A feeder mounted directly under a hopper's discharge opening runs under the heaviest duty: it holds back a column of material, absorbs impact loads when the hopper is filled, and must deliver a uniform metered feed further down the line. A sizing mistake here is the most costly — a feeder undersized on capacity or tray strength either can't handle the volume or fails early.
What you need to know before sizing
- Hopper chute angle and tray angle — the datasheet capacity is given for 4° or 8°.
- Maximum material lump size — must not exceed the selected model's "max. lump size" figure.
- Bulk density and moisture — catalog capacity is given for dry sand; other materials are recalculated individually.
- Required capacity, m³/h — allow a 15–25% margin for variation in material properties and duty cycle.
- Material temperature leaving the hopper — the standard design is rated up to +200°C.
- Duty cycle — continuous feed, or start/stop by level in the receiving unit ("under a full hopper").
Worked example (illustrative)
| Parameter | Value |
|---|---|
| Material | Crushed stone, 0–40 mm |
| Bulk density | ~1.5 t/m³ |
| Required capacity | 45 m³/h (20% margin over the actual 37 m³/h) |
| Tray incline | 8° |
| Suitable line | PEVF (bottom-mounted drive, heavy duty) |
This is an illustrative example of the sizing process, not a ready recommendation — the exact model depends on the full set of parameters for your hopper and material. Similar conditions are covered in our note on feeders for mining plants, where "full-hopper" duty is a typical operating mode.
Common sizing mistakes
- Using catalog capacity as-is — without recalculating for the material's real bulk density and moisture, so actual throughput ends up below expectations.
- Ignoring impact load at a full hopper — if the chute has no buffer volume, the full material mass lands on the feeder tray all at once.
- Sizing capacity with no margin — the slightest change in material properties (seasonal moisture, a batch with a different fraction) pushes the feeder to its limit.
- Not reporting material temperature — right after a furnace or dryer, actual temperature can exceed the standard +200°C rating, which calls for an individual solution on drive and seal materials.
- Choosing an open tray where regulations require a covered one — more on this criterion in our article on open vs. covered tray design.
"Full-hopper" duty and overload protection
An electromagnetic drive lets the feeder start right under a full hopper, effectively acting as a hopper gate — with no rotating parts that would jam under load. For overload protection, we recommend automatic mode with a vibration sensor on the tray via a control cabinet or unit: if the amplitude drifts from the setpoint, the drive shuts off, protecting both the feeder and the drive coil.
Send us your hopper and material parameters via the request form — we'll size and select a model or propose a custom solution.
How is the tray incline angle calculated, and how does it affect capacity?
The tray incline is set at the design stage of the unit and directly sets the model's datasheet capacity — specifications list it separately for 4° and for 8°.
A steeper incline moves material off the tray faster under its own weight plus the oscillation, but too steep an angle can let material slip through without even metering, while too shallow an angle makes the tray self-clean less effectively, especially with sticky or moist material. That's why every model's datasheet gives capacity for two standard angles rather than a single figure: 4° for higher capacity under steady feed, 8° for better tray self-cleaning at the cost of some capacity. The final angle for a given installation is set by the geometry of the hopper chute or loading point — it's either already fixed by an existing structure, or chosen together with the feeder model to match the required capacity and the material's properties.