Minimunm Ignition Energy (MIE)

Definition:

The minimum ignition energy (MZE) is the smallest electrical power stored in a condenser, which sufficiently ignites an ignitable mixture of a combustible atmosphere by an electrical discharge. The MIE is determined under prescribed test conditions.

Testing Method:

according to BG Chemie R 003 6/2000

• Test facility:
  • modified Hartmann-tube
  • Ignition source: spark discharge with variable ignition source
  • Igniton energy normally till 1 J
  • Installation of an inductance: temporal stretch of the sparks, thereby higher ignition effectiveness

Under variation of the apparatus parameters (Ignition Energy, firing delay time, evtl. temperature) and the dust concentration the lowest spark energy ignited sufficiently a dust/air mixture  and the highest spark energy which does not lit a dust/air mixture.

Further information see also Fire and Explosion Protection. A description of the testing method (german version) you can download here.

Safety-relevant meaning:

Usually the MIE of inflammable types of dust is 2-3 powers of ten higher than the MZE for gases and steams. The MZE depends on the refinement, the surface condition and the dampness of the dust.

Generally the MZE decreases with increasing temperature and diminishing particle size (® drying processes!!).

A classification of the inflammability can be taken from the following table.