The open/closed issue of pneumatic valves?
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There is a problem with the pneumatic valve. There is a pneumatically operated ball valve on site, and fluid is leaking from the packing gland. Due to excessive tightening, the valve gets stuck halfway when tried to be opened manually. After loosening the tightening screws slightly, when the control system tried to operate the valve, it was found that when the control system activated the valve, it actually closed on site, while when the control system deactivated it, the valve opened on site. When the pneumatic supply to the valve was cut off, the control valve remained in the open position. This pneumatic valve changed from being a pneumatically operated valve to functioning in the opposite manner – what is going on here? How to adjust? Urgent! Thank you, there is no problem with the circuit of the pneumatic valve
After reading the description, it seems that the valve has changed from a gas-open type to a gas-close type. Check the direction-of-action setting in the parameter settings; if it is set to positive action, try changing it to negative action, and if it is already set to negative action, then change it to positive action.
A gas-on valve cannot turn itself into a gas-off valve, mainly because the positions of the spring and diaphragm remain unchanged.
This post was last edited by Happy King on 2017-8-19 at 14:59. Try reversing the 4 to 20mA output from DCS; otherwise, it will be necessary to make adjustments on the locator.
Just rotate the installation angle of the actuator and the valve by 90°.
Yes, but the usual approach is to disassemble the valve and turn the valve core 90 degrees
It depends on whether the valve is a pneumatic control ball valve or a pneumatic on/off ball valve; the type of failure of the valve cannot change without human intervention. Therefore, to address such issues, it is necessary to consider the configuration of the upstream unit for this valve; for control valves, one needs to look at whether the AO output signal has a positive or negative effect, while for on/off valves, it is necessary to consider the valve state corresponding to the energized or de-energized state of the output solenoid valve DO signal.
Is the position signal of the valve reversed? In fact, should the opening and closing of the valve be in sync with that in the control room?