Why is Process Simulation Needed? (for EPC Project) When I joined an EPC Company… When I joined an EPC company as a process engineer,  process engineers were busy doing process simulations. I saw a senior process engineer doing a process simulation by using HYSYS or Pro II for the EPC project of oil & gas / petrochemical / refineries. But Heat and Mass Balance(HMB) already existed!! The thing that I couldn't understand was that there had already been HMB given by  a FEED company after being awarded the EPC project. All kinds of the process documents such as PFD, P&ID, HMB, etc., had already existed. The funny thing to me was that the senior engineers were inputting the process conditions (temperature, pressure, pressure drop, flow rate, compositions of feed streams, etc.) by referring to HMB given by FEED, they literally just copied the input data and pasted it into the HYSYS. Then they had almost the same results as the HMB. They had created their own HMB extracted from t

1. According to API RP 520 PART2, isolation valve shall be full bore to minimize built up back pressure. And the flow area of the isolation valve shall be same or bigger than PSV outlet flow area.  There is no requirement that PSV outlet isolation valve size shall be same or bigger than PSV outlet size. Usually PSV discharge isolation valve is located downstream of expander in order to reduce the back pressure but, it is not mandatory by API. <API RP 520 PART2> 2. According to API 521, the sizing criteria for the PSV discharge piping is based on total back pressure. If there is no problem on total back pressure which is lower than PSV's MABP(Maximum Allowable Back Pressure),  there is no need for isolation valve is located downstream of expander in the PSV discharge line.  In case of conventional PSV application,  MABP is 10% of set pressure. API 521  3. In case Fluid is gas phase, it is required to avoid sonic velocity or critical velocity. if fl

1. Open HYSYS V8.6 2. You have to have your simulation file and open it. The fluid package and component might be determined. 2. "VIEW" TAP click 3. "Model Palette" click 4. Palette will pop up. 5. Click " CUSTOM" button 6. Click " Equilibrium Unit Operation" button. Youtube : https://www.youtube.com/channel/UCofwAgaoyd_aVQmZ7OJxHOA