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Depressuring Tutorial

In this posting, we will learn the depressuring simulation study using HYSYS simulator. The simulation is mainly divided into two steps, fire case and adiabatic case. Commonly, the fire case simulation result in the peak flowrate to flare, whereas the adiabatic case simulation is used as basis in determining Minimum Design Metal Temperature (MDMT).

Basic Depressuring - Why 15 minutes ?

In previous posting, we have discussed that PSV wouldn’t provide adequate protection for vessel of fire case. Therefore, depressuring can be applied for another safety layer.

Commonly the plant area is divided into the ESD Zone. Each ESD zone may contain one or more equipments. ESDV or SDV valves are provided in each ESD Zone to isolate the system zone. In case of fire, a system will be isolated by those SDV valves. Then the inventory fluid (commonly gas phase only) in the system will be released to flare through BDV valve. Commonly one BDV is provided for one system zone, but in some cases, it is possible to provide more than one BDVs in one system zone.