Abstract

A flange union is disclosed which is provided with inner and outer annular metal-to-metal seals and an optional resilient seal and/or insert. In one embodiment, the two metal-to-metal seals are formed simultaneously, and in another embodiment they are formed sequentially thereby allowing the second to be used as a back-up seal. The configuration of the metal sealing surfaces is such that an annular metal-to-metal line seal of minimum surface area is formed closely adjacent the internal diameter of the bore, and an annular metal-to-metal line seal is formed, or is capable of being formed, outward therefrom. This sealing structure results in markedly less stress and strain on the flange bolts to achieve and maintain the desired sealing pressure. Male-female sealing surfaces mate adjacent the internal diameter of the bore, and the flange union is self aligning in that area. The flange union will seal effectively with the flange members being either in or out of alignment. Inserts are used to extend the life of the flange union and to render it useful for a number of other purposes.