Abstract: The relief valve assembly has a spring-loaded poppet valve that vents the interior of a transport tanker to the atmosphere when gaseous pressure within the tank exceeds a predetermined limit. Sudden surge protection from a pressure spike created by liquid within the tank during the instant that the tank strikes the ground during accidental roll over is provided to keep the poppet valve closed during the surge condition. A reaction piston having one face that counteracts the face of the poppet valve is exposed to pressure within the tank simultaneously with the poppet valve, but the counteracting effect of that surface is normally overcome by a neutralizing chamber on the opposite side of the reaction piston which is likewise exposed to the interior of the tank.

Abstract: A relieving valve for a fluid or liquid storage tank to permit release of pressure from inside the tank as necessary. A piston is movable within the valve to open the same to atmosphere as pressure builds up slowly therewithin. Upon occurrence of a sudden or rapid pressure rise in the tank, such as when the fluid therein surges against the valve, a snubber assembly in the valve is moved by said pressure rise to a partially closed position to impede the rate at which pressure can build within the valve and thus increase the time before which the valve opens to atmosphere.

Abstract: 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.