Hot headers: how to reduce fire risk

Published: November 2018 | By: Justin Law

Fires in harvesters are far too common but researchers say they are completely preventable.

harvesting crop

EVERY year, 7% of combine harvesters – or ‘headers’, as the growers call them – operating in Australian paddocks are likely to catch fire. Of those, 10% will result in significant machinery destruction and crop damage – plus there’s the potential risk of injury. 

Ag research company the Kondinin Group has put a fair bit of time into the issue and says header fires are completely preventable. Ben White, a research engineer at the company, took on the task of figuring out how these fires start and his surveys of growers and contract harvesters identified machinery hygiene, in particular dust and chaff build-up, and bearing failures as the main causes.

Because a header isn’t moving fast, dust and chaff can accumulate on the machine or stick to oil around hydraulic motors. Temperatures on the exhaust system, including the turbo, get well above the point where this accumulated crop residue can ignite. “This can be as low as 130°C in lentils, but exhaust components reach temperatures of up to 450°C,” Ben says.


USEFUL TECHNOLOGY TO REDUCE HARVESTER FIRE RISKS 

In his research into reducing fire risk, Ben says he turned to motorsport for inspiration and discovered a number of potentially useful tools. Heat-shield paints or fire-retardant fibrous coatings, exhaust bandages or jackets and insulative double ceramic skins on the exhaust system were just some of the racing industry’s thermal barrier options now being trialled on grain harvesters.  

“It is important growers check first whether modifications [such as heat shields] will impact their warranties, but they are just some of the tools coming into play to help us reduce the risk of harvester fires,” Ben White says.

But even the most sensible precautions won’t completely prevent fire from taking hold in the paddock. Sparks from striking a rock, bearing or brake failure, and even the material being harvested can all contribute to fire risk.

combine harvester in field
Fire hazards caused by hot headers are easily preventable, according to experts.

STATIC ELECTRICITY OFTEN BLAMED FOR HARVESTER FIRES

Sometimes the cause is never found and there doesn’t seem to be an explanation at all, says crop farmer Curt Severin from Brocklesby in the NSW Murray region. “We had one fire that we think had to be electrostatic because it started near the feeder head driving in canola,” says Curt Severin.

“There wasn’t anything there like a bearing collapse that we could see that would have started it. It sucked up inside the header so that was a pretty entertaining hour or two.”

RELATED CROPPING ARTICLES: 
Biofuels: Australian farmers’ untapped resource
Is lupin the new superfood?
 
“Luckily the fire captain was just over the hill on the same UHF radio channel, so he heard everything from the start and the truck was there pretty quick. We emptied seven fire extinguishers into the threshing drum, so luckily there was no great damage.”

Static electricity is often thought to be a cause. It’s not uncommon to feel the zap of a static charge from the machine when you’re out harvesting in dry and dusty conditions. However, Ben White says it’s not the risk many think it is.

“The static energy on a harvester ranges from about 10 millijoules [mJ] to 150mJ, whereas the static energy required to ignite a fire is about 500mJ in a continuous arc,” he says, adding that static electricity does attract dust to the machine, causing fuel to build up.


DUST BUILD-UP ONE OF THE BIGGEST FIRE RISKS

This build-up of flammable organic dust is something farmers dread most, and Curt Severin agrees keeping the harvester clean is the best way to prevent fire. “We had a big fire on our old header,” Curt says.

“We’d pulled a lot of the guarding [heat shielding] off our header to make it run cooler, which might have been part of the problem. We had a lot more fires than a neighbour with the same header,” Curt Severin says.

“It might have been that the dust was able to build up, whereas the guarding on the machine would get so hot that dust would hit and dissolve straight away so it dissipates.

“But if it rains on the windrow [row of cut crop] after it’s been cut, it can get a mould on it, which makes the dust heavier and that seems to build up thicker on the machine.”


Dust on harvesters increases fire risk
A build up of flammable dust on your harvester can pose one of the biggest fire hazards. Keeping your machinery clean in fire risky conditions is crucial.

The heavy build-up on Curt’s machine caught fire and again quick action saved the day. An air compressor to clean the header was soon on his shopping list. “It blows a lot of material off in not much time,” Curt says. “In good conditions you might be doing that every other day, in bad conditions it might be more than once a day.”


ALWAYS BE PREPARED – AND CHECK INSURANCE COVER

Modern harvesters are becoming less prone to fire. The new Claas Lexion, for instance, has a cooling fan that draws air from above the machine and blows down and through areas where dust can build up.

Automated fire extinguishing systems are also being developed, although Curt warns they can be an expensive exercise if they go off for no good reason. “There’s a capillary line that runs around the machine and if it melts, it sets it off,” he says. “But they’re charged with nitrogen which is expensive so you can’t just use it on a whim, and if a belt snaps and cuts the lines, you’ve got a $1,500 fire extinguisher refill.”
 
Ben says keeping an eye on the fire danger index with a hand-held weather meter and having plenty of fire-fighting equipment at hand is good practice. He recommends keeping 1,000 litres of water nearby, and carrying two fire extinguisher sets on the harvester – one water, and one powder fire extinguisher (ABE). Failing that, he says farmers should ensure their insurance covers everything on the harvester including the GPS guidance system.


 
Dusty headers create preventable fire risks



Ben White’s tips for preventing and handling header fires

- Regularly clean down machinery to reduce fuel load.

- Monitor bearings with an infrared temperature gun.

- Monitor ambient conditions and the fire danger index.

- Consider heat shield or exhaust modifications, such as exhaust paints or coatings, including ceramics and alumina silica, which can minimise dust adhesion and reduce hot component surface temperatures.

- Investigate exhaust bandages and blankets designed to insulate exhaust components.

- Consider double skins on the exhaust system (which are insulative, like a thermos).

- Ensure an electrical isolator system is used.

- Ensure the fuel system is well maintained.

- Maintain and keep airflow systems clear.

- Check concave doors are well sealed (minimise dust leakage which may in turn contact hot surfaces).

- Ensure your harvest team has a plan and knows their individual responsibilities in the event of a fire.


If your harvester does catch fire, pull out of the paddock and call 000.
 

Enjoy this story? Want more in-depth news on farming in NSW? Members of NSW Farmers receive a free glossy monthly magazine called The Farmer, direct to their letterbox, with over 130 pages of exclusive news, views and deep analysis. Plus of course, you get all the benefits of being a member of the largest state farming organisation. Join here