GB845782A - Improvements in expansion joints for pipes - Google Patents

Abstract

845,782. Expansion joints. GENERAL ELECTRIC CO. Nov. 19, 1957 [Dec. 17, 1956], No. 35993/57. Class 99(1). In a sealing assembly for an expansion joint of a turbine connecting the inlet conduit 3 to the casing 1, the assembly being arranged in a recess 1a of the casing and preventing the leakage of fluid from the inlet through the recess to a low pressure area in the casing and including at least a first ring engaging the outer surface of the conduit and spaced from the wall of the recess and a second and axially adjacent ring engaging the wall of the recess and spaced from the outer surface of the conduit, and retaining means for limiting axial movement of these rings, the sealing assembly comprises a first group of rings 5a ... 5d exposed to the fluid in the conduit and retaining means 6 for limiting axial movement of that group of rings; and retaining means 8 for limiting axial movement of a second group of sealing rings 5e ... 5h axially spaced from the first group of rings. An annular chamber 17 arranged between the two groups of rings is maintained at a pressure intermediate the pressure in the conduit and the low pressure area and providing a distribution of axial compression forces from the means 6 to the means 9 to facilitate radial expansion of the conduit. As shown, the conduit 3 extends into the cylindrical recess 1a and through an opening in the casing 2, and has integral therewith a nozzle box assembly 4 for directing high-pressure steam on to the blades of a rotor 13. The upper group of solid rings 5a... 5d are retained in place by a segmental ring 6 disposed in an annular recess 1d and the segments of that ring are prevented against moving radially by a retaining ring 7 provided with openings 7a; similarly the rings 5e ... 5h are retained in place by rings 8, 9. Axial clearance spaces 7b, 7c between the rings 7 and 5d and 6 prevent the transmission of compressive forces on to the ring 5e, and an axial clearance space 9a prevents compressive forces being transmitted to the ring 9. The latter is held in place by tack welds, locking screws, or by peening over the adjacent portion of the casing as indicated at 15, the exterior end surface of the ring being provided with a number of circumferentially spaced notches. To prevent sticking of the groups of rings, the conduit has a coating 3a selected with reference to the material of the rings, and there is a clearance space 11 between the ring 9 and the casing 1. The pressure differential across the retaining rings is minimised by providing a passage 1b communicating with the chamber 17 and the space between the blade wheel 14 and nozzle diaphragm 15, the conduit 20 having located therein an orifice 28 across which is connected a flow meter 25 for detecting leakage past the expansion joint.