GB950210A - Improvements in flame failure detection - Google Patents

Abstract

950,210. Controlling burners. ELCONTROL Ltd. Aug. 22, 1962 [June 7, 1961; June 13, 1961; July 4, 1961], Nos. 20637/61, 21232/61 and 24058/61. Heading F4T. [Also in Divisions G4 and H4] An ultrasonic flame detector comprises a transmitter consisting of an ultrasonic generator 1, transducer 2 and emitter tube 3 and a tuned receiver 9 the output of which is filtered and amplified to operate an alarm or recorder. The output from tube 3 is reflected by the flame and transmitted to the receiver, should the flame disappear, there will be no receiver input and relay 12 will be de-energized to operate an alarm and/or shut off the fuel valve. Only one tube 3 or 5 need be used in a system, the same tube also detecting any reflected signal. The flickering of the flame will modulate the carrier and the receiver may include a demodulator to avoid a false alarm due to spurious signals. In another embodiment (Fig. 2) the ultrasonic signals are transmitted through the flame, the mean flame envelope F normally masking the receiver tube. A " fail-safe " system can be provided by using tuned transducers 2, 9 (e.g. magneto-strictive piezo-electric) and feeding back from amplifier 11 to transducer 2 so that the circuit resonates only in the absence of flame; the rise of current being very sharp at this point and actuating the relay 12. The common axis 7, 8 of the receiver and transmitter tubes are offset from the flame axis so that a dangerously low flame is also detected. The system can be applied to a multi-burner installation (Fig. 3, not shown).