Patent ID: 7413194

Claim:
A segmented annular seal assembly comprising an annular seal ring consisting of a plurality of arcuate seal segments disposed end-to-end to form an annular seal operative in use to seal a leakage gap between a fixed part and a relatively rotatable movable part, wherein, in use, there is an upstream pressure region of high pressure on one side of the annular seal and the fixed part and a downstream pressure region of lower pressure on the other side of the annular seal and the fixed part, the fixed part having an upstream wall and a downstream wall that define a recess within which the seal segments are disposed, the upstream wall and the downstream wall being spaced apart such that the seal segments are free to follow radial movement of the movable part relative to the fixed part, at least a portion of each of the seal segments being in sliding contact with at least a portion of each of an inner face of the upstream wall and an inner face of the downstream wall of the fixed part, the inner face of the downstream wall of the recess being formed with a first pressure balance region within the recess adjacent the downstream side of the seal segments, the inner face of the upstream wall of the recess being formed with a second pressure balance region within the recess adjacent the upstream side of the seal segments, and a first communication passage through the fixed part linking the first pressure balance region in the downstream wall of the recess with the upstream pressure region via an opening in the outer face of the upstream wall, and a second communication passage, separate from the first communication passage, through the fixed part linking the second pressure balance region in the upstream wall of the recess with the downstream pressure region via an opening in the outer face of the downstream wall.