Agricultural engineers develop system to prevent combine fires
"What a nightmare," blogs one North Dakota sunflower farmer, describing fires smoldering in combine engine and ladder compartments, under the rotor belt and in front of the radiator.
"And the harvesters have 800 acres to go," he laments. This scenario illustrates the challenges sunflower producers face during harvest.
"Sunflower producers have known for a long time that they had a more severe risk of fire than producers of corn, soybeans or wheat," says professor Dan Humburg of the agricultural and biosystems engineering department.
In the fall of 2011, a team of SDSU agricultural engineers set out to analyze the problem and figure out how to prevent the fires through funding from the South Dakota Oilseeds Council.
"It's not if they have a fire, but when," adds Kevin Dalsted, who coordinated data-gathering and input from area producers and assisted with technical and design work.
Through this project, the engineering team has designed a device which when fitted onto a combine, drastically reduces and may even eliminate these fires.
Protecting machines with vigilance
In the 2011 harvest season, agriculture engineering instructor Nicholas Uilk gathered data from fire departments in eastern South Dakota, southwestern Minnesota and northwestern Iowa. Warm temperatures, exceptionally dry crop conditions, low humidity and high winds created conditions conducive to fires during a three-day period in October 2011. In northwestern Iowa, 100 combine fires occurred within a 10-county area during this time span.
"And those people were harvesting soybeans," he adds, estimating the cost of a replacing a combine at $300,000, without the heads and other needed accessories.
Though fires do occur with soybeans, Humburg says, "it not endemic like in sunflowers. Some producers won't grow sunflowers because they don't want to put their combines at risk."
For those who do, harvesting requires constant vigilance.
"Most farmers keep a truck at the end of the field with a water tank to put out a catastrophic fire," Humburg explains. On the combine, they typically carry water to extinguish small smoldering areas.
One sunflower grower in central South Dakota told Humburg he has become attuned to the odor just before a fire ignites.
"He's so sensitive to it that he knows exactly what to smell for to be on guard," Humburg explains. This exemplifies "the tension they're under all the time."
Finding the source of fires
Graduate student Joseph Polin and assistant professor Zhengrong "Jimmy" Gu investigated which parts of the plant ignite and at what temperature. The researchers ground the outer shells of the stem, the plate-shaped head and the white pith in the center of the stem, and then compared their chemical properties to those of the dust gathered from combines.
A large part of what was sticking to the combine was the white pith, Humburg explains.
It breaks down and is drawn into the fan that pulls air through the radiator to cool the engine.
"A portion of this dust ignites when it hits the turbocharger and exhaust system," Humburg says. "Every once in a while one of those embers lives long enough to land on a surface covered with the same stuff."
Anecdotal information from the producers supported this scenario. Farmers were finding scattered, smoldering fires on the side of the combine downstream from the radiator blast, especially under windy conditions.
"Once a fire starts, it's easy for a spark to be relocated," Humburg explains. Many machine components including fiberglass shields, wiring harnesses, flexible hoses and plastic fuel tanks can burn.
"Dust doesn't have to sit on a hot component; just coming close ignites some of the material when the machine is operating under heavy load conditions," he says. Polin and Gu found that sunflower debris ignites at temperatures that are 68 to 86 degrees Fahrenheit lower than those for corn or soybean residue.
Producers report being able to find a threshold above which they will experience fires immediately, Humburg explains. They monitor fuel usage and rated engine load to pinpoint this threshold each year.
"If they push engines beyond this threshold, they have a higher likelihood of a fire," Humburg says. A greater engine load will increase the exhaust system's temperature.
Designing preventive measures
By the 2012 harvest season, the agricultural engineers had developed a prototype system that uses a fan to pull outside air through a filter. The clean air is pushed through a duct into an enclosure surrounding the turbocharger and exhaust manifold.
"This clean air enters the same hot environment, but it but contains no dust to ignite," Humburg notes. Additionally, the outside of the patent-pending system easily stays within a safe temperature range.
Humburg credits producer Scott Foth for "contributing much to our understanding of the problem."
The Onida farmer used the research team's prototype on his Case IH 8120 combine during the 2012 harvest. He tested an updated version last fall.
"I've been fighting these fires for years," Foth says. "I've experimented with many things that helped, but nothing really solved the problem completely. If we can get through this season without a fire caused by the exhaust, I will be totally convinced that this is the answer so many farmers have been looking for."
Last year when a seal went out on the prototype system, he reports, "we had a fire every day while the device was not operating." Since then, Foth has experienced only one fire, which he speculates may have been caused by a bearing failure.
"Being able to go full speed and use all the capacity of the combine to get the crop in is a huge relief," says Foth.
The expertise and passion of the SDSU team produced results that Brad Bonhorst, former president of the Oilseeds Council, describes as having "great potential to solve the problem."
"This was one of the best uses of checkoff dollars that I've ever seen," he says.
"Those fellas took a relatively small amount of money and came up with some really impressive results."
In 2013, the National Sunflower Association took over funding the project. "That doesn't happen very often," Bonhorst explains. The increase in funding allowed the researchers to expand the project to two more operations—another Onida farmer who has a John Deere 9770 combine and one in Hazen, N.D, who owns a Case IH 8230.
"All three models have different exhaust sizes and configurations," Humburg explains, so the fan and filter system has to be redesigned for each combine. "That's the limitation."
Humburg hopes that this type of equipment will become standard fare on combines.
Coping with new emission standards
To meet new emission standards effective in 2014, combine manufacturers are focused on cleaning up diesel exhaust, he explains. Some of this equipment uses a diesel particulate filter to trap the black soot. However, to regenerate the filter, manufacturers are running the component hot enough to burn the material away. This creates yet another danger area when it comes to sunflower dust.
Once the new combine models can meet the exhaust requirement, manufacturers will look at fixing things–and this will be one of the issues they must address, he explains.