Which type of centrifugal pump impeller is suitable for pumping medium-sized solids?

• A. Closed impeller
• B. Semi-open impeller
• C. Open impeller
• D. Vortex impeller

Answer: (B)

A semi-open impeller is designed to handle medium-sized solids effectively. The semi-open design features vanes that are partially enclosed, allowing some room for solids to pass through while still maintaining good hydraulic efficiency. This characteristic minimizes the risk of clogging compared to a closed impeller, which has a fully enclosed design and is better suited for clear fluids.

In contrast, an open impeller, although effective in passing larger solids, can result in a more turbulent flow and may not be as efficient for certain applications due to the larger gaps between the vanes. A vortex impeller, on the other hand, is typically used for handling larger solids and creating a vortex effect to move solids without direct contact, which might not be ideal for all kinds of medium-sized applications. Therefore, the semi-open impeller strikes a balance between efficiency and solid handling capability, making it the preferred choice for pumping medium-sized solids in a centrifugal pump.