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[ayan_dg]

Flare header is sweeped by fuel gas in order to keep them at slightly higher pressure so that air ingress does not occur.
I have two cases for the first case is normal sweeping based on a velocity of 0.03 m/s in main flare header which requires a total flow of 180 Sm3/h and the other case is contraction of vapour inside flare header during a rain storm in this case the sweeping rate is 600 Sm3/h.
The problem is how I design the system based on this two flowrates. Should I make an oversize system which provides a sweeping flow of 600 Sm3/h always or should I put manual globe valve set in such a way that it gives 180 Sm3/h with a bypass having a PCV which will open sensing vacuum in flare header and sized for (600-180) Sm3/h.

[fallah]

ayan_dg,

IMO, second option, i.e. using a by pass having a PCV, is better solution than the first in process and economical standpoints. With such a high additional flowrate of sweep gas during sudden condensation it might the pilot operated pressure regulator be more proper than simple one in order to cope with probable stability concern.

Fallah