API 526 table and D orifice

[cam72]

I have following scenario for a safety valve.

MAWP = 240bar g, set pressure = 240 bar g, operating temperature = 50 deg c, relieving temperature = 580 deg c., over pressure = 21% and valve body material is carbon steel. Vendor has calculated and selected 1.5D3 valve with 2500# x 300# rating. Vendor says that 2500# rating is selected based on API 526. Can anybody explain me how to cross check this with API 526 table 3? Why I can not select 1500# valve? Thanks in advance.

 

[DLite30]

If you're overpressure requirement for your relief valve to meet its required capacity is 21% above 240 barg, say 290 barg (which is about 4300 psig), you're well into the 2500# range.


Also, I assume that you made a typo in your relieving temperature of 580 deg C.

 

[MortenA]

Do you have access to API 526? You can e.g. buy it here:

http://global.ihs.com/

However, go to table 2 and have a look. Actually if your temp. is right (a very hot fire case indeed) then you may actually be out of the table even with "exotic" materials. But the vendor may be able to overcome that.

Best regard

Morten