Abstract:
Embodiments of a valve positioner that can maintain operation of the control valve despite failures in one or more components. These embodiments reduce downtime by allowing in-situ repair to occur on the valve positioner. In one embodiment, the valve positioner incorporates a by-pass component, which can utilize control input signals (e.g., a 4-20 mA signal) to energize one or more components (e.g., a current-to-pressure converter) to cause the control valve to modulate fluid flow without the digital microprocessor and/or related components.

Description:
BACKGROUND 
       [0001]    The subject matter disclosed herein relates to control valves and, in particular, to embodiments of a valve positioner for control valves. 
         [0002]    Control valves regulate transmission and distribution of fluids (e.g., liquids and gases). These devices integrate into process control systems in a wide variety of industries. Examples of process control systems form a control loop with remote sensors and other feedback elements to monitor process conditions (e.g., temperature, pressure, etc.). The control loop can generate signals that cause the control valve to modify the flow of fluid in response to changes in the process conditions. 
         [0003]    Many control valves integrate valve positioners with digital components (e.g., microprocessors) that can process these signals. These digital components afford the control valve with precise control and functionality. Certain types of digital components can also expand data processing and communication capabilities of the valve positioner. These features can improve the quality, accuracy, and speed of the control valve to respond to changes in the process conditions. 
         [0004]    Unfortunately, although digital-based valve positioners are more powerful and accurate than conventional mechanical and/or early digital devices, these types of valve positioners still have reliability issues and can fail. Failures often lead to valve downtime for repair and/or replacement of the defective components. More important, however, is that failures that require maintenance of the control valve can render the process system inoperable for extended periods of time. The resulting downtime can lead to expensive production delays and, possibly, run afoul of regulations set forth by any number of government organizations (e.g., the Environmental Protection Agency (EPA), the Occupational Safety and Health Administration (OSHA), etc.). 
         [0005]    Most solutions that address the reliability of digital components provide little relief to shorten, or to avoid, downtime of control valves that utilize digital-based valve positioners. For example, some control valves may integrate a mechanical actuator that can change fluid flow in lieu of the digital components. The mechanical actuator does not operate automatically in this configuration. Rather, maintenance and/or operations personnel must intervene to manually operate the mechanical actuator. Other solutions integrate solenoids with the valve positioner to modulate the flow of fluid through the control valve. However, solenoids provide only binary operation (e.g., on/off), which does not allow finite modulation of flow through the control valve. On the other hand, still other solutions include redundant control valves and/or fluid circuits into the process system. The control system and/or operations personnel can divert flow into these redundant circuits to maintains operation of the process in parallel with repair of the defective control valves. Although effective to remedy potential downtime, these redundant systems still require additional hardware and software that can add significant component cost and complexity to the process line and control system. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    This disclosure describes improvements in valve positioners that allow control valves to continue to operate despite failures in one or more digital components (e.g., the microprocessor). These improvements reduce downtime by allowing in-situ repair to occur on the valve positioner. As set forth more below, this disclosure presents various embodiments of a valve positioner that incorporates a by-pass component, which can utilize control input signals (e.g., a 4-20 mA signal) to maintain operation of the control valve to modulate fluid flow without the digital microprocessor and/or related components. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Reference is now made briefly to the accompanying figures, in which: 
           [0008]      FIG. 1  depicts a perspective view of an exemplary embodiment of a valve positioner as part of a control valve; 
           [0009]      FIG. 2  depicts a perspective, exploded assembly view of the valve positioner of  FIG. 1 ; 
           [0010]      FIG. 3  depicts a schematic diagram of an exemplary embodiment of a valve positioner for use with a control valve (e.g., the control valve of  FIG. 1 ); 
           [0011]      FIG. 4  depicts a schematic diagram of an exemplary embodiment of a valve positioner for use with a control valve (e.g., the control valve of  FIG. 1 ); 
           [0012]      FIG. 5  depicts a schematic diagram of an exemplary embodiment of a valve positioner for use with a control valve (e.g., the control valve of  FIG. 1 ) 
           [0013]      FIG. 6  depicts the valve positioner of  FIG. 5  with an example of a manifold element in a position that corresponds to a by-pass mode of operation; and 
           [0014]      FIG. 7  depicts the valve positioner of  FIG. 6  with an example of a processing component separated from the valve positioner. 
       
    
    
       [0015]    Where applicable like reference characters designate identical or corresponding components and units throughout the several views, which are not to scale unless otherwise indicated. 
       DETAILED DESCRIPTION 
       [0016]      FIGS. 1 and 2  illustrate an exemplary embodiment of a valve positioner  100  with by-pass features that continue to modulate fluid flow during on-line maintenance and repair. In  FIG. 1 , the valve positioner  100  is part of a control valve  102  with a fluid coupling  104  and an actuator  106 . These components of the control valve  102  work in combination with the valve positioner  100  to control one or more process conditions (e.g., flow, pressure, temperature, etc.) that relate to fluid flow through the fluid coupling  104 . As shown in the diagram, the fluid coupling  104  has a body  108  with a first inlet/outlet  110  and a second inlet/outlet  112 . The fluid coupling  104  can also have a valve, which is not shown in the diagram of  FIG. 1 . The valve resides in the body  108 . The actuator  106  couples with the valve to change the position of the valve (e.g., from a first valve position to a second valve position). The change in position modulates fluid flow across the first inlet/outlet  110  and the second inlet/outlet  112 . In one implementation, the valve positioner  100  couples with the actuator  106  to cause the actuator  106  to change the valve position in response to one or more input control signals the valve positioner  100  receives from a remote device (e.g., a central process control module and/or sensors that monitor changes in the process conditions upstream and downstream of the control valve  102 ). 
         [0017]      FIG. 2  depicts the valve positioner  100  in exploded form. As shown in this diagram, the valve positioner  100  has a plurality of valve components (e.g., a converter component  114 , a relay component  116 , a processing component  118 ). The valve components  114 ,  116 ,  118  work in combination to maintain the position of the valve that modulates fluid flow across the control valve  102  ( FIG. 1 ). The valve positioner  100  also includes a by-pass component, identified by the numeral  120 . Examples of the by-pass component  120  form an analog circuit and/or device that forgoes use of digital components. This design offers robust performance and high reliability relative to components and construction, e.g., of the processing component  118 . For example, as discussed more below, the by-pass component  120  is compatible with the various protocols for the input control signals in use to operate the control valve  102  ( FIG. 1 ) in process control systems. 
         [0018]    Broadly, the by-pass component  120  couples with the processing component  118  and with the remote device. This configuration couples the by-pass component  120  with the input control signal that instructs the correct position of valve in the control valve  102  ( FIG. 1 ). Examples of the by-pass component  120  can operate in one or more operating modes that defines how the input control signal conducts to the valve components in response to component failure. For example, during normal operating conditions (i.e., no component failures), the by-pass component  120  operates in a first mode. In this first mode, the by-pass component  120  conducts the input control signal, or a derivation thereof, from the processing component  118  to the other valve components (e.g., the converter component  114 ). This configuration manages operation of the valve components to achieve the appropriate modulation of fluid flow across the control valve  102  ( FIG. 1 ). 
         [0019]    If a failure occurs, i.e., if the processing component  118  fails and/or other operating deviations of the control valve  102  ( FIG. 1 ) are detected, the by-pass component  120  can operate in a second mode that permits the by-pass component  120  to conduct the input control signal, or a derivation thereof, directly to the valve components. To this end, the input control signal effectively by-passes the processing component  118 . This configuration maintains operation of control valve  102  ( FIG. 1 ) to modulate the flow of fluid, but without the processing and functionality of the processing component  118 . 
         [0020]    Examples of the by-pass component  120  can maintain the functionality of the control valve  102  ( FIG. 1 ) to modulate fluid flow during on-line maintenance and repair. Operating the by-pass component  120  in the second mode, for example, effectively decouples the processing component  118  from operation of the valve components. This feature permits an end user (e.g., a technician) to remove, replace, and/or repair the processing component  118  and/or other digital components (e.g., sensors) on the control valve  102  ( FIG. 1 ) without disruption to fluid flow and, ultimately, the process system (and process control system) that integrates the control valve  102  ( FIG. 1 ). 
         [0021]    Referring back to  FIG. 2 , the valve positioner  100  has a housing  122  with housing openings  123  and one or more mounting locations (e.g., a first mounting location  124  and a second mounting location  126 ). One or more covers (e.g., a first cover  128  and a second cover  130 ) can secure with the housing  122  at the mounting locations  124 ,  126 . Examples of the covers  128 ,  130  enclose the valve components, thereby protecting the valve components from conditions prevailing in the environment surrounding the control valve  102  ( FIG. 1 ). At the first mounting location  124 , the valve positioner  100  includes an interface component  132  that resides at least partially between the housing  120 . The interface component  132  can include various layers of material (e.g., insulators, mounting plates, etc.). This construction can secure, retain, and/or protect one or both of the converter component  114  and the relay component  116 . In one example, the housing  122  has a compartment  134  that can receive the processing component  118  and/or the by-pass component  120 . The valve positioner  100  also includes one or more gauges (e.g., a first gauge  136  and a second gauge  138 ) that can provide an indication of the flow conditions (e.g., pressure, flow rate, etc.) of fluid, e.g., compressed air, that the valve positioner  100  uses to operate the valve in the control valve  102  ( FIG. 1 ). 
         [0022]    In one embodiment, the converter component  114  can comprise a current-to-pressure (I/P) converter. This device converts an analog signal to a proportional linear pneumatic output. The pneumatic output corresponds to a pressure value, which in turn can control pneumatic actuators/operators and pneumatic valves. As shown in the example of  FIG. 2 , the relay component  116  can receive the pneumatic output. Examples of the relay component  116  include switching devices and, in one particular example, pneumatic relays that change position in response to the pneumatic output, e.g., open and close in response to compressed air. In one example, the position of the relay component  116  can regulate the position of the valve. This feature modulates the flow of fluid through the control valve  102  ( FIG. 1 ). 
         [0023]    The processing component  118  manages operation of the control valve  102  ( FIG. 1 ). Examples of the processing component  118  can comprise one or more discrete components (e.g., resistors, transistors, capacitors, etc.) that reside on one or more substrates (e.g., a printed circuit board). These components may include a processor (e.g., an ASIC, FPGA, etc.) that can execute executable instructions in the form of software and firmware. These executable instructions can be stored on memory. In one embodiment, the processing component  118  can include one or more programmable switches, inputs that couple with sensors for position feedback, a proportional-integral-derivative (PID) controller, a display (e.g., an LCD display), and like components that facilitate use and operation of the control valve  102  ( FIG. 1 ). 
         [0024]      FIG. 3  depicts a schematic diagram of a valve positioner  200  to further describe operation among the various operating modes of the by-pass component  220 . In the example of  FIG. 3 , the valve positioner  200  couples with a remote device  240  that provides a control input signal  242 . Examples of the control input signal  242  conform to a variety of protocols, e.g., 4-20 mA, 10-50 mA, Fieldbus, and Modbus®. The valve positioner  200  also couples with valve elements  244 , which modulate the fluid flow through the control valve  202 . In one example, the valve elements  244  couple with the relay component  216  and with the processing component  218 . A first feedback loop  246  can generate a first feedback signal  248  to the processing component  218  that contains data about the operation condition of the valve  244  and/or the control valve  202  in general. 
         [0025]    As also shown in  FIG. 3 , the by-pass component  220  includes a signal conditioning component  250  and a signal switching component  252  with one or more inputs (e.g., a first input  254  and a second input  256 ) and one or more outputs (e.g., a first output  258 ). The signal switching component  252  can operate among a plurality of operating states (e.g., a first operating state  260  and a second operating state  262 ). In one embodiment, the valve positioner  200  includes a second feedback loop  264  that communicates a second feedback signal  266  between the converter component  214  and the switching component  252 . The valve positioner  200  also includes an operating loop  268  that communicates an operating signal  270  between the processing component  218  and the switching component  252 . 
         [0026]    Examples of the operating states  260 ,  262  of the signal switching component  252  correspond with the operating modes which, as discussed above, determine how the input control signal  242  conducts, e.g., to the converter component  214 . The first operating state  260  places the by-pass component  220  in the first operating mode, thereby conducting the input power signal  242  from the processing component  218  to the converter component  214 . On the other hand, the second operating state  262  places the by-pass component  220  in the second operating mode, which conducts the input power signal  242  from the signal conditioning component  250  to the converter component  214 . 
         [0027]    The operating signal  270  from the processing component  218  can cause the signal switching component  252  to change between the operating states  260 ,  262 . Examples of the operating signal  270  can have one or more assigned parameters (e.g., voltage, current, etc.). These assigned parameters can change, e.g., in response to failure of the processing component  218  and/or changes in operation of the control valve  202 . For example, the voltage and/or current of the operating signal  270  can change from a high level to a low level, and vice versa. The high level may correspond to the first operating state  260  and, accordingly, operation of the by-pass component  220  in the first mode to conduct the input power signal from the processing component  218 . In another example, the low level may indicate failure and/or errors in operation of the control valve  202 . In response to the low level, the signal switching component  252  may enter the second operating state  262 , which causes the by-pass component  220  to operate in the second mode to conduct the input power signal from the signal conditioning component  250  to the converter component  214 . 
         [0028]    The first feedback signal  248  can, in one embodiment, dictate the level of the operating signal  270 . Examples of the first feedback signal  248  can arise from one or more sensors that reside in and/around the valve  244  and throughout the control valve  202 . These sensors can track the position and/or travel of the valve  244 , flow properties (e.g., velocity, rate, pressure, etc.), and other parameters that define operation of the control valve  202 . The first feedback signal  248  can contain data that defines one or more values for these parameters. In one example, the processing component  218  can compare these values to a threshold criteria to detect problems in operation. If the values do not satisfy the threshold criteria, then the processing component  218  can cause the level of the operating signal  270 , which, in turn, modifies the operating state  260 ,  262  of the signal switching component  252 . 
         [0029]    As shown in  FIG. 3 , the remote device  240  can deliver the input control signal  242  to one or both of the processing component  218  and the signal conditioning component  250 . Examples of the signal conditioning component  250  can modify properties of the input control signal  242  to comport with construction of the signal switching component  252 . As mentioned above, this construction may require the input control signal  242  to utilize analog, rather than digital, parameters. To this end, and in one example, configurations of the signal conditioning component  250  may modify signals that use the Fieldbus and Modbus® protocols into one or more signals with corresponding analog parameters that are compatible with operation, e.g., of the converter component  214 . 
         [0030]      FIG. 4  illustrates a schematic diagram of an exemplary embodiment of a valve positioner  200 . In the example of  FIG. 4 , the signal switching component  352  includes an operational amplifier  372  and an output range component  374 . Examples of the output range component  374  can include step-up and step-down circuitry with conventional topology to adjust the output of the signal switching component  352 . These types of circuitry, in combination with the operational amplifier  372 , can scale the output of the signal switching component  352  to match the operating range (e.g., the pneumatic range) of the valve  344 . This feature provides adequate control over the mechanical range of the valve  344  in the event that the processing component  318  fails and, accordingly, feedback signals (e.g., the first feedback signal  348 ) are no longer available to monitor the position of the valve  344  as desired. Examples of the operational amplifier  372  can receive the input control signal, e.g., at the first input  354  and the second input  356 , and a power input (e.g., operating signal  370 ) from the processing component  318 . 
         [0031]      FIGS. 5 ,  6 , and  7  illustrate one implementation of the by-pass features that allow for on-line maintenance and repair to occur without the need to take the valve-under-maintenance offline.  FIG. 5  illustrates a schematic diagram of an exemplary embodiment of a valve positioner  400  that is part of a valve  402 , shown in a normal operating state. The diagram in  FIG. 6  provides an example of the valve  402  in a by-pass condition that utilizes the by-pass component  420  to continue to conduct control signals between the converter component  414  and the remote device  450 . This feature preserves operation of the valve  402  to modulate flow of a working fluid. As shown in  FIG. 7 , configurations of the valve positioner  400  also allow the processor  418  to separate from the housing  422 , e.g., as might happen during maintenance to swap and/or replace the processor  418 . 
         [0032]    In  FIG. 5 , the valve positioner  400  includes a manifold element  476  with one or more openings  478  and corresponding gasket elements  480  disposed on either side of the manifold element  476 . The manifold element  476  may incorporate a signal connection element that includes a top-side connector  482  found on the top side (also “first side”) of the manifold element  476  and a bottom-side connector  483  found on the bottom side (also “second side”) of the manifold element  476 . The signal connection element can couple with the converter component  414  via cable  484  that extends from the bottom-side connector  483 . In one embodiment, the valve positioner  400  also has a relay assembly with a relay component  486 , and connectors (e.g., a first connector  487  and a second connector  488 ). A cable  490  can couple with the second connector  488  and with connectors on the by-pass component  420 . The valve positioner  400  can also include a bypass switch element  492  and a manifold position sensor  494 , which in one example includes a magnet  495  and a hall effect sensor  496 . 
         [0033]    Construction of the valve positioner  400  permits the manifold element  476  to move relative to the processing component  418  and/or the housing component  422 . This construction may incorporate slides, rollers, bearings, and like elements that afford low friction coupling, e.g., of the manifold element  476  with one or more parts of the housing element  422 . Examples of the gasket elements  480  include o-rings and like devices that can create a seal between the surfaces of the manifold element  476  and housing element and/or the processing component  418 . Formation of this seal may prevent fluid from migrating from the manifold openings  478 , while reducing the number of points of contact with the manifold element  476  that might restrict and/or prevent movement. 
         [0034]    This configuration of components can allow the manifold element  478  to change position, e.g., from a first position (shown in  FIG. 5 ) to a second position that is different from the first position. The different positions regulate flow of fluid (e.g., air) between the processing component  418  and one or more of the converter component  414 , the relay component  416 , and a regulator  498 . In one implementation, when the valve  402  operates in the normal operating state, the manifold element  478  can assume the first position to allow fluid to flow from the housing openings  423  to the processing component  418  via openings  478 . In this first position, the signal connection element on the manifold element  476  couples with the relay element  486 . This connection allows signals to conduct from the remote device  440  to the converter component  414  via the processing component  418 . In one example, these signals travel along a signal path that includes the relay element  486 , the signal connection element on the manifold element  476 , and the cable  484 . 
         [0035]    Use of the by-pass switch element  492  can initiate and/or facilitate the change in position of the manifold element  476 . Examples of the by-pass switch element  492  may include one or more switches (e.g., toggle, push button, etc.) and other devices that can cause the manifold element  476  to move, e.g., between the first position and the second position. In one implementation, these devices actuate in response to physical contact to affect motion of the manifold element  476 . This feature of the element  492  may require the presence of a technician to initiate the by-pass condition and provide maintenance, as contemplated herein. However, this disclosure also contemplates other configurations of elements and components that would allow automated actuation of the by-pass switch element  492 , e.g., in response to signals that originate remote from the valve  402 . These configuration might respond, for example, to signals from the remote device  440  that cause the by-pass switch element  492  to change the position of the manifold element  476  between the first position and the second position. 
         [0036]      FIG. 6  illustrates an example of a second position for the manifold element  476 . In this example, the change in position of the manifold element  476  misaligns the manifold openings  423  and the openings  478 . This configuration prevents the flow of fluid, e.g., between the processing component  418  and components  414 ,  416 ,  498 . The change in position of the manifold element  476  also decouples the signals connection element on the manifold element  476  from the relay element  486 . In one example, the signal connection element on the manifold element  478  couples with the by-pass component  420  via connection  499  in the second position. Examples of the connection  499  allow signals to conduct from the by-pass component  420  to the converter component  414  without passing through the processing component  418 . This feature preserves operation of the valve  402 , while placing the valve positioner  400  in condition to allow the processing component  418  to separate, e.g. from the housing element  422 . 
         [0037]      FIG. 7  illustrates one exemplary configuration for the valve positioner  400  to show the separation of the processing component  418  from the housing element  422 . This separation may occur during maintenance to repair and/or replace the processing component  418 . In one implementation, a technician can actuate the by-pass switch element  492  to change the position of the manifold element  476  from the first position to the second position. This step places the valve positioner  400  in the by-pass condition, which permits the valve  402  to continue to operate, e.g., to modulate the flow of fluid in response to signals from the remote device  440 . During the remaining maintenance procedure, the technician may decouple the cable  490  from the processing component  418 . The technician may then grasp the processing component  418  and, in one example, apply sufficient force on the processing component  418  to extract the processing component  418  from the housing element  422 . In one procedure, the technician may replace the processing component  418  in the housing  422 , reconnect the cable  490 , and replace and/or reconnect any other miscellaneous components as necessary. The technician may then actuate the by-pass switch element  492  to re-position the manifold element  476  in the first position to re-initiate normal operation of the valve positioner  400 . During re-initiation, the valve positioner  400  may pole the manifold positioner sensor  494  to ensure that the manifold element  476  returns to the first position. 
         [0038]    In light of the foregoing discussion, examples of the by-pass component expand the functionality of control valves to continue operation during maintenance and repair. This feature allows the control valve to remain on-line and, more importantly, to continue to modulate fluid flow as necessary to maintain process conditions as though the control valve is operating normally. Moreover, designs for the by-pass component proposed herein offer process operators an option to realize the benefits (e.g., expanded processing power, data collection and feedback, etc.) of valve positioners and control valves, while addressing potential reliability that might otherwise result in downtime and loss of process productivity in devices that do not utilize the by-pass component therein. 
         [0039]    As used herein, an element or function recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural said elements or functions, unless such exclusion is explicitly recited. Furthermore, references to “one embodiment” of the claimed invention should not be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. 
         [0040]    This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to 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 include equivalent structural elements with insubstantial differences from the literal language of the claims.