Patent GB-378285-A (GB)
Title: Improvements in and relating to governing mechanism for elastic fluid turbines
IPC: F01D17/26
Filed: 1931-11-26
Abstract: 378,285. Governing turbine plant. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London.- (Assignees of Caughey, R. J. ; 910, Living- ston Avenue, Schenectady, New York, U.S.A.) Nov. 26, 1931, No. 32834. Convention date, Nov. 26, 1930. [Classes 57, 110 (iii), and 122 (iv).] In a turbine plant comprising an H.P. turbine 1 and an L.P. turbine 2 normally driven by the exhaust of the H.P., an intercepting valve 26 is arranged in the connecting conduit 5, a highpressure steam supply 45 is provided for the L.P. turbine, and the governor gear 41, 51 for the L.P. is adapted to be connected to control either the intercepting valve 26 or the regulating valve 47 for the supply 45. Normally the governor gear for the L.P. is ineffective, the machines being kept at the same speed by having the alternators driven by them connected in parallel. The speed is then controlled by the governor gear of the H.P. turbine which comprises an adjustable governor 20 controlling the main regulating valve 7 through a relay 21, and an emergency governor 16 which at excess speed acts through a relay 11 to trip the latch 9 of the combined trip and throttle valve 6a. The emergency control is of the type described in Specification 181,646, [Class 57, Governors &c.]. The linkage of the L.P. speed governor 41 may, as shown in Figs. 1 and 2, be connected up in two ways depending upon whether the L.P. turbine is to be supplied with exhaust from the H.P. section, or with high-pressure steam by the connection 45. In the first case the pilot valve of the servomotor 44 which controls the regulating valve 47 is locked to keep the valve closed by a link 66 connected to the follow-up linkage 55, 56, 57. The floating governor lever 38 is connected by a link 37 to the pilot valve 33 of the reverser 31 in the oil circuit of the motor 29 which controls the interceptor valve 26. Governor 41 is set for speed slightly higher than normal, but lower than that for the emergency governor. In operation, with this arrangement of the links 66, 3'7, should the H.P. stop valve 6a be tripped, the L.P. governor 41 will act to close the interceptor valve 26, and if it fails, the trip 53 of the L.P. emergency governor will bring about the same result. This is necessary because the volume of steam left in the conduits 4, 5, and the reheater to which they are connected, might, when the H.P. turbine is shut down, cause overspeeding. In the second case, if, when the H.P. turbine has been shut down, it is desired to drive the L.P. turbine by high-pressure steam introduced at 45, the linkage of the L.P. governor 41 is altered as shown in Fig. 2. The locking link 66 is disconnected from the pilot valve of the servomotor 44, and the link 37 is disconnected from the pilot valve 33, and connected to the bar 57. The combined trip and throttle valve 46 is then opened, and the governor 41 takes over control of the regulating valve 47. If excessive speed is attained a trip 52 on the emergency governor 51 causes a piston 62 to drop and so lower the pilot valve to close the regulator 47. At the same time the stop valve 46 is tripped by a relay device 48.