Patent Application
20170122454
This disclosure relates to electro-hydraulic actuators for valves. In some installations in the oil and/or gas industry, it is sometimes desirable to implement fail-in-last position actuators onto process valves for affecting the flow of fluids such as oil or gas. In the event of primary power loss, a fail-in-last position actuator will maintain an associated valve in the current position. Typically, fail-in-last position actuators utilize pumped systems and solenoid controlled circuits to provide the desired functionality.
There exists a need for a simpler system that does not include a power consuming pump and control circuitry to provide a fail-in-last position actuator.
Some embodiments of the invention provide an electro-hydraulic actuator for actuating a valve. The electro-hydraulic actuator includes an electric linear actuator having an electric motor and a controller that controls the electric motor. A double chamber hydraulic cylinder includes a double chamber piston that is coupled to the electric linear actuator, and defines a first double chamber volume and a second double chamber volume. The position of the double chamber piston affects the relative volumes of the first double chamber volume and the second double chamber volume. A hydraulic actuator includes a hydraulic actuator housing, a first rack piston, a second rack piston, a rack arranged between the first rack piston and the second rack piston, and a pinion engaged with the rack. A first hydraulic actuator volume is defined between the hydraulic actuator housing and the first rack piston and is in communication with the first double chamber volume. A second hydraulic actuator volume is defined between the hydraulic actuator housing and the second rack piston and is in communication with the second double chamber volume.
Another embodiment of the invention provides a valve and actuator system that includes a valve and an electro-hydraulic actuator. The valve includes a quarter turn valve element moveable between an open position and a closed position. The electro-hydraulic actuator includes an electric linear actuator, a double chamber hydraulic cylinder having a double chamber piston coupled to the electric linear actuator, and a hydraulic actuator having a hydraulic actuator housing, a first rack piston, a second rack piston, a rack arranged between the first rack piston and the second rack piston, and a pinion engaged with the rack. Movement of the double chamber piston actuates the hydraulic actuator. The pinion is coupled to the valve to actuate the quarter turn valve element between the open position and the closed position.
Another embodiment of the invention provides a method of operating a valve with an electro-hydraulic actuator. The method includes controlling an electric motor with the controller, moving a linear actuator with the electric motor, moving a double chamber piston with the linear actuator, moving a rack with hydraulic fluid moved by the double chamber piston, rotating a pinion with the rack, and actuating the valve with the pinion.
Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.
The following discussion is presented to enable a person skilled in the art to make and use embodiments of the invention. Various modifications to the illustrated embodiments will be readily apparent to those skilled in the art, and the generic principles herein can be applied to other embodiments and applications without departing from embodiments of the invention. Thus, embodiments of the invention are not intended to be limited to embodiments shown, but are to be accorded the widest scope consistent with the principles and features disclosed herein. The following detailed description is to be read with reference to the figures, in which like elements in different figures have like reference numerals. The figures, which are not necessarily to scale, depict selected embodiments and are not intended to limit the scope of embodiments of the invention. Skilled artisans will recognize the examples provided herein have many useful alternatives and fall within the scope of embodiments of the invention.
As shown in
The electric actuator 18 integrates the electric motor 42, the controller 50, and all required communication functions in an explosion proof enclosure 70, with a local interface for local non-intrusive operation and configuration. Remote operation and configuration of the electric actuator 18 are also available via the Bluetooth™ wireless communication provided by the controller 50. Manual operation via the hand wheel 58 is provided in case of power failure. The low revolutions output of electric motor 42 is converted into linear movement of the threaded shaft 62 by the recirculating ball nut 66. The power screw assembly 46 with recirculating balls increases the mechanical efficiency and the usable lifetime of the electric actuator 18.
As shown in
As further shown in
The first accumulator 26 is in fluid communication with the first double chamber volume 86 via the first double chamber port 98, and the second accumulator 30 is in fluid communication with the second double chamber volume 90 via the second double chamber port 102. The first accumulator 26 and the second accumulator 30 may be substantially the same and in one embodiment are bladder type accumulators. The first accumulator 26 and the second accumulator 30 compensate for the difference in volumetric displacement of the first double chamber volume 86 and the second double chamber volume 90 (the first double chamber volume 86 has less volumetric displacement due to the presence of the coupler 94). Additionally, the first accumulator 26 and the second accumulator 30 absorb any thermal expansion of the hydraulic fluid within the electro-hydraulic actuator 10, avoiding over pressure due to temperature variations.
As shown in
As shown in
The valve 14 may be a quarter turn valve such as a ball valve or a butterfly valve, for example, that includes an input shaft 150 coupled to the pinion 114 via the coupling 38. Actuation of the electro-hydraulic actuator 10 rotates the input shaft 150 so that the valve 14 can be actuated between opened or closed positions.
Operation of the electro-hydraulic actuator 10 and the associated valve 14 will be discussed below with reference to
When the controller 50 determines that the state of the valve 14 should be changed, whether from external communication or internal programming, power is supplied to the electric motor 42 and the reciprocating ball nut 66 is rotated so that the threaded shaft 62 moves linearly. For example, when the reciprocation ball nut 66 is rotated clockwise, the threaded shaft 62 extends from the electric actuator 18 and the double chamber piston 78 moves to increase the amount of hydraulic fluid held within the first double chamber volume 86 and to reduce the amount held within the second double chamber volume 90. In turn, the pressure in the first hydraulic actuator volume 134 decreases, and the pressure in the second hydraulic actuator chamber 146 increases. The pressure differential moves the rack 110 toward the first hydraulic actuator volume 134 (e.g., to the right in
When the reciprocation ball nut 66 is rotated counter-clockwise, the threaded shaft 62 retracts into the electric actuator 18 and the double chamber piston 78 moves to decrease the amount of hydraulic fluid held within the first double chamber volume 86 and to increase the amount held within the second double chamber volume 90. In turn, the pressure in the first hydraulic actuator volume 134 increases, and the pressure in the second hydraulic actuator chamber 146 decreases. The pressure differential moves the rack 110 toward the second hydraulic actuator volume 146 (e.g., to the left in
The accumulators 26, 30 act to absorb volumetric displacement and thermally induced changes within the system. For example, at higher temperatures, the pressure of the hydraulic fluid increases and the accumulators 26, 30 need to relieve pressure. At lower temperatures, pressure is decreased and the accumulators 26, 30 need to add pressure to the system.
The electro-hydraulic actuator 10 provides a closed hydraulic system that does not require a pump or solenoid controlled hydraulic flow/control (e.g., using flow regulators, solenoid operated pressure valves, control systems, etc.). Additionally, the system does not require relief valves or stop valves. A closed system presents less risk of leakage and failure due to power loss or insufficient maintenance. Since the system does not include a pump, relative sea level does not affect the performance of the system. Another advantage of the closed system design is that the electro-hydraulic actuator 10 can be installed in areas where there may not be sufficient power to operate a pump.
The electro-hydraulic actuator 10 is a fail-in-last-position type actuator. In other words, hydraulic fluid and pressure are always maintained in both the first hydraulic actuator volume 134 and the second hydraulic actuator volume 146 so that the rack 110 is effectively locked in place.
It will be appreciated by those skilled in the art that while the invention has been described above in connection with particular embodiments and examples, the invention is not necessarily so limited, and that numerous other embodiments, examples, uses, modifications and departures from the embodiments, examples and uses are intended to be encompassed by the claims attached hereto. The entire disclosure of each patent and publication cited herein is incorporated by reference, as if each such patent or publication were individually incorporated by reference herein.
Various features and advantages of the invention are set forth in the following claims.
