Fires in upright silos can range from being a nuisance to a financial burden to deadly if not handled correctly, says Dave Hill, director of Penn State University’s Managing Agricultural Emergencies program.
He and his team are frequently called out to Pennsylvania farms to help size up just what should be done to contain and put them out. Fires started by spontaneous combustion – usually when corn silage, haylage or other material is put up too dry and doesn’t have the moisture to dissipate heat produced through natural fermentation – tend to start three to six weeks after harvest, he says.
But silo fires can start anytime and can cause $30,000 or more in feed losses.
“We hear some horror stories of fire companies, if they see smoke coming out of a silo, that they will pump tens of thousands of gallons of water into a silo. That’s just a terrible, wrong thing to do. If there’s a fire inside that silo caused by spontaneous combustion, there is a pocket someplace in the middle that is burning.”
Water pumped into a silo usually runs along its side, leaching nutrients and ruining a lot more feed than is necessary, he adds.
“One of the things we try to tell farmers, and especially fire companies, is if you get a silo fire, there’s usually no huge emergency. The product that’s in that silo is not a good fuel source. It’s not going to go rip-roaring through the silo and burn your entire operation.”
Producers can take a few hours to call for technical assistance, such as the local Extension safety specialist, to help determine the safest and most economical way of containing a fire.
He suggests that producers and firefighters download “Silo Fire Decision Tree” charts from the Managing Agricultural Emergencies Web site found at the end of this article. The charts, for conventional and oxygen-limiting silos, offer steps to be taken and ask information needed by specialists when they’re called.
An essential bit of information needed: whether the burning silo is conventional or oxygen-limiting. Oxygen-limiting silos can be more dangerous and fires in them are treated differently because of the potential for pressure to build and cause explosions.
Fires burning in pockets within a conventional silo can be located using thermal imaging cameras, which can show where the excessive heating is located. A small hole drilled into the silo, and water pumped to that specific pocket through a probe, can contain the fire until the producer can safely unload the silage to that spot in the silo.
“It’s not real simple, but it’s much more effective than flooding the silage. You’re trying to find the spot and kind of surgically enter that with your probe.
“All you’ve created is an inch-and-a-half hole that could easily be plugged up with patching material, and you haven’t ruined a whole lot of feed,” Hill says.
Fires in oxygen-limiting silos can often be treated by closing off all openings to hopefully smother the fire. Or a gas such as carbon dioxide or liquid nitrogen can be pumped into the silo to consume any air that keeps the fire burning. Early detection of fire is critical with this type of silo, he adds
But don’t always assume a fire is created within the silo. Hill says at least a third of those he’s handled were started in chutes. Chute fires can be caused by faulty wiring or old crop left within. Because fires can smoke heavily, it’s hard to pinpoint when they’re in chutes.
It’s not fun climbing a chute with an SCBA (self-contained breathing apparatus) on, or washing the chute out, but Hill says those fires are easier to put out than pocket fires within silos.
“If you notice heavy smoke, fire or embers in the chute, that chute will need to be washed out. That will be a terrible mess if you’re going to do that from the ground. What we suggest to fire companies is to try to get at the top of the silo and break into the chute, drop some sort of nozzle down from above and wash it out that way.
“When you notice a fire, it’s not going to get any worse, for the most part, in a couple of hours. Now, that said, it depends on whether the fire is in an oxygen-limiting silo or a non-oxygen-limiting silo. Oxygen-limiting silos are really a different beast and they’re extremely dangerous.”
Hill gives farmers further advice in a short paper he wrote called “Silo Fires – Protect Your Investment,” which can be found at www.farmemergencies.psu.edu, under Quick Links.