What are Smart Valve Positioners?

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Pneumatic actuator is an actuator powered by compressed air. Pneumatic actuators are used in conjunction with electrical converters and valve positioners to continuously receive control commands from DCS and output linear displacement. At this time, the positioner and the actuator form a closed loop, which can overcome the friction force of the valve stem and the unbalanced force of the valve core. This ensures that the position of the regulating valve is accurately positioned in proportion to the current signal output by the DCS. By adjusting the positioner, the flow characteristics and action form of the control valve can also be modified.

If the pneumatic actuator is equipped with accessories such as position retaining valve, solenoid valve, position feedback, limit switch, etc., the three-break self-locking function of the regulating valve can be realized (that is, when the power is cut off, the signal is cut off, and the air source is cut off, the valve keeps the current position unchanged. ), and can also fully open (or fully close) the regulating valve in an emergency.

The composition of the smart valve positioner

The intelligent valve positioner is a digital field device using a highly integrated microprocessor, which is very different from the conventional positioner in structure and working principle. It is small in size and light in weight. The positioner can output inversion signals and limit switch signals. The use of this positioner does not require additional inversion and limit switches. The interior of the positioner is mainly composed of the following components:

⑴ It is a motherboard with a microprocessor and an input circuit. The LCD screen and operation buttons are located on the circuit board, and the circuit board mounting bracket has several slots, which can be inserted into the modules with position feedback and alarm functions according to the numbers.The position feedback module can output a 4~20 mA bit reverse current signal. In the automatic mode, if the execution unit fails to reach the set position (open and close) or fails, it will output an alarm signal and display the fault code on the LCD screen.

Valve Positioner Maintenance and Inspection

1. Regularly check the output pressure of the air filter pressure reducer of the valve positioner. Do not increase or reduce the output pressure of the pressure reducer at will.

2. Regularly drain the air filter pressure reducer to prevent the water vapor in the pressure reducer from entering into the positioner and cause the positioner failure. When draining water, turn the drain screw 2 circles anticlockwise, and then tighten the screw.

3. In normal use, please cover the shell of the positioner to prevent water vapor, dust and other impurities from entering the positioner to cause failure.

Common troubleshooting

No action of preset signal

Check the air supply

Check the signal connection

It acts but cannot be fully opened


Check the air supply pressure.

It can only be fully opened or fully


Check whether the connecting accessories are


Check the output port for leakage

Small volume of the actuator

Positioner oscillation

Check whether the connecting accessories are


Check the output port for leakage

Small volume of the actuator

No feedback signal

Check the feedback signal connection

Check the 24 V power supply of feedback

signal circuit

The LCD displays as Error

Check whether the feedback rod is loose

Check the potentiometer gear for looseness

Potentiometer and gear not aligned or


poor contact of potentiometer wire

Clear constant throttling orifice  


1. Do not adjust the amplifier "balance adjusting screw".

2.The junction box can be uncovered  only after the power is cut off.

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