JP7814550B2 - Improving control valve accuracy using short-stroke position transducers. - Google Patents

Description

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 a control valve can disrupt the process, reducing yield or reducing quality. In large industrial operations, these problems can result in significant costs due to the downtime required to troubleshoot and repair or replace problematic devices.

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 coupled to a rotatable mechanism. In one embodiment, this mechanism can register an angular position that directly correlates to the linear position of the shaft. This feature is beneficial because the proposed design is much less complex and less susceptible to vibration or other influences that can affect the measurement, providing more reliable and accurate measurement of component position within a control valve than traditional linkage mechanisms.

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" on 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 "lower limit." For example, if the lower 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 reduce the performance and life of the valve assembly.

Reference will now be made briefly to the accompanying drawings, in which:
FIG. 1 shows a schematic diagram of a position transmission device used in a control valve. FIG. 2 shows a perspective view, in exploded form, of an exemplary structure for a position-transmitting device. FIG. 3 shows a rear elevation view of the exemplary structure of FIG. 2 in assembled form. FIG. 4 shows an elevational view of a cross section of the exemplary structure of FIG. 2 in assembled form. FIG. 5 shows a perspective view of the exemplary structure of FIG. 2 in assembled form. FIG. 6 shows a perspective view of the exemplary structure of FIG. 3 in place for an example control valve. FIG. 7 shows a schematic diagram of the example position-transmitting device of FIG. 1 with the magnet in a first angular position. FIG. 8 shows a schematic diagram of an example of the position transfer device of FIG. 1 with the magnet in a second angular position.

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

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.

We now describe features of the embodiments shown in the drawings above. These embodiments eliminate the need for mechanical linkages to measure component position on a 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 within the scope of this disclosure.

FIG. 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 may 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 may include a sensor target unit 120 proximate to the position sensor 116. The sensor target unit 120 may communicate with a transmission unit 122 coupled to the valve stem 108.

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, as it is less susceptible to external influences such as vibrations that can prevent the use of conventional linkage systems for control valves. As an additional advantage, the proposed mechanism 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.

The valve assembly 102 may be configured for use in systems that transport materials. These configurations may 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.

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. To this end, the DCS may generate control signals having operating parameters that describe or define the operation of the valve assembly 102. For example, the operating parameters may specify a commanded position of the valve assembly 102.

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. Pneumatic devices 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 actuator 106 housing. 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.

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.

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 for 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.

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.

The transmission unit 122 may be configured to set this angular position. These configurations may embody devices that move in coordination with the linear drive of the valve assembly 102. These devices may include a linearly translating shaft; however, rotatable mechanisms are equally prevalent. In one embodiment, the translating shaft may 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.

FIG. 2 shows an exploded perspective view of an example structure for the position-transmitting device 100 of FIG. 1 . The structure can include a body 124 having an internal bore structure that creates vertical axes 126 and 128. The bore structure can terminate in openings 130 on the body 124, shown here on opposing sides 132 and 134 and opposing sides 136 and 138, respectively. A flange 140 can surround each of the openings 130. In one example, the structure can include a bushing 142 that is inserted into the openings 130 on the sides 132 and 134. A seal 144 can be secured to the flange 140 on the sides 132 and 134. The example seal 144 can prevent dirt and debris from entering the interior of the device. This feature makes the proposed structure more suitable for harsh, corrosive environments and low-temperature applications. In one embodiment, one of the seals 144 can incorporate a cap 146. Both the bushing 142 and the seal 144 may have a bore for receiving the drive shaft 148. In one embodiment, the drive shaft 148 may include a driven portion 150, shown here as an elongated cylindrical member that can be inserted into the body 124 from the side 132. The cylindrical member may have two sections 152, 154 of different outer diameters OD. The sections 152, 154 may abut each other at a shoulder 156. A sleeve 158 may be inserted into the body 124 through the side 134. The sleeve 158 may have a throughbore 160 that can receive the second section 154 of the driven portion 150. A biasing unit 162 may be inserted over the exposed end of the second section 154. The biasing unit 162 may include one or more springs, such as Belleville washers or similar constant force springs. In one embodiment, a nut 164 may be threaded onto the exposed end.

The structures may be configured with components to create an angular position that reflects the linear position of the shaft 148. These structures may include a rotating housing 166 that mates with a flange 140 on the side surface 136 of the body 124. A bushing 168 may reside within the bore of the rotating housing 166. The bushing 168 may have a through bore that can receive a first portion of the sensor interface 170. A magnet 172 may reside within the second portion of the sensor interface 170. The magnets 172 may be configured diametrically opposed to each other. Often, the second portion of the sensor interface 170 has a larger outer diameter than the first portion. A disk 174 may be affixed to the exposed end of the first portion of the sensor interface 170. The disk 174 may include a boss or pin 176 that extends along the axis 128 toward the drive shaft 148. In one example, a cover 178 may be secured to the flange 140 on the side surface 138 to close the bore structure of the body 124.

3 and 4 show additional views of the position transmitting device of FIG. 2. FIG. 3 shows a rear elevation view in partially assembled form. The cover 178 has been removed to expose the interior of the body 124. As shown, fasteners F may penetrate the disk 174 into the sensor interface 170 (FIG. 2). The shoulder 156 of the driven portion 150 and the end of the sleeve 158 may form an intervening gap G within the drive shaft 148. Thrust washers W may bound the gap G. As best shown in the cross-sectional view of FIG. 4, the pin 176 may extend within the intervening gap G and between the thrust washers W. Tightening the nut 164 compresses the spring 162, creating a preload on the pin 176. This preload clamps or "squeezes" the pin 176 into the intervening gap G, thus coupling the rotatable disk 174 to the translation drive shaft 148.

Figure 5 shows a front perspective view of the position transfer device 100 of Figure 2 in assembled form. Engagement between the drive shaft 148 and the rotatable disk 174 can set an angular position θ of the magnet 172 on the sensor interface 170 about the axis 128. This angular position can correspond to a linear position L of the drive shaft 148 on the axis 126. Translation of the driven portion 150 to a different position on the axis 126 (e.g., from a first position to a second position) causes the disk 174 to rotate within the main housing 124, which in turn results in a different angular position θ of the magnet 172.

Figure 6 shows a perspective view of the position transmission device 100 of Figure 2 in the example valve assembly 102 of Figure 1. This structure may mount a magnet 164 (Figure 2) in proximity to a sensor 116 (Figure 1) on the controller 104. A tie bar 180 may couple one end of the driven portion 150 to a transmission block 182 on the valve assembly 102. In this manner, the position of the transmission block 186 is directly transmitted to the drive shaft 148 to set the angular position θ of the magnet 172 (Figure 4).

7 and 8 show schematic diagrams illustrating the operation of the device of FIG. 6. In FIG. 7, the magnet 172 has a first angular orientation _θ1 corresponding to a first linear position _L1 of the drive shaft 148. The tie bars 180 ensure that the first linear position _L1 corresponds to the position of the transfer block 182, which itself moves in coordination with the valve stem 108. FIG. 8 shows the magnet 172 at a second angular orientation _θ2 corresponding to a second linear position _L2 of the drive shaft 148. This second linear position _L2 indicates a change in position of the transfer block 180, for example, moving upward in response to movement of the valve stem 108. This new position may indicate that the closure member (not shown) is moving away from its seat (not shown) in the valve assembly 102.

Examples including specific elements or items (one or more of which may be combined with other elements and items) appear below and describe 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 (18)

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 pin engaged with the shaft and a magnet having an angular position corresponding to a linear position of the valve stem;
a sleeve having a through hole for receiving the shaft;
Equipped with
The valve assembly , wherein the pin extends between the shaft and the sleeve . 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 pin engaged with the shaft and a magnet having an angular position corresponding to a linear position of the valve stem;
a sleeve having a through hole for receiving the shaft;
a biasing unit that generates a preload to clamp the pin between the shaft and the sleeve. 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 pin engaged with the shaft and a magnet having an angular position corresponding to a linear position of the valve stem;
a sleeve having a through hole for receiving the shaft;
a spring washer disposed on the end of the shaft;
a nut threaded onto the end of the shaft in a position that compresses the spring washer ;
The pin extends between the shaft and the sleeve. 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 pin engaged with the shaft and a magnet having an angular position corresponding to a linear position of the valve stem;
The shaft is configured to preload the pin. 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 pin engaged with the shaft and a magnet having an angular position corresponding to a linear position of the valve stem;
a biasing unit coupled to the shaft;
The biasing unit generates a preload that acts on the pin through the shaft. 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 pin engaged with the shaft and a magnet having an angular position corresponding to a linear position of the valve stem;
The shaft comprises a first portion and a second portion extending within the first portion and having a reduced diameter section forming a shoulder to thereby receive the pin between the shoulder and an end of the first portion. A valve assembly as claimed in any preceding claim, wherein the shaft translates along an axis perpendicular to the pin. A valve assembly according to any preceding claim, wherein the pin translates radially about an axis perpendicular to the shaft. A valve assembly according to any preceding claim, wherein the pin extends perpendicular to the shaft. The valve assembly of any one of claims 1 to 6 , further comprising a tie bar connecting the shaft to the valve stem. 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 comprising: a shaft; a pin engaged with the shaft; a rotatable disk coupled to the pin; and a magnet coupled to the rotatable disk;
Linear translation of the shaft rotates the rotatable disk to change the angular position of the magnet about an axis perpendicular to the shaft ;
The valve assembly further comprises a biasing unit coupled to the shaft, the biasing unit applying a preload to the pin . The valve assembly of claim 11, wherein the shaft has two portions that form a gap for receiving the pin. A valve assembly according to any one of claims 1 to 6 , wherein the shaft has two portions separated from each other by the pin. 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 pin extending perpendicular to the first axis and having a first end extending into the shaft;
a measurement system comprising a pair of magnets coupled to the pin and proximate to the sensor, the pair of magnets being rotatable about a second axis perpendicular to the first axis;
a sleeve having a through hole for receiving the shaft;
Equipped with
The pin extends between the shaft and the sleeve . The measurement system includes:
15. The control valve of claim 14 , further comprising a cylindrical body coupled to the pin and holding the magnets diametrically opposed to one another. The measurement system includes:
The control valve of claim 14 including a rotatable disk aligned on the second axis and receiving the second end of the pin. The measurement system includes:
The control valve of claim 14 including a spring load acting on the shaft to clamp the first end of the pin. The measurement system includes:
The control valve of claim 14 including a tie bar connecting the shaft to the valve stem.