Industrial technologies are characterized by hot surfaces, these can be furnaces, burners, and dryers operating normally, but local hot surfaces can also occur as a result of mechanical or electrical malfunctions. Hot surfaces can be a source of ignition in a potentially explosive environment (e.g. stuck bearings, overloaded electric motors).

The minimum ignition temperature - Minimum Ignition Temperature (MIT) - is the lowest surface temperature that can ignite the dust cloud in the mixture most prone to ignition, relative to the suspended state of the dust sample. The ignition temperature of powders can be determined with a BAM furnace or a Godbert-Greenwald furnace.

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The two test principles are very similar. The two methods only differ in that, while the GG furnace space is vertical, the BAM furnace space is horizontal. During the test, the powder prepared in the sample holder is delivered to the furnace space with pressurized air. When testing, we look for the ignition temperature of the mixture most prone to ignition, so the measurement parameters vary widely. The excess pressure of the air tank can be selected between 10-50 kPa (typically 10 kPa, 20 kPa, 30 kPa, 40 kPa, 50 kPa), the amount of the sample ranges from 0.05g to 0.5g (typically 0.05g; 0.1g; 0.2g; 0.3g; 0.4g; 0.5g). Combinations of measurement parameters are tested at each measurement temperature. If the powder ignites, i.e. the temperature of the furnace exceeds the ignition point of the powder sample, a flame phenomenon is experienced at the bottom of the tube furnace. After ignition, the wall temperature of the furnace must be reduced and the measurement must be repeated until the highest temperature is found at which none of the 10 repeated tests of the mixture most prone to combustion results in a flame phenomenon. The ignition temperature of the sample measured in the floating state is obtained by subtracting 20°C above 300°C and 10°C below 300°C from the lowest temperature step where ignition occurred. The results of the test are relevant up to 600°C from an explosion protection point of view, but we can perform the test up to 1000°C if required.

With the GG or BAM furnace, the explosiveness of the powder sample can be verified if the powder ignites during the test. However, the reverse is not true, i.e. it is possible that the ignition temperature of a given powder is higher than the measurement limit of the measuring device and although no ignition phenomenon can be experienced in the furnace, the powder is still explosive.