How it works
Screening separates particles by whether they can pass an aperture. Material is presented to a screening surface; particles smaller than the opening have a chance to pass to the undersize (fine) stream, while larger ones are retained as oversize (coarse). The chance of passing is not a clean step at the mesh size — it depends on how often a particle meets an aperture, its orientation, and near-mesh particles that only just fit.
The result is a smooth grade efficiency (partition) curve: the fraction of each size class that reports to the coarse stream. Two numbers summarize it — the cut size (where half the material goes each way) and the sharpness (how steeply the curve rises around the cut). High sharpness means a clean separation; low sharpness leaves near-size material in the wrong fraction.
Before a particle can be tested at all, it must reach the deck: the bed stratifies under vibration, fines percolate downward through the coarse layer, and the transport velocity sets how long each particle stays on the screen. Real screens lose sharpness to blinding, overloading, and cohesive or moist material — near-size particles lodge in the apertures, and adhering fines ride along with the coarse fraction instead of passing.
The model
Dyssol Pro splits the feed at the population level: for every particle size class it computes the fraction reporting to the coarse stream, with the fine stream taking the remainder — mass-conserving, at every time point of the dynamic flowsheet.
The split is governed by the separation curve — the same partition curve you would measure by sampling both product streams. Its two defining quantities are the cut size, where feed material divides equally between the outlets, and the sharpness, which sets how steeply the curve rises around that cut; both may change over time, so a screen whose performance drifts across a campaign is represented as it actually behaves.
Because the shape of the curve is free — steep or shallow, symmetric or with a fines bypass into the coarse stream — the unit reproduces measured screening behavior from coarse scalping decks to fine control sieves. Dyssol Pro resolves the complete particle size distribution on both outlets, which is what makes closed mill–screen circuits with recycle predictive rather than guesswork.
Equipment this model can represent
Any screening duty where a size cut splits the feed into oversize and undersize.
Vibrating / shaker screens
Inclined or horizontal decks vibrated to stratify and transport material across the mesh.
Tumbler / gyratory screens
Gentle gyratory motion for fine, accurate classification.
Trommel (drum) screens
A rotating cylindrical screen for robust scalping and washing duty.
Ultrasonic-assisted fine screens
High-frequency excitation of the mesh to keep fine, cohesive powders from blinding.
Typical engineering studies
What teams investigate with the screen model.
Cut and split prediction
Predict the oversize/undersize split and both product PSDs for a given cut size and sharpness.
Closed mill–screen circuit
Return oversize to a crusher and study recycle load and product PSD across the loop.
Cut & sharpness sensitivity
Map how cut size and sharpness move misplacement and yield.
Partition-curve fitting
Fit the separation curve to a measured partition curve, then use it predictively.
Cut optimization
Optimize the cut to balance product quality against recovery across the connected process.
Technical FAQ
How do I choose the right screen mesh size?
The mesh opening starts at roughly the target cut size and is then corrected for near-size load, particle shape, and expected blinding — in practice the effective cut sits somewhat below the nominal opening. In Dyssol Pro you set the cut size in the screen unit, predict the split and both product PSDs, and iterate until the product spec is met before committing to a mesh.
Why is my vibrating screen blinding?
Blinding comes from near-size particles wedging in the apertures or sticky, moist fines coating the mesh; the countermeasures are aperture shape, deck motion, ultrasonics, and drier feed. Its process signature is a blunted cut — in Dyssol Pro you represent that as a reduced effective sharpness and quantify what the degraded separation costs downstream.
How can I improve screening efficiency?
Efficiency needs enough aperture encounters per particle — sufficient area, controlled bed depth, the right transport velocity — and a feed that is not overloading the deck. In Dyssol Pro you vary cut size and sharpness inside the connected circuit, so the improvement is judged with recycle effects included rather than on the screen alone.
What causes too much good product in the oversize fraction?
Undersize retained in the coarse fraction means the effective cut sits too coarse or the separation is too blunt — typically overloading, too little screening length, or partially blinded apertures. In Dyssol Pro you move the cut or sharpen the separation curve and read directly how much good product returns to the right stream.
How does moisture content affect screening performance?
Surface moisture makes fines adhere to coarse particles and to the mesh, so the cut blunts and undersize reports coarse; most materials have a critical moisture band where screening is at its worst. In Dyssol Pro you model the upstream drying in the flowsheet to find a safe moisture window and represent the residual effect as a reduced sharpness.
How do vibration frequency and amplitude affect separation?
They set stratification and transport: enough acceleration to loosen the bed so fines reach the deck, but not so much that particles fly over apertures without being tested — most decks run at a few g. Their net result is a cut size and sharpness, which is exactly how the screen enters a Dyssol Pro flowsheet, calibrated to the measured performance.
How can I reduce screen wear when processing abrasive particles?
Wear is fought with harder or resilient deck materials such as polyurethane or rubber, lower impact angles, and taking the abrasive coarse load out early. Dyssol Pro computes the split and the mass loads each deck actually sees, so wear parts are specified against the real duty.
What is the difference between scalping, classification, and dedusting screens?
They differ only in where the cut sits relative to the product: scalping removes a small coarse tail, classification cuts inside the distribution, and dedusting takes fines off the bottom end. In Dyssol Pro all three are the same screen unit with a different cut size and sharpness.
How do I size a screen for a powder processing line?
Deck area follows from the material-specific capacity per unit area, the fraction of near-size particles, and the efficiency you are willing to accept — the near-size load is what really drives area. Dyssol Pro supplies the duty that sizing depends on: the split and the mass loads at every operating point of the line, so the area calculation starts from the right numbers.
How can I model screen separation efficiency?
Separation efficiency is described by the grade-efficiency (partition) curve — the fraction of each size class reporting to the coarse stream — summarized by cut size and sharpness. That curve is the core of Dyssol Pro’s screen unit: set it or fit it to data, and the unit returns the size-resolved split and both product PSDs inside the flowsheet.
How can I prevent screen clogging with sticky powders?
Sticky powders need conditioning — drier feed, flow aids, heated or coated decks — plus aggressive anti-blinding measures such as ultrasonic excitation. In Dyssol Pro you study the upstream drying and handling that reduce cohesion, and check what cut remains realistically achievable once the feed is conditioned.
Why is screen throughput lower than expected?
Falling throughput usually means the effective open area is shrinking — blinding, overloading, or moist feed — or the feed carries more near-size material than the design assumed. In Dyssol Pro you vary the feed PSD and the effective separation independently, which tells you whether the cause is the process or the machine.
How does particle shape affect screening accuracy?
Elongated and flaky particles pass an aperture by their intermediate dimension, so they classify at a different size than a sieve analysis suggests and smear the cut. In the flowsheet this appears as a reduced sharpness, so in Dyssol Pro you calibrate the separation curve to measured data and the shape effect is carried automatically.
How can I reduce fines in the oversize stream?
Fines report coarse when they never reach the deck — too deep a bed, too fast a transport, or moist, agglomerated feed — so the fix is stratification and residence time as much as the mesh. In Dyssol Pro you tune the separation curve and quantify the fines-in-oversize fraction against cut and sharpness directly.
How do I optimize screen inclination angle?
Inclination trades capacity against accuracy: a steeper deck moves material faster, giving fewer aperture encounters and a coarser, blunter cut; a flatter deck cuts finer but carries a deeper bed. Its net effect lands in the cut size and sharpness, which you calibrate in Dyssol Pro from the screen’s measured performance at each setting.
What causes product loss through the undersize stream?
Coarse product leaks to undersize when the effective cut is finer than intended or the separation is blunt — often worn or oversized apertures. In Dyssol Pro you shift the cut or sharpen the curve and read the recovered product straight off the partition curve.
How can I select between ultrasonic and mechanical screen cleaning?
Ultrasonics excel on fine, dry, blinding-prone powders; ball trays and brushes are the robust choice for coarser, tougher duties. Dyssol Pro defines the separation the process must maintain — the cut and sharpness the product spec requires — so the cleaning system is chosen to protect exactly that performance.
How do I improve screening of cohesive powders?
Cohesive powders screen better with drier feed, flow aids, ultrasonic decks, and a shallow bed so agglomerates break up and fines actually reach the apertures. In Dyssol Pro you model the upstream conditioning and test what effective cut and sharpness are achievable before promising a product spec.
How can I measure screening efficiency in production?
Sample feed, oversize, and undersize, sieve each, and compute the recovery of every size class to the coarse stream — that gives the partition curve, the honest measure of screen performance. Dyssol Pro then fits its separation curve to that measurement, turning the audit into a validated unit you can use predictively.
How can I model screen performance using partition curves?
The partition (Tromp) curve is the complete description of a screen: the fraction of each size class reporting coarse, characterized by cut size and sharpness. Dyssol Pro’s screen unit is built on exactly this curve — fit it to your measured data and the unit reproduces the screen inside the connected flowsheet.