member 38 springs 66 are essentially enclosed by a generally cylindrical cover 74 which encircles flange 72 of member 38 and is bolted to housing flange 60 the rear surface 52 of back up ring 40 the rear surface 51 of the member 38 and the annular surface 61 of housing flange 60 cooperatively define an annular cavity 76 open to high pressure fluid back up ring 40 is axially drilled at 78 to provide a fluid passageway between cavity 76 and cavity 80 cavity 80 being defined by o rings 82 84 a portion 86 of a rear face 44 of seal ring 22 and reduced portion 88 of the front face 42 of back up ring 40 the effective pressure on face 86 is substantially the same as on face 28 thus the fluid pressures on opposite ends of seal ring 22 are substantially the same the inner surfaces of the stationary seal ring 22 and its back up ring 40 are spaced from shaft sleeve 12 and define with shaft sleeve 12 a first zone 90 communicating with low pressure zone 18 and the outer surfaces of seal ring 22 and back up ring 40 define with member 38 a second zone 92 to insure that the pressure on the outside surface of seal ring 22 in zone 92 is the same as on the inside surface of seal ring 22 in zone 90 back up ring 40 is radially drilled at 94 and member 38 is angularly drilled to provide a fluid passage 96 bridging o ring 82 because the pressure on the inner and outer surfaces of the seal ring 22 and the back up ring 40 is the same or substantially the same compressive loads due to pressure differentials do.