Patent GB-685094-A (GB)
Title: Improvements in or relating to stokers for stoker-fired boilers, and hydraulic systems therefor
IPC: F23K3/16
Filed: 1951-02-27
Abstract: 685,094. Furnace control apparatus. SHEPHERD, G. R. (Westinghouse Electric International Co.). Feb. 27, 1951, No. 4736/51. Class 51 (i) [Also in Group XXIX] In a hydraulicallydriven fuelfeeding device for a stoker - fired boiler in which pressure oil is supplied at a fixed rate to act as a driving medium, some of the oil is bypassed by means responsive to boiler gas flow whereby the amount of fuel delivered is variable to maintain the fuel-air ratio. The invention is shown applied to a furnace wherein the fuel passes from a feeding device 22, Fig. 1, on to a rotary distributer 23, and thence to moving grates 24. Dumping grates 25 are also provided. The operation of an air blower 15 is controlled by a pressure pick-off 19 to maintain a constant negative pressure in the furnace. A secondary air damper 18a and stack damper 18 are controlled by the pressure in the steam header 16 through a master regulator 17. The feeding device, the rotary distributer, and the grates are driven by oil motors 26, 27, 28, Fig. 3, respectively. Oil from a pump 29 giving a constant flow rate passes to a valve 31 which splits the flow into two flows in a fixed ratio, one flow being fed past a manual control valve 45 to drive motor 27,. and the other, to a second valve 34 similar to valve 31. The two flows from this latter valve are in a fixed ratio, and one is fed to the motor 28 whilst the other flows through a controller 105 to motor 26. A manually-actuated change-over valve 46 determines whether this latter flow passes through a line with a manuallyactuated control valve 45a or an automatically-controlled circuit 47. Proportioning valves 31, 34 each comprise a housing with an inlet 38, Fig. 5, and outlets 39, 40 communicating with the inlet passage through ports 42, 43, respectively. The ports are obturated by the top and bottom edges of a spring-loaded piston 44, and whereas the flow to outlet 39 is direct from the inlet through port 42, the flow to outlet 40 passes through an aperture 45 in the piston. Valves 45, 45a each comprise a manually-actuated rotary regulating cock 52, Fig. 9, in the flow line and an inverted-cup lift valve 55 upstream of the cock 52 and controlling the by-pass of oil from the flow line. Valve 55 can slide up- and-down between fingers 65 on a valve seat-carrying inset 63, and it is loaded through a tappet 56 by a spring-pressed piston 57 and the oil pressure downstream of cock 52 acting on the piston 57. In the automatic control of the oil flow to motor 26, the flow of gas in the furnace is measured by taking the pressures at two spaced points in the furnace and applying these pressures to the opposite sides of a diaphragm 71, Fig. 7. The latter actuates a valve 83 venting a line 85 supplied with oil from the main flow line 47 to the motor 26 past a restriction 86, so that the pressure in line 85 corresponds with the gas flow in the furnace. This control pressure is applied to a diaphragm 95 which actuates a valve 93 venting oil from the line 47. The fuel-air ratio of the furnace is set by a manually-variable restriction 88 in the line 47, and the pressure downstream of this restriction is applied to a piston 99 connected to valve 93.