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 Drying Bin, 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 heated air into a void space below the floor. The floor is vented to allow the heated air to flow up through the grain.  Vertical 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 frictional heating capable of igniting the grain.  Another failure mode encountered is the collapse of the grain bin floor allowing grain to be in close proximity to the burner plenum.  In all types of dryers the possibility of high resistance heating at electrical connections is viable ignition source.

The other main type of drying system used extensively is horizontal- or vertical continuous flow systems. These dryers are designed to continuously take in wet grain and deliver dried product simultaneously.  These dryers have individual columns that consist of metal mesh walls that allow heated air to flow through the grain.  Heated air is forced into a plenum area and equally distributed through the columns.  Failure modes on continuous flow dryers are similar to that of bin style dryers.  Malfunction or modification of sensors, thermostats and safety devices can cause over temperature conditions, which can ignite the grain in the drying column(s).   When conditions dictate that extremely high moisture grain be harvested, many times the grain is damaged during the process.  Worm or improperly adjusted harvesting equipment can also cause excessive damage to the grain.  The damaged grain has more fine particles contained than grain harvested at a lower moister content or with newer well maintained harvesting equipment.  The accumulation of the fine particles can cause reduced airflow and improper sensor operation.  The leading cause of grain bin and grain dryer fires is the accumulation of fine grain particles in proximity to the burner system.  Fine grain particles in close proximity to the open flame burner are a potential for disaster.  Diligent maintenance in the cleaning of grain fines from the burner area is a must.  These are all factors that must be taken into consideration when analyzing the failure mode of grain-drying equipment.