Does anyone know if self-acting control valves come in FO and FC versions?
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I would like to ask the experts: Are self-acting control valves of type FO or FC? Thank you
FO: Fault On FC: Fault Off
There’s no such thing as a failure of the air source in a self-acting type, right? But if there’s no upstream pressure, isn’t the pressure reducing valve fully open?
There is no such concept for self-acting types, as there is no air source
The three disconnections in control valve failures refer to the loss of air supply, power supply, and signal. FO=Fail Open, which means the valve remains open in the event of a failure; FC=Fail Close, meaning the valve remains closed in such a situation. By \"failure\" is meant the interruption of air supply – i.e., what happens when the air supply is cut off, and whether the valve is in an open or closed state. The characteristic of a self-acting control valve is that it can perform regulation without the need for an external air source (by utilizing the pressure of the medium itself); therefore, concepts such as FO and FC do not apply to self-acting control valves.
If it is used to regulate the pressure before the valve, similar to FC； If it is used to regulate the pressure after the valve, similar to FO: lol
Self-acting valves with pressure tapping behind the valve generally operate to close (to stabilize the pressure behind the valve), while self-acting valves with pressure tapping in front of the valve generally operate to open (to stabilize the pressure in front of the valve). Self-acting control valves are not classified as FC or FO; the distinction lies only in whether pressure is taken from inside the valve, from outside the valve, or before or after the valve.