The internal floating roof in a fixed roof tank with ifr design must float on the liquid surface except when the floating roof must be supported by the leg supports.
Floating roof fixed roof tank.
The internal floating roof must be equipped with a continuous seal between the wall of the tank and the floating roof edge.
Of currently used tank designs the fixed roof tank is the least expensive to construct and is generally considered the minimum acceptable equipment for storing liquids.
Floating roof tank can be divided into two types internal floating roof and external floating roof.
However by reducing emissions the increased costs can be offset or justified on the basis of reduced product loss though evaporation a product savings and less impact to the environment.
Floating roof tanks are commonly protected against lightning ignition by bonding the floating roof to the seal shoes at no less than 3m 10ft intervals use of insulating sections in the hanging linkages covering sharp points on hangers with insulating materials and installation of electrical bond straps across each pinned hanger joint.
Tanks with external floating roofs are used primarily to contain liquids with high vapor pressures when the vapor emissions from fixed roof tanks would exceed the standards set by the local jurisdiction.
A typical fixed roof tank consists of a cylindrical steel shell with a cone or dome shaped roof that is permanently affixed to the tank shell.
Floating roof tanks are generally about twice as expensive to construct as fixed roof tanks so there is a trade off of risk against cost.