Abstract: Methods and system for minor loop feedback fallback are disclosed. An example method includes controlling a process control device using first values from a first sensor; comparing the first values to reference values to identify a difference; and in response to the difference being outside of a threshold, controlling the process control device using second values from a second sensor.

Abstract: Methods and apparatus of testing a solenoid valve of an emergency valve via a positioner are disclosed. An example method includes conducting a solenoid valve test by initiating a pulse duration and a monitoring duration for the solenoid valve test. Conducting the solenoid valve test further includes instructing a solenoid valve to transition from a first state to a second state during the pulse duration. The solenoid valve is in fluid communication with an actuator to enable the actuator to actuate an emergency valve. Conducting the solenoid valve test further includes determining a functionality of the solenoid valve by measuring, via a valve positioner, a maximum pressure change of a pressure chamber of the actuator during the monitoring duration. The example method includes, upon determining the solenoid valve is in a functioning state, conducting a partial stroke test of the emergency valve via the valve positioner.

Abstract: Methods and apparatus of assessing a test of a solenoid valve via a positioner are disclosed. An example apparatus includes a solenoid valve to enable an actuator to close an emergency valve and a valve positioner fluidly and communicatively coupled to the solenoid valve. The valve positioner is to instruct the solenoid valve to transition the solenoid valve from a first state to a second state. The valve positioner is to monitor a pressure change of a pressure chamber of the actuator in fluid communication with the solenoid valve relative to an initial pressure for a monitoring duration. The valve positioner is to identify a maximum pressure change during the monitoring duration and determine a ready state of the solenoid valve when the maximum pressure change is greater than a minimum trip value and the pressure change at a monitoring end time is less than a maximum reset value.

Abstract: Methods and apparatus of stabilizing a valve positioner when testing a solenoid valve are disclosed. An example apparatus includes a solenoid valve and a valve positioner fluidly and communicatively coupled to the solenoid valve. The valve positioner is to be set in a pressure control state prior to conducting a test of the solenoid valve. The valve positioner is to detect a pressure change across the solenoid valve caused by the solenoid valve transitioning from a first state to a second state and transition the valve positioner from the pressure control state to a saturated state upon detecting the pressure change. The full supply pressure is to stabilize the valve positioner to conduct the test of the solenoid valve. The valve positioner is to maintain the saturated state until the pressure across the solenoid valve returns to the predetermined initial value.

Abstract: Methods and apparatus of stabilizing a valve positioner when testing a solenoid valve are disclosed. An example apparatus includes a solenoid valve and a valve positioner fluidly and communicatively coupled to the solenoid valve. The valve positioner is to be set in a pressure control state prior to conducting a test of the solenoid valve. The valve positioner is to detect a pressure change across the solenoid valve caused by the solenoid valve transitioning from a first state to a second state and transition the valve positioner from the pressure control state to a saturated state upon detecting the pressure change. The full supply pressure is to stabilize the valve positioner to conduct the test of the solenoid valve. The valve positioner is to maintain the saturated state until the pressure across the solenoid valve returns to the predetermined initial value.

Abstract: Methods and apparatus of assessing a test of a solenoid valve via a positioner are disclosed. An example apparatus includes a solenoid valve to enable an actuator to close an emergency valve and a valve positioner fluidly and communicatively coupled to the solenoid valve. The valve positioner is to instruct the solenoid valve to transition the solenoid valve from a first state to a second state. The valve positioner is to monitor a pressure change of a pressure chamber of the actuator in fluid communication with the solenoid valve relative to an initial pressure for a monitoring duration. The valve positioner is to identify a maximum pressure change during the monitoring duration and determine a ready state of the solenoid valve when the maximum pressure change is greater than a minimum trip value and the pressure change at a monitoring end time is less than a maximum reset value.

Abstract: Methods and apparatus of testing a solenoid valve of an emergency valve via a positioner are disclosed. An example method includes conducting a solenoid valve test by initiating a pulse duration and a monitoring duration for the solenoid valve test. Conducting the solenoid valve test further includes instructing a solenoid valve to transition from a first state to a second state during the pulse duration. The solenoid valve is in fluid communication with an actuator to enable the actuator to actuate an emergency valve. Conducting the solenoid valve test further includes determining a functionality of the solenoid valve by measuring, via a valve positioner, a maximum pressure change of a pressure chamber of the actuator during the monitoring duration. The example method includes, upon determining the solenoid valve is in a functioning state, conducting a partial stroke test of the emergency valve via the valve positioner.

Abstract: Methods and system for minor loop feedback fallback are disclosed. An example apparatus includes a minor loop feedback having a first mode and a second mode. The first mode is to output a first value used to control a process control device in a normal operation. The second mode is to output a second value used to control the process control device during a failure condition. The apparatus includes a controller to transition between the first mode and the second mode based on an identification of the failure condition.

Abstract: Methods and system for minor loop feedback fallback are disclosed. An example method includes controlling a process control device using first values from a first sensor; comparing the first values to reference values to identify a difference; and in response to the difference being outside of a threshold, controlling the process control device using second values from a second sensor.

Abstract: Methods and system for minor loop feedback fallback are disclosed. An example apparatus includes a minor loop feedback having a first mode and a second mode. The first mode is to output a first value used to control a process control device in a normal operation. The second mode is to output a second value used to control the process control device during a failure condition. The apparatus includes a controller to transition between the first mode and the second mode based on an identification of the failure condition.

Abstract: A lead-lag input filter is connected ahead of a positioner feedback loop having one or more valve accessories, such as a volume booster or a QEV, to overcome slow dynamics experienced by the accessories when receiving low amplitude change control or set point signals. A user interface is connected to the lead-lag input filter and enables an operator or other control personnel to view and change the operating characteristics of the lead-lag input filter to thereby provide the control loop with any of a number of desired response characteristics.

Abstract: Systems and methods for urging a valve plug off a seat of a control valve and toward a set point in the absence of significant delay. Adjustable, user-selected input parameters to the input of a lead-lag filter in communication with the input of a control loop facilitates achieving tunable response by a control valve upon application of small amplitude inputs.

Abstract: Methods and apparatus related to feedback control for electro-pneumatic control systems are disclosed. An example electro-pneumatic control system comprises an electro-pneumatic controller and a secondary pneumatic power stage coupled to the electro-pneumatic controller to provide a feedback signal to the electro-pneumatic controller.

Abstract: An asymmetric volume booster assembly includes an actuator movable in a first direction and a second direction, a first booster in fluid communication with the actuator, and a second booster in fluid communication with the actuator. The first booster includes a first supply passage and a first exhaust passage, wherein the first supply passage supplies fluid to the actuator and the first exhaust passage exhausts fluid from the actuator. The first exhaust passage is configured to produce a first fluid flow resistance. The second booster includes a second supply passage and a second exhaust passage, wherein the second supply passage supplies fluid to the actuator and the second exhaust passage exhausts fluid from the actuator. The second exhaust passage is configured to produce a second resistance to fluid flow. The first fluid flow resistance is greater than the second fluid flow resistance, such that the actuator moves substantially symmetrically in the first direction and the second direction.

Abstract: A diagnostic system and method for a field device in a process control apparatus is provided. At least one sensor is associated with the process control apparatus, and a computer is adapted to receive data from the sensor and to detect an occurrence of a predetermined process event. A memory device is operatively connected to the computer and adapted to store sensor data received by the computer at a time corresponding to the occurrence of the predetermined process event.

Abstract: A method and apparatus determines the presence of and source of instabilities, such as limit cycles, within a process control loop while the process control loop operates on-line within a process environment. The method and apparatus measures one or more signals within a process control loop when the process control loop is connected on-line within a process control environment, stores the measured signal as signal data and then performs one or more statistical analyses on the stored signal data to determine whether instabilities exist and, if so, whether the source of an instability is within a servo loop or outside of a servo loop and is due to friction, external forces or mechanical anomalies.