How much do you know about pneumatic valve positio

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Pneumatic valve is a valve driven by compressed air. When purchasing pneumatic valves, only specifying the specification, category and working pressure can meet the purchasing requirements. It can be used to control the flow of various types of fluids such as air, water, steam, various corrosive media, mud, oil, liquid metal and radioactive media. It is imperfect in the current market economy environment

do you know the pneumatic valve positioner? Pneumatic valve positioner is one of the important accessories and accessories of pneumatic control valve. Play the role of valve positioning. The pneumatic valve positioner and pneumatic actuator together constitute the automatic control unit and various regulating valves. After debugging and installation, they are combined into pneumatic regulating valves. It is used in various industrial automation process control fields. The following editor will introduce the relevant knowledge about pneumatic valve positioner. Let's go and find out

working principle of pneumatic valve positioner

pneumatic valve positioner works according to the principle of torque balance. When the signal pressure P1 connected to bellows 2 increases, the main lever 3 rotates around the fulcrum to make the nozzle baffle 9 close to the nozzle. After the nozzle back pressure is amplified by one-way amplifier 8, the pressure connected to the membrane chamber of the actuator increases and the valve rod moves downward. And drive the feedback rod to rotate around the fulcrum, and the feedback cam will also rotate counterclockwise. The auxiliary lever 4 will rotate around the fulcrum through the roller, and the feedback spring will be stretched. When the tension of the spring on the main lever 3 and the signal pressure on the bellows reach the torque balance, the instrument will reach the balance state. The valve position of the actuator is maintained at a certain opening, and a certain signal pressure corresponds to a certain valve position opening. The above action mode is positive action. If you want to change the action mode, just turn the cam over and turn the a direction into the B direction, etc. The so-called positive action positioner means that when the signal pressure increases, the output pressure also increases; The so-called reaction positioner means that the signal pressure increases and the output pressure decreases. As long as a positive action actuator is equipped with a reaction positioner, the action of the reaction actuator can be realized; On the contrary, as long as a reaction actuator is equipped with a reaction positioner, the action of the positive action actuator can be realized

structural principle of pneumatic valve positioner

pneumatic valve positioner receives weak current signals such as 4 ~ 20mA from the controller or control system, and sends air signals to the pneumatic actuator to control the valve position

it is used together with pneumatic control valve to form a closed-loop control circuit. The DC current signal given by the control system is converted into the gas signal driving the regulating valve to control the action of the regulating valve. At the same time, the feedback is carried out according to the opening of the regulating valve, so that the valve position can be correctly positioned according to the control signal output by the system

characteristics of pneumatic valve positioner

pneumatic valve positioner has many characteristics. Its structure is equipped with a large-diameter pilot type repeater, which can well prevent the air path from blocking, so that the action of the regulating valve will be accelerated. This positioner is relatively sensitive, so it can use the changes of working conditions well, adjust in time, and continue to work stably. If you need to change the working mode during the working process, you don't need to change the parts, just adjust the specific installation position of the relay in the positioner

the requirements of this valve positioner for its partner, namely pneumatic control valve, are not very high, and it can be used within various pressure ranges. The pneumatic valve positioner can be controlled separately. The range of positioner signal is not all, but only a part of the whole control signal. Therefore, if there is a control signal, it can well control multiple positioners

pneumatic valve positioner is an important component, so it will be used in many places. If you want to buy it, you must pay attention to the following aspects: whether the positioner can realize split range, whether it can be easily adjusted for zero and range, how stable the first two are, and how accurate it can be, etc

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