Abstract: Through the statistical analysis of several dust explosion accidents, taking open fire as a common ignition source as the research object, test device was developed to study the characteristics of combustible dust induced by open flame represented by welding flame. Experiments were carried out by using corn starch, lycopodium dust and coal powder as test materials to study the characteristics of igniting combustible dust by open fire. The maximum temperature of corn starch and lycopodium dust in the combustion process were 956 ℃and 855 ℃. The mass concentration of dust ignited by open fire in semi-open space is significantly higher than the LEL measured by 20 L spherical device. Open flame is not easy to ignite the dust, such as coal dust, that is insensitive to temperature ignition source. Therefore, when determining the flammability of dust, open flame could be used as a preliminary screening method and 20 L spherical device is the final method to determine the combustibility of dust.

Key words: open fire, welding flame, dust explosion, explosion characteristics