Active valve system for positive displacement pump
An active valve system may be used to improve operation of the suction valve(s) of a positive displacement pump. As appropriate, the active valve system may apply a force to the suction valve directed to open and/or close the suction valve. By quickening the opening and/or closing of the suction valve, the pump may run at a higher speed and operate with less wear. Additionally, the active valve system may allow all suction valves of a pump to be held open for various purposes.
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FIELD OF THE INVENTIONEmbodiments described herein relate to positive displacement pumps, and more specifically to devices and methods to improve the efficiency, durability, performance, and operating characteristics of reciprocating positive displacement pumps (of the sort that might be used in pumping wellbore servicing fluids) by actively operating the suction valve(s) of the pump.
BACKGROUNDPositive displacement pumps, and specifically reciprocating pumps, are used in all phases of oilfield operation to pump water, cement, fracturing fluids, and other stimulation or servicing fluids. Pumps in oil field operations often endure harsh conditions, especially when pumping abrasive fluids (such as fracturing fluids). Thus, there is an ongoing need for improved pumps and methods of operation for pumps, allowing for more effective oil field pumping operations in the face of such harsh operating conditions.
SUMMARYIn one aspect, the present disclosure is directed to a device comprising a reciprocating pump having a suction valve through which fluid is drawn into a chamber during a suction stroke in order to be discharged from the pump during a discharge stroke; and an active valve system (typically including an active valve train and often also including a sensor for pump stroke position and a controller) operable to provide force to operate the suction valve. The device may further comprise a timing marker indicative of pump stroke, a sensor operable to detect the timing marker, and a controller operable to activate the active valve train based on the sensed pump stroke. Further, the active valve train may comprise a cylinder with a rod, with the rod connected to or in contact with the suction valve. The active valve train may provide a force directed to open the suction valve prior to or shortly after the suction stroke begins. Alternatively, in embodiments that pre-load the suction valve to open, the active valve train may provide a force directed to open the suction valve during the discharge stroke. Typically, the reciprocating pump further comprises a suction valve spring (closure member) operable to provide force to close the suction valve. The suction valve spring (closure member) may close the suction valve prior to the discharge stroke.
In one embodiment, the suction valve spring (closure member) is sufficiently stiff to minimize valve float as the suction valve closes. The force provided by the active valve train may be greater than the closing force exerted by the suction valve spring (closure member). Additionally, as pressure in the chamber varies during the suction and discharge strokes, the force provided by the active valve train may be less than the closing force exerted by the suction valve spring (closure member) in conjunction with the pressure in the chamber during the discharge stroke. Alternatively, as pressure in the chamber varies during the suction and discharge strokes, the force provided by the active valve train may be less than the force exerted by the suction valve spring (closure member), but sufficient in conjunction with the pressure in the chamber during the suction stroke (such as the pressure differential between the high pressure suction header and the low pressure chamber, for example) to open the suction valve quickly enough to minimize cavitation. The active valve train may release the opening force prior to the discharge stroke. Thus, the active valve train may provide a force directed to open the suction valve during the discharge stroke, and may then release the opening force prior to the discharge stroke.
In an alternative embodiment of the device, the suction valve spring (closure member) may be insufficiently stiff to close the suction valve quickly enough to minimize valve float on its own, and the active valve train may provide a force directed to assist in opening the suction valve and a force directed to assist in closing the suction valve. Then, the force of the suction valve spring (closure member) in conjunction with the closing force provided by the active valve train would typically be sufficient to close the suction valve quickly enough to minimize valve float. Often, the suction valve connects to a fluid header operable to deliver fracturing fluid and the like to the pump for discharge into a well bore. The pump may also be mobile, with the pump being transported via a motorized vehicle, and the pump possibly being powered by the engine of the motor vehicle. In another embodiment in which there is no suction valve spring (closure member), the active valve train may provide a force directed to open the suction valve and a force directed to close the suction valve (actively operating the opening and closing of the suction valve entirely on its own).
In another aspect, the present disclosure is directed to a method for bringing online a reciprocating pump having multiple chambers each with a suction valve and a plunger driven through a suction stroke and a discharge stroke by a common crankshaft, the method comprising actively opening the suction valves of all cylinders and holding the suction valves open; bringing the crankshaft up to operating speed; and releasing the suction valves to bring the pump online. The suction valves may be released sequentially (such as one at a time, for example). Additionally, the suction valves may each be released at or near the end of the discharge stroke (when the plunger is fully extended and there is maximum mechanical advantage). The suction valves typically would be released when the crankshaft speed is sufficiently high to provide adequate torque from the engine, motor, or other prime mover to start the pump (as the pump can only start operating once the engine's torque is sufficient to overcome the discharge pressure).
In one embodiment, the method may further comprise priming the pump (before normal operation), which may further include actively holding the suction valves open during suction stroke to minimize the pressure drop across the suction valve until each chamber fills completely during the suction stroke. Additionally, the method may further comprise actively opening each suction valve prior to its chamber's suction stroke, and releasing each suction valve prior to its chamber's discharge stroke (once the pump is functioning normally at operating speed). This may require sensing the timing for each suction stroke and discharge stroke. The method may further comprise charging the cylinder during the suction stroke; closing the suction valve prior to the discharge stroke; and discharging the cylinder during the discharge stroke. The suction valve may automatically be closed at or near the end of the suction stroke (prior to the discharge stroke) by a suction valve spring sufficiently stiff to minimize valve float. Alternatively, when the closing of the suction valve operates by a suction valve spring, the method may further comprise actively assisting the closing of the suction valve at or near the end of the suction stroke in order to minimize valve float. In one embodiment, the method further comprises connecting the suction valve to a source of fracturing fluid and/or pumping fracturing fluid into a well bore.
In yet another aspect, the present disclosure is directed to a method for actively assisting the opening of a suction valve in a reciprocating pump having a suction stroke and a discharge stroke, the method comprising providing a spring operable to close the suction valve prior to each discharge stroke; actively applying an opening force to the suction valve during each discharge stroke (and actively holding the suction valve open during the suction stroke by maintaining the opening force on the suction valve); and releasing the opening force prior to each discharge stroke. In one embodiment, the method further comprises sensing the timing of the pump stroke. The spring may provide a closing force sufficient to close the suction valve fast enough to minimize valve float. The pump may further comprise a chamber in which the pressure varies during suction and discharge strokes; and the opening force actively applied may be greater then the spring closing force, but less than the spring closing force in conjunction with the pressure in the chamber during the discharge stroke.
In still another aspect, the present disclosure is directed to a method of servicing a wellbore with a servicing fluid (e.g., a fracture fluid) using a reciprocating pump having multiple chambers each with a suction valve and a discharge valve and operable to provide a suction stroke and a discharge stroke, the method comprising connecting each suction valve to a source of wellbore servicing fluid; connecting each discharge valve to the wellbore; providing a force to actively open each suction valve prior to the suction stroke of its chamber; charging each chamber with wellbore servicing fluid during its suction stroke; releasing the opening force on each suction valve prior to the discharge stroke of its chamber; and discharging wellbore servicing fluid from each chamber during its discharge stroke and into the wellbore. When the suction stroke and discharge stroke of each chamber is driven by a common crankshaft, the method may further comprise sensing the timing of the suction stroke and the discharge stroke based on rotation of the crankshaft. Each suction valve may also be opened sufficiently fast to minimize cavitation.
In an embodiment, the method may further comprise providing a force for closing the suction valve of each chamber prior to its discharge stroke. Each suction valve may then be closed sufficiently fast to minimize valve float. The method may further comprise providing one or more springs operable to close the suction valve of each chamber prior to its discharge stroke (with the springs providing the closing force). In one embodiment, the opening force provided to actively open each suction valve prior to the suction stroke of its chamber is greater than the closing force provided to close the suction valve of each chamber prior to its discharge stroke. In another embodiment, the pressure in the chamber varies during the suction and discharge strokes; and the opening force provided to actively open each suction valve prior to the suction stroke of its chamber is less than the closing force provided to close the suction valve of each chamber prior to its discharge stroke, but is sufficient in conjunction with the pressure in the chamber during the suction stroke to open the suction valve quickly enough to minimize cavitation.
In still another embodiment, the method may further comprise actively holding all suction valves open to prime the pump. Alternatively, the method may further comprise actively holding all suction valves open during start-up; bringing the pump up to operating speed; and releasing one or more suction valves to bring the pump online. The suction valves may be released sequentially. Further, the engine may have sufficient torque at operating speed for start-up (so that the engine may be brought up to operating speed to have sufficient torque to bring the pump online during start-up). The suction valves also may be released at or near the end of the discharge stroke to take advantage of maximum mechanical advantage.
In another embodiment, a method of pumping wellbore servicing fluid comprises sensing the position of a reciprocating pump stroke and actively assisting the opening, closing or both of a suction valve in response to the sensed position of the pump stroke. In an embodiment, the active assistance applies a force to overcome a static or passive force applied to the suction valve, for example a static or passive force applied by a biasing spring or other closure device.
In still another aspect, the present disclosure is directed to a method for draining a pump having multiple chambers each with a suction valve and a plunger driven through a suction stroke and a discharge stroke, the method comprising actively opening the suction valves of all cylinders (all suction valves); holding all suction valves open as the pump runs/is driven (or as the plunger cycle through suction and discharge strokes); and running/driving the pump so that each plunger goes through multiple suction and discharge strokes. In one embodiment, the method may further comprise flushing fluid out of the pump (specifically the chambers and the suction valves). In another embodiment, the method may further comprise sucking air in and out of each chamber through the open suction valves in order to dry the pump. Typically this draining, cleaning, and drying technique would be used at the end of a pumping process/job, after fluid pumping is completed. In yet another embodiment, the method further comprises closing all suction valves and stopping running/driving the pump.
In yet another aspect, the present disclosure is directed to a method for varying the available displacement of a pump having multiple chambers each with a suction valve and a plunger driven through a suction stroke and a discharge stroke, the method comprising running/driving the pump so that each plunger cycles through suction and discharge strokes; actively opening one or more suction valves and holding the one or more opened suction valves open (throughout both suction and discharge strokes); and continuing to run/drive the pump (with the plungers cycling through suction and discharge strokes). When running the pump while one or more suction valves are held open, only the cylinders whose suction valves are not being held open will actually pump fluid (be on line). Actively opening and holding one or more suction valves open serves to drop the cylinders associated with the one or more opened suction valves out of active pumping/pumping operation (so that the pump acts as a pump having fewer cylinders/less fluid displacement). This allows the pump to pump fluid at a rate less than possible if all cylinders are pumping (with suction valves opening and closing in time with the suction and discharge strokes). In fact, dropping cylinders out of use allows the pump to pump fluid at a rate less than it would be able to even if the engine driving the pump were operating at its lowest speed (in first gear) with all cylinders operating/pumping. It may also provide more precise control of the pump/flow rate (by offering smaller intervals of available displacement).
In another aspect, the present disclosure is directed to a method for quickly stopping fluid pumping by/fluid flow through a pump having multiple chambers each with a suction valve and a plunger driven through a suction stroke and a discharge stroke, the method comprising running/driving the pump so that each plunger cycles through suction and discharge strokes; actively opening all suction valves (the suction valves of all chambers) and holding the suction valves open as the plungers continue to cycle through suction and discharge strokes. In one embodiment, the method further comprises stopping the pump (stopping driving the plungers). By holding all suction valves open (even as the plungers continue to move), the fluid flow rate through the pump drops nearly instantaneously to zero (fluid ceases to be pumped nearly instantaneously). This provides the possibility of a fast/emergency/safety stop of fluid pumping, despite the inertia of the pump elements (such as the plungers). In effect, opening all of the suction valves serves as a safety stop/quick kill. In an embodiment, the method further comprises holding the suction valves open until the pump stops running (i.e. the plungers stop moving/cycling).
For a more complete understanding of the present disclosure, and for further details and advantages thereof, reference is now made to the accompanying drawings, wherein:
Disclosed embodiments demonstrate an active valve system for assisting or providing the operation of the suction valve(s) of a positive displacement pump. In the disclosed embodiments shown in the figures, the active valve system provides active operation of the suction valve(s) of a reciprocating positive displacement pump (providing a force directed to open and/or close the suction valve). The active valve system may often be configured to provide a force directed to open the suction valve(s) in a controlled manner, so that the opening force is applied to the suction valve(s) at the appropriate time in the pump stroke cycle for opening of the suction valve(s), with the opening force then released/removed from the suction valve(s) at the appropriate time in the pump stroke cycle to allow for closing of the suction valve(s). While the active valve system may provide the sole means for opening and/or closing the suction valve(s), often it would be used in conjunction with other forces (such as pressure differentials and/or springs, by way of non-exclusive example) to assist in opening and/or closing the suction valve(s) of a reciprocating pump.
Using an active valve system, it may be possible to both quickly open and quickly close the suction valves(s). For instance, a stiff suction valve spring (providing a strong closing force to quickly close the suction valve) may be used, while the active valve system may apply an opening force at the appropriate time to quickly open the suction valves(s) (despite the stiff suction valve spring). As another possible alternative, a weak suction valve spring (allowing for quick opening of the suction valve) may be used, while the active valve system may apply a closing force at the appropriate time to assist in quickly closing the suction valve. By improving the opening and/or closing of the suction valve(s), the active valve system may improve the operating efficiency and lifespan of reciprocating pumps. Additionally, the active valve system may be used for other purposes. By way of example, the active valve system may aid in bringing a pump online (especially if it is facing back pressure), in priming the pump, in making transmission shifts (by selectively disabling chambers during a shift sequence), and in draining the pump.
While
The pump 200 of
Rather than using a sensor 257 with a controller 259 to determine activation of the active valve train 250, the active valve system could alternatively employ a mechanical, electrohydraulic, pneumatic, electric, or other linkage coupling the movement of the active valve train 250 directly to the movement of the crankshaft 210. In such an embodiment, the active valve train 250 would act on the suction valve 237 based directly on the position of the plunger 220. While such alternative active valve systems are feasible, using a mechanical linkage may restrict alternative uses of the active valve system, for example embodiments requiring the ability to hold suction valves open throughout both suction and discharge strokes.
In
In
In the example set forth in
In operation, sensor 257 of
So in operation, the suction stroke of the pump 200 in
Additionally, however, as the sensor 257 detects the end of a discharge stroke and the beginning of a suction stroke, the controller 259 activates the active valve train 250, providing an additional force directed to open the suction valve 237. In
When the suction stroke ends and the discharge stroke is about to begin, pressure in the chamber 230 should be approximately the same as the pressure in the fluid chamber 260. Thus, the suction valve spring's 235 closing force on the suction valve 237 would only be resisted by the opening force applied by the active valve train 250. Before the discharge stroke begins, the controller 259 of
In the example of
During the discharge stroke, fluid pressure in the chamber 230 increases throughout the discharge stroke as the plunger 220 extends (since both the suction valve 237 and the discharge valve 239 are closed). Pressure now assists in keeping the suction valve 237 closed (although the suction valve spring 235 would generally be sufficiently strong on its own), and when the pressure becomes sufficiently high to overcome the closing force of discharge valve spring 243 and discharge line pressure, the discharge valve 239 opens and pumps fluid out of the chamber 230 under pressure. Once the discharge stroke has ended and the following suction stroke is about to begin, the cycle starts over and repeats, with the discharge valve 239 closing (since there is insufficient pressure in the chamber 230 to overcome the discharge valve spring 243 and discharge line pressure biasing the discharge valve 239 closed), the active valve train 250 applying a force directed to open the suction valve 237, the pressure (of the partial vacuum) in the chamber 230 applying an opening force on the suction valve 237, the suction valve spring 235 compressing, and the suction valve 237 opening as the suction stroke begins.
The amount of opening force applied by the active valve train 250 can vary depending on design factors and/or need. If the active valve train 250 is designed to merely assist the chamber pressure in opening the suction valve 237 by reducing the effective stiffness of the suction valve spring 235 during the suction stroke (so that the suction valve spring 235 acts as a stiff spring to close the suction valve 237 prior to the discharge stroke, but acts as a weak spring when the suction valve 237 is being opened prior to, after, or as the suction stroke due to the opening force applied by the active valve train), then the opening force of the active valve train 250 would be less than the closing force exerted by the suction valve spring 235. In such a case, the opening force provided by the active valve train 250 would only be sufficient to overcome the suction valve spring's 235 closing force and/or to open the suction valve 237 quickly enough to minimize cavitation and wear when it was used in conjunction with the chamber pressure (pressure differential) during the suction stroke.
Alternatively, the active valve train 250 could be designed to provide a powered opening. In such a case, the active valve train 250 would apply an opening force greater than the suction valve spring's 235 closing force to the suction valve 237, in an attempt to drive the suction valve 237 open quickly. It may be beneficial to cap the opening force provided by the active valve train 250, however, so that it does not exceed the closing force of the suction valve spring 235 plus the chamber pressure during the discharge stroke (with the high pressure in the chamber providing an additional closing force on the suction valve). This precaution would prevent early opening of the suction valve 237 in case the active valve train 250 was activated during the discharge stroke (as will be discussed below in one alternative embodiment). Alternatively, the active valve train 250 may apply an opening force greater than the suction valve spring's 235 closing force in conjunction with the chamber pressure force to the suction valve 237, allowing a powered opening at any time during the pump operation/cycle (even during the discharge stroke).
While the embodiment shown in
In another alternative embodiment, the active valve train 250 could operate to provide both an opening force and a closing force on the suction valve 237. In such an instance, the active valve train 250 would apply an opening force prior to the suction stroke (and as described above, this could include application during the discharge stroke), and would apply an active closing force to the suction valve 237 prior to the discharge stroke (rather than simply releasing the opening force). This type of two-way active valve operation might also allow the use of a weak suction valve spring 235 (since the suction valve spring 235 would be assisted in closing the suction valve 237 quickly). Thus, while a weak suction valve spring 235 might be insufficiently stiff/strong to close the suction valve 237 quickly enough to minimize valve float on its own, when used in conjunction with a closing force applied prior to the discharge stroke by the active valve train 250, valve float could still be minimized.
Alternatively, such two-way active valve operation could allow the suction valve spring 235 to be completely eliminated (with the active valve train 250 then providing both the opening and the closing force on the suction valve 237). In such a case, the closing force would need to be sufficient alone to close the suction valve 237 quickly enough to minimize valve float. This variant may be disfavored, however, since it would not provide fail-safe operation of the pump 200 in case of failure of the active valve train 250. Rather, it is preferred to use a stiff suction valve spring 235 with an active valve train 250, so that the suction valve spring 235 may act as a fail-safe (allowing the pump 200 to continue operation, although less efficiently, even if the active valve train is unavailable).
The pump 200 of
When used for wellbore servicing, the pump 200 is often used to pump an abrasive fluid, such as fracture fluid that may contain sand or other proppants/abrasives. This tends to increase wear concerns for pump components, making the benefits of the active valve system even more important. Typically, the discharge valve 239 of the pump 200 would be attached in fluid communication to the wellbore, so that fracture fluid supplied to the pump 200 via a fluid header 260 (leading to a fluid source, such as a tank) may be pumped into the wellbore under pressure. The fracture fluid from the fluid header 260 enters the pump 200 through the suction valve 237 during the suction stroke, and is discharged out the discharge valve 239 during the discharge stroke. As discussed above, the active valve system allows for quick opening and closing of the suction valve 237, such that fracturing fluid may be pumped into the wellbore without substantial wear on the pump 200. In addition to increasing the service life of the pump 200, the active valve system may allow the pump 200 to operate effectively at higher speeds (by allowing the suction valve 237 to open and close more quickly, so that the pump stroke speed may be increased). Thus pump efficiency and output may also be improved.
Additionally, the chamber 230 of a pump 200 used for wellbore servicing could be susceptible to damage due to compression of incompressible materials. This could be a problem, especially when pumping fracture fluid, since the fluid may include solids (such as proppant). To address this concern, the chamber 230 may be sealed at one end (opposite the plunger 220) with an end cap 275. The end cap 275 generally closes the chamber, but it is designed as a plug that may shear off and open the chamber if too much incompressible material fills the chamber (preventing damage to the pump from extreme pressure buildup).
In addition to improving pump efficiency and reducing pump wear, an active valve system may also provide other benefits, by allowing for control of suction valve(s) independent of the pump stroke. By way of example, the active valve system could also be used to assist in bringing a pump online during start-up. It can be challenging to bring a pump online against high pressure, due to the torque curve characteristics typical of an engine. More specifically, engines tend to provide very low torque at low speeds (RPMs), and only provide significant torque levels above a certain speed. So during start-up, as the pump begins to slowly operate, it can be difficult for the engine to generate sufficient torque to overcome resistance. An active valve system may be used to help bring pumps online in such challenging circumstances.
Recall that while the discussion above regarding
So during start-up, it may be difficult to get an engine driving the pump up to operating speed. Using an active valve system, however, the suction valves of all cylinders of the pump may be held open during start-up, reducing start-up torque resistance. This basically allows the engine and/or pump to be brought up to operating speed without any load acting as resistance, and then once the pump's inertial mass is in motion at operating speed, such that the engine is capable of generating sufficient torque to overcome resistance, the suction valves may be released to bring the pump online (so that it begins actual pumping of fluid). By bringing the crankshaft up to speed without a load, the pump can be brought online once the engine is operating at a speed capable of generating sustainable torque.
Thus, a pump may be brought online using an active valve system by first opening all of the pump's suction valves, and then starting to cycle the pump (through suction strokes and discharge strokes) while the suction valves are actively held open. In other words, the crankshaft is brought up to operating speed (often by starting and engaging an engine or motor for powering the crankshaft) while the suction valves are actively held open (so that the pump experiences no load/resistance). Fluid is sucked into each chamber through the suction valve during its suction stroke, and forced out of each chamber through the suction valve during its discharge stroke (since the suction valve for the chamber is being held open and the discharge valve is closed, since the chamber pressure would be too low to overcome the discharge valve spring while the suction valve is open). Thus, during start-up, fluid would basically slosh back and forth across the suction valve(s). The effect of holding the suction valves open is akin to placing the pump in neutral (since the pump does not have to generate pumping pressure to discharge fluid through the discharge valve). This lowers the resistance that the pump experiences during start-up, allowing the engine and/or pump to be brought up to operating speed. Once at operating speed, the engine is capable of generating sufficient torque to begin actually pumping fluid (overcoming the pressure/resistance), and the suction valve(s) may be released to bring the pump online.
Furthermore, the suction valves may be sequentially released, allowing for example one chamber of the pump to come online at a time in order to provide a soft-start for the pump. The process of bringing a pump online with the assistance of an active valve system may be further improved by releasing the suction valves when their plungers are at full extension (approximately at the end of a discharge stroke), in order to take advantage of the maximum mechanical advantage. So again, all the suction valves would be held open as the pump is brought up to speed. Once the engine reaches an operating speed where it can achieve full torque (or at least sufficient torque to overcome pressure/resistance), the suction valves that are being held open could then be released as their corresponding plungers reach full extension (late in the displacement stroke), and the suction valves would operate as normally (opening for the suction stroke, with the active valve system perhaps providing an opening force, and closing for the displacement stroke, with the active valve system perhaps providing a closing force as well).
The active valve system could also be used to aid in priming the pump. Actively holding the suction valves wide open during the suction stroke reduces pressure drop across the suction valve and allows the pump to take on fluid while minimizing the expansion of any gas in the chamber. This minimizes the chance of vapor locking.
Additionally, an active valve system may be used to float suction valves during transmission shifts, as a way to reduce the load on the pump. During transmission shifts (of the motor or engine used to power the crankshaft of the pump, for instance), available torque may drop significantly. Thus, it might be useful to reduce the effective load/resistance experienced by the pump's crankshaft during transmission shifts. By floating one or more suction valves (by actively opening the suction valves using an active valve system), the effective load can be reduced while transmission shifts are being made. Thus, one or more suction valves could be actively held open whenever a transmission shift is to occur, and then released once the transmission shift is completed (returning to normal operation). The number of suction valves floated could be determined based on the amount of torque that the engine and/or pump can generate during a transmission shift, and the amount of load that floating each suction valve takes from the overall resistance load, with at least the appropriate number of suction valves being floated to allow the engine to provide adequate torque (preventing stalling). This may improve the efficiency of the pump during transmission shifts, as the engine can continue to operate at whatever level it can sustain until the transmission shift is completed and the new gear is brought up to operating speed.
An active valve system may also be used to aid in cleaning out/draining the pump (for example, when a pump job is completed). Once all of the fluid for a job has been appropriately pumped, it may be useful to flush any remaining fluid out of the pump (draining the pump) and/or to dry the pump. This can be especially important in cold environments, since any fluid remaining in the pump could freeze and prevent the pump from operating properly. By actively holding all of the suction valves open as the pump is run/driven (with the plunger cycling through suction and discharge strokes), any fluid remaining in the chamber(s) and/or suction valve(s) may be discharged and/or evaporated. Additionally, air is sucked in and out of the suction valves, serving to air dry the pump. So by continuing to run the pump (after pumping of fluid for the job is complete) while holding all of the suction valves open, the pump may be drained and dried.
Additionally, an active valve system may be used to selectively drop one or more chamber of a pump out of action. By selectively holding one or more suction valves open during operation of the pump, the chambers associated with the one or more suction valves being held open may be deactivated (so that they do not aid in pumping fluid). In essence, this provides for a variable displacement pump. So for example, if a pump has five cylinders, it may be made to effectively operate as a pump having one to five cylinders, depending on the number of suction valves held open per revolution. If the suction valve for one cylinder is held open during pump operation, then the pump would effectively act as a four cylinder pump, while holding two suction valves open per revolution would allow the pump to act as a three cylinder pump. This may be useful in providing finer control over the flow rate of the pump. By taking cylinders out of line (so that one or more cylinders do not pump fluid when the pump is run), it is possible to operate the pump at a slower speed than would otherwise be available (even at the engine's slowest speed in its lowest gear). While deactivating cylinders (by holding suction valve(s) open during pump operation) may reduce the smoothness at which the pump operates, it allows the pump's flow rate range to be expanded (by reducing the minimum available pump flow rate, and by providing for additional intermediate flow rates).
Similarly, if all of the suction valves (associated with all of the cylinders of a pump) are held open (so that all of the cylinders are effectively taken off line and will not pump fluid), then the pump's fluid flow rate may be quickly reduced to zero (even if the pump is still running/the pump components are still moving and/or cycling). In other words, fluid flow may be stopped more quickly by opening and holding all of the suction valves open even as the plunger continues to cycle through suction and discharge strokes. Ceasing to drive/power the pump may not be sufficient for a quick stop (due to inertia). Rather, the suction valves may all be held open until the plunger stops moving. This may serve as a way to more quickly stop pumping (even if the pump components, such as the plunger, are still in motion). Conventionally, a pump cannot be stopped too quickly since the inertia of the pump components/element (such as the plunger) would have to be overcome by the friction forces, etc. before the pump stopped. By holding all of the suction valves open even as the pump components continue to move (for example, as they slow to an eventual stop), it is possible to nearly instantaneously stop actual pumping of fluid. Thus, an active valve system may provide for a safety stop, improving job safety by allowing for fluid pumping to be nearly instantaneously stopped (even if the pump's physical components, such as the plunger, must slow to a stop due to inertia). Persons skilled in the art field will understand these and other uses of such an active valve system.
While various embodiments in accordance with the principles disclosed herein have been shown and described above, modifications thereof may be made by one skilled in the art without departing from the spirit and the teachings of the disclosure. The embodiments described herein are representative only and are not intended to be limiting. Many variations, combinations, and modifications are possible and are within the scope of the disclosure. Accordingly, the scope of protection is not limited by the description set out above, but is defined by the claims which follow, that scope including all equivalents of the subject matter of the claims. Furthermore, any advantages and features described above may relate to specific embodiments, but shall not limit the application of such issued claims to processes and structures accomplishing any or all of the above advantages or having any or all of the above features.
Additionally, the section headings used herein are provided for consistency with the suggestions under 37 C.F.R. 1.77 or to otherwise provide organizational cues. These headings shall not limit or characterize the invention(s) set out in any claims that may issue from this disclosure. Specifically and by way of example, although the headings refer to a “Field of the Invention,” the claims should not be limited by the language chosen under this heading to describe the so-called field. Further, a description of a technology in the “Background” is not to be construed as an admission that certain technology is prior art to any invention(s) in this disclosure. Neither is the “Summary” to be considered as a limiting characterization of the invention(s) set forth in issued claims. Furthermore, any reference in this disclosure to “invention” in the singular should not be used to argue that there is only a single point of novelty in this disclosure. Multiple inventions may be set forth according to the limitations of the multiple claims issuing from this disclosure, and such claims accordingly define the invention(s), and their equivalents, that are protected thereby. The term “comprising” as used herein is to be construed broadly to mean including but not limited to, and in accordance with its typical usage in the patent context, is indicative of inclusion rather than limitation (such that other elements may also be present). In all instances, the scope of the claims shall be considered on their own merits in light of this disclosure, but should not be constrained by the headings set forth herein.
Claims
1. A device comprising:
- a reciprocating pump having a suction valve through which fluid is drawn into a chamber during a suction stroke in order to be discharged from the pump during a discharge stroke; and
- an active valve train providing force to the suction valve.
2. A device as in claim 1 further comprising a timing marker indicative of pump stroke, a sensor operable to detect the timing marker and thereby sense a pump stroke, and a controller coupled to the sensor and the active valve train and activating the active valve train based on the sensed pump stroke.
3. A device as in claim 1 wherein the reciprocating pump further comprises a suction valve spring providing force to close the suction valve.
4. A device as in claim 3 wherein the suction valve spring is sufficiently stiff to minimize valve float as the suction valve closes.
5. A device as in claim 3 wherein the active valve train provides a force directed to open the suction valve prior to, after, or as the suction stroke begins.
6. A device as in claim 5 wherein the opening force is provided by the active valve train during the discharge stroke, and the force provided by the active valve train is greater than the closing force exerted by the suction valve spring.
7. A device as in claim 6 wherein pressure in the chamber varies during the suction and discharge strokes, and the force provided by the active valve train is less than the closing force exerted by the suction valve spring in conjunction with the pressure in the chamber during the discharge stroke.
8. A device as in claim 5 wherein pressure in the chamber varies during the suction and discharge strokes, and the force provided by the active valve train is less than the force exerted by the suction valve spring, but is sufficient in conjunction with the pressure in the chamber during the suction stroke to open the suction valve quickly enough to minimize cavitation.
9. A device as in claim 5 wherein the active valve train releases the opening force prior to the discharge stroke.
10. A method for bringing online a reciprocating pump having multiple chambers each with a suction valve and a plunger driven through a suction stroke and a discharge stroke by a common crankshaft, the method comprising:
- actively opening the suction valves of one or more cylinders and holding the suction valves open;
- bringing the crankshaft up to operating speed; and
- releasing the suction valves to bring the pump online.
11. A method as in claim 10 wherein the suction valves are released sequentially one or more at a time.
12. A method as in claim 10 wherein the suction valves are each released at or near the end of the discharge stroke.
13. A method as in claim 10 wherein the suction valves are released when the crankshaft speed is sufficiently high to provide adequate torque to bring the pump online.
14. A method as in claim 10 further comprising actively opening each suction valve prior to its chamber's suction stroke, and releasing each suction valve prior to its chamber's discharge stroke.
15. A method as in claim 14 further comprising sensing the timing for each pump stroke.
16. A method of servicing a wellbore with servicing fluid using a reciprocating pump having multiple chambers each with a suction valve and a discharge valve and operable to provide a suction stroke and a discharge stroke, the method comprising:
- connecting each suction valve to a source of servicing fluid;
- connecting each discharge valve to the wellbore;
- providing a force to actively open each suction valve prior to, after, or at the start of the suction stroke of its chamber;
- charging each chamber with servicing fluid during its suction stroke;
- releasing the opening force on each suction valve prior to the discharge stroke of its chamber; and
- discharging servicing fluid from each chamber during its discharge stroke and into the wellbore.
17. A method as in claim 16 wherein the suction stroke and discharge stroke of each chamber is driven by a common crankshaft; and the method further comprises sensing the timing of the suction stroke and the discharge stroke based on rotation of the crankshaft.
18. A method as in claim 16 further comprising providing a force for closing the suction valve of each chamber prior to its discharge stroke.
19. A method as in claim 18 wherein the opening force provided to actively open each suction valve prior to the suction stroke of its chamber is greater than the closing force provided to close the suction valve of each chamber prior to its discharge stroke.
20. A method as in claim 18 wherein pressure in the chamber varies during the suction and discharge strokes; and the opening force provided to actively open each suction valve prior to the suction stroke of its chamber is less than the closing force provided to close the suction valve of each chamber prior to its discharge stroke, but is sufficient in conjunction with the pressure in the chamber during the suction stroke to open the suction valve quickly enough to minimize cavitation.
Type: Application
Filed: Aug 8, 2007
Publication Date: Feb 12, 2009
Applicant: Halliburton Energy Services, Inc. (Houston, TX)
Inventors: Timothy Hunter (Duncan, OK), Stanley Stephenson (Duncan, OK)
Application Number: 11/835,523
International Classification: F04B 49/00 (20060101);