The burning issue of combine harvester fires


Preventative and precautionary measures are essential in reducing the potential for combine harvester fires, according to a Grains Research and Development Corporation-funded investigation into the issue. A spate of harvester fires last season on South Australia’s Yorke Peninsula triggered industry concerns and led to the GRDC seeking an independent investigation and report on harvester fires. The research was conducted by Dr Graeme Quick, an internationally-recognised agricultural engineer and harvester expert. He was engaged by the GRDC to look at the causes of the blazes and to prepare a set of recommendations for reducing the impact and consequences of combine harvester fires.

Dr Quick canvassed professional advice and industry opinions about combine fires, then investigated harvester fire incidents in southern Queensland, northern New South Wales and on the Yorke Peninsula. The most common cause of harvester fires was in the engine bay, where material can collect on hot components such as the exhaust manifold and turbocharger. An extensive US study over 15 years showed that 77% of harvester fires initiated in the combine engine bay. “Crop materials collecting or clumping on hot components can ignite, then embers can drop down or are blown around the machine and into the crop to cause smouldering and spot fires,” Dr Quick said. “Others causes are failed bearings or brake problems, electricals, fluid leaks and rock strikes.”

Static electricity was cited by some operators as a cause of harvester fires. This became a particular focus of Dr Quick’s investigation. “Static electricity builds up on operators and machinery in low-humidity atmospherics. The evidence, however, does not support static electricity as a prime cause of harvester fires. While it is true that static electricity builds up on moving machinery, the charge is most probably insufficient to ignite dry crop materials on harvesters.

“Given appropriate conditions, an operator can generate a higher charge from sliding across the seat of a vehicle. The plastic panels on some harvesters are insulators and definitely not at fault. The fire issue affects all brands, with or without plastic panels. “The relative proportion of fire incidents on combines may be rising somewhat, but that could simply be due to the increasing crop throughput and hours logged of modern machines. They have bigger engines and greater heat load.

“On SA’s Yorke Peninsula, the increase in fire incidents is most likely attributed to the expansion in lentil production in recent years. Lentils are one of the more fire-prone crops. “This crop barely reaches 300 millimetres in height, so it requires harvesting low to the ground to gather the pods. Lentil harvest generates liberal amounts of sticky dust. Flinty rocks increase the chances of fires at the front,” Dr Quick reported. The practice of desiccating or spraying out crops to eliminate weeds provides for uniform crop maturity at harvest, but results in a loss of green material that might otherwise have dampened fire risks, according to Dr Quick. “Whatever the cause, the costs of harvester fires in terms of crop loss and of machinery are extensive. My guess is that there are around a dozen combines totalled each year in Australia and there are hundreds of fire incidents, many of which may go unreported.

“For example, there are spot fires quickly extinguished by the operators. So far no lives have been lost due to combine harvester fires, fortunately.” Supported by the GRDC in his findings and his recommendations, Dr Quick said the key to avoiding harvester fires was diligence in cleandown and inspection, and to postpone paddock work during the highest fire risk periods. “The greatest need is suitable equipment and operator diligence in a fire-prone environment. This calls for systematic preparation and prevention procedures,” Dr Quick said. “All operators should equip their machines with at least two fire extinguishers. A high capacity air compressor with air lances should be on board or at hand. Regular blowdowns are essential and in the worst conditions a blowdown may be needed as frequently as every half hour.”

The following is a checklist developed by Dr Quick for reducing fire hazards on combine harvesters:

1. Recognise the big four factors that contribute to fires, namely relative humidity, ambient temperature, wind and crop type and conditions. Stop harvest when the danger is extreme. In North America sunflowers have ignited in sub-zero temperatures – the critical factor was residues on hot spots and low humidity.
2. Redouble service, maintenance and machine hygiene efforts at harvest on the days more hazardous for fire. Follow systematic preparation and prevention procedures.
3. Use every means possible to avoid the accumulation of flammable material on the manifold, turbocharger or the exhaust system. Be extra wary of tailwinds that can disrupt the radiator fan airblast that normally keeps the exhaust area clean.
4. Be on the lookout for places where chafing of fuel lines, battery cables, hot wires, tyres, drive belts etc, can occur.
5. Avoid overloading electrical circuits.
6. Periodically check bearings around the front and the machine body. Use a hand-held digital heat-measuring gun for temperature diagnostics on bearings, brakes etc.
7. Drag chains, or better still drag cables or grounding conductors, may help dissipate electrical charge but are not universally successful in all conditions. In certain conditions a drag chain could even start a fire from rock strikes. On the other hand there are some invaluable fire-suppressing options on the market – these are listed in the report.
8. Use the battery isolation switch when the harvester is parked. Use vermin deterrents in the cab and elsewhere, as vermin chew some types of electrical insulation.
9. Observe the Grassland Fire Danger Index (GFDI) protocol on high fire risk days. Don’t jump to a conclusion that static electricity is a cause of fires; the evidence doesn’t support this as a prime cause on harvesters.
10. Maintain two-way contact with base and others. And keep an eye out for hazards on machinery during the season.

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