Abstract: Two seal elements are respectively mounted on generally coaxial relatively rotatable members so that each seal element is capable of relative radial movment with respect to its associated member. One of the seal elements is mounted on its associated member in such a manner that they remain coaxial. The seal elements have confronting radially spaced apart surfaces which are so configured that together they define a hydrodynamic gas bearing. The arrangement is such that upon the relative rotation of the members said seal element which is mounted so as to remain coaxial with its associated member hydrodynamically supports the other seal element so that they remain coaxial.

Abstract: A seal arrangement suitable for sealing between two coaxially mounted, axially restrained, radially spaced apart and relatively rotatable members comprises two concentric, ring-shaped seal elements having adjacent sealing faces. The seal elements are mounted on the respective members by a spline and groove arrangement which permits radial growth or shrinkage of the relatively rotatable members due to their thermal expansion or contraction without such growth or shrinkage being transferred to the seal elements. The arrangement insures that the gap between the sealing faces of the seal elements remains substantially constant during thermal variations.