What is Fixed roof tank?
The fixed roof tank is a storage tank to store liquids, consisting of a cone-shaped or dome-shaped roof that is permanently affixed to a cylindrical shell. That is opposite to the floating roof tank. However, the internal floating roof tank is a combination of fixed roof tank and floating roof tank. Newer fixed roof tanks are typically fully welded and designed to be both liquid- and vapor-tight. Older fixed roof tanks, however, are often riveted or bolted, and are not vapor tight.
A breather valve (pressure-vacuum valve) is commonly installed on the fixed roof tank. It allows the tank to operate at a slight internal pressure or vacuum. The valve prevents the release of vapors during very small changes in temperature, barometric pressure, or liquid level. Fixed roof tanks without breather valves will generally be freely vented; thus the emissions from a fixed roof tank can be non-trivial. Gauge hatches, sample wells, float gauges, and roof manholes provide accessibility to the fixed roof tank, and also act as potential sources of volatile emissions.
Applications of fixed roof tank:
Storage tanks in general, and fixed roof tank 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. Fixed roof tanks are typically used to store liquid products that have relatively low volatilities and flash points.
