CENTERING COUPLING FOR ELECTRICAL SUBMERSIBLE PUMP SPLINED SHAFTS

Abstract

An electrical submersible well pump assembly having a pump, a pump motor, and a seal section. The motor drives the pump via shafts rotatingly coupled with a coupling assembly. The coupling assembly maintains the shaft ends in coaxial alignment with an alignment device. The alignment device is profiled on opposite ends for mating engagement with the centering profiles on the shaft ends.

Description

FIELD OF THE INVENTION

This invention relates in general to electrical submersible well pumps, and in particular to couplings between splined shafts of an electrical submersible pump.

BACKGROUND OF THE INVENTION

Electrical submersible pumps (ESP) are commonly used for hydrocarbon well production, FIG. 1 provides an example of a submersible pumping system 10 disposed within a wellbore 5. The wellbore 5 is lined with casing 4 and extends into a subterranean formation 6. Perforations 9 extend from within the wellbore 5 through the casing 4 into the formation 6. Hydrocarbon fluid flow, illustrated by the arrows A, exits the perforations 9 into the wellbore 5, where it can either be pumped by the system 10 or migrate to a wellhead 12 disposed on top of the wellbore 5. The wellhead 12 regulates and distributes the hydrocarbon fluid for processing or refining through an associated production line 7.

The pumping system 10 includes an electrical submersible pump (ESP) 14 with production tubing 24 attached to its upper end. The ESP 14 comprises a motor 16, an equalizer or seal 18, a separator 20, and a pump 22. A fluid inlet 26 is formed in the housing in the region of the ESP 14 proximate to the separator section 20. The fluid inlet 26 provides a passage for the produced hydrocarbons within the wellbore 5 to enter the ESP 14 and flow to the pump 22. Fluid pressurized by the pump 22 is conveyed through the production tubing 24 connecting the ESP 14 discharge to the wellhead 12. The pump 22 and separator 20 are powered by the motor 16 via a shaft (not shown) that extends from the motor 16. The shaft is typically coupled to respective shafts in each of the pump 22, separator 20, and seal 14.

Delivering the rotational torque generated by an ESP motor 16 typically involves coupling a motor shaft (i.e., a shaft connected to a motor or power source) to one end of a driven shaft, wherein the other end of the driven shaft is connected to and drives rotating machinery. Examples of rotating machinery include a pump, a separator, and tandem pumps. One type of coupling comprises adding splines on the respective ends of the shafts being coupled and inserting an annular collar over the splined ends, where the annular collar includes corresponding splines on its inner surface. The rotational force is well distributed over the splines, thereby reducing some problems of stress concentrations that may occur with keys, pins, or set screws. Examples of a spline cross-section include an involute and a square tooth. Typically, splines having an involute cross-section are smaller than square tooth splines thereby leaving more of the functional shaft diameter of a shaft to carry a rotational torque load. Additionally, involute spline shapes force the female spline to center its profile on the male spline, thus coaxially aligning the shafts in the coupling with limited vibration. Square tooth splines are made without specialized cutters on an ordinary mill. However square teeth spline couplings do not align like involute teeth unless the clearance is reduced or the male and female fittings are forced together. However, reducing clearance or force fitting square teeth splines prevents ready assembly or disassembly.

SUMMARY OF THE INVENTION

Disclosed herein is a submersible pumping system for pumping wellbore fluid, comprising, a pump motor, a seal section, a motor shaft having an end rotatably affixed within an end of a shaft coupling, the motor shaft rotatable by the motor, a driven shaft having an end rotatably affixed within an end of the shaft coupling opposite to the motor shaft, the respective ends of the motor shaft and driven shaft being substantially coaxial within the shaft coupling, and an alignment element provided in the shaft coupling, the element coaxially engaging the respective terminal ends of the motor shaft and driven shaft within the shaft coupling. Optionally, the alignment element may be disposed on a shaft end. A first centering guide may be included on one side of the alignment element and a second centering guide on the alignment element opposite side, the first centering guide being substantially coaxial with the second centering guide. The first and second centering guides may be one of a protrusion on a side of the alignment element or a recess bored in the alignment element. A motor shaft tip alignment member may be included on the end of the motor shaft within the coupling and a driven shaft tip alignment member provided on the end of the driven shaft within the coupling. The tip alignment members may be a protrusion on the end of a shaft or a recess bored into the shaft. Square tooth splines may be formed on the motor shaft and driven shaft respective ends. An axial bore can be formed through the coupling where square tooth splines are formed on the bore inner diameter. In one embodiment, the driven shaft drives rotating machinery, where the machinery may be a pump, a tandem pump, and a separator. A resilient member may be included with the alignment element. The resilient member can be used to align the shafts with an opposing force in the absence of a shaft thrust load.

Also disclosed herein is a method of using an electrical submersible pump (ESP) in a wellbore involving providing the ESP in the wellbore. The ESP may include a motor, a motor shaft rotatingly affixed to the motor; a rotating device, a driven shaft rotatingly affixed to the rotating device, and a coupling rotatingly affixing ends of the motor shaft and driven shaft. The method may further include energizing the motor thereby rotating the motor shaft, the coupling, and the driven shaft. Additionally, the present method includes substantially coaxially aligning the ends of the motor shaft and driven shaft during shaft rotation. The method optionally further comprises providing an alignment element in the coupling between the shaft ends, and coaxially mating the shaft ends with the alignment element. A resilient member may be includable with the alignment element. The shaft ends can be profiled for coaxial alignment. The shaft end profile might include a protrusion or a recess bored into the shaft end. The method can also include profiling a side of the alignment element to align with the shaft ends. Profiling can involve forming a protrusion on a side of the alignment element and forming a recess bored into a surface of the alignment element.

The present disclosure also includes an electrical submersible pump (ESP) comprising a pump motor, a motor shaft mechanically affixed to the pump motor, a seal portion, a pump, a pump shaft mechanically affixed to the pump, a connector assembly rotatingly coupling respective terminal ends of the motor shaft and the pump shaft, and an aligning pin in the connector assembly axially engaged on one end with a terminal end of the pump shaft and axially engaged on another end with a terminal end of the motor shaft, wherein the pump shaft, motor shaft, and aligning pin axes are substantially aligned. A profile can be included on the aligning pin configured to engage the shaft ends, wherein the profile may be a protrusion or a recess. A resilient member may be included with the aligning pin.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a prior art submersible electrical pumping system in a wellbore.

FIG. 2a is an exploded view of a shaft coupling for use with the system of FIG. 1.

FIG. 2b is an assembled view of the shaft coupling of FIG. 2a.

FIG. 3a is an exploded view of an alternative shaft coupling for use with the system of FIG. 1.

FIG. 3b is an assembled view of the shaft coupling of FIG. 3a.

FIG. 4a is an exploded view of an alternative shaft coupling for use with the system of FIG. 1.

FIG. 4b is an assembled view of the shaft coupling of FIG. 4a.

FIG. 5 is a side partial cut-away view of an alternative shaft coupling for use with the system of FIG. 1.

FIG. 6 is a side partial cut-away view of an alternative shaft coupling for use with the system of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments of the invention are shown. This invention may, however, be embodied 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 the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. For the convenience in referring to the accompanying figures, directional terms are used for reference and illustration only. For example, the directional terms such as “upper”, “lower”, “above”, “below”, and the like are being used to illustrate a relational location.

It is to be understood that the invention 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 of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation. Accordingly, the invention is therefore to be limited only by the scope of the appended claims.

The present disclosure includes a square tooth spline coupling with vibration control. The coupling disclosed herein provides sufficient clearance between the respective male and female splines providing ready assembly and disassembly. With reference now to FIG. 2a, an exploded side partial cutaway view of one embodiment of a coupling assembly and respective shafts is provided. As noted above, during operation of a pumping assembly, a motor shaft is powered by a pump motor, either directly or through a shaft coupling. The coupling assembly provides a manner of connecting the motor shaft to a driven shaft that drives rotating machinery. The coupling connection also transfers rotational energy between the motor and driven shaft, thus providing power for the rotating machinery.

The coupling assembly 30 of FIG. 2a comprises an annular collar 48 with a bore 50 formed lengthwise therein. Female splines 52 extend axially along the bore 50 inner surface. The bore 50 diameter transitions at a point to form a shoulder 56 that is substantially perpendicular to the collar 48 axis A_X. An alignment element 54 is on the shoulder 56. In the embodiment shown, the alignment element 54 has a disc-like midsection and disposed in the collar 48 with its midsection axis (not shown) largely aligned with or parallel to the collar axis A_X. The alignment element 54 outer diameter exceeds the shoulder 56 inner diameter and its lower side butts on the shoulder 56. The outer diameter fits closely in the bore 50. An insert or sleeve 60 is coaxially received within the collar 48 in the portion of the bore 50 having an increased diameter. The insert 60 extends from the upper surface of the alignment member 54 terminating at the upper end of the collar 48. The insert 60 is optionally threaded on its outer diameter to mate with corresponding threads provided on the collar 48 inner diameter. Female splines 52 are formed along the insert 60 inner diameter. Positioning the insert 60 against the alignment element 54 toward the shoulder 56, retains the alignment element 54 within the collar 48.

Centering guides (62, 63) are shown extending from the upper and lower surface of the alignment element 54. In this embodiment, the centering guides (62, 63) comprise conically shaped protusions. Above and below the coupling assembly 30 are an upper shaft 32 and lower shaft 40. The upper shaft 32 lower end 36 is provided with male splines 34 configured for coupling engagement with the female splines 52 of the coupling assembly 30. Similarly, the lower shaft 40 upper end 44 includes male splines 42 configured for coupling engagement with the female splines 52. The shafts (32, 40) are profiled on their terminal ends for centering engagement with the centering guides (62, 63) of the alignment element 54. In the embodiment shown, the profiling on the shafts comprises recesses or bores (38, 46) extending from the terminal mating tips of the shafts and substantially aligned with the respective axes (A_SH, A_SL) of the upper or counterbore lower shafts (32, 40). Each recess (38, 46) has a conical entry way with a taper matching the centering guides (62, 63). The recess and protrusion provide examples of guide profiles formed on the shaft ends and alignment element for engaging the shaft ends to the alignment element. During pumping operations, impellers in the pump create an axial thrust force in the pump shaft forcing the shafts (32, 40) together and engaging the centering guides (62, 63) with the recesses (38, 46).

Referring now to FIG. 2b, an example of an assembled shaft coupling is shown in side cross-sectional view. The male splines 34 on the lower end 36 of the upper shaft 32 engage the female splines 52 and the upper shaft 32 bore 38 mates with the centering guide 62 that extends from the alignment element 54. Similarly, the male splines 42 on the upper end 44 of the lower shaft 40 are engaged with the female splines 52 of the collar 48 and the bore 46 on the upper terminal end of the shaft 40 mates with the centering guide 63 that extends from the opposite side of the alignment element 54. The upper shaft 32 and lower shaft 40 are aligned along a common axis within the collar 48 thus preventing shaft vibration when one of the shafts energizes the other.

FIG. 3a shows an alternative embodiment of a shaft coupling 30a for coupling an upper shaft 36a to a lower shaft 44a. In this embodiment, the alignment element 54a has a largely disc-like cross-sectional area and is seated on the shoulder 56. The insert 60 retains the element 54a within the collar 48. The centering guides (62a, 63a) comprise a conical profile bored into the body of the alignment element 54a. Similarly, the terminal tips of the upper shaft 36a and lower shaft 44a include conically profiled protrusions (39, 47) formed to engaged the bores of the centering guides (62a, 63a). FIG. 3b illustrates the assembled shaft coupling 30a and engagement of the protrusions (39, 47) with the centering guides (62a, 63a). This configuration also control s shaft vibration during transmission of torque through the coupling 30a. The profiles on the alignment elements and the terminal tips of the shafts are not limited to the figures described herein, but can include other shapes such as conical, concave, convex, spherical or other curved surfaces. Additionally, cylindrical profiles with may be employed and may include rounded tips on the cylinder end.

Yet another embodiment of a shaft coupling 30b is provided in side cross-sectional view in FIG. 4a. In this embodiment, the centering guides 62b and centering guide 63b comprise a raised profile on the respective upper and lower sides of the alignment element 54b. The alignment element 54b comprises an upper housing 64, a lower housing 66, and a resilient member housed within the upper and lower housings (64, 66). One example of a resilient member is a spring 68. In this embodiment, the upper and lower housing (64, 66) both comprise a generally cup-like structure having a closed base that is largely perpendicular to the axis of the collar 48a. The housings have sides extending from the base towards an open end, the sides lie generally concentric with the axis A_X of the collar 48a. The upper housing 64 inner diameter is greater than the lower housing 66 outer diameter allowing insertion of the lower housing 66 into the upper housing 64 in telescoping relation. The spring 68 provides a resilient force for urging the upper and lower housing (64, 66) apart.

As shown in FIG. 4b, in some embodiments, a vertical force may move the shaft (32, 40) toward one another and pushes on one of the upper or lower housing (64, 66), thereby compressing the spring 68 there between. One of the advantages of this embodiment is an axial force from one of the shafts (32, 40) is fully absorbed by the spring 68 and not transferred to the other or any other adjacent shaft within a pumping system. Moreover, the resilient nature of the spring 68 can force the housings (64, 66) apart upon absence of the vertical force while continuing axial alignment of the shafts (32, 40) during operation of the pumping system. Because rotational shafts in an ESP seal portion typically are not subjected to axial thrust, the resilient feature may be useful for these couplings. As shown, the housings (64, 66) have protrusions profiled on their respective outer surfaces formed to match recesses (38, 46) on the shafts (32, 40). However, the housings (64, 66) could be fashioned to include recesses and the shafts (32, 40) having corresponding protrusions.

Another embodiment illustrating ESP shaft coupling is provided in a side partial cut-away view in FIG. 5. Here an upper shaft 36b and lower shaft 44b are aligned with a retaining pin 70 that extends from a bore 38b in the lower terminal end of the upper shaft 36b into a corresponding bore 46b in the upper terminal end of the lower shaft 44b. The retaining pin 70 may include an annular shoulder 71 radially disposed around the body of the pin 70 approximately at its mid-section. To accommodate the retaining pin 70, the bores (38b, 46b) are formed deeper into the shafts (36b, 44b) than the bores (38, 46) illustrated in FIGS. 2a and 2b.

A coupling assembly is presented in side partial cross sectional view in FIG. 6 that combines concepts described above. An upper shaft 36 with a bore 38 is disposed within a collar 48b into coaxial alignment with a corresponding lower shaft 44b. A protrusion 47a extends from the lower shaft 44b upper terminal end into the bore 38 and is retained therein for coaxial alignment of the shafts (36, 44b). The protrusion 47a of FIG. 6 is similar to the protrusion 47 of FIGS. 3a and 3b, but has increased dimensions, including an increased length, to ensure mating cooperation with the bore 38. The collar 48b inner diameter is smaller at its upper end to match the upper shaft 36 outer diameter. The collar 48b can be machined or forged as a uni-body configuration, or reduced with an insert (not shown) similar to the collar 48 of FIGS. 2a-3b.

The present invention 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. 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.

Claims

1. A submersible pumping system for pumping wellbore fluid, comprising:

a pump motor;

a splined shaft coupling;

a motor shaft having a splined end rotatably affixed within one end of the shaft coupling, the motor shaft being rotatable by the motor;

a driven shaft having a splined end rotatably affixed within an opposite end of the shaft coupling opposite to the motor shaft, the respective ends of the motor shaft and driven shaft being substantially coaxial within the shaft coupling;

a guide profile on the splined end of each shaft; and

an alignment element mounted in the shaft coupling, the element coaxially engaging the guide profiles on the ends of the motor shaft and driven shaft within the shaft coupling.

2. The pumping system of claim 1, further comprising a first centering guide on one side of the alignment element and a second centering guide on the alignment element opposite side, the first centering guide being substantially coaxial with the second centering guide each centering guide engaging a corresponding guide profile.

3. The pumping system of claim 2 wherein the first and second centering guides selectively comprise a protrusion or a recess.

4. The pumping system of claim 1 wherein the guide profiles on the shafts are conical and located on each shaft axis.

5. The pumping system of claim 1, wherein the guide profiles comprise a protrusion or a recess.

6. The pumping system of claim 1, wherein the coupling has internal square tooth splines.

7. The pumping system of claim 1, wherein the alignment member comprises a disk mounted in the coupling, the disk being perpendicular to the coupling axis.

8. The pumping system of claim 1 further comprising a shoulder formed in the coupling, and a threaded sleeve secured within the coupling, wherein the alignment element comprises a disk secured between the shoulder and the sleeve.

9. The pumping system of claim 1, wherein the alignment element comprises upper and lower housings that telescope relative to one another, and a resilient member.

10. An electrical submersible pump (ESP) comprising:

a pump motor;

a motor shaft mechanically affixed to the pump motor;

a driven shaft;

a splined coupling rotatingly coupling respective splined ends of the motor shaft and the driven shaft;

a tapered centering profile on the splined ends of each shaft coaxial with each shaft axis; and

an alignment device mounted in the coupling the alignment device having a tapered guide profile on one side that mates with the centering profile on the motor shaft and a tapered guide profile on an opposite side that mates with the centering profile on the driven shaft.

11. The ESP of claim 10 wherein the tapered centering profiles and the tapered guide profiles are conical.

12. The ESP of claim 18, wherein the alignment device comprises an upper housing and a lower housing, each housing having one of the guide profiles, and a spring located between the upper housing and the lower housing urging the upper housing and the lower housing apart.

13. A method of connecting a live shaft of an ESP pump motor to a driven shaft, the shafts having splined ends, the method comprising:

providing a guide profile on each splined shaft end;

mounting an alignment element within a splined coupling; and

inserting the splined shaft ends into the coupling and engaging profiles on the alignment element.

14. The method of claim 13, wherein the profile comprises a protrusion and the alignment element comprises a recess configured to receive the protrusion.

15. The method of claim 13, wherein the alignment element comprises a protrusion and the profile comprises a recess configured to receive the protrusion.

16. The method of claim 13, wherein the shaft ends are maintained coaxial within the coupling by engaging the profiles with the alignment element.

17. The method of claim 13, wherein the alignment element comprises a disk member having profiles on its upper and lower surface, the method further comprising mounting the alignment element perpendicularly in the splined coupling.