How to Safely Recover Combustible Dust
When most people think of controlling dust in the workplace, they think of taking steps to avoid inhaling dusts to prevent health problems. However, the accumulation of combustible dusts in the workplace can lead to far greater consequences. As seen in recent years, neglect of housekeeping and improper handling of combustible dusts can lead to property damage, injuries and loss of life.
Any combustible material can burn rapidly when in a finely divided form. If such a dust is suspended in air in the right concentration, under certain conditions, it can become explosive. Even materials that do not burn in larger pieces (such as aluminum or iron), given the proper conditions, can be explosible in dust form.
The force from such an explosion can cause employee deaths, injuries and destruction of entire buildings. For example, three workers were killed in a 2010 titanium dust explosion in West Virginia, and 14 workers were killed in a 2008 sugar dust explosion in Georgia. The U.S. Chemical Safety and Hazard Investigation Board (CSB) identified 281 combustible dust incidents between 1980 and 2005 that led to the deaths of 119 workers; injured 718; and extensively damaged numerous industrial facilities.
What Materials Cause Combustible Dust?
A wide variety of materials that can be explosive in dust form exist in many industries. Examples of these materials include food (e.g., candy, sugar, spice, starch, flour, feed), grain, tobacco, plastics, wood, paper, pulp, rubber, pesticides, pharmaceuticals, dyes, coal, metals (e.g., aluminum, chromium, iron, magnesium and zinc). These materials are used in a wide range of industries and processes, such as agriculture, chemical manufacturing, pharmaceutical production, furniture, textiles, fossil fuel power generation, recycling operations, and metalworking and processing (which includes additive manufacturing and 3D printing).
OSHA estimates that 30,000 U.S. facilities are at risk for a major combustible dust explosion—across all industries. So, the threat of an industrial explosion in your facility is very real. But there are steps you can take right now to protect your people and your facility from combustible dust. If you can eliminate the dust, you can eliminate the explosion hazard. That’s why OSHA recommends—and in some cases requires—manufacturers to use certified, explosion-proof vacuums as part of a regular plant maintenance program when collecting hazardous-classed dust.
The National Fire Protection Association (NFPA) defines a combustible dust as “a combustible particulate solid that presents a fire or deflagration hazard when suspended in air or some other oxidizing medium over a range of concentrations, regardless of particle size or shape.”
In general, combustible particulates having an effective diameter of 420μm or smaller, as determined by passing through a U.S. No. 40 Standard Sieve, are generally considered to be combustible dusts. However, agglomerates of combustible materials that have lengths that are large compared to their diameter (and will not usually pass through a 420μm sieve) can still pose a deflagration hazard. Therefore, any particle that has a surface area-to-volume ratio greater than that of a 420μm diameter sphere should also be considered a combustible dust.
The vast majority of natural and synthetic organic materials, as well as some metals, can form combustible dust. The NFPA’s Industrial Fire Hazards Handbook states, “Any industrial process that reduces a combustible material and some normally non-combustible materials to a finely divided state presents a potential for a serious fire or explosion.”
[Editor’s Note: This article first appeared as a blog on Prestivac’s website. For original article, visit: https://prestivac.com/blog/how-to-safely-recover-combustible-dust .]
Class II Group E metal dusts (aluminum, bronze, chromium, iron carbonyl, magnesium, tantalum, titanium, zinc, zirconium and other commercial alloys)
Class II Group F carbonaceous dusts (carbon black, charcoal, coke, coal, etc.)
Class II Group G combustible dusts (agricultural, calcium, chemical, cocoa, coffee, corn, cotton, egg white, epoxy resin, flour, grain, lactose, malt, melamine, milk, oat, plastic, rice, sodium, spices, starch, sugars, sulfur, tobacco, vinyl, wheat, whey, wood, etc.)
Suggested Industrial Vacuums for Recovery of Toxic & Combustible Dust
Dust Ignition Protected Division 2 Vacuums
Dustless Sanding Vacuums
Explosion Proof Division 1 Vacuums
Immersion Separator Dustless Sanding Vacuums
Which Industries are at Risk with Combustible Dust?
Energy & natural resources
Pulp & paper