What Is Centrifugal Pump? | How does a Centrifugal Pump work?

A pump is a device that uses to transfer different incompressible fluids. These are used all over the world for different industries. There are more many types of pumps and centrifugal is one f them. This article mainly explains the centrifugal pump.

 A dynamic pump is a famous type of pump that uses a diffuser or volute casing to pressurize the fluids. The dynamic pump divides into two famous types.

1. Radial Centrifugal Pump
2. Axial Pump

In this article, we will just discuss only the radial centrifugal pump. In the previous article, we discussed the axial pump.

What is a Centrifugal Pump?

A Centrifugal pump is a mechanical machine that pumps the fluids by converting the mechanical power (rotational energy)  into the pressure energy of the fluid flow. This mechanical power generally supplies by the electric motor or engine. A centrifugal pump uses a centrifugal force to pump the fluids. Therefore, it is known as a centrifugal pump.

It is a simplest type of hydraulic equipment that uses in a wide variety of industries and in many everyday appliances to move fluids from low to high-pressure areas. It uses an impeller to pump the fluid or water from one location to other. In 1475, engineer Francesco Di Giorgio Martini designed a centrifugal pump as a mud lifter device. 

The actual centrifugal pump was only discovered in the 17th century. Next, Denis Papin designed a centrifugal pump with straight blades. British discoverer John Appold invented a curve vane centrifugal pump in 1851.

These types of dynamic pumps mostly use in the food and chemical industries to efficiently pump viscous liquids. These pumps are cheaper than positive displacement pumps. In simple words, it is a brilliant pump that can work efficiently in a different application.

Centrifugal pumps are very common all over the world industries. The main reason for their popularity is that these pumps have no power loss due to friction. This dynamic pump has a simple design and very easy to control. They don’t have leakage and heat transfer problems. This is the reason they get preference over the positive displacement pump.

Working Principle of Centrifugal Pump

The centrifugal pump working principle is according to the basic principle of the angular momentum principle which states that the change in the angular momentum of a revolving element is equivalent to the applied force. It represents, when a specific quantity of the fluid rotates due to an external force (force provide by an electrical motor or a turbine), a centrifugal force appears on the fluid, which further converts the fluid speed into pressure. Some part of this energy converts into the fluids’ kinetic energy.

Centrifugal Pump Working

The working of a centrifugal pump is almost similar to the centrifugal compressor but there is only a difference of working fluid. A centrifugal pump works in the following way:

• First of all, mechanical power is provided to the pump impeller by an electric motor or engine. The impeller directly connects with the electric motor through a shaft and reciprocates with the motion of the motor shaft. 
• When the impeller starts rotating, a vacuum starts generating inside the impeller’s eye. Due to this vacuum, the water starts to enter inside the eye in the axial direction.
• As the water enters in the eye, the water strikes the blades of the impeller. The impeller rotates the water radially and axially outward with the help of centrifugal force. This impeller continues this movement of water until it passes through all its components. 
• The impeller blades convert the kinetic energy of the water into its speed and increase the water speed.
• After passing through the impeller, the water enters into the diffuser area. This diffuser slows down the water by reducing its speed. It converts the speed of the water into pressure energy. After increasing the desired pressure, the water discharges through the pump outlet and transfer it into the desire position.

In this way, a centrifugal pump increases the pressure and pumps the different fluids. 

In simple words, in a centrifugal pump, fluid or water rises to a certain height due to the centrifugal force acting on these fluids or water. Therefore, this pump knows as a centrifugal pump. And this a complete working principle of the centrifugal pump.

For better understanding, watch the below-given video of the centrifugal pump

Major Parts of Centrifugal Pump

The major components of the centrifugal pump are given below in detail.

1) Casing

The casing is a narrow air passage around the impeller. It designs in such a shape that it converts the fluid kinetic discharges by the impeller outlet energy into pressure energy before the fluid exits the casing and inserts into the discharge pipe. The casing includes in the major components the centrifugal pump 

There are further three main types of casing.

(a) Volute Casing:

It has a spiral-type design. The volute casing has a gradual increase in the flow area. As the flow area increases, the speed slows, and the pressure of the fluid increases. This type of casing is given in the above diagram.

(b) Vortex Casing:

The vortex housing introduces a circular cavity between the casing and impeller. It uses to avoid energy loss due to the creation of swirls. These types of casings have high efficiency than volute casings. 

(c) Guide Blades Casing:

In this type of casing, the runner surrounds with the help of a different number of guide blades. These blades attach around a ring that is known as a diffuser. The guide blades design in such a way so that it does not affect the water exiting the impeller as it enters the diffuser. As the area of these blades increase then the water velocity reduces and its pressure energy increase. Mostly, the casing remains concentric with the impeller.

2) Suction Pipe

The bottom side of the suction pipe immerses in the water to that we want to lift while other side connects with the inlet of the centrifugal pump.

This part of the centrifugal pump has a foot and strainer valve at its bottom end. The role of these valves is to remove debris like sands, leaves, and allow the water to flow upwards.

3) Rotating Parts

These parts of the centrifugal pump consisting of an impeller and a shaft:

i) Impeller:

The impeller includes in the most important components of the centrifugal pump. It increases the pressure and speed of the fluid. The impeller gives centrifugal acceleration to the fluid. It further divides into the below-given parts.

a) Open impeller:

The impeller has no crown and bottom plate. The open impeller can be used to remove liquids that contain solid particles, like water having paper pulp or sand, e.tc.

b) Close impeller:

These impellers have cover plates on both sides of the blades. The close impeller uses to obtain pure water.

c) Semi-open impeller:

This type of impeller has only a base plate, but it doesn’t have a crown plate. These impellers are for the fluids having loading debris.

ii) Shaft:

The shaft uses to turn the impeller. It designs to transmit the torque generated when starting and operating the impeller and other revolving parts.

iii) Shaft Sleeve:

The sleeve prevents the shaft of the pump by leakage and corrosion. One end of the sleeve must be sealed.

4) Delivery Pipe

This part of the centrifugal pump uses to lift fluid to the required area. One end of the delivery pipe connects with the outlet of the pump, and the other end connects with the height where we want to transfer fluid.

Types of Centrifugal Pump

There are different types of centrifugal pumps that are widely using in different industries all over the world. These pumps divide according to the number of impellers, type of casing, orientation, and stages. But major types of the centrifugal pump are given below. A centrifugal pump has the following major types:

1. According to the number of impellers
2. According to the Casing
3. According to the orientation of the fluid 
4. According to the position of the pump

1) Types according to the number of Impellers

Depending on the number of impellers, the centrifugal pump can be divided into a single-stage and multistage pump.

• The multistage centrifugal pump types have more than one impeller—the impellers of the multistage pump linked in series in the same housing.
• On the other hand, single-stage pumps have a single impeller that is mounted on the shaft.

2) According to the Casing Type

According to the casing type, the centrifugal pumps have the following types:

i) Turbine Pump

This pump includes in the most famous types of centrifugal pump. This dynamic pump consists of different numbers of blades that mount on the impeller. The diffuser ring on which these blades mountain and blades are stable and the distance between the blades determines the liquid flow direction. The fluid emerging from the impeller flows by these cavities at high pressure. After exiting the blades, the liquid enters into a housing with a volute, concentric or circular shape. The big advantage of these pumps is that they can change 75% of the kinetic power into pressure. These pumps have a high cost.

Advantages and Disadvantages:

Advantages:

• These pumps have a high head
• It is reliable
• It has a compact design
• Turbine pump provides excellent handling of a gas-liquid mixture

Disadvantages:

• The turbine pump has a low flow rate
• It doesn’t have any easy method to adjust the performance
• It has a tight internal clearance that requires water without contaminations

ii) Volute Pump

The impellers of these pumps are covered with a volute chamber. These volute housing can be shaped so that fluids having the same speed exit the impeller and enter the pump. With the above design, the energy loss is minimal. In these pumps, the kinetic energy can’t convert into maximum valuable potential energy.

Advantages:

• It has a simple design
• The volute pump has a low price
• It increases the fluid pressure through the volute casing instead of a diffuser. Therefore, there is no need of a diffuser

3) According to the Orientation of the Fluid

Depending on the direction of the fluid flow through the impeller, the centrifugal pump has the following three types.

a) Radial Pumps

In these dynamic pumps, the fluid or water enters axially while discharges radially. It is most commonly used in different industries.

Advantages and Disadvantages of Radial Pump:

Advantages:

• It provides pulsation free flow
• Uses for many applications
• It is available in various designs

Disadvantages:

• This pump uses a rotation of the impeller to move a fluid instead of the suction process
• It has no suction power

b) Axial Pumps

Main article: Axial Pump

In these pumps, water enters into the pump radially while discharges axially due to that these pumps are called axial flow pumps.

Advantages and Disadvantages of Axial Pump:-

Advantages:

• It has the highest flow
• It can adjust for best efficiency at different conditions

Disadvantages:

• It has low discharge pressure and low head
• It is not best for suction lift

c) Mixed flow Pumps

The name of this pump represents an intermediate direction between radial (vertical to the axis) and axial (along the axis). In these pumps, water moves along the axis of the impeller till half a distance after that, it starts moving vertically to the axis.

Advantages and Disadvantages:

Advantages:

• It has simple operation
• You can start it directly

Disadvantages:

• It requires large space for installation

4) Types According to the Position of Centrifugal Pump

The centrifugal pumps have the following types according to the pump position:

a) Horizontal Centrifugal Pump

The horizontal pumps mostly design to deliver the liquid at very high speeds with a direct drive motor. These centrifugal pump types can easily ensure an efficient fluid flow. These pumps have top-quality performance. Therefore, these pumps seal very tightly, and these are environmentally protected. Due to the function of these pumps, they show long-lasting performance, such as excellent productivity and high-quality materials.

These pumps provide a cost-effective solution to a wide variety of reliable water applications. These pumps are easy to install and maintain.

Advantages and Disadvantages:

Advantages:

• It has easy maintenance than a vertical pump
• Smooth operation
• It has low noise
• Low failure rate

Disadvantages:

• It requires large space for installation
• It can’t fit in a low space area
• A horizontal pump has a complex installation because it needs precision adjustment after installation

b) Vertical Pumps

These pumps operate by a motor. A vertical centrifugal pump has a high water flow rate. These types of negative displacement pumps are appropriate for the high-speed transport of chemicals. The open pump impeller also enables very dirty liquids to be used.

This negative displacement pump, also known as a cantilever pump. It uses a bearing support device to drop the vortex into the water tank, and the bearings are attached outside the water tank. It also uses a shaft for rotation. These pumps use a throttle sleeve to close the shaft. The vertical pump has maximum temperature and thickness.

Advantages and Disadvantages:

Advantages

• It has a small footprint
• It has small size
• A vertical pump can fit in tight spaces
• This pump is best for high pressure and high-temperature fluids
• It doesn’t have priming problems
• It is very efficient for low flow and high head applications
• Provides a continuous flow rate

Disadvantages:

• The vertical pump has a difficult maintenance
• It has more noise than a horizontal pump
• It can’t deliver large power

c) Submersible Pump

Main article: Submersible Pump working

Other names of submersible pumps are rainwater pumps, sewage pumps, and septic tanks. These dynamic pump types are used for rainwater, municipal, commercial, household, land, and industrial purposes. These pumps primarily use to supply grey water, black waste, underground soil, well water, rainwater, commercial, sewage, rainwater, chemicals, food, and other moisture.

This type of pump uses in a variety of impellers like convection pumps, closed pumps, grinders, single-channel pumps, spiral pumps, clippers, and multi-stage pumps. The choice of these pumps mainly depends on the fluid high head and low flow or low head and high flow rate.

Applications of Centrifugal Pump

1. These pumps use in different buildings for pumping water from one place to another.
2. This type of dynamic pump use in refrigerants and coolant recirculation.
3. These pumps use in different fertilizer companies.
4. They use for drainage, irrigation, and sprinkling.
5. Centrifugal pump uses in the oil industry for pumping, slurry, mud, and oil.
6. This article is about the working principle, types, and components of the centrifugal pump.

Advantages and disadvantages of Centrifugal Pump

Advantages	Disadvantages
A centrifugal pump has easy maintenance than a reciprocating pump	It has cavitation problems
It requires less space for installation	It requires additional priming
It has small size	Shaft misalignment issues
Deals with large volume fluids	Impeller damage issues
These pumps have the capability to pump sensitive as well as hazardous fluids.	It can’t operate high viscous fluids
There is no fear of loss due to friction	It can’t operate the high head
This pump doesn’t have leakage problems	Wear ring damage issues

How to choose a centrifugal Pump?

Following are some factors that you must consider for the selection of a centrifugal pump:

• Working Fluid Viscosity: The fluid viscosity plays an essential role in the selection of a centrifugal pump. Before selecting a pump, you should decide whether you want to pump low viscosity fluids or high viscosity fluids. A centrifugal pump is best suitable for pumping low viscosity fluids.
• Specific density and gravity of working fluid: You must consider the gravity and specific density of the fluid to select the pump. Because if you want a fluid other than water, then you must consider these factors.
• Operating temperature and pressure:  The fluid pumping situations such as pressure and temperature play a vital role in selecting a pump. E.g., high pressure and temperature may need special seals, special gasket, and mounting design.

Why priming is required in Centrifugal Pump

The priming is compulsory for a centrifugal pump because it can’t pump low-density substances such as gas and air to the discharges valve and can’t generate the desired suction pressure for the required liquid or water. If you will not prime the pump, the pump pressure can’t suck water from the reservoir through the inlet pipe.

Due to this reason, priming is very important for centrifugal pumps. Otherwise, the pump runner may make contact with air and water bubbles during working, which can lead to cavitation and a lack of water or other liquid supply. Due to cavitation problems, the impeller blade may damage badly and can cause pump failure.

How do you prime a centrifugal pump?

Following are the steps to prime a centrifugal pump:

1) When the suction delivery is underneath the Pump:

Follow the below-given steps to prime a centrifugal pump if the suction delivery is underneath it.

• Shut the outlet isolation valve.
• Open the air vent inside the housing.
• Open the valve in the external discharge pipe so that only water emerges from the outlet valve.
• Shut the outlet valve.
• Shut the external supply pipe.

2) When the Suction delivery is over the Pump:

Use the following steps to prime a centrifugal pump when the suction or inlet delivery is over the pump:

• Open the inlet isolation valve.
• Open the air vent on the inlet and outlet pipe so that only water discharges from the outlet valve.
• Shut the air vents.

Difference between Centrifugal Pump and Reciprocating Pump

The major difference between a centrifugal pump and a reciprocating pump is given below:

Centrifugal Pump	Reciprocating Pump
It is a type of the dynamic pumps.	It is a type of positive displacement pump.
A centrifugal pump uses an impeller for increasing the water pressure.	A reciprocating pump increases the pressure of the fluid by using a piston.
This pump has priming problems.	This pump doesn’t have priming problems.
In this pump, the fluid discharges continuously.	The fluid in this pump doesn’t discharge continuously.
The pressure increases due to a reduction in the flow rate.	In this pump, the pressure doesn’t affect the flow rate.
Mainly, this pump utilizes for transferring high viscous fluids.	It uses for transferring low viscous fluids.
It has low efficiency.	It has high efficiency than a centrifugal pump.
The delivery rate is inversely proportional to the fluid viscosity.	In this pump, fluid viscosity doesn’t disturb the discharge rate.
These pumps have low weight than reciprocating pumps.	They have high weight.
At the lower head, this pump provides higher discharge.	It provides a high head at a low discharge rate.
These have a low price.	These have high price than centrifugal pumps.
It requires lower maintenance.	It requires high maintenance.
It has easy installation.	This pump has a complex installation than a centrifugal pump.
These pumps mostly use for domestic applications.	These pumps use for industrial applications.

FAQ Section

Who invented the centrifugal pump?

Denis Papin invented the first true centrifugal pump in 1687.

Where are the centrifugal pumps used?

The centrifugal pumps use for the following applications

• Power plants
• Refrigerants
• Coolant recirculation
• Oil refineries
• Drainage
• Irrigation
• Sprinkling

Which motor is used in the centrifugal pump?

A centrifugal pump uses an induction motor.

What are the main parts of centrifugal pumps?

A centrifugal pump has the following major parts:

1. Impeller
2. Casing
3. Diffuser
4. Inlet and outlet valves

See More:

1) What are the different types of Pumps?

2) Dynamic pump and its types

3) Positive displacement Pump and its types