Isolations for Shutdown Valves and Blowdown Valves
I'm working in gas plant, we donot have written philosphy for the isolation of the Shutdown Valves and Blowdown Valves. In our case, at actuation of Level-1 ESD, plant will trip and gas will be blow down through vent stack. In level-2 ESD, only shutdown valves will close and blowdown valves will remain also closed.
Now, problem is some blowdown valves are passing, we can't attend due to non-availability of isolation. Can any body let me know the standard philosphy for the Isolations of Shutdown Valves and Blowdown Valves in gas plants.