MINIMUM IGNITION ENERGY (> 1 J)
If the dust explosibility test in the modified Hartmann-apparatus was NEGATIVE the minimum ignition energy of these type of dusts is then normally determined in a 20-ℓ-Apparatus.
The ignition delay time (turbulence level) in the 20-l-Apparatus is tv = 0,06 s and/or tv = 0,12 s.
By variation of the dust concentration the maximum Pmax and Kmax are determined for different level of ignition energies e.g., IE = 10.000 J, IE = 5.000 J, IE = 2.500 J, IE = 1.000 J, IE = 500 J.
The measured Kmax are plotted versus the used ignition energies.
The minimum ignition energy can then be determined by extrapolating the measured maximum explosion constant as a function of the used ignition energy IE to Kmax = 0 m·[bar·m/s].