Feed rate in vibratory screening is the rate at which material is introduced to the screener, measured in pounds per hour (lbs/hr) or tons per hour (tons/hr), and is a primary variable controlling screening efficiency, material bed depth, and product quality. Along with G-force and mesh size, feed rate is one of the three most important operating parameters on any vibratory separator.
Material enters the screener through a center feed inlet (on round separators) or an end hopper (on linear screeners). The rate of introduction determines how much material sits on the screen surface at any given moment. When feed rate is properly matched to the screener's capacity, the material bed is thin enough for undersize particles to stratify downward and reach the screen openings, yet thick enough to keep the full screen area productive. Vibratory separators from ScreenerKing, Sweco, Kason, Midwestern Industries, and other manufacturers all have rated feed capacities that depend on screen diameter, mesh size, and material characteristics.
Typical Feed Rate Ranges by Screener Size
| Screener Diameter | Screen Area (sq ft) | Coarse (4–30 mesh) | Medium (30–100 mesh) | Fine (100–325 mesh) | Ultra-Fine (325–500 mesh) |
|---|---|---|---|---|---|
| 18" | 1.2 | 200 – 600 lbs/hr | 100 – 400 lbs/hr | 50 – 200 lbs/hr | 20 – 100 lbs/hr |
| 24" | 2.4 | 500 – 1,500 lbs/hr | 200 – 800 lbs/hr | 100 – 400 lbs/hr | 50 – 200 lbs/hr |
| 30" | 4.0 | 800 – 2,500 lbs/hr | 400 – 1,500 lbs/hr | 200 – 700 lbs/hr | 80 – 350 lbs/hr |
| 48" (SiftPro 48) | 10.5 | 2,000 – 6,000 lbs/hr | 1,000 – 4,000 lbs/hr | 500 – 2,000 lbs/hr | 200 – 800 lbs/hr |
| 60" (SiftPro 60) | 17.0 | 3,500 – 10,000 lbs/hr | 1,500 – 6,000 lbs/hr | 700 – 3,000 lbs/hr | 300 – 1,200 lbs/hr |
Note: Ranges are approximate for dry powders and granules with bulk density of 30–60 lbs/cu ft. Actual rates vary with bulk density, particle size distribution, moisture content, and target efficiency.
Why This Matters
Feed rate is the operating variable most commonly responsible for screening problems in production:
- Overfeeding degrades efficiency — Excessive feed rate creates a thick material bed that prevents fine particles from reaching the screen surface. Undersize particles are swept over the screen with the oversize discharge (carry-over), reducing screening efficiency and contaminating the oversize product.
- Underfeeding wastes capacity — A feed rate that is too low means the screener is not being fully utilized. While efficiency will be high, the operation pays for screening capacity it is not using. Increasing feed rate to the optimal point maximizes productivity.
- Surge feeding causes problems — Inconsistent feed rate (surges and starves) is worse than a steady rate that is slightly too high. Surges momentarily overwhelm the screen, causing spikes of carry-over, while starves waste capacity. A consistent, metered feed is essential for stable operation.
- Feed rate interacts with every other parameter — Increasing G-force allows higher feed rates. Finer mesh requires lower feed rates. Higher moisture content reduces the tolerable feed rate. These interactions must be considered together.
Related Glossary Terms
- Material Bed Depth — The layer thickness on the screen, directly controlled by feed rate
- Residence Time — How long material stays on the screen, inversely related to feed rate
- Throughput / Capacity — The maximum feed rate at which the screener meets efficiency targets
- Carry-Over — Undersize in the oversize fraction, caused by excessive feed rate
- Screening Efficiency — The metric that degrades when feed rate exceeds capacity
- Screen Loading — Weight of material per unit area, a function of feed rate
Feed Rate FAQs
What is feed rate in vibratory screening?
Feed rate is the mass of material introduced to a vibratory screener per unit of time, typically measured in pounds per hour or tons per hour. It determines the material bed depth and directly affects screening efficiency. Too high a feed rate creates a thick bed that prevents undersize particles from reaching the screen, reducing efficiency. Too low a feed rate underutilizes capacity.
How do I determine the correct feed rate for my vibratory screener?
The correct feed rate depends on screener diameter, mesh size, material bulk density, particle size distribution, and target efficiency. Start at a moderate rate and adjust while monitoring the oversize discharge for carry-over of undersize particles. ScreenerKing's engineering team can provide specific feed rate recommendations for your application.
Maximize Feed Rate with the Right Screener
ScreenerKing vibratory screeners — the SiftPro, SiftPro 48, and SiftPro 60 — are engineered for maximum throughput at your target efficiency. Need to increase feed rate? Our engineers can recommend screen mesh, G-force settings, and machine configurations to optimize your operation. 30+ years of experience from Houston, TX.
