GB694919A - Improvements in combined shut-off and throttle valve assemblies - Google Patents

Abstract

694,919. Valves. BRITISH THOMSONHOUSTON CO., Ltd. July 10, 1951 [July 26, 1950], No. 16324/51. Class 135 A combined shut-off and throttling valve for controlling, e.g., a steam turbine has a cap-like throttling valve member 15 slidable on a fixed guide piston 12 carried by arms 14 welded to or integral with a valve seat member 7, and a shutoff valve member 20 slidable on the valve member 15 and on a fixed piston 22 supported by studs 23 mounted on the piston 12 and passing through clearance holes 15a in the valve member 15. The throttling valve member is actuated, through a rod 17, by a hydraulic motor &c., as in Specification 659,643, and the shut-off valve member is actuated, through a rod 26 having a lost-motion connection with the valve member and an auxiliary valve member 27 which controls admission of inlet pressure to the interior of the shut-off valve member for balancing, by manual and automatically actuated emergency mechanism also as in Specification 659,643. The seat member 7, which may be secured in the valve housing by tack-welds, has a passage of Venturi form, and the two valve closure members 15, 20 are bevelled exteriorly at 16, 20a so that, when open, they provide a substantially smoothly convergent, annular, entrance to the passage through the seat member. The fixed guide pistons 12, 22 have circumferential grooves 13, 24 with or without piston rings. The sliding surfaces of the valve members may be nitrided and ground. In a modification, the upper fixed piston 22 is omitted.