A fixed roof tank is a type of storage tank, used to store liquids, consisting of a cone- or dome-shaped roof that is permanently affixed to a cylindrical shell. Newer storage tanks are typically fully welded and designed to be both liquid- and vapor-tight. Older tanks, however, are often riveted or bolted, and are not vapor tight. A breather valve (pressure-vacuum valve), commonly installed on many fixed roof tanks, allows the tank to operate at a slight internal pressure or vacuum. This valve prevents the release of vapors during very small changes in temperature, barometric pressure, or liquid level.[1] Fixed roof tanks without breather valves will generally be freely vented;[2] thus the emissions from a fixed roof tank can be non-trivial. Gauge hatches, sample wells, float gauges, and roof manholes provide accessibility to these tanks, and also act as potential sources of volatile emissions.[3][4]
Applications
editStorage tanks in general, and fixed roof tanks in particular, containing organic liquids can be found in many industries, including:
- petroleum production and refining
- petrochemical and chemical manufacturing
- bulk storage and transfer operations
- other industries consuming organic liquids[2]
Fixed roof tanks are typically used with products that have relatively low volatilities and flash points.[5] Using a fixed roof tank to store a product with high volatility can lead to product losses as vapors escape the enclosure.[6]
See also
editReferences
edit- ^ BNH Gas Tanks. "Fixed Roof Tank". Retrieved 5 December 2015.
- ^ a b South Coast Air Quality Management District. "Supplemental Instructions For Liquid Organic Storage Tanks" (PDF). Retrieved 5 December 2015.
- ^ Werner Sölken. "Explore the World of Piping - Introduction to Storage Tanks". Retrieved 5 December 2015.
- ^ USA Environmental Protection Agency. "Alternative Control Techniques Document:Volatile Organic Liquid Storage in Floating and Fixed Roof Tanks" (PDF). Retrieved 5 December 2015.
- ^ Buckeye Fire Equipment. "Storage Tanks: Fixed or Semi-fixed Systems" (PDF). Retrieved 5 December 2015.
- ^ ISEC Company. "Fixed Roof Tank".