Grading (also called classification) is the screening process of separating bulk material into two or more defined particle size fractions using one or more screen decks. Each resulting fraction falls within a specified particle size range. Grading is distinguished from scalping and check screening by its intent: the goal is to produce distinct, marketable or process-ready size fractions rather than simply removing contaminants or verifying specifications.
In a multi-deck round vibratory separator, the top deck uses the coarsest mesh, removing the largest particles as the first oversize fraction. Material that passes through reaches the second deck with a finer mesh, producing a second fraction. This cascading process continues through each deck. The number of fractions produced equals the number of decks plus one. ScreenerKing, Sweco, Kason, Midwestern, and Rotex separators are all widely used for multi-fraction grading across food, chemical, mineral, and plastics industries.
Grading Configurations by Number of Fractions
| Decks | Fractions Produced | Typical Application | ScreenerKing Model |
|---|---|---|---|
| 1 | 2 (oversize + undersize) | Simple go/no-go separation | SiftPro 18", 24", 30" |
| 2 | 3 (coarse + medium + fines) | Standard product grading | SiftPro 24", 30"; SiftPro 48 |
| 3 | 4 fractions | Multi-grade product lines | SiftPro 48 |
| 4-5 | 5-6 fractions | Precision grading (abrasives, spices) | SiftPro 48; SiftPro 60 |
Why This Matters in Vibratory Screening
- Product value — Grading creates defined fractions that command higher prices than unsorted bulk material. Precisely graded products meet customer specifications and reduce rejections.
- Process control — Classification feeds specific size fractions to downstream operations that require uniform particle size, such as tableting, coating, blending, or reaction processes.
- Mesh selection — Each deck requires a specific screen cloth mesh size to define the cut point between fractions. Proper mesh selection is critical to hitting target specifications.
- Efficiency trade-offs — Adding more decks produces more fractions but reduces throughput per deck. Operators must balance the number of fractions against production rate requirements.
Related Glossary Terms
- Classifier — A screener configured for multi-fraction grading
- Particle Size Distribution — The size makeup of the feed material
- Scalping — Removing only the coarsest fraction before processing
- Check Screening — Verifying product meets spec after processing
- Screening Efficiency — Accuracy of each grading cut point
Grading / Classification FAQs
What is grading or classification in screening?
Grading is the process of separating a bulk material into two or more defined particle size fractions using vibratory screens. A single-deck screener produces two fractions, while multi-deck configurations produce additional fractions at each deck.
How many fractions can a vibratory screener produce?
The number of fractions equals the number of screen decks plus one. Round vibratory separators like the ScreenerKing SiftPro 48 can accommodate up to five decks, producing six graded fractions in a single pass.
Multi-Fraction Grading Screeners
ScreenerKing offers round vibratory separators from 18" to 60" with up to five decks for precision grading across all industries.