Grain Grader Manufacturers
Connect with verified grain grader manufacturers on Towobo. Source rotary screen classifiers, flat screen graders, grain length graders, and grain grading equipment for wheat, maize, rice, and other cereal grading and classification.
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Browse Grain Grader Suppliers →Grain graders — types and applications
Grain graders (also called grain classifiers, separators, or sifters) separate grain into size and length classes for commercial grading, cleaning, or milling preparation. The main types include: rotary drum screens (a rotating perforated cylinder with multiple screen sections — large foreign material is removed from the outside; undersized grain falls through to a bottom collection; on-size grain passes through); flat oscillating screens (vibratory or gyratory screens with multiple screen decks — separate grain into fractions by width and thickness); indent cylinders or trieur cylinders (a rotating cylinder with small indentations or cells on the inner surface — short grains or seeds are carried in the indentations and discharged at the top; long grains or stalks pass through without being lifted — used to separate short weed seeds from wheat grain, or broken grain from whole grain in rice milling); and optical colour sorters (separate grain by colour and surface defect rather than by size — standard in premium rice milling and seed cleaning). Grain graders are used both in the pre-cleaning section of grain mills (to separate contaminants from grain before milling) and in post-milling or post-processing quality grading (to produce uniform, graded products for export or premium markets).
Frequently asked questions
What screen sizes are used to grade wheat before milling?
In wheat milling, the cleaning section typically uses multiple screen sizes to grade the cleaned wheat: a top screen (typically 3.5–4.5mm round hole or 4–6mm slotted hole) removes large foreign matter (large stones, large seeds, clumps); a middle screen (2.2–2.8mm) retains the wheat and rejects oversized material; and a bottom screen (1.8–2.0mm) allows undersized grain and fine material to fall through and be collected separately. The exact screen sizes depend on the wheat variety (wheat kernel size varies by variety) and should be validated by inspection of the overflow and underflow fractions. Screen condition (holes wear and enlarge over time) must be monitored — worn screens allow oversized material to pass through with the wheat.
What is an optical colour sorter and when is it essential?
An optical colour sorter uses high-resolution cameras (and often near-infrared sensors) to inspect each grain individually at high speed, detecting discoloured, mouldy, chalky, or otherwise defective grains. An air ejector fires a precisely timed jet of air to deflect rejected grains from the product stream. Optical colour sorters are essential in premium rice milling (to remove discoloured and chalky grains that command a lower price), in seed cleaning (to remove off-colour seeds), in spice processing, and in nut and dried fruit processing. For standard commodity grain milling, colour sorting may not be economically justified, but for premium branded or export products where appearance is a key quality parameter, an optical sorter is standard.
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