Tank isolation valve

A tank isolation valve assembly for use in an effluent discharge path to provide a vapor barrier to prevent back flow of gases while enabling fluid and solid substances to pass therethrough in a desired flow direction, said tank isolation valve assembly comprising:

• a main housing member having a peripheral flange joined with an apertured outlet wall, said outlet wall defining a valve member receiving region including an apertured bottom wall portion, a side wall portion and a wall portion formed at an angle with respect to and joining said bottom and side wall portions;
• a first apertured mounting gasket received about the side wall portion of said main housing member adjacent said peripheral flange, and a second apertured mounting gasket positioned on the opposite side of said peripheral flange from said first mounting gasket, each said gasket having an outer diameter greater than the outer diameter of said peripheral flange;
• a second member comprising a valve plate having a convex peripheral portion mounted in sealing engagement with said wall portion, and having an apertured wall structure with a valve member retaining surface facing said valve member receiving region;
• and
• an isolation valve member comprising a flexible diaphragm mounted in sealing relationship between said valve member receiving region and said valve member retaining surface, said valve member being provided with a first plurality of boss receiving apertures, said valve plate being provided with a second plurality of boss receiving apertures, and said outlet wall including plurality of valve member mounting bosses extending therefrom and received within said first and second plurality of boss receiving apertures,
• said flexible diaphragm comprising a pair of disks fabricated from an elastomeric material, each disk having a plurality of slits extending from a central region thereof and wherein said disks are mutually positioned with solid portions of one of said pair of disks overlying the slits of the other one of said pair of disks, said slits being of a length to permit the passage of both fluid and solid effluent therethrough, with at least some of said slits terminating in enlarged openings.