During this investigation, the determination of minimum ignition energy (MIE), by electrical spark in accordance with EN 80079-20-2
The minimum ignition energy (MIE) test measures the ignition of a dust cloud by electrical and electrostatic discharges. Using a spark with controllable energy content, the minimum ignition energy (MIE) of the powder is determined in the MIKE3 device.
The MIE apparatus consists of a borosilicate tube placed over a dispersion cup and fitted with two electrodes. The electrodes are connected to a circuit that produces an electrical spark of known energy. A sample of combustible dust is placed in the dispersion cup, which is blown up through the tube with compressed air past the ignition source.A modified glass Hartman tube (of 1.2l) is used as the explosion vessel. The sample of the dust is freely dispersed in the tube by the built-in dust dispersion system. After which the substance is ignited by a spark between two electrodes. The value of the minimum energy is used to exclude possible initiation source.
If flame propagation is observed, the energy of the spark is reduced until no flame propagation is seen for 10 consecutive tests. At that spark energy, a range of dust sample weights is tried to thoroughly investigate potential dust explosion concentrations. The test result is stated as an energy range, indicating that ignition took place at the higher value and no ignition took place at the lower value. The MIE is a measure of how sensitive an explosive dust cloud is to electrical spark ignition.
Determining the minimum ignition energy is important for determining the energy required to explode a substance. Consider, for example, electrostatic sparks.
Testing for minimum ignition energy gives guidance on whether ignition by electrostatic discharge from personnel or process conditions is likely to occur in practice.
The test is carried out according to EN ISO/IEC 80079-20-2 (Explosive atmospheres Part 20-2: Materialcharacteristics – Combustible dusts test methods).