The impeller is the rotating component of a centrifugal pump that transfers energy from the motor to the fluid. Its design significantly affects efficiency, head (pressure), flow rate, and suitability for different fluids (clean, abrasive, viscous, etc.).
Closed Impeller
HVAC systems, water supply, petroleum refining.
High efficiency (minimal recirculation losses).
Best for clean liquids (water, oils, chemicals).
Design: Enclosed with front and back shrouds (covers).
Advantages:
Applications:
Semi-Open Impeller
Wastewater, light slurry pumping.
Handles small solids and slurries.
Easier to clean than closed impellers.
Design: One shroud (usually back side), open on the front.
Advantages:
Applications:
Open Impeller
Sewage, mining, pulp & paper industries.
Lower efficiency (higher recirculation losses).
Handles large solids, fibrous materials, and sludge.
Less prone to clogging.
Design: No shrouds, blades fully exposed.
Advantages:
Disadvantages:
Applications:
Radial Flow Impeller
High-pressure systems (boiler feed, industrial processes).
High head, low-to-medium flow rates.
Design: Fluid exits perpendicular to the shaft (90°).
Characteristics:
Applications:
Mixed Flow Impeller
Irrigation, drainage, moderate-pressure systems.
Medium head & flow rate.
Design: Fluid exits at an angle (between radial and axial).
Characteristics:
Applications:
Axial Flow (Propeller) Impeller
Flood control, large-volume water transfer.
High flow rate, low head.
Design: Fluid flows parallel to the shaft.
Characteristics:
Applications:
| Parameter | Effect on Performance |
|---|---|
| Impeller Diameter (D₂) | Larger = Higher head & pressure |
| Blade Angle (β₁, β₂) | Affects efficiency & flow characteristics |
| Number of Blades | More blades = smoother flow but higher friction |
| Outlet Width (b₂) | Wider = Higher flow rate |
| Specific Speed (Nₛ) | Determines impeller type (radial/mixed/axial) |
Low Nₛ (10–60) → Radial flow (high head, low flow).
Medium Nₛ (60–160) → Mixed flow.
High Nₛ (160–300+) → Axial flow (low head, high flow).
Cast Iron – Low-cost, general-purpose water pumping.
Stainless Steel (SS 304/316) – Corrosion-resistant (chemicals, seawater).
Bronze – Marine applications (saltwater resistance).
Polymer (PP, PVDF) – Chemical processing (acid/alkali resistance).
Hardened Alloys (Chrome, Ni-Hard) – Slurry & abrasive handling.
✔ Efficiency – Closed impellers are most efficient (~85–92%).
✔ NPSH Requirement – Larger impellers need more NPSH (cavitation risk).
✔ Head-Flow Curve – Steeper curves for radial impellers; flatter for axial.
✔ Solid Handling – Open/semi-open impellers better for slurries.
| Issue | Cause | Solution |
|---|---|---|
| Cavitation | Low NPSH, high speed | Reduce speed, increase suction pressure |
| Clogging | Solids buildup in vanes | Use open impeller, larger passages |
| Wear & Erosion | Abrasive particles | Hard-coated or replaceable vanes |
| Vibration | Unbalanced impeller | Dynamic balancing, proper alignment |
Vortex Impeller – Creates a whirlpool effect, ideal for sewage/slurries.
Recessed Impeller – Used in chopper pumps for solids handling.
Trimmed Impeller – Diameter reduced to lower head/flow (energy saving).
The impeller is the heart of a centrifugal pump, and its design must match the fluid type, pressure, and flow requirements.
Closed impellers → Best for clean liquids, high efficiency.
Open/semi-open impellers → Handle solids, but lower efficiency.
Radial/mixed/axial → Determined by required head & flow.
The above content is compiled and published by Zhilong Drum Pump supplier, please specify, to buy oil drum pump, electric drum pump, high viscosity electric drum pump, fuel drum pump, food grade drum pump and so on, please contact us.