Full definition
Seal designed to prevent atmospheric air ingress into systems under vacuum. Lip or face orientation is reversed relative to pressure seals. Low gas-permeability materials required: FKM Viton, VMQ silicone, EPDM. Applications: evaporators, vacuum dryers, reactors and vacuum filtration systems (10⁻³ to 1 bar absolute). Leak testing with helium mass spectrometer to verify integrity below 10⁻⁶ mbar·l/s.