We’ve seen the impact they can cause – grain dust explosions sparked when certain conditions come together to create a combustible situation. And those conditions can develop much faster than many know, according to a Kansas State University grain scientist.
“Grain dust explosions still occur under specific handling conditions,” said Kingsly Ambrose, assistant professor in K-State’s Department of Grain Science and Industry, but the likelihood of such occurrences decreases when employees know the risks and know what to do to prevent incidents.
The majority of explosions are linked to dust from corn and more happen in grain elevators than in feed or flour mills, for example, but Ambrose said he did not want to downplay the risks of working with other grains and in other types of facilities.
A total of 100 grain dust explosions occurred over the 10 years 2005-2014 in the United States, resulting in nine fatalities and 96 injuries. Fifty-four involved corn, three involved soybeans and four were linked to wheat. The rest happened in facilities handling barley, oats, beet pulp, rice and others.
Sixty-one of the 100 explosions occurred in grain elevators and 22 in feed mills. Since 1980, however, there has been a decline in explosions, injuries and fatalities at grain handling facilities. The historical data for the period 1976 through 2005 (http://krex.k-state.edu) confirm the downward trends of reduced risk of dust explosions and injury to personnel at grain handling and processing facilities.
It takes just a spark when conditions are right in any grain handling facility to set off an explosion, Ambrose said, and the conditions can change in a matter of minutes. The ingredients common to all explosions are fuel (in this case, dust); ignition (often a spark); confined space; oxygen; and dust clouds.
The dust on the floor of a facility would ignite first, he said, and if there are dust clouds, the explosion can happen. “The pressure and heat from these conditions combined can be just like a bomb,” he said.
He conducts workshops focused on ways to prevent such explosions, funded by the U.S. Department of Labor Occupational Safety and Health Administration.
Ambrose’s work follows up on the work of long-time K-State grain science professor Bob Schoeff, who is now K-State professor emeritus.
Awareness and training
Shane Eck, location manager with Mid Kansas Cooperative’s grain elevator in Lindsborg, Kansas, has not experienced a grain dust explosion and wants to keep it that way. He said MKC routinely trains its employees on proper housekeeping, preventative maintenance, daily inspections, and equipment monitoring.
Also citing the ingredients needed to create a grain dust explosion, Eck said, “We work to eliminate the ingredients within our control. Those are the grain dust and ignition source. It is important to have and follow a good housekeeping program to eliminate the dust. The ignition source of many dust explosions comes from hot bearings or belts rubbing on metal. The grain industry has widely accepted the practice of utilizing monitors to warn us of such conditions. Not all facilities are required to have monitoring equipment so daily leg and equipment inspections are also a good way of identifying potential issues.”
The leg is a continuous belt with hundreds of buckets that elevates the grain to the top of the elevator where it goes into a distributor. The distributor directs the product into the desired bin.
“Most primary explosions occur in the leg,” Eck said. “These explosions are not the ones that do the most damage. The primary explosion suspends dust in other parts of the facility providing the necessary components for additional secondary explosions. A good housekeeping program will prevent secondary explosions.”
“Generally the number of grain dust explosions is going down,” said K-State’s Ambrose, noting that OSHA regulations that went into effect in 1984 helped, as have recommended standards set by the National Fire Protection Association.
In the 45 years from 1958 to 2003, 510 grain dust explosions were reported in the U.S., with an average of 11.3 per year. In the most recent 10 years (2005-2014), 100 explosions were reported for an average of about 10 incidents per year.
Training and new technologies are helping to decrease incidents, Ambrose said. With newer technologies, including explosion-proof panels and explosion suppression instruments, many of these accidents can be avoided. According to OSHA, particles/dust less than 420 microns has the potential to ignite and create an explosion.
Where and when
Most grain explosions happen in the Midwestern states – Iowa, Kansas, Illinois, Nebraska and Minnesota are where most have occurred. That’s where most grain is grown and where the largest concentration of grain handling facilities are located. But they can happen anywhere, Ambrose said.
In the 55-year period 1958-2013, Iowa had the most explosions at 90, followed closely by Kansas at 85, with 80 reported in Illinois, and 78 in Nebraska. Historical data on grain dust explosion incidents in the U.S. is available at the K-State K-REx website (https://krex.k-state.edu/dspace/).
“We tend to see more explosions during harvest season, starting in August to October, depending on the crop,” he added. “We see more explosions at grain elevators than at other grain handling facilities. When you have 1-5 kilograms of dust per metric ton of grain coming into the facilities, that’s where we see a lot more incidences.”
Ambrose said that the tiniest leak in a pipe – even one that can barely be seen – can let enough grain dust escape to form a dust cloud and create the makings of an explosion. Just a minor spark in such conditions can be enough to ignite the dust.
“Conditions in any facility can change in a matter of minutes,” he said.
More information about grain dust explosions is available on an OSHA fact sheet at https://www.osha.gov/OshDoc/data_General_Facts/OSHAcombustibledust.pdf.