Setting of FC and FO control valves, as well as drain valves
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For the control valves of FC, should there be one drain valve or should drain valves be installed both before and after the valve? What about the drain valve for the control valves of FO? Please, experts, give me some advice!
The original poster who discussed this issue on the forum can take a look! Under normal circumstances, an FC is a valve that closes in the event of a fault, that is, it is a gas-actuated valve; when the gas supply fails, the valve closes automatically. It opens only when there is gas available. The air enters from below the diaphragm head, which is why two drain valves need to be installed at the inlet and outlet. Contrary to FO, since the pressure relief valve is open, only one drain valve is required at the front and back; generally, standards specify that a drain valve should be installed at the inlet of the control valve. However, the above design requirements are stipulated by standards; in actual design, if the medium is non-toxic and harmless, generally only one drain valve will be installed on the FC valve!
Generally, there is one discharge valve installed at the control valve assembly, and it is usually placed in front of the control valve.