters the intake chamber.
In this invention, the thrust chamber connects directly to the housing of the pump. The working fluid intake is mounted to a sidewall of the thrust chamber, rather than to a separate intake chamber. The fluid flows into the thrust chamber and from there into the pump. The fluid also lubricates the thrust bearings. In the preferred embodiment, the fluid is not filtered prior to passing through the thrust bearings. Also, the flow path through the thrust bearings is arranged so that no pump stage is needed to pump the fluid through the thrust bearing.
Referring to
A thrust chamber 19 is mounted on skid 11 at the end opposite discharge 17. Thrust chamber 19 has a thrust bearing assembly 20 (
Referring to
Intake 21 comprises a tubular member 37 that extends outward from sidewall 35 relative to a longitudinal axis of shaft 23. Tubular member 37 has a connector on its outer end for connecting to a flowline. In this embodiment, the connector comprises a flange 39 for bolting to a flowline. Other types of connectors are feasible. In this example, an axis of intake 21 intersects the longitudinal axis of shaft 23 at 90 degrees, thus comprises a radial line of the axis of shaft 23; however the angle of intersection may vary. Also, the axis of intake 21 intersects a mid-center portion of thrust hearing 20 in this embodiment, thus intake 21 is located radially outward from thrust bearing 20.
A base portion 41 of the housing of pump 15 bolts directly to thrust chamber 19. Pump base 41 is illustrated as bolting to an adapter 43, which in turn bolts to an end plate 45 of thrust chamber 19. Other arrangements for connecting the housing of pump 15 to thrust chamber 19 are feasible. For example, end plate 45 and adapter 43 may be eliminated in some circumstances.
Pump end member 29 has an axial passage 47 extending through it through which shaft 23 passes. Axial passage 47 includes mating axial passages in end plate 45, adapter 43 and pump base 41. Axial passage 47 is larger in diameter than the outer diameter of shaft 23, providing an annular inlet 42 for pump 15. A coupling 49 is shown connecting the splines of chamber shaft 23 to pump shaft 51 for rotating pump shaft 51.
Motor end member 31 also has an axial passage 53 extending through it that is coaxial with passage 47. Axial passage 53 has a seal 55 on its motor end for sealing around shaft 23. Seal 55 is shown schematically and may be a variety of types. Preferably it would be a type having a rotating component that rotates against a stationary base, the rotating component being urged by a coil spring against the stationary base. Radial bearings or bushings 56, 57 are located within axial passages 47, 53, respectively, for providing radial support for chamber shaft 23.
Each end member 29 and 31 has an end face 59, the end faces 59 being opposed to each other and spaced apart from each other along the axis of shaft 23. A thrust bearing stationary base 61 is affixed to end face 59 of motor end member 31 for absorbing thrust passing in a direction from pump 15 toward thrust chamber 19. Pump 15 in some circumstances may exert thrust in the opposite direction. Preferably to accommodate this type of thrust, a stationary thrust bearing face 63 is affixed to end face 59 on pump end member 29. Thrust bearing 20 also has a thrust runner 65 that is secured to shaft 23 for rotational as well as axial movement. Thrust runner 65 is sandwiched between stationary bases 61 and 63 to transfer thrust imposed on shaft 23 to one of the bases 61 or 63. Thrust runner 65 preferably has a plurality of ports 67 extending from its motor side to its pump side for allowing fluid flow between axial passage 53 and axial passage 47 to lubricate thrust bearing 20.
Each end member 29, 31 of thrust chamber 19 has an outer portion 69 that is surrounded by sidewall 35. In this example, outer portion 69 is conical, tapering to a smaller diameter at thrust bearing 20. Other configurations are feasible. An annular clearance 70 is defined between outer portions 69 and sidewall 35.
At least one, and preferably several, pump end member ports 71 extend from outer portion 69 of pump end member 29 to passage 47. Ports 71 are inclined slightly toward pump 15 rather than being straight radial passages in this embodiment. Ports 71 provide a flow path from intake 21 through clearance 70 and axial passage 47 to pump inlet 42.
A plurality of motor end ports 73 extend from outer portion 69 of motor end member 31 inwardly to axial passage 53. Ports 73 also may incline toward pump 15 as illustrated, although other arrangements are feasible. Ports 73 provide a flow path for some of the fluid flowing through intake 21 and clearance 70 to axial passage 53 and ports 67. Bushing 56 does not seal nor significantly impede the flow of fluid flowing through thrust bearing 20 toward pump inlet 42. Ports 75 may be located in bushing 56 to assure that the flow of fluid through thrust bearing 20 is not impeded by bushing 56. In addition, ports may be located in bushing 57 to communicate the working fluid in passage 53 with seal 55.
In operation, when motor 27 (
The invention has significant advantages. Locating the intake in a side of the thrust chamber, rather than in a separate chamber, eliminates the need for a shaft seal sealing between the working fluid and lubricant in the thrust chamber. The fluid being pumped will provide cooling and lubrication of the thrust bearings without creating excessive wear. With thrust bearings as shown, the fluid does not need to be filtered before it passes through the thrust bearing. The incoming fluid directly impinges on the exterior of the thrust bearing and needs no supplemental pump stage to deliver the fluid through the thrust bearing.
While the invention has been shown in only one of its forms, it should be apparent to those skilled in the art that it is not so limited but is susceptible to various changes without departing from the scope of the invention.
