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SAFE HAY STORAGE (page 3)
In a stack of uncured hay two fire propagation
requirements—fuel and heat—are at work. The only thing lacking in sufficient
quantity is oxygen. The
hay may smolder unnoticed for quite some time before the edge of the stack
is reached. When that happens, and oxygen is suddenly available in
abundance and there is a means for the generated heat to escape, you have
a full-blown fire on your hands. The same process may occur with damp
grain, sawdust or wood shavings, too, and in these situations an explosion
may result due to the greater amount of exposed surfaces in the material.
That means we must pay careful attention to how our hay is stacked and stored. It’s
important to protect the hay stack from water, either from rain entering
through a barn or storage building roof or the side walls, since rain-dampened
bales can allow the bacterial action to restart.
Air circulation is needed under and around
the bales to allow the hay to dry and the heat to escape. Wood floors
with gaps between the boards, such as you would find on the upper level (or
threshing floor) of a bank barn, usually provide adequate air circulation. If
you are stacking hay outdoors, on the ground, stack the bales on wood pallets
or old tires so air can circulate and the hay will not be in contact with
ground moisture. Any
hay stacked outdoors must also be completely covered, top and sides, with
a tarp to keep it dry.
If you have the choice, it’s best not to accept
any load of hay that is not completely cured, especially if it’s clover or
alfalfa hay, since these seem to be particularly prone to incomplete curing. First-cutting
alfalfa is often subject to this problem.
The presence of chemical and bacterial reactions
leading to spontaneous heating and ignition may sometimes be detected by a
“sooty” odor, and if your eyes become mildly irritated when you’re in the
immediate area of the hay stack, that, too, may indicate spontaneous heating.
It’s a good idea to monitor the heat in your
haystacks to determine if spontaneous heating is taking place. You can
make a simple temperature probe using a 10’ piece of 3/4” diameter pipe. Drill
some holes in the pipe around three inches from one end and flatten the pipe
to make a point for inserting between the bales. You want to check the
temperature in the middle of the stack, and one of the easiest ways to do
that is from the top, but you must not walk directly on the stacked hay because
there may be burned-out pockets beneath you. Walk on boards or a ladder
to spread your weight evenly so you don’t end up falling into a burned-out
void. You
should also be wearing a lifeline just in case.
Push the probe into the stack and lower a thermometer
to the end of the probe. Leave
it there for about 15 minutes before pulling the thermometer out and checking
the temperature. Here’s what the temperatures indicate:
- Below 130°F. there is no problem.
- Between 130-140°F. there is still no problem. The temperature can go up or down. Recheck the temperature in a few hours.
- At 150°F the temperature will very likely continue to rise. Move the hay to allow for better air circulation and recheck the temperature often.
- At 175-190°F a fire is about to start or is already present not too far from the probe. CALL THE FIRE DEPARTMENT IMMEDIATELY. They will stand by with charged hose lines while the suspect bales are moved from the barn or storage area. You need firefighters on the scene because the bales may ignite while they’re being moved.
If you don’t have a thermometer, you can use the probe alone. Push it into the stack and leave it for ten to fifteen minutes before pulling it out. If you can hold the probe comfortably in your hand the temperature is below 130°F. If the probe is too hot to hold in your hand it means the temperature is above 160°F and a fire is about to start or already has. AGAIN, CALL THE FIRE DEPARTMENT IMMEDIATELY.
One last pointer regarding wood shavings: If you get your shavings fresh from a local mill and heap the shavings into a pile, it's possible there might be hot pieces of wood or metal (such as from a nail embedded in the tree) mixed in with the shavings from having made it through the sawmill. If your shavings are fresh and mounded into a pile, check for smoke when the shavings are unloaded--and also several times later, just to be on the safe side.
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Content Added: Some excellent information on hay storage from Ed Scott
Also read: Hay Barn Fires by Mike Weider (PDF)