Attrition in vibratory screening is the gradual wearing, chipping, or erosion of particle surfaces caused by repeated contact between particles and between particles and the screen surface, generating unwanted fine particles that affect product quality and screen performance. Unlike friability, which involves sudden fracture, attrition is a progressive surface degradation that produces very fine dust-like particles over the course of the screening operation.
Every time a vibratory screener cycles, particles collide with each other, slide across the screen wires, and are thrown against the screener walls. Each contact removes microscopic amounts of material from particle surfaces. Over millions of contact events during a typical screening operation, these micro-removals accumulate into a measurable quantity of attrition fines. The rate of attrition depends on material hardness, particle shape (angular particles attrite faster), G-force, residence time, and the bed depth (more particles means more contact events).
Attrition vs. Friability Comparison
| Characteristic | Attrition | Friability |
|---|---|---|
| Mechanism | Surface erosion, rubbing, chipping | Impact fracture, shattering |
| Fines produced | Very fine dust (<10% of parent size) | Large fragments (10–50% of parent size) |
| Rate | Gradual, progressive | Sudden, event-based |
| Primary cause | Particle-to-particle rubbing | Impact force (G-force, drop height) |
| Affected by G-force | Moderate influence | Strong influence |
| Affected by residence time | Strong influence (more time = more attrition) | Moderate influence |
| Example materials | Crystalline salt, sugar, catalysts | Spray-dried powders, granules, agglomerates |
Why This Matters
Attrition is often an overlooked source of fines generation that accumulates into significant quality and cost problems:
- Product contamination — Attrition fines are typically much smaller than the target product. In a classification operation, these fines pass through the screen and contaminate the undersize fraction. In a safety screening operation, they pass through as part of the accepted product, potentially affecting appearance, flowability, or dissolution rate.
- Screen blinding — Attrition fines are often electrostatically charged and can adhere to screen wires, accelerating blinding. This is especially problematic on fine screens (100+ mesh) where the wire diameter is small and the surface-to-volume ratio of the fines promotes adhesion.
- Dust generation — In open or vented vibratory screeners, attrition fines become airborne dust. This creates housekeeping problems, potential health hazards, and may require dust collection systems that add cost and complexity to the installation.
- Yield loss — Material lost to attrition is material that no longer meets the target product specification. While the percentage may seem small (0.5–2% per pass is common), it compounds across multiple screening passes and over continuous production hours.
Related Glossary Terms
- Friability — Particle breakage tendency, related but distinct from attrition
- G-Force — The acceleration force that influences attrition rate
- Residence Time — Longer residence time increases total attrition exposure
- Blinding — Screen clogging worsened by attrition fines
- Undersize / Fines — The fraction that increases due to attrition
- Elliptical Motion — Gentle motion that minimizes attrition
Attrition FAQs
What is attrition in vibratory screening?
Attrition is the gradual wearing of particle surfaces during screening, creating fine dust particles through rubbing and contact. Unlike friability (sudden breakage), attrition is progressive surface erosion. These fines can contaminate products, cause screen blinding, and reduce yield over time.
How is attrition different from friability?
Friability involves particles shattering into large fragments under impact, while attrition produces very fine dust through surface rubbing. A hard crystalline material like salt is non-friable but still generates dust through attrition. Both create unwanted fines, but attrition is managed by reducing residence time and bed depth, while friability is managed by reducing G-force and impact.
Minimize Attrition with Proper Screener Configuration
ScreenerKing's application engineers can help you configure your vibratory screener to minimize attrition while maintaining throughput and efficiency. We offer adjustable G-force settings, multiple motion options, and screen materials selected to reduce particle wear. Compatible with Sweco, Kason, Midwestern, Cleveland Vibratory, Russell Finex, and Rotex.
