Ignition properties of mechanical sparks and hot surfaces in dust/air mixtures



Up to now it was believed that mechanically generated sparks caused most of the dust explosions in industry. Such belief was not confirmed through extensive testing involving combustible dust and selected flammable gases. The steel grinding, friction and impact sparks were capable of igniting fuel/air mixtures under certain conditions. However, from additional tests it was found that hot surfaces which are generated by rubbing steel against steel are capable of easily starting dust explosions independent of the ignition behavior of the fuels.