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Improve positioning accuracy and reliability of regulating valves
Jun 12, 2018

The positioner is the main accessory of the regulating valve, usually used in conjunction with a pneumatic regulating valve. It accepts the output signal of the regulator and then uses its output signal to control the pneumatic regulating valve. When the regulating valve is actuated, the displacement of the valve stem passes through the mechanical The device feeds back to the positioner and the valve position status is transmitted to the host system via the electrical signal.

The positioner is the main accessory of the control valve. It uses the valve stem displacement signal as the input feedback measurement signal. The controller output signal is used as the setting signal for comparison. When the two are deviated, the output signal to the actuator is changed. The actuator is actuated to establish a one-to-one correspondence between the displacement of the valve stem and the output signal of the controller. Therefore, the positioner consists of a feedback control system that takes the valve stem displacement as a measurement signal and the controller output as a set signal. The manipulated variable of the control system is the output signal from the positioner to the actuator.


(1) An important adjustment system that is required for adjusting the quality to improve the positioning accuracy and reliability of the regulating valve.

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

(3) When the medium to be adjusted is high temperature, high pressure, low temperature, toxic, flammable, and explosive, in order to prevent external leakage, the packing is often pressed tightly, so the friction between the valve stem and the packing is large. Locator can overcome the time lag.

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

(5) For large diameter (Dg> 100mm) regulators to increase the output thrust of the actuator.

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

(7) Used to improve the flow characteristics of the regulator.

(8) When one regulator controls two actuators to perform split-range control, two positioners can be used to respectively accept low input signals and high input signals, and then one actuator performs a low-range action and the other performs an elevation action, which constitutes a point. Process adjustment.


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