When Do I Turn On the Fans...

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When Do I Turn On the Fans...

• And For How LONG???

Carol Jones, PhD. Stored Product
Engineering Biosystems and Ag. Engr. Dept.
2
Whats 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.
3
What happens if we dont aerate?

• Cool air outside
• Warm grain inside
• Convection Currents
• Move moisture
• Wet or spoiled grainat 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 55 - 65 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
• 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 dont exchange
  moisture

Carol Jones, PhD. Stored Product
Engineering Biosystems and Ag. Engr. Dept.
11
So what about RH?

• Example

RH at various Temperature RH at various Temperature 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 whats 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.
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Results of over-aeration

• Grain shatter
• Grain is too dry
• Temp. has dropped too quickly
• Excessive shrink
• Moisture can be added, but its slow and takes
  additional air capacitycareful 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
  condensationopen vents
• Dont cut corners on aerationit never pays!

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

• EMC Tables

Carol Jones, PhD. Stored Product
Engineering Biosystems and Ag. Engr. Dept.
24
Resources

• EMC Tables (wheat, corn, soybeans)
• http//www.grainqualitycontrol.com/emc_drying.htm
• 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.
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Resources

• Commercial controller (OPI System)

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

• http//biosystems.okstate.edu/Home/jcarol/index.ht
  ml

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