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We are about to install 2 PSVs on a new vessel designated for hydrogen storage. The vessel is horizontal and is placed on ground level in close proximity of hydrogen production unit. In case of pressure buildup the PSVs will vent excessive pressure to atmosphere. I want to know what should be the optimum/safe height of the PSV vent?
 
Answers
23/03/2010 A: Morgan Rodwell, Fluor Canada Limited, morgan.rodwell@fluor.com
To follow on Mr. Ragsdale's response, a hydrogen vent stack will often autoignite so the possibility of this being an ignition source should also be considered.
19/03/2010 A: Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
Even though hydrogen is lighter than air, in some parts of the world the vent would need to be tied into the relief system to a flare or thermal oxidizer. So, it is difficult to say what the minimum height of an "unlit flare" would be in your case.