A vibrating screen is the machine in a crushing and screening plant that separates material into fractions according to particle size. However well the crushers work, the screen is the final stage that determines saleable product: a wrongly selected or badly adjusted screen causes mixing between fractions, unnecessary recirculating load and overloading of the crushers.
In this guide you will find the working principle of vibrating screens, the differences between inclined (standard) and horizontal screens, the parameters that determine screening efficiency, screen media selection and the maintenance practices highlighted in manufacturers’ manuals.
How Does a Vibrating Screen Work?
The screen body sits on springs or rubber mounts and is vibrated by a vibrator mechanism (an eccentric weighted shaft or vibrating motors). As the vibration moves material along the screen surface, it does two things at once: stratification (coarse particles moving to the top and fine particles to the bottom) and probability of passage (fine particles passing through the openings after repeated contact). Screening efficiency depends on how well these two processes take place.
Inclined (standard) screen
- Usually installed at an inclination of 15–25°; makes a circular vibrating motion.
- Carries material quickly with the help of gravity; gives high capacity for the same area.
- The most common screen type in aggregate plants; can be built with 2–4 decks.
- Typical operating acceleration is about 3.5–4.5 g.
Horizontal screen
- Installed close to horizontal (0–5°); makes a linear or elliptical (triple-shaft) motion.
- Needs a lower installation height; an advantage in mobile and modular plants.
- Material stays on the surface longer; gives superior performance in precise separation and wet screening (with spray bars).
- Typical operating acceleration is about 4.5–5.5 g.
Parameters That Determine Screening Efficiency
| Parameter | Effect | Practical rule |
|---|---|---|
| Stroke (amplitude) | Provides stratification and prevents pegging | Large stroke + low speed for coarse separation; small stroke + high speed for fine separation |
| Speed (rpm) | Number of times a particle contacts the screen surface | Run at the manufacturer’s design speed |
| Inclination | Material velocity and bed depth | As inclination increases, capacity increases but efficiency may fall |
| Bed depth | In a very deep bed, fine particles cannot reach the screen | At the discharge end, bed depth should not exceed about 3–4 times the aperture |
| Open area | Throughput capacity | High for wire mesh, lower for polyurethane/rubber |
| Feed distribution | Full use of the screen width | Material should be fed evenly across the full width of the screen |
| Moisture and clay | Blinding, pegging | Washing, self-cleaning wire or heated solutions |
Choosing Screen Media
Screen media is the most frequently replaced part of a screen and the part that most affects its efficiency.
- Woven steel screen wire: The highest open area and capacity; relatively short wear life. Economical with dry, moderately abrasive material. For details, see our screen wire guide.
- Self-cleaning screen wire: Reduces blinding with wet, sticky material because the wires vibrate independently. See self-cleaning screen wire.
- Polyurethane modular panels: Long wear life, low noise, ideal for wet screening; lower open area.
- Rubber panels: High durability with impact and coarse material (top deck, under the grizzly).
For a comparison of polyurethane and rubber, our article on polyurethane vs rubber screen panels will help.
Installation and Commissioning
- The screen must be completely level in the lateral (cross) direction; on a tilted screen, material collects at one edge, efficiency falls and wear concentrates on one side.
- Springs or mounts must carry equal load, and a broken spring must be replaced immediately; a single broken spring leads to cracks in the body.
- Enough clearance must be left between the screen body and the chutes, feed box and surrounding structures; the vibrating body must not touch any fixed structure.
- At first start-up, stroke and direction of motion are measured (stroke card or vibration meter) and compared with the design values.
Maintenance: Practices That Extend Screen Life
Screen media and tensioning
- Screen wires must be at the correct tension. A slack wire slaps against the support bars underneath and breaks quickly. Tension should be increased equally from both sides.
- Newly fitted wires bed in during the first hours of operation; tension should be checked again after the first shift.
- When the rubber caps (bucker-up rubbers) on the support bars wear, the wire sits directly on metal and is cut; the caps should be checked regularly.
Vibrator and bearings
- Bearing greasing is the most critical item in screen maintenance. Grease lines must be sound and the grease must reach the bearing.
- A slight trace of grease around the labyrinth seals is desirable: grease overflowing slightly from the seals protects the bearing against dust and moisture.
- On oil-lubricated vibrators, oil level and temperature should be monitored and the oil changed at the interval specified by the manufacturer.
- Check vibrator belts and cardan shaft/coupling connections.
Body and bolts
- Screen bodies are usually joined with huck bolts (lockbolts) rather than welds; a loose connection is the start of a crack.
- Side plates and cross members should be inspected periodically for cracks; welding on a screen body is not recommended without the manufacturer’s approval.
Weekly Screen Inspection Round
- Screen media: broken wires, holed panels, excessively worn areas, blinding.
- Tensioning: slack wires and edge fixings.
- Springs/mounts: broken springs, crushed mounts, even seating.
- Bearings: temperature, noise, grease traces.
- Stroke and motion: uneven or “rocking” motion (unequal stroke).
- Feed box and chutes: wear, liners, even distribution.
- Body: cracks, loose bolts.
Troubleshooting Table
| Symptom | Possible cause | Solution |
|---|---|---|
| Mixing between fractions (fines in the product) | Overfeeding, deep bed, blinded screen | Reduce the feed, increase screen area, clean/replace the media |
| Blinding | Wet/clayey material, unsuitable aperture, insufficient stroke | Self-cleaning wire, washing, increase stroke |
| Material collecting at one edge | Screen not level, feed from one side | Level the screen, use a feed distributor |
| Wires breaking frequently | Slack tension, worn support caps, heavy impact | Correct tensioning, renew the caps, add an impact plate |
| Bearing overheating | Too little/too much grease, contamination, belt tension | Correct the greasing programme, check the seals |
| Unequal stroke, rocking | Broken spring, loose weight, cracked body | Check springs and weights, inspect the body |
Frequently Asked Questions
Should I choose an inclined or a horizontal screen?
An inclined screen is more suitable for high capacity and standard aggregate fractions; a horizontal screen for low installation height, precise separation or wet screening.
How is screen capacity calculated?
Screen area is calculated with correction factors such as aperture size, the proportion of undersize in the feed, the half-size proportion, deck position, inclination, moisture and the required efficiency. For an accurate calculation, consult the manufacturer together with the plant flowsheet.
When should screen wire be replaced?
It should be replaced when the wire diameter has thinned markedly, the apertures have grown (so the product specification is no longer met) or wires break. Because aperture growth directly spoils product quality, regular measurements should be taken.
Calculating Screen Area: Understanding the Logic
The basic idea of screen area calculation is that a certain amount of material can pass through a given aperture per unit area (basic capacity). This basic value is multiplied by correction factors for actual conditions:
- Undersize proportion: The proportion of feed smaller than the aperture.
- Half-size proportion: The proportion smaller than half the aperture; if high, screening is easier.
- Oversize proportion: Coarse material increases bed depth.
- Deck position: Lower decks receive less material, already screened by the upper decks, but work less efficiently.
- Inclination, moisture, washing, aperture shape and open area.
- Required efficiency: A 90–95% efficiency target needs markedly more area than an 80% target.
A practical rule: along with crusher capacity, screen area is the equipment most often undersized. If the screen area is insufficient, however well the crusher works, products mix and the recirculating load increases.
Adjusting Stroke and Speed
On eccentric weighted vibrators, stroke is adjusted by changing the position of the weights (or weight plates); speed is changed by changing pulleys or with a frequency inverter. General principles:
- For coarse separations (top deck, above 40 mm), a large stroke and low speed provide enough energy for particle stratification and movement.
- For fine separations (sand screen), a small stroke and high speed give more frequent contact between particles and the screen surface.
- When stroke is increased, bearing loads and body stresses also increase; the limits allowed by the manufacturer must not be exceeded.
- After adjustment, measure the stroke at the four corners of the body; unequal stroke indicates weight imbalance or a spring problem.
Wet Screening
Washing material with spray bars on the screen removes clay and dust and gives a clean product. In wet screening:
- Spray bars should be positioned along the screen at the points where the material tumbles,
- Water pressure and flow should be adjusted to how dirty the material is,
- Polyurethane panels provide wear resistance and low noise with water,
- The undersize sand and muddy water should be sent to a sand washer or water recovery system. See screw sand washer.
Spare Parts Stock
- Always in stock: At least one set of screen media (wire or panels) for each deck, tensioning hooks and bolts, support bar rubber caps, springs, vibrator belts, grease.
- Critical spares: A complete vibrator unit or bearing set, cardan shaft/coupling, motor.
- Planned: Feed box liners, side plate protectors, huck bolt set.
Keeping a spare vibrator unit allows the screen to be back in service within hours after a bearing failure.
An Example from the Field: Capacity Problems on a Sand Screen
At an aggregate plant, the 0–4 mm sand screen kept blinding and the sand contained particles over 4 mm. It was found that the screen wires were not properly tensioned, the support caps were worn and the screen was running below its design speed. The speed was corrected by changing pulleys, the plant switched to self-cleaning wire and the tensioning procedure was added to the shift checklist. Sand quality came within specification and the recirculating load fell. This example shows that most screening problems come from simple setting and maintenance shortcomings.
Pre-Purchase Checklist
- Are the feed size distribution and peak capacity known?
- How many fractions will be produced, and is the number of decks sufficient?
- Will screening be dry or wet?
- Is there a risk of blinding because of moisture and clay?
- Is installation height limited (need for a horizontal screen)?
- Have access and platforms for changing screen media been planned?
- What are the dust and noise requirements?
More Questions
Why is material running back or bouncing on the screen?
Reversed direction of motion (vibrator rotation direction), excessive stroke or the inclination of the body can cause this problem. The direction of rotation and stroke should be checked.
Which is more economical, polyurethane panels or wire mesh?
Polyurethane panels are more expensive but last much longer; taking replacement frequency and downtime costs into account, they are often more economical in wet and abrasive applications. Wire mesh has the advantage in dry applications needing high capacity.
A crack has formed in the screen body; can it be welded?
Uncontrolled welding on screen bodies can create new stress concentrations and larger cracks. Repairs should be carried out according to the manufacturer’s procedure and with a suitable welding method.
Vibrating Screen Motors and Drive Types
| Drive Type | How It Works | Typical Use |
|---|---|---|
| Eccentric shaft + belt-driven motor | An electric motor turns an eccentric shaft with unbalance weights via V-belts; circular motion results | Inclined screens |
| Two vibrator motors | Two counter-rotating unbalanced motors produce linear motion | Dewatering and horizontal screens, feeders |
| Oil-lubricated exciter unit | Unbalance weights synchronised by gears, running in an oil bath | Large horizontal screens |
Screen motor power is set by the manufacturer according to screen size, number of decks and vibration characteristics. On screens with vibrator motors, the weight settings of the two motors must be equal and their directions of rotation wired correctly. For belt selection and tensioning on belt drives see our belt and pulley calculation guide, and for motor maintenance our electric motors guide.
Vibrating Screen Bearings
On vibrating screens, bearings run at high speed under loads that constantly change direction. Screen-specific spherical roller bearings with greater internal clearance (C3/C4) and reinforced cages are therefore generally used. When replacing a bearing, match not only the basic number but also the screen-type suffixes; otherwise the bearing soon overheats and fails. For details see our bearing numbers and sizes and bearing selection guides.
Factors That Determine Vibrating Screen Prices
- Screen size (width × length) and number of decks,
- Inclined or horizontal type and drive system,
- Motor power and the design of the vibrating mechanism,
- Screen media type (screen wire, polyurethane or rubber panels) (screen wire sizes),
- Body material, side plate thickness and build quality,
- Extras such as spray bars, dust covers, support frame and platforms.
For a fair comparison, quotes should be prepared on the same material, capacity and fraction assumptions.
Screening Solutions from CSP Mühendislik
CSP Mühendislik manufactures standard (inclined) screens and horizontal screens, and supplies vibrating screen spare parts such as screen wire, polyurethane panels, springs, vibrators and bearings. Contact us to improve screening efficiency at your plant.
