Storage tank for a volatile liquid having an outer roof and an internal floating roof a vent pipe having one end in liquid communication with the bottom space of the tank and the other end extending in vapor communication to outside the tank means to support the floating roof above the tank bottom and above the liquid when the liquid contents drops below a predetermined level and port means.
Floating roof tank breather vent.
The vents in the floating roof protect the roof and rim seal and accommodate liquid movement and thermal breathing.
The floating roofs can be either external i e with open top tanks or internal i e inside fixed roof tanks.
The floating roof rim vent has a cast body which can be flanged or threaded for connection to the storage tank the weatherhood protects the exhaust port of the rim vent from atmospheric conditions.
Depending upon how a tank receives product there are instances where entrained vapour may be released into the tank from the filling pipeline.
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.
The rim vents are fitted with a hinged pallet lift set to lift when the set pressure in the tank exceeds the set pressure allaowing the air gas to flow.
For a tank with a fixed roof and internal floating roof but without a gas blanket.