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[T Rustagi]

Hi Everyone,

 

First of all, I like to thank all the generous wisdom sharers on this wonderful forum. The articles /blog/explanations have been of great help to me. 

 

I am currently facing a situation in which we need to assign a gas group to pumps connected to the drain line of a Flare KOD.  Now, the KOD would be maintained at some minimum level during operation and as per specification it can have HC + H20. Also there is PSV outlet line from a H₂ bullet connected to the KOD.  Hence, it has been assigned Gas Group II C.  The problem arises when we try to assign gas group to the pump at the downstream of the drain of the KOD. 

 

My issue is few people are saying that as there is little chance that H2 can enter the pump hence it should be assigned II C as well.  But I feel as the boiling pt. of H₂ at operating cond. of the vessel is  (-)252.8 deg. C, therefore it will never reach the pump inlet and hence it can be assigned gas group II A / II B.

 

so could anyone explain to me which is the correct philosophy to follow and why.  Also it would be of great help if the following doubts could also be cleared:

 

1. Is it possible for vapors to reach the pump inlet (which is connected to the drain of a KOD)?

2. In case H₂ can reach the pump inlet, is there any way by which we can stop it from reaching that point, or at least reduce the conc. level below 4% (which is the lower explosive limit of H2)?  And if that can occur, then would it reduce the gas group from II C to II B?

 

Hope to hear from someone soon.

 

Thanks,

 

Tanmay