Patent Application
20190353147
The invention relates to chemical injection pumps and methods of controlling pump output.
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.
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:
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:
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
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.
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.
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
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
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
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
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
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
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
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
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
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.
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.
| Number | Date | Country | |
|---|---|---|---|
| 62673635 | May 2018 | US |
