Artifact: Vent and Relief Valve, Liquid Oxygen Propellant Tank, Saturn IB Second Stage & Saturn V Third Stage (S-IVB)

An Apollo Saturn V/IB S-IVB (Third Stage) Liquid Oxygen (LOX) tank propulsive venting Vent and Relief Valve manufactured by CALMEC under subcontract to Douglas Aircraft Corporation (primary design/builder for the S-IVB). The Vent and Relief valve is pneumatically operated using helium gas from the stage pneumatic control system. It is opened upon receipt of a ground command prior to propellant (LOX) fill operations, and the boil-off of LOX during loading is directed through the propulsive vent in the aft skirt of the stage. When LOX tank pressurization commences, the valve is closed and placed in the Relief position. The valve is calibrated to open at a maximum of 45 psia and reseat at 42 psia. During flight, relief venting is normally accomplished via a separate non-propulsive vent valve. Propulsive venting in flight is used to support ullage (positioning of propellants towards the bottom of the stage in preparation for J-2 engine start/restart).

A similar Vent and Relief valve was installed in the Liquid Hydrogen (LH2) tank; an example is included in this collection and is discussed in a listing immediately preceding (above) this artifact.