GB1406678A - Boiler burner balancing-counter control system - Google Patents

Abstract

1406678 Automatic control FORNEY INTERNATIONAL Inc 11 Aug 1972 [11 Aug 1971] 37641/72 Heading G3N [Also in Division F4] A control system for two banks of burners in a furnace comprises electronic summing circuits for providing signals respresentative of the number of burners in operation in each bank, comparator means for comparing the two signals, and control means including logic circuitry for controlling the number of burners in operation, in response to the overall load deinand. In the illustrated embodiment the burners are connected to an adder/ subtractor amplifier 80 which produces an output depending on the difference in the numbers of burners in operation in the two banks, electronic comparator circuits 92, 94 connected to AND gates 110, 114, 116 and 118 producing signal outputs responsive to the difference in the numbers of burners in operation in the two banks, and a control circuit 128 responsive to said output signals for controlling the burners. Each summing circuit comprises flame detectors (16), Fig. 2, (not shown), one for each burner (15), connected to the input circuits of transistor amplifiers, Fig. 4, (not shown) whose output circuits are connected to the differential amplifier 80 and in parallel with each other. This output is fed into the two comparators 92, 94 in which the voltage signal from the amplifier 80 is compared with voltages from a corresponding pair of two series of potentiometers 46, 48, in which each pair corresponds to a given value of the difference in the numbers of burners in operation. The output from the comparator circuits 92, 94 indicates which of the banks has a greater number of burners in operation and is fed, together with signals from a load control circuit 128, which indicates the overall heat demand, into the four AND gates 110, 114, 116 and 118 whose output controls two burner control circuits 142, 146. The control circuits 142, 146 restore the balance in the numbers of burners by lighting some in one bank if more heat is required or extinguishing some in the other bank if less heat is required, by operating valves V10, V10' in fuel-pipes P10, P10'. A D.C. source 20 provides power for all the active circuits and a Zener diode network 26 provides a voltage reference.