Grain Dryer Fires
In the farming industry today, nearly every farmstead has a grain-drying system in use. These systems come in many different configurations and sizes, but most of the units are fueled by either natural or L.P. gas. At Donan Engineering, our personnel are experienced in grain dryer operation and maintenance.
Two main types of grain-drying systems are in use today. The first is the Bin Dryer, which is simply a storage bin that has the capability to dry the grain as it is put into the bin. Most of these units range in size from 8,000 to 20,000 bushels of grain capacity. The configuration of these units includes a large fan and a burner that pushes air into a void space below the floor. The floor is vented to allow the warm air to flow up through the grain. Augers inside the bin continuously stir the grain to assure uniform drying. There are many potential ignition sources present in a bin dryer system. If the temperature control malfunctions and a burner continues to operate after the grain is dry, elevated temperatures capable of igniting the grain can occur. Mechanical failure of fan bearings, auger bearings, or gearboxes can also cause friction in the grain capable of ignition.
The other main type of drying system used extensively is horizontal- or vertical-batch systems. These dryers can be designed to quickly dry a designated amount of grain, or to continuously take in wet grain and expel dry grain into a storage bin. The process used to dry the grain in a batch dryer is much like that in a bin dryer. A large-capacity burner and fan move heated air through the grain. In the batch system, much less grain is inside the heated area than in the bin system.
The leading cause of grain bin and grain dryer fires is the accumulation of fine grain particles in proximity to the burner system. The condition of the grain entering the drying unit has a huge impact on the amount of fine particles that accumulate in areas where combustion could occur. This condition is largely determined by the efficiency of the harvesting equipment and the moisture content in the grain. These are all factors that must be taken into consideration when analyzing the failure mode of grain-drying equipment.