3 replies to this topic

[elvisnew]

Dear all,
I have chance to size the relief valve in case of blocked outlet (110% max). I try to use Hysys to size the orifice size of relief valve by using RV equipment in the program in steady state (I didn't use depressurize in utility because this case is not fire case or blowdown case). The results shows orifice size "E" but when I manual calculate by hand (API 520), I found that the correct size is "J". So I have question that
1. Why the result is different?
2. Actually, can RV in Hysys use for relief valve orifice sizing?
3. If Hysys can use for the sizing, it will automaticall change the equation of orifice calculation in case that source is change to Liquid or Gas or Steam? And it will calculate critical point and select the equation for user or not?

However, pls try to see design parameter as attachment.

Best Regards,
elvisnew

Attached Files

•  10-Jul-10 1-20-03 AM.pdf   5.32KB   320 downloads
•  10-Jul-10 1-21-36 AM.pdf   5.54KB   181 downloads
•  10-Jul-10 1-21-51 AM.pdf   6.62KB   197 downloads
•  10-Jul-10 1-22-11 AM.pdf   7.2KB   164 downloads
•  10-Jul-10 1-22-38 AM.pdf   8.72KB   164 downloads

Edited by elvisnew, 09 July 2010 - 01:32 PM.

[joerd]

Please explain how you'll have a PSV set pressure of 17.3 psig and an inlet stream pressure of 230 psig.

[elvisnew]

Joerd,
Thank you Joerd for response and sorry for confusing you. This function of this application is to reduce the inlet pressure from 230 psig to 14.7 psig by pressure control valve (PCV). However to protect downstream (D/S) equipment of PCV (pressure rating = 22 psig) in case of valve malfunction open of this PCV, so relief valve is required to install between D/S of PCV and U/S of equipment. I design to set the set pressure of RV at 17.3 and MAWP (Full open pressure) = 20.3 psig according to API-520. As I told before the orifice size of RV which get from hand calculation and Hysys simulation are different around 3 letter ("E" and "J").

[joerd]

Please check your hand calc, especially for input values. The larger orifice size seems to be the right one.