Pressure and vacuum relief valve mechanism for a fluid storage tank

摘要

A pressure and vacuum relief valve mechanism which can be installed in a vent opening in the top wall of a fluid storage tank. The valve mechanism includes a valve housing with a central bore therethrough. One end of the bore communicates with the vent opening to ambient atmosphere and the opposing end communicates with the interior of the tank above the stored fluid. A valve seat within the bore. A single, integral valve member is movable in the bore of the housing. The valve member has a valve component or head formed thereon cooperably engageable with the valve seat within the bore for relieving excessive vacuum in the tank interior. The integral valve member also includes a valve seat and a cooperating valve head for relieving excessive vacuum in said tank interior. These valving arrangements normally being biased closed. There is a third overturn valve seat and cooperable valve closure component or head normally operable to maintain this valving arrangement open but operable to close the same when the tank is tilted or overturned so as to prevent leakage of stored fluid through the vent opening.