Parts of a Centrifugal Pump – Impeller, Volute, Casing

All 16 parts on the diagram

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Path of the liquid 7

Impeller The wheel that spins and throws the liquid outward.
Vanes (impeller vanes) Curved blades that push the liquid round and outward.
Eye (impeller eye) The center of the impeller, where the liquid enters.
Volute A widening channel: the liquid slows here and gains pressure.
Discharge (outlet) The liquid leaves the pump here.
Pump casing The fixed shell that holds the liquid and guides it.
Suction (inlet) The liquid comes in here, toward the eye.

Shaft, seals and bearings 9

Wearing rings Replaceable rings where impeller and casing nearly touch.
Hub (impeller hub) The middle of the impeller, fixed on the shaft.
Packing Soft rings that limit leakage along the shaft.
Lantern ring A hollow ring with holes that spreads cooling liquid round the shaft.
Stuffing box The space round the shaft that holds the packing.
Gland (packing gland) It holds the packing in; its nuts press it tighter.
Bearing housing The frame that holds the bearings and their lubricant.
Bearings They carry the turning shaft and cut friction.
Shaft The rotating rod that drives the impeller.

How this list was compiled: Every name checked on 2026-09-30, a name kept only where two independent sources use it. US Department of Energy, DOE Fundamentals Handbook, Mechanical Science (DOE-HDBK-1018/1-93), Pumps module, as hosted in full text by Engineering Library (https://engineeringlibrary.org/reference/pumps-doe-handbook); US Navy, Utilitiesman 3 and 2, Rate Training Manual (1973), chapter 6, Prime Movers, Pumps, and Air Compressors (https://archive.org/details/ERIC_ED097442); US Army, FM 3-34.471, Plumbing, Pipe Fitting, and Sewerage (2001), chapter 11, Centrifugal Pumps (https://archive.org/details/FM_3_34_471_P_2001); Wikipedia, Centrifugal pump (https://en.wikipedia.org/wiki/Centrifugal_pump). Licence: own work

The drawing: Drawn for this site on 2026-09-30 from plain geometry; a schematic of no maker's product, nothing traced. Licence: own work

How it works

A centrifugal pump moves liquid with a spinning impeller inside a casing. The first drawing shows the pump from the front with its cover off. The second cuts it through along the shaft to show the seals and the bearings.

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The path of the liquid

Liquid comes in at the suction and reaches the eye of the impeller. The vanes whirl it round and throw it outward into the volute. There it slows, its pressure rises, and it leaves at the discharge.

Round the shaft

The shaft leaves the casing through the stuffing box, where packing held in by the gland limits leakage. A lantern ring spreads cooling liquid among the packing. Wearing rings sit where the impeller and the casing nearly touch. Two bearings in the bearing housing carry the shaft.

Questions and answers

What are the main parts of a centrifugal pump?

An impeller with curved vanes on a shaft, inside a casing. The casing has a suction, a volute and a discharge. Round the shaft are wearing rings, a stuffing box with packing or a mechanical seal, and bearings.

What does the impeller do?

It spins. Liquid enters at its eye, the vanes whirl it round, and it is thrown outward from the rim into the volute at high speed.

What is the volute in a centrifugal pump?

The channel in the casing round the impeller. It widens toward the discharge, so the liquid slows down, and as it slows its pressure rises.

What is the difference between packing and a mechanical seal?

Both seal the place where the shaft leaves the casing. Packing is rings of material pressed round the shaft in a stuffing box. A mechanical seal has two polished faces, one turning with the shaft and one fixed to the casing.