Process Engineering Division – Instrumentation and Automation Section – Daily Question – Question dated 2020-08-16
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Process Engineering Division – Instrumentation and Automation Section – Daily Question – Question from 2020-08-16: Discussion question: 206. How can the air-operated mode of a pneumatic control valve be changed from air-open to air-close?
1. Change the air-open valve to an air-close valve: (The valve core structure of the control valve must have the capability to be changed; not every type of valve core can be modified.) (1) Direct-acting pneumatic diaphragm control valve: a. Replace the normally open air valve with an air-close valve by installing the valve core in reverse; in other words, change the shape from an equilateral triangle (the shape of the valve core being △) to an inverted triangle ▽. Then fix it with rivets. To replace a normally closed air valve with a normally open one, simply reverse the approach. b. Replace the reaction air valve with an air-shut valve, and install the valve core in the reverse direction; in other words, change the inverted triangle shape (the valve core having a ▽ shape) to an upright triangle shape △. Then fix it with rivets. To change a reverse-acting air shut-off valve to an air-on valve, just use the opposite approach. (2) Angle-controlled control valve: a. Single-acting type: Taking a ball valve as an example, after disconnecting the actuator, rotating the valve core by 90 degrees and reconnecting it (that is, manually moving it from the closed position to the open position before reconnecting it to the actuator) enables switching between air-open and air-close operation. The same is true in reverse. b. Double-acting: There is no such thing as air-open or air-close.
By changing the positive and negative actions of the actuator of the control valve, as well as the normal and reverse installation of the control valve and the feedback cam of the valve positioner, it is possible to change the air-operated or air-shut mode of the control valve
By changing the positive and negative actions of the actuator of the control valve, as well as the normal and reverse installation of the control valve and the feedback cam of the valve positioner, it is possible to change the air-operated or air-shut mode of the control valve
By changing the positive and negative actions of the actuator of the control valve, as well as the normal and reverse installation of the control valve and the feedback cam of the valve positioner, it is possible to change the air-operated or air-shut mode of the control valve
By changing the positive and negative actions of the actuator of the control valve, as well as the normal and reverse installation of the control valve and the feedback cam of the valve positioner, it is possible to change the air-operated or air-shut mode of the control valve
By changing the positive and negative actions of the actuator of the control valve, as well as the normal and reverse installation of the control valve and the feedback cam of the valve positioner, it is possible to change the air-operated or air-shut mode of the control valve
By changing the positive and negative actions of the actuator of the control valve, as well as by adjusting the normal and reverse installation of the control valve and the feedback cam of the valve positioner, it is possible to change the air-operated or air-shut type of the control valve.
By changing the positive and negative actions of the actuator of the control valve, as well as the normal and reverse installation of the control valve and the feedback cam of the valve positioner, it is possible to change the air-operated or air-shut mode of the control valve
1. Change the air-open valve to an air-close valve: (The valve core structure of the control valve must have the capability to be changed; not every type of valve core can be modified.) (1) Direct-acting pneumatic diaphragm control valve: a. Replace the normally open air valve with an air-close valve by installing the valve core in reverse; in other words, change the shape from an equilateral triangle (the shape of the valve core being △) to an inverted triangle ▽. Then fix it with rivets. To replace a normally closed air valve with a normally open one, simply reverse the approach. b. Replace the reaction air valve with an air-shut valve, and install the valve core in the reverse direction; in other words, change the inverted triangle shape (the valve core having a ▽ shape) to an upright triangle shape △. Then fix it with rivets. To change a reverse-acting air shut-off valve to an air-on valve, just use the opposite approach. (2) Angle-controlled control valve: a. Single-acting type: Taking a ball valve as an example, after disconnecting the actuator, rotating the valve core by 90 degrees and reconnecting it (that is, manually moving it from the closed position to the open position before reconnecting it to the actuator) enables switching between air-open and air-close operation. The same is true in reverse. b. Double-acting: There is no such thing as air-open or air-close.
By changing the positive and negative reactions of the control valve actuator； The normal and reverse installation of the control valve, along with the use of the valve positioner’s feedback cam, can be used to change the valve’s operation mode from air-open to air-close.