Floating Roof Tank Vent Design

The roof rises and falls with the liquid level in the tank.

Floating roof tank vent design.

The floating roofs can be either external i e with open top tanks or internal i e inside fixed roof tanks. Today controlled gas venting in to the atmosphere is becoming more and more important due to environmental regulations. Floating roofs have been designed and used for more than a century. It consists of an open topped cylindrical steel shell equipped with a roof that floats on the surface of the stored liquid.

For normal venting api 650 g 8 3 and h 6 2 specifies vents in the fixed roof tank shell and internal floating roof. Closed floating roof tank this has an internal floating roof but eliminates natural ventilation of the tank vapor space. 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. 2 16 failure mode due to seismic effects on floating roof tank 34 2 17 fitting design and requirement 36 2 18 typical fitting and accessories for floating roof 37.

For a tank with a fixed roof and internal floating roof but without a gas blanket. Instead the cfrt is equipped with a pressure vacuum pv vent and may even include a gas blanketing system such as that used with fixed roof tanks these tanks are designed as in appendix c of the api standard 650. Floating roof storage tanks. Vii 2 18 1 roof seal system 37 2 18 2 support leg 38 2 18 3 roof drain system 39 2 18 4 vent bleeder vents 43 2 18 5 centering and anti rotation device 44.