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

What’s the purpose? Manage: –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.

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.

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.

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.

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.

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.

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.

How do we know T? Thermocouples throughout bin –Permanently installed –Hung on cables Pipe with thermometers Temperature probe at least 3’ long CO 2 monitor at exhaust of fan –Change indicates insect or mold activity Carol Jones, PhD. Stored Product Engineering Biosystems and Ag. Engr. Dept.

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.

So what about RH? Example Carol Jones, PhD. Stored Product Engineering Biosystems and Ag. Engr. Dept. RH at various Temperature Grain MC40F60F75F

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.

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.

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.

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

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.

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.

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

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

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

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

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

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