Importance

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Abstract

In a turbine inclusive of: a turbine shaft having a longitudinal axis, a steam pipe, a shell circumadjacent the pipe, the pipe and shell being shiftable in vertical and transverse and axial directions relative to the longitudinal axis of the shaft, and a seal assembly disposed between the pipe and shell and comprising a stack of interdigitated relatively large and small piston rings, the improvement comprising: each large ring loosely fitting inside the shell during nonoperative conditions and firmly and sealingly engaging the shell during operative conditions; and having a coefficient of thermal expansion greater than that of the shell for expanding at a rate faster than the expansion rate of the shell under a condition of increased temperature, each small ring loosely fitting around the pipe during nonoperative conditions and firmly and sealingly engaging the pipe during operative conditions; and having a coefficient of thermal expansion less than that of the pipe for expanding at a rate slower than the expansion rate of the pipe under a condition of increased temperature, with the large and small rings tightening upon the respective shell and pipe respectively under an increasing temperature condition and shrinking from the respective shell and pipe respectively under a decreasing temperature condition.

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First Claim