Sedimentation in a horizontal bead mill happens when beads and heavy particles settle to the bottom of the chamber, mainly when the mill stops with slurry inside, but also in low-flow zones during operation. The settled layer makes restarts hard, overloads the drive and seal, and can break beads. It is prevented by flushing before stops, keeping the slurry stable, and restarting gradually.
Why it happens
- Stopping with product inside: with no rotor motion, beads and dense particles sink and pack together.
- Unstable slurry: low viscosity, dense particles or too little dispersant let solids settle quickly.
- Low flow and dead zones: in a horizontal chamber, solids can collect where flow is weakest.
- Long stops: the longer the stop, the harder the layer becomes, especially if the slurry thickens or dries.
What it causes
| Problem | Why |
|---|---|
| High starting torque, motor trips | The rotor must break a packed bead layer |
| Seal and shaft stress | Uneven load at start-up |
| Broken beads, later screen clogging | Beads crushed in the packed layer |
| Off-spec product at restart | Settled solids leave in a slug |
Solutions
- Flush with solvent or carrier before every planned stop, until the outlet runs clear.
- Keep the slurry stable: set solids and dispersant in the lab so particles stay suspended.
- For short stops, keep the agitator in the feed tank running so the feed stays mixed.
- Restart in steps: start the feed pump and flushing first, then the rotor at low speed, then raise speed and flow.
- Never let slurry dry inside the mill.
Safe start-up and shut-down sequences are covered in INFOR's bead mill start-up and shut-down guide, and other faults in the troubleshooting guide.
Design choices that reduce sedimentation
In a vertical mill the material flows bottom-up through the chamber, which avoids the horizontal dead zones where solids collect. INFOR's vertical dual-power and LPM vertical mills use this layout. For a full comparison, see vertical vs horizontal bead mills. INFOR runs free material tests at its Dongguan and Hubei test bases; send your material, target fineness and output through the contact page.