1. When Do I Turn On the Fans...
And For How LONG???
Carol Jones, PhD.
Stored Product Engineering
Biosystems and Ag. Engr. Dept.

2. What’s the purpose? Manage: Properly managed..
Temperature
Moisture
Properly managed..
Preserves quality
Helps to prevent insects
10% harvest lost every year
½ due to poor storage procedures
Carol Jones, PhD.
Stored Product Engineering
Biosystems and Ag. Engr. Dept.

3. What happens if we don’t aerate?
Cool air outside
Warm grain inside
Convection Currents
Move moisture
Wet or spoiled grain at the top-center and/or on the cold wall
Carol Jones, PhD.
Stored Product Engineering
Biosystems and Ag. Engr. Dept.

4. What does aeration do? Conditions grain and seed by
Lowering temperature in the grain
Equalizes temperature within the structure
Prevents moisture migration and condensation
Controls bacteria, insects, molds and mites
Carol Jones, PhD.
Stored Product Engineering
Biosystems and Ag. Engr. Dept.

5. What does aeration do? Little insect reproduction occurs below 60F
Eggs are controlled at 40F
40F is tough to do in some areas
So fumigation is still required but can be reduced
Carol Jones, PhD.
Stored Product Engineering
Biosystems and Ag. Engr. Dept.

6. When do we aerate? At Harvest:
Leave fans on continually until exhaust T is close to same as (or less than) average air T
Usual day-night T difference is about 20°
When outside air is 10° below grain temperature
Ideal target is 40°, or as cool as possible
Carol Jones, PhD.
Stored Product Engineering
Biosystems and Ag. Engr. Dept.

7. When do we aerate? Cool in 15 to 20° stages Example:
If grain is 80°, wait for ° weather and cool until grain is cooled to that range
Then wait for the next drop of 15° to aerate again.
Monitor grain weekly to detect heat increases
Carol Jones, PhD.
Stored Product Engineering
Biosystems and Ag. Engr. Dept.

8. How long will it take?
Goal: to move the cooling front through the grain bulk.
Depending on the season (1/10 cfm/bu):
Summer: 80 hours
Fall: 120 hours
Winter: 160 hours
Half that time if you use 0.2 cfm/bu
Carol Jones, PhD.
Stored Product Engineering
Biosystems and Ag. Engr. Dept.

9. How do we know T? Thermocouples throughout bin Pipe with thermometers
Permanently installed
Hung on cables
Pipe with thermometers
Temperature probe at least 3’ long
CO2 monitor at exhaust of fan
Change indicates insect or mold activity
Carol Jones, PhD.
Stored Product Engineering
Biosystems and Ag. Engr. Dept.

10. So what about RH? Regardless of RH, harvest heat has to be removed
Then…
Equilibrium Moisture Content (EMC) RULES !
Point at which grain and air don’t exchange moisture
Carol Jones, PhD.
Stored Product Engineering
Biosystems and Ag. Engr. Dept.

11. RH at various Temperature
So what about RH?
Example
RH at various Temperature
Grain MC
40F
60F
75F 13 54 61 65 12 47 53 58 11 40 45 51 10 33 37 44
Carol Jones, PhD.
Stored Product Engineering
Biosystems and Ag. Engr. Dept.

12. So what about RH?
1 – 2 days of rainy weather causes very little change in MC
Takes much longer to change MC than to change T
Carol Jones, PhD.
Stored Product Engineering
Biosystems and Ag. Engr. Dept.

13. So what’s the plan? Summary:
Run fans night and day at binning until exhaust fan T is close to average daily T
Then run fans only when air T is 10° less than grain until grain is about 40° if possible
After desired T, operate a few hours each week to prevent musty odors
Carol Jones, PhD.
Stored Product Engineering
Biosystems and Ag. Engr. Dept.

14. Manual or Automatic? Small grain storage: Manual
Requires temperature and humidity information
Thermometer and hygrometer
Larger bins: Automatic
Automatic will pay for itself by preventing shrink from over-drying and saving labor
Carol Jones, PhD.
Stored Product Engineering
Biosystems and Ag. Engr. Dept.

15. Automatic Controls Requires humidstat and thermostat Carol Jones, PhD.
Stored Product Engineering
Biosystems and Ag. Engr. Dept.

21. Results of over-aeration
Grain shatter
Grain is too dry
Temp. has dropped too quickly
Excessive shrink
Moisture can be added, but it’s slow and takes additional air capacity…careful monitoring
Carol Jones, PhD.
Stored Product Engineering
Biosystems and Ag. Engr. Dept.

22. Words of Caution
Make sure T front has moved all the way through grain bulk
Negative Pressure System: open vents before starting fans
Positive Pressure System: watch for roof condensation…open vents
Don’t cut corners on aeration…it never pays!
Carol Jones, PhD.
Stored Product Engineering
Biosystems and Ag. Engr. Dept.

23. Resources EMC Tables Carol Jones, PhD. Stored Product Engineering
Biosystems and Ag. Engr. Dept.

24. Resources EMC Tables (wheat, corn, soybeans) Temperature Probe
Temperature Probe
Carol Jones, PhD.
Stored Product Engineering
Biosystems and Ag. Engr. Dept.

25. Resources Hygrometer Carol Jones, PhD. Stored Product Engineering
Biosystems and Ag. Engr. Dept.

26. Resources Commercial controller Carol Jones, PhD.
Stored Product Engineering
Biosystems and Ag. Engr. Dept.

27. Resources Commercial controller (OPI System) Carol Jones, PhD.
Stored Product Engineering
Biosystems and Ag. Engr. Dept.

28. Resources
Questions
Carol Jones, PhD.
Stored Product Engineering
Biosystems and Ag. Engr. Dept.