Page 18 - Occupational Health & Safety, January/February 2020

COMBUSTIBLE DUST
The Finer Points of Combustible Dust Compliance Requirements
Companies that don’t recognize the risks of combustible dust and fail to mitigate them are quite literally playing with fire. BY STEPHEN WATKINS
If you’re involved in any kind of industrial pro- cessing, then by now you should be familiar with NFPA 652, the National Fire Protection Associa- tion’s Standard on the Fundamentals of Combus-
tible Dust.1 First issued in 2016 and updated for 2019, NFPA 652 sets the requirements used by OSHA and other authorities having jurisdiction (AHJs) to deter- mine if companies are doing what they need to do to keep their workers safe from combustible dust hazards.
Judging by the 2019 Mid-Year Combustible Dust Incident Report, many companies still haven’t taken the required compliance steps.2 Between January and July of this year in the United States and Canada alone, there were 92 fires and 20 explosions, result- ing in 36 injuries and one fatality. At least four of the incidents resulted in losses of more than $1 million. Keep in mind that these are only the incidents that were reported in publicly-available sources, like news outlets. The real number is undoubtedly much higher.
Almost any dust except regular dirt can be com- bustible under the right conditions, and every small fire has the potential to become a catastrophe. Com- panies that don’t recognize these risks and fail to miti- gate them are quite literally playing with fire.
Many articles in this publication have addressed
the broad strokes of NFPA requirements. In this article, we’ll dig into some specific issues that give rise to the most common questions when perform- ing cleaning compliance assessments at industrial processing facilities.
When to Use Historical or Published Data to Determine Dust Combustibility or Explosibility The first thing facilities need to do is to determine whether their dust is combustible or explosible. This is required even if you’ve never had a combustible dust incident.
NFPA 652 provides two methods for evaluating your dust:
■ Using historical facility data or published data that are deemed to be representative of current mate- rials and process conditions
■ Using analysis of representative samples, i.e., dust testing
Obviously, the first option here is the easiest. There is published data on just about every type of material used in processing facilities (see NFPA 652, Appendix A). The trick is that the available data may not be “representative of current materials and pro- cess conditions.”
In a recent webinar on combustible dust compli- ance, Nilfisk’s director of engineering, Norman No- wosinski, gave the example of spice mixes.3 A com- pany might have historical or published data on each spice (e.g., salt, pepper, garlic powder) that goes into a mix. But the properties of the mixture dust will be dif- ferent from the properties of the individual ingredient dust, so each mixture still needs to be tested.
The bottom line is that you can use historical or published data as long as you can prove that the properties of your dust are the same as the previously tested dust. If they aren’t the same, you’ll need to take the testing route.
The 1/32” Criterion for Dust Accumulation
You may have heard about the 1/32” requirement, aka the paper clip test. This is the idea that dust should not be allowed to accumulate more than 1/32”, or roughly the thickness of a paper clip. Another way of thinking about this is that if there’s so much dust that you can’t see the color of the underlying surface, you should clean immediately.
This is a useful rule of thumb, and cleaning when- ever you see more than 1/32” of dust certainly isn’t a bad idea. But it’s also not the complete story.
14 Occupational Health & Safety | JANUARY/FEBRUARY 2020
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