"Enclosed", "open", and "semi-closed" are terms used to describe what pump part?

The terms "enclosed," "open," and "semi-closed" are used to describe the design variations of impellers in centrifugal pumps. An enclosed impeller has shrouds or covers on both sides, which can help increase efficiency by directing fluid flow and reducing turbulence. Open impellers lack these shrouds, making them suitable for handling fluids with solids or fibrous materials because they provide less resistance to flow. Semi-closed impellers feature one shroud, providing a compromise between the characteristics of enclosed and open designs, balancing efficiency and the ability to handle solids. Understanding these designs is crucial for selecting the appropriate type of impeller based on the application and the nature of the fluids being pumped.