Open circuit diagnosis for pulse solenoid I / P

Abstract

Techniques for diagnosing faults in a digital solenoid I / P converter are provided herein. A controller of the I / P converter can apply a fixed voltage to an I / P coil of the I / P converter, thereby causing an armature to move from a closed position to an open position in a functioning I / P converter. The controller can receive an indication of whether a digital logic line transition has occurred, which indicates that a current of the I / P coil has reached a desired maximum current level. The controller can remove the fixed voltage applied to the I / P coil when the maximum current level is reached or when a threshold period of time has elapsed from applying the fixed voltage to the I / P coil. The controller can diagnose a fault in the I / P converter based on whether the digital logic line transition occurred before the fixed voltage is removed.

Description

Technical Field

[0001] This disclosure generally relates to converters, and more specifically to electro-pneumatic converters and related methods. Background Technology

[0002] Control valves (e.g., slide valves, rotary valves, axial flow valves, ball valves, etc.) are commonly used in industrial processes, such as oil and gas pipeline distribution systems and chemical processing plants, to control the flow of process fluids. These control valves are automated using pressure-operated actuators controlled by remotely operated field instruments. The field instruments communicate with a process control computer to command changes in fluid flow within the valve, thereby achieving the desired control strategy via the pressure-operated actuator. Electro-pneumatic (I / P) converters (e.g., current-to-pressure transducers) are typically used in the field instruments to provide the conversion of electrical signals to volumetric flow rate or pressure output (i.e., pneumatic pressure signals) to control the actuators, thereby controlling the valves.

[0003] Exemplary electro-pneumatic converters (e.g., those discussed in U.S. Patent No. 10,422,438 B2, the entire contents of which are incorporated herein by reference) can be fluidly coupled between a supply pressure source supplying pressurized fluid and a downstream device (e.g., a pneumatic relay) that uses the pressurized fluid to control process control equipment (e.g., actuators). The exemplary electro-pneumatic converter can control the flow of pressurized fluid between the supply pressure source and the downstream device. Specifically, the exemplary electro-pneumatic converter can operate between a closed state (sometimes referred to as closed or unlocked) and an open state (sometimes referred to as open or latched). In the closed state, no pressurized fluid is supplied to the downstream device. In the open state, an electrical signal in the form of current is applied to the electro-pneumatic converter, which allows the flow of pressurized fluid to the downstream device and thus converts the electrical input signal into a pneumatic pressure signal.

[0004] An electro-pneumatic converter utilizes a solenoid with a coil and a movable armature to control the flow of pressurized fluid between a supply port and one or more output ports. In some examples, the electro-pneumatic converter includes an axial passage between the supply port and a discharge port. One or more output ports are fluidly coupled to the axial passage and may be coupled to a downstream device (e.g., a pneumatic relay). The supply port receives pressurized fluid from a pressure supply source. The armature is positioned in the axial passage and is movable between a first position and a second position, the first position blocking pressurized fluid flow through the axial passage between the supply port and one or more output ports, and the second position allowing pressurized fluid flow through the axial passage between the supply port and one or more output ports. When the solenoid is activated, the armature moves from the first position to the second position to allow pressurized fluid flow to one or more output ports. In the first position, when the supply port is blocked, the discharge port is unblocked, and one or more output ports are fluidly coupled to the discharge port (e.g., vented to the atmosphere). In the second position, when the supply port is open, the armature blocks the discharge port, thereby allowing pressurized fluid to flow from the supply port to one or more output ports. The solenoid can be activated and deactivated to move the armature back and forth in the channel between a first position and a second position, thereby controlling the flow of pressurized fluid to one or more output ports. This geometry allows the armature to travel a relatively small distance between a first (closed) position and a second (open) position.

[0005] Specifically, digital solenoid I / P converters typically include an armature that is initially spring-biased to the closed position when no voltage is applied. To actuate the armature, a fixed voltage is applied until a desired maximum current level is reached. Once the maximum current level is reached, a reduced voltage is applied to hold the armature in the pulled-in position (i.e., the on position). When the voltage is removed (or, in some examples, when a small negative voltage is applied), the spring force returns the armature to the closed position.

[0006] The goal is to detect open circuits in digital solenoid I / P systems using as few system resources as possible. Summary of the Invention

[0007] In one aspect, a method is provided for diagnosing faults in a digital solenoid I / P converter in a process control system, wherein the digital solenoid I / P converter includes an I / P coil and a drive circuit, and wherein the solenoid I / P converter, when actuated, moves an armature from a closed position to an open position, the method comprising: establishing that a fixed voltage has been applied to the I / P coil at a first time; establishing that the fixed voltage has been removed from the I / P coil at a second time; receiving an indication of a current level associated with the I / P coil from a current sensor; performing a first comparison between the indication of the current level associated with the I / P coil and a desired maximum current level; based on the first comparison, causing a digital logic line to switch when the current level associated with the I / P coil reaches the desired maximum current level; performing a second comparison to determine whether the digital logic line switched before the second time; and based on the second comparison, determining whether the I / P coil and the drive circuit are functioning correctly or whether one or more of the I / P coil or the drive circuit have failed.

[0008] On the other hand, a system for diagnosing faults in a digital solenoid I / P converter in a process control system, the system comprising: a digital solenoid I / P converter including an I / P coil and a drive circuit, the digital solenoid I / P converter being configured to move the armature from a Gambi position to an open position when actuated; and a controller configured to apply a fixed voltage to the I / P coil at a first time and remove the fixed voltage applied to the I / P coil at a second time when the first of the following occurs: (i) the I / P coil reaches a desired maximum current level; (ii) a certain period of time has elapsed since the first time. A threshold time period; a current sensor configured to sense the amount of current associated with the I / P coil; and a diagnostic circuit configured to: perform a first comparison between the sensed amount of current associated with the I / P coil and a desired maximum current level; based on the first comparison, cause a digital logic line to switch when the sensed amount of current associated with the I / P coil reaches the desired maximum current level; perform a second comparison to determine whether the digital logic line has switched after the first time period; and based on the second comparison, determine whether the I / P coil and the drive circuit are functioning correctly or whether one or more of the I / P coil or the drive circuit has failed. Attached Figure Description

[0009] Figure 1 It is a cross-sectional view of an exemplary electric-pneumatic converter having an exemplary armature in the first (closed) position.

[0010] Figure 2 yes Figure 1 A cross-sectional view of an exemplary electric-pneumatic converter, wherein the exemplary armature is in the second (open) position.

[0011] Figure 3It shows the use of Figure 1 An exemplary graph showing the input current applied and the output pressure obtained by an exemplary electric-pneumatic converter.

[0012] Figure 4 Includes several exemplary figures illustrating the applied voltage, generated current, and logic line trip over time for an exemplary normally functioning electric-pneumatic converter.

[0013] Figure 5 Includes several exemplary figures illustrating the applied voltage, the generated current, and the logic line transitions over time for an exemplary electro-pneumatic converter with an open circuit in the coil or drive circuit.

[0014] Figure 6 Examples are given for diagnosis. Figure 1 An exemplary diagnostic circuit for possible malfunctions of an exemplary electric-pneumatic converter.

[0015] Figure 7 This indicates that diagnostics can be implemented by a controller and / or diagnostic computing device. Figure 1 A flowchart illustrating an exemplary method for addressing potential failures of an exemplary electric-pneumatic converter. Detailed Implementation

[0016] As described above, a digital solenoid I / P converter typically includes an armature that is initially spring-biased to the closed position when no voltage is applied. To actuate the armature, a fixed voltage is applied until a desired maximum current level is reached. Once the maximum current level is reached, a reduced voltage is applied to hold the armature in the pulled-in position (i.e., the on position). When the voltage is removed (or, in some examples, when a small negative voltage is applied), the spring force returns the armature to the closed position.

[0017] This disclosure provides a technique for detecting open circuits in a digital solenoid I / P using minimal resources. Using this technique, the digital logic line will switch or toggle when the desired maximum current has been reached and reset upon sending an I / P armature "unlock" command. When an open circuit exists in the I / P converter coil or drive circuitry, the digital logic line will not toggle before the voltage is removed. Therefore, using this technique, open circuits in the I / P converter coil and / or drive circuitry can be detected with minimal resources based on a single state change on the digital logic line (i.e., whether the digital logic line switches before the voltage is removed). In other words, in a properly functioning I / P converter, the digital logic line will change state when the maximum current is reached, while in an I / P converter with an open circuit in the coil or drive circuitry, the digital logic line never toggles because no current is ever generated. In some examples, this technique includes generating an alarm or alert if the digital logic line has not toggleed when the voltage is removed. Advantageously, this technology minimizes system resources by eliminating the need for diagnostics such as timers and capture registers, compared to a normally functioning I / P converter with an open circuit in the coil or drive circuit.

[0018] Now turn to the attached diagram. Figure 1 This is a cross-sectional view of an exemplary electro-pneumatic (I / P) converter 100 (referred to herein as converter 100) constructed according to one or more principles of this disclosure. The exemplary converter 100 converts an electrical input signal into a pneumatic output signal (e.g., a pressure signal) by controlling the flow of pressurized fluid through the converter 100. In some examples, the pneumatic output signal is used to control a device (e.g., a pneumatic actuator for actuating a valve). In some examples, the pneumatic output signal is amplified to a higher pressure and / or volumetric flow rate via a pneumatic relay and then supplied to the actuator to actuate the valve.

[0019] The converter 100 includes a body 102 defining an axial channel 104 extending between a first opening 105 and a second opening 107. The first opening 105 is defined by a supply port 106 to be fluidly coupled to a supply pressure source (e.g., plant air, process gas, etc.). Two output ports 108 are fluidly coupled to the channel 104. The converter 100 operates to block or allow fluid flow between the supply port 106 and the output ports 108. The output ports 108 can be fluidly coupled to a downstream device that receives pressurized fluid, which is considered a pneumatic output signal.

[0020] To control the flow of fluid between the supply port 106 and the output port 108, an exemplary converter 100 includes a solenoid 110 having a coil 112 and a movable armature 114 (e.g., a plug or plunger). The armature 114 is disposed in and movable within a channel 104 between a first opening 105 and a second opening 107. The armature 114 has a first side 116 (e.g., a top side) facing the supply port 106 and a second side 118 (e.g., a bottom side) facing the solenoid 110. The armature 114 can be in a first position (e.g., ... Figure 1 As shown, this position can be referred to as the closed position, the locked position, or the unlocked position, and the second position (such as...). Figure 2 As shown, this position (which may be referred to as an open position, locked position, or open position) moves between two positions. In a first position, armature 114 prevents pressurized fluid from flowing through channel 104 between supply port 106 and output port 108. In a second position, armature 114 allows pressurized fluid to flow through channel 104 between supply port 106 and output port 108, as disclosed in further detail herein. Controller 120 is electrically coupled to coil 112 via drive circuit 121. Controller 120 can activate solenoid 110 by applying current to coil 112 via drive circuit 121, as disclosed in further detail herein.

[0021] The solenoid 110 includes a core 122 and a sleeve 124, with a coil 112 wound around the core 122. The core 122 and the coil 112 are disposed within the sleeve 124. The core 122 has a first side 126 (e.g., a top side) and a second side 128 (e.g., a bottom side) forming the opposite side of the solenoid 110. The solenoid 110 is disposed in a channel 104, near a second opening 107. The solenoid 110 is disposed in a section of the channel 104 having a larger diameter than a section of the channel 104 near the first opening 105. In some examples, the solenoid 110 is press-fitted into the channel 104 through the second opening 107. A seal 130 is disposed between the solenoid 110 and the inner wall 131 of the channel 104. The seal 130 forms a fluid-tight interface between the solenoid 110 and the body 102, and thus prevents fluid flow around the solenoid 110. A first side 133 of the sleeve 124 (e.g., the top side of the solenoid 110) engages with a wall 132 (e.g., a step) of the body 102, which separates the smaller and larger sections of the channel 104. In other examples, the first side 133 of the sleeve 124 may be separable from the wall 132. For example, the solenoid 110 may be formed with a ridge or lip that engages with a corresponding lip formed on the inner wall 131 of the channel (e.g., near the second opening 107), which may be advantageous during manufacturing and / or assembly. The core 122 of the solenoid 110 includes a discharge channel 134 between a first opening 136 (e.g., a discharge port) in a first side 126 of the core 122 and a second opening 138 in a second side 128 of the core 122, as disclosed in further detail herein.

[0022] A stroke stop 140 is disposed in the channel 104, near the supply port 106. The stroke stop 140 has a stroke stop channel 142 between a first opening 144 and a second opening 146. A seal 148 is disposed between the stroke stop 140 and the inner wall 131 of the channel 104 to prevent leakage caused by the stroke stop 140. Therefore, the flow of pressurized fluid into the channel 104 is controlled by the stroke stop channel 142. As discussed further in detail herein, the stroke stop 140 can be adjusted to different positions in the channel 104 to regulate the flow rate when the converter 100 is open or closed. In some examples, the stroke stop 140 is held in the channel 104 by an interference fit. In other examples, the stroke stop 140 can be screwed into the channel 104 by threads. In this example, the stroke stop 140 can be rotated in one direction or the other to adjust its position in the channel 104. Figure 1 As shown, the side of the travel stop 140 facing the armature 114 is conical. However, in other examples, this side of the travel stop 140 may be shaped differently.

[0023] exist Figure 1 In the closed or shut-off position shown, solenoid 110 is not energized, and armature 114 is biased toward supply port 106 via spring 150. Spring 150 is disposed between armature 114 and solenoid 110. The outer portion (e.g., outer circumference) of spring 150 is caught between sleeve 124 (e.g., a notch in the first side 133 of sleeve 124) and wall 132 of body 102. The inner portion (e.g., inner circumference) of spring 150 is coupled to armature 114 at or near the second side 118 of armature 114. The inner portion of spring 150 engages with flange 151 of armature 114 near the second side 118 of armature 114. Spring 150 biases armature 114 toward travel stop 140. Figure 1 In the example shown, spring 150 is a conical tension spring. However, other types of springs can be implemented in other examples. Furthermore, in other examples, spring 150 can be positioned in other locations.

[0024] exist Figure 1 In the closed or shut-off position, armature 114 prevents the flow of fluid from supply port 106. More specifically, armature 114 engages with travel stop 140 and blocks the second opening 146, thereby preventing the flow of fluid through travel stop passage 142. Thus, armature 114 prevents pressurized fluid from flowing through passage 104 between supply port 106 and output port 108. Furthermore, in the closed or shut-off position, armature 114 is spaced apart from the first side 126 of core 122 (e.g., the top side of solenoid 110). In this position, discharge passage 134 fluidly couples passage 104 to the atmosphere. As a result, the flow path is limited between output port 108 and discharge passage 134 (i.e., output port 108 is vented to the atmosphere). Fluid can flow from output port 108, around armature 114 (between armature 114 and inner wall 131 of channel 104), through spring 150, between second side 118 of armature 114 and first side 126 of core 122, and through discharge channel 134 to the atmosphere. Therefore, when converter 100 is in the closed or shut-off position, any positive pressure at output port 108 (and / or fluid lines coupled to output port 108) is released to the atmosphere.

[0025] In order to supply fluid from supply port 106 to output port 108 (e.g., to generate a pneumatic output signal), solenoid 110 can be switched on or activated by applying current to coil 112. Figure 2An exemplary converter 100 is illustrated when the solenoid 110 is activated. The core 122 may be made of an ferrous material (e.g., iron). The current in the coil 112 induces a magnetic field around the core 122. The armature 114, made of a metallic material (e.g., iron), is attracted to the core 122 and moves toward the first side 126 of the core 122. As a result, the armature 114 moves away from the second opening 146 of the travel stop 140, so that pressurized fluid can flow through the channel 104 from the supply port 106 to the output port 108 (as indicated by the arrow). Furthermore, in the open or closed position, the second side 118 of the armature 114 engages with the first side 126 of the core 122. In this position, the armature 114 closes the first opening 136, thereby blocking the discharge channel 134.

[0026] like Figure 1 and Figure 2 As shown, armature 114 can be positioned along axis 152 of channel 104 at a first position blocking supply port 106 ( Figure 1 ) and the second position of blocking the discharge channel 134 ( Figure 2 The supply port 106 and the discharge channel 134 are axially aligned with channel 104. This geometry allows the armature 114 to move a relatively small distance to control the flow of fluid through the converter 100. In particular, the armature 114 is in the first position ( Figure 1 ) and second position ( Figure 2 The armature 114 moves a relatively small distance between the two channels. In some examples, the armature 114 moves approximately 0.002 inches (in) (0.0508 millimeters (mm)). In other examples, the converter 100 may be designed to allow the armature 114 to move more or less within the channel 104.

[0027] like Figure 1 and Figure 2As shown, output port 108 extends from channel 104 in a direction perpendicular to axis 152 of channel 104. In other examples, output port 108 may be oriented at different angles relative to axis 152. Converter 100 includes two output ports 108 disposed on opposite sides of channel 104. In other words, output ports 108 extend from channel 104 in opposite directions. In some examples, by providing two opposing output flow paths, fluid flowing through stroke stop 140 and through armature 114 acts symmetrically on a first side 116 (e.g., top side) of armature 114. In other words, the forces exerted by the fluid flow on the first side 116 of armature 114 are balanced. Otherwise, if only one output port is used, the fluid may bias armature 114 to one side of channel 104, which could cause armature 114 to become misaligned over time. In other examples, converter 100 may include more (e.g., three, four, etc.) or fewer (e.g., one) output ports, and the output ports may be located in other positions and / or oriented in other directions. Figure 1 and Figure 2 In this example, the first side 116 of the armature 114 is relatively flat or planar. As a result, if the armature 114 moves laterally within the channel 104 (towards the inner wall 131), the first side 116 of the armature 114 can still block the second opening 146 of the travel stop 144 when the armature 114 moves back to the first position. In other examples, the first side 116 of the armature can be shaped differently.

[0028] The flow rate of converter 100 can be changed by adjusting the position of travel stop 140 in channel 104. For example, if travel stop 140 moves further into channel 104 toward solenoid 110, the flow rate will be higher when armature 114 moves to the second position ( Figure 2 When the travel stop 140 moves away from the solenoid 110 in the channel 104, the space generated between the travel stop 140 and the armature 114 is less. As a result, the flow rate decreases. On the other hand, if the travel stop 140 moves away from the solenoid 110 in the channel 104, when the armature 114 moves to the second position ( Figure 2 When the stroke stop 140 is engaged, more space is created between the stroke stop 140 and the armature 114. As a result, the flow rate increases. Therefore, the exemplary converter 100 can be easily calibrated to achieve the desired flow rate (e.g., which may correspond to a pneumatic output signal) by adjusting the position of the stroke stop 140.

[0029] Once the desired pressure is reached at output port 108, controller 120 can deactivate solenoid 110 by stopping the current applied to coil 112, which allows armature 114 to move (e.g., via spring 150) back to the first position. Figure 1This prevents fluid flow to output port 108. Furthermore, discharge channel 134 is opened. As a result, any pressure at output port 108 is discharged to the atmosphere through discharge channel 134. In some examples, controller 120 may apply a reverse current to coil 112, which generates an electromagnetic field in the opposite direction that repels or pushes armature 114 toward travel stop 140. Converter 100 can be activated and deactivated relatively quickly (e.g., via pulses of current) to generate a small pneumatic output signal (e.g., a pulse of air) at output port 108.

[0030] In the closed or closed position ( Figure 1 The armature 114 essentially prevents the flow of pressurized fluid into the channel 104. In some cases, only a relatively small amount of fluid leaks into the channel 104. In some examples, the converter 100 achieves an air consumption of less than 0.1 cubic feet per hour (SCFH) at 20 pounds per square inch (PSI).

[0031] The converter 100 includes a seal 154 (e.g., an O-ring) disposed around the body 102 near the output port 108. The seal 154 can be used to fluidly seal the converter 100 in a hole or channel of the controller.

[0032] In some examples, controller 120 initially applies a higher current to coil 112 to move armature 114 to a second position. Figure 2 Then the current is reduced to a lower current. Once the armature 114 moves closer to the core 122, less magnetic force is needed to hold the armature 114 in the second position. Therefore, less current is needed to generate a magnetic field sufficient to hold the armature 114 in the proper position. Therefore, once the armature 114 moves to the second position, the controller 120 reduces the current, thereby reducing the total power consumed by the converter 100.

[0033] Figure 3 An exemplary diagram 300 is illustrated, showing the applied current (top diagram) and corresponding pneumatic output (bottom diagram) generated by the exemplary converter 100. As shown, when the converter 100 is turned on, the controller 120 applies a higher current to the coil 112 to move the armature 114 toward the solenoid 110, thereby overcoming the bias of the spring 150. Once the armature 114 moves to the second position ( Figure 2The flow path between supply port 106 and output port 108 is opened, generating a stable pneumatic output pressure. The applied current can then be reduced. As described above, once armature 114 approaches core 122, the attraction between core 122 and armature 114 becomes stronger, thus allowing a lower magnetic field to hold armature 114 in place. In some examples, a higher current is applied only for a short period until armature 114 is located at or near core 122, at which point the current can be reduced. By reducing the current, less energy is used to operate the exemplary converter 100. In particular, the output pressure remains constant even as the current decreases. Therefore, the exemplary converter 100 is more energy-efficient than known converters that apply the same high current throughout activation. In some examples, the high current signal is approximately 3 mA, while the low current signal is approximately 1 mA. The current can then be stopped, causing converter 100 to close and stop generating pneumatic output pressure. Thus, converter 100 operates between three power states (off, high current, and low current) to produce two pneumatic output states (on or off).

[0034] like Figure 2 As shown, when armature 114 is in the second position, the second side 118 of armature 114 engages with the first side 126 of the core. In this position, a pressure difference is formed that biases armature 114 toward solenoid 110 (into the second position). Specifically, the pressure of the fluid in channel 104 acts on the first side 116 (e.g., the top side) and the lateral side of armature 114, thereby forcing armature 114 toward solenoid 110, and the pressure (e.g., atmospheric pressure) in discharge channel 134 acts on a relatively small area on the second side 118 (e.g., the bottom side) of armature 114, thereby forcing armature 114 in the opposite direction. In some cases, if spring 150 does not generate sufficient reaction force on armature 114 to overcome the pressure of the fluid in channel 104 acting on armature 114, armature 114 may remain in the second position even after solenoid 110 is deactivated. In other words, when solenoid 110 is deactivated and armature 104 is in the second position ( Figure 2 When the pressure difference is greater than the combined force of the spring 150 and the pressure in the discharge channel 134 acting on the first side 116 and the lateral side of the armature 104, the armature 114 can be held in the second position by resisting the bias of the spring 150. Therefore, in some examples, a pressure relief mode can be used to allow the higher-pressure air in the channel 104 to act on the second side 118 of the armature 114, so that the pressure acting on all sides of the armature 114 is approximately balanced. This allows the use of a relatively small and lighter spring 150.

[0035] Figure 4 Exemplary figures 402, 404, and 406 are illustrated, illustrating the applied voltage (402), the generated current (404), and the logic line switching (406) over time for an exemplary normally functioning I / P converter. For example, figures 402 and 404 illustrate an exemplary normally functioning I / P converter, as shown in figure 402, where a fixed voltage is applied until a desired maximum current level is reached, as shown in figure 404. The current drop shown in figure 404 is caused by the movement of the armature as its state changes from the off position to the on position. Then, once the maximum desired current level is reached, the digital logic line switches (as shown in figure 406) and applies a reduced voltage, as shown in figure 402, to hold the armature in the on position. Figure 4 In the example shown, controller 120 can determine that the I / P converter is functioning correctly based on the fact that the logic line jumps before the fixed voltage is removed.

[0036] Figure 5 Exemplary figures 502, 504, and 506 are illustrated, illustrating the time-varying applied voltage (502), the time-varying generated current (504), and the time-varying logic line transition (506) for an exemplary I / P converter with an open circuit in the coil or drive circuit. For example, figure 502 illustrates that for an exemplary I / P converter with an open circuit in the coil or drive circuit, the fixed voltage never decreases to a lower voltage because, as shown in figure 504, the desired maximum current level is never reached. In other words, no current is generated due to the open circuit in the coil or drive circuit. Therefore, as shown in figure 506, the logic line never transitions. Figure 5 In the example shown, controller 120 can determine that the I / P converter has an open circuit in the coil or drive circuit based on the fact that the logic line cannot jump before the fixed voltage is removed.

[0037] Figure 6 Examples are given for diagnosis. Figure 1 An exemplary logic circuit 600 for a possible failure of an exemplary electric-pneumatic converter. In some examples, the logic shown in circuit 600 may be implemented by a processor of controller 120, for example, as a control module, while in other examples, the logic shown in circuit 600 may be implemented by hardware circuit elements of I / P converter 100.

[0038] The logic circuit 600 can receive the sensed current level (I / P coil 112) of the I / P coil 112 from the current sensor 602 associated with the I / P coil 112. 感测The first comparator (C1) 604 of the logic circuit 600 can compare the sensed current with the expected maximum current level (I) of the I / P coil 112. max The comparison can be made, and the digital logic line 606 can be switched based on the sensed current reaching the desired maximum current level.

[0039] Logic circuit 600 can determine a fixed voltage (V) 施加 The fixed voltage is determined to have been applied to the I / P coil 112 at a first time and removed from the I / P coil at a second time. For example, in some examples, when the logic circuit 600 is implemented by the processor of the controller 120, the logic circuit can determine that the fixed voltage has been applied to or removed from the I / P coil 112 at a first time based on the controller 120 causing the fixed voltage to be applied to or removed from the I / P coil 112 at a first time (e.g., via drive circuitry). In other examples, when the logic circuit 600 is implemented by the hardware circuitry elements of the I / P converter 100, the logic circuit 600 can determine that the fixed voltage has been applied to or removed from the I / P coil at a first time based on receiving an indication from a voltage sensor (not shown) associated with the I / P coil 112 indicating that the fixed voltage has been applied to or removed from the I / P coil 112.

[0040] The second comparator (C2) 608 of the logic circuit 600 compares the application / removal of a fixed voltage with any digital logic line transition to determine whether the I / P coil 112 and / or drive circuit 121 are functioning correctly. For example, if the digital logic line transitions before the fixed voltage is removed, the I / P coil 112 and drive circuit 121 are functioning correctly, while if the digital logic line does not transition before the fixed voltage is removed, the I / P coil 112 and / or drive circuit 121 may not be functioning correctly. Furthermore, if the I / P coil 112 and / or drive circuit 121 are not functioning correctly, the second comparator 608 can diagnose possible causes of the fault (diagnostic results), such as an open circuit in the I / P coil 112 or drive circuit 121.

[0041] In an example where logic circuitry 600 is not implemented as part of controller 120, logic circuitry 600 may send diagnostic results to controller 120. In an example where logic circuitry 600 is implemented as part of controller 120, the controller may receive diagnostic results directly from logic circuitry 600. Controller 120 may then take control actions to change the operation of the process control system based on the diagnostic results. For example, controller 120 may change the control strategy to mitigate the fact that I / P converter 100 is not functioning properly. For example, controller 120 may switch the process control system to a redundant field device based on the fact that I / P converter 100 for a specific field device is not functioning properly. As another example, controller 120 may generate an alarm based on the diagnostic results, or otherwise transmit the diagnostic results to the operator of the process control system.

[0042] Figure 7 This is a flowchart illustrating an exemplary method 700, which can be implemented by the controller 120 for diagnostic purposes. Figure 1 Possible malfunctions of the exemplary electric-pneumatic converter 100.

[0043] At block 702, controller 120 can establish that a fixed voltage has been applied to the I / P coil 112 of I / P converter 100 at a first time (e.g., based on controller 120 applying a fixed voltage to I / P coil 112 via drive circuit 121, and / or based on an indication received from a voltage sensor associated with I / P coil 112 that a fixed voltage has been applied to I / P coil 112). Additionally, controller 120 can establish that the fixed voltage has been removed from I / P coil 112 at a second time (e.g., based on controller 120 removing a fixed voltage from I / P coil 112 via drive circuit 121, and / or based on an indication received from a voltage sensor associated with I / P coil 112 that a fixed voltage has been removed from I / P coil 112).

[0044] At block 704, controller 120 may receive, for example, an indication of a sensed current level associated with I / P coil 112 via a current sensor associated with I / P coil 112. At block 706, controller 120 may perform a first comparison, comparing the sensed current level with a desired maximum current level of I / P coil 112. At block 708, controller 120 may, based on this comparison, cause a digital logic line to switch when the sensed current level reaches the desired maximum current level of I / P coil 112. At block 710, controller 120 may perform a second comparison, comparing whether the digital logic line switches after a first time and / or before a second time.

[0045] At block 712, controller 120 can determine, based on a second comparison, whether the I / P converter 100 is functioning correctly, or whether one or more of the I / P coil 112 or drive circuit 121 has failed. For example, if the digital logic line transitions after a first time and / or before a second time, the I / P converter 100 is functioning correctly. Conversely, if the digital logic line fails to transition after the first time and / or before the second time, the I / P coil 112 or drive circuit 121 may have failed (e.g., there may be an open circuit in the I / P coil 112 or drive circuit 121). At block 714, controller 120 can take control actions to alter the operation of the process control system in which the I / P converter 100 operates, based on the determination that one or more of the I / P coil 112 and / or drive circuit 121 has failed. For example, controller 120 can modify the control strategy to mitigate the fact that the I / P converter 100 is not functioning correctly. For example, controller 120 can switch the process control system to redundant field devices based on the fact that the I / P converter 100 of a specific field device is not functioning properly.

[0046] In addition, in some examples, method 700 may include controller 120 generating an alarm based on determining that one or more of the I / P coils or drive circuits have failed.

[0047] aspect

[0048] Embodiments of the technology described in this disclosure may include any number of the following aspects, individually or in combination:

[0049] 1. A method for diagnosing a fault in a digital solenoid I / P converter in a process control system, wherein the digital solenoid I / P converter includes an I / P coil and a drive circuit, and wherein the digital solenoid I / P converter, when actuated, moves an armature from a closed position to an open position, the method comprising: establishing that a fixed voltage has been applied to the I / P coil at a first time; establishing that the fixed voltage has been removed from the I / P coil at a second time; receiving an indication of a current level associated with the I / P coil from a current sensor; performing a first comparison of the indication of the current level associated with the I / P coil and a desired maximum current level; based on the comparison, causing a digital logic line to switch when the current level associated with the I / P coil reaches the desired maximum current level; performing a second comparison to determine whether the digital logic line switched before the second time; and based on the second comparison, determining whether the I / P coil and the drive circuit are functioning correctly or whether one or more of the I / P coil or the drive circuit have failed.

[0050] 2. According to the method of aspect 1, determining whether the I / P coil and the drive circuit are functioning normally or whether one or more of the I / P coil or the drive circuit have failed further includes: determining that the I / P coil and the drive circuit are functioning normally based on the digital logic line switching before the second time.

[0051] 3. According to the method of aspect 1 or aspect 2, determining whether the I / P coil and the driving circuit are functioning normally or whether one or more of the I / P coil or the driving circuit have failed further includes: determining that one or more of the I / P coil or the driving circuit have failed based on the fact that the digital logic line has not changed before the second time.

[0052] 4. The method according to aspect 3 further includes: determining, based on the fact that the digital logic line has not changed before the second time, that one or more of the I / P coil or the drive circuit has failed due to an open circuit in one or more of the I / P coil or the drive circuit.

[0053] 5. The method according to aspect 3 or aspect 4 further includes: generating an alarm based on determining that one or more of the I / P coils or the drive circuits have failed.

[0054] 6. The method according to any one of aspects 3-5 further includes: based on determining that one or more of the I / P coils or the drive circuits have failed, causing the controller to take a control action that changes the operation of the process control system.

[0055] 7. A system for diagnosing faults in a digital solenoid I / P converter in a process control system, the system comprising: a digital solenoid I / P converter including an I / P coil and drive circuitry, the digital solenoid I / P converter being configured to move an armature from a closed position to an open position when actuated; and a controller configured to apply a fixed voltage to the I / P coil at a first time and remove the fixed voltage applied to the I / P coil at a second time when: (i) the I / P coil reaches the desired maximum current level; or (ii) a threshold time period has elapsed since the first time. A current sensor configured to sense the amount of current associated with the I / P coil; and a diagnostic circuit configured to: perform a first comparison between the sensed amount of current associated with the I / P coil and a maximum desired current level; based on the first comparison, cause a digital logic line to switch when the sensed amount of current associated with the I / P coil reaches the maximum desired current level; perform a second comparison to determine whether the digital logic line has switched after the first time; and based on the second comparison, determine whether the I / P coil and the drive circuit are functioning correctly or whether one or more of the I / P coil or the drive circuit has failed.

[0056] 8. The system according to aspect 7, wherein the diagnostic circuit is configured to determine that the I / P coil and the drive circuit are functioning normally based on the digital logic line switching before the second time.

[0057] 9. The system according to aspect 7 or 8, wherein the diagnostic circuit is configured to determine that one or more of the I / P coil or the drive circuit has failed based on the fact that the digital logic line has not changed before the second time.

[0058] 10. The system according to aspect 9, wherein the diagnostic circuit is configured to determine, based on the fact that the digital logic line has not changed before the second time, that one or more of the I / P coil or the drive circuit has failed due to an open circuit in one or more of the I / P coil or the drive circuit.

[0059] 11. The system according to aspect 9 or aspect 10, wherein the diagnostic circuit is further configured to generate an alarm based on determining that one or more of the I / P coil or the drive circuit has failed.

[0060] 12. A system according to any one of aspects 9-11, wherein the controller is further configured to take control actions to change the operation of the process control system based on determining that one or more of the I / P coils or the drive circuits have failed.

Claims

1. A method for diagnosing faults in digital solenoid I / P converters of field devices in a process control system, wherein, The digital solenoid I / P converter includes an I / P coil and a drive circuit, wherein, when actuated, the digital solenoid I / P converter moves the armature from a closed position to an open position, the method comprising: A fixed voltage is established to be applied to the I / P coil at the first moment; The fixed voltage is removed from the I / P coil at a second time. Receive an indication of the current level associated with the I / P coil from the current sensor; Perform a first comparison between the indication of the current level associated with the I / P coil and the expected maximum current level; Based on the comparison, the digital logic line is made to switch when the current level associated with the I / P coil reaches the desired maximum current level; Perform a second comparison to determine whether the digital logic line transitioned before the second time. Based on the second comparison, it is determined whether the I / P coil and the drive circuit are functioning normally, or whether one or more of the I / P coil or the drive circuit have failed; and Based on the determination that one or more of the I / P coils or the drive circuits have failed, the controller takes a control action to change the operation of the process control system, wherein the control action includes switching from using the field device in the process control system to using redundant field devices in the process control system.

2. The method according to claim 1, wherein, Determining whether the I / P coil and the drive circuit are functioning properly, or whether one or more of the I / P coil or the drive circuit have failed, also includes: Based on the fact that the digital logic line changes before the second time, it is determined that the I / P coil and the drive circuit are functioning normally.

3. The method according to claim 1, wherein, Determining whether the I / P coil and the drive circuit are functioning properly, or whether one or more of the I / P coil or the drive circuit have failed, also includes: Based on the fact that the digital logic line did not change before the second time, it is determined that one or more of the I / P coil or the drive circuit have failed.

4. The method according to claim 3, further comprising: Based on the fact that the digital logic line did not change before the second time, it is determined that one or more of the I / P coil or the drive circuit has failed due to an open circuit in one or more of the I / P coil or the drive circuit.

5. The method according to claim 3, further comprising: An alarm is generated based on the determination that one or more of the I / P coils or the drive circuits have failed.

6. A system for diagnosing faults in digital solenoid I / P converters in process control systems, the system comprising: The digital solenoid I / P converter of the field device of the process control system includes an I / P coil and a drive circuit, and the digital solenoid I / P converter is configured to move the armature from the closed position to the open position when actuated. A controller is configured to apply a fixed voltage to the I / P coil at a first time and remove the fixed voltage applied to the I / P coil at a second time when the first of the following occurs: (i) the I / P coil reaches the desired maximum current level; Or (ii) the threshold time period has elapsed since the first time; A current sensor is configured to sense the amount of current associated with the I / P coil; as well as The diagnostic circuit is configured as follows: Perform a first comparison between the sensed current quantity associated with the I / P coil and the maximum desired current level; Based on the first comparison, the digital logic line is made to switch when the sensed current associated with the I / P coil reaches the maximum desired current level. Perform a second comparison to determine whether the digital logic line has changed after the first time interval; Based on the second comparison, it is determined whether the I / P coil and the drive circuit are functioning normally or whether one or more of the I / P coil or the drive circuit have failed. as well as Based on the determination that one or more of the I / P coils or the drive circuits have failed, the controller takes a control action to change the operation of the process control system, wherein the control action includes switching from using the field device in the process control system to using redundant field devices in the process control system.

7. The system according to claim 6, wherein, The diagnostic circuit is configured to determine that the I / P coil and the drive circuit are functioning correctly based on the digital logic line switching before the second time.

8. The system according to claim 6, wherein, The diagnostic circuit is configured to determine that one or more of the I / P coil or the drive circuit has failed, based on the fact that the digital logic line has not changed before the second time.

9. The system according to claim 8, wherein, The diagnostic circuit is configured to determine, based on the fact that the digital logic line has not changed before the second time, that one or more of the I / P coil or the drive circuit has failed due to an open circuit in one or more of the I / P coil or the drive circuit.

10. The system according to claim 9, wherein, The diagnostic circuit is also configured to generate an alarm based on the determination that one or more of the I / P coils or the drive circuits have failed.

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