Roof selection is decided largely by the content's propensity to form vapours* the losses due to the emissions* the costs for mitigation or recovery of the emissions and the environmental laws in place regarding the emissions.

Fixed roof is generally the first choice for storage* however if any of the above prevail* then floating roofs are used.
Fixed Roof Tanks are used to store materials with a true vapor pressure of less than 1.5 psia absolute.
Floating Roof Tanks are preferred for storage of petroleum products with a true vapor pressure of 1.5 to 11 psia absolute. Internal floating roofs accord greater control over emissions and vapour recovery than External floating Roof.

Medium flash point products as Crudes* Diesel* Kerosene*Naphtha* Reformate and the like are stored in external Floating Roofs. However if storage Volume is small* and thereby emissions are not a concern* Fixed Cone Roofs can be used for storage.

Low Flash point products as ethanol* gasoline* Motor Spirit* Aviation Turbine Oil* Isomerate are stored in Internal Floating roof tanks.

Glycol and Methanol could be stored in fixed roof vertical tanks. Horizontal tanks with domed ends could also be used for glycol.


LINUS