Image Number 2 for United States Patent #6234198.
A combined vacuum relief and pressure containing valve assembly for relieving vacuum developing within an associated vessel and for containing elevated pressures developing within the vessel. The valve assembly has a housing having two communicating passageways demarcated by a valve seat. The first passageway communicates to the open atmosphere and also with the valve from below the valve seat. The valve is a ball constrained to move only vertically above its seat. The second passageway communicates with the valve from above the valve seat. The second passageway extends below the valve so that when the valve assembly is connected to the associated vessel, pressures prevailing within the vessel act on the valve from above. Therefore, vacuum prevailing within the vessel, acting in concert with relatively higher ambient temperatures, will draw the valve into the open position. At zero pressure differential, gravity urges the valve into the closed position and maintains a seal. High pressures within the vessel further urge the valve into the closed position. The valve seat and the valve abut along a circular line of contact when the valve is in the closed position.