Available to 30 ksi ranges. Unsupported stem subtracts from plug area resisting this force. Original Seal Requires careful design not to yield or overpressure seal area. Can be difficult to open after use. Requires relatively tight tolerances.
Modification Uses a metal seal ring between body and cover.
Sealing surfaces are at different angles to give line contact. Seals Major problem is o-ring extrusion through assembly clearance gaps. Most commercial designs now use back-up rings successfully to near 100 ksi. With gas seals, permeation should also be considered. SST or Nylon Wedge ring Bronze or Beryllium Copper 7.