Powder checking - Removing Foreign Bodies
| Section Summary |
|---|
| Introduction to different foreign body checking equipment including Vibrating Sieves, Magnets, and Metal Detectors. |
Why checking the powder?
Checking powder ensures that no foreign body is carried within the bulk solids, either at the beginning of the process (raw materials) or prior to final packaging. Foreign bodies can damage equipment, increase ATEX explosion risks, and lead to costly customer recalls.
Industrial Rules of Thumb
- Sieve Oversize: Typically, "security" sieving targets 2-5% of the aperture size for foreign body capture.
- Magnetic Strength: Use NdFeB (Neodymium) magnets with >10,000 Gauss for fine ferrous particle capture.
- Metal Detection: Gravity fall detectors should have an "auto-learn" function to account for "product effect" (conductivity of the powder itself).
| Sieves & Sifters | Magnets | Metal Detectors |
|---|---|---|
| Vibrating Design | Static & Rotary | Detection Principles |
| Sizing & Capacity | Extractors | Rejection Systems |
| Troubleshooting | Positioning Strategy | Selection Guide |
Vibrating Sieve Capacity Estimator
Mathematical Principle of Sifting
The capacity of a vibrating sieve can be approximated by:
\[ Q = A \cdot \left(\frac{\rho}{\rho_{\text{ref}}}\right) \cdot d \cdot C_{\text{base}} \cdot F_{\text{material}} \]Where \(Q\) is throughput, \(A\) is screen area, \(\rho\) is bulk density, and \(d\) is screen aperture opening.