Improving control valve accuracy using long-stroke position transducers.

Abstract

Position transmitting devices are configured for use on control valves. These configurations can convert a linear position of a closure member on the control valve to an angular position of a magnet. A sensor proximate to the magnet can generate a signal in response to the angular position. In one implementation, a valve positioner or controller can process the signal to identify the position of the closure member relative to the seat.

Description

[Background technology]

[0001] Flow control devices are used in a variety of applications. A control valve is a type of flow control device used in industrial equipment that comprises part of a process line. The design of these devices is intended to precisely regulate flow to meet process parameters. Precision issues with control valves can disrupt the process, resulting in lower yields and reduced quality. In large industrial operations, these issues can lead to significant expenses due to the downtime required to troubleshoot and repair or replace the problematic device(s). Summary of the Invention

[0002] The subject matter of this disclosure relates to improvements to address accuracy issues in control valves. Of particular interest are embodiments of devices or mechanisms that can convert linear position to angular position. Devices of the proposed design may include a linearly translating shaft that forms an inclined surface. A rotatable mechanism may contact the inclined surface. In one implementation, the mechanism can register an angular position that correlates to a contact point on the inclined surface. This feature is beneficial because it provides a more reliable and accurate measurement of component position within a control valve than traditional linkage mechanisms, as the proposed design is much less complex and less susceptible to vibration or other influences that can affect the measurement.

[0003] Measurement accuracy is important for various control valve operations. For example, position measurement is important for maintaining the closure member in a precise position relative to the seat. This position regulates flow to achieve appropriate process parameters. Control valves may also use position measurement to participate in certain operating “modes” of the device. The “full open” mode ensures that the closure member reaches the furthest position from the seat. The “tight shutoff” mode may place the closure member in its closed position (contacting the seat) in response to a commanded position below a “low limit.” For example, if the low limit is 10%, the closure member will contact the seat at commanded positions below 10% and operate normally at commanded positions above 10%. The tight shutoff mode is useful for preventing operating conditions that result in the closure member being too close to the seat. These operating conditions cause the working fluid to flow at high flow rates or velocities that can cause wear and damage that can degrade the performance and shorten the life of the valve assembly. [Brief explanation of the drawings]

[0004] Reference will now be made briefly to the accompanying drawings, in which:

[0005] [Figure 1] FIG. 1 is a schematic diagram of a position transmission device used in a control valve. [Figure 2] FIG. 2 is a perspective view illustrating an exemplary structure for a position-transmitting device in exploded form. [Figure 3] FIG. 3 is a perspective view of the exemplary structure of FIG. 2 in assembled form. [Figure 4] FIG. 4 is an elevational view of a cross section of the exemplary structure of FIG. [Figure 5] FIG. 5 is a perspective view of the exemplary structure of FIG. 3 in place for an example control valve. [Figure 6] FIG. 6 is a schematic diagram of the example position transfer device of FIG. 1 with the magnet in a first angular position. [Figure 7] FIG. 7 is a schematic diagram of the example position transfer device of FIG. 1 with the magnet in a second angular position.

[0006] Where applicable, like reference characters designate identical or corresponding components and units throughout the several figures, which are not drawn to scale unless otherwise indicated. Embodiments disclosed herein may include elements that appear in one or more of the several figures or in combinations of multiple figures. Moreover, the methods are merely illustrative and may be modified, for example, by reordering, adding, removing, and / or altering individual steps.

[0007] The drawings and any descriptions herein use examples to disclose the invention. These examples, including the best mode, enable any person skilled in the art to practice the invention, including making and using any device or system and performing any incorporated methods. Elements or features described in the singular and preceded by the words "a" or "an" should be understood as not excluding a plurality of such elements or features, unless such exclusion is expressly stated. References to "one embodiment" or "one implementation" should not be interpreted as excluding the existence of additional embodiments or implementations that also incorporate the recited features.

[0008] The features of the embodiments shown in the above figures will now be described. These embodiments eliminate the need for mechanical linkages to measure component position on the control valve. These linkages are often large and bulky. They also tend to extend well outside the structural envelope of the control valve. The designs herein, on the other hand, fit entirely within this structural envelope. Other embodiments may be contemplated within the scope of this disclosure.

[0009] 1 shows a schematic diagram of an exemplary embodiment of a position transmitting device 100. This example is part of a valve assembly 102 that includes a valve positioner 104 (or "controller 104") coupled to an actuator 106. A valve stem 108 can connect the actuator 106 to a valve 110. This feature allows the actuator 106 to regulate the movement of a closure member 112 relative to a seat 114. The controller 104 may also include a position sensor 116. As shown, the position transmitting device 100 can include a sensor target unit 120 proximate to the position sensor 116. The sensor target unit 120 can communicate with a transmission unit 122 that is coupled to the valve stem 108.

[0010] Generally, the position transmitting device 100 can be configured to convert a linear position into an angular position. These configurations may employ components that can connect to a linear drive or linear load, as is typical for many flow controls (including control valves). The components of the device 100 can fit into a small, compact form factor. This feature can provide a more robust mechanism because it is less susceptible to external influences, such as vibration, that can prevent the use of conventional linkage systems for control valves. As an additional advantage, the proposed components and mechanisms can be integrated with one another to reduce or eliminate "backlash" or "play" in the measurement system. This feature can provide more accurate measurements than any conventional linkage in the field.

[0011] The valve assembly 102 may be configured for use in systems that transport materials. These configurations can be connected in-line with conduits, such as pipes and pipelines, as part of one or more process lines that transfer fluids. Hydrocarbon operations are known to utilize these devices to regulate the flow of oil and natural gas (including liquefied natural gas or "LNG") from extraction points to process facilities or within the process facilities themselves.

[0012] The controller 104 may be configured to exchange and process signals. These configurations may be connected to a control network (or "distributed control system" or "DCS") that maintains the operation of all devices on the process line to ensure that material flows according to the process. The DCS may generate control signals having operating parameters that describe or define the operation of the valve assembly 102 for this purpose. For example, the operating parameters may define the command position of the valve assembly 102.

[0013] The actuator 106 may be configured to generate a load that acts against the pressure of the material. These configurations can use pneumatic devices, although electric or electronic devices (e.g., motors) can function as well. The pneumatic device may have a diaphragm inside a housing. In operation, the controller 104 may deliver gas or "instrument air" as a pneumatic signal. This instrument air signal varies the pressure or load against the diaphragm inside the housing of the actuator 106. The stem 108 directs the load to the valve 110. The parameters of the pneumatic signal depend in large part on the commanded position of the valve assembly 102.

[0014] The valve 110 may be configured to fix flow parameters to a process line. These configurations often include hardware that mates with a pipe or pipeline. The fabrication of this hardware often matches the properties of the material, including its composition or "phase," e.g., solid, fluid, or solid-liquid mixture. The closure member 112 may embody a plug, ball, butterfly valve, or similar device that can contact a seat 114 to prevent flow. The positioning of the closure member 110 relative to the seat 112 allows for more or less material flow through the valve 106 to meet process parameters.

[0015] The position sensor 116 may be configured to generate data. In these configurations, a non-contact modality (e.g., magnetic) may be used to generate a measured position value of the closure member 110. During operation, the controller 104 can process signals from both the DCS and the positioner sensor 116 to set a pneumatic signal to operate the actuator 106 and maintain the closure member 112 in a commanded position. This feature ensures that material flow through the valve 106 meets process parameters. The use of a non-contact modality allows the controller 104 to be easily separated from (and installed on) the valve assembly 102. This feature simplifies maintenance and, in some applications, allows a technician to remove and replace the controller 104 as part of the task of repairing, upgrading, or maintaining the device.

[0016] The sensor target unit 120 may be configured to communicate angular position. These configurations may embody devices that interface with the non-contact modality of the sensor 116. These devices may include magnets, particularly if the sensor 116 is of a type that responds to magnetic fields, such as a Hall Effect sensor. However, other devices compatible with this type of sensor 116 may also be prevalent. These other types may employ optical or ultrasonic technology, for example.

[0017] The transmission unit 122 can be configured to set this angular position. These configurations can embody devices that move in coordination with the linear drive of the valve assembly 102. These devices may include a linearly moving shaft; however, rotatable mechanisms are prevalent as well. In one implementation, a translation shaft can set the angular position of the sensor target unit 120 to correspond to the position of the linear drive and ultimately the position of the closure member 112.

[0018] FIG. 2 is a perspective view, in exploded form, of an example structure for the position-transmitting device 100 of FIG. 1 . The structure may include a body 124 having an internal bore structure that creates vertical axes 126, 128. The bore structure may terminate in openings 130 on the body 124, shown here on opposing sides 132, 134 and opposing sides 136, 138, respectively. A flange 140 may surround each of the openings 130. In one example, the structure may include a bushing 142 that is inserted into the openings 130 on the sides 132, 134. A seal 144 may also be secured to the flange 140 on the sides 132, 134. Both the bushing 142 and the seal 144 may have a bore to accommodate a shaft 146 that may be inserted through the body 124. The shaft 146 may have ends 148, 150. A slot 152 may extend through its surface. The slot 152 may extend lengthwise along the shaft 146 and terminate at locations 154, 156 set inwardly from the ends 148, 150.

[0019] The structure may be configured with components to generate an angular position that reflects the linear position of the shaft 146. The structure may include a rotating housing 158 that mates with the flange 140 on the side 136 of the body 124. A bushing 160 may reside within a bore of the rotating housing 158. The bushing 160 may have a through hole that receives a first portion of the sensor interface 162. A magnet 164 may reside within a second portion of the sensor interface 162. The magnets 164 may be configured diametrically opposed to each other. Often, the second portion of the sensor interface 162 has a larger outer diameter than the first portion. A disk 166 may be affixed to an exposed end of the first portion of the sensor interface 162. The disk 166 may be coupled to a pin member 168, shown here with a boss 170 perpendicular to the axis 128. In one implementation, the structure may include a biasing unit 172 that may bias the pin member 168 in one direction D1 about the axis 128. The biasing unit 172 may include a spring plate 174 having a boss 176 extending parallel to the axis 128. The boss 176 may engage a corresponding aperture on the pin member 168. The biasing unit 172 may use a spring 178, typically a coil spring or a torsion spring. The spring 178 may reside within the spring plate 174. In one example, a cover 180 may be secured to the flange 140 on the side surface 138 to enclose the biasing unit 172, including the coil spring 178, inside the bore structure of the body 124.

[0020] 3 is a perspective view showing the assembled position-transmitting device 100 of FIG. 2. The assembly can set an angular position θ of the magnet 164 on the sensor interface 162 about the axis 128. This angular position can correspond to a linear position L of the shaft 146 on the axis 128.

[0021] FIG. 4 shows an elevational view of a cross section of the position transmitting device 100 of FIG. 3 taken along line 4-4. The slot 152 may have a depth "d" that varies between the locations 154 and 156. In one implementation, the depth d may vary linearly to form the inclined surface 182. A boss 170 on the pin member 168 may contact the inclined surface 182. A coil spring 178 ( FIG. 2 ) may generate a preload or preset tension direction D1. This preload biases the pin member 168 against the inclined surface 182. In use, the contact point of the boss 170 with the inclined surface 182 sets the angular position θ of the disk 166, which corresponds to the angular position θ of the magnet 164 on the sensor interface 162. Translation of the shaft 146 to a different position on the axis 126 (e.g., from a first position to a second position) changes the depth d of the slot 152 at the contact point between the boss 170 and the inclined surface 182. This change in depth d results in a different angular position θ. As depth d increases at the contact point, the preload of coil spring 178 (FIG. 2) urges pin member 168 in direction D1, ensuring that boss 170 remains in contact with angled surface 182.

[0022] 5 shows a perspective view of the position transfer device 100 of FIG. 2 in the example of the valve assembly 102 of FIG. 1. The structure may mount a magnet 164 (FIG. 3) in proximity to the sensor 116 (FIG. 1) on the controller 104. A tie bar 184 may couple one end of the shaft 146 to a transfer block 186 on the valve assembly 102. In this way, the position of the transfer block 186 is transferred directly to the shaft 162 to set the angular position θ of the magnet 146 (FIG. 4).

[0023] 6 and 7 show schematic diagrams illustrating the operation of the device of FIG. 5. In FIG. 6, the magnet 164 has a first angular orientation θ1 corresponding to a first linear position L1 of the shaft 146. The tie bars 184 ensure that the first linear position L1 corresponds to the position of the transfer block 186, which itself moves in coordination with the valve stem 108. FIG. 7 shows the magnet 164 at a second angular orientation θ2 corresponding to a second linear position L2 of the shaft 146. This second linear position L2 indicates that the transfer block 186 will change position, for example, moving upward in response to movement of the valve stem 108 (indicating the position of a closure member (not shown) within the valve assembly 102).

[0024] In view of the above, the improvements herein better reflect the operation of a control valve or similar flow control. These mechanisms may provide a more accurate measurement of the position of a closure member compared to the same measurement by a conventional linkage measurement system. The resulting values ​​may prove useful in maintaining the accuracy of the control valve.

[0025] Examples including specific elements or items (one or more of which may be combined with other elements and items) are described below to illustrate embodiments contemplated within the scope and spirit of the present disclosure. This scope includes and is contemplated by those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they have equivalent structural elements that differ insignificantly from the literal language of the claims.

Claims

1. 1. A valve assembly comprising: A pneumatic actuator; a valve stem coupled to the pneumatic actuator; a shaft coupled to the valve stem and configured to move simultaneously with the valve stem; a rotatable mechanism coupled to the shaft, the rotatable mechanism including a magnet having an angular position corresponding to a linear position of the valve stem; a slot extending longitudinally within the shaft, the rotatable mechanism engaging the slot.

2. A valve assembly, A pneumatic actuator; a valve stem coupled to the pneumatic actuator; a shaft coupled to the valve stem and configured to move simultaneously with the valve stem; a rotatable mechanism coupled to the shaft, the rotatable mechanism including a magnet having an angular position corresponding to a linear position of the valve stem; a slot extending longitudinally within the shaft and having a variable depth, the slot configured to receive at least a portion of the rotatable mechanism to set the angular position of the magnet.

3. an inclined surface on the shaft, the rotatable mechanism engaging the inclined surface; The valve assembly of claim 1 further comprising:

4. a biasing unit coupled to the rotatable mechanism, the biasing unit biasing the rotatable mechanism against the shaft; The valve assembly of claim 1 further comprising:

5. a coil spring engaging the rotatable mechanism and biasing the rotatable mechanism against the shaft; The valve assembly of claim 1 further comprising:

6. The valve assembly of claim 1 , wherein the shaft is aligned with an axis parallel to the valve stem.

7. 2. The valve assembly of claim 1, wherein the magnet rotates about an axis perpendicular to the shaft.

8. 2. The valve assembly of claim 1, wherein the magnet comprises a pair of diametrically opposed magnets.

9. a tie bar connecting the end of the shaft to the valve stem; The valve assembly of claim 1 further comprising:

10. 1. A valve assembly comprising: A seat and a closure member movable relative to the seat; a position transmitting device coupled to the closure member, the position transmitting device having a first movable member and a second movable member including a magnet, the first movable member taking a linear position corresponding to an arrangement of the closure member relative to the seat, and the second movable member setting an angular position of the magnet to correspond to the linear position of the first movable member; The valve assembly, wherein the position transmitting device includes a slot extending in a direction of movement of the first movable member, the second movable member engaging the slot.

11. A valve assembly comprising: A seat and a closure member movable relative to the seat; a position transmitting device coupled to the closure member, the position transmitting device having a first movable member and a second movable member including a magnet, the first movable member taking a linear position corresponding to an arrangement of the closure member relative to the seat, and the second movable member setting an angular position of the magnet to correspond to the linear position of the first movable member; the position transmitting device includes a slot extending in a direction of movement of the first movable member and having a variable depth, the slot configured to receive at least a portion of the second movable member to set the angular position of the magnet.

12. 11. The valve assembly of claim 10, wherein the first movable member translates in the same direction as the closure member.

13. 11. The valve assembly of claim 10, wherein the first movable member translates on an axis parallel to an axis of movement of the closure member.

14. The valve assembly of claim 10 , wherein the second movable member rotates the magnet.

15. 11. The valve assembly of claim 10, wherein the second movable member rotates the magnet about an axis perpendicular to an axis of movement of the closure member.

16. A control valve, a valve having a closure member, a seat, a valve stem, and an actuator; a measurement system configured to measure the position of the closure member, A sensor, a shaft coupled to the closure member, the shaft being movable along a first axis to a position corresponding to the placement of the closure member relative to the seat; a pair of magnets coupled to the shaft and proximate to the sensor, the pair of magnets being rotatable about a second axis perpendicular to the first axis; a measurement system including a slot extending longitudinally within the shaft, the rotatable mechanism including the pair of magnets engaging the slot.

17. A control valve comprising: a valve having a closure member, a seat, a valve stem, and an actuator; a measurement system configured to measure the position of the closure member, A sensor, a shaft coupled to the closure member, the shaft being movable along a first axis to a position corresponding to the placement of the closure member relative to the seat; a pair of magnets coupled to the shaft and proximate to the sensor, the pair of magnets being rotatable about a second axis perpendicular to the first axis; a measurement system including a slot extending longitudinally within the shaft and having a variable depth, the slot configured to receive at least a portion of a rotatable mechanism comprising the pair of magnets to set an angular position of the pair of magnets.

18. The measurement system includes:

17. The control valve of claim 16, including a cylinder coupled to the shaft and holding the magnets diametrically opposed to one another.

19. The measurement system includes:

17. The control valve of claim 16, including a rotatable disk aligned on the second axis and coupled to the shaft and the pair of magnets.

20. The measurement system includes:

17. The control valve of claim 16, including a coil spring that biases the pair of magnets in one direction about the second axis.

21. The measurement system includes: The control valve of claim 16 including a tie bar connecting the shaft to the valve stem.

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