Pressure and vacuum relief valve mechanism for a fluid storage tank

Abstract From the Canadian patent

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 single, integral valve member is movable in the bore of the housing. The valve member has a plurality of valve seats formed thereon and valve operable closure means cooperably engaged respectively with the valve seats. There is a valve seat and closure means for relieving excessive pressure and a valve seat and closure means …