How Does Screening Work?
May 4, 2026SUMMARY
- Screen blinding and pegging reduce effective open area and limit screening efficiency.
- Blinding occurs when fines cover the screen surface; pegging (or plugging) occurs when near-size particles lodge inside apertures.
- Operational factors such as bed depth, feed distribution, vibration, moisture, and aperture design influence buildup.
- Addressing the issues of blinding and pegging improves throughput, reduces recirculating load, and stabilizes plant performance.
What Causes Screen Blinding and Pegging?
Screen blinding occurs when fine material accumulates across the screen surface and blocks apertures. Pegging—sometimes referred to as plugging—occurs when near-size particles become lodged inside the openings themselves.
Both conditions reduce effective open area and prevent undersized material from passing efficiently.
Blinding and pegging are typically driven by the following:
- Excessive material bed depth
- High concentrations of near-size particles
- Inadequate or inconsistent vibration
- Moisture or cohesive fines
- Improper aperture size or geometry
- Media material not suited to the application
Understanding the root cause is essential before applying corrective measures.
10 Practical Ways to Prevent Screen Blinding and Pegging
1. Optimize Material Bed Depth
Excessive bed depth limits stratification and reduces the exposure of fines to the screen surface. When the material layer is too deep, smaller particles may never reach the apertures before exiting the deck.
Maintaining a consistent and controlled feed rate allows proper stratification and improves probability of passage. Balanced bed depth is one of the most influential factors in preventing buildup.
2. Improve Feed Distribution Across the Screen Deck
Uneven feed presentation creates localized overloading, where certain areas of the screen carry more material than others. These overloaded zones are often where blinding and pegging begin.
Proper feed distribution across the full width of the screen deck maximizes effective open area and reduces concentrated buildup.
3. Adjust Screen Vibration Parameters
Vibration directly influences particle movement and stratification.
If amplitude is too low, particles may not lift and resettle effectively, encouraging fines to accumulate on the surface. If vibration is inconsistent, material can compact and restrict passage.
Proper stroke and motion characteristics help dislodge lodged particles and reduce the likelihood of persistent pegging.
4. Match Aperture Size and Geometry to the Application
Aperture size significantly affects pegging risk.
When the feed contains a high percentage of near-size material—particles very close to the intended cut size—those particles are more likely to lodge inside the openings.
In these cases, geometry becomes just as important as nominal size. Square, slotted, and other aperture shapes interact differently with near-size material. Selecting an aperture design suited to the feed characteristics can greatly reduce lodging.
The solution is not always a larger opening, but often a better-matched geometry.
5. Increase Effective Open Area Where Possible
Open area determines how many opportunities particles have to pass through the screen surface.
Higher effective open area increases probability of passage and reduces the likelihood that fines remain trapped in the oversize stream.
In some applications, buildup problems are related less to aperture size and more to insufficient effective screening area. This problem is often due to design limitations such as wide panel borders or incorrect panel material choice.
6. Manage Moisture and Water Application
Moisture is a major contributor to screen blinding. Excessive moisture in dry screening applications can cause cohesive fines to smear across the screen surface, preventing proper dispersion and cleaning.
In cases of dry screening where the material being screened is moist or sticky, using highly flexible screen media with high open area can help break apart surface buildup and reduce blinding.
7. Address Near-Size Material in the Feed
Pegging is most common when a large percentage of the feed material is close in size to the aperture dimension. When near-size material dominates, even properly selected apertures may experience lodging.
Monitoring feed gradation and understanding upstream material behavior can help identify when near-size concentration is driving pegging issues.
8. Consider Flexible or Self-Cleaning Media
Rigid screening surfaces do not always release lodged particles easily. Flexible or dynamic media can help dislodge near-size particles and reduce long-term pegging, particularly in fine sizing applications.
In environments prone to buildup, selecting media designed to promote particle release can improve consistency without altering aperture size.
9. Monitor Wear Before It Reduces Effective Open Area
As screen media wears, aperture edges can round or deform, increasing the likelihood of larger particles getting lodged within openings.
Routine inspection and timely replacement prevent gradual efficiency losses from turning into persistent buildup problems.
10. Match Media Material to Operating Conditions
The material of the screen media influences how the surface behaves under vibration and load.
Different media materials vary in the following attributes:
- Flexibility and elasticity
- Resistance to particle adhesion
- Impact absorption
- Long-term aperture stability
- Wear profile consistency
In fine or wet applications, more-flexible media may help release near-size particles that would otherwise remain lodged in rigid openings. In highly abrasive environments, more durable materials help maintain aperture integrity over time.
In dry screening applications with sticky material, media made with flexible materials and high open area characteristics will yield the best results.
Matching media material to operating conditions improves screening stability and reduces the likelihood of persistent blinding or pegging.
Why a Reduction in Blinding and Pegging Improves Overall Plant Performance
When blinding or pegging reduces effective open area, undersized material remains in the oversize discharge stream longer than intended.
This can lead to the following:
- Increased recirculating load
- Reduced available throughput
- Higher energy consumption
- Unstable material flow
- More frequent maintenance interruptions
- Additional strain on crushers
Improving screening efficiency stabilizes material flow through the plant and reduces unnecessary reprocessing. In many operations, resolving buildup issues on the screen deck can unlock capacity without adding equipment.
If you need help with combatting screen blinding or pegging, contact Polydeck to learn how our solutions can help.
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