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Hi all,

I am confused about Nitrogen blanketing requirement here on our site.

We have 3, 30year old Ref. Butane Storage Tanks (50x15m) with an integrated vapour recovery unit. These storage vessels have PSV and VSV located on them.

A number of securities are there preventing a potential relief. I am less bothered about the rise in pressure scenario. The main concern that I have here is that the VSVs located on the tanks’ roof would breathe in air should the pressure drop too low.

To safe guard this, they have compressor shut off sequence defined. Furthermore, the unit has a dedicated vaporiser there injecting hot C4 vapors in case the pressure drops too low.

To the best of my knowledge, the refinery hasn’t seen these VSVs operating in last 30 years. Would that justify the reason letting the VSV breathe-in air?

I would like to have N2 blanket there. But same time, I would be worried about cycling the air in the compressor loop and adversely affecting the comp duty.

Any thoughts?