This ramping up of system force might help protect against undesired opening of the Valve seat mainly because of the momentum of the fluid. The inlet Valve has to be open completely. Double block and bleed (DBB) valves supply a single valve that may simultaneously Minimize off/isolate the downstream http://martinkfyqr.mpeblog.com/11790575/detailed-notes-on-double-block-and-bleed-valve