Operations & Design for FR Atmospheric Tanks
Operations & Design for FR Atmospheric Tanks
(OP)
I need some expert opinions regarding API650 floating roof tanks. My current project expects to buy a number of these tanks, but I see a few problems I'm unsure about. First, the design temperature is up to 230 degrees F, which I think exceeds API650 limitations. Obviously high temperature atmospheric tanks are built, but I'm not sure how the regulations change with higher temperatures. Second, the client's process engineer asked me how a floating roof tank responds to fillings, emptyings, and cleanout operations. (Sorry this isn't glamorous stuff, but it is down-to-earth.) Specifically, he wanted to know how air was vented during initial (and subsequent)filling, how a complete emptying of the tank could be accomplished, and was steam cleaning possible. I'm always worried when dealing with pressure and "atmospheric" tanks, so this is a real challenge to me. The client is asking me what sort of internal/external pressures develop during these operations, and can the tank handle this. I need "An Idiot's Guide to Atmospheric Tank Operations and Design", but don't have the resources available here.
Other pertinent information:
Tanks will hold several types of heavy crude oil at 160 to 180 to possibly even 205 degrees F (Design = 230).
Several sizes being used from 25,000 bbl to 200,000 bbl (or 70 to 200 ft.).
Some of the tanks will have internal steam coils for temperature maintenance.
Site is pretty remote. Thanks.
Other pertinent information:
Tanks will hold several types of heavy crude oil at 160 to 180 to possibly even 205 degrees F (Design = 230).
Several sizes being used from 25,000 bbl to 200,000 bbl (or 70 to 200 ft.).
Some of the tanks will have internal steam coils for temperature maintenance.
Site is pretty remote. Thanks.





RE: Operations & Design for FR Atmospheric Tanks
I once worked in an Aussie Lube refinery, using Saudi crude as feedstock, and the bottoms were quite thick. This had to be heated to the sort of temperature you mention, just to be able to pump it as boiler fuel. In that case, the bottoms tank was a fixed roof (although much smaller than you mention.
A useful feature that we had was a bayonet-type U-tube heater inserted into the tank by the outlet. This enabled thinning of the contained liquid only at the point where it was needed.
RE: Operations & Design for FR Atmospheric Tanks
RE: Operations & Design for FR Atmospheric Tanks
A floating roof has vents that open when the roof lands on its legs. When an empty tank is filled, air/vapor will just vent out of these vents until the roof starts floating. Normally, the floating roof would be operated between a high and low level, with landings minimized for emissions reasons.
I'm not sure about the steam cleaning specifically, as that would depend on the details. The main thing to consider would be adequate vacuum relief vents in the floater or in any fixed roof so that condensation of the steam couldn't suck a tank in. Steam under pressure would never be used in an atmospheric tank, as the allowable pressures for large tanks is usually only slightly above the weight of the roof plate.
A lot of the products that require heating don't require floating roofs- just fixed roofs.
RE: Operations & Design for FR Atmospheric Tanks
RE: Operations & Design for FR Atmospheric Tanks
RE: Operations & Design for FR Atmospheric Tanks
RE: Operations & Design for FR Atmospheric Tanks
RE: Operations & Design for FR Atmospheric Tanks
RE: Operations & Design for FR Atmospheric Tanks