Nitrogen blanket on high sulfur gasoline-external floating roof tank 2

[kirnsi]

Hi, we have a nitrogen blanket on an external floating roof tank with sour gasoline in it. it has to go back to refinery for processing. our maintainence wants to do some work on it and wnat to shut the nitrogen off for about an hour . the main reason we are blanketing this is to avoid formation of gums. would shuting the nitrogen off for a short time hurt the quality of the product in this static tank.

any help will be appreciated,

thank you

 

[JLSeagull]

Instead of the quality of sour gasoline that requires refining - the loss of N2 could affect the explosion hazard. An hour or so does not sound too hazardous.

 

[JimCasey]

OK, I'm stupid.

How do you N2 blanket a tank with a floating roof?

Does not "floating roof" mean that the roof is open above and in direct contact with the gasoline below? Put nitrogen on top of the roof and it is slightly lighter than air so it's gone. Put it below the roof and the bubbles will either blow out around the edge seals, or lift the roof. The N2 leaking from under the floating roof would carry a lot of vapors with it and INCREASE the fire hazard.

'splain to me where my concept has failed. THis is how I learn.

 

[JLSeagull]

Visualize an INTERNAL floating roof on a tank with a cone roof over the floating roof. The floating roof has a vacuum breaker for protection in addition to the pressure-vacuum relief valves on top of the tank. The nitrogen blanket is applied in the vapor space above the floating roof, within the closed tank.

 

[JimCasey]

Thank you, Mr. Seagull. You are, as usual, most erudite. I was thinking inside the box, imagining only the floating roof tanks that have the floating roof exposed to the blue sky above. I probably would have expected the cone-roofed ones to called a "floating barrier" tank or somesuch.

Thanks again,
JC

 

[MJCronin]

To all,

The problem seems to be with the original post, kirnsi states: "we have a nitrogen blanket on an external floating roof tank"... which, I do not think is possible.

The terms "Internal Floating Roof" and "External Floating Roof" tanks are very specific. IFRs can be nitrogen blanketed, EFRs, as I understand, cannot

http://www.engineersedge.com/hydraulic/tank_internal_floating_roofs.htm

http://www.hghouston.com/float.html

http://www.cbi.com/about/articles/PNG_article.pdf

Addtionally, this month's issue of "Hydrocarbon Processing" contains an excellent article on tank roofs and selection criteria.

My opinion only

-MJC

 

[kirnsi]

Yes, Sorry MJ , it is an internal floating roof tank with cone roof on the top. we wanted to put that room on high legs and for that we needed to send men (with fresh air) between two roofs and they wanted to know if they can turn the nitrogen off for an hour. thanks for that links on the tanks.