Patent GB-759711-A (GB)
Title: Control systems for burner apparatus for heating steam generators
Inventor: GARRAWAY GEORGE H
IPC: F23D11/00
Filed: 1953-12-28
Abstract: 759,711. Burner apparatus. ORR & SEMBOWER, Inc. Dec. 28, 1953, No. 35981/53. Class 75(1). [Also in Groups XXIX and XXXV] A steam generating unit includes a control system for modulating the combustion rate of a burner for firing a furnace for heating a boiler, and said control system comprises means responsive to variations in steam pressure to control directly both the fuel and air supplies -to the burner apparatus to provide the fuel air ratio required for optimum combustion conditions throughout the full firing range of the burner apparatus. The steam pressure responsive means preferably comprises a control element having a mechanical linkage to both the fuel and air supply valves regulating the burner combustion. The burner 22, Fig. 5, which is similar to that described in Specification 717,340, is adapted to burn either liquid or gaseous fuel, and comprises an oil sprayer 112 nounted coaxially within a gas burner tube 104. Combustion air is supplied by a blower (not shown) through a duct 100 containing a control damper 160 and leading tangentially into an air chamber 92 surrounding the burner from which the air passes through an annular port 96 into the combustion tube 46. The damper 160 is adjusted conjointly with oil and gas valves 122, 138 respectively, which are simultaneously adjustable, although only one is supplied with fuel at a time, each fuel supply being further controlled by a separate solenoid operated cutoff valve. The valves 122, 138 are actuated by cams 132, 156 respectively, driven by a reversible motor 136 MD in Fig. 8B, controlled in response to variations in the pressure of steam generated. The gas valve 138 has a valve element 140, Fig. 3, biased downwardly by a spring 150 to a minimum gas flow position determined by an adjustable stop 154 or a valve stem 142 carrying a cam follower roller 143 which is lifted by the cam 156 to raise the valve element 140 to increase the gas flow. The cam 156 has a variable profile defined by the outer ends of members 171 screw-threaded into the cam periphery, and its movement is transmitted to the damper 160 through a linkage comprising a rod 168 connected by an adjustable pin and slot connection to an arm 164 fixed to the rotary shaft 162 carrying the damper 160. The cam 132 is constructed similarly to the cam 156, and the oil valve 22 is of a construction described in Specification 744,747. The burner operation is controlled by an electrical system illustrated in part in Fig. 8B. If the burner is required to be oil fired a control switch SBC is set to "oil" to complete the primary circuit of a transformer T3 to energize a relay RL-1 in the secondary circuit. Relay contacts RL1-1, -3, and -4 are then closed and contacts RL1-2 opened to start a time switch motor M, and energize motor starter relay MSB to start the combustion air blower to purge the burner and combustion space. After a pre-determined purge period the motor M closes contacts K2-1 and K1-2 to energize a gas pilot solenoid valve SVGP and an ignition transformer TI, provided that contacts PCA have been closed by the combustion air pressure, and that the water level in the boiler of the steam generator is sufficiently high to close safety control contacts RWC. A pilot burner is then ignited and a flame detector CCS responds to the pilot flame to cause an electronic circuit EC to energize a relay RL2, closing contacts RL2-2, -3, and -4, and opening contacts RL2-1. After a pre-set period contacts K1-3 are closed and contacts K1-2 and K1-1 are opened by the timing motor M thus energizing the main oil solenoid valve SVMO through the closed contacts MSA, SBC, K1-3, RL2-3 and RL1-4. Flow of fuel through the valve SVMO is thus only permitted provided that the contacts RL2-3 are closed by the flame detector CCS in response to a flame at the pilot burner. Contacts K2-1 are now opened to de-energize the ignition transformer TI and gas pilot solenoid valve SVGP. After a pre-set period the timing motor M opens contacts K4-1 and K3-1 and closes contacts K4-2 and K3-2, thus stopping the motor M. During burner operation a movement of the arm of a variable resistor PCM in response to a variation in steam pressure unbalances the energizing circuit of the electric motor MD so that the latter becomes energized and adjusts the oil valve 122 and the combustion air control damper 160. Movement of the damper 160 is transmitted by linkage to a potentiometer PMD to balance the circuit and stop the motor MD when the damper 160 is adjusted. In the event of flame failure the electronic circuit controlled by the flame detector CCS deenergizes the relays RL2 and RL1, and thus also the main oil solenoid valve SVMO, and closes contacts RL3-2 to energize an alarm circuit. Specifications 717,340 and 759,717 [Group XIII], also are referred to.