The incident occurred on a large farm located approximately 3/4 miles north of
Burnside, Illinois and about ten miles north of the City of Carthage. The farm’s principal
buildings consisted of an occupied single-family frame home, a large wood frame
shed, two metal clad pole sheds used for farm equipment storage and repair, and two
large circular metal silos. A small, frame farm office building was located near the
machine shop pole shed. Three unused wood frame barns were also on the property.
The farm’s principle crop was corn and soybeans.
No pressurized public water supply was immediately available at the site. The
closest hydrant was located about 3/4 mile away in the town of Burnside and was
supplied by a four-inch water main. A second public water supply was available seven
miles away. The farm had two water ponds available for drafting operations.
The fire and subsequent explosion involved the farm’s grain drying operation
where harvested corn or soybeans was heated to reduce the moisture content before
being stored. The grain dryer and supporting equipment was located to the west of the
large wood frame shed and to the north of the west large metal grain silo. Although a
portable unit with wheels, the continuous flow grain dryer had been at the location for
many years. The dryer was principally constructed of metal with internal conveyors
and passages that provide for fan forced heated air to dry the grain. The grain and the
heating fuel were the primary combustibles in the dryer.
Mechanical power for the dryer’s fans, conveyors, and grain movement equipment
was provided by a power take off (P.T.O.) from a field tractor at the front (north)
end of the dryer. Electric power for the dryer’s controls was from an outdoor panel
located southeast of the dryer near the pole shed between the two grain silos.
The fuel supply for the dryer and the field tractor was provided from two,
1,000-gallon LP-Gas fuel tanks located immediately adjacent to the west wall of the destroyed wood shed. Distance between the shed and the tank closest to it was less
than three feet and the tanks were less than five feet apart. The distance from the dryer
to the tank closest to it was about 15 feet. Both tanks had integral steel legs, which
rested on concrete pads. One tank had been at its location for many years and the
second LP-Gas tank was added several years ago. At the time of the investigation, the
identity of the original tank could not be determined. The two LP-Gas tanks, when
full, provided about 36 hours of fuel for the dryer and tractor.
LP-Gas moved from the tanks to the dryer and tractor by means of a rubber LPGas
hose. The hose connected the west tank to a tee fitting located near the front of the
dryer. From the tee, fuel split to the dryer and the tractor. The hose reportedly lay on
top of the ground between the tank and dryer. The hose was used for both vapor and
liquid fuel transfer through different valved connections to the west tank. The dryer
was indicated to start with LP-Gas vapor and then switched to liquid when warmed and
under load. The tractor always used liquid and it did have an integral fuel tank that
should have allowed the tractor to operate while the hose contained vapor.
At the west tank the LP-Gas hose was also connected to a tee. This fitting
allowed the line to be attached to both the liquid withdrawal and vapor withdrawal
connections on the tank. By means of manual valves, either vapor or liquid could be
sent to the dryer and tractor.
When either LP-Gas tank emptied, the hose and fittings would be disconnected
from the empty tank and attached to the full one. The dryer would have to be restarted
and potentially any trapped air removed from the fuel hose. About two weeks before
the incident, the delivery driver for the LP-Gas supplier suggested a means to manifold
the two tanks together and eliminate the hose transfer process.
The driver suggested attaching a liquid transfer hose, used for filling LP-Gas
fueled field tractors, to the liquid withdrawal connection on the top of the east tank and
to the liquid fill connection on the west tank. No similar vapor space interconnection
between the two tanks was identified during investigation. The liquid transfer hose did
have a manual valve at one end but there was no indication of check valves, relief
valve, or excess flow valves in the hose.
The tank manifold configuration worked satisfactorily and the two tanks were
filled several times during the two-week period. Prior to the explosion, roughly 35,000
bushels of grain had been dried during the current harvest season without mishap. Both tanks had been filled in the morning of the incident and had been in operation for about
seven hours without a problem.
The grain drying process began with grain brought from the field and gravity discharged
into a field tractor PTO driven auger that deposited the grain into the wet bin. The
wet bin was a vertical metal storage unit with a conical shaped bottom that acted as a surge
bin for the dryer. It provided a continuous feed to the dryer while grain trucks from the field
were changed.
From the wet bin, the grain discharged from the bottom by gravity into an electric
motor driven auger, which discharged, at the top front of the dryer. Once inside the dryer,
grain movement was provided by the LP-Gas fueled tractor, which mechanically powered the
dryer. From the dryer, the grain discharged into another electric motor powered auger, which
elevated the grain into one of the two storage silos. The unloading of the trucks from the field
and discharge of grain into the wet bin was supervised. Once running and adjusted, the dryer
did not require constant supervision. The dryer was started each morning and was stopped in
the evening.
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