Dear all,
Please find the quote from API 521 regarding the liquid hold-up in a flare KO drum.
"The volume occupied by the liquid should be based on a release that lasts 20 min to 30 min. Larger hold-up
volume may be required if it takes longer to stop the flow. Any accumulation of liquid retained from a prior release (from pressure-relief devices or other sources) should be added to the liquid indicated in items a) and above to determine the available vapour-disengaging space."
It states that "any accumulation from the previous release should be added". My question is what is the liquid level in the KO drum should be taken from the previous release? Is that pump start level or LZHH? What is the justification for that?
Appreciate your response.
Thanks and regards,
Fakhri