GB695863A - Improvements in or relating to protection apparatus for controlling the supply of fuel to furnaces fired by means of liquid or gaseous fuels - Google Patents

Abstract

695,863. Burner control systems. SANDERS (ELECTRONICS), Ltd., W. H. Aug. 30, 1950 [Aug. 31, 1949], No. 22606/49. Class 75(i) A protection apparatus for controlling the fuel supply to furnaces supplied witn gaseous or liquid fuel as claimed in Specification 631,894 has switch means for automatically connecting in continuous succession the flame path gaps of a plurality of furnaces into circuit between the grid of the first thermionic valve and a point at earth potential. Assuming all burners to be alight, the apparatus functions in the following manner, pulses from a pulse generator 11 of known type cause switch arms FS25.1 and FS25.2 of multi-point switches to be rotated by high tension current supplied to a stepping magnet FS.25/2 through contact B1 which is closed by a solenoid B/1 operated on each impulse, one stud (12, 15), at a time being contacted to bring the flame of each burner such as 13D into the grid circuit of a thermionic valve V1 every 6 seconds, a current being thus supplied to an associated relay D/4 to hold contact D1, D2 and D, open and D3 closed, whereby a resistance R1 is held out of circuit, fuel valve of burner 13D is held open and a warning light 16D is out. A manually held switch S2A is open, and switch S2B shut. As current is passing through relay A/2, contacts A1, A2 are open thus disconnecting the arm F.S.25.2 of the rotary switch from earth and a relay K from the pulse generator high tension supply. The relay K/2 not being energized contacts K1, K2 are open and a warning horn 18 is out of circuit from a source 17. Should the burner 13D fail there will be no flame resistance in the grid circuit of V, and hence anode current in V2 will cease to flow, relay A/2 will be de-energized and contact A1, A2 closed, the closing of contact A1 will cause relay D/4 to be by-passed and de-energized to close contacts D1, D2 and D4 and to open contact D3. The closing of contact D1 provides a path to earth parallel to D/4 through a push button P2. Closure of contact D2 brings the resistance R1 into circuit in place of the burner flame resistance to enable the apparatus to function thereafter as though the burner 13D were alight. Closure of contact D4 lights the warning light 16D and the opening of contact D3 operates a solenoid to close the fuel valves of the burner 13D. Closure of contact A2 energizes relay K/2 to close contacts K1, K2 of which contact K1 ensures that when contact A2 again opens K/2 remains energized and K2 to cause the warning horn 18 to operate until a push button P4 is pressed. To relight the burner 13D the push button P2 is pressed to energize the relay D/4 which opens contacts D1, D2 and D4 and closes the contact D3 which opens the fuel supply valve and thus the burner may be ignited in the normal manner. The burner 13D may be kept permanently extinguished by closing the switch S2A and opening the switch S2B to by-pass relay D/4 and to put the lamp 16D out of circuit. Should the pulse generator fail a solenoid I/1 operates a contact I/1 to shut a main fuel supply valve.