PLEASE NOTE: this posting is about pressure vessel RVs discharing back into the process and not Hydrostatic RVs or pump RVs.
Scenario: Process is shutdown using the emergency stop (e-stop) systems because the building is on fire. On the roof of the building/plant sit a number of vessels that have a “flooded system” which contains a “surge tank” that holds the EHS/HHC for the flooded system. These surge tanks are ASME coded vessels and are protected by pressure relief valves, which discharge back into a “suction line”.
I am hopeful that most can see where I am going with this. Although technically allowed by some groups in some process specific applications, this design is one that should NEVER be considered without some very detailed discussions and understanding of its limitations and here’s why…