Abstract: An emergency valve assembly for a tank adapted to contain liquid such as for instance hazardous material, with the valve assembly including a valve head for closing the discharge port from the tank in an operative closed position of the valve head, and with a first operating unit coacting with the valve head for selectively opening the latter and a separate second operating unit coacting with the valve head for automatically closing the latter. The first operating unit has a portion adapted for accessibility from exteriorly of the tank and includes a fluid power connection to the first operating unit, for selectively supplying pressurized fluid to such operating unit; for causing opening of the valve head via such operating unit upon application of pressurized fluid thereto.

Abstract: A tank pressure and vacuum relief mechanism for relieving excess pressure or vacuum in a tank interior. The mechanism includes a housing disposed in a wall of the tank, such housing containing a one-way, normally-closed pressure relief valve for venting excessive pressure in the tank to the atmosphere. The housing also contains a one-way, normally-closed vacuum relief valve for admitting atmospheric pressure to the tank interior to relieve excessive vacuum therein. The mechanism seals completely on tank roll-over at any angle to prevent tank product leakage.