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.