With Elastomer Seal: The Tri-Seal Flange system is illustrated below.
These flanges have protruding metal lips which serve several purposes. They protect the sealing surface of the flange and regulate the sealing compression of the elastomer seal. When these lips butt (metal to metal), the “O”-ring is properly torqued and confined by metal on all sides. This creates a dynamic sealing action not only on the sides of the “O”-ring but on the OD as well. The result of this dynamic seal is that the flange is capable of holding both high vacuum and high pressure sealing.