Patent GB-375815-A (GB)
Abstract: 375,815. Regulating combustion in boiler furnaces. SANDISON, A. G. S., Kelda, Baltasound, Shetland, and INDUSTRIAL COMBUSTION ENGINEERS, Ltd., Cecil Chambers, Strand, London. Feb. 27, 1931, No. 6174. [Class 51 (i).] In a boiler plant in Which each boiler is provided with one or more electric control circuits for varying the fuel and air supply, a master control varies the voltage applied to the control circuits in accordance with the steam pressure, while the fuel and air are regulated automatically in accordance with the current in the control circuits which are provided with current responsive devices. As shown in Fig. 1, the steam pressure in the main 1 operates through a Bourdon tube 3, or other pressure responsive device, a lever 4 connected to relay mechanism 8, which may be of the kind described in Specification 377,674, [Group XXXV], operating an induction regulator 9 connected to A.C. supply mains 10 and having its output main connectedwith a solenoid 6 the core of which opposes the movement of the lever 4. The output voltage of the induction regulator 9 is impressed on the control circuits of each boiler through switches 12. The control circuit for one boiler is illustrated and comprises an ammeter 14, variable impedance 15, solenoid 16, ammeter 17 and solenoid 18, the ammeter 17 and solenoid 18 being shunted by the variable impedance 19. The solenoid 16 is adapted to operate the flue damper 30 of the boiler 2 through the core 20, lever 21 and relay 29, the lever 21 being connected to oil-sealed bells 22, 23 exposed to the pressure of the gases at the points 26, 27 of the boiler and serving to oppose the force exerted by the solenoid. The solenoid 18 operates through a lever 32 and relay 40 a rheostat 38 to control the speed of the stoker 36, the force exerted by the solenoid being opposed by the suction of a tachometer fan 35 on an oil-sealed bell 33 supported on the lever 32. The forced draught damper 47 is controlled by a counterweighted lever 41 provided with an oil-sealed bell 43 exposed to furnace pressure. The impedance 19 may be adjusted to vary the ratio of the fuel and air supply either by hand or automatically by an efficiency instrument of any well-known type. Figs. 2 and 3 show apparatus for operating the impedance 19 automatically comprising a spindle 52 for varying the impedance on which spindle is mounted a ratchet wheel 51 operated by pawls 53, 58 connected to the cores 55, 60 of solenoids 56, 61 connected to contact strips 63, 64 and to the main 69 while the contact strips 65, 66 are connected to the main 67. A suspended rod 70 operated by an air flow meter is provided with contacts 73, 74 adapted to bridge the strips 63, 65 and 66, 64 respectively and in front of the rod 70 is a suspended rod 77 operated by a steam flow meter and capable of engaging with the contacts 73, 74 upon being depressed and when the steam and air flow are not in the desired ratio. Cam shafts 83, 84 intermittently operate switches 82, 68 to energize the solenoid 81 to operate the armature 79 and rod 78 and depress the rod 77 and also to energize the solenoids 56, 61. Should the ratio of steam flow to air flow depart from the normal one or other of the contacts 73, 74 is pressed against its corresponding contact strips and the corresponding solenoid 56 or 61 is energized to operate the pawl and ratchet gear to turn the spindle 52 and vary the impedance 19. The various control circuits may be connected directly to the mains 10 instead of through the induction regulator 9.