Centrifugal pumps are used to move liquid by pressurizing them using an impeller that rotates within a case.
These are the common type of pumps used to move water from one point to another.
Most people prefer using them since they move liquids at a higher pressure and they have a higher efficiency.
Before I go too deep and get caught on the details, let me share with you the main components of centrifugal pumps.
The main components of centrifugal pumps are;
- Impellers; which can be radial, backward and forward curved.
- The casing; which can be volute, vortex and casing with guide blades.
- The drive shaft with gland and packaging.
- The suction pipe with the suction valve
- The delivery pipe with delivery valve.
Now, that you know the components of centrifugal pump it’s time to learn of its types.
Types of centrifugal pumps;
Centrifugal pumps can be classified in various types of categories based on several things;
- Based on the number of impellers.
- Based on how the case is orientated.
- Based on type of impeller design.
- Based on the type of volute.
- Based on the basis compliance with industrial specifications.
- Based on where the bearing support is located.
- Based on how the shaft is placed in the pump.
1. Based on the number of impellers.
The number of impellers present in a centrifugal pump determines its type.
Different types of centrifugal pumps have different numbers of impellers.
Single stage centrifugal pumps; these types of pumps have one impeller, its design and construction is very simple. It’s one of the simplest centrifugal pumps available.
It has high performance since it operates under a high speed.
Due to their small sizes and few parts makes these pumps very easy to repair and maintain.
The main disadvantage is that it can only pump a maximum lift of 125 metres head.
Two stage centrifugal pumps; these pumps have two suction impellers that draw in the liquid to be pumped.
So, it operates under a relatively higher pressure discharge than single stage centrifugal pump.
2. Based on case how the case is oriented.
Case orientation in centrifugal pumps is different depending on the uses of the pumps.
There are two main case orientation in centrifugal pumps, which are;
- Axial split.
- Radial split.
Axial split centrifugal pumps; these are centrifugal pumps in which the volute casing is split through the centre line of the shaft. The rotor in these pump are supported between the bearings.
Axial split centrifugal pumps have a higher performance and they are very easy to maintain since the split allow access to the internal parts of the pumps.
Radial split centrifugal pumps; these pumps have splits that is perpendicularly to the shaft.
The fluid is pumped in such a way it leaves the pump in a radial direction.
They pump small volume rates but in a very high pressure.
3. Based on the type of impeller design.
The impeller design of the centrifugal pumps can also be used to categorize the centrifugal pumps.
You have to understand that the impeller is the component that creates a suction in these pumps.
So, centrifugal pumps can either have single suction or double suction.
Single suction centrifugal pumps; these are pumps that draws liquid in the pump using one end only since it has a single suction chamber.
Double suction centrifugal pump; this pump pulls liquids in the pump using two sides. It has two suction chambers which is different from single suction centrifugal pump.
The main advantage of using double suction centrifugal pump is that it’s not easy to cavitation since the pump is under the same speed and flow.
The axial thrust is canceled since one force coming from one end of the suction chamber cancels the other.
4. Based on type of volute.
Volute is a spiral like structure structure that directs the water discharged from the pump to the delivery pump.
The are two types of volutes in centrifugal pumps namely;
- Single volute.
- Double volute.
Single volute centrifugal pump; The impeller discharges the pumped liquid into one volute that is wrapped around the impeller which ends up directing that water to the discharge pipe.
Double volute centrifugal pump; this pump consists of two partial volutes with the same pressure effects and are arranged at an offset of 1800 directed to the same discharge nozzle.
Since the volutes with the same pressure effects are directed to the same discharge nozzle this aids in the balancing of radial load on the impeller.
This creates equal distribution of water in the pump as the water is being discharged.
5. Based on the basis compliance with industry specifications.
The centrifugal pumps are also categorized according to their specific standards set by a certain institute.
These standards are what specify which type of centrifugal pump should be used in a certain industry.
Some of the industry standards of centrifugal pumps are;
- ANSI pump – (American National Standards Institute).
- API pump – (American Pump Petroleum Institute).
- Nuclear Pump ASME – American Society of Mechanical Engineers).
- ISO pump specifications.
- DIN pump specifications.
ANSI pump – (American National Standards Institute) specifications, deals with specific designs of chemical pumps, which are centrifugal pumps which meet the requirements of the national American standards institute.
ANSI refers to the dimensional measure standards of the pumps.
These centrifugal pumps which satisfy the ANSI specifications are mostly used in chemical industries, paper stock, ethanol production, pharmaceutical, food processing and process plants.
API pump – (American Pump Petroleum Institute); these are the centrifugal pumps that are heavy duty than ANSI which satisfy the American Petroleum Institute specifications.
Their specifications mainly refer to the pumps construction and design. They also refer to the ability of the pumps to be able to withstand high temperature and pressure.
Nuclear Pump ASME – American Society of Mechanical Engineers); the specifications and designs that these types of centrifugal pumps satisfy the measures needed by the American Society of Mechanical Engineers when it comes to handling nuclear elements.
Their designs are mainly for the use in the nuclear power plants.
ISO pump specifications; these are the centrifugal pumps that specify requirements of end suction centrifugal pumps of a single stage, horizontal and vertical construction for general applications.
DIN pump specifications; these are the centrifugal pumps that are used for working areas that need application of high pressure discharge from the pump.
They are mostly used in industrial applications where large rates of applications are needed.
They are rarely used in building services.
6. Based on where the bearing support is located.
Where the bearing support is oriented also plays a big part in categorizing the centrifugal pumps.
According to the location of the bearing support, we have the following centrifugal pumps;
- Overhung centrifugal pumps.
- Between-bearing centrifugal pumps.
Overhung centrifugal pumps; these are the type of centrifugal pumps that use one impeller that is installed on a shaft suspended at one end of a bearing.
Between-bearing centrifugal pumps; these types of pumps use two or more impellers installed on a shaft suspended at both ends between the two bearing.
These types of centrifugal pumps are used when high flow rate, high pressure and heavy loading is to be expected by the work done by the pump.
7. Based on how the shaft is placed in the pump
Different centrifugal pumps have different shaft orientations and this is one of the factors that is also used to categorize them.
There are two type of shaft orientations in centrifugal pumps namely;
- Horizontal
- Vertical.
Horizontal centrifugal pumps; these are the types of centrifugal pumps that have their shaft oriented horizontally in between the bearings.
The main advantage of such pumps is that they facilitate easy maintenance and installation.
This feature also enables such pumps to be coupled with external accessories and devices e.g turbines and electric motors.
The disadvantages of these centrifugal pumps is that they occupy a large space and they don’t provide more net positive suction head.
Horizontal centrifugal pumps are used in water circulation, spraying systems and general purpose.
Vertical centrifugal pumps; these are the centrifugal pumps that have their shaft placed vertically within the pumps.
These types of pumps are used in areas where the fluid that need to be pumped is of high pressure and temperature.
The disadvantages of vertical centrifugal pumps is that they are difficult to maintain and install.
Vertical centrifugal pumps are used in sump, booster stations, condensate and lift stations.
Working principle of centrifugal pumps
The delivery valve is first closed and the pump is primed so that the suction pipe, casing and the portion of delivery pipe up to the delivery valve is filled with liquid completely such that there is no air pocket left.
This is to make sure that the liquid is completely compressible and it will result in the efficiency of the pumping mechanisms.
As the delivery valve is still closed, the prime mover is started so as to rotate the impeller. The rotation of the impeller creates a centrifugal force that causes suction which draws the liquid into the eyes of the impeller within the pump.
The impeller rotates until it attains its normal energy required to pump the pressurized liquid. The delivery valve is opened and the liquid is continuously sucked and impelled out of the eye of impeller by the rotating blades into the casing where the kinetic energy is changed to pressure energy.
As the pressurized liquid enters the casing, it’s directed to the delivery pipe via the delivery valve.
This process will go on as long as the impeller is still running and there is water to be pumped in the casing.
Uses of centrifugal pumps.
Centrifugal pumps are used in several areas where their main function is pressurizing liquid so that it moves from one end to another;
Centrifugal pumps are used in;
- Water management systems.
- Chemical and process plants.
- Fire departments.
- Pumping of petroleum products .
- Waste management.
- Pharmaceutical and food industries.
- Nuclear power plants.
There are many areas where centrifugal pumps are used due to their amazing capabilities.
Advantages of using centrifugal pumps
- They provide high pressure discharge.
- They are compact and small in size thus occupying a small area.
- Centrifugal pumps have the ability to handle large volume of liquids without breaking down.
- There are many types of centrifugal pumps thus making it easier for one to choose of any type depending on their budget.
- They are easy to maintain and repair because of the few understandable components.
- Centrifugal pumps can handle liquids that are under high pressure and temperatures.
- They can handle a wide range of liquids since they are corrosive resistant e.g finish Thompson’s centrifugal pump.
Thank you so much for reading this article, if you have any questions leave them in the comment section.
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