What is Centrifugal Pump? Definition, Basics, Working Principle, Applications
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What is Centrifugal Pump? Definition, Basics, Working Principle, Applications
The Centrifugal pump is the most widely used pump in the world. It is a rotary pump. Here, flow and pressure are generated dynamically due to rotational energy. We will learn all the basic details of the centrifugal pump in this session.
Let’s explore the details of the centrifugal pump!
The Centrifugal pump is working based on the centrifugal force and the name follows the same. Fluid enters the pumps, gets the energy from the centrifugal force of the impeller, and raised its velocity and pressure.
Due to this pressure, the liquid is transferred from one place to another.
Centrifugal Pump Definition
A Centrifugal pump means a hydraulic machine that converts mechanical energy into hydraulic energy.
A Centrifugal pump is a rotary machine that converts mechanical energy or kinetic energy into pressure energy or pressure head by means of centrifugal force, is known as a centrifugal pump. In simple understanding,
A pump is required to transfer liquid from an area or a place to another place.
The main acting force is centrifugal force
Kinetic energy changed into pressure energy or pressure head.
History of Centrifugal Pump
Johann Garden first invented the centrifugal pump in 1680. However, the practical centrifugal pump was first built in 1818.
Centrifugal Pump Parts
The main parts of the Centrifugal Pump are:
Suction & Discharge Nozzles
A foot valve
Suction nozzle or suction flange
Pump Shaft / Connections
Delivery or discharge pipe
Discharge nozzle or discharge flange
Shroud and Legs
Centrifugal Pump Impeller
The impeller is the main part of the pump and it is connected to a motor drive shaft that drives the pump. The impeller rotates based on the rotation of the motor.
Pumps can also be driven by other drivers such as,
So, we can conclude that, if the area is more then velocity is more, velocity more means kinetic energy more which changed into pressure head.
Due to this pressure head, the liquid can be lifted to a different level.
How does a centrifugal pump work?
Below the schematic diagram of the centrifugal pump explains step by step working of the pump.
Step#1 Priming & Start-up
Do you have to prime a centrifugal pump? Let’s try to understand! Centrifugal Pump doesn’t suck the liquid, and priming is to be done at the beginning. Priming means liquid must be filled-up in the suction pipe to fill all the air gaps.
If air is not removed from the pump, then a small negative pressure will be created at the suction pipe and it cannot suck the water from the water sump or reservoir.
Priming means filling the liquid in the suction pipe.
The priming is done by a “Foot Valve” installed at the end of the suction pipe.
The filling is done up to the pump casing top.
In a centrifugal pump, the discharge pressure is directly proportional to the density of fluid and priming is necessary.
Step#2 Start the motor
Once priming is done, the motor to be switched on. When the motor or drive shaft rotates, the impeller also rotates since both these are connected.
The suction pipe is connected between the water sump and the eye. When the impeller rotates at high speed, water will also start to rotate at the same speed and the impeller accelerates the fluid out through the impeller vanes.
Now, whatever the type of impeller, it may be closed or open or semi-open, the principle is the same.
Due to rotation, a negative pressure is created in front of the impeller and a vacuum is created. Water will start to fill these vacuum and water will flow continuously.
If the pressure reduces to below the vapor pressure, the bubble formed which is not recommended to avert cavitation, which damages the impeller.
Step#4 Increase in Pressure Energy
There are two important design parameter volute and diffuser, plays an important role.
When the impeller rotates, the liquid also rotates with the impeller and the centrifugal force is acted on the liquid.
The velocity and pressure are transferred to the liquid during this process.
This liquid then enters inside the pump volute casing (sometimes with diffuser)
The volute casing is looking like a curved funnel and the cross-sectional area is gradually increased.
Reduction in the area reduces the velocity of the liquid.
This velocity reduction converted into pressure and pressure is increased.
This liquid then passes towards the discharge nozzle.
Check a nice ANIMATED VIDEO!
The purpose of both types of designs is mainly to translate the fluid flow into a controlled discharge at the required pressure.
In this design, velocity is reduced and converted into pressure energy as per Bernoulli’s theory.
Hence, pressure energy or pressure heat at the outlet is increased.
In the case of the diffuser, since the liquid is expelled between stationary vanes, the velocity of the liquid is reduced and the same is converted into pressure energy. Hence, a high-pressure head is developed.
Factors that Impact Centrifugal Pump Performance
Suction Pressure – If pressure at pump suction is less than required, cavitation will occur and the impeller will be damaged
Flow at suction – Constant flow at pump suction is required, otherwise the pump cannot work at design conditions.
The viscosity of the fluid – Best for lower viscosity
Vapor Pressure of the Fluid – Very low-pressure liquid is not suitable, it will make cavitation.
The density of the fluid – High-density liquid is not suitable.
Main features of the Centrifugal Pump
The main feature of centrifugal pumps is:
Centrifugal pumps are used for higher flows and in case of low viscous liquids. It can handle liquid around 0.1cP as well.
In some chemical industries, most of the pumps are centrifugal pumps.
Typical Centrifugal Pump Package
Let’s see what are the basic components in a standard pump package. The components are,
Pump along with casing, impeller, shaft, etc.
Gland packing system
How to Select a Centrifugal Pump?
We have got a basic idea about the centrifugal pump, now, how to select this kind of pump and what are the main criteria needs to look into?
Let’s see the main factors for this type of pump selection,
We have already learned that centrifugal pump is suitable for low viscosity. Now, if you are working in a project, where you need to handle low viscous liquid, then centrifugal pump will be your option.
Check the pressure / head requirements for the applications.
In case of very high pressure, proper sealing to be used.
In case of high temperature applications, proper cooling/suitable gaskets, sealing etc. should be taken care
Density of fluid
Normally, we have considered water as working fluid, however, it can be any other fluid as well. Hence, density as well as specific density or specific gravity to be considered.
Centrifugal Pump Application
These pumps are widely used for pumping water, other low & medium viscous liquids.
Solvents, acids, bases, oils, organics, etc. are easily handled.
Water supply in buildings, domestic water supply, many industries.
Pumping sewage and slurries.
Fire protection system
The beverage industry, like transferring juice, bottled water, etc.
Dairy industries, like transferring milk, etc.
Refrigeration and air conditioning industries
Oil & gas industries – pumping crude oil, slurry, etc.
Centrifugal Pump Advantages
Simple & compact design
Less capital cost & operating cost
Less space requirements
Less moving parts & easy for maintenance
Less capital cost
Steady & consistent flow
Handles a large volume of liquids
These pumps do not include drive seals that reduce leakage risk.
These pumps are used to pump out normal liquid to harmful and risky fluids as well.
These pumps handle non-viscous, and low viscous to medium viscous liquids.
These pumps generate low friction, hence, friction loss is less.
Normally, the motor and pump are separated, heat transfer is negligible.
Cost is comparatively less
Installation is easy
Noise is very less
Very less wear & tear with respect to other kinds of pumps.
The pressure is uniform.
No shock waves or pulsation.
Centrifugal Pump Disadvantages
What are the limitations of a centrifugal pump?
It uses impeller rotation for suction, hence, very less suction power.
Due to the low suction power, priming is necessary.
The coupling can generate some magnetic resistance, which can make energy losses.
Once the intense load occurs, possibilities are there for the coupling fall.
Efficiency reduces when this pump handles high viscous liquids.
Very less flow can overheat the pump.
Not suitable for high head applications.
It can produce cavitation, corrosion, etc.
Centrifugal Pump Safety
There are a few key points for centrifugal pump safety:
At first selection of pump. It should be based on the application.
Always check the overheating of the pumps.
Follow the instruction manual, as well as the operator, should have proper training.
Internal parts shall be maintained, and worn-out components shall be replaced immediately.
The blockage of the suction and discharge line shall be checked.
Air leaks shall be checked.
Check for Air Leaks.
Never skip routine maintenance and scheduled inspection.
A shut-off test shall be done.
Proper location and proper maintenance space should be considered.
Standards for Centrifugal Pumps
A few of the major codes and standards that are used in process industries are listed below:
ANSI B 73.1 – Horizontal End Suction Centrifugal Pumps
ANSI B 73.2 – Vertical In-Line Centrifugal Pumps
ANSI B 73.2 – Sealless Horizontal End Suction Centrifugal Pumps