What is a Pump ?

A Pump is a mechanical device used to move fluids such as liquids , gases or slurries.

It increases the additional energy of the Fluid.

The additional energy can be used to increase  –

• Velocity (flow rate )
• Pressure
• Elevation

Classification Of Pump 

Pumps are broadly categoraized as :

• Positive Displacement Pumps :  A positive displacement pump makes a fluid move by trapping a fixed amount and forcing (displacing) that trapped volume into the discharge pipe.

Positive displacement pumps, which lift a given volume for each cycle of operation, can be divided into two main classes, reciprocating and rotary. Reciprocating pumps include piston, plunger, and diaphragm types; rotary pumps include gear, lobe, screw, vane, and cam pumps.

• Dynamic Pumps : Rotodynamic pumps (or dynamic pumps) are a type of velocity pump in which kinetic energy is added to the fluid by increasing the flow velocity. This increase in energy is converted to a gain in potential energy (pressure) when the velocity is reduced prior to or as the flow exits the pump into the discharge pipe.

Centrifugal pumps are the most common type of pump used in industry. There are three basic sub-types of centrifugal pumps:

• Axial Flow  Pumps are high flow, low pressure pumps which lift fluid in a direction parallel to the impeller shaft.
• Mixed Flow Pumps are medium flow, medium pressure pumps which push fluid out away from the pump shaft at an angle greater than 90°.
• Radial Flow Pumps are high pressure, low flow pumps which accelerate fluid along the impeller blades perpendicular to the shaft.

Working of Centrifugal Pumps

Impeller – The Heart of Centrifugal Pumps

Centrifugal pumps are used to induce flow or raise pressure of a liquid. Its working is simple. At the heart of the system lies impeller. It has a series of curved vanes fitted inside the shroud plates. The impeller is always immersed in the water. When the impeller is made to rotate, it makes the fluid surrounding it also rotate. This imparts centrifugal force to the water particles, and water moves radially out.

Diffuser : 

A diffuser is actually a series of vanes surrounding the impeller which accepts the discharge of liquid from the impeller. It efficiently reduces the velocity and, in the case of a multistage pump, directs this lower velocity fluid into vaned return channels which guide the liquid to the inlet or eye of the next stage impeller.