The document discusses cleaning and grading of grains for physical characteristics. It describes types of cleaners and graders, specifically air screen cleaners. It explains that air screen cleaners use screening and aspiration to separate grains based on size, removing impurities. The document outlines factors that influence air screen cleaner design, like material properties, machine settings, and screen specifications. Finally, it provides an overview of the industrial setup for cleaning and grading operations.

1. CLEANING AND GRADING – PHYSICAL
CHARACTERISTICS OF GRAINS FOR CLEANING AND
GRADING – TYPES OF CLEANERS AND GRADERS – AIR
SCREEN CLEANER
COMPILED BY-
ANUJ JHA
2014027007
FPE 251- Crop Process Engineering

2. Spotlight……..
• Cleaning
• Grading, sorting and scalping
• Objectives of cleaning
• Physical characteristics of grains for cleaning and grading
• Screening and Air screen cleaner
• Vibratory and rotary air screen cleaner
• Factors influencing the design of air screen cleaner-Machine
and materials
• Industrial Setup for Cleaning and Grading
• Universal Cleaning Machine

3. Cleaning
Remove foreign and undesirable material
To separate grains into various fractions
Commercial value of agriculture products depends on grade factors
Physical
characteristics
• Size
• Shape
• Color
Chemical
characteristics
• Odour
• Free fatty acid
Biological
characteristics
• Germination
• Insect damage

4. Grading, Sorting & Scalping
• Grading refers to the classification of cleaned products into various
quality fractions to enhance commercial value
• Sorting refers to the separation of cleaned product into various
quality fractions on the basis of colour, size, shape, density, texture
etc.,
• Scalping refers to the removal of few large impurities

5. OBJECTIVES OF CLEANING
1. To reduce requirements for drying and drying cost.
2. To remove materials that could cause deterioration during storage.
3. To remove materials that could damage the conveying and milling
machinery.
4. To remove materials that cause a reduction in the grade.
5. To reduce storage requirements.

6. Physical characteristics of grains for cleaning and grading
Physical properties of seeds- Size, Shape, specific gravity, surface roughness, colour
Designing of air screen cleaner- shape and size of grain determine the screen openings,
angle of inclination and vibration amplitude and frequency of screens
Size of screening surface- determined by density of grains
Frontal areas and related diameters- determination of terminal velocity

7. SCREENING
• Method of separating grain/seed into two or more fractions
• according to size alone
• Most widely used device is screen
• Material retained over a screen is oversize material
• Material passes through the screen is undersize material
• Material passes through a particular screen and retained over a
subsequent screen is intermediate material

8. AIR SCREEN CLEANER
• Performs the separation based on size alone
• Screens used in combination with air blast performs satisfactory cleaning
and separation operations for most of the granular materials
• Uses three cleaning systems; aspiration, scalping screen and grading lower
screen
• Classified into two types based on the movement of the screening surface
• Vibratory screen
• Rotary screen

9. VIBRATORY AIR SCREEN CLEANER
Screening unit is composed of double or multiple screens.
Screens are tightened together and suspended in such a manner that
these have horizontal oscillating and slightly vertical motion.
The slope of the screen is adjustable to control the rate of forward
travel of the grain
To avoid clogging, the screens are fitted with brush
Two screen m/c fitted with aspirator to suck the lighter materials
Coarse impurities are screened off by upper screen
Fine impurities are screened off by lower screen
Grains are again cleaned by upward draft of air in the ascending
separator
During this process, remaining lighter impurities and shriveled grains
are sucked away
Lighter impurities are removed by Cyclone separator

10. Rotary Air Screen Cleaner
• Has normally circular decks
• Motion is circular in horizontal plane
• Either single or double drum
• Consists of a rotary screen, aspirator and hopper
• Sound grains pass through the screen perforation into the center of
the screen drum
• Oversized material is retained above and pass out through an outlet
• Sound grains come out at the center side of the drum rotating at low
speed and fall onto the vibratory screen which remove the dirt
particles
• Light impurities are sucked away by the aspirator
• Cleaned grains are discharged through the discharge chute

11. FACTORS INFLUENCING THE DESIGN OF AIR
SCREEN CLEANER
• A. Material factors
• Compaction or bed density
• Free flow of material is greatly affected by compaction
• Particle size and shape
• Deciding factors towards the identification of proper sieve
configuration
• Distribution of various fraction sizes
• Straw, chaff, node etc in the mixture greatly influence the
separation
• Stickiness and abrasiveness
• Material abrasiveness affects the selection of screen

12. • Feeding mechanism
• Feeding should be done properly in order to obtain maximum capacity and efficiency
• Size of screen surface
• Width of screen affects capacity whereas its length affects efficiency
• Length of screen should be between 2-3 times its width
• Grain bed depth
• All particles should be in contact with the screen
• 1600 kg/m3 - Thickness of bed should not exceed 4 times the size of screen aperture
• 800 kg/m3 - Thickness of bed should not exceed 2.5 - 3 times the size of screen aperture
• Shape of the opening
• Depends upon the shape of the grain to be handled
• For round shaped grain, top screen of round holes and bottom screen of slotted holes are used
• For elongated grains, slotted top screen and slotted bottom screen are used
• Percentage open area
• Higher percentage open area increase both capacity and efficiency
• Triangular spacing is invariably used
B. Machine factors

13. • Vibration amplitude and frequency
• Objective is to properly stratify the feed over the screen
• Fast shake speeds are very effective in cleaning chaffy materials
• When the speed is too fast, round seeds tend to bounce over the screen and are not
sifted properly
• Number of screens
• Most efficient screening results when a series of single deck screens are used
• Rate of forward travel
• Indicates the travel of material in m/min
• Useful in determining the capacity
• Air velocity
• For removing the lighter particles based on difference in density of the material
• 8m3/min per ton of paddy upto 8 t/h & 5 m3/min for capacity more than 10 t/h are
recommended

14. Industrial Setup for Cleaning and Grading

15. Universal Cleaning Machine
(Cleaning, Grading and aspiration)

16. TO BE
CONTINUED…….