HYSYS simulation (Utility) for pressure relief, calculating BDV and the connected orifice plates
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Everyone, I have some thoughts regarding the calculation of BDV and the orifice plates under fire conditions; I would appreciate your guidance. HYSYS can be used to simulate and calculate the diameter of the orifice plate as well as the peak flow rate. Some people determine the size of orifice plates and BDVs in this way: they provide the simulated peak flow rate and pressure difference to the orifice plate manufacturer, who then calculates the diameter of the orifice plate as well as the size of the pipe. In this way, the size of the BDV matches that of the pipe, and the diameter of the orifice plate is also determined. I calculated using this method, and there was a significant difference between the orifice bore size obtained from HYSYS simulations and the value calculated by Daniel’s company; therefore, I personally think there are some issues with the approach mentioned above. Please tell us how exactly BDV and the size of the subsequent orifice plates should be determined.
Do you have an example of the calculation that you can upload? I'm a beginner.
Can the original poster upload an example?
Is the approach you mentioned really the right one? What do they say? For the peak values and maximum pressure differences that are calculated, you also need to take into account the CV value. After all, there are standards regarding how fast the pressure drops to half its original level, etc. Additionally, each valve manufacturer has its own set of design and calculation procedures, so it’s hard to say that the calculated values will definitely be problem-free. Hehe
I previously used Plus to make a pressure relief valve, but I always felt that there was something wrong with it. Version 8.3 of HYSYS allows for selection and can also generate reports. There is a PDF that explains this; you can take a look.
Where is that PDF file? Could you please upload it and share it? Thank you
ZHEGE TIE ZI BUYAO CHEN A
The confirmation of the BDV diameter followed the requirement of 3% before and 10% after the pressure drop of the safety valve. What confuses me is that the specifications require that the branch pipe connected to the BDV outlet have a flow rate of no more than 0.7 Ma, whereas the BDV outlet itself experiences critical flow at a rate of 1 Ma based on the speed of sound. Does this mean there is a contradiction in the descriptions provided in API521 standards? Or maybe I misunderstood.
I would like to ask you another question regarding the calculation of the outlet pipeline for safety valves. The specifications require that the pressure drop in the outlet pipeline be less than 10% of the set pressure, with the flow velocity in the branch pipes being less than 0.7 m/s and the flow velocity in the main pipe being less than 0.5 m/s. If the gas is compressible and a critical flow (1 Ma) is established at the outlet of the relief valve BDV, then it logically follows that the pipeline downstream of the outlet should also have a flow rate of 1 Ma. How, then, can the requirement specified in the standards of having a flow rate below 0.7 Ma be met (since valves and pipelines are usually considered based on their diameter)? Maybe I misunderstood; please enlighten me