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Magnetic Mixers Applications

Ceramic Sliding Bearings for Magnetic Mixers

CERAMIC SLIDING BEARINGS

Key components of magnetic mixers are ceramic sliding bearings which are in direct contact with the mixed product and additionally are exposed to temperature changes and cleaning chemicals.

Usually the male bearing is made of zirconium oxide and the female bearing is made of silicon carbide. The static, robust male bearing is attached to the vessel's tank plate and the rotating female bearing is integrated and sealed with the mixing head. The inner bearing made of zirconium oxide has increased resistance to impacts and damage from sudden rotor settling or during assembly / disassembly of the mixer. The outer bearing made of silicon carbide provides superior abrasion resistance and low surface roughness.

Thanks to our extensive mechanical machining facility we can achieve high quality surfaces with minimal friction in the operating mode and with reduced breakage risk in dry run conditions.

Graphic_Magnetic Mixers_1000px.jpg

Combination of zirconium oxide FZM and silicon carbide StarCeram© S

  • Zirconium oxide (FZM) is used because of high impact resistance (high flexibility/low E-Modulus)
  • Silicon carbide (SSiC) is used because of hardness and wear resistance

Why ceramics?

Ceramic bearings are one of the most critical parts in the mixer:

  • Direct contact with the high value product (product lubricated)
  • Exposure to cleaning chemicals and temperature cycling

Main advantages

  • Eliminates risk of contamination from mechanical wear debris
  • Biocompatibility: complying with FDA rules and USP Class VI certification required for pharmaceutical and biotechnology industries
  • Good thermo shock resistance CIP /SIP possible (clean in place / sterilization in place)
  • Perfect finish and surface quality Ra < 0,5 μm
  • No product residue or bacterial growth
  • Low shear forces (particle generation below detectable levels)
  • Minimalized drag force
  • Emergency dry run possible
  • Tight tolerances for perfect coupling between bearings (up to 5 μm)
  • Simple design eliminates entrapments of product (no product stagnation between bearing surfaces)
  • Easy maintenance - ceramic bearing parts can be replaced by users on site

Our strengths

  • Long term proven quality in application
  • One source for both ceramic materials
  • High precision grinding technologies
  • Metal-ceramic joints or threads in ceramics possible

Material properties

PropertiesUnitFZMStarCeram© SMetal
Main components-ZrO2, MgOSiCStainless steel
Properties of microstructure
Densityg/cm³≥ 5.703.167.8
Open porosityVol. %000
Water absorption%00-
Average crystal sizeμm50--
Mechanical properties
Hardness (HV1)GPa10.7237.2 (HV10)
Compressive strengthMPa2000> 25001700
Bending strength σmMPa500
(DIN EN 843-1)
450500
Modulus of elasticity (E-modulus)GPa185
(static)
440210
Poisson ratio-0.30.170.3
Fracture toughness KIcMPa*m0.56.3
(SEVNB)
2-3-
Thermal properties
Max. operating temperature°C9001400120-280
Specific heat 20 °CJ/(kg*K)400670502
Thermal conductivityW/(m*K)320045
Thermal expansion coefficient 20-300 °C10-6/K10.64.412
Electrical properties
Specific electrical resistance 20 °CΩ•cm101010810-6
Typical colour-yellowblack-
Characteristic values may vary depending on shape of products and service conditions.

Examples

SSiC_female and male bearings_290x280.jpg

Female bearing made of silicon carbide StarCeram© SSiC, male bearing made of zirconium oxide FZM

Shrink fit ceramic in metal housings_290x180.jpg

Shrink fit ceramic in metal housing

Male bearing assembly on tank plate_290x180.jpg

Male bearing assembly on tank plate

Stirrers made of Alumina_290x180px.jpg

Stirrers made of alumina

Near net shape forming method (F-Molding)

For stirrers elements Kyocera can produce complex shape elements using new near net shape forming method (F-Molding). In this method elements are casted directly to a parts shape without need of green machining before sintering. This way machining costs are reduced in comparison to other ceramic production methods.

Advantages

  • Complex shape: products with complex shapes that cannot be machined
  • Cost saving by reducing waste of raw materials (vs. CIP = cold isostatic pressing)
  • Cost saving through less processing (vs. CIP)
  • Saving initial cost: an economical forming die (vs. injection / press forming)

Examples

F-Molding method creates more freedom in design for manufacturing.
Materials: Zirconia, Silicon Nitride, Silicon Carbide, Cordierite

Zirconia_Z206N_01_290x180px.jpg

Zirconia (Z206N)

Zirconia_Z206N_02_290x180px.jpg

Zirconia (Z206N)

Silicon Nitride_SN240_01_290x180px.jpg

Silicon Nitride (SN240)

Silicon Nitride_SN240_02_290x180px.jpg

Silicon Nitride (SN240)