COMBUSTIBLE DUSTS

THE HAZARD OF ANY GIVEN DUST (COMBUSTIBLE MATERIALS AND FINELY DIVIDED METALS) IS RELATED TO ITS EASE OF IGNITION AND ENSUING EXPLOSION.

FIRE HAZARDS OF DUST

• LARGE DEPOSITS OF DUSTS PROVIDE A MEANS FOR FIRE TO SPREAD RAPIDLY.  THEY MAY ALSO ACT AS THERMAL INSULATION OF HEAT PRODUCING EQUIPMENT.
• THE CHANCE OF DUST IGNITING IS GOVERNED BY THE SIZE OF THE PARTICLES, DUST CONCENTRATION, AND IMPURITIES PRESENT, OXYGEN CONCENTRATION, AND THE STRENGTH OF THE SOURCE OF IGNITION.
• THE SMALLER THE PARTICLE OF DUST, THE EASIER TO IGNITE.
• CONCENTRATION - THE MINIMUM CONCENTRATION OF DUST BELOW WHICH PROPAGATING IGNITION WILL NOT OCCUR, IS KNOWN AS THE LOWER EXPLOSIVE LIMIT (LEL).

EXPLOSIONS INVOLVING DUST

• DUST EXPLOSIONS RESULT FROM DEFLAGRATION OR DETONATION.
• DEFLAGRATION - TO BURN OR CAUSE TO BURN WITH GREAT HEAT AND INTENSE LIGHT.
  COMBUSTION TRAVELS AT LESS THAN THE SPEED OF SOUND.
• DETONATION - COMBUSTION TRAVELS AT OR ABOVE THE SPEED OF SOUND.
• DUST EXPLOSIONS USUALLY OCCUR AS A SERIES.
• SMALL DEFLAGRATION - JARS DUST - SECONDARY LARGER EXPLOSION…..

This is a video example of dust explosions.

       
INDEX Heat

FPT 102 - Fire Prevention and Inspection // Instructor: Kevin M. Kolb        Slide #1