Centrifugal Pumps - Working, Applications ,Types,Advantages and Disadvantages

Centrifugal Pumps:  A mechanical device used to transport fluids by the conversion of rotational kinetic energy to the hydrodynamic energy of the fluid flow.

● Centrifugal pumps are the most popular pump used and are the chief pump type in the class of kinetic pumps.

● Used in various sectors such as:  agriculture, power  generation plants, municipal, industries, domestic purposes, etc.

● Common uses include:  air, water, sewage, petroleum, petrochemical pumping.

● Consist of two major parts:
1. impeller (a wheel with vanes)
2. Circular pump.


How it works:

● Converts mechanical energy from a motor to energy of a moving fluid.
● Centrifugal pumps include a shaft driven impeller that rotates inside a casing.
● Energy conversion is due to the outward force that curved impeller blades impart on the fluid.
● When the impeller rotates, the fluid surrounding it also rotates. This imparts centrifugal force to the water particles, and water moves out.
● Pressure and kinetic energy of the fluid rises due to rotational mechanical energy transferred to the fluid.
● A negative pressure is induced at the eye because water is displaced at the suction side.

Types of Centrifugal Pumps 

● Mechanically actuated
○ A motor uses a gear set or other mechanical mechanism to convert rotation into a reciprocating motion that moves the pump diaphragm

● Hydraulically Actuated
○ An intermediate fluid is pressurized, and this pressure flexes the diaphragm

● Solenoid
○ An electric motor energizes and de-energizes a solenoid that flexes a diaphragm

● Air Operated Double Diaphragm Pumps (AODD) ○ Air is delivered to two sides of a diaphragm, and the alternating cycles flex the diaphragm.

Advantages

● Simple principle (don’t require valves or moving parts).
● Small in size compared to other pumps with same output.
● Can move at high speeds with minimal maintenance.
● Steady and consistent output
● Can handle large volumes of fluid
● Good for medium to low head
● Good for medium to low viscous fluids.

Disadvantages

● Use rotation instead of suction to move water (very little suction power)
● Close fitting parts can cause maintenance issues as parts wear out
● Pump must be primed before use
● Can develop cavitation
● Not good for high head
● Not good with high viscous fluids.

Determining which type of pump to use

Centrifugal Pumps can be grouped into numerous types using criteria based on: 
● Number of impellers in the pump.
● Compliance with industry standards
● Impeller suction
● Type of volute
● Nozzle location
● Shaft orientation
● Orientation of case-split
● Bearing support
● Shaft connection to driver.

Applications of Centrifugal Pumps 

● Energy & Oil Industries
○ Refineries and Power Plants

● Building Services
○ Pressure boosting, heating installations, fire protection sprinkler systems, drainage, air conditioning

● Industry and Water engineering
○ Boiler feed applications, water supply (municipal, industrial), wastewater management, irrigation, sprinkling, drainage and flood protection

● The Chemical and Process Industries
○ Paints, chemicals, hydrocarbons, pharmaceuticals, cellulose, petro-chemicals, sugar refining, food and beverage production.

Diffuser Blades

In large centrifugal pumps attachments called diffuser blades. these help the pump convert dynamic into static energy. these exist to give a pump more capacity to to create head but at the expense of losing discharge.

Centrifugal Pump Efficiency

● The overall efficiency of a pump is a product of three factors
○ Mechanical Efficiency (Losses in the bearing frame and mechanical seals)
○ Volumetric Efficiency (Losses due to leakage in wear rings and impellers)
○ Hydraulic Efficiency (Losses due to fluid friction within the pump casing)

● Centrifugal pumps can have very high efficiencies
○ Medium to Large pumps can be 75% - 90% efficient
○ Small pumps can be 50% to 70% efficient