Impellers in Slurry Pump Applications – Types, Wear Control, and Practical Examples
Slurry pumps are widely used in industries such as mining, chemical processing, wastewater treatment, and power generation. The impeller is the heart of a slurry pump, responsible for imparting energy to the slurry mixture and ensuring efficient flow. Selecting the right impeller design and maintaining clearances are critical for performance, service life, and reliability.
Types of Impellers Used in Slurry Pumps
Both semi-open impellers and closed impellers are commonly used in slurry services:
- Semi-Open Impellers
- Easier to maintain and adjust.
- Suitable for handling slurries with larger solid particles.
- Example: Semi-open impellers are often used in dredging pumps where sand and gravel are present.
- Closed Impellers
- Provide better efficiency and leakage control.
- Suitable for fine slurries with lower solid concentrations.
- Example: Closed impellers are used in chemical slurry pumps where fine particles are suspended in liquid.
Leakage Control in Slurry Pumps
Leakage back into suction is controlled by:
- Clearing or Expelling Vanes – Located on the impeller to reduce recirculation.
- Close Axial Clearances – Maintain efficiency by minimizing leakage.
- Practical Note: As axial clearances increase with wear, pumps should be designed for easy clearance adjustments to maintain performance.
Radial vs Axial Clearances
- Close Radial Clearances
- Wear quickly when solids are present.
- Not suitable for high-concentration slurries.
- Best for low concentrations of fine slurries.
- Axial Clearance Arrangement
- Common in high-wear services.
- Provides better leakage control between impeller inlet diameter and liner.
- Example: Mining slurry pumps often use axial clearance designs to handle abrasive ores.
Impeller Attachment Methods
Impeller attachment varies by manufacturer and service requirements:
- Bolted Designs – Easy to assemble and disassemble.
- Threaded Designs – Provide secure attachment for high-wear services.
- Internally Threaded Impellers – Protect attachment from wear in highly abrasive slurries.
- Practical Example: In coal washing plants, internally threaded impellers are used to extend service life against abrasive coal particles.
Balancing Requirements for Slurry Pump Impellers
Balancing slurry pump impellers is more complex than balancing impellers for clear liquids:
- Clear-Liquid Impellers
- Remain substantially balanced throughout their operating life.
- Slurry Pump Impellers
- Wear causes erosion of metal, leading to imbalance.
- Bearings and shafts must be designed to withstand higher residual unbalance.
- Manufacturers set balancing standards based on operational and design factors.
- Practical Example: In mineral processing plants, slurry pump impellers gradually lose balance due to erosion, so the pump design must accommodate this unbalance without premature bearing failure.
Conclusion
Impellers are critical components in slurry pumps, and their design directly affects efficiency, wear resistance, and service life. Semi-open and closed impellers serve different slurry conditions, while axial clearance arrangements and internally threaded attachments help control leakage and protect against wear.
