Selection between air-open and air-close for pneumatic control valves
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What are the selection principles for air-operated control valves in terms of air-open and air-close operation? Are there any standards?
Principled behavior is mainly determined by the process. The situation of no air needs to be considered. If the gas supply is interrupted, it is necessary to ensure that this valve is in a safe position. A gas-open valve is one that closes automatically when the gas supply is cut off, while a gas-close valve is one that opens automatically when the gas supply is cut off. For things like fuel gas flow control valves, if a problem occurs, it is necessary to ensure that this valve remains closed, and for that purpose a gas-actuated valve is used. Usually, people call them accident shut-off valves and accident opening valves.
It is determined by the production process; for example, steam vents generally use air valves, those locations that need pressure relief during emergencies or shutdowns also use air valves, while others use air switches