The specific speed of a centrifugal pump is defined as the speed of an imaginary pump, identical with the given pump, which will discharge 1 liter of water, while it is being raised through a head of one meter. Mathematically, specific speed,
The ranges of specific speeds for different types of pumps are given in the following table.
Type of pump | Slow speed with radial flow at outlet | Medium speed with radial flow at outlet | High speed with radial flow at outlet | High speed with mixed flow at outlet | High speed with axial flow at outlet |
Specific speed inr.p.m. | 10 - 30 | 30 - 50 | 50 - 80 | 80 - 160 | 160 - 150 |