3 replies to this topic

Dear everybody

I'm a process engineer, my boss assigns me to study about the flare system for using in new plant construction then I read the API RP521 in Flare Sizing Topic as a guildline, first I've the suspicion about the wording of Low Pressure Flare and High Pressure Flare.
For the flare sizing, RP521 said that the mach number that recommend for low pressure flare is 0.2 and the sonic velocity may be appropriate for high pressure flare.
From above I would like to know that what criteria to classify the low and high pressure flare.

Could you please suggest me about this issue.

Thank you in advance for your hosptality.

[jprocess]

Dear,
A lot of aspects should to be considered to segregate relieving streams to flare network. The critical concern is cost. Sometimes you may have three levels: LP, MP and HP.
In one of my previous projects we had a LP flare network for sources with pressures less than 10 barg and HP flare for pressures more than 20 barg.
Other important points are presence of toxic species and water and low temperature studies.

[mishra.anand72@gmail.com]

Pressure is the criteria for classifying LP and HP flare line. Below 0.2, LP and above 0.2 HP. May be below 0.2, you don't get sufficient drive to reach standardised flare tip height.

[eilpar]

One way is to look at the set pressure of PSVs in the flare network. If there is a large variation in the set points it may be economical to segregate into HP and LP lines and allow more pressure drop (without exceeding mach number) in HP lines. This will result in smaller size lines and save cost. But a detailed study will be required.