2025-12-04
When purchasing a horizontal sand mill, attention should be paid to the following critical aspects:
Many manufacturers use 304 stainless steel for the grinding chamber. However, the nickel content in standard 304 stainless steel (typically 8%) is crucial for corrosion resistance. Some suppliers may use lower-grade variants with only about 4% nickel. This can lead to rusting, especially when processing water-based materials or if the mill sits idle with liquid residue. Rust contamination can cause discoloration in products (e.g., graying of white pigments, darkening of phthalocyanine blue, fading of reds). This discoloration occurs because the chamber wall wears against the grinding media (beads).
To minimize this wear when using stainless steel chambers, suppliers often recommend softer media like glass beads or standard zirconium silicate beads. However, for achieving fine particle sizes (e.g., 0.2-0.5μm / 200-500 nm), high-density media like pure zirconia beads are necessary for effective grinding energy. The conflict arises because these hard beads accelerate the wear of a soft stainless steel chamber.
Solution: Opt for mills with grinding chambers made from imported wear-resistant alloy steel (e.g., ASSAB tool steel). This allows the use of high-density, high-purity (95%+ ZrO₂) zirconia beads (density ~6.0 g/cm³) without significant chamber wear. Higher bead density provides greater impact force, leading to more efficient particle size reduction compared to lighter glass beads (~2.0 g/cm³) or standard zirconia beads (~2.5 g/cm³).
Horizontal sand mills primarily feature two agitator designs:
Disc-Type: Features smooth chamber walls and a rotor with multiple discs. Grinding media moves primarily in a linear, back-and-forth motion. This design offers limited grinding efficiency and longer processing times for fine grinding.
Pin-Type: Features both a rotor and a stationary chamber liner studded with pins (typically made of tungsten carbide). This creates a more intense grinding zone. The media follows a complex path involving both linear and zigzag motions at high tip speeds (e.g., ~12 m/s). This significantly enhances shear and impact forces, leading to much faster and more efficient grinding compared to disc-type mills.
This critical component separates the finished product from the grinding beads. It typically consists of a gap separator with a stationary ring (near the mechanical seal) and a rotating ring (in contact with the product slurry). Both are ideally made of tungsten carbide for wear resistance.
Gap Adjustment: The separation gap is adjustable based on the target fineness and bead size. For example, to achieve a 200-500 nm grind, a gap of 0.1-0.4mm might be set. Bead diameter should generally be at least 3 times the gap width to prevent blockage. Therefore, for a 0.17mm gap, 0.6-0.8mm beads would be appropriate. A correctly sized separator ensures product purity, high throughput, and efficient grinding.
Mechanical Seal: High-quality, leak-proof mechanical seals from reputable German brands are essential. These seals should have a long service life (e.g., 8000+ hours) and be self-lubricating, eliminating the need for external oil lubrication which could contaminate the product. The seal flush should use a solvent or water compatible with the product.
Cooling: Effective temperature control is vital. A comprehensive four-point cooling system covering the mechanical seal, grinding chamber, front end plate, and shaft is recommended to maintain optimal process conditions and product quality.
A well-designed pin-type mill with a dual-stage pin configuration, paired with high-density zirconia beads, offers significantly higher efficiency. Some models feature a dual-outlet gap system to further enhance output, potentially doubling or more the productivity of conventional mills without compromising product quality.
The main control panel should be centrally located and user-friendly, simplifying operation and parameter adjustments.
The grinding chamber should have a dead-space-free, self-cleaning design.
Features like chamber-mounted wheels or carts allow easy dismantling and maintenance. Ideally, one person should be able to perform tasks like cleaning or replacing beads.
The electrical system should use reliable components (e.g., Schneider/Taiwan Shihlin brands). Comprehensive safety interlocks are mandatory, including automatic shutdown in case of over-pressure in the chamber, over-temperature, or motor overload to protect both the equipment and the operator.
