Valve system and method for operating a control system of a valve actuator of a valve system

Abstract

The invention provides a valve system and a method of operating a control system of a valve actuator of the valve system. The valve system includes a valve actuator for controlling fluid flow through at least a portion of the valve with a valve element, and a control system for controlling the valve actuator and configured to command the valve actuator to move the valve element from an initial position in the valve to a target position, to reduce or increase fluid flow through the at least a portion of the valve; monitoring at least one characteristic of the valve system during movement of the valve element to the target position; detecting a position of the target position based on the monitored at least one characteristic of the valve system; and at each time the valve element is moved to the target position, substantially maintaining the position of the initial position while actively adjusting the position of the target position based on the monitored at least one feature of the valve system.

Description

[0001] This application is a divisional application of the application with the application number 2020103025877, the title of which is "Valve System and Related Methods", the filing date of which is 2020-04-16. TECHNICAL FIELD

[0002] The present disclosure relates generally to valve actuators, and more particularly, to control systems for valve actuators and related systems and methods. BACKGROUND

[0003] Valves include devices for liquids and gases. Valve actuators are used to operate valves and are manufactured in various shapes, sizes, forms, and have a variety of uses. Valve actuators can be manually driven, electrically driven, operated by fluid pressure or other hydraulic systems in which a shaft is directly or indirectly connected to a fluid operated piston. For example, valve actuators can be manually driven, operated by fluid pressure in which a shaft is directly or indirectly connected to a fluid operated piston, or driven by an electric motor or by electro-hydraulic or electro-fluidic methods. Conventional valve actuators of these types include an electrically driven input shaft, which can be rotatable at relatively high speeds and relatively low torque. The input shaft can rotate an output shaft of relatively high torque, low speed through a reduction gear such as a worm gear or a helical screw thread and nut.

[0004] Actuators are typically formed in a size such that they can provide more torque than is necessary to seat a given valve completely. It can be desirable to determine the torque generated by the output shaft or drive sleeve of a valve actuator. For example, the torque required to operate a valve can be significantly higher when the valve is near a completely closed and / or seated position.

[0005] Actuators typically need to control or limit the amount of torque that can be applied to a load in a manner that is appropriate for the various modes of operation for a given application. If a torque threshold is exceeded, a torque sensor can disengage or stop the operation of the motor, or otherwise stop the operation of the actuator. The torque threshold can be fixed by a user at start-up and can remain fixed until physically changed by a user. In this case, the valve actuator can stop operating without completing the movement of the valve, which can result in the valve not being in a completely seated or closed position.

[0006] In addition to setting a torque threshold, the actuator can be configured (e.g., initially configured) to move a valve element to a selected fully seated or closed position of the valve. However, due to changes in the operating state of the valve assembly (such as material buildup on the valve seat surface and / or valve, wear of the valve seat surface and / or valve, or a combination thereof), the fully seated or closed position of the valve can change over time. The shift in the fully seated or closed position of the valve affects the ability of the actuator to ensure that the valve is properly positioned in the fully seated or closed position. SUMMARY

[0007] In some embodiments, the present disclosure includes a valve system including a valve actuator to control a position of a valve element in a valve to control a flow through at least a portion of the valve, and a control system to control the valve actuator. The control system can be configured to: command the valve actuator to move the valve element toward a first unobstructed position in the valve to enable fluid to flow through at least a portion of the valve; command the valve actuator to move the valve element to a second position in the valve to reduce or increase fluid flow through at least a portion of the valve; monitor at least one characteristic of the valve system during movement of the valve element to the second position; and determine a drift of the second position based on the monitored at least one characteristic of the valve system.

[0008] In further embodiments, the present disclosure includes a valve system including a valve actuator to control a position of a valve element in a valve to control a flow through at least a portion of the valve, and a control system to control the valve actuator. The control system can be configured to: command the valve actuator to move the valve element from an initial position in the valve to a target position to reduce or increase fluid flow through at least a portion of the valve; monitor at least one characteristic of the valve system during movement of the valve element to the target position; and detect a location of the target position based on the monitored at least one characteristic of the valve system. The control system can be further configured to at least one of: move the valve element to contact a valve seat of the valve system in the target position and then force the valve element into the valve seat until a torque of the valve actuator reaches a selected value; or substantially maintain a location of an open position while actively adjusting the location of the target position based on the monitored at least one characteristic of the valve system each time the valve element is moved to the target position.

[0009] In still further embodiments, the present disclosure includes a method of operating a control system of a valve actuator. The method includes moving, with the valve actuator, a valve element to a closed position to substantially inhibit fluid flow through at least a portion of the valve; monitoring at least one characteristic of the valve system during the movement of the valve element to the closed position; determining an offset of the closed position based on the monitored at least one characteristic of the valve system; and at least one of: moving, with the valve actuator, the valve element toward an open position in the valve that does not have a hard stop to enable fluid flow through at least a portion of the valve; moving the valve element to be in contact with a valve seat of the valve system in the closed position and then forcing the valve element into the valve seat until a torque of the valve actuator reaches a selected value; or substantially maintaining a position of the open position while actively adjusting a position of the closed position based on the monitored at least one characteristic of the valve system each time the valve element is moved to the closed position.

[0010] The features, advantages, and various aspects of the present disclosure will be apparent to those skilled in the art from the following detailed description, taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0011] While considered to be a specification of the present disclosure concluding with the claims as specifically set forth and intended to be the scope of protection sought for the present disclosure, the advantages of the present disclosure can be more readily determined from the following description when read in conjunction with the accompanying drawings.

[0012] Figure 1 is a cross-sectional view of an electrically driven valve actuator.

[0013] Figure 2 is a cross-sectional view of a pneumatically driven valve actuator.

[0014] Figure 3 is a diagram illustrating a method of operating a control system of a valve actuator according to one embodiment of the present disclosure.

[0015] Figure 4 illustrates an exemplary graph representing a motion profile of a valve according to one embodiment of the present disclosure.

[0016] Figure 5 is another diagram illustrating a method of operating a control system of a valve actuator according to one embodiment of the present disclosure. DETAILED DESCRIPTION

[0017] Those skilled in the art will understand that, as used herein, the reference to a given parameter with the term“substantially” or“approximately” means and includes, to some extent, the given parameter, characteristic, or state satisfying a small degree of variation, such as within acceptable manufacturing tolerances. For example, a parameter that is substantially satisfied can be at least 90% satisfied, at least 95% satisfied, at least 99% satisfied, or even 100% satisfied.

[0018] Figure 1 An electrically driven valve actuator 100 is shown. Figure 1 Only one view of an electrically driven valve actuator is shown, and is not intended to limit the applicability of the present disclosure to any electrically driven or other valve actuator (e.g., pneumatic actuator, hydraulic actuator, etc.). The valve actuator 100 includes an electric motor 104 coupled to a worm shaft 103. A handwheel 101 is connected to a handwheel adapter 111. The handwheel adapter 111 is connected to a drive sleeve 102. The drive sleeve 102 is connected to a valve stem nut (not shown). A worm gear 110 mates with the worm shaft 103. The worm gear 110 is also coupled to the valve stem nut, which is capable of driving a valve stem of a valve. In Figure 1 In the present embodiment, the valve actuator 100 is not shown attached to a valve. Operation of the electric motor 104 or the handwheel 101 causes the valve stem to rise or fall. The valve stem is capable of traveling up and down through the center of the handwheel 101. The valve stem is also rotatable and operates a nut in the valve that can cause the valve to open or close, or can cause a valve element to rotate directly to an open or closed position (e.g., in a butterfly valve, vane valve, or ball valve).

[0019] The valve actuator 100 can include any drive train, hardware, devices, electronics, and / or software for operating a valve. The valve actuator 100 can be designed for any type of valve, including, for example, linear valves, quarter-turn rotary valves, multi-turn rotary valves, ball valves, plug valves, butterfly valves, and diaphragm valves. The components of the valve actuator 100 can be arranged in any manner. The handwheel 101 can be oriented on the side of the valve actuator 100, as is known in the art.

[0020] The drive train includes any prime mover, any hand-operated mechanism, any decoupling or isolating mechanism, a braking mechanism, any speed-modulating mechanism, and a mechanism for attachment to a valve. The drive train can also exclude any of the above elements, or can also include other elements. For purposes of illustration only, Figure 1 The electric motor 104 is shown as a prime mover and the handwheel 101 is shown as a hand-operated mechanism. Typically, a clutch mechanism would be included so that operation of either the electric motor 104 or the handwheel 101 does not result in operation of the other. By way of example, the lever 105 and the clutch mechanism 113 can be provided as a decoupling or isolating mechanism. A variety of clutches and engagement mechanisms are known in the art. The clutch mechanism 113 can be designed to engage or disengage any portion of the drive train of the valve actuator 100.

[0021] In Figure 1In this design, the locking and braking mechanisms are integrated into the worm shaft 103 and the worm wheel 110. Other gear types, or even none at all, may be used in the valve actuator 100, instead of the worm wheel 110 and worm shaft 103. The type of gear used in the valve actuator is typically selected based on the reduction in speed between the motor 104 and the valve stem nut, if present. In the following discussion, when referring to gears in the transmission system of the valve actuator, the example of a worm wheel and worm shaft is primarily used. However, it should be understood that this discussion can be applied to any gear. If no gear is present in the valve actuator, the output mechanism of any suitable prime mover may also meet the requirements.

[0022] exist Figure 1 In the example, the mechanism for attaching to the valve may be a valve stem nut and associated support structure, as known in the art. However, any mechanism known in the art for attachment may be used. As used herein, the term "valve" covers the most general usage of the term as used in the art, including the definition of a device, component, or system for at least partially controlling the flow of liquids, gases, and / or solids. The electric motor 104 may be any electrically driven prime mover capable of operating the valve actuator.

[0023] Valve actuator 100, during operation, moves the valve at or near its rated design speed (e.g., the rated design speed may be the actuator's full speed) until motor 104 is de-energized. When the valve is moved to its closed position, actuator 100 moves at its rated speed until the valve reaches its closed position (e.g., seated position), thereby increasing the output torque generated by actuator 100. If the torque level reaches a predetermined trip level, motor 104 can be de-energized. This torque-seat method of closing the valve secures it in a closed position that terminates the process flow. In other embodiments, other components of the valve system can be monitored to determine when the valve reaches its closed position. For example, a control system (e.g., control system 106 discussed below) can monitor the position of valve components, the position of the valve shaft, one or more characteristics of the valve actuator (e.g., power consumption, current level supplied to the motor, motor position, motor thermal output, etc.), one or more characteristics of the valve (e.g., characteristics of flow or pressure in or through the valve), or combinations thereof.

[0024] Figure 1An exemplary control system 106 for the valve actuator 100 is also shown. For example, the control system 106 can include a control module 108 for controlling the electric motor 104, and an electronic device 115 is shown for receiving input from an interface (e.g., a control panel 107) and for sending output to an indicator 112. In this particular example, the indicator 112 is shown as a liquid crystal display (LCD). There can be one or more indicators 112. Some non-limiting examples of indicators include light emitting diode lights (LEDs) and displays, filament lights, and dials.

[0025] The control system 106 can also include one or more sensors for determining a position of a portion of the valve (e.g., a valve element that provides a physical barrier to flow in a closed position and allows flow in an open position). For example, the control system 106 can include an encoder 109, which is depicted in Figure 1 as a multi-turn absolute encoder. In other embodiments, the encoder 109 can include a different type of encoder, such as, for example, a single-turn absolute encoder, an incremental encoder, etc. Other types of position sensors can be used, such as, for example, magnetic sensors, inductive sensors, capacitive sensors, etc.

[0026] In some embodiments, the control panel 107 can be part of the control system 106. In other embodiments, the control panel 107 can be formed separate from the control system 106 and in remote communication with the control system (e.g., where the control system 106 is positioned away from the actuator 100). In any example, the control system 106 and / or the control panel 107 can provide user instructions and / or automatic instructions (e.g., in the form of executed coded instructions) that can operate the valve actuator and / or other portions of a valve assembly or system.

[0027] The present disclosure is not limited to any particular valve actuator, and can apply to any valve actuator. Figure 2 A pneumatically driven valve actuator, i.e., valve actuator 140, as known in the art, is shown. The valve actuator 140 is shown in cooperation with a valve 136, and an actuator stem 122 is coupled to a valve element 132 (e.g., a shaft 131 and a plug 130). As noted above, reference is made to Figure 1 and Figure 2 The control system 106 of the actuator 100, 140 can include position sensing features that can monitor a position of the valve 136, such as, for example, one or more positions of the valve element 132 (e.g., the plug 130 and / or the shaft 131 associated therewith).

[0028] Movement of the actuator stem 122 causes corresponding movement of the shaft 131 and the plug 130, thereby controlling operation of the valve 136. The valve 136 can be a globe valve, gate valve, ball valve, butterfly valve, stopcock valve, diaphragm valve, or any other type of valve that can be operated by an actuator. The actuator stem 122, shaft 131, and plug 130 are shown for a representative globe valve. However, it should be understood that any of the components can be modified depending on the type of valve present. Furthermore, when the phrase "drive train" is used hereinafter, the phrase encompasses the drive components of the valve actuator 140, such as the actuator stem 122.

[0029] The valve actuator 140 can also include a control system similar to the control system 106 as shown and described above with reference to FIG. 1. Figure 1

[0030] Embodiments of the methods, devices, apparatuses, and systems of the present disclosure can be used to operate a valve actuator and monitor and control such operation. For example, embodiments of the present disclosure can be used to operate a control system of a valve actuator while monitoring at least one parameter or characteristic of the valve system, in order to periodically modify one or more operations of the valve actuator.

[0031] Embodiments of the present disclosure can include a control system for a valve actuator, such as an internal control system or an external (e.g., remote) control system of the valve actuator.

[0032] Embodiments of the present disclosure can relate to electrically powered valve actuation, which includes changing (e.g., with an electric motor) a valve position to obtain a desired process flow. As noted above, other types of valve actuation can be implemented.

[0033] The control system can command the valve actuator to open the valve from a closed and / or seated position to an intermediate travel position within the travel limits, which can initiate a process flow. Conversely, the valve actuator can move the valve to a closed or seated position, which terminates the process flow. Furthermore, the valve can be moved from one intermediate travel position to another intermediate travel position, which increases or decreases the process flow as desired.

[0034] During a closing or seating event, when the valve begins to make contact with the valve body (e.g., valve seat surface), a resistance to further movement of the valve can be limited due to hard stops and / or other conditions in the valve, such as fluid flow. This can result in a rapid rise in the torque required by the valve actuator to close the valve. For example, the torque gradient can be steep (e.g., over a millisecond of time) such that the final torque applied to the valve by the actuator will exceed the torque trip level of the actuator. In this case, the actuator can not be able to react fast enough to limit the torque level (e.g., stop operation), which can result in accelerated wear of the valve, which will result in maintenance cycles and / or reduce the useful life of the valve.

[0035] ​Furthermore, depending on the process dynamics, such a torque seating method can create a rapid drop in the process flow through the valve, which can create process control transients that can damage other process control elements in the flow process loop. Still further, if the torque gradient is sufficiently severe, it can cause failure of the valve and associated piping.

[0036] Figure 3 is a diagram illustrating a method of operating a control system (e.g., control system 106) of a valve actuator (e.g., valve actuator 100). As Figure 3 shown, in one act, the control system commands the valve actuator to move the valve from an open position (e.g., a fully open position, a partially open position) toward a closed position (e.g., to the closed position).

[0037] In some embodiments, the open position can be unimpeded. For example, the open position can not have a hard stop or backstop that prevents the valve element from moving further past the open position. In other words, the control system can move the valve element in a direction away from the closed position to the open position, where the valve element can move past the open position in a direction away from the closed position. In the case of a rotating valve element, it should be noted that as the valve element moves in one direction (e.g., along one arcuate path) away from the closed position, the valve element can move relatively closer to the closed position in the other direction (e.g., along the other arcuate path).

[0038] In some embodiments, the closed or seated position can include positioning the valve element at a hard seat that is substantially immovable relative to the movable valve element of the valve (e.g., by first contacting the valve seat and then forcing the valve element into the valve seat with the actuator). For example, the valve can include a butterfly valve that contacts a hard stop and is then forced into the hard stop in the closed position in which a valve seat (e.g., a metal or polymer seal) defines a substantial barrier to fluid flow through the valve. In other embodiments, the closed or seated position can include positioning the valve element in a position or valve seat in which further movement of the valve element is substantially unconstrained. For example, the valve can include a ball valve that is positioned in a closed position in a selected orientation in which a valve seat (e.g., a metal or polymer seal) defines a substantial barrier to fluid flow through the valve. However, in such embodiments, the valve element can move beyond the closed or seated position.

[0039] Figure 4An exemplary graph showing a motion profile between an initial position of the valve (e.g., an open position, a closed position, a change therebetween) and a commanded or target position into which the valve actuator is to move the valve element (e.g., an open position, a closed position, a change therebetween) is shown. By way of example, moving the valve element from an open position to a closed position is discussed below. However, in other embodiments, the valve element can be moved between two open positions, can be moved from a closed position to an open position, etc. As discussed further below, the commanded position can relate to a characteristic of the valve. For example, a characteristic of fluid flow, such as flow rate, pressure, and / or pressure differential can be specified, and the control system can move the valve element until such a condition is substantially achieved at the corresponding position. In some embodiments, using known parameters of the valve, the control system can make an initial calculation to predict an approximate position at which such a characteristic can be achieved.

[0040] Referring to Figure 3 and Figure 4 , the control system commands the valve actuator to move the valve (e.g., valve element) from an open position toward a closed position. The valve actuator can accelerate the valve element to a run speed (e.g., can be a partial speed, full speed, or maximum speed of a motor of the actuator). In some embodiments, the control system can calculate and / or monitor the acceleration of the valve element as it ramps up to the run speed (e.g., by monitoring the time taken to reach the run speed from a rest position).

[0041] After the run speed is maintained for a period of time (e.g., which can be monitored by the control system such as a position of the angular position), the control system can begin to decelerate the valve element. As shown, such action can begin at a determined deceleration position. In some embodiments, the determined deceleration position can be calculated (e.g., based on speed), directly sensed (e.g., by sensing a position of the valve element by an encoder or other position sensor), a combination thereof, etc.

[0042] Once the deceleration position is reached, the speed of the valve element can be reduced to a valve seating approach speed (e.g., to perform a soft closure of the valve element). As noted above, the closed or seating position can include positioning the valve element at a hard valve seat that is substantially immovable relative to the movable valve element of the valve, or in a position or valve seat in which further movement of the valve element is substantially unconstrained.

[0043] The actuator can maintain the approach speed until the valve is substantially closed (e.g., fully closed). As noted above, a closed valve can be determined, for example, by a valve element position (e.g., as measured by an output shaft encoder), by a valve seat torque measured by the actuator, by monitoring one or more characteristics of the valve (e.g., a current level supplied to the motor, a flow or pressure through the valve), or a combination thereof.

[0044] In some embodiments, as the valve element moves along the path toward the closed position (e.g., along a portion of the path where the valve element travels at the run speed and / or where the valve element travels at the approach speed), the control system can monitor a first characteristic of the valve (e.g., a position of the valve element, a position of a shaft of the valve or actuator). At a location along the path, as the valve element approaches and reaches the closed position along the path (e.g., along a portion of the path where the valve element travels at the approach speed), the control system can switch to monitoring another characteristic of the valve (e.g., one or more of a torque or current of the valve actuator).

[0045] In some embodiments, as the valve element decreases from the run speed to the approach speed, the control system can calculate and / or monitor a deceleration of the valve element. For example, the control system can monitor a time taken to decrease from the run speed to the approach speed (e.g., a time taken to travel from the deceleration position to the approach position).

[0046] Over time, the closed position of the valve can shift from an initial or previously configured closed position in the actuator (e.g., by a user directly inputting, by sensing the closed position, etc.). In some embodiments, this shift can occur due to wear of one or more components of the valve (e.g., wear experienced by the valve element, valve seat surface, etc.) and / or due to material buildup on one or more components of the valve (e.g., buildup on the valve element, valve seat surface, etc.). In some embodiments, as this wear accumulates over time, the actual closed position can shift further away from the open position, lengthening the travel distance of the actuator to the closed position. In some embodiments, material can build up on the valve, for example, due to precipitation of the process stream, oxidation of the valve material from interaction with the process, etc. In this and other embodiments, the closed position of the valve can shift closer to the open position, reducing the travel of the valve.

[0047] Regardless of the direction and / or magnitude of the shift, the control system can monitor a deviation from the initial closed position of the valve, which can indicate a change from the initially configured operating state. This deviation can be calculated at certain intervals or each time the valve element is moved to the closed position. The control system can sense (e.g., via a position sensor) the new or shifted position of the valve element in the closed position and record the new position. The shift or deviation can be calculated by comparing the initial position and the new or current closed position (e.g., calculating the difference between).

[0048] As shown in FIG. 1 1, once the new closed position is determined, the control system can then adjust the profile utilized in closing the valve (and, in some embodiments, opening the valve). For example, as shown in FIG. 1 1, the control system can adjust the profile to account for the shift in the closed position of the valve. Figure 4 Figure 4 ​As shown, the baseline curve (e.g., the center line in the deviation band) can be modified to the left side of the graph (e.g., when the valve seat has been offset to be relatively closer to the open position) or modified to the right side of the graph (e.g., when the valve seat has been offset to be relatively far from the open position).

[0049] By way of further example, through an adaptive control algorithm, the control system can dynamically adjust (e.g., to recalculate based on baseline parameters in the control system) one or more of the deceleration position and the approach speed position by utilizing the newly sensed seated or closed position of the valve element (e.g., the measured deviation / offset of the closed or seated position).

[0050] like Figure 4 As shown, while the control system can dynamically update the offset of the seated or closed position, it can essentially maintain (e.g., fully maintain) the open position. For example, the control system can dynamically modify the distance between the open and closed positions while essentially maintaining the predetermined open position.

[0051] In other embodiments, the control system may modify the open position relative to a change in the closed position. In yet another embodiment, the control system may dynamically modify the open position based on one or more values ​​monitored by the control system. For example, the control system may modify one or more characteristics of the fluid flow through the valve (e.g., pressure, velocity, flow state, such as laminar, turbulent, or variations thereof). In response to such sensed or monitored values, the control system may actively adjust the open position until an acceptable value is achieved (e.g., a value within a set range stored in the control system).

[0052] In some embodiments, when the offset exceeds a set point (e.g., a predetermined deviation band), a message and / or alarm may be generated to remind maintenance and operation of the offset, optionally indicating the direction in which the offset occurred. Such an alarm message may also include possible causes of the offset and recommended measures.

[0053] Using this adaptive velocity-position curve control algorithm can alleviate many of the problems associated with the aforementioned seating events. In some embodiments, altering the valve seating approach speed characteristics is one way to reduce / eliminate at least some of the unwanted characteristics of moving the valve between positions (e.g., as described above). For example, reducing the valve closing speed before seating can significantly enhance the ability to control the seating event, resulting in a less steep torque gradient, reduced peak torque overshoot, reduced valve wear, and reduced process flow interruptions.

[0054] In some embodiments, such application of electric motor control techniques with closed loop speed and closed loop torque control (e.g., control of power or current to the electric motor) can implement soft seating of the valve, and adaptive control enables the control system to dynamically monitor and update various positions of the valve, such as closed and open positions. In some embodiments, the control system for the valve actuator can implement electric motor control techniques, such as like a direct current (DC) electric motor drive or an alternating current (AC) variable frequency drive with field oriented control. The control system can further include one or more sensors for monitoring the actuator output shaft position (e.g., an encoder or other position sensor) and one or more sensors for measuring outputs and / or inputs related to components of the actuator, such as like output shaft torque (e.g., via motor current or torque-to-force sensing devices), power consumption (e.g., current), and / or operating temperature of the electric motor. When the position of the valve approaches the seating position, implementing an algorithm for commanding a reduction in the approach seating speed can enable a more smooth controlled transition to the seating position. Once in the seating position, the algorithm transitions from a closed loop speed position mode to a closed loop torque control mode, increasing the actuator torque output to a desired final torque level. The electric motor is then de-energized, and the valve is now firmly secured in the closed position.

[0055] In some embodiments, such monitoring of torque with the control system can indicate whether the valve is worn or sticking. Further, a trend pattern in the torque measurements can enable predictive maintenance.

[0056] As described above, in some embodiments, the control system can be used in a somewhat similar manner as shown in FIGS. 1 1 A and 1 1 B to move a valve element between one or more positions in which movement (e.g., rotational movement) of the valve element is unimpeded by a physical hard stop. Figure 3 and Figure 4 The control system can be used in a somewhat similar manner as shown in FIGS. 1 1 A and 1 1 B to move a valve element between one or more positions in which movement (e.g., rotational movement) of the valve element is unimpeded by a physical hard stop. As described above, such a configuration does not have a hard seating position at the end of travel and the associated torque increase and torque kick. Such a valve configuration (e.g., a modulating control valve) can have a physical position and geometry that can close flow, fully open, and / or throttle between open and closed or closed positions defining different operating ranges.

[0057] In the example of a modulating control valve, such a valve can be used to precisely regulate a process flow or pressure. Fluid flow can be measured directly by a flow sensor, or fluid flow can be measured by measuring a differential pressure across the valve.

[0058] Figure 5 is a diagram showing a method of operating a control system for a valve actuator, for example, in which positions are unimpeded (e.g., do not have a hard stop). As described above, such positions can include a combination of multiple open positions of a valve element and a closed position or seating position that does not have a hard stop.

[0059] Referring to Figure 4 and 5 When the valve is moved to a commanded position or target position that does not have an associated hard stop, the actuator will move at its rated speed until the valve reaches the commanded position where the motor is de-energized and motion stops. However, the actuator can have overshot the commanded position, triggering a correction in the form of motion in the opposite direction. Since this correction is typically a relatively small motion, the duration of the motor energization is also small, perhaps even just a quick pulse. The actuator can overshoot again and start a correction in the original direction. This hunting / oscillation will continue until the error between the commanded position and the actual position falls within the deadband parameter of the control loop (e.g., a range where the position error is small enough that no further action is needed). If the deadband parameter (or other gain parameters) are not set correctly, the oscillation can continue indefinitely, leading to reduced actuator life and process disturbances in the flow loop. In some examples, the actuator can overheat (e.g., thermal trip), causing the actuator to be disabled for a period of time to cool down, during which time the process is temporarily not actively controlled.

[0060] Implementing a closed loop process algorithm as described above to regulate the reduction in approach velocity as the valve approaches the commanded position, flow rate, and / or expected pressure can result in a smooth, controlled transition from motion to stop. Overshoot and hunting / oscillation with respect to the expected process parameters can be reduced or eliminated, resulting in faster process startup, less wear on the actuator and valve, and better process stability.

[0061] Referring to Figure 4 and 5 The offset can be characterized as a process error, where the error is a function of the difference between the set process variable (e.g., position, flow rate, and / or pressure) and the process setpoint for that process variable. The characteristics of the operating curve can be parameterized by the operator, or dynamically calculated (e.g., learned) by implementing an automatic tuning algorithm. The latter provides for dynamic updates to control the operation and / or characteristics of the valve, ensuring optimal performance throughout the operating range. Dynamic updates can also adjust for changing environmental conditions, flow materials, and / or equipment wear, all of which can affect the operation of the actuator and process stability.

[0062] One or more initial valve position can be utilized to benchmark valve actuator performance to establish an expected process signature. Over time, wear / accumulation on the valve can cause these one or more positions to change, and the control system can update these positions to produce substantially the same process signature. When the one or more positions deviate from the one or more benchmark positions, an alarm can be generated once the deviation exceeds an operator-defined deviation band. This alarm can alert the operator and maintenance resources that the system performance is changing, which can indicate that the system health is eroding and potential system failure.

[0063] In some embodiments, the control system can monitor one or more characteristics of the valve (e.g., torque profile) compared to a baseline. As described above, the valve actuator can be equipped with a torque limiting device. If the torque generated by the actuator exceeds the torque set by the limiting technology, the device can cause the motor to de-energize. Replacing or supplementing the torque limiting technology with a dynamic direct torque measurement technology can enable the actuator to monitor the torque generated throughout the valve motion. The torque profile can be benchmarked, and subsequent torque profiles of valve motions can be monitored and compared to the torque profile baseline.

[0064] As the actuator and valve wear and / or the environmental and / or operating conditions change, the deviation between the actual measured torque profile and the benchmark torque profile will increase. As these deviations begin to exceed a deviation limit, a measure (e.g., one or more alarms) can be generated to alert the operator and maintenance resources that the system’s changing operating dynamics are indicative of a potential degradation in system health. In some embodiments, the analysis of the changing torque profile can be utilized to suggest areas of the system to investigate as the root cause of the deviation.

[0065] In some embodiments, the control system can monitor one or more heat values in the valve system. For example, when the actuator moves the valve, the prime mover of the system is the motor in the actuator, which will generate heat energy during operation. The heat rise rate can be partially determined by one or more of: (1) the number of moves per unit time, (2) the load on the motor (e.g., the torque required to move the valve at the commanded speed), (3) the ambient temperature, and (4) the motor’s construction, thermal rating, and heat dissipation design.

[0066] For example, running a motor at maximum speed with a high load for multiple runs in a very warm environment will result in a high heat rise (e.g., temperature rise). Since the components of the actuator have a rated operating temperature in their design specifications, this situation can limit the amount the actuator can be used to move the valve. Driving the equipment beyond these rated thermal conditions can severely damage the equipment or even cause equipment failure. Typically, if the actuator exceeds the rated operating temperature of the motor, the actuator stops to cool until the temperature returns to the operating range.

[0067] In some embodiments, since the actuator device can include a mission critical application, stopping the actuator to cool can not be acceptable.

[0068] In some embodiments, the control system can monitor the current temperature and / or the rate of temperature rise of the motor. The control system can predict when the actual temperature of the motor will exceed the temperature specification based on the actual motor temperature and / or the rate of change. In this case, the adaptive control algorithm can reduce the speed of the motor, thus reducing the thermal efficiency, and enable the actuator to continue to operate within the specified operating range. Although this measure can not completely prevent the actual temperature of the motor from eventually exceeding the specification, this throttling of the motor will expand the operating window of the actuator.

[0069] As the rate of heat rise decreases, the throttling can be reduced until the motor temperature again begins to rise or returns to full operating capability.

[0070] While certain embodiments have been described and shown, these embodiments are merely exemplary and are not intended to limit the scope of the present disclosure, and the present disclosure is not limited to the precise construction and arrangement shown and described since such will vary depending upon the desires of the particular application. Accordingly, the scope of the present disclosure is limited only by the language of the appended claims and legal equivalents thereof.

Claims

1. A valve system comprising: a valve actuator for controlling fluid flow through at least a portion of a valve with a valve element; and a control system for controlling the valve actuator, the control system configured to: command the valve actuator to move the valve element from an initial position in the valve to a target position to reduce or increase fluid flow through the at least a portion of the valve; monitor at least one characteristic of the valve system during movement of the valve element to the target position; detect a position of the target position based on the monitored at least one characteristic of the valve system; and substantially maintain a position of the initial position each time the valve element moves to the target position while actively adjusting the position of the target position based on the monitored at least one characteristic of the valve system.

2. The valve system of claim 1, wherein, the control system is further configured to monitor torque of the valve actuator when the valve element is positioned at the target position.

3. The valve system of claim 1, wherein, the control system is further configured to determine a shift of the target position based on the monitored at least one characteristic of the valve system.

4. The valve system of claim 3, wherein, the control system is further configured to: decrease a rate of the valve element at a selected point as the valve element progresses to the target position; and update the selected point for decreasing the speed of the valve element based on the determined shift of the target position. the control system is further configured to:

5. The valve system of claim 3, wherein, update a position of the target position based on the determined shift; and / or update a position of a change in speed of the valve element based on the determined shift. the control system is further configured to update a deceleration point based on the determined shift.

6. The valve system of claim 3, wherein, the control system is further configured to generate an alert or warning when the determined shift is outside of a selected range of shift values.

7. The valve system of claim 3, wherein, the control system is further configured to at least one of:

8. The valve system of claim 1, wherein, determine that the target position of the valve element has shifted to a position relatively closer to the initial position; or determine that the target position of the valve element has shifted to a position relatively further from the initial position. the at least one characteristic comprises at least one of: torque of the valve actuator; current of the valve actuator; flow rate through the valve; flow type through the valve; position of the valve element; and 9. The valve system of claim 1, wherein, pressure in the valve. the control system is further configured to monitor at least another characteristic of the valve system during movement of the valve element back to the initial position.

10. The valve system of claim 1, wherein, the initial position is unobstructed.

11. The valve system of claim 1, wherein, the unobstructed initial position comprises a position of the valve element without a hard stop, and wherein the target position comprises a hard stop.

12. The valve system of claim 11, wherein, the target position comprises a closed seated position, and wherein the control system is configured to move the valve element into contact with a valve seat of the valve system and then force the valve element into the valve seat until torque of the valve actuator reaches a selected value.

13. The valve system of claim 1, wherein, 14. A valve system comprising: ​ a valve actuator for controlling fluid flow through at least a portion of a valve with a valve element; and a control system for controlling the valve actuator, the control system configured to: command the valve actuator to move the valve element from an unobstructed initial position in the valve to a target position to reduce or increase fluid flow through the at least a portion of the valve; monitor at least one characteristic of the valve system during movement of the valve element to the target position; and during each movement of the valve element, the control system is further configured to at least one of: move the valve element into contact with a valve seat of the valve system in the target position and then force the valve element into the valve seat until a torque of the valve actuator reaches a selected value; or substantially maintain a predetermined position of the initial position while actively adjusting a position of the target position based on the monitored at least one characteristic of the valve system at each movement of the valve element to the target position.

15. The valve system of claim 14, wherein, the control system is configured to monitor a torque of the valve actuator when the valve element is positioned at the target position.

16. A method of operating a control system of a valve actuator of a valve system, the method comprising: moving a valve element from an open position to a closed position with the valve actuator to substantially inhibit fluid flow through at least a portion of a valve; monitoring at least one characteristic of the valve system during movement of the valve element to the closed position; determining an offset of the closed position based on the monitored at least one characteristic of the valve system; and substantially maintaining a position of the open position while actively adjusting a position of the closed position based on the monitored at least one characteristic of the valve system at each movement of the valve element to the closed position.

17. The method of claim 16, further comprising one or more of: monitoring at least another characteristic of the valve system during movement of the valve element to the open position; or positioning the control system at a location remote from the valve.

18. The method of claim 16, further comprising: monitoring a position of the valve element as the valve element moves along a path toward the closed position; and switching to monitoring at least one of a torque and a current of the valve actuator at a position along the path as the valve element approaches and reaches the closed position along the path.

19. The method of claim 16, further comprising: decreasing a velocity of the valve element at a selected point as the valve element travels toward the closed position; and updating the selected point for decreasing the velocity of the valve element based on the determined offset of the closed position.

20. The method of claim 16, further comprising: ​ moving the valve element toward the open position in the valve that does not have a hard stop using the valve actuator to enable fluid flow through the at least a portion of the valve; moving the valve element into contact with a valve seat of the valve system in the closed position and then forcing the valve element into the valve seat until a torque of the valve actuator reaches a selected value.

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