What are centrifugal pumps?

Centrifugal pumps are a sub-class of dynamic axisymmetric work-absorbing turbomachineryCentrifugal pumps are used to transport fluids by the conversion of rotational kinetic energy to the hydrodynamic energy of the fluid flow. The rotational energy typically comes from an engine or electric motor. The fluid enters the pump impeller along or near to the rotating axis and is accelerated by the impeller, flowing radially outward into a diffuser or volute chamber (casing), from where it exits.

Common uses include water, sewage, petroleum and petrochemical pumping; a centrifugal fan is commonly used to implement a vacuum cleaner. The reverse function of the centrifugal pump is a water turbine converting potential energy of water pressure into mechanical rotational energy.

How it works

General explanation: Like most pumps, a centrifugal pump converts rotational energy, often from a motor, to energy in a moving fluid. A portion of the energy goes into kinetic energy of the fluid. Fluid enters axially through eye of the casing, is caught up in the impeller blades, and is whirled tangentially and radially outward until it leaves through all circumferential parts of the impeller into the diffuser part of the casing. The fluid gains both velocity and pressure while passing through the impeller. The doughnut-shaped diffuser, or scroll, section of the casing decelerates the flow and further increases the pressure.

A Centrifugal Pump is widely used in the industry because it has a simple design, very high efficiency, wide range of pump capacity and head. These pumps are easy to operate and maintain and have a smooth flow rate.

The design of a Centrifugal Pump depends on the following:

  • Number of suctions (could be single suction or double suction)
  • Number of impellers (single stage, two stage or multistage)
  • Output
  • Impellers type, number of vanes/volutes, etc.

There are three types of centrifugal pumps:

  • Single Stage Pump – Such pumps are used when low head is required and they generally have one impeller only. Their cost is low.
  • Two Stage Pump – Such pumps have two impellers arranged in series and are used where medium head is required.
  • Multistage Pump – Such pumps have three or more than three impellers arranged in series. They are used when high head service is required.

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