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Working principle of imported pneumatic valve positioner

Pneumatic valve positioner is divided into two types: electric positioner and gas positioner. Let's talk about the gas locator today:
(1) Working principle
The pneumatic valve positioner is one of the important accessories and accessories of the pneumatic control valve, which functions as a valve.
The pneumatic valve positioner works according to the principle of torque balance. When the signal pressure P1 of the bellows 2 is increased, the main lever 3 is rotated around the fulcrum, so that the nozzle baffle 9 is close to the nozzle, and the nozzle back pressure is amplified by the unidirectional amplifier 8. Thereafter, the pressure introduced into the diaphragm chamber of the actuator increases, causing the valve stem to move downward. And driving the feedback rod to rotate around the fulcrum, the feedback cam also rotates counterclockwise, the secondary lever 4 is rotated around the fulcrum by the roller, and the feedback spring is stretched, and the tension and signal pressure of the spring on the main lever 3 are used in the bellows When the upper force reaches the torque balance, the meter reaches equilibrium. The valve position of the actuator is maintained at a certain degree of opening, and a certain signal pressure corresponds to a certain valve position opening. The above action mode is a positive action. If the action mode is to be changed, the cam is turned over and the A direction is changed to the B direction. The so-called positive acting positioner means that the signal pressure increases and the output pressure also increases. The so-called reaction positioner means that the signal pressure increases and the output pressure decreases. A positive acting actuator can implement the action of the reaction actuator as long as the reaction locator is installed; on the contrary, a reaction actuator can implement the action of the positive acting actuator as long as the reaction locator is installed.

(2) Structural principle
The pneumatic valve positioner receives a weak electrical signal from 4 to 20 mA in the controller or control system and sends an air signal to the pneumatic actuator to control the position of the valve.
It is used in conjunction with a pneumatic control valve to form a closed loop control loop. The DC current signal given by the control system is converted into a gas signal that drives the regulating valve to control the action of the regulating valve. At the same time, feedback is made according to the opening degree of the regulating valve, so that the valve position can be correctly positioned according to the control signal outputted by the system.

(3) Main functions
The pneumatic valve positioner and the pneumatic actuator form a self-control unit and various regulating valve connections are assembled and assembled into a pneumatic regulating valve. Used in a variety of industrial automation process control areas.

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