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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%
•
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