Minimum ignition temperature of a dust layer of 5 mm thickness (glowing temperature)

Definition

Lowest temperature of a hot surface on which ignition occurs in a 5 mm thick layer of dust under specified test conditions.

Determination

The glowing temperature is determined on an electrically heated plate 185 mm in diameter, the temperature of which is controlled with an accuracy of +/- 2 °C by thermostats. The sample is spread in a circular shape (100 mm diameter) in a 5 mm thick layer in the centre of the preheated plate and the reaction behaviour observed - sometimes with the aid of a sensitive thermocouple. Signs of glowing phenomena are made clearer, if necessary, by careful fanning. The lowest plate temperature, at which parts of the sample glow within two hours after application, is referred to as glowing temperature. Thicker layers may ignite at markedly lower temperatures.

Remarks

The abbreviation "n.g.u. ..." means: no glowing up to ... °C. The information "melts" means that the substance melts or sinters in such a way that the dust character is lost before a glowing temperature is achieved. 

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