While creating an automated spreadsheet to perform sub-cooled PSV sizing,I noticed that per API 520, equation D.9 can be used for all cases highlighted in section D.2.2 (multi-component systems with nominal boiling range less than 150°F or single-component systems far from the critical point...
I have been working on finding steam flow across an orifice, as this flow will dictate the relief requirements for a relief valve down stream of the orifice. Therefore, I decided to create my own excel calculator to be very detailed, so that future engineers can see how I arrived at my numbers...