To select the right exciting force for a VIBRATING SCREEN, do not choose the exciter only by its nominal kN rating. The correct value depends on total vibrating mass, material load, required amplitude, operating frequency, deck inclination, feed rate, particle size, moisture, and screening objective. For an unbalanced rotating exciter: F = m × r × ω². The objective is sufficient acceleration for the required screening performance without excessive impact, bearing load, structural stress, or resonance.
Exciting force is a mechanical input; screening performance is a system response.
Force changes with the square of angular velocity — speed has disproportionate influence.
Coarse screening favours larger amplitude and lower speed; fine screening favours smaller amplitude and higher speed.
Beyond an optimum, more force reduces residence time and screening efficiency.
Increasing amplitude can shorten bearing service life.
Support structure natural frequency should be at least 2.5× operating frequency.
Field verification reveals problems a nameplate cannot show.
| Item | Description |
|---|---|
| Function | Periodic force that moves the screen box |
| Formula | F = m × r × ω² |
| Application | Coarse scalping, fine screening, dewatering, coal preparation |
| Service Life | Limited by bearing capacity, amplitude, and structural stress |
| Selection Basis | Screen mass, material load, amplitude, frequency, aperture, duty |
Exciting force is the periodic force generated by the vibrating mechanism and transferred to the screen structure. In mining vibrating screens, it is typically produced by rotating eccentric masses. The force is a mechanical input — it is not the same as screening performance, which depends on the complete dynamic system.
For an unbalanced rotating mass, the centrifugal force relationship is:
F = m × r × ω²
Where F is centrifugal or exciting force, m is effective unbalanced mass, r is eccentric distance, and ω is angular velocity.
Because angular velocity is squared, a small speed change produces a large force change. However, the resulting screen response also depends on machine mass, support stiffness, damping, frequency, and structural configuration.
The relationship chain is:
Exciting force → machine response → amplitude and acceleration → particle movement → screening performance
Changing one parameter affects the others.
Correct stratification. Adequate excitation separates fines from coarse material on the deck.
Effective transport. Material moves across the deck at the required rate.
Reduced blinding. Sufficient aperture activity keeps openings functional.
Bearing protection. Correct amplitude and eccentric mass protect bearing life.
Structural integrity. Operating within mechanical limits avoids dynamic stress.
Resonance avoidance. Correct frequency separation prevents excessive vibration.
Exciting force selection depends on the screening duty. Common duties include primary scalping, coarse classification, fine screening, wet screening, dewatering, sizing of crushed aggregate, iron ore classification, coal preparation, and mineral processing.
Screening sits between CRUSHING and GRINDING in the comminution circuit.
| Duty | Amplitude | Frequency | Reason |
|---|---|---|---|
| Coarse scalping | Larger | Lower | High particle inertia |
| Fine screening | Smaller | Higher | More aperture contacts |
| Wet sticky material | Moderate | Moderate | Anti-blinding, transport balance |
| Dewatering | Moderate | Moderate | Drainage and residence time |
| Duty | Key Priority | Selection Focus |
|---|---|---|
| Primary scalping | Transport and stratification | Large amplitude, heavy-duty bearings |
| Fine screening | Aperture accuracy | Small amplitude, high frequency |
| Wet screening | Blinding control | Balanced motion, PU media |
| Dewatering | Drainage rate | Force and residence time balance |
| Coal preparation | Controlled direction | Synchronized dual-shaft |
| Aggregate sizing | Throughput | Standard eccentric configuration |
| Industry | Typical Duty | Key Exciting Force Concern | Selection Focus |
|---|---|---|---|
| Iron Ore | Coarse classification, dewatering | Bearing load, amplitude | Heavy-duty, large amplitude |
| Coal | Preparation, dewatering | Synchronization, sealing | Dual-shaft geared |
| Aggregates | Scalping, sizing | Impact load, transport | Heavy-duty bearings |
| Gold | Fine screening | Frequency, amplitude | High-frequency, low amplitude |
| Copper | Classification | Load capacity | Heavy-duty configuration |
| Silica Sand | Fine screening | Aperture accuracy | High-frequency arrangement |
| Phosphate | Wet screening | Sealing, blinding | Balanced motion, PU media |
| Lead-Zinc | Classification | Load capacity | Heavy-duty configuration |
Pub Thời gian : 2026-10-06 09:03:17 >> danh mục tin tức
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