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SAMSON valve positioner working principle and debugging steps

Views: 36     Author: Site Editor     Publish Time: 2022-05-25      Origin: Site

SAMSON valve positioner working principle

The valve positioner is the main accessory of the control valve. It takes the valve stem displacement signal as the input feedback measurement signal, and uses the controller output signal as the setting signal for comparison. When there is a deviation between the two, the output to the actuator is changed. The signal makes the actuator act, and the one-to-one correspondence between the displacement of the valve stem and the output signal of the controller is established. Therefore, the valve positioner constitutes a feedback control system with the stem displacement as the measurement signal and the controller output as the set signal. The manipulated variable of the control system is the output signal of the valve positioner to the actuator.

(1) It is used for important adjustment systems that require high adjustment quality to improve the positioning and reliability of the adjustment valve.

(2) It is used in the occasions where the pressure difference between the two ends of the valve is large (△p>1MPa). By increasing the air source pressure, the output force of the actuator is increased to overcome the unbalanced force generated by the liquid on the valve core and reduce the stroke error.

(3) When the medium to be adjusted is high temperature, high pressure, low temperature, toxic, flammable and explosive, insmart positioner for control valve price - Hiltech order to prevent external leakage, the packing is often pressed very tightly, so the friction between the valve stem and the packing is large. Time lag can be overcome with a locator.

(4) When the medium to be adjusted is a viscous fluid or contains suspended solids, the positioner can overcome the resistance of the medium to the movement of the valve stem.

(5) It is used for regulating valve with large diameter (Dg>100mm) to increase the output thrust of the actuator.

(6) When the distance between the regulator and the actuator is more than 60m, the positioner can overcome the transmission delay of the control signal and improve the response speed of the valve.

(7) Used to improve the flow characteristics of the regulating valve.

(8) When one regulator controls two actuators to implement split-range control, two positioners can be used to accept low input signals and high input signals respectively, then one actuator operates at low range and the other moves at high level, which constitutes a split. program adjustment.

Debugging steps of SAMSON valve positioner:

1. Knob button

Rotate the knob button to select the parameter code (P0 to P16), then press this button to confirm the selected parameter code. To change the parameter value, turn the Knob button to select the desired value, and then press the Knob button to confirm the selected value.

1. Tips

When the display returns to status indication mode, the changed parameter values are first saved in EEPROM (in case of power failure). Turn the knob to code P0, or wait 3 minutes

2. Pay attention

The positioner needs to be re-initialized after parameter codes P2, P3, P4 and P8 are changed. Air restrictor Q Q air restrictor is used to adjust the air delivery to suit the size of the actuator. There are two different settings that can be selected according to the way of the actuator gas circuit.

2. The air volume limiter is used to adapt the size of the actuator when supplying air.

The transmission time of the actuator is less than 1s, such as a linear actuator with an effective diaphragm area less than 240cm2, it is necessary to limit the air flow (MIN). Actuator transit time ≥ 1s, no need to limit air flow (MAX) The position of the air volume limiter also depends on how the signal pressure acts on the SAMSON actuator: "SIDE" (side) position applies when the actuator is connected to the signal pressure on the side , such as 3271-5. The "BACK" position is for when the actuator is connected to the signal pressure at the back, such as 3277-5 "SIDE"

Also applies to non-SAMSON actuators.

1. Display

The LC display indicates setting codes and function symbols. The bar graph shows the control deviation by a (+/-) sign and a numerical value, and one bar of the bar graph represents 1% of the control deviation. If the positioner is not initialized, the bar graph does not indicate the control deviation, but the deflection angle of the feedback lever relative to the valve stem/shaft. One division of the bar graph corresponds to a deflection angle of approximately 5°. If the error symbol appears on the display, turn the rotary button until ERR appears, and view error codes E0 to E15. See Section 5.6 for details.

2. Startup Warning When the device is running, do not start the system. When the air supply and electrical signals are applied, the control valve may move over the full range of travel or angle of rotation, depending on the setting parameters.

Connect the air supply (SUPPLY 9) to the input control signal 4 to 20 mA, (terminals 11 and 12). In most cases, if the locator is installed correctly, the default settings will be used. Once the output air limit and fail-safe position are set, the positioner can be initialized.

3. Tips

The positioner is able to monitor the working range. If the feedback lever is too close to the mechanical limit (which may cause mechanical damage), the positioner will bleed air from the actuator and the control valve will move to the fail-safe position ( S will be reset with an error code.

4. Zero calibration

If the closed position of the valve is inconsistent, as in the case of a soft-sealed spool, a zero calibration is required. Activating code P16 starts zero calibration: turn the button until code P16 appears. Press the button for 6 seconds to count down to 6-5-4-3-2-1 on the display. Initialization has started and the display is flashing! The positioner moves the control valve to the closed position and recalibrates the electrical zero point. When zero calibration is complete, the positioner returns to closed loop operation (status indication). Cancelling the zero point calibration The zero point calibration can be canceled by pressing the button. The positioner will move to the fail-safe position (shown as S S). The zero point calibration can be restarted afterwards. After initialization, the positioner is in closed loop operation.

5. Reset

A reset causes the initialization process to be canceled and all parameter settings to return to their default settings (see Section 6). When the P0 status indication mode is selected: Press the button for 6 seconds, the countdown to 6-5-4-3-2-1 is performed on the display, and ESC appears on the display. Rotate the button and RST appears on the display. Press the button to reset its default settings.

6. Manual operation mode

The control valve can be moved using manual operation: turn the button until code P14 appears. Press the button for 6 seconds to count down to 6-5-4-3-2-1 on the display. – The manual setpoint (wman) is shown on the positioner display after initialization is complete.

Displays the angle of the position of the feedback lever with respect to the axis of the valve stem on the display of an uninitialized positioner. Rotate button. Initialized positioner: The setpoint can be manually adjusted by adjusting the positioner to move the control valve within its range in steps of 0.1%. Positioner without initialization: By adjusting the manual set point, the control valve will only move in one direction.

For more details of SAMSON valve positioner products, please pay attention to: SAMSON positioner.