Industry-Knowledge

Different types of impellers used in centrifugal pumps

Centrifugal pumps use various types of impellers to move fluids by converting rotational energy into kinetic energy and then into pressure. The choice of impeller depends on factors like fluid viscosity, solid content, head requirements, and efficiency. Here are the main types of impellers used in centrifugal pumps:

1. Based on Flow Direction:

  • Radial Flow Impeller

    • Fluid exits perpendicular to the shaft (90°).

    • High head, low flow applications.

    • Used in high-pressure pumps (e.g., multi-stage pumps).

  • Mixed Flow Impeller

    • Combines radial and axial flow characteristics.

    • Fluid exits at an angle (between 0° and 90°).

    • Medium head and flow applications.

  • Axial Flow (Propeller) Impeller

    • Fluid flows parallel to the shaft (0°).

    • Low head, high flow applications (e.g., flood control, irrigation).

2. Based on Suction Type:

  • Single Suction Impeller

    • Fluid enters from one side.

    • Simpler design but may have axial thrust imbalance.

  • Double Suction Impeller

    • Fluid enters from both sides.

    • Balanced axial thrust, higher flow capacity, and efficiency.

3. Based on Design & Construction:

  • Closed (Shrouded) Impeller

    • Has front and back shrouds (covers).

    • High efficiency, best for clean liquids (no solids).

    • Used in water, chemical, and oil pumps.

  • Semi-Open Impeller

    • Has only a back shroud, open on one side.

    • Handles small solids and slightly viscous fluids.

    • Self-cleaning, used in wastewater and slurry pumps.

  • Open Impeller

    • No shrouds, just vanes attached to a hub.

    • Handles fibrous & abrasive fluids (slurries, sewage).

    • Less efficient but easier to clean and maintain.

4. Specialized Impeller Types:

  • Vortex Impeller

    • Creates a whirlpool effect to pass solids without clogging.

    • Used in sewage and slurry pumps.

  • Non-Clogging (Recessed) Impeller

    • Large flow passages to prevent clogging.

    • Handles thick slurries, wastewater, and debris.

  • Splitter Impeller

    • Alternating full and partial vanes for better efficiency.

    • Reduces turbulence in medium-viscosity fluids.

5. Based on Vane Shape:

  • Backward-Curved Vanes

    • Most common, energy-efficient, stable performance.

  • Forward-Curved Vanes

    • Higher flow but lower pressure, prone to clogging.

  • Straight Radial Vanes

    • Simple design, used in slurry and abrasive applications.

Selection Factors:

  • Clean liquids → Closed impeller (high efficiency).

  • Solids/Slurries → Open or semi-open impeller.

  • High head → Radial flow impeller.

  • High flow → Axial or mixed flow impeller.

Each impeller type has trade-offs in efficiency, clog resistance, and maintenance needs. The right choice depends on the specific application.

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