Control valve
Thread Content
There is currently a control valve (air-operated shut-off valve), and the pressure difference before and after the valve is quite high, which prevents it from operating automatically. When set to manual mode, the valve still leaks even when a 100% signal is applied (the positioner is already at 100%). The handwheel was turned to the lowest position to make the valve positioner output 102%, and then the handwheel was turned to the highest position; at this point, the internal leakage of the control valve was eliminated. Could that expert explain what the theoretical basis is for doing this?
Reason: 1. The valve stem is short; turn the stem out a little. 2. Due to the large pressure difference before and after the valve, it is also possible that the actuator does not have sufficient output force; in such cases, an actuator with a greater output force should be used.
Is the valve you have chosen a pneumatic valve? When it is fully closed, the spring stiffness is insufficient, resulting in the valve not closing properly
It’s not a gas-on valve; it’s 100% a gas-off valve.
Adjust the length of the valve stem; it is likely that the stem is too short
Is a valve positioner being used? The output of the valve positioner is insufficient ； Or the pressure difference before and after the control valve is too large, resulting in insufficient travel of the control valve.
I agree with the opinion from the first floor; it’s possible that the spring strength of the actuator is not sufficient. The poster can try increasing the pressure of the instrument air.
1. The valve stem is short; turn it out a little. 2. Due to the large pressure difference before and after the valve, it is also possible that the actuator does not have sufficient output force; in such cases, an actuator with a greater output force should be used. Agree with the view from the second floor; a pneumatic actuator is used, so there is no issue with insufficient spring force