Patent Application
20190186245
The present disclosure relates to an electrical submersible pump motor. More particularly, the disclosure relates to a lubricant circulating pump that forms a part of a radial bearing for the motor.
Electrical submersible pumps (ESP) are commonly used to pump well fluid from hydrocarbon producing wells. A typical ESP includes a motor that rotates a shaft to drive a pump. The motor is normally a three-phase electrical motor having a non-rotating stator that has a stator bore. The shaft extends through the stator bore and has rotor sections spaced apart from each other along the length of the shaft. The stator has windings that when powered will interact with the rotor sections to cause rotation of the shaft.
The motors can be 30 feet or more in length. Radial bearings are located in the spaces between the rotor sections to provide radial support for the shaft. The bearings are immersed in a dielectric lubricant in the stator bore for lubrication. The bearings may be of various types and normally include an inner sleeve keyed to the shaft for rotation and a bearing carrier with an outer diameter that fits closely in the stator bore. An anti-rotation member on the outer diameter of the bearing carrier engages the stator bore to prevent rotation of the bearing carrier.
These types of ESPs work well. However, the lubricant in the stator bore can stagnate at and around the radial bearings. Stagnation can cause the temperature of the bearings to rise significantly. The heating will cause the lubricant viscosity to decrease, resulting in localized heating and thermal expansion. The localized heating can accelerate bearing degradation and in severe cases, bearing and motor failure. The heating can cause the rotating sleeve to lock with the non-rotating bearing carrier. Various proposals have been made for lubricant pumps to enhance lubricant circulation in motors.
An electrical submersible pump assembly comprises a motor having a stator with a bore extending along a longitudinal axis. A shaft extends longitudinally through the bore. Rotor sections are mounted to the shaft for rotation in unison, the rotor sections being axially spaced apart from each other. At least one lubricant pump within the bore is mounted to the shaft for rotation therewith for circulating motor lubricant within the bore. A bearing carrier has an inner diameter in sliding engagement with an outer diameter of the lubricant pump. An anti-rotation member on an outer diameter of the bearing carrier is in engagement with the bore of the stator to prevent rotation of the bearing carrier.
The lubricant pump may have at least one curved blade. More particularly, the lubricant pump may have a plurality of curved blades spaced around the shaft, defining flow passages between the blades.
In the embodiment shown, the lubricant pump is located between adjacent ones of the rotor sections. The motor may have a plurality of lubricant pumps, each of the lubricant pumps being located in a space between adjacent rotor sections.
In the embodiment shown, the lubricant pump includes an inner sleeve mounted to the shaft for rotation in unison. An outer sleeve surrounds the inner sleeve, the outer sleeve having a greater inner diameter than an outer diameter of the inner sleeve, defining an annular space between. At least one curved blade is within the annular space and joined to the inner diameter of the outer sleeve and the outer diameter of the inner sleeve for rotation in unison with the inner sleeve and the outer sleeve. The inner sleeve, the outer sleeve, and the curved blade may be a monolithic single-piece member.
A port may extend from an inner diameter to the outer diameter of the lubricant pump to divert to the outer diameter of the lubricant pump a portion of the lubricant flowing through the lubricant pump.
The method and system of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments are shown. The method and system of the present disclosure may be in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey its scope to those skilled in the art. Like numbers refer to like elements throughout. In an embodiment, usage of the term “about” includes +/−5% of the cited magnitude. In an embodiment, usage of the term “substantially” includes +/−5% of the cited magnitude.
It is to be further understood that the scope of the present disclosure is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. In the drawings and specification, there have been disclosed illustrative embodiments and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation.
A seal section 23 connects to motor 21 and has features to reduce a pressure differential between a dielectric lubricant in motor 21 and the hydrostatic pressure of the well fluid. In this example, the pressure equalizing features of seal section 23 locate between motor 21 and pump intake 19, but the pressure equalizing components could be mounted to a lower end of motor 21. ESP 13 may also include other components, such as a gas separator (not shown) and another motor connected in tandem with motor 21. If a gas separator is employed, intake 19 would be at a lower end of the gas separator.
Although
Shaft 31 extends through a number of rotor sections 33, which connect to shaft 31 with a key and slot arrangement to cause shaft 31 to rotate in unison with rotor sections 33. Each rotor section 33 is made up of a large number of thin laminations or disks. Copper rods (not shown) are spaced around axis 32 parallel to axis 32. The copper rods extend through the laminations of each rotor section 33 to end rings 35 located at the upper and lower ends of each rotor section 33. Rotor sections 33 are axially spaced apart from each other. An electromagnetic field generated by supplying three-phase power to the windings of stator 27 causes rotor sections 33 to rotate shaft 31.
Motor 21 may be lengthy, such as 30 feet or more. A combined radial bearing and lubricant pump 37 locates in at least some of the spaces between adjacent rotor sections 33 provide radial stabilization for shaft 31. A dielectric lubricant fills stator bore 29 and immerses the combined radial bearings and lubricant pumps 37 for lubrication.
Referring also to
Referring also to
Inner sleeve 41, outer sleeve 45 and helical blades 49 may be integrally formed together as a monolithic single-piece rigid metal structure by additive manufacturing techniques. All of the radial bearings within motor 21 could include one of the screw pumps 40 or only some of them.
Referring to
In this example, carrier 53 is a single-piece member. Alternately, carrier 53 could include an insert sleeve between an inner portion of the carrier and the outer sleeve to attenuate vibration being transferred from shaft 31 through combined bearing and lubricant pump 37 to stator 27. Carrier 53 does not need any axial flow passages for lubricant flow because the lubricant flows through flow passages 50 of screw pump 40.
During operation, an electromagnetic interaction of rotor sections 33 with stator 27 causes shaft 31 to rotate. Screw pump 40 rotates with shaft 31, inducing the flow of lubricant from a lower to an upper side of combined bearing and lubricant pump 37, or vice-versa. The combined bearing and lubricant pump 37 provides radial stabilization of shaft 31 through the engagement of carrier 53 with stator bore 29 and the engagement of screw pump 40 with shaft 31. Screw pump 40 and bearing carrier 53 resist any radial movement of shaft 31 by transferring radial forces from shaft 31 to the side wall of stator bore 29. Outer sleeve 45 will perform like a standard bearing sleeve inside bearing carrier 53 with a lubricant wedge supporting it. Ports 51 divert a portion of the lubricant in some of the flow passages 50 to the dynamic interface between outer sleeve 45 and carrier 53. Differences in thermal growth may cause slight axial movement between shaft 31, screw pump 40 and carrier 53.
The circulation of lubricant by screw pump 40 mitigates the occurrence of stagnant lubricant around combined bearing and lubricant pump 37, which otherwise could undergo significant heating and thermal expansion. The present disclosure described herein, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned, as well as others inherent therein. While a presently preferred embodiment of the invention has been given for purposes of disclosure, numerous changes exist in the details of procedures for accomplishing the desired results. These and other similar modifications will readily suggest themselves to those skilled in the art, and are intended to be encompassed within the spirit of the present invention disclosed herein and the scope of the appended claims. For example, the screw pump could be another type, such as an impeller style. Further, instead of the screw pump being integrated into bearing sleeve, it could also be integrated into the rotor end rings.
This application claims priority to provisional application Ser. No. 62/608,043, filed Dec. 20, 2017.
| Number | Date | Country | |
|---|---|---|---|
| 62608043 | Dec 2017 | US |
