Normally open and normally closed valves
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I would like to ask everyone: on the devices you have used, which valves are designed to be in an always-open or always-closed state? It means the device remains either on or off throughout its operation.
The valve at the root of the safety valve, the valve at the root of the pressure gauge, the pump inlet valve, and the circulating water valve are normally open; the pressure relief valve is normally closed
The valve at the root of the safety valve, the valve at the root of the pressure gauge, the pump inlet valve, and the circulating water valve are normally open; the pressure relief valve is normally closed
Devices for draining, drain pipes, spare interface valves, bypasses for flow meters and control valves, emergency water intake points, valves at steam interfaces, shut-off valves for emergency discharge, and so on, are usually kept closed.
Under normal conditions, it must be either on or off in order to function properly; therefore, either the on or off mode should be selected. In emergency situations, it is necessary to maintain an open, closed, or immediate state in order to ensure safety; therefore, it is essential to choose between a normally open, normally closed, or latching type
What the people above mentioned are the valves that should (need to) be opened or closed under normal operating conditions, and this is understandable. In fact, in automated control systems, there are valves that can be either normally open or normally closed (in pneumatic valves, these are referred to as air-open or air-close). I’m not sure if that’s what the questioner is referring to.
Thank you all for your advice! It perfectly solved my problem: lol