To celebrate the fourth year of the Dust Safety Science podcast, we’re doing a couple of solo episodes about combustible dust loss history.
There’s a saying that goes along the lines of “If we could just remember what we forgot, we would improve safety insurmountably.” Unfortunately, we’re forgetting more than we actually learn in most instances, which is why the same losses occur time and again. For this reason, we want to dive into the history books and see where we’ve been so we can better understand and control where we’re going.
There are myths that we’re going to tackle in the next couple of episodes. One is that combustible dust is a new problem. It didn’t start with the Imperial Sugar Refinery Explosion. Dust explosions and fires have been happening across the globe for hundreds of years.
When Did Dust Explosions Become an Issue?
The earliest dust explosion reports date back to the 1700s. In North America, one of the earliest and most comprehensive references was published in 1922. Titled “Dust Explosions: Theory and Nature of, Phenomena, Causes and Methods of Prevention,” it was written by David J. Price, the engineer in charge of dust explosion investigations for the Bureau of Chemistry at the U.S. Department of Agriculture, and published by the National Fire Protection Association, or NFPA, back at the time.
The preface reads as follows:
“The subject of dust explosions has not received serious consideration until recent years. In fact, no one seemed to have any conception that dust alone could explode. But the fact that a large number of explosions have been occurring in mines and industrial plants where no explosive gases were present has proved the idea to be false and has led to the study of this particular hazard.
“The loss of life and property, which many of these explosions have entailed, has increased the demand for comprehensive and authoritative publication on the subject. Attempting to meet this demand, the authors desire to give the facts as they have been found by investigation, and in such a way they can be easily understood and applied.”
Coal mining incidents were the first indicators that dust alone could explode: people couldn’t justify a large mine exploding due to methane gas build-up alone, so organizations like the U.S. Bureau of Mines looked at dust explosions. Then the U.S. Department of Agriculture began investigating grain-related explosions, which is how Price and his co-author H.H. Brown got into the Bureau of Chemistry.
The third and fourth paragraphs of the preface state:
“It is safe to state the explosions are known to have occurred in flour mills, feed mills, grain elevators, starch and all grain handling plants, sugar, candy, chocolate malt, spice, linseed meal, cottonseed meal, paper, cork and linoleum, woodworking and sulphur factories, and in coal mines. In fact, all industrial plants in which dust is produced in the handling of a carbonaceous material or the manufacture of various products from this material are subject to the possibility of an explosion. Some idea of the extent of the industries affected and the amount of property involved may be obtained from the Census Reports for 1919. These show that more than 21,000 establishments are manufacturing or creating dusts of an explosive nature and that the valuation of product is more than 6.7 billion dollars.
“In approaching the subject, it has seemed well to consider what a dust explosion really is, and the different factors which affect its nature or behaviour, what explosions have done and what has been learned, and studying those which have occurred in various industries. And then to discuss the measures which have proved most effective in preventing an explosion, or in retarding its development once it started. It is the sincere desire of the authors in bringing this matter to the attention of the public in this way, that many explosions may be prevented, and that thereby many lives and much property may be saved.”
The table of contents is eerily similar to many of the guidebooks published today:
- Chapter 1 covers the nature and theory of dust explosions and compares them to gas explosions.
- Chapter 2 talks about the industries producing combustible dust and identifies the points at which dust is produced: handling the material, choke-ups, dry equipment, cleaning a material, grinding, separation, storage.
- Chapter 3 is about the causes of explosions and sources of ignition. They talk about smoking, electro-causes, small-scale fire sparks from foreign material and static electricity: all things that are relevant today.
The next couple of chapters address prevention of explosions by control of explosive mixtures, decreasing the percentage of oxygen and air and preventing explosive dust and air mixtures by keeping things below the minimum dust concentration. They talk about isolation and prevention of explosion propagation. There’s an entire chapter on dust collection removal – why it’s needed, the hazards that arise from dust collection, the use of compressed air, and the inefficiency of the broom push method for cleaning. One chapter is devoted to static electricity while others review factors like plant construction.
The Standard Development Process for Combustible Dust
NFPA 652 is not the first standard for combustible dust. In 1924, the 28th Committee on Dust Explosion Hazards was held by the National Fire Protection Association in 1924. One of its outcomes was the regulations for the pulverizing systems for sugar and cocoa.
These regulations and others like them became the earliest combustible NFPA dust standards. They go over modern concerns like housekeeping, containment, keeping the dust inside the processing vessel and not having any accumulations outside.
Conclusion
All of these issues discussed during the 1920 are combustible dust challenges that we’re dealing with today. Hopefully, with the global information exchange made available by modern technology, lessons learned will yield tangible results.
If you have questions about the contents of this or any other podcast episode, you can go to our ‘Questions from the Community’ page and submit a text message or video recording. We will then bring someone on to answer these questions in a future episode.
Resources mentioned
Dust Safety Science
Combustible Dust Incident Database
Dust Safety Science Podcast
Questions from the Community
Dust Safety Academy
Dust Safety Professionals
Organizations
NFPA
Incidents
Imperial Sugar Refinery Explosion
Standards
NFPA 652
Publications
Price, David J. Dust Explosions: Theory and Nature of, Phenomena, Causes and Methods of Prevention
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