Basics of Seed Conditioning Dr. Steven Beckham

Physical Differences Dimensional Differences A. Length B. Width C. Thickness Shape Density Surface Texture Color Affinity for Liquids Electrical Conductivity

Basic Seed Conditioning Basic Machines Air screen machine Setting the fans Setting the screens Bucket elevators Spiral separator Precision sizers Length graders Aspirators Gravity tables Seed treaters

Width and Thickness Sizing Techniques (Diagrams Show Cross-Section Views of Cylinders)

Basic Seed Conditioning Air Flow Measurements and Adjustments Terminal Velocity Dust conveys at 2,500 fpm; whole soybeans and corn convey at 5,500-6,000 fpm Fans are rated in CFM (cubic feet of air per minute) To find velocity – divide CFM / area of pipe or duct Example – Fan has CFM = 3,000; If the duct is 10” x 12” = 120 square inches = (120/144) or 0.833 square feet; the velocity = 3,000 / 0.833 = 3,601 feet per minute If the same fan had a duct 14” x 14” = 196 square inches = 1.36 square feet the velocity would be 3,000 / 1.36 = 2,205 feet per minute

Basic Seed Conditioning (cont.) Static Pressure Any time we decrease the duct size or put a bend in a duct the static pressure will increase. When static pressure increases, velocity will decrease. Never increase or decrease the area of the ducts coming out of a cleaner fan or aspirator fan. Keep bends to a minimum. If there is a bend make sure the radius of the bend is a minimum of twice the diameter of the duct. Keep the total run of ducting to a minimum.

Basic Seed Conditioning Cyclones and Dust Filters Cyclones work by decreasing the velocity of the air, which falls below the terminal velocity of the dust or other particles. That causes the dust to settle out. If the cyclone is too small the velocity will not decrease enough to settle the dust. Cyclones need to be tuned or balanced. This is done by adjusting the vent cap so that pressure differential between the vent cap and the bottom discharge is almost equally balanced. If done correctly a piece of heavy paper will “just fall away” when placed over the bottom discharge. If the vent cap is open too much dust will plume out the top. If it is closed too much dust laden air will blast out the bottom. Dust filters work by actually filtering dust from the air as it passes through. The critical calculation for sizing dust filters is the – air / cloth ratio. On dirty air from the air screen machine there should never be more than 10 cfm per square foot of filter cloth. Dust hoods can get by with up to 30 cfm per square foot of filter cloth. Filters must be kept clean to work. Pulse jet filters have automatic cleaners built in. Dust bags need to be shut down periodically and shaken to keep clean.

DAMAGE CONTROL Force = Mass * velocity If velocity doubles 2 Force = Mass * velocity If velocity doubles Force increases 4 times After 1 second 32 ft. / minute After 2 seconds 1024 ft. / minute