Cone roof tanks with internal floating roofs

Cone Roof Tanks with Internal Floating Roofs... 

Cone roof tank with internal floatingcover—an atmospheric storage tank with a fixed cone-shaped roof and an internal floating cover of one of the following designs ... 

Two types of designs are commonly applied. For cone top tanks or internal floating roof tanks with other than pontoon decks, multiple foam makers are mounted on the upper edge of the tank shell. These systems are designed to deliver and protect the entire surface area of the liquid of the tank. For open and covered floating roof tanks with pontoon decks, the foam system is designed to protea the seal area. Foam makers are mounted on the outside of the tank shell near the rim and foam is run down inside to the seal area that is provided with vertical barrier adjacent to the seal area i.e., a foam dam to hold the foam in the seal area. This method tends to cause the movement of cooler product to the surface to aid in extinguishment of... 

A cone roof tank with an internal floating roof that does not meet these criteria or uses plastic foam for flotation, even if encapsulated in metal or fiberglass, should be fire protected by side wall foam chambers suitable for the full (surface) area of the tank. This type of internal floating-roof installation is not recommended, particularly for flammable liquids. 

The foam concentrate used with subsurface systems should be a fluoroprotein type for best results, although some AFFF foams are listed for substitutable application (because of their "fuel shedding" properties). The minimum foam solution rate should be 0.3 gpm/ft (12 Ipm/m ). The supply of foam liquid should be adequate to operate the system for 20 minutes. The foam injection point must be above the level of any residual water in the bottom of the tank. Subsurface foam application is not recommended for open or covered floating roof tanks or cone roof tanks with internal floating covers. 

Cone roof and floating roof tanks are usually correlated using vs. volirme, with materials of construction as another variable. The cost of internal heat exchangers, insulation, unusual corrosion allowance, and special internals should be separated from the basic cost of the tank in the correlations. 

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