A simple analysis method is described in ASCE (1986). This phenomenon has been particularly studied in Japan, where experimental tanks have been studied to determine their response in cases of real earthquakes. When testing a tank it is, first of all, necessary to determine the liquid motion and the forces exerted by it on the tank.
Experience indicates the possibility of damage at the roof-wall join (buckling and breaks), of damages to the base of the lateral wall (‘elephant foot’ buckling), of damage to the anchor components between the tank and its foundation (if existing) and damage to internal components. Tanks of liquid, specially of light construction ( atmospheric tanks), are subject to peculiar phenomena during an earthquake, all of them are related to the formation of internal waves and to their interaction with the walls and with the roof of the tank. Gianni Petrangeli, in Nuclear Safety, 2006 Tanks A fabric expansion chamber housed in a compartment on top of the tank roof also permits variation in volume. There are lifter-roof types in which the roof either has a skirt moving up and down in an annular liquid seal or is connected to the tank shell by a flexible membrane. They may have floating roofs of the double-deck or the single-deck type. Sometimes vents are manifolded and led to a vent tank, or the vapor may be extracted by a recovery system.Īn effective way of preventing vent loss is to use one of the many types of variable-volume tanks.
Excessive losses of volatile liquids, particularly those with flash points below 100 ☏ (38 ☌), may result from the use of open vents on fixed roof tanks. The principals of this standard can be applied to fluids other than petroleum products. API Standard 2000, venting atmospheric and Low Pressure Storage Tanks, gives practical rules for vent design. Boyce, in Gas Turbine Engineering Handbook (Fourth Edition), 2012 Fixed Roof TanksĪtmospheric tanks require vents to prevent pressure changes, which would otherwise result from temperature changes and the withdrawal or the addition of liquid.
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