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[MWS777]

Hello,

           We are currently in the process of re-commissioning our liquid nitrogen tank. Our tank is an API 620 APP 'Q'-8th Edition built by CBI in 1997. The tank was allowed to go dry for maintenance issues. We have completed so far, the inner tank purge and are maintaining a 3.4 psig of dry nitrogen gas at approximately -46°F dewpoint @ ambient temperature, (62°F as of this morning). We are trying to get the annulus dry now and are having difficulty achieving the requierd dewpoint (-20°F). We are sending 60°F nitrogen gas to the top odf the tank @ 2.5"/H2O with the relief valve open at the top and four 4" open flanges at the bottom. Is it bett to purgew from the top down or from the bottom up? Annular space is about 45,000 ft³. Thanks for any help. Mike