GB1369038A - Method and apparatus for determining the explosibility of a gaseous medium - Google Patents

Abstract

1369038 Determining explosibility of gaseous medium electrically INDUSTRILABORATORIET AB 1 Dec 1971 [2 Dec 1970] 55740/71 Heading G1N In order to determine the explosibility of a gaseous medium, the medium is placed in a probe including an ignition igniter and the energy of the igniter is increased until ignition of the medium takes place, the energy or temperature level at which the medium ignites being measured to provide a measurement of the explosibility. In a first arrangement a pulse from a pressure spark gap 7 energized by adjustable high voltage source 1 is applied to a spark gap 13 in probe 6. The energy of the pulses are increased until ignition of the gas being tested takes place as indicated at 6, 12, and the magnitude of the igniting pulse measured by oscilloscope 10 and capacitive voltage divider 11. The probe 6, Figs. 2, 3 (not shown) is in the form of a right circular cylinder provided with apertures spaced circumferentially around the cylinder which are covered by a mesh smaller than the quenching distance of the medium to avoid flash back. The spark gap is defined by two axial electrodes. In Fig. 4 (not shown) a source of γ-rays is provided to promote ionization of the gas in the spark gap and in Figs. 6, 7 (not shown) a fan is provided at the end of the probe which is provided with the mesh covered apertures to promote circulation of the medium through the spark gap. Ignition of the medium may be detected by thermistors inserted in the gas chamber. In a second embodiment, Fig.8, the ignition igniter is a heating or incandescent body 40 instead of the spark gap. The probe 6 in this case has a heating element 40 connected in one arm of a bridge fed by adjustable voltage source 43. The bridge is initially balanced and then the current through 40 increased until ignition occurs, indicated by transducer 49 connected via amplifier 50 to lamp 51, the transducer being a heat-sensitive emitter, pressure or light sensor. The unbalance voltage of the bridge is measured at ignition on instrument 48 which shows the heating element temperature. The probe 6 is similar in construction to that of Fig. 1 except that a strip of resistor material replaces the spark gap electrodes, Figs. 9, 10 (not shown). Instead of a strip of resistor material the heating body 40a, 40b, 40c may comprise a thermo-electric couple, Fig. 12, which is supplied from an alternating-current generator 62 via capacitors 63, 64 the e.m.f. developed in the couple due to its heating being applied to meter 48a via inductors 65, 66 to indicate the temperature of the couple. The generator 62 output is controlled by a rampfunction generator 67 which passes through normally open gate 68. When ignition occurs a signal from transducer 49a closes the gate to stop the heating current from 62. The heating body may be a tube of resistor material Fig. 14 (not shown).