Aeration fans should be started as soon as the bin floor is covered with grain and operated continuously until the grain is dry or the average air temperature is below 35° F for extended periods. Leave all roof hatches open to provide a large air exhaust opening, approximately 1 sq. ft. for each 1,000 cubic feet per minute of air delivered to the bin.

Adjusting the temperature of grain in a filled bin should be done in steps. The movement of a temperature front (zone) completely through the grain is one cooling or warming cycle. Each time an adjustment is made; one must run aeration fans continuously until the zone moves completely through the grain before shutting down the system. Failure to do so can lead to major problems in the grain mass wherever the front was allowed to stop. How long that takes varies with the number and sizes (airflow rates) of aeration fans attached to a bin, as shown in Table 2.

grain cooling and warming cycle times

Grain drying or rewetting is usually insignificant during grain aeration. Because the cooling (or warming) front moves through the grain about 50 times faster than a drying or wetting front, only a small fraction of the grain is rewetted during an aeration cycle, even with high humidity. As a precaution, operate the aeration fan only long enough to accomplish the grain cooling or warming cycle. This is particularly important with higher capacity aeration fans.

When the daily average temperature drops below 35° F, cool the grain to a uniform temperature and turn the fan off. If moldy odors are detected or the grain starts to heat, turn the fan on until the conditions are corrected. 

After cooling is completed, close the roof hatches and cover fan inlets to prevent migrating air from adding moisture to the grain.

If grain has been dried correctly for the storage period intended, problems with grain condition usually result from: 1) Improper grain cooling; 2) Inadequate observation of the stored grain for early detection of developing problems; 3) Poor initial grain quality; and 4) Improper insect control. Each of these problems can be minimized with good management.

Remember, working around flowing grain and grain in storage can be very dangerous. Follow safety rules at all times while working in or around grain bins.

For more information about managing dry grain in on-farm storage bins see factsheets from Purdue and Ohio State:

Managing Dry Grain in Storage (Purdue University)

Natural Air Grain Drying in Ohio FactSheet AEX-202-06 (The Ohio State University)


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