Centrifugal Pump: Casing and Impeller

A pump casing encloses the fluid-handling interior and contains pressure. An impeller is a rotating component with vanes or blades that transfers mechanical energy to the liquid. In a centrifugal pump they have distinct, connected roles: the impeller adds energy, while the casing contains and directs the flow. KSB casing definition · KSB impeller definition · Grundfos energy transfer

Casing and impeller roles

The casing surrounds the rotating hydraulic components. The impeller rotates with the pump shaft and interacts with the liquid through its vanes. The casing is not simply a protective cover over an otherwise independent pump; its internal flow passages are part of the hydraulic arrangement. KSB component relationship · Grundfos impeller and casing

The nozzles identify where liquid enters and leaves the pump. Their names describe their functions; KSB notes that the connections may join piping or be immersed, depending on the pump construction. KSB inlet and outlet nozzles

What a volute does

A volute casing collects liquid leaving the impeller and guides it towards the discharge nozzle. Its flow passage supports conversion of kinetic energy into static pressure. This role differs from supplying the mechanical energy at the rotating impeller. KSB volute function · Grundfos water-pump explanation

Volute is a particular casing form, rather than a universal name for every pump casing. KSB also describes annular and tubular forms. KSB casing categories

Impeller does not mean only one flow direction

KSB classifies impellers by their flow pattern, including radial, mixed-flow and axial types. Grundfos illustrates radial outward acceleration in its water-pump explanation; that example should not be turned into a definition requiring every impeller to discharge only radially. The component name identifies a rotating energy-transfer element, while its geometry determines the more specific category. KSB impeller categories · Grundfos radial example

Construction and performance are different descriptions

If a drive shaft passes through the casing, the construction needs a shaft-sealing arrangement to control leakage and air ingress. This condition does not imply that every pump uses the same external shaft seal. KSB shaft-seal condition

Component names alone provide no guaranteed flow, head or pressure rating. See pump flow rate and head for those quantities and the pumps and fluid equipment section for connected reading. This page explains roles; it does not specify a pump design or a service procedure.