Vacuum blanket

[2904]

We are investigating the application of a vacuum blanketing system on API separators and slop oil tanks. We will operate between -1/2" and -1 1/2 w.c. vacuum and will use nitrogen as the blanket gas. We would like to know if anyone has done this or heard of someone doing it in a hydrocarbon application. Our concern is formation of an explosive mixture in the vicinity of a leak in the tank cover.
Thank you.

 

[arsef]

I would recommend using nitrogen to hold tank at 1 to2 inches of water. With a control valve to release pressure at about 8 in. w.c. Also a relief valve to discharge to atmosphere at tank design pressure. A vacuum relief from atmosphere set at minus 2 in. w.c.

If the relief goes to a flare header, then the header will need an inert gas sweep or installation of a device to prevent back flashes in the line.