Abstract

A fluid-tight coupling and sealing apparatus for first and second tubes having high pressure fluid flowing therethrough comprising a non-metallic ring rigidly received in the first tube via an interference shrink-fit and a metallic, resilient annular sealing element rigidly coupled to and extending from the second tube and having a ring portion with a curved outer surface in contact via an interference fit with the inner surface of the non-metallic ring. The coefficient of friction between the metallic sealing element and the non-metallic ring is low, to minimize the moment required to angulate the apparatus under load, and the wear properties are optimal, to decrease the chance of galling along the sealing line and thus loss of sealing. The non-metallic ring is preferably formed of carbon-graphite and is rigidly secured in the first tube by first heating the tube to thereby increase its size by thermal expansion; inserting the non-metallic ring, which is at room temperature, into the heated tube; and then allowing the tube to cool and therefore reduce in size into an interference shrink-fit contact with the outer surface of the ring. Following this, the resilient sealing element is inserted into the non-metallic ring with an interference fit.