Combustible Dust Hazards in Welding

Combustible dust is a metallic or non-metallic material composed of distinct particulate that presents a fire or explosion hazard when met with air, or other oxidizing mediums, over a variety of concentrations.

Combustible dust is generated when materials are being transported, handled, processed, shaped, or polished, and during cutting, sifting, mixing, and abrasive blasting applications.

Dust that is contained inside of processing equipment or ventilation systems can deposit into ducts and become concentrated in collection systems such as baghouses. Equipment that is used to store, collect or, handle combustible dust requires specific design features to reduce the risk of dexplosion.

Welding, cutting, and other hot work processes are the cause of many workplace dust explosions. Combustible dust trails on surfaces can act as a fuse to serve as a source of ignition in other areas.

Facilities at risk of a fire or combustible dust explosion can reduce risks by following the NFPA’s recommended guidelines. To prevent combustible dust from escaping into the work environment, central dust collectors and wet downdraft tables are required to control contaminants. Dust control equipment must be designed to prevent dust explosion and deflagration hazards.

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Fire Triangle

Fire Triangle

Dust Explosion Pentagon

Not all dust is combustible. Dust will vary in the potential for combustion and how severe airborne dust deflagrations might be. However, materials which can burn or corrode in contact with oxygen can form combustible dusts. These reactive materials include:

Metals	Grains
Plastics	Wood
Coal	Paper
And other carbonaceous materials	And other organic compounds: • additives • Solid food products • Pharmaceuticals

For a dust deflagration to occur, a large and dense cloud of dust needs to become airborne at one time and make contact with an energy source that is strong enough to cause ignition. To understand how dense a dust cloud is and what type of energy sources are required to create an ignition hazard can only be learned through specialized lab testing.

For certain dust, a static spark is enough to ignite a dense cloud vs. others that may require an open flame or contact with a hot surface. A small explosion or shock can stir up settled dust into the air creating a big cloud that is often ignited by the heat of the first explosion. It's important to note that finer dust particles become airborne and ignite more easily.

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Preventing Combustible Dust Hazards

When it comes to preventing combustible dust hazards there are many things you can do to eliminate the risks. Understanding the materials that are present in your work environment or finding out what they are if you are unsure will help determine what type of extraction system will be most efficient for your application. It's important to remember not to use compressed air when cleaning powder materials and dust.

Welding and other hot work processes should never take place where combustible dust is present on surfaces or in areas where combustible dust may become airborne. Check adjacent and concealed spaces for dust. Consult a supervisor or safety professional if you are unsure about the risks or safety requirements.

Wet downdraft tables and central dust collectors can be implemented in industrial facilities to establish safety for your staff. Do not work on any equipment that handles or collects combustible dust unless you have received the proper training and are authorized to do so.

Always be extra careful about electrical safety, including static charge build-up, and be sure to follow all safety procedures, hot work precautions, and any other safety rules to prevent dust explosions.

To determine what explosive dust collection system is best for your application, get in touch with our specialists for your customized quote!

Resource: Combustible Dust Hazards in The Welding and Cutting Environment