GB813958A - Seal for rotating machinery - Google Patents

Abstract

813,958. Elastic-fluid turbines; stuffing-box substitutes. GARRETT CORPORATION. May 10, 1957 [May 16, 1956], No. 14965/57. Classes 110 (3) and 122 (5). A seal between the stator 10, Fig. 1, and rotor 18 of a turbine or other rotary machine comprises an axially-movable and floating sealing ring 42 which is carried by the stator so as with the rotor to separate two spaces 100, 106 subjected to different pressures and provided with two annular sealing ribs 52, 54 on the face presented to the rotor and passages 56 connecting the space 102 between the ribs with a rear chamber 104 enclosing the rear face of the ring, the arrangement being such that the balance of pressure on the two faces of the ring maintains the desired clearance between the ring and rotor. The ring is mounted in an annular opening 40 formed in the stator 10 by two wall sections 38, 12 connected by an annular cover 58 to form the chamber 104. In operation, high pressure fluid, which is admitted to the turbine rotor 18 through a nozzle ring 22, escapes through the clearance space 30, 28 between the nozzle ring and rotor into the space 100 where it acts upon the surface 41 of the ring 42 to increase the gap between the rib 52 and rotor surface 34. The fluid in the space 102 then passes both through the passages 56 to the chamber 104 to act upon the rear side of the ring to return it to its normal position and through the clearance between the rib 54 and surface 34 into the low-pressure space 106 where it may then escape to atmosphere through vents 98. By suitably positioning the ribs on the ring the pressure in the chamber 104 may be arranged to balance the pressure acting upon the ring in the spaces 100, 102, 106 thereby maintaining the desired clearance. The ribs 52, 54 may engage a frusto-conical section on the rotor surface, and the clearance between the two ribs and the rotor surface may be equal or unequal. Bosses 70 on the ring co-operate with mating bosses 68 on the stator to prevent rotation and to limit the extreme axial movement of the ring. Piston rings 44, 48 may be provided to seal the outer and inner peripheries of the ring 42 and have in their operative faces a circumferential groove 80, Fig. 2, and axial grooves 82 which reduce the surface area in order to permit free movement of the ring and communicate with the higher pressure spaces. If desired, one or other of the piston rings may be designed to allow a slight leakage or, alternatively, a bypass may be arranged through the ring 42 from the chamber 104 to the space 106. The balance of pressure effect may also be used to balance the end thrust of the rotor.