Frequency in vibratory screening is the number of vibration cycles per unit of time at which the vibratory motor rotates and the screen surface oscillates, directly influencing particle stratification, separation efficiency, and material conveyance. It is measured in RPM (revolutions per minute) or Hz (cycles per second) and works in combination with amplitude to define the screener's motion characteristics.
Most round vibratory separators operate at either 1,200 RPM (20 Hz) or 1,800 RPM (30 Hz) on 60 Hz electrical power. Higher frequency provides more vibration cycles per second, giving particles more opportunities to contact screen openings and pass through. This is particularly beneficial for fine screening. Lower frequency combined with higher amplitude provides the aggressive throw needed for coarse, heavy, or wet materials.
Frequency Ranges for Vibratory Screening
| Frequency | RPM (60 Hz power) | Best For |
|---|---|---|
| Low | 900–1,200 RPM | Coarse materials, heavy feeds, dewatering |
| Standard | 1,200–1,800 RPM | General-purpose screening, most applications |
| High | 1,800–3,600 RPM | Fine powders, precision classification |
Why This Matters in Vibratory Screening
- Stratification rate — Higher frequency increases the rate at which fine particles migrate to the bottom of the material bed (stratify), putting them in contact with the screen surface for separation.
- Fine screening performance — Fine powders benefit from high frequency because more vibration cycles per second mean more particle-to-screen contacts.
- Amplitude trade-off — At a given motor power, increasing frequency reduces amplitude. Operators must balance these parameters for optimal results.
Related Glossary Terms
- Amplitude — The complementary vibration parameter
- Lead Angle — Determines material travel direction
- Motion Generator / Vibratory Motor — Sets the operating frequency
- Stratification — The process improved by proper frequency
- Screening Efficiency — Affected by frequency selection
Frequency FAQs
What is frequency in vibratory screening?
The number of vibration cycles per second or minute. Most round separators operate at 1,200–1,800 RPM. Higher frequency improves fine screening; lower frequency with higher amplitude suits coarse materials.
Can I change the frequency on my screener?
Standard motors run at fixed speeds. A variable frequency drive (VFD) allows infinite adjustment of vibration speed for optimization.
ScreenerKing Separators — Optimized for Your Application
All ScreenerKing vibratory separators feature adjustable counterweights for amplitude tuning. VFD-compatible motors available for frequency optimization.