3 replies to this topic

[Wiseguy007]

Hi All,

I wonder if anyone can help me with this. I am looking to calculate the required rate of fuel gas purge used in a cold vent header open to atmoshere. So far the only information i have come across is relating to flare stacks (API 521). Can the formulas be applied to fuel gas purge of cold vents?

If not can you link to me any literature with formulas specifically used for calculating the puge rate of cold vent headers?

Thanks,

[Bobby Strain]

My first job more than 40 years ago was in an ethylene unit with cold vents. We never used purge. But the vents had a vent head with a steam ring.

Bobby

[Wiseguy007]

It is a vent system with several process lines feeding into it; these then lead to the vent knock-out drum with open vent open to atmosphere.
Purge gas is taken directly from the production header and used for continuous purge.

Is there a minimum requirement for purge rates in any of the API standards?

Does anyone have any ideas on how to proceed with this calculation?

Edited by Wiseguy007, 01 December 2012 - 05:10 AM.

[Neelakantan]

hi
i was looking at this thread and expected some senior guys to comment/advice the OP.

my questions and thoughts are:
1) is it existing one or are you designing new one?
2) who suggested FG purging for a cold vent?
3) know the difference between the functionality of a cold vent and a flare ( Hint: cold vent is for intermittent instant relief! and not for continuous flow)
4) purging of cold vent is done with non-combustible (N2) to prevent air
5) always remember cold vent is a possible source of fire; that is why API talks of radiation assuming a fireball incident and dispersion using DEGADIS or some such software; and check NFPA 211.
6) Finally look at your operator company; what is their hse recommendations regarding cold vent. are they willing to cover insurance for cold vents?

regards
neelakantan