The purpose of this article is to answer the following questions in order to understand the explosion hazards presented by combustible dust in the premises: -
• What is Combustible Dust?
• What is Combustible Dust Explosion?
• How Does Combustible Dust Explosion Occur?
• What is Dust Explosion Pentagon?
• Where May Combustible Dust Explosion Occur?
• How to Prevent Combustible Dust Explosion?
• Protection Measures against Combustible Dust Explosion
What is Combustible Dust?
Combustible dust is the fine particle form of a material that may present explosion hazards when suspended in air. It is not necessary that the
What is Combustible Dust Explosion?
Combustible dust explosion is the ignition of fine dust particles of a material generally in a confined space due to spark, static electricity, direct heat source, hot surface or any other source of ignition. This rapid combustion is also known as deflagration.
Since the surface area of the dusts is larger than the material, it is easy for the dusts to ignite than they would as material. Since burning occurs at the surface area the dusts become more prone to fire and explosion than the material itself.
How Does Dust Explosion Occur?
Dust explosion occurs when there is a combustible dust cloud that generates because of process or storage and handling practices. This combustible dust cloud has all the capability to ignite yet in the absence of a source of ignition it can’t.
When there is a source of ignition, the combustion occurs very fast (generation of explosion wave) owing to the large surface area of the material often resulting into complete combustion of the material. Conditions required for dust explosion are often denoted by Dust Explosion Pentagon.
The explosion wave generated will find ways to get out of the confined space or it will increase the pressure of the area where it is generated. Generally such areas are machinery enclosures, vessels, rooms etc.
What is Dust Explosion Pentagon?
Dust explosion pentagon comprises five arms that are required for a combustible dust explosion to occur. In the absence of
• Combustible dust
• Oxygen or Oxidation
• Source of Ignition
• Dispersion of particles
Where may Combustible Dust Explosion Occur?
Where the requirements of the dust explosion pentagon are met, combustible dust explosion may occur. Combustible dust explosions are generally recorded at coal storage areas, food industries, wood industries, pharmaceutical industries, sugar industries, chemical industries, grain industries, metal processing industries etc.
How to Prevent Combustible Dust Explosion?
Basic theory behind the prevention of combustible dust explosion is to prevent the dust explosion pentagon from completing. If this is done dust explosion won’t occur. Following steps may be taken in order to prevent dust explosion from occurring: -
• Analysis of the material handling procedures processes and storage practices
• Inspection schedule and preventive maintenance program to prevent accumulation of dust
• Appropriate installation and routine inspection of electrical fittings
• Installation of dust collectors and filters
• Cleaning schedules and housekeeping policies to avoid accumulation of dust
• In the presence of sources of ignition, methods other than those that generate dust may be followed
• Restrict smoking, sparks and other sources of ignition in such areas
• Separating hot surfaces and heating systems from dusts
• Measures to avoid accumulation of dust where relief valves are located
Protective Measures against Combustible Dust Explosion
If despite the preventive measures a dust explosion occurs there must be some measures to minimize the probable losses. Following are the protection measures that may be taken in order to minimize losses in case of dust explosion: -
• Explosion Venting
• Explosion Suppression System
• Explosion containment