How to supply air to a control valve with a solenoid valve?
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While studying the installation diagrams for valves, I noticed that for control valves equipped with solenoid valves, in some cases the air supply is connected to the valve positioner directly, while in other cases it passes through the solenoid valve first before reaching the valve positioner. I’m very confused; please ask someone knowledgeable to help explain it!
Due to different designs, the pneumatic piping varies, and it must be constructed in accordance with the design.
Often, solenoid valves are used in situations where rapid adjustment of control valves is required. For example, when a certain process variable exceeds its limit, it is necessary to cut off the air supply to the valve positioner, so as to cause a rapid loss of air pressure and bring the valve back to a safe state. If there is no solenoid valve, the positioner must be used to adjust the valve slowly, and rapid operation of the valve cannot be achieved. Therefore, the target for supplying air is the valve positioner; the solenoid valve simply acts as a switch for supplying air to the positioner
What the senior on the 3rd floor said makes a lot of sense; the solenoid valve in the valve positioner acts as a pilot valve, enabling rapid ventilation and shutdown of air flow.
I support the view from the 3rd floor; the function of the solenoid valve is to cut off the air supply, which is used for interlocking
The air supply is connected to the valve positioner and is used for normal adjustment on a daily basis； It first passes through the solenoid valve and then into the valve positioner, which is used for emergency shutdown interlocks; in this way, once the solenoid valve is turned off, the gas flow is stopped and the valve quickly reaches the F.O. or F.C. state
Rapid shutdown prevents accidents, of course by first connecting the solenoid valve!
The third floor explained it in great detail; the solenoid valve is used to enable quick opening and closing
If there is an air source for the solenoid valve, it should pass through the solenoid valve first; otherwise, the solenoid valve will not be able to serve its interlock function!
What the original poster seems to be asking is why, for control valves that also have solenoids, some of these solenoids are placed in front of the valve positioner while others are placed behind it. Personally, I don’t think there’s any difference; it’s just a physical distinction. However, it’s better to place the solenoid valve in front of the valve positioner. For interlock purposes, it’s advisable to switch the control circuit to manual mode at the moment of activation.
Everyone is right; I would like to add that solenoid valves are also used to maintain a position in interlock systems!
If there is a solenoid valve, connect it to the positioner first; if not, connect it directly to the positioner. Otherwise, it is a wrong connection.
Floor 3 is supported; the function of the solenoid valve is to cut off the air supply
Does everyone think so? In my opinion, a solenoid valve is something that is connected after the valve positioner! That is, the positioner---solenoid valve---diaphragm head! There’s no reason to connect it in front of the valve positioner, right? Who can talk to me about it?
What the original poster seems to be asking is why, for control valves that also have solenoids, some of these solenoids are placed in front of the valve positioner while others are placed behind it. That’s right, that was indeed what I meant to ask. Sorry for not making it clear! The descriptions for the 12th floor and the 14th floor are clearly different; please explain this in detail, leaders!
The air supply is directed to the solenoid valve, and the operation of the valve is controlled by the opening and closing of the solenoid valve
The control valve equipped with a solenoid valve is supplied with air via the solenoid valve, and the opening and closing of the control valve are controlled by changing the direction of the solenoid valve