Valve system and related methods

Abstract

A valve system and related methods, the valve system including a valve actuator and a control system, the control system configured to monitor at least one characteristic of the valve system during movement of a valve element to a position in the valve system and determine an offset of the position based on the at least one monitored characteristic of the valve system.

Description

Technical Field

[0001] The present disclosure relates generally to valve actuators and, more particularly, to control systems for valve actuators and related systems and methods. Background Art

[0002] Valves include devices for liquids and gases. Valve actuators are used to operate valves and are manufactured in various shapes, sizes, forms, and have multiple uses. The valve actuator can be driven manually, electrically, and operated by fluid pressure or other hydraulic systems, in which the shaft is directly or indirectly connected to a fluid-operated piston. For example, the valve actuator can be driven manually, operated by fluid pressure in which the shaft is directly or indirectly connected to a fluid-operated piston, or driven by an electric motor or by electrohydraulic or electrofluidic methods. Traditional valve actuators include an electrically driven input shaft, which can be capable of rotating at a relatively high speed and relatively low torque. The input shaft can rotate a relatively high torque, low speed output shaft through a reduction gear such as a worm gear or helical thread and nut.

[0003] Actuators are often sized to provide more torque than is necessary to fully seat a given valve. It may 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 may be significantly higher as the valve approaches a fully closed and / or fully seated position.

[0004] Actuators typically need to control or limit the amount of torque that can be applied to a load in a manner appropriate for the various operating modes of a given application. If a torque threshold is exceeded, the torque sensor can disengage or stop the motor, or otherwise stop the actuator. The torque threshold can be fixed by the user at startup and remain fixed until physically changed by the user. In this case, the valve actuator may stop operating without completing the valve's movement, potentially resulting in the valve not being in a fully seated or closed position.

[0005] In addition to setting a torque threshold, the actuator can be configured (e.g., initially configured) to move the valve element (spool) to a selected fully seated or closed position of the valve. However, due to changes in the operating conditions of the valve assembly (such as material buildup on the seat surface and / or the valve, wear of the seat surface and / or the valve, or a combination thereof), the fully seated or closed position of the valve may vary over time. This shift in the fully seated or closed position of the valve affects the ability of the actuator to ensure that the valve is correctly positioned in the fully seated or closed position. Summary of the Invention

[0006] In some embodiments, the present disclosure includes a valve system comprising a valve actuator for controlling a position of a valve element in a valve to control flow through at least a portion of the valve, and a control system for controlling the valve actuator. The control system may be configured to: command the valve actuator to move the valve element toward a first, unobstructed position in the valve to enable fluid 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 at least one monitored characteristic of the valve system.

[0007] In another embodiment, the present disclosure includes a valve system comprising a valve actuator for controlling a position of a valve element in a valve to control flow through at least a portion of the valve, and a control system for controlling the valve actuator. The control system may 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 at least one monitored characteristic of the valve system. The control system may be 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 actively adjust the position of the target position based on the at least one monitored characteristic of the valve system each time the valve element moves to the target position while substantially maintaining the position of the open position.

[0008] In yet another embodiment, the present disclosure includes a method of operating a control system for a valve actuator. The method includes: moving a valve element with the valve actuator to a closed position to substantially inhibit fluid flow through at least a portion of the valve; monitoring at least one characteristic of a valve system during movement of the valve element to the closed position; determining an offset from the closed position based on the at least one monitored characteristic of the valve system; and at least one of: moving the valve element with the valve actuator toward an open position in the valve without a hard stop to enable fluid flow through 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; or actively adjusting the position of the closed position based on the at least one monitored characteristic of the valve system while substantially maintaining the position of the open position each time the valve element moves to the closed position.

[0009] The features, advantages, and aspects of the present disclosure will become apparent to those skilled in the art from the following detailed description considered in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] While the specification of the present disclosure is considered to conclude with claims particularly pointed out and distinctly claimed, the advantages of the present disclosure may be more readily ascertained from the following description of the disclosure when read in conjunction with the accompanying drawings.

[0011] Figure 1 is a cross-sectional view of an electrically driven valve actuator.

[0012] Figure 2 is a cross-sectional view of a pneumatically driven valve actuator.

[0013] 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.

[0014] Figure 4 An exemplary graph representing a motion curve of a valve according to one embodiment of the present disclosure is shown.

[0015] 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

[0016] Those skilled in the art will understand that, as used herein, the reference to the term "substantially" or "approximately" for a given parameter means and includes, to a certain extent, that the given parameter, characteristic, or condition meets a small degree of variation, such as within an acceptable manufacturing tolerance. For example, a parameter that is substantially met may be met by at least 90%, met by at least 95%, met by at least 99%, or even 100%.

[0017] 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.). Valve actuator 100 includes an electric motor 104 coupled to a worm shaft 103. Handwheel 101 is connected to a handwheel adapter 111. Handwheel adapter 111 is connected to drive sleeve 102. Drive sleeve 102 is connected to a valve stem nut (not shown). Worm gear 110 mates with worm shaft 103. Worm gear 110 is also coupled to a valve stem nut, which is capable of driving the valve stem of the valve. In Figure 1In the figure, valve actuator 100 is not shown attached to the valve. Operation of motor 104 or handwheel 101 raises or lowers the valve stem. The valve stem can move up and down via the center of handwheel 101. The valve stem can also rotate and operate a nut in the valve that can open or close the valve, or can directly rotate the valve element to an open or closed position (for example, in a butterfly valve, leaf valve, or ball valve).

[0018] 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 use with 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.

[0019] The drive train includes any prime mover, any manually operated mechanism, any disengaging or isolating mechanism, braking mechanism, any speed modulation mechanism, and a mechanism for attaching to a valve. The drive train may also exclude any of the above elements or may also include other elements. For illustration purposes only, Figure 1 An electric motor 104 is shown as a prime mover, and a handwheel 101 is shown as a manual operating mechanism. Typically, a clutch mechanism will be included so that operation of either the electric motor 104 or the handwheel 101 does not cause operation of the other. By way of example, the lever 105 and the clutch mechanism 113 may be configured as a disengagement or isolation mechanism. Various clutch and engagement mechanisms are known in the art. The clutch mechanism 113 may be designed to engage or disengage any portion of the drive train of the valve actuator 100.

[0020] exist Figure 1 10 and 110. In the embodiment of the present invention, the locking and braking mechanism is incorporated into the worm shaft 103 and the worm wheel 110. Instead of or in addition to the worm wheel 110 and worm shaft 103, other gear types or no gears may be used in the valve actuator 100. The type of gear used for the valve actuator is typically selected based on the amount of speed reduction (if any) between the motor 104 and the valve stem nut. In the following, when referring to the gears of the drive train of the valve actuator, the example of a worm wheel and worm shaft is primarily used. However, it should be understood that the discussion is applicable to any gear. If no gears are present in the valve actuator, then the output mechanism of any suitable prime mover may also suffice.

[0021] exist Figure 1In the example of FIG, the mechanism for attaching to the valve may be a stem nut and associated support structure, as known in the art. However, any mechanism for attachment known in the art may be used. As used herein, the term "valve" encompasses the most general usage of the term as used in the art, including the definition of a device, assembly, or system that at least partially controls the flow of liquids, gases, and / or solids. The motor 104 may be any electrically driven prime mover capable of operating a valve actuator.

[0022] During operation, the valve actuator 100 can move the valve at or near its rated design speed (e.g., the rated design speed can be the full speed of the actuator) until the motor 104 is de-energized. When moving the valve to its closed position, the actuator 100 will move at its rated speed until the valve reaches its closed position (e.g., seated position), thereby increasing the output torque generated by the actuator 100. If the torque level reaches a predetermined trip level, the motor 104 can be de-energized. This torque-seating method of closing the valve can secure the valve in a closed position that terminates process flow. In other embodiments, other components of the valve system can be monitored to determine when the valve reaches the closed position. For example, a control system (e.g., control system 106 discussed below) can monitor the position of the valve element, 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 heat output, etc.), one or more characteristics of the valve (e.g., characteristics of the flow or pressure in or through the valve), or a combination thereof.

[0023] Figure 1 Also shown is an exemplary control system 106 for the valve actuator 100. For example, the control system 106 may include a control module 108 for controlling the motor 104, and electronics 115 are shown for receiving input from an interface (e.g., the 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 may be one or more indicators 112. Some non-limiting examples of indicators include light emitting diodes (LEDs) and displays, filament lights, and dials.

[0024] The control system 106 may also include one or more sensors for determining the position of a portion of a 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 may include an encoder 109 that Figure 11 is depicted as a multi-wheel absolute encoder. In other embodiments, encoder 109 may include different types of encoders, such as a single-wheel absolute encoder, an incremental encoder, etc. Other types of position sensors may be used, such as magnetic sensors, inductive sensors, capacitive sensors, etc.

[0025] In some embodiments, the control panel 107 can be part of the control system 106. In other embodiments, the control panel 107 can be separate from the control system 106 and in remote communication with the control system (e.g., where the control system 106 is located remotely 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 the valve assembly or system.

[0026] The present disclosure is not limited to any particular valve actuator and is applicable to any valve actuator. Figure 2 A pneumatically driven valve actuator, namely valve actuator 140, as is known in the art, is shown. Valve actuator 140 is shown mated with valve 136, with actuator stem 122 coupled to valve element 132 (e.g., shaft 131 and plug 130). As noted above, with reference to Figure 1 and Figure 2 The control system 106 of the actuators 100, 140 may include position sensing features that may monitor the position of the valve 136, such as, for example, one or more positions of the valve element 132 (eg, the plug 130 and / or the shaft 131 associated therewith).

[0027] Movement of the actuator stem 122 causes corresponding movement of the shaft 131 and the plug 130, thereby controlling the operation of the valve 136. The valve 136 can be a globe valve, a gate valve, a ball valve, a butterfly valve, a plug valve, a diaphragm valve, or any other type of valve that can be operated by an actuator. The actuator stem 122, the shaft 131, and the 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 being used. 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.

[0028] The valve actuator 140 may also include a control system similar to that described above with reference to Figure 1 The control system 106 is shown and described.

[0029] Embodiments of the methods, apparatuses, devices, and systems of the present disclosure may be used to operate a valve actuator and monitor and control such operation. For example, embodiments of the present disclosure may be used to operate a control system of a valve actuator while monitoring at least one parameter or characteristic of the valve system to periodically modify one or more operations of the valve actuator.

[0030]

[0014] Embodiments of the present disclosure may include a control system for a valve actuator, such as, for example, an internal control system of the valve actuator or an external (eg, remote) control system.

[0031] Embodiments of the present disclosure may relate to electric valve actuation, which involves changing (eg, using an electric motor) a valve position to achieve a desired process flow. As noted above, other types of valve actuation may be implemented.

[0032] 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, thereby initiating process flow. Conversely, the valve actuator can move the valve to a closed or seated position, thereby terminating process flow. Furthermore, the valve can be moved from one intermediate travel position to another, thereby increasing or decreasing process flow as needed.

[0033] During closure or seating, when the valve begins to contact the valve body (e.g., the valve seat surface), resistance to further valve movement may be limited due to hard stops and / or other conditions in the valve (such as fluid flow). This can cause the torque required by the valve actuator to close the valve to rise rapidly. For example, this torque gradient may be so steep (e.g., over a period of milliseconds) that the final torque applied by the actuator to the valve will exceed the actuator's torque trip level. In this case, the actuator may not react quickly enough to limit the torque level (e.g., cease operation), which can lead to accelerated wear of the valve, which may increase maintenance intervals and / or reduce the life of the valve.

[0034] Furthermore, depending on process dynamics, this torque seating method can produce a rapid drop in 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 severe enough, it can lead to failure of the valve and associated piping.

[0035] Figure 3 1 is a diagram illustrating a method of operating a control system (eg, control system 106) of a valve actuator (eg, valve actuator 100). Figure 3 As shown, in one action, the control system commands the valve actuator to move the valve from an open position (eg, fully open position, partially open position) toward a closed position (eg, to a closed position).

[0036] In some embodiments, the open position may be unobstructed. For example, the open position may not have a hard stop or a reverse stop that prevents the valve element from moving further past a certain open position. In other words, the control system may cause the valve element to move in a direction away from the closed position to the open position, wherein the valve element is able to move past the open position in a direction away from the closed position. In the case of a rotary valve element, it should be noted that when the valve element moves away from the closed position in one direction (e.g., along an arcuate path), the valve element can move relatively closer to the closed position in another direction (e.g., along another arcuate path).

[0037] In some embodiments, the closed or seated position may include positioning the valve element at a hard valve seat that is substantially immovable relative to a 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 an actuator). For example, the valve may include a butterfly valve that contacts a hard stop and is then forced into the hard stop in a closed position, in which the 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 may 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 may include a ball valve that is positioned in a closed position in a selected orientation, in which the 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 may be movable beyond the closed or seated position.

[0038] Figure 4 An exemplary graph is shown representing a motion curve between an initial position (e.g., open position, closed position, variations therebetween) of a valve and an instruction or target position (e.g., open position, closed position, variations therebetween) to which the valve actuator will move the valve element. By way of example, the following discussion will move the valve element from an open position to a closed position. However, in other embodiments, the valve element may be movable between two open positions, from a closed position to an open position, etc. As discussed further below, the command position may relate to a characteristic of the valve. For example, a characteristic of the fluid flow, such as flow rate, pressure, and / or pressure difference, may be specified, and the control system may move the valve element until such a state is substantially achieved at the corresponding position. In some embodiments, using known parameters of the valve, the control system may perform an initial calculation to predict an approximate position at which such a characteristic may be achieved.

[0039] refer to Figure 3 and Figure 4, the control system commands the valve actuator to move the valve (e.g., valve element) from the open position toward the closed position. The valve actuator can accelerate the valve element to an operating speed (e.g., which can be a fraction of the speed, full speed, or maximum speed of the actuator's motor). In some embodiments, the control system can calculate and / or monitor the acceleration of the valve element as it ramps up to the operating speed (e.g., by monitoring the time it takes to reach the operating speed from a rest position).

[0040] After maintaining the operating speed for a period of time (e.g., a position such as angular position can be monitored by the control system), 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 the position of the valve element via an encoder or other position sensor), or a combination thereof.

[0041] 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 closing of the valve element). As described above, the closed or seated position can include positioning the valve element at a hard valve seat that is substantially immovable relative to a movable valve element of the valve, or positioning the valve element in a position or seat in which further movement of the valve element is substantially unrestrained.

[0042] The actuator may maintain the approach velocity until the valve is substantially closed (e.g., fully closed). As described above, a closed valve may be determined, for example, by valve element position (e.g., measured by an output shaft encoder), valve seating torque measured by the actuator, by monitoring one or more characteristics of the valve (e.g., current level supplied to the motor, flow or pressure across the valve), or a combination thereof.

[0043] In some embodiments, as the valve element moves along a path toward a closed position (e.g., along a portion of the path where the valve element travels at an operating speed and / or at an approach speed), the control system may monitor a first characteristic of the valve (e.g., position of the valve element, position of a valve or actuator shaft). At one position along the path, as the valve element approaches and reaches the closed position along the path (e.g., along the path where the valve element travels at an approach speed), the control system may switch to monitoring another characteristic of the valve (e.g., one or more of torque or current of the valve actuator).

[0044] In some embodiments, the control system can calculate and / or monitor the deceleration of the valve element as it decelerates from the operating speed to the approach speed. For example, the control system can monitor the time it takes to reach the approach speed from the operating speed (e.g., the time it takes to travel from the deceleration position to the approach position).

[0045] Over time, the closed position of a valve may drift from the closed position initially or previously configured in the actuator (e.g., through direct user input, by sensing the closed position, etc.). In some embodiments, this drift may occur due to wear on one or more components of the valve (e.g., wear experienced by the valve element, valve seat surfaces, etc.) and / or due to material buildup on one or more components of the valve (e.g., buildup on the valve element, valve seat surfaces, etc.). In some embodiments, as this wear accumulates over time, the actual closed position may shift further away from the open position, increasing the travel distance of the actuator to the closed position. In some embodiments, material may accumulate on the valve, for example, due to precipitation from the process stream, oxidation from the interaction of the valve material with the process, etc. In this and other embodiments, the closed position of the valve may be moved closer to the open position, reducing the travel of the valve.

[0046] Regardless of the direction and / or magnitude of the offset, the control system can monitor deviations from the valve's initial closed position, which can indicate a change in operating conditions from the initial configuration. This deviation can be calculated at regular intervals or each time the valve element moves to the closed position. The control system can sense (e.g., via a position sensor) the new or deviated position of the valve element in the closed position and record the new position. The offset or deviation can be calculated by comparing the initial position and the new or current closed position (e.g., calculating the difference therebetween).

[0047] like Figure 4 As shown, once the new closed position is determined, the control system can then adjust the curve utilized when closing the valve (and in some embodiments, opening the valve). 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 deflected relatively closer to the open position) or modified to the right side of the graph (e.g., when the valve seat has deflected relatively farther from the open position).

[0048] By way of further example, via an adaptive control algorithm, the control system may utilize a newly sensed seated or closed position of the valve element (e.g., a measured deviation / offset from the closed or seated position) to 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.

[0049] like Figure 4 As shown, while the control system can dynamically update the offset of the seated or closed position, the control system can substantially maintain (e.g., completely maintain) the open position. For example, the control system can dynamically modify the distance between the open position and the closed position while substantially maintaining the position of the predetermined open position.

[0050] In other embodiments, the control system may modify the open position relative to changes in the closed position. In still other embodiments, the control system may dynamically modify the position of 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, flow rate, flow state, such as laminar flow, turbulent flow, or variations therebetween). 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).

[0051] In some embodiments, when the deviation exceeds a certain set point (e.g., a predetermined deviation band), a message and / or alarm may be generated to prompt maintenance and action to correct the deviation, optionally indicating the direction in which the deviation occurred. Such an alarm message may also include the possible cause of the deviation and recommended measures.

[0052] Using this adaptive speed-position profile control algorithm can help alleviate many of the aforementioned issues with seating events. In some embodiments, altering the valve seating approach velocity characteristics is one way to reduce / eliminate at least some of the undesirable characteristics of moving a valve between positions (e.g., as described above). For example, reducing the valve closing velocity before the valve is seated 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 interruption.

[0053] In some embodiments, the application of motor control technology with closed-loop variable speed and closed-loop torque control (e.g., control of the motor's power or current) can implement soft seating of the valve, with adaptive control enabling the control system to dynamically monitor and update various valve positions, such as closed and open positions. In some embodiments, the control system for the valve actuator can implement motor control technology, such as a direct current (DC) motor drive with field-oriented control or an alternating current (AC) variable frequency drive. The control system can further include one or more sensors for monitoring the position of the actuator output shaft (e.g., encoders or other position sensors) and one or more sensors for measuring outputs and / or inputs associated with components of the actuator, such as output shaft torque (e.g., via motor current or torque-force sensing devices), power consumption (e.g., current), and / or operating temperature of the motor. As the valve position approaches the seated position, implementing an algorithm for commanding a reduction in approach-to-seating speed can achieve a smoother, more controlled transition to the seated position. Once in the seated position, the algorithm transitions from a closed-loop speed-position mode to a closed-loop torque control mode, thereby increasing the actuator torque output to the desired final torque level. The motor is then de-energized and the valve is now securely fixed in the closed position.

[0054] In some embodiments, such monitoring of torque by the control system can indicate whether a valve is worn or sticking.Further, trend patterns in torque measurements can enable predictive maintenance.

[0055] As described above, in some embodiments, Figure 3 and Figure 4 In a somewhat similar manner to that shown, a control system is used to move a valve element between one or more positions in which the motion (e.g., rotational motion) of the valve element is free of physical hard stops. As described above, this configuration also lacks a hard seated position at the end of travel and the associated torque increase and torque trip. Such a valve configuration (e.g., a modulating control valve) can have a physical position and geometry that can shut off, fully open, and / or throttle flow between open and closed or closed positions that define different operating ranges.

[0056] In the example of a modulating control valve, such a valve can be used to precisely regulate process flow or pressure. Fluid flow can be measured directly by a flow sensor, or it can be measured by measuring the pressure differential across the valve.

[0057] Figure 5 is a diagram illustrating a method of operating a control system of a valve actuator, for example, wherein the position is unobstructed (e.g., without a hard stop). As described above, such a position can include a combination of multiple open positions of the valve element and a closed position or seated position without a hard stop.

[0058] refer to Figure 4 and 5 When moving a valve to a commanded or target position without 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 may have already overshot the commanded position, triggering a correction in the form of movement in the opposite direction. Because this correction is typically a relatively small movement, the duration of motor energization is also short, perhaps even just a quick pulse. The actuator may overshoot again and begin correcting in the original direction. This hunting / oscillation will continue until the error between the commanded and actual positions falls within the control loop's deadband parameter (e.g., the range in which the position error is small enough that no further action is required). If the deadband parameter (or other gain parameters) are not set correctly, the oscillation may continue indefinitely, shortening the actuator life and generating process disturbances in the flow loop. In some examples, the actuator may overheat (e.g., thermal trip), causing the actuator to be deactivated for a period of time to cool, during which time it is temporarily not actively controlling the process.

[0059] Implementing a closed-loop process algorithm as described above to regulate the reduction in approach velocity as the valve approaches a commanded position, flow rate, and / or desired pressure can produce a smooth, controlled transition from motion to stop. Overshoot and hunting / oscillation about desired process parameters can be reduced or eliminated, resulting in faster process startup, less wear on actuators and valves, and better process stability.

[0060] refer to Figure 4 and 5 , the offset can be characterized as a process error, where the error is a function of the difference between a set process variable (e.g., position, flow, and / or pressure) and the process setpoint for that process variable. The characteristics of this operating curve can be parameterized by the operator or dynamically calculated (e.g., learned) by implementing an auto-tuning algorithm. The latter provides 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, flowing materials, and / or equipment wear, all of which can affect actuator operation and process stability.

[0061] Valve actuator performance can be benchmarked using one or more initial valve positions to establish expected process characteristics. Over time, wear and buildup on the valve may cause these one or more positions to change, and the control system may update these positions to produce substantially the same process characteristics. When one or more positions deviate from the one or more baseline positions, an alarm is generated once the excursion exceeds an operator-defined deviation band. This alarm can alert operators and maintenance resources to changing system performance, which may indicate erosion of system health and potential system failure.

[0062] In some embodiments, the control system can monitor one or more valve characteristics (e.g., torque curve) 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 shut down. Utilizing dynamic direct torque measurement technology instead of or in addition to torque limiting technology can enable the actuator to monitor the torque generated throughout the valve movement. The torque curve can be benchmarked, and the torque curve of subsequent valve movements can be monitored and compared to the torque curve baseline.

[0063] As the actuator and valve wear and / or the environment and / or operating conditions change, the deviation between the actual measured torque curve and the reference torque curve will increase. As these deviations begin to exceed a deviation limit, a measure (e.g., one or more alarms) can be generated to alert operators and maintenance resources of the changing operating dynamics of the system, which indicates that the system health may be deteriorating. In some embodiments, analysis of the changing torque curve can be used to suggest problem areas in the system for investigation as the root cause of the deviation.

[0064] In some embodiments, the control system can monitor one or more thermal values ​​in the valve system. For example, when an actuator moves a valve, the prime mover of the system is the motor in the actuator, which generates heat during operation. The rate of heat rise can be determined in part by one or more of the following: (1) the number of movements 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 structure, thermal rating, and heat dissipation design of the motor.

[0065] For example, repeatedly running a motor at maximum speed with a high load in a very warm environment will result in a high heat rise (e.g., temperature increase). Because the components of the actuator have rated operating temperatures 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 temperatures can seriously damage the equipment or even cause it to fail. Typically, if the actuator exceeds the rated operating temperature of the motor, the actuator stops to dissipate the heat until the temperature returns to the operating range.

[0066] In some embodiments, because the actuator device may include mission-critical applications, shutting down the actuator for cooling may not be acceptable.

[0067] In some embodiments, the control system can monitor the current temperature and / or the rate of increase in the motor temperature. Based on the actual motor temperature and / or the rate of change, the control system can predict when the actual motor temperature will exceed a specified temperature. In this case, the adaptive control algorithm may reduce the speed of the motor, thereby reducing thermal efficiency and allowing the actuator to continue operating within the specified operating range. While this measure may not completely prevent the actual motor temperature from eventually exceeding the specified temperature, such throttling of the motor will expand the actuator's operating window.

[0068] As the rate of thermal rise decreases, throttling can be reduced until the motor temperature begins to rise again or full operating capacity is restored.

[0069] Although certain embodiments have been described and shown in the drawings, such embodiments are merely exemplary and do not limit the scope of the present disclosure, and the present disclosure is not limited to the exact construction and arrangements shown and described, as various other additions and modifications, as well as deletions, to the described embodiments will be apparent to those skilled in the art. Accordingly, the scope of the present disclosure is limited only by the literal language of the appended claims and their legal equivalents.

Claims

1. A valve system comprising: a valve actuator for controlling a position of a valve element in the valve to control flow through at least a portion of the valve; as well as A control system for controlling the valve actuator, the control system being configured to: commanding the valve actuator to move the valve element toward a first, unobstructed position in the valve to enable fluid flow through the at least a portion of the valve; commanding the valve actuator to move the valve element to a second position in the valve to reduce or increase fluid flow through the at least a portion of the valve; monitoring a first characteristic of the valve system during movement of the valve element and as the valve element moves along a path toward the second position; At a predetermined position along the path, when the valve element approaches and reaches the second position along the path, switching to monitoring a second characteristic of the valve system that is different from the first characteristic; as well as An offset of the second position is determined based on at least one of the first and second monitored characteristics of the valve system.

2. The valve system according to claim 1, wherein: The control system is further configured to: reducing the velocity of the valve element when the valve element is at a selected point in its travel toward the second position; and The selected point for decreasing the rate of the valve element is updated based on the determined offset of the second position.

3. The valve system according to claim 1, wherein: The control system is further configured to at least one of: determining that the second position of the valve element has shifted to a position relatively closer to the first position; or It is determined that the second position of the valve element has shifted to a position relatively away from the first position.

4. The valve system according to claim 1, wherein: The determined offset comprises a deviation between the second position and a previous closed position that was previously configured in the valve actuator.

5. The valve system according to claim 1, wherein: The first characteristic of the valve system includes a position of the valve element, and the second characteristic of the valve system includes a torque of the valve actuator.

6. The valve system according to any one of claims 1 to 5, wherein: The at least one characteristic includes 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, or pressure in the valve.

7. The valve system according to any one of claims 1 to 5, wherein: 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 first position.

8. The valve system according to claim 7, wherein: The at least one other characteristic comprises at least one of: a flow rate through the valve, a type of flow through the valve, a position of the valve element, or a pressure in the valve.

9. The valve system according to any one of claims 1 to 5, wherein: The first unobstructed position comprises a position of the valve element without a hard stop, and wherein the second position comprises a hard stop.

10. The valve system according to any one of claims 1 to 5, wherein: The control system is further configured to: updating the position of the second position based on the detected offset; and The speed-varying position of the valve element is updated based on the detected excursion.

11. The valve system according to any one of claims 1 to 5, wherein: The control system is further configured to substantially maintain the position of the first position while actively adjusting the position of the second position each time a deviation of the second position is detected.

12. The valve system according to any one of claims 1 to 5, wherein: The control system is further configured to generate a warning when the offset is outside of a selected range of offset values.

13. The valve system according to any one of claims 1 to 5, wherein: The second 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 the torque of the valve actuator reaches a selected value.

14. A valve system comprising: a valve actuator for controlling fluid flow through at least a portion of the valve via the valve element; as well as A control system for controlling the valve actuator, the control system being configured to: commanding the valve actuator to move the valve element from an initial position to a target position in the valve to decrease or increase fluid flow through the at least a portion of the valve; monitoring at least one first characteristic of the valve system during movement of the valve element toward the target position; detecting a position of the target location based on the monitored at least one first characteristic of the valve system; monitoring at least one second characteristic of the valve actuator when the valve element reaches the target position; and The control system is further configured to: moving the valve element into contact with a valve seat of the valve system in the target position and then forcing the valve element into the valve seat until the torque of the valve actuator reaches a selected value; and Each time the valve element moves to the target position, the position of the initial position is substantially maintained while actively adjusting the position of the target position based on the monitored at least one first characteristic of the valve system.

15. The valve system according to claim 14, wherein: The control system is configured to monitor the 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 the valve element to a closed position with the valve actuator to substantially inhibit fluid flow through at least a portion of the valve; monitoring at least one characteristic of the valve system during movement of the valve element toward the closed position; monitoring at least another characteristic of the valve system during movement of the valve element toward the open position; determining a deviation from the closed position based on the at least one monitored characteristic of the valve system; as well as The valve element is moved into contact with a valve seat of the valve system in the closed position and then forced into the valve seat until the torque of the valve actuator reaches a selected value.

17. The method of claim 16, the determined offset comprising a deviation between the closed position and a previous position that was previously configured in the valve actuator.

18. The method according to claim 16, further comprising: monitoring a position of the valve element as the valve element moves along a path toward the closed position; as well as At a location along the path, as the valve element approaches and reaches the closed position along the path, a switch is configured to monitor at least one of torque or current of the valve actuator.

19. The method according to any one of claims 16 to 18, further comprising: reducing the velocity of the valve element when the valve element is at a selected point in its travel toward the closed position; and The selected point for decreasing the rate of the valve element is updated based on the determined offset from the closed position.

20. The method of any one of claims 16 to 18, further comprising locating the control system remotely from the valve.

21. The method according to any one of claims 16 to 18, further comprising: moving the valve element with the valve actuator toward an open position in the valve without a hard stop to enable fluid flow through the at least a portion of the valve; and Each time the valve element moves to the closed position, the position of the open position is substantially maintained while actively adjusting the position of the closed position based on the at least one monitored characteristic of the valve system.

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