Silo Fires - Costly, Frustrating and Even Deadly (News Release)

  • Prather, Timothy G.

With the extreme heat and drought this year, the risk of silo fires may be increased. Crops harvested too dry will not produce quality silage and will increase the risks of silo fires. Fire risks are even greater if your silo has air leaks through cracks and around doors.

Make sure your silo is in good repair. Inspect it carefully and seal any cracks to keep air out. Check the condition of doors and make sure they are sound and fit tightly.

Ensile crops at 50 - 68 percent moisture content. Check the moisture content with a moisture meter or use an oven-drying method to determine crop moisture content. You cannot accurately judge moisture content by sight or by touch. Too much moisture results in seepage and silo damage; too little moisture can result in a fire. Correct moisture is required for good feed.

Using a distributor will increase the amount of silage you can store by 10 percent by making full use of the silo. The distributor will also result in even distribution and even packing without a hard core; thus, fewer air pockets and better silage. Even distribution also protects the structure and foundation from failure.

Haylage can dry several percentage points in a short period of time on hot, sunny, breezy days. For example, alfalfa cut at 85 percent moisture can often be baled at 18 percent in two days. With this in mind, time your field operations to allow the chopper to keep pace with the mower/conditioner. Any breakdowns or delays can allow the forage to dry too much for ensiling. Either add water when filling the silo or bail the crop later for hay.

Make sure the fire department does not compound your problems if a silo fire does occur. The fire department should not pump thousands of gallons of water into the silo. The water will not soak through the silage, and may channel down along the walls instead of reaching the fire. Wetting agents are not much help, and they contaminate the silage, rendering unburned silage unfit for feed. Silos are not designed as water tanks, and soaking the silage may cause structural damage or collapse.

Oxygen-limiting silos, such as Harvestore: silos, can explode if a fire is not handled properly. Two firemen were killed in Georgia on August 5, 1993 when they applied water and foam to a fire in an oxygen-limiting silo. The explosion blew the roof off, sending one fireman to the ground over 100 yards away and the other through the roof of the nearby metal building. Two firemen on the ground were injured by debris. The top 15 feet of the silo were severely damaged by the explosion and an adjacent silo dented by the debris.

The only safe methods for controlling fires in oxygen-limiting silos are to close all hatches (but allow pressure to vent from the top hatch) and inject large volumes of carbon dioxide through the bottom of the silo.

Fires in conventional silos can be controlled during early stages by probing to locate the hot spots and injecting water directly into the fire. This practice is more effective than dousing from the top, and it uses much less water. Advanced fires are often best left to burn themselves out. If the fire has burned enough silage that the unloader cannot function, the remaining silage is probably useless as feed. Even if the fire is put out, the silo may be too dangerous to unload by hand. Fires in concrete silos do little harm to the structure, so prevent spread of fire and allow it to bum out.

For more information on silo fires, obtain a copy of publication PB 1307, Silo Fires - Prevention and Control, from your county Extension office. And remember - safety is no accident. It is a responsibility and a way of life.

This news release was distributed by the University of Tennessee Agricultural Extension Service, University of Tennessee Agricultural Extension Service, Knoxville, Tennessee 37901. Publication date: August 1993.

Timothy G. Prather, Agricultural Safety Specialist, Agricultural Engineering Department, University of Tennessee Agricultural Extension Service, Knoxville, Tennessee 37901.

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