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

Apollo Saturn V S-IVB (Third Stage) Gaseous Hydrogen (GH2) dual function Tank Vent and Relief Valve manufactured by CALMEC under subcontract to Douglas Corporation (prime for the S-IVB NASA CONTRACT NAS 7-101). The Valve provided relief and overboard venting of excess Gaseous Hydrogen from the fuel tank which serviced the J-2 Rocket Engine; routing via the non-propulsive vent ducts into space (during flight) or the GH2 Burn Pond (during ground fueling operations).

Vent valve actuation was commanded from an external ground signal during fill operations, and from the flight sequencer during liftoff and flight. The vent valve was designed to open in a maximum of 0.1 second upon command. The relief valve, which provided a backup capability in case of vent valve failure, opened at 42 psia and reseated at 39 psia, and had a flow/relief capability of 2 pounds/second at sea level.