Patent GB-445869-A (GB)
Title: Improvements in or relating to steam generators
IPC: F22B35/10
Filed: 1934-10-17
Abstract: 445,869. Fluid pressure servomotorcontrol systems. SULZER FRERES SOC. ANON., Winterthur, Switzerland. Oct. 17, 1934, No. 29689. Convention date, Nov. 16, 1933. [Class 135] In a steam generator of the kind in which the water is fed to one end 3 of at least one tube 4 wherein it is evaporated and delivered from the other end 5 as superheated steam, and having at least one regulating device automatically controlled by a condition of the steam, a manually-operated device is provided whereby adjustment of the regulating device can be influenced as and when desired, such influence ceasing automatically after a predetermined interval. The steam condition may be temperature or pressure or any measurable value, variations of which are accompanied by variations in such conditions, and may control the feed-water supply pump 1 at the feed-end or at an intermediate point 17, the air and fuel supply valves 30, 29, the main steam delivery valve 31, or a steam byepass valve 32. The pressure control-device 28, 34 comprises a Bourdon tube 49, Fig. 2, connected to the delivery pipe 6 and operating, in accordance with pressure variations, a piston valve 50 controlling the flow of pressure medium from a supply pipe 51 to two pipes 40, 40<1>. The pressure in the pipe 40 acts on a spring-loaded piston-valve 55 and controls the admission and exhaust of pressure fluid from pipes 53, 54 to a chamber 150 so as to operate a piston 52 actuating a byepass valve 32 for relieving the pressure if this exceeds the required value. The pressure in the pipe 40<1> is applied to a piston 27, Fig. 1, movement of which actuates a needle valve 29 and a butterfly valve 30 controlling fuel and air supply respectively to the heating - device 24. One temperaturecontrol device 14 is situated at an intermediate part of the tube 4 and is actuated by the expansion of the tube between points 61, 62, Fig. 3. This causes movement of a piston-valve 63 so as to allow pressure fluid from a pipe 65 to act upon a piston 66 and actuate a piston valve 66<1> controlling the flow of pressure fluid from a, pipe 68 to a pipe 13, the pressure in which thus varies with temperature changes. Movement of the piston 66 tends to return the valve 63 to its neutral position. The pipe 13 has two branches 13<a>, 13<b> so as to transmit pressure to a piston 77 actuating a piston-valve 74, and a piston-valve 72 respectively. The valve 72 controls the flow of pressure medium from a pipe 70 through a pipe 104, 105 to a space beneath a piston 73 connected to a second piston 75 having a bleed port 76. The space 107 beneath the piston 75 communicates with the space 108 beneath the piston 77. As the pressure in the space 106 varies in accordance with temperature variation, change of temperature causes movement of the piston 75, the rate of which is affected by the rate of change of temperature due to the port 76 and which tends, through the lever 112, to return the valve 72 to its neutral position. A change of pressure, caused in the chambers 107, 108 by the rate of movement of the piston 75, is thus dependent on the rate of change of temperature. The resultant pressure on the piston 77 being dependent on the pressures in the chamber 108 and pipe 13<a>, thus varies with temperature and rate of change of temperature, and the valve 74 actuated thereby causes pressure fluid to be transmitted along a pipe 11 in accordance with such variations. The pressure in the pipe 11 is applied to a pistonvalve 78 in an apparatus 10 controlling the admission and exhaust of pressure medium from pipes 80, 81 to a chamber 117 so as to act on a piston 118 and thus vary the position of a switch-arm 9 of a motor 7 actuating the feed pump 1. The lower end of the piston 118 bears on a piston 82 furnished with a bleedpassage 123 and subjected to constant upward pressure from pressure medium in a pipe 79 and the fluid pressure in the chamber 120. Adjacent to the chamber 120 is a chamber 121 communicating therewith and containing a sealing piston 115<1> loaded by springs 115 also bearing against the valve 78. Thus, movement of the piston 118 tends to return the valve 78 to its initial position. An additional temperature-control device 23, Fig. 1, similar to the device 14 is situated in the delivery pipe 6 so as to set up a pressure in a pipe 38<1> corresponding to the temperature. This pressure is communicated by a pipe 38 to an apparatus 22 identical with the apparatus 10 and to an apparatus 33. The apparatus 22 controls a pump 17 supplying feed-water to an intermediate point in the boiler tube 4. A piston 58 in the apparatus 33, Fig. 2, is connected by a link-and-lever arrangement to the steamdelivery valve 31. A piston-valve 60 in the apparatus is spring-loaded and subjected to the pressure in the pipe 38 so that variation of pressure causes movement thereof to admit or exhaust pressure fluid to, or from beneath the piston 58 from or to pipes 56, 59 so as to vary the opening of the valve 31, exhaust taking place and causing closing of the valve 31 if the steam temperature falls below a predetermined limit. The hand-control device 16 comprises a number of piston-valves 124 which are operated simultaneously by a hand-operated cam-shaft 41 through pistons 126 and springs 48 so as to put chambers 128 into communication either with a pressure medium supply pipe 47 or with an exhaust passage 130. The valves 124 tend to return to their neutral position after each movement. The pressures in the chambers 128 are communicated by pipes 39, 36, 35 and 15 to the piston 27 and the piston-valves 55, 57, 78 respectively, so that operation of the shaft 41 causes alteration of the loading of the parts 27, 55, 57, 78. In the case of all the parts except the piston valve 57 controlling the delivery-valve 31, the alteration of pressure in the chambers 128 is caused to act temporarily only and for this purpose in each of the pipes 15, 36, 39 a device 83, Fig. 5, is fitted. The pressure in each chamber 128 acts through a pipe, the pipe 15, for example, on a piston 85 connected to a piston 87 in a fluid-filled chamber with an open mouth 88 and an outlet 90 to the continuation of the pipe 15. The spaces above and below the piston 87 are in communication through a throttle opening 89, so that movement of the piston 85 causes movement of the piston 87 so as to transmit a pressure impulse along the pipe 15, this impulse dying out as the pressure on the two sides of the piston 87 equalizes due to the opening 89. The hand-control is for use particularly where the generator supplies steam for propelling a vehicle or aircraft and is operated in the event of a rapid variation of load so as to set the regulating devices rapidly to the new load conditions and until the automatic devices come fully into operation.