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S.D. Study Looks at Combine Fire Causes & Solution

Tuesday, August 30, 2011
filed under: Research and Development

Ask a grower where fires can happen on their combine during sunflower harvest, and he will likely have a one-word answer: everywhere. Wherever dust builds is potential for a smolder. Growers report smolders on the engine compartment, exhaust manifold, turbo charger, feederhouse, chassis and more. Most producers stress the need to keep the combine clean and make sure your nose is working well.

The energy spent trying to implement all the recommended precautions and tips robs a grower of valuable time. Despite all necessary steps, combine fires still linger. In response, members of the South Dakota Oilseed Council (SDOC) approached researchers within the Agricultural and Biosystems Engineering Department at South Dakota State University about a potential project to study the complexity of combine fires during sunflower harvest. Researchers returned to the council with a proposal, and funding was approved for a one-year study.

“The idea came about from growers,” says SDOC Director Rick Vallery. “We are here to use the checkoff dollars wisely to help where we can in trying to solve these types of issues for the growers.”

The study is rather unique in that little emphasis has been focused in the research community on studying the characteristics of sunflower dust and how it leads to combine fires. Members of the council and the researchers involved in this current study had little luck finding other literature available from past studies and could find no previous major analysis of sunflower dust.

The partnership with SDSU came together as the council members discussed this primary question: Is it the sunflower dust, or is it the machinery? The study’s three-part objective is to understand the basic characteristics of sunflower dust in the lab, see it in action in the field, and bring the data together to suggest potential engineering solutions that could serve to interrupt one or more of the factors that are present when a fire starts.

The study, which began on May 15, is still in the early stages. Dr. Zhen Grong Gu and graduate student Joe Polin have been working in the lab to characterize the physical and chemical properties of sunflower dust that result in its unique ability to start and propagate fires. Work is being conducted on two different types of dust — from sunflower stalks and from corn stover — to try and simulate conditions in the field. What is it about sunflower dust that makes it so susceptible to fire? First, how do the organic compounds of dust influence combustion; and second, what are the ignition points (lowest temperature to start ignition) of sunflower dust? The key is to identify the energy level (static electrical spark), temperature level (of environment) and oxygen contents present at ignition.

The scientists are looking at three different scenarios in the lab in order to analyze the different ignition points.

In the first, during which they create dust clouds, dust is blown into a tube where they expose it to different temperatures in continuous flowing air. The goal is to see at what point the dust becomes combustible.

The second exposes a spark electrode to the dust cloud to measure lowest ignition energy of dust at different temperatures, humidities and oxygen content.

The third involves placing layers of dust on a hot plate and raising the temperature slowly to identify hot zones and ignition points of the dust layer.

Field Study at Harvest

As harvest approaches in central South Dakota, the study moves to the field, with lab results dictating what will be looked at more closely in the real-world scenario.

The field crew will spend four to five days during the 2011 sunflower harvest in combines ranging from the Pierre to the Selby, S.D., areas. The goal is to better understand the nature of dust movement in the engine compartment. The researchers hope to discern whether fires/smolders originate on all hot surfaces, or are initiated by airborne embers and translocated into other locations within the combine, where the fires then develop.

Building upon the lab results, a description of the ignition and translocation of embers and potential ignition sources, among other factors, will be documented during the harvest process in the field through observations and instrument-based analyses. Heat guns will be used to measure hot spots, remote sensors will monitor engine compartments, and members of the crew will also collect dust for further study. Here in the field, environmental factors that lead to critical thresholds for fires will be documented and analyzed, taking into account the unpredictability of harvest conditions.

Kevin Dalsted, an SDSU project investigator who specializes in remote sensing, says the field observations will allow the lab work to be put in perspective. “In the field we’ll be looking at weather conditions, temperatures, wind speed and relative humidity as well. We can get out there and see how those factors tie into the scientific findings,” he notes.

Possible Mechanical Solutions

The study findings will be organized based on lab results and the field data, combining both to achieve the third and final step in the study: the suggestion of potential engineering solutions which could interrupt one or more of the factors that must be present to initiate a fire.

Dr. Daniel Humburg, SDSU ag engineering professor, specializes in machine systems and is one of the collaborators on the research project.

“I’m most interested in the exhaust system,” Humburg explains, “since this is the hottest area of the engine compartment. Is that the origin of fires, or do the smolders start and then redistribute from there? Those are going to be important questions for us.”

Humburg says the research team has theories like this, but their work will focus on finding out if their theories are verified by observations both in the lab and the field. As they try to answer the “why” question, they can move toward a possible solution, including equipment adjustments.

“We don’t expect to solve the issue, but we’re taking an in-depth look into the characteristics of sunflower dust and the conditions on a combine that interact with it to cause problems,” Dalsted adds.

In effect, understanding the basic behavior of the key ingredients in combine fires will hopefully point toward factors that have the most practical potential to be changed and result in the reduction of the problem for growers.

“We took a broad approach in the research proposal. There may be something there that we can expand on after these findings come in,” Vallery says. “Is there something, for example, that can be done genetically in the plant breeding process to address the particular characteristics of sunflower dust that make it prone to stick to engine parts and initiate combine fire? We hope this research can feed other studies in the future.”

— Sonia Mullally
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