Title:
PROGRESSIVE CAVITY PUMP
Kind Code:
A1


Abstract:
An electric submersible progressing cavity pump (ESPCP) assembly that restricts reverse rotation of the pump motor and provides for efficient motor shutdown in the event of reverse rotation is disclosed. When the ESPCP rotates in a reverse direction, components associated with the rotating motor shaft stop rotation of the shaft to increase the torque and current of the motor, and the increased torque/current on the motor actuates a torque or current limit switch to shut off the motor. Also, particle and gas separation mechanisms are disclosed, which separate particulates and gas from the fluid flowing into the pump so that the fluid that reaches the rotor and stator assembly has a higher proportion of liquid than the resident well fluid.



Inventors:
Bookout, Russell (Fort Wayne, IN, US)
Application Number:
13/967904
Publication Date:
04/17/2014
Filing Date:
08/15/2013
Assignee:
FRANKLIN ELECTRIC COMPANY, INC.
Primary Class:
Other Classes:
417/44.11, 417/423.3
International Classes:
F04D13/06; F04D13/10
View Patent Images:
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Primary Examiner:
MICK, STEPHEN A
Attorney, Agent or Firm:
FAEGRE DRINKER BIDDLE & REATH LLP (FORT WAYNE, IN, US)
Claims:
1. An electric submersible progressing cavity pump assembly comprising: a motor having a shaft defining a longitudinal axis, said shaft rotatable in a forward direction and in a reverse direction; a coupling rotatably fixed to said shaft; a collar releasably coupled with said coupling, said collar movable along said longitudinal axis; a bracket attached to said motor and at least partially surrounding said collar, said bracket comprising at least one stationary stop; said collar positionable in a first position adjacent said coupling when said shaft is rotated in said forward direction; and said collar displaceable from said coupling along said longitudinal axis to a second position in which said collar contacts said at least one stationary stop when said shaft is rotated in said reverse direction.

2. The pump assembly of claim 1, further comprising a torque detection switch, said torque detection switch operable to stop said motor when said collar contacts said at least one stationary stop.

3. The pump assembly of claim 1, further comprising a current detection switch, said current detection switch operable to stop said motor when said collar contacts said at least one stationary stop.

4. The pump assembly of claim 1, wherein said coupling and said collar comprise respective surfaces disposed substantially parallel to said longitudinal axis, said surfaces in driving contact with one another with said shaft is rotated in said forward direction and said surfaces spaced from one another when said shaft is rotated in said reverse direction.

5. The pump assembly of claim 1, wherein said collar further comprises at least one ramped surface, said at least one ramped surface contacting said at least one stationary stop when said shaft is rotated in said reverse direction.

6. The pump assembly of claim 1, wherein said collar further comprises an outer circumference and at least one vane situated along said outer circumference, said at least one vane contacting said at least one stationary stop when said shaft is rotated in said reverse direction.

7. The pump assembly of claim 6, wherein said at least one vane is angled such that a first force, urging said collar into said first position, is applied to each said vane when said collar is rotated in said forward direction, and a second force, urging said collar into said second position, is applied to each said vane when said collar is rotated in said reverse direction.

8. The pump assembly of claim 6, comprising a plurality of said vanes, said plurality of vanes defining a plurality of circumferential gaps each disposed between a respective pair of said vanes.

9. The pump assembly of claim 1, wherein said coupling comprises a first ramp surface and said collar comprises an second ramp surface complementary to said first ramp surface, said first and second ramp surfaces sliding with respect to one another to urge said collar into said second position when said shaft is rotated in said reverse direction.

10. The pump assembly of claim 1, wherein said bracket further comprises at least one fluid inlet.

11. An electric submersible progressing cavity pump assembly for pumping a fluid having entrained particulates, comprising: a motor having a rotatable shaft defining a longitudinal axis; a pump mechanism driven by said shaft to pump the fluid; a shell disposed intermediate said motor and said pump assembly, said shell including at least one slot; and an inducer at least partially disposed within said shell, said inducer driven by said shaft for rotation about said longitudinal axis, said inducer operable to centrifugally urge particulates in the fluid outwardly from said shell through said at least one slot.

12. The pump assembly of claim 11, wherein said inducer comprises a helical thread.

13. The pump assembly of claim 11, wherein said inducer is formed of a resilient material and overlies said shaft.

14. The pump assembly of claim 11, wherein said shell comprises a plurality of said slots, said slots disposed in a helically staggered, spaced relation with respect to one another along a length of said shell.

15. An electric submersible progressing cavity pump assembly for pumping a fluid having entrained gas bubbles, comprising: a motor having a rotatable shaft defining a longitudinal axis; a pump mechanism driven by said shaft to pump the fluid; a shell disposed intermediate said motor and said pump assembly and comprising at least one hole; and a gas separator at least partially disposed within said shell, said gas separator operable to channel entrained gas bubbles in the fluid outwardly from said shell through said at least one hole.

16. The pump assembly of claim 15, wherein said gas separator is a crossover device comprising at least one port, each said port of said crossover aligned with a respective said hole in said shell.

17. The pump assembly of claim 16, wherein said crossover device further comprises a wall disposed with said shell, said wall including at least one port, said port spaced from said shaft and disposed radially adjacent said shell.

18. The pump assembly of claim 17, wherein said crossover device comprises a plurality of said walls having a respective plurality of said ports, and a plurality of circumferentially spaced channels defined between respective pairs of said walls, said channels aligned with respective said ports.

19. The pump assembly of claim 16, wherein said crossover device further comprises a top opening, and a penetrable resilient gas barrier positioned in said top opening.

20. The pump assembly of claim 16, wherein said crossover device further comprises a top opening, said shaft extending through said top opening.

21. The pump assembly of claim 15, wherein said gas separator further comprises a gas slinger rotatable with said shaft.

Description:

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional Patent Application Ser. No. 61/691,426, filed Aug. 21, 2012, and U.S. Provisional Patent Application Ser. No. 61/783,263, filed Mar. 14, 2013, the disclosures of which are hereby expressly incorporated by reference herein in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Disclosure

The present disclosure relates generally to systems and methods associated with progressing cavity pumps and, in particular, to systems and methods associated with electric submersible progressing cavity pumps (“ESPCP”).

2. Description of the Related Art

An ESPCP includes a rotor and stator for pressurizing fluid. In one known well arrangement, an ESPCP is positioned in an interior of a well to pump fluid from the well towards the surface. Rotation of the rotor is driven by an electric motor submerged in fluid below the rotor and stator. A shaft allowing for eccentricity connects the electric motor to the rotor. The ESPCP includes a check valve that restricts fluid from flowing through the ESPCP in a reverse direction. If the electric motor is started in a reverse direction, the check valve will prevent downstream fluid from entering the ESPCP, which may cause rapid heating of the rotor and stator.

Also, in many well arrangements which include an ESPCP, pumped fluids may include entrained particles, such as sand, as well as gas in the form of bubbles. Problematically, entrained particles and gas bubbles can prevent optimum operation of the ESPCP.

What is needed is an improvement over the foregoing.

SUMMARY

The present disclosure provides an electric submersible progressing cavity pump (ESPCP) assembly that restricts reverse rotation of the pump motor and provides for efficient motor shutdown in the event of reverse rotation. In particular, when the ESPCP rotates in a reverse direction, components associated with the rotating motor shaft stop rotation of the shaft to increase the torque and current of the motor, and the increased torque/current on the motor actuates a torque or current limit switch to shut off the motor. Also, particle and gas separation mechanisms are provided, which separate particulates and gas from the fluid flowing into the pump so that the fluid that reaches the rotor and stator assembly has a higher proportion of liquid than the resident well fluid.

In one illustrative embodiment, an electric submersible progressing cavity pump assembly includes a motor having a shaft defining a longitudinal axis, the shaft rotatable in a forward direction and in a reverse direction; a coupling rotatably fixed to the shaft; a collar releasably coupled with said coupling, the collar movable along the longitudinal axis; a bracket attached to the motor and at least partially surrounding said collar, the bracket comprising at least one stationary stop; the collar positionable in a first position adjacent the coupling when the shaft is rotated in the forward direction; and the collar displaceable from the coupling along the longitudinal axis to a second position in which the collar contacts the at least one stationary stop when the shaft is rotated in the reverse direction.

In another illustrative embodiment, an electric submersible progressing cavity pump assembly for pumping a fluid having entrained particulates includes a motor having a rotatable shaft defining a longitudinal axis; a pump mechanism driven by the shaft to pump the fluid; a shell disposed intermediate the motor and the pump assembly, the shell including at least one slot; and an inducer at least partially disposed within the shell, the inducer driven by the shaft for rotation about the longitudinal axis, the inducer operable to centrifugally urge particulates in the fluid outwardly from the shell through the at least one slot.

In another illustrative embodiment, an electric submersible progressing cavity pump assembly for pumping a fluid having entrained gas bubbles includes a motor having a rotatable shaft defining a longitudinal axis; a pump mechanism driven by the shaft to pump the fluid; a shell disposed intermediate the motor and the pump assembly and comprising at least one hole; and a gas separator at least partially disposed within the shell, the gas separator operable to channel entrained gas bubbles in the fluid outwardly from the shell through the at least one hole.

It should be understood that the components that stop rotation of the shaft to actuate a limit switch to shut off the motor, the particle separation mechanisms that separate particulates from the fluid, and the gas separation mechanisms that separate gas from the fluid may be employed in pump devices individually, or the foregoing devices may be combined, including any two of the features or all three features, into the same device.

Additional features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following detailed description of the illustrative embodiment exemplifying the best mode of carrying out the invention as presently perceived.

BRIEF DESCRIPTION OF THE DRAWINGS

The above mentioned and other features and advantages of this disclosure, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a longitudinal sectional view of an exemplary electric submersible progressing cavity pump positioned in a well bore;

FIG. 2 is a partial sectional view of a portion of an electric submersible progressing cavity pump including a backstop with the motor shaft rotating in a forward direction;

FIG. 2A is an enlarged view of a portion of FIG. 2 further illustrating the collar ramp surfaces;

FIG. 2B is another enlarged view of a portion of FIG. 2 further illustrating the collar ramp surfaces;

FIG. 3 is a side sectional view of the portion of the electric submersible progressing cavity pump of FIG. 2;

FIG. 4 is the partial sectional view of the portion of the electric submersible progressing cavity pump of FIG. 2 with the motor shaft rotating in a reverse direction;

FIG. 4A is an enlarged view of a portion of FIG. 4 further illustrating the collar ramp surfaces;

FIG. 5 is a side sectional view of the portion of the electric submersible progressing cavity pump of FIG. 4;

FIGS. 6-9 are graphs illustrating the starting characteristics of an electric submersible progressing cavity pump including a backstop;

FIG. 10 is a schematic of an exemplary torque limit switch;

FIG. 10A is a schematic of an exemplary current limit switch;

FIG. 11 is a flow chart of an exemplary processing sequence for a torque limit switch;

FIG. 12 is an exploded perspective view of another exemplary backstop including a coupling and a collar for an electric submersible progressing cavity pump;

FIG. 13 is a perspective view of the assembled coupling and collar of FIG. 12;

FIG. 14 is a side sectional view of another exemplary backstop for an electric submersible progressive cavity pump;

FIG. 15 is an cross-sectional view of the backstop of FIG. 14;

FIG. 16 is another side sectional view of the backstop of FIG. 14 illustrating the electric submersible progressive cavity pump rotating in the forward direction;

FIG. 17 is another side sectional view of the backstop of FIG. 14 illustrating the electric submersible progressive cavity pump rotating in the reverse direction;

FIG. 18 is a perspective view of another exemplary bracket for an electric submersible progressive cavity pump;

FIG. 19 is an overhead view of the bracket of FIG. 18;

FIG. 20 is a longitudinal sectional view of an exemplary electric submersible progressive cavity pump including sand and gas separating components;

FIG. 21 is an upper perspective view of an exemplary radial entry crossover;

FIG. 22 is a lower perspective view of the crossover of FIG. 21;

FIG. 23 is an enlarged fragmentary sectional view of a portion of FIG. 20 further illustrating the radial entry crossover and a gas slinger;

FIG. 24 is an upper perspective view of an exemplary axial entry crossover;

FIG. 25 is a lower perspective view of the crossover of FIG. 24;

FIG. 26 is an enlarged fragmentary side sectional view of a portion of FIG. 20 further illustrating the axial entry crossover and gas slinger;

FIG. 27 is an upper perspective view of a radial entry crossover including a rubber gas barrier; and

FIG. 28 is a side sectional view of the crossover of FIG. 21 showing the rotor breaching the rubber gas barrier.

Corresponding reference characters indicate corresponding parts throughout the several views. Although the drawings represent embodiments of various features and components according to the present disclosure, the drawings are not necessarily to scale and certain features may be exaggerated in order to better illustrate and explain the present disclosure. The exemplification set out herein illustrates embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION

A. Introduction

For the purposes of promoting and understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings, which are described below. The embodiments disclosed below are not intended to be exhaustive or limit the invention to the precise form disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may utilize their teachings. It will be understood that no limitation of the scope of the invention is thereby intended. The invention includes any alterations and further modifications in the illustrated devices and described methods and further applications of the principles of the invention which would normally occur to one skilled in the art to which the invention relates.

Referring to FIG. 1, a lower portion of an exemplary electric submersible progressing cavity pump (“ESPCP”) 12 is illustrated. ESPCP 12 is illustrated in FIG. 1 centered in an interior of well 14 having sides 16 defining a well bore. ESPCP 12 includes progressing cavity pump 18 having a rotor 20 and stator 22. Rotation of rotor 20 inside stator 22 pressurizes fluid inside progressing cavity pump 18. When rotor 20 is rotated in a forward direction, fluid is directed towards the top fluid surface of the well from progressing cavity pump 18 through a drop pipe (not shown) attached to one end of progressing cavity pump 18.

Rotation of rotor 20 within stator 22 is powered by electric motor 24. In one embodiment, electric motor 24 is a submersible electric motor configured to be submerged in fluid below progressing cavity pump 18 when ESPCP 12 is positioned in well 14. Electric motor 24 may be, for example, a Franklin Electric CBM plus motor model #23472935256. ESPCP 12 may include a motor lead (not shown) providing electric power and control signals to electric motor 24 from the surface of the well installation. The shaft of electric motor 24 is connected to rotor 20 through flex shaft 26. Extension 28 surrounds flex shaft 26 between electric motor 24 and progressing cavity pump 18. In the embodiment illustrated in FIG. 1, fluid inlets 30 allow fluid in the interior of well 14 to enter extension 28 to be pumped by progressing cavity pump 18 towards the surface. Exemplary fluids include, but are not limited to, water, oil, other petroleum products, and fluid mixtures.

In one embodiment, progressing cavity pump 18 may include a check valve (not shown) at one end. The check valve restricts fluid from flowing through progressing cavity pump 18 in a reverse direction. If electric motor 24 is started in a reverse direction, the check valve will prevent downstream fluid from entering progressing cavity pump 18. Additionally, fluid passing fluid inlets 30 will not be drawn into progressing cavity pump 18 if rotor 20 rotates in a reverse direction. With no fluid in progressing cavity pump 18, reverse rotation of rotor 20 may cause rapid heating of rotor 20 and stator 22. In one embodiment, rapid heating of the rubber forming stator 22 may quickly lead to catastrophic failure. The exemplary backstop elements of the present disclosure restrict electric motor 24 and progressing cavity pump 18 from rotating in a reverse direction, thereby restricting the potential for motor failure.

Electric motor 24 is attached to extension 28 through motor bracket 32. The exterior of electric motor 24 is stationary relative to attached motor bracket 32, the exterior of extension 28, and stator 22. Motor shaft 34 and coupling 36 transmit rotational energy from electric motor 24 to flex shaft 26 and rotor 20.

B. Backstop Mechanisms

Referring next to FIG. 2, a partial sectional view of motor bracket 32 is illustrated. In the illustrated embodiment, motor bracket 32 is secured to electric motor 24 using one or more fasteners 25. Motor shaft 34 and coupling 36 are connected, such as being splined or keyed or through another suitable method, to rotate together within motor bracket 32. In an exemplary embodiment, coupling 36 is connected to motor shaft 34 such that relative axial displacement between coupling 36 and motor shaft 34 is prevented. As illustrated in FIG. 1, flex shaft 26 is attached to upper coupling portion 38 and rotor 20 such that flex shaft 26 rotates with motor shaft 34 to drive rotor 20.

Referring back to FIG. 2, collar 40 is illustrated in a first position encircling upper coupling portion 38. In the illustrated embodiment, collar 40 is not rigidly attached to coupling 36, but is configured to releasably engage with coupling 36 when rotated in forward direction 44 and releasably engage with stationary stop elements 42 and coupling 36 when rotated in reverse direction 56 (see FIG. 4). In the embodiment illustrated in FIG. 2, three stationary stop elements 42 are shown. In other embodiments, more or fewer than three stationary stop elements 42 may be provided. In the illustrated embodiment, stationary stop elements 42 are formed as part of motor bracket 32 (an alternative of which, bracket 32B, is shown in FIGS. 19 and 20 and described below). In another embodiment, stationary stop elements 42 are discrete elements attached to motor bracket 32. Stationary stop elements 42 do not rotate with motor shaft 34 or coupling 36. In one embodiment, stationary stop elements 42, collar 40, and coupling 36 cooperate to form a means for allowing rotation of motor shaft 34 when motor shaft 34 is rotating in forward direction 44 (FIG. 2) and means for stopping rotation of motor shaft 34 when motor shaft 34 begins to rotate in reverse direction 56 (FIG. 4).

In one embodiment, collar 40 includes an upper portion having a first diameter including upper ramp surfaces 60 with upper projections 54 and a lower portion having a second diameter including ramp surfaces 48 and lower projections 52. In the embodiment illustrated in FIGS. 2 and 3, the first diameter is larger than the second diameter, resulting in collar 40 having a shape that flares outwardly from bottom to top. In the illustrated embodiment, the flared shape allows stationary stop elements 42 to have a sufficient interior radial clearance to facilitate more room for the insertion of rotor 20 through motor bracket 32 during assembly of ESPCP 12.

In the embodiment illustrated in FIGS. 2 and 3, when electric motor 24 rotates motor shaft 34 in a forward direction, as indicated by arrows 44, collar 40 does not engage stationary stops 42. Rotation in forward direction 44 allows ramp surfaces 46 of coupling 36 and ramp surfaces 48 of collar 40 to cooperate such that lower portion 50 of coupling 36 abuts lower portion 52 of collar 40, which causes collar 40 to rotate with coupling 36 in forward direction 44. In this manner, a driving connection is provided between portion 50 of coupling 36 and portion 52 of collar 40, such that coupling 36 drives collar 40 in the forward direction such that sliding of ramp surface 48 along or relative to ramp surface 46 is prevented. Further, referring to FIG. 2B coupling 36 may be constructed to have one or more protrusions 47 extending from and maintaining substantially the same angle as ramp surface 46. Protrusion 47 can engage notch 49 to present a physical barrier to prevent collar 40 from moving axially upward relative to coupling 36 when collar 40 and coupling 36 rotate in the forward direction. As illustrated in FIG. 3, during rotation of collar 40 in forward direction 44, upper projections 54 on collar 40 are positioned below stationary stops 42 and do not engage stationary stops 42 during forward rotation. In the illustrated embodiment, three upper projections 54 are shown. In other embodiments, more or fewer than three upper projections 54 are provided. In one embodiment, the number of stationary stop elements 42 is the same as the number of upper projections 54.

Referring next to FIG. 4, a partial sectional view of motor bracket 32 shown in FIG. 2 is illustrated in which the motor shaft 34 has been rotated in a reverse direction, as indicated by arrows 56. In the illustrated embodiment, motor shaft 34 is rotationally locked with coupling 36, such as being splined, keyed, or other suitable method. In this embodiment, rotation of motor shaft 34 in reverse direction 56 causes coupling 36 to also rotate in reverse direction 56. The inertia of collar 40 causes collar 40 to axially displace from coupling 36 as coupling 36 rotates in reverse direction 56, with portion 50 of coupling initially separating from portion 52 of collar 40 and ramp surfaces 48 sliding along ramp surfaces 46. As seen in FIGS. 4 and 5, collar 40 will be displaced upwardly and away from coupling 36 into a second position along the axis of motor shaft 34 until upper projections 54 of collar 40 engage stationary stop elements 42.

In the embodiment illustrated in FIGS. 4 and 5, once upper projections 54 engage stationary stop elements 42, rotation of collar 40 about the longitudinal axis of motor shaft 34 is stopped. Collar 40 may continue being forced upward away from coupling 36 until surface 58 of upper ramp surfaces 60 of collar 40 near upper projection 54 abuts stationary stop elements 42 (See also FIG. 2). Surface 58 resists further axial displacement of collar 40.

In one exemplary embodiment, ramp surfaces 48, 58 have a helical pitch of about 2 inches. In one exemplary embodiment, collar 40 has a shape that flares outwardly from bottom to top and ramp surface 58 has a ramp angle with a horizontal plane orthogonal to an axis aligned with motor shaft 34. In the embodiment illustrated in FIGS. 2A and 4A, collar 40 flares outwardly from bottom to top and the angle of ramp surface 58 to a horizontal plane orthogonal to the motor shaft 34 varies from a first ramp surface 62 at the smaller bottom diameter of collar 40 having an angle of about 30° to a second ramp surface 64 at the larger upper diameter of collar 40 having an angle of about 25°. Angles within the range of 25-30° may be utilized.

Referring again to the embodiment illustrated in FIGS. 4 and 5, once upper projections 54 and surface 58 engage stationary stop elements 42, collar 40 can no longer rotate relative to coupling 36 or move axially relative to coupling 36. Collar 40 transmits a force resisting further rotation through ramp surfaces 48 to adjacent ramp surfaces 46 of coupling 36. Because coupling 36 is attached to motor shaft 34, this force is further transmitted to motor shaft 34 and electric motor 24. Thus, in the illustrated embodiment, rotation of electric motor 24 in a reverse direction 56 will cause collar 40 to engage stationary stop elements 42 and stop movement of motor shaft 34.

FIGS. 6-9 are graphs illustrating the starting characteristics over time of electric motor 24 of ESPCP 12 including an exemplary backstop comprising collar 40, coupling 36, and stationary stop elements 42 on motor bracket 32. The top curve labeled “1” indicates the current with a scale of 0.1 v/amp, the bottom curve labeled “2” indicates the voltage (50.8x scale), and the middle curve labeled “3” indicates the percent of maximum torque. Point “a” on the x-axis indicates 543 milliseconds and point “b” on the x-axis indicates 794 milliseconds from a motor start point.

FIG. 6 is a graph showing the starting characteristics of electric motor 24 supplied with 20 Hz power when the electric motor 24 is started in forward direction 44. FIG. 7 is a graph showing the starting characteristics of electric motor 24 supplied with 20 Hz power when the electric motor 24 is started in reverse direction 56. FIG. 8 is a graph showing the starting characteristics of electric motor 24 supplied with 50 Hz power when the electric motor 24 is started in forward direction 44. FIG. 9 is a graph showing the starting characteristics of electric motor 24 supplied with 50 Hz power when the electric motor 24 is started in reverse direction 56.

As illustrated in FIGS. 6 and 8, when electric motor 24 rotates in forward direction 44, motor shaft 34 turns in forward direction 44 and collar 40 does not engage stationary stop elements 42. This allows coupling 36 and flex shaft 26 to also rotate in forward direction 44, which rotate rotor 20 in forward direction 44. As illustrated in FIGS. 7 and 9, when electric motor 24 rotates in reverse direction 56, collar 40 engages stationary stop elements 42, resulting in a rapid increase in torque shown by the rapid rise in middle curve just prior to point “a”. This prevents coupling 36 and flex shaft 26 from rotating in reverse direction 56, which prevents rotor 20 from rotating in reverse direction 56 in stator 22. In FIGS. 7 and 9, the maximum torque occurs at approximately 500 to 600 milliseconds. In one embodiment, as described below, the higher torque resulting from collar 40 engaging stationary stop elements 42 is monitored by a torque sensor attached to electric motor 24, and may trigger a torque limit switch to stop electric motor 24.

In one embodiment, electric motor 24 includes a torque limit or torque detection switch. The torque limit switch monitors the torque necessary for electric motor 24 to rotate motor shaft 34 and stops electric motor 24 from applying further torque to motor shaft 34 if the torque limit switch determines that the monitored torque exceeds a predetermined torque limit. In one embodiment, once the torque generated by electric motor 24 does not exceed the predetermined torque limit, the torque limit switch is reset and electric motor 24 can again attempt to rotate motor shaft 34. In one embodiment, the torque limit switch is a physical switch (not shown). Exceeding the predetermined torque limit results in a mechanical action stopping electric motor 24. In another embodiment, the torque limit switch controls the current to the motor. In this embodiment, exceeding a predetermined current results in the torque limit switch turning off electric motor 24.

In another embodiment, illustrated in FIG. 10, the torque limit switch is electronic switch 100. Switch 100 includes processor 102 and memory 104. Processor 102 may comprise a single processor or may include multiple processors, located either locally with switch 100 or accessible across a network. Memory 104 is a computer readable medium and may be a single storage device or may include multiple storage devices, located either locally with switch 100 or accessible across a network. Computer-readable media usable as memory 104 may be any available media that may be accessed by processor 102 and includes both volatile and non-volatile media. Further, computer readable-media may be one or both of removable and non-removable media. By way of example, computer-readable media may include, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, Digital Versatile Disk (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which may be used to store the desired information and which may be accessed by switch 100. In one embodiment, switch 100 communicates data, status information, or a combination thereof to a remote device for analysis. In one embodiment, switch 100 includes torque limit switch software 106 stored in memory 104. Torque limit switch software 106 monitors the torque of electric motor 24 as determined by a torque sensor 108. Torque limit switch software 106 executes appropriate steps to stop electric motor 24 from applying torque to attempt to rotate motor shaft 34 if it determines that the monitored torque exceeds a predetermined torque limit. In another embodiment, illustrated in FIG. 10A, torque limit switch software 106 has been replaced with current limit switch software 107 and torque sensor 108 has been replaced with current sensor 109. Current limit switch software 107 monitors the current of electric motor 24 and stops electric motor 24 when the current reaches a predetermined maximum threshold, such as that which is achieved when upper projections 54 of collar 40 engage stationary stop elements 42 during reverse rotation of motor shaft 34.

Referring again to FIGS. 3 and 4, if the torque limit switch determines that the torque generated by electric motor 24 to rotate motor shaft 34 exceeds a predetermined value, the torque limit switch stops electric motor 24 from applying torque to attempt to rotate motor shaft 34. In one embodiment, torque limit switch stops electric motor by disrupting power to electric motor 24. In another embodiment, the torque limit switch stops electric motor by disengaging motor shaft 34 from electric motor 24. Other suitable methods of stopping electric motor 24 from applying torque to attempt to rotate motor shaft 34 may also be used.

An exemplary processing sequence 110 for switch 100 is illustrated in FIG. 11. In step 112, a predetermined torque limit value is received. In step 114, the torque determined by torque sensor 108 on electric motor 24 is monitored. In step 116, if the torque determined by torque sensor 108 does not exceed the predetermined torque limit value, the system returns to step 114 to monitor the current torque. If the torque determined by torque sensor 108 does exceed the predetermined torque limit value, the system stops the electric motor 24 from applying torque to motor shaft 34 in step 118. If the system is not reset, the electric motor 24 is maintained in a status of not applying torque. If the system is reset in step 120, the system returns to monitoring the current torque in step 114.

In the embodiment illustrated in FIGS. 4 and 5, once the electric motor 24 is no longer attempting to rotate motor shaft 34 and coupling 36 in the reverse direction 56, ramp surface 46 will stop applying force to ramp surface 48 of collar 40. When electric motor attempts to rotate motor shaft 34 and coupling 36 in the forward direction 44, collar 40 will slide back down ramp surface 46 along ramp surface 48 until lower portion 52 abuts lower portion 50 of coupling 36, as illustrated in FIGS. 2 and 3. In this position, upper projections 54 do not engage stationary stop elements 42 and collar 40 can rotate with coupling 36 in the forward direction 44.

C. Alternative Backstop Mechanism Embodiments

Backstop mechanisms including various coupling-collar combinations can be constructed. Referring next to FIGS. 12 and 13, another coupling 36A and collar 40A for ESPCP 12 is illustrated. As illustrated in FIGS. 12 and 13, coupling 36A is similar to coupling 36 and collar 40A is similar to collar 40 illustrated in FIGS. 2-5, but utilizes a different series of ramps. In one embodiment, stationary stop elements 42, collar 40A, and coupling 36A cooperate to form a means for allowing rotation of motor shaft 34 when motor shaft 34 is rotating in forward direction 44 and means for stopping rotation of motor shaft 34 when motor shaft 34 begins to rotate in reverse direction 56.

As illustrated in FIG. 12, collar 40A includes a plurality of upper projections 54A and upper ramp surfaces 60A for engaging stationary stop elements 42 attached to motor bracket 32. Coupling 36A is attached to and rotates with motor shaft 34. In the illustrated embodiment, ramp surface 48A is a single surface that wraps helically around an interior surface of collar 40A. Ramp surface 48A cooperates with ramp surface 46A on coupling 36A. In the illustrated embodiment, ramp surface 46A is a single surface that wraps helically around an exterior of coupling 36A. In another embodiment, one or both of ramp surface 46A and ramp surface 48A are comprised of multiple surfaces.

In one embodiment, as electric motor 24 rotates coupling 36A in a forward direction, ramp surfaces 46A of coupling 36A and ramp surfaces 48A of collar 40A cooperate such that collar 40A rotates with coupling 36A in the forward direction. During rotation in the forward direction, upper projections 54A are positioned below stationary stops 42 and do not engage stationary stops 42.

In this illustrated embodiment, when electric motor 24 rotates coupling 36A in reverse direction 56, ramp surface 46A of coupling 36A engages ramp surface 48A of collar 40A. The force of ramp surface 46A against ramp surface 48A in reverse direction 56 causes collar 40A to axially displace relative to coupling 36A and begin to rotate collar 40A in reverse direction 56. Rotating collar 40A in reverse direction 56 causes collar 40A to be forced upwardly and away from coupling 36A along the axis of motor shaft 34 until upper projections 54A of collar 40A engage the stationary stop elements 42. Once upper projections 54A engage the stationary stop elements 42, collar 40A transmits a force through ramp surfaces 48A to coupling 36A through adjacent ramp surfaces 46A, resisting the further rotation of coupling 36A. Because coupling 36A is attached to motor shaft 34, this force is further transmitted to motor shaft 34 and electric motor 24. Thus, in the illustrated embodiment, rotation of electric motor 24 in reverse direction 56 will cause collar 40A to engage stationary stop elements 42 and stop movement of motor shaft 34. In one embodiment, a torque limit switch stops electric motor 24 from applying torque to attempt to rotate motor shaft 34.

Referring now to FIG. 14-17, an alternative coupling 36B and an alternative collar 40B for ESPCP 12 are illustrated. Coupling 36B is substantially the same as coupling 36 illustrated in FIG. 2 except as described below. Collar 40B includes three abbreviated vanes 80B situated around outer the circumference of collar 40B. Additionally, as with previous embodiments, coupling 36B is cylindrically secured to and rotates with both motor shaft 34 and flex shaft 26. Each vane 80B slopes at an angle between 30 and 60 degrees relative to a horizontal plane normal to the vertical axis defined by both flex shaft 26 and motor shaft 34. In the illustrated embodiment, three vanes 80B are shown. In other embodiments, more or fewer than three vanes 80B may be provided.

FIGS. 15-17 illustrate how circumferential gaps 90B, defined between vanes 90B, provide additional space for fluid flow along the length of ESPCP 12. Each circumferential gap 90B separates a respective pair of circumferentially adjacent vanes 80B and there are an equal number of gaps 90B and vanes 80B. Advantageously, referring to FIG. 15, each gap 90B provides additional cross-sectional area between the inner circumference of bracket 32B and the outer circumferences of both coupling 36B and collar 40B. FIGS. 16 and 17 illustrate how circumferential gaps 90B can be defined along both the outer circumference of coupling 36B and the outer circumference of collar 40B.

FIGS. 16 and 17 also illustrate the rotation of motor shaft 34 in the forward and reverse directions, respectively. FIG. 16 illustrates rotation of motor shaft 34 in forward direction 44 in which fluid is pumped upwardly as viewed in FIG. 16. When motor shaft 34, which is splined, keyed, or attached by another suitable method to coupling 36B, rotates coupling 36B in the forward direction, collar 40B in engaged by, and rotates with, coupling 36B in the manner described above. During such forward rotation, there is no sliding of ramp surface 48B along or relative to ramp surface 46B and portions 50B and 52B of coupling 36B and collar 40B, respectively, drivingly engage one another.

Additionally, during rotation in the forward direction, a downforce F1 is exerted on the top surfaces of vanes 80B as the top surfaces of vanes 80B are angled such that each vane 80B resistingly confronts the fluid as vanes 80B are rotated. This downforce helps maintain the engagement between coupling 36B and collar 40B by preventing axial displacement of collar 40B away from coupling 36B and advantageously provides additional pumping force to the fluid flowing through the pump. In this manner, because axial displacement of collar 40B from coupling 36B is prevented, vanes 80B rotate and pass underneath stationary stops 42B formed along the interior of bracket 32B.

FIG. 17 illustrates reverse rotation 56 that causes vanes 80B to engage stationary stops 42B to actuate the torque limit switch and stop electric motor 24. As motor shaft 34 rotates coupling 36B in reverse direction 44, portions 50B and 52B of coupling 36B and collar 40B, respectively, separate from one another. As portions 50B and 52 separate, the inertia of collar 40B will cause ramp surface 48B to slide upward and along ramp surface 46B, causing axial displacement of collar 40B from coupling 36B.

This axial displacement of collar 40B from coupling 36B effects the stoppage of electric motor 24 in the manner described above. Additionally, as collar 40B is urged in the reverse direction, portion 52B begins to separate from portion 50B due to the inertia of collar 40B to expose portion 52B. Fluid force F3 acts on exposed portion 52B to urge ramp surface 48B upward along ramp surface 46B so that collar 40B rises. Further, as coupling 36B rotates in the reverse direction, vanes 80B contribute to the axial displacement of collar 40B because, as previously described, collar 40B is urged in the reverse direction and the bottom surface of each vane 80B faces and pushes against the fluid. Because each vane 80B is angled as shown, this pushing causes lift F2 on that bottom surface of each vane 80B to assist with the axial displacement of collar 40B relative to coupling 36B. These two fluid forces F3 and F2 combine to effect the axial displacement of collar 40B from coupling 36B so that vanes 80B can engage stationary stops 42B. As previously described in further detail for other embodiments, when vanes 80B strike stationary stops 42B, the stoppage of the reverse rotation increases the torque on motor shaft 34 that actuates a torque limit switch to shut off electric motor 24.

Advantageously, since assembly and replacement of parts for ESPCP 12 can require installing parts of various sizes, abbreviated vanes 80B allow for the use of modified bracket 32B having minimized stationary stops 42B, as shown in FIG. 19. Stationary stops 42B define stationary stop circle CS. The further stationary stops 42B extend radially inward, the smaller the area of stationary stop circle CS will be. However, the design of vanes 80B minimizes the distance that stationary stops 42B must extend radially inward to engage vanes 80B and stop reverse rotation of electric motor 24. Thus, modified bracket 32B has been designed to maximize the area of stationary stop circle CS so that bracket 32B can accommodate the insertion of a wide range of different sized rotors 20 (not shown) and other components that would have to be installed or replaced in ESPCP 12.

D. Particulate and Gas Separation

Referring to FIG. 20, ESPCP 12 is shown with mechanisms for separating entrained particulates and gas from the pumped fluid. Bottom shell 200 includes particulate slots 204 and gas holes 208, and is constructed from a rigid outer layer and may include a resilient interior layer 212 formed of rubber, for example. A resilient inducer 216, made of rubber, for example, is housed within bottom shell 200. Inducer may be molded onto, and thereby rotates with, flex shaft 26 to effect the expulsion of particulates and gas in the manner described below. As pumped fluid moves from the bottom to the top of bottom shell 200, the fluid first traverses the particulate separation components and then traverses the gas separation components.

First, referring to FIG. 20, particulate slots 204 accommodate fluid entering bottom shell 200, represented by arrows A1, and particulates exiting bottom shell 200, represented by arrows A2. Inducer 216 has a helical thread 220 with a pitch that progressively shortens from the bottom to the top of inducer 216.

Particulates are expelled from the fluid through particulate slots 204 by rotation of inducer 216, which centrifugally forces particulates radially outwardly. As the fluid, containing entrained particulates, travels the length of inducer 216 along rotating helical thread 220, the relatively heavier particulates in the fluid are centrifugally forced outwardly and are expelled through particulate slots 204 concurrently with the intake of some fluid into slots 204. Further, to prevent redeposition of particulates through one particulate slot 204 that have already been expelled through another particulate slot 204, particulate slots 204 are spirally staggered in a spaced manner along the length of bottom shell 200.

Second, still referring to FIG. 20 and as will be further described below, gas holes 208 provide an outlet for expulsion of gas-heavy fluid, as shown by arrow A3. Minimizing the entrainment of gas into the intake of the rotor and stator pumping components of ESPCP 12 lowers the probability of vapor lock, which can cause a loss of feed pressure to ESPCP 12 resulting in stalling or a loss of pumping power.

Referring to FIGS. 21-23, an exemplary embodiment of radial entry crossover 224 is illustrated. Referring specifically to FIGS. 21 and 22, radial entry crossover 224 is shown separated from and prior to installation within bottom shell 200 of ESPCP 12. Three spaced, radially outwardly-facing upper ports 236 are evenly circumferentially distributed near the top of radial entry crossover 224. Additionally, three circumferentially spaced lower ports 240 are evenly distributed near the bottom of radial entry crossover 224 and each face in a common clockwise or counterclockwise direction about the central axis of crossover 224. Lower ports 240 facilitate the continual upward flow of fluid through ESPCP 12 as represented by arrows A4 in FIG. 21. In particular, after passing through lower ports 240, fluid flows through vertical channels 244 defined between circumferentially spaced pairs of upper ports 236.

Referring to FIG. 23, radial entry crossover 224, when installed at the top of bottom shell 200, encircles the upper portion of inducer 216 and flex shaft 26 and encloses gas slinger 232, which is formed as the tapered cylindrical upper tip of inducer 216. Outwardly-facing upper ports 236 of crossover 224 are aligned with gas holes 208.

As fluid with entrained gas bubbles is pumped up and along the length of inducer 216 and into crossover 224, the rotation of inducer 216 will tend to centrifugally force the relatively heavier, liquid-heavy fluid outwardly toward shell 200 while the relatively lighter, gas-heavy fluid will remain inwardly adjacent inducer 216. In other words, the fluid having a greater proportion of liquid to gas bubbles (liquid-heavy portion) is directed radially outwardly and away from inducer 216 while the fluid containing a greater proportion of gas bubbles (gas-heavy portion) remains inwardly close to inducer 216. The liquid-heavy portion flows radially outwardly through lower ports 240 (shown by arrows A4) and thence upwardly through liquid channels 244 that direct fluid upward toward rotor-stator housing 152 and into the pumping mechanism of ESPCP 12. The gas-heavy portion flows upwardly past lower ports 240, remaining substantially within crossover 224, toward gas slinger 232. Gas slinger 232 directs the gas-heavy portion outwardly through upper ports 236 (shown by arrows A3) through gas holes 208 in shell 200. Further, since the area immediately outside of gas holes 208 of shell 200 has a lower pressure than the interior of crossover 224, the gas heavy fluid is further drawn outwardly through gas holes 208.

Referring to FIGS. 24-26, an exemplary embodiment of axial entry crossover 228 is illustrated. Referring specifically to FIGS. 24 and 25, axial entry crossover 228 is shown separated from and prior to installation within bottom shell 200 of ESPCP 12. Like radial entry crossover 224, three spaced, radially outwardly-facing upper ports 236 are evenly circumferentially distributed near the top of axial entry crossover 228. While axial entry crossover 228 lacks lower ports 240, upper ports 236 have circumferential gaps 248 along the walls of crossover 228 separating each respective pair of circumferentially adjacent upper ports, to facilitate the continual upward flow of fluid through ESPCP 12 as represented by arrows A4 in FIG. 26.

Referring to FIG. 26, axial entry crossover 228 is installed at the top of bottom shell 200 in substantially the same manner as radial entry crossover 224, except that axial entry crossover 228 is installed to create vertical separation D1 between the bottom axial entry crossover 228 and the top of rubber-lined interior 212 along bottom shell 200. As in radial entry crossover 224, outwardly-facing upper ports 236 align with gas holes 208.

As fluid with entrained gas bubbles is pumped up and along the length of inducer 216 and into crossover 228, the rotation of inducer 216 will tend to centrifugally force the liquid-heavy fluid outwardly toward shell 200, while the gas-heavy fluid remains inwardly close to rubber inducer 216. Vertical separation D1 helps channel the liquid-heavy fluid to avoid the interior of axial entry crossover 228 and continue (shown by arrows A4) toward rotor-stator housing 152 along circumferential gaps 248. The gas-heavy portion flows upward toward gas slinger 232. Gas slinger 232 directs the gas-heavy fluid outward through upper ports 236 (shown by arrows A3) and out through gas holes 208. Further, as in crossover 224, since the area immediately outside of gas holes 208 has a lower pressure than the interior of crossover 224, the gas-heavy fluid is further drawn outwardly.

Referring to FIGS. 27 and 28, either crossover 224 or 228 may include resilient gas barrier 252 within upper circular opening 256. Advantageously, gas barrier 252 may be made of a resilient material, such as rubber, for example, and provides a thin web that can be flexed or warped to accommodate large diameter rotors (as shown in FIG. 28). Further, gas barrier 252 forms a barrier that inhibits any gas which may remain entrained within the pumped fluid from moving upwardly through upper circular opening 256 of crossover 224 or 228 and into the pumping mechanism of rotor-stator housing 152.

While this invention has been described as having an exemplary design, the present invention may be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains.