Lecture 17

Flat Structures

Aeration for Flat Structures

• Ideally - uniform air flow –  "dead zones"  – min. of .2 cfm design rate (this is double) – fines concentrate under filling auger... – Duct pacing and storage –    less than or equal to grain depth –    longest air path should be less than or equal to 1.5

times the shortest path –  max. slope to grain = 10%

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Aeration for Flat Structures

• Duct Sizing – number of bushels – airflow rate – design velocity

• Positive vs Negative pressure – 2,500 fpm = positive – 1,500 fpm = negative

Grain Sampling and Inspection

•  Tell Tale signs –    leaking grain –    bulging walls –    snow melting off the roof

•  Prevention of dead zones... –    perforated flooring best –    when ducts are used: probe "dead zones

Preventing spoilage

• Preventing spoilage –   perforated floor best, but fines accumulate below the floor -

good spot for insects – checking "dead zones" – ducts can have fines accumulate, however cleaning and

treating is much easier. – "core" in center of bin (where grain unloads) prevents air

movement- spreader – probe areas where the probing is more difficult – filling and unloading leads to stagnant grain – Stirring devices – use of a vapor barrier – sealing bottom ring to concrete

Sampling equipment needed

• Moisture tester

• Sampling probe

• Temperature probe

• Measuring tape

• Grain dividers

• Scale to weigh foreign material

Getting a good sample

• Divide bin into 5 equal parts

• use probe

• Sample each section

Still concerned?

• Fan test... Musty odor?  

• Corrective Action –    Insects - fumigate –    Wet - dry –    Hot - aerate

• Note- Value of sampler greater than value of sample