Patent ID: 8177090

Claim:
A combination liquid petroleum floating roof storage tank and emergency drainage system for draining rain water accumulated on the roof of said storage tank, comprising: a. a storage tank including a floating roof, side walls having a circumferential inner surface and a base which define an interior space, b. at least one rainwater drain duct having an inlet adapted to receive rain water accumulated on said roof, said drain duct having walls which define a predetermined generally round bore diameter, said drain duct extending downward about a central axis and communicating with said interior space, c. a petroleum vapor barrier valve in said drain duct at an axial location downstream of said inlet, said valve formed as a multi-blade rotor that is rotatably mounted in said drain duct for rotation about a central rotor axis extending generally perpendicular to said drain duct central axis at said axial location, d. said rotor comprising a central axle means and a plurality of generally semi-circular blades, each of said blades having a base and a body part extending radially outward from said base to an exposed semi-circular peripheral edge, said exposed edges of said plurality of blades defining a generally spherical shape having diameter corresponding generally to said round bore diameter of said duct at said axial location.