With a separator 30% to 60% liquid full I would NOT add up vapor generation from heat input to wetted area plus vapor expansion. Usual practice is to consider only vapor generation from heat input to wetted area.
As far as I know, either the vapor thermal expansion relief load or the boiling...
Montemayor/monaco8774,
Thanks for your replies. Thanks for the recomendation about thread124-143554 - I had read part of it, but not the last and more interesting posts.
I only wanted to check others opinions and some general criteria, instead of boring you with numbers, levels, operating...
We have a couple of gas/liquid separators. We calculated relief requirements due to fire considering the wetted surface heat absorption rate (API 521 eq. 3).
Were wondering about the possibility that the liquid could completely evaporate. After that, expanding vapour would have to be relieved...
Thanks. I can understand the cost saving... in some plants, instead of this solution (short length of SS downstream cold PSVs), I've seen a different approach: two separate flare systems (flare header, KOD & flare):
- one for 'hot' discharges, made of carbon steel
- one for 'cold' discharges...
EGT01, I've recently read some recommendations indicating that safety valve chatter in liquid service, though less likely, is potentially more serious than in vapor service because of the liquid hammer effect (In Ostrwski's presentation here...
I've seen in a couple of old cryogenic gas processing plants that sometimes stainless steel (or 3.5% Ni steel) is used in PSV discharge lines for a short length (e.g.: 10 to 15 m), before the discharge line ties-in to a carbon steel flare header.
This is applied in PSVs that relieve gases at...
I think that, according to API 521, physical properties for PSV sizing should be evaluated at relief pressure, not at PSV set pressure.
So, I would search for latent heat (and relief temperature) @ 1.21 x 855 psig = 1034 psig (21% overpressure for fire case), which may be well above critical...