Seed Cleaning Methods – Upgrading the Quality of Cleaned Seed
We have mentioned earlier that in certain instances it is necessary and in others rather desirable to further upgrade the seed quality by removing either specific contaminants, or by very precise size grading. The various processing operations conducted after basic cleaning to further improve seed quality are regarded as upgrading operating. The choice of upgrading operation, however, shall depend upon the type of contaminants and crop seed. Table 17.2 describes the various types of upgrading operation equipment, their principle of operation and specific uses.
Upgrading Machines:
1. Type of Upgrading Operation and Types of Machines:
i. Sizing and Grading: (Dimensional Sizing):
a. Width and thickness sizing and grading
1. Horizontal flat screen separators, e.g. Clipper com sizer, superior rock-it-com grader.
2. Vertical ribbed screen separator, e.g. Dockings seed grader.
3. Cylindrical screen separators, e.g. Carter-day precision grader, superior high capacity sizer.
b. Length sizing and grading
1. Disc Separator
2. Principles of Operation of the Machine:
These machine make extremely sensitive and precise separations on the basis of differences in width and thickness. The seeds are sized for width by using round-hole screen openings and for thickness by using slotted screen openings. The separators employ gravity, centrifugal force, product pressure , or a combination of these forces, to make width and thickness separations on screens.
Seeds are separated on a pure length basis. In a disc separator , the discs lift uniformly shaped and sized and undersize particles, out of a mass of seed. The separation is not affected by seed coat texture, weight per bushel or moisture content.
3. Uses of Machine/ General Usage:
a) Removal of splits from soybeans, peanuts, etc.
b) The removal of chips and splits from sorghum seeds.
c) Removal of cheat from wheat.
d) Removal of cockle burns from cotton seed, wild onion from fescue , and wild oats from barley.
1. Removal of weed seeds.
2. Cross broken crop seeds.
3. To upgrade general appearance.
4. Size grade for precision plantings.
4. Specific Usage:
Sizing hybrid corn. Rice seed industry.
Small grains, corn, soybeans.