What centrifugal pump impeller types are there?

There are three main types of centrifugal pump impellers: open impellers, semi-open impellers, and closed impellers. In addition, there are several variations on impeller types.

Open Impellers

Open impellers feature vanes that radiate outward from the centre with no other connection. They are what you will find on smaller centrifugal pumps, such as the C-series, thanks to their simple design, comparatively low-cost, ability to handle small suspended solids, and ease of cleaning via CIP. However, they are structurally weaker, and less efficient than other designs.

Semi-Open Impeller

Tiia Monto, CC BY-SA 3.0, via Wikimedia Commons

On a semi-open impeller, the vanes connect on one side to a shroud. This increases both strength and efficiency, and still allows some small suspended solids. However, they are more expensive and harder to clean, relying on drilled holes in the shroud to allow CIP fluid to the backside and the seal.

Semi-open impellers have a single closed side, improving the strength of the vanes and improving efficiencies.

Closed Impeller

In a closed impeller the vanes sit between two discs. These are often used in large pumps, and provide much higher efficiency. These are more complicated to design and expensive to build. They are also very difficult to CIP, so they are not commonly used in the food and beverage industry.   

Other Types:

Helicoidal

Helicoidal impellers, as seen in Inoxpa’s RVN pumps, are semi-open impellers with a helicoidal design. This design lets them move significant suspended solids and highly viscous products. 

Shear

Shear pumps often use a centrifugal impeller, though one specially designed to break apart solids. It can be open, semi-open, or closed depending on the manufacturer.