What is the purpose of the two safety valves connected to the three-way valve?
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I saw a P&ID showing that a tee valve is connected to the top of the pressure vessel, with two safety valves installed at each end of that tee valve. I’m not sure what the purpose of this is Some colleagues also said that this ensures that at least one safety valve is available. But I think the environments in which these two safety valves are located are similar; if one fails, the other is also likely to fail. Why not simply use two nozzles with two safety valves?
When removing or installing a safety valve, the three-way valve can serve to close off and isolate it. If two ports are opened, valves are also needed for isolation. It’s not quite clear why two safety valves are needed. --There were mistakes in the speech; please feel free to point them out.
The reason for installing two safety valves is to ensure that one of them remains functional.
This is a dual-safe valve; the commonly available domestic models are A38 and A37. There are also quad-type versions that allow for switching use, so that one set can be in use while another is under maintenance without affecting the operation of the equipment