What Is The Impeller Of A Centrifugal Pump Type Water Pump

Aug 16, 2025

The impeller is a key component of a centrifugal pump, typically made of cast iron. The blades on the impeller play a crucial role, and the impeller's shape and dimensions are closely related to the pump's performance. Impellers can generally be classified into two types: single-suction and double-suction.

Single-suction impellers draw liquid from one side and are commonly used in low-flow pumps.

Double-suction impellers draw liquid from both sides and are used in high-flow pumps.

Four Main Types of Centrifugal Pump Impellers

(a) Closed (b) Front semi-open (c) Rear semi-open (d) Open

Closed Impeller

Consists of blades enclosed between front and rear shrouds.

Offers high efficiency but is more complex to manufacture.

Most widely used in centrifugal pumps.

Suitable for clean, low-viscosity liquids (e.g., water, chemical solutions) without solid particles.

Semi-Open Impeller

Front semi-open: Composed of blades and a rear shroud.

Lower efficiency but can be improved with an adjustable wear ring.

Rear semi-open: Composed of blades and a front shroud.

Similar efficiency to closed impellers due to compatible wear rings.

The blades also function as back vanes or auxiliary impellers, enhancing sealing.

Easier to manufacture, cost-effective, and adaptable.

Suitable for liquids containing suspended solids or fibers.

Increasingly used in petrochemical pumps for water and similar fluids.

Open Impeller

Consists only of blades with reinforcing ribs (no front or rear shrouds).

Typically has fewer blades (2–5).

Lower efficiency, less common, mainly used for high-viscosity or slurry-like liquids.

Blade Design

Centrifugal pump impellers usually feature backward-curved blades, which can be either:

Cylindrical (straight) – Simpler but less efficient.

Twisted (3D curved) – Reduces blade load, improves suction performance, and enhances cavitation resistance. However, twisted blades are more complex to manufacture and costly.

Manufacturing Requirements for Petrochemical Pumps

Impellers must be cast or fully welded for structural integrity.

Welded impellers have gained popularity, especially for corrosion-resistant alloys (e.g., titanium) that are difficult to cast.

Welded impellers offer better geometric accuracy and surface finish, improving pump efficiency.