INJECTION PUMP

Abstract

A chemical injection pump system includes a reversible and controllable electric motor driving a cam wheel having a pressure ramp and a suction ramp, which rotates about an axis; and at least injection pump having a reciprocating plunger which is actuated by rotation of the cam wheel. The motor may be an outrunner brushless DC motor having a rotor which acts as the cam wheel, with an outer surface defining a cam profile having a pressure ramp and a suction ramp, which rotates about a stator axis. The system may be controlled to independently operate two or more injection pumps at different injection rates.

Description

FIELD OF THE INVENTION

The invention relates to chemical injection pumps and methods of controlling pump output.

BACKGROUND

During the production of oil and gas, it is often necessary to inject a treatment chemical into a well, particularly into the annular space between the well casing and production tubing. These chemicals might include demulsifiers, corrosion inhibitors, scale inhibitors, or paraffin inhibitors. The various chemicals and their intended effects are well known in the industry.

Rotary motors, typically electric or hydraulic motors, are used to power injection pumps which inject chemicals into a process. The motors are connected by a gearbox or transmission to a camshaft which reciprocates a plunger within a cylinder to pump fluid through an injection valve.

Control of the injection rate of such chemical pumps is conventionally controlled by varying the speed or duty cycle of the motor, or the stroke length and diameter of the piston, however, this does not always allow for precise control over injection rates and may be unduly complicated when dealing with multiple chemicals requiring different injection rates at different times.

SUMMARY OF THE INVENTION

In one aspect, the present invention relates to a positive displacement pump driven by an indexable, reversible electric motor. In preferred embodiments, the motor comprises an outrunner brushless DC (BLDC) electric motor. In preferred embodiments, the pump does not comprise a gearbox.

Thus, the invention may comprise a pump system comprising:

• • (a) an outrunner BLDC motor comprising a stator having a central axis and a rotor, wherein the rotor defines a cam profile having a pressure ramp and a suction ramp, which rotates about the stator axis; and
  • (b) at least one pump head comprising an injection pump having a reciprocating plunger which is actuated by rotation of the cam profile.

In some embodiments, the cam profile is created by a non-circular profile of the rotor. In alternative embodiments, the rotor has a circular profile but with an axis of rotation which is offset from the centre of the circle. Alternatively, the cam profile may be defined by a cam wheel, separate from the motor rotor.

In some embodiments, the pump system comprises at least two pump heads, radially arrayed around the rotor, wherein each pump head comprises a housing and a reciprocating plunger.

In some embodiments, the pump system further comprises a motor controller for controlling the speed and, optionally, direction of the motor. The motor controller may be configured to stroke one or more pump heads by cycling the cam profile or cam wheel backwards and forwards, over the entire pressure ramp, or a portion of the pressure ramp.

In another aspect, the invention may comprise a pump system comprising:

• • (a) a reversible and controllable electric motor driving a cam wheel having a pressure ramp and a suction ramp, which rotates about an axis; and
  • (b) at least one pump head comprising an injection pump having a reciprocating plunger which is actuated by rotation of the cam wheel.

In some embodiments, the reversible and controllable motor comprises an outrunner BLDC, a stepper motor or a servo motor. The motor is preferably an outrunner BLDC having a rotor with an outer surface which defines the cam wheel.

In another aspect, the invention comprises a method of actuating a reciprocating pump having a plunger, comprising the steps of

• • (a) providing a reversible and controllable electric motor driving a cam wheel having a pressure ramp and a suction ramp, which rotates about an axis;
  • (b) rotating the cam wheel to actuate the plunger.

In some embodiments, the reversible and controllable motor comprises an outrunner BLDC, a stepper motor or a servo motor. The motor is preferably an outrunner BLDC having a rotor with an outer surface which defines the cam wheel.

In one embodiment, the method is implemented to actuate two or more reciprocating pumps, arrayed radially around the circumference of the rotor. In one embodiment, the method comprises the further step of cycling the rotor backwards and forwards to stroke at least one pump on the pressure ramp.

In another aspect, the invention may comprise a control system for controlling a chemical injection rate for an injection pump comprising a suction valve and an output valve, comprising a mechanism for disabling operation of the suction valve or output valve, to maintain the suction valve in an open bypass position during the pressure stroke, or to maintain the output valve in an open bypass position during the suction stroke.

In one embodiment, the control system may be used in connection with any electrical motor and pump configuration, such as those conventionally used in chemical injection pumps or in connection with a BLDC motor as described herein.

In another aspect, the invention comprises a method of disabling a pump having a suction valve at its inlet and output valve at its outlet, comprising the step of opening the suction valve during a pressure stroke of the pump while keeping the output valve closed, or by opening the output valve during a suction stroke while keeping the suction valve closed.

In another aspect, the present invention comprises a control system comprising: a circuit control device for operative connection to an electric circuit comprising an electric motor for actuating a chemical injection pump; a processor operatively connected to the circuit control device; and a memory comprising a non-transitory tangible medium storing instructions readable by the processor to implement one or a combination of the methods as described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings shown in the specification, like elements may be assigned like reference numerals. The drawings are not necessarily to scale, with the emphasis instead placed upon the principles of the present invention. Additionally, each of the embodiments depicted are but one of a number of possible arrangements utilizing the fundamental concepts of the present invention.

FIG. 1A is a top plan view of one embodiment of the invention. FIG. 1B is a schematic representation of a motor controller.

FIG. 2 is a cross-sectional view along line II of FIG. 1.

FIG. 3 is a cross-sectional view along line III of FIG. 1.

FIG. 4 is another view of FIG. 2, showing offset axes.

FIG. 5 is another view of FIG. 2, showing indexed rotation over a portion of the rotor cam profile.

FIG. 6 is an exploded view of an alternative embodiment of the invention.

FIG. 7 is a vertical cross-section of the embodiment shown in FIG. 6.

FIG. 8 is another vertical cross-section along line VIII in FIG. 7.

FIG. 9 is a schematic view of an alternative embodiment having two pump heads arrayed at a 90 degree angle, with an offset circular cam wheel.

FIG. 10 is a graph showing sinusoidal pattern of a pump piston stroke compared to the rotation of the cam wheel of FIG. 9.

FIG. 11 is an exploded view of the embodiment of FIG. 6, having a suction valve deactivation system.

FIG. 12 is a top plan view of the embodiment of FIG. 11.

FIG. 13 is a vertical cross-section along line XIII of FIG. 12.

FIGS. 14A and 14B show details of a portion of FIG. 13, showing the actuator in an active and bypass position, respectively.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In one aspect, the invention may comprise a positive displacement pump comprising an outrunner brushless DC (BLDC) motor comprising a stator and a rotor, wherein the rotor defines an external cam profile. Rotation of the rotor/cam actuates at least one plunger which reciprocates to pump fluid in a conventional manner. This configuration may take advantage of the low RPM, high torque capability of an outrunner BLDC motor. No gearbox or transmission is required, and is specifically excluded in one embodiment of the invention.

In the following description, the terms “horizontal” and “vertical” are used to describe the relative orientation of elements of the invention in reference to the drawings, where FIG. 1 is a top plan view and FIGS. 2 and 3 are cross-sectional views of one embodiment along a vertical plane. FIG. 2 is taken in a transverse direction while FIG. 3 is taken in a longitudinal direction. The longitudinal horizontal axis is defined by the axis of rotation of the motor. When installed and in operation, the actual orientation of the motor and the pump may of course be different.

BLDC motors, also known as electronically commutated motors (ECMs or EC motors), or synchronous DC motors, are synchronous motors powered by DC electricity through an inverter or switching power supply which produces an AC electric current to drive each phase of the motor with a closed loop controller. The controller provides pulses of current to the motor windings that control the speed and torque of the motor. The structural elements of a brushless motor system are well known in the art, and are conventionally similar to a permanent magnet synchronous motor, but can also be a switched reluctance motor, or an induction (asynchronous) motor.

In some embodiments, the controller (300) may be configured to allow control injection rates for at least one injection pump, and preferably for two or more injection pumps, independently of each other. The controller may comprise a processor (302); a memory (304); an input device (306); and a circuit control device (308). The memory (304) stores a set of instructions that are readable by the processor (302) to implement a method of pump operation as is further described below. The memory (304) may be a read-write memory allowing the stored set of instructions to be modified or selected by the user. The input device (306) may be any computer hardware device that allows a user to input data to the processor (302). Non-limiting examples of an input device (306) include a keypad, a touch screen, or a pointing device such as a computer mouse used in conjunction with a display device. In one embodiment, under the control of the processor (302), the circuit control device (308) modifies the voltage and/or current applied to the electric motor, in accordance with a method of the present invention.

The term “outrunner” refers to a type of BLDC electric motor which spins its outer shell (rotor) around stationary windings (stator). Usually, outrunner motors have more poles, so they spin slower than their inrunner counterparts, while producing more torque.

In one embodiment, the system comprises a chemical injection pump comprising an outrunner BLDC motor (12), contained within a housing (10). The motor stator (13) is supported within the housing (10) by a spindle (8) which allows passage of electrical power and control wires. The rotor (14) is supported by bearings within the housing. One preferred feature of this system is that the rotor (14) is supported by only two bearings, at the front (15) and at the rear (17), which reduces friction and maintenance needs.

In one embodiment, the rotor (14) has an outer surface defining a cam profile with a non-uniform radius, as measured from the axis of rotation. In one embodiment, the outer cam profile comprises at least one lobe (16) which rotates about the central axis of the motor. In an alternative embodiment, the rotor (14) may define a cam profile with a non-uniform radius as a result of having an oval or other non-circular shape, or the rotor may be circular but with an offset axis of rotation. The rotor may have any configuration with a pressure ramp so long as rotation of the rotor is able to cause linear reciprocation of a plunger.

In alternative embodiments, the rotor may drive a separate cam wheel which defines an external cam profile or rotates eccentrically as required.

In the example shown in FIG. 2, two opposing pumps (18, 20) which are aligned in the vertical plane are actuated by the motor rotor (14). Each pump comprises a roller (22), a return spring (24), and a plunger (26). Rotation of the rotor (14) causes reciprocation of the plunger (26) by means of the roller (22).

As one skilled in the art may appreciate, the motor (12) may operate a plurality of pumps, which may be operated by the same rotor (and therefore be aligned in a vertical plane). Alternatively, or additionally, a plurality of rotor cams or cam wheels having the same axis of rotation (i.e. mounted on the same shaft) may be provided to operate pumps which are disposed horizontally adjacent to each other. Each rotor/cam or cam wheel may have one or more lobes or pressure ramps, which may operate in phase with other cam lobes or pressure ramps, or out of phase in varying degrees. As a result, the pump system may be configured with a wide range of output options.

In the example shown in FIGS. 1-3, a single cam lobe (16) on the motor rotor drives two horizontally opposed pumps (18, 20). By combining the output of the two pumps, a substantially continuous single rate injection may be achieved because the pressure ramp of the earn profile extends 180 degrees and increases linearly. The 180 degree arc of the rotor opposite the cam lobe is the base circle, and the plunger (26) of pump (20) does not reciprocate when on this portion of the cam. Through the 180 degree pressure ramp profile, the plunger of pump (18) moves to the top of its stroke, culminating at the peak of the pressure ramp (16A), followed by a shorter suction ramp (16B) to the base circle (16C). In alternative embodiments, the pressure ramp and the suction ramp may have different lengths and slopes. For example, in one embodiment, the pressure ramp and suction ramp may be of equal length.

In one alternative embodiment, the pressure stroke may be lengthened in duration by lengthening the pressure ramp, for example to 320 degrees. Such a cam profile would reduce motor torque requirement, maximize the flow time and create longer periods of constant flow.

In other embodiments, the effective slope of the pressure ramp and/or the suction ramp may be non-linear.

In one embodiment, as shown in FIG. 4, the rollers and the axis of the pump are offset from the centreline (C) of the drive axis, which reduces or eliminates side loading on the plunger drive mechanism. As may be seen in FIG. 3, the pump axes (P1 and P2) are both slightly offset from the drive axis centreline (C), minimizing off-axis forces on the roller and pump components.

BLDC motors are reversible and highly controllable with conventional motor controllers. The motor may be indexable with rotational index or position information provided by a shaft encoder or the like, or by using a load profile. As a result, a pump may be stroked by cycling the rotor back and forth, as opposed to continuous rotation in one direction. In the embodiment shown in FIG. 5, if the rotor (14) is cycled back and forth from the position shown, the left hand pump (18) will be actuated, while the right hand pump (20) will not be actuated. The cycle may comprise the 180 degree phase of the pressure ramp, or some portion of it, for example, a 90 degree portion illustrated in FIG. 5 as arc “A”. In this manner, the pump heads may be independently controlled to vary flow rate. This may be particularly useful if the two pump heads pump different chemicals, and the injection rates of each are desired to be different, or different at different times. In other embodiments, the other pump head may be positioned differently or with a differently configured rotor cam profile, to be actuated at a lower injection rate.

The advantages of stroking a pump by cycling a rotor back and forth may be also realized by using a motor other than a BLDC motor. For example, stepper motors or servo motors are also reversible and conveniently controllable and may be used to drive a cam wheel with the desired cam profile.

An alternative embodiment is shown in FIGS. 6-8. In this example, the motor (112) has the same outrunner configuration with a stator (113) and rotor (114). In this example, the rotor (114) does not have a cam profile, but rotates a spindle (116) which extends into a pump drive housing (118) and an eccentric cam wheel (120). The pump drive housing bolts to the motor housing (110) as shown. In this example, the cam wheel (120) is circular, but is mounted to the spindle (116) in a offset manner, resulting in eccentric rotation of the cam wheel (120) within the housing (118).

Opposing pump heads (101) and (102) comprise plungers (122, 124) which extend outwards and operate in conjunction with suction and output valves (126, 128), which may be ball valves, to open and close the injection fluid path, in a conventional manner. During the suction stroke, fluid is drawn into the pump through the suction valve, and expelled during the pressure stroke through the output valve. Single or multiple pump variations are of course possible. Rotation of the eccentric cam wheel (120) results in separate actuation of the pump heads (101, 102), each being stroked in a sinusoidal pattern. Because the two pump heads are 180 degrees opposed, the two sinusoidal patterns will be 180 degrees out-of-phase.

In a further alternative embodiment, as illustrated in FIG. 9, the two pump heads (101, 102) may be spaced at 90 degrees apart, resulting in sinusoidal patterns that are 90 degrees out-of-phase, as is illustrated in FIG. 10. Of course, it is possible to use this configuration, or a similar configuration, to independently vary the injection rate of two or more pump heads with one electric motor. In this case, as shown in FIG. 10, a range of rotation angle exists where there is maximum differential between the pump strokes and the rotation angle of the cam wheel (cam). If the motor is cycled back and forth in this range of rotation angle, a large difference in injection rates between the two pump heads can be realized.

In some embodiments, two or more cam wheels, having non-aligned eccentricities, may be mounted to the same spindle, and actuate different pump heads.

In a preferred embodiment, the rotor/spindle assembly is supported by two bearings only, a front bearing (115) positioned adjacent the cam wheel (120) in the pump drive housing (118), while a rear bearing (117) is positioned at the rear of the spindle (116), adjacent the stator (113).

In another aspect, the invention comprise a method and system for controlling a pump, for example, to vary its injection rate. In one embodiment, this may permit independent operation of one pump head, from another pump head driven by the same motor. In this case, the motor and pump configuration may as described herein, or may be a conventional chemical injection pump configuration using any known motor and pump, provided the pump comprises a suction valve on its intake and an output valve on its output.

In one embodiment, shown schematically in FIGS. 11-14, a rotor (114) actuates two opposing pump heads (101, 102), as described above. However, one or both of the pump heads (101) may be adapted with a control system (200) which is configured to modulate one or both of the suction valve or the output valve, in order to disable fluid injection by that pump head. This may be implemented by the motor controller as part of its control options.

In normal operation, the plunger (124) will draw fluid into the pump chamber (202) during its suction stroke. The suction side has a check valve ball (204) which is unseated off its valve seat (206) by the pressure differential, allowing fluid to flow into the pump chamber (202) while the output valve (210) remains closed. A suction valve return spring (208) biases the suction valve in a closed position: The output valve (210) may also comprise check valve ball (212) which is also biased in a closed position with spring (214), and which opens with the pressure generated by the pressure stroke. During the pressure stroke, the fluid drawn into the pump chamber (202) is discharged through the output valve, while the suction ball check valve remains seated and closed.

This normal operation of the pump may be disabled or modulated by force opening or force closing either valve during either the pressure stroke or the suction stroke. For example, force opening the suction valve during the pressure stroke or force closing the suction valve during the suction stroke will impair fluid pumping. Alternatively, force opening the output valve during the suction stroke, or force closing the output valve during the pressure stroke will also impair fluid pumping.

In general terms, in one embodiment, the control system (200) is used to disable the suction valve by keeping it open during the pressure stroke of the pump. As a result, the volume of fluid within the pump chamber simply flows back into the suction line (220) as the output valve (210) remains closed.

In one embodiment, the suction valve is kept open by physically blocking it from seating in its valve seat (206). In a preferred embodiment, a pin (230) protrudes upward through the valve seat opening, and may be extended or retracted by a pin actuating mechanism comprising a ferromagnetic armature (232) and an solenoid coil (234). Optionally, the pin is biased in an upward position within the armature (232) by a coil spring (236) In FIG. 12A, the pin is shown in its retracted position (valve active), which allows the valve ball (204) to seat normally. Upward movement of the armature (232) allows spring (236) to push the pin (230) upwards and off its valve seat (206), thereby disabling the suction valve. The armature is moved upwards by energizing the solenoid coil (234).

In one embodiment, the pin is biased into a normally retracted position, allowing normal operation of the suction valve (valve active). Alternatively, the pin may be biased into a normally extended position, in which case the suction valve is disabled (valve bypass).

In an alternative embodiment, the output valve may be disabled, for example by keeping it in an open position during suction stroke. In one embodiment, a switchable magnet (not shown) may hold the check valve ball (212) open. As a result, fluid in the output line will be drawn back into the pump, while the suction valve will fail to open because of a lack of pressure differential.

Definitions and Interpretation

References in the specification to “one embodiment”, “an embodiment”, etc., indicate that the embodiment described may include a particular aspect, feature, structure, or characteristic, but not every embodiment necessarily includes that aspect, feature, structure, or characteristic. Moreover, such phrases may, but do not necessarily, refer to the same embodiment referred to in other portions of the specification. Further, when a particular aspect, feature, structure, or characteristic is described in connection with an embodiment, it is within the knowledge of one skilled in the art to affect or connect such module, aspect, feature, structure, or characteristic with other embodiments, whether or not explicitly described. In other words, any module, element or feature may he combined with any other element or feature in different embodiments, unless there is an obvious or inherent incompatibility, or it is specifically excluded.

It is further noted that the claims may be drafted to exclude any optional element. As such, this statement is intended to serve as antecedent basis for the use of exclusive terminology, such as “solely,” “only,” and the like, in connection with the recitation of claim elements or use of a “negative” limitation. The terms “preferably,” “preferred,” “prefer,” “optionally,” “may,” and similar terms are used to indicate that an item, condition or step being referred to is an optional (not required) feature of the invention.

The singular forms “a,” “an,” and “the” include the plural reference unless the context clearly dictates otherwise. The WI “and/or” means any one of the items, any combination of the items, or all of the items with which this term is associated. The phrase “one or more” is readily understood by one of skill in the art, particularly when read in context of its usage.

Claims

1. A pump system comprising:

(a) an outrunner brushless DC motor comprising a stator and a rotor wherein the rotor has an outer surface defining a cam profile having a pressure ramp and a suction ramp, which rotates about the stator axis; and

(b) at least one pump head comprising an injection pump having a reciprocating plunger which is actuated by rotation of the cam profile.

2. The pump system of claim 1 wherein the outer cam profile is created by a non-circular profile of the rotor.

3. The pump system of claim 1 wherein the rotor has a circular profile but has an offset axis of rotation.

4. The pump system of claim 1 comprising at least two pump heads, radially arrayed around the rotor.

5. The pump system of claim 1, further comprising a motor controller for controlling the speed and/or direction of the motor.

6. The pump system of claim 5 wherein the motor controller is configured to stroke at least one pump head by cycling the rotor backwards and forwards, over the entire pressure ramp, or a portion of the pressure ramp.

7. The pump system of claim 4 further comprising a motor controller for controlling the speed and/or direction of the motor and wherein the motor controller is configured to stroke one pump head by cycling the rotor backwards and forwards, over the entire pressure ramp, or a portion of the pressure ramp, while the other pump head is not actuated, or actuated at a lower injection rate.

8. The system of claim 1 wherein the pressure ramp comprises about 180 degrees of rotation of the rotor.

9. The system of claim 8 wherein the portion of the rotor which is not the pressure ramp comprises a base circle.

10. A pump system comprising:

(a) a reversible and controllable electric motor driving a cam wheel having a pressure ramp and a suction ramp, which rotates about an axis; and

(b) at least one pump head comprising an injection pump having a reciprocating plunger which is actuated by rotation of the cam wheel.

11. The pump system of claim 10 wherein the reversible and controllable motor comprises an outrunner BLDC, a stepper motor or a servo motor.

12. The pump system of claim 10 comprising two or more pump heads, and a cam wheel configured to operate a first pump head out of phase with another pump head.

13. The pump system of claim 12 wherein the two or more pump heads are arrayed at a 90 degree angle or an 180 degree angle from each other, and the cam wheel is circular with an offset axis of rotation.

14. The pump system of claim 12 comprising a motor controller configured to stroke one pump head by cycling the rotor backwards and forwards, over the entire pressure ramp, or a portion of the pressure ramp, while the other pump head is not actuated, or actuated at a lower injection rate.

15. A method of actuating a reciprocating pump having a plunger, comprising the steps of

(a) providing a reversible and controllable electric motor driving a cam wheel having a pressure ramp and a suction ramp, which rotates about an axis;

(b) rotating the cam wheel to actuate the plunger.

16. The method of claim 15 wherein the reversible and controllable motor comprises an outrunner BLDC, a stepper motor or a servo motor.

17. The method of claim 16 wherein the motor is an outrunner BLDC having a rotor which defines the cam wheel or which drives the cam wheel.

18. The method of claim 15 which actuates two or more reciprocating pumps, arrayed radially around the circumference of the cam wheel.

19. The method of claim 15 comprising the further step of cycling the motor backwards and forwards to stroke at least one pump on the pressure ramp.

20. The method of claim 19 wherein the motor is cycled backwards and forwards to stroke a first pump over the entire pressure ramp, or a portion of the pressure ramp, while a second pump is not actuated, or actuated at a lower injection rate.

21. A chemical injection pump system comprising an injection pump having a suction valve and an output valve, the system comprising a mechanism configured to disable normal operation of one or both of the suction valve or the output valve, to reduce or eliminate fluid output of the pump.

22. The system of claim 21 wherein the mechanism is configured to maintain the suction valve in an open bypass position during a pressure stroke, to maintain the suction valve closed during a suction stroke, to maintain the output valve open during a suction stroke, and/or to maintain the output valve closed during a pressure stroke.

23. The system of claim 22 wherein the mechanism comprises a pin moveable between an extended position where it interferes with seating of the suction valve, and a non-interfering retracted position, and a ferromagnetic armature and a solenoid coil for actuating the pin.

24. A method of disabling a chemical injection pump having a suction valve at its inlet and output valve at its outlet, comprising the step of disabling normal operation of either the suction valve or the output valve.

25. The method of claim 24 wherein normal operation is disabled by opening the suction valve during a pressure stroke of the pump while keeping the output valve closed.