What You Need to Know About the Centrifugal Pump

Posted on Dec 21, 2020

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centrifugal pump

A centrifugal pump is a device that is used to deliver fluid with high pressure and high flow rate by the rotating motion of the one or several impellers inside, and they are widely used in a variety of applications.

What is a centrifugal pump?

A centrifugal pump is a device that is used to deliver fluid with high pressure and high flow rate by the rotating motion of the one or several impellers inside. The centrifugal pumps are widely used in a variety of applications, since they welcome any type of fluid with low viscosity, except for a few other kinds.

There are a variety of applications that the centrifugal pumps are preferred to be used. From the domestic, municipal, commercial, agricultural, to the industrial usage, they can work efficiently with the centrifugal force that the impellers provide when they are triggered by the motors with sufficient horsepower. 

As the variable environments of the applications that the centrifugal pumps are dedicated to, they can be presented with some different forms in the discs that the impellers are attached to, including open, semi-opened, or enclosed impellers.


How does a centrifugal pump form?

A primed centrifugal pump would be connected to the piping by the suction inlet, which is the entrance of the impeller and where the fluid is sent from. Wrapped inside the external pump casing, there are one or several impellers, and each is formed by several curved vanes that are serially around the eye of the impeller. 

Moving outward from the impeller, there may be diffuser vanes or a volute casing. The former are stationarily set around the circumference of the impeller. The latter allows the fluid to flow radially out of the impeller, and be sent from a curved funnel with an increasing cross-sectional area toward the discharge outlet, where the fluid is delivered out to its applications.

A long cylindrical pump shaft sits in the middle of the impeller, which penetrates through the pump casing and acts as the axis of the impeller. There are a series of mechanical seals placed around the pump shaft at the back of the pump casing, in order to prevent leakage of the fluid. In addition, the mechanical seals between the pump shaft and bearings hold the shaft in place, so as to stabilize the shaft within the bearings.

:: Read more : What Is Multistage Centrifugal Pump - Types Compared and Explained


How does a centrifugal pump work?

The working principle of a centrifugal pump starts from the suction inlet. If the suction inlet is well-primed with the piping, then the fluid would be constantly delivered from the piping to the suction inlet.

Once the fluid successfully passes through the suction inlet, it would enter the eye of the impeller. With the motor turning in the centrifugal pump, the electrical energy can be converted into the kinetic energy, and therefore makes the pump shaft and impeller rotate. When the impeller starts to rotate, followed by the fluid, the flow rate would be influenced by the constancy in the delivery of fluid from the piping.

Then the centrifugal force moves the fluid radially. When the fluid impacts the diffuser or the volute, the pressure of the fluid would then be increased. For the multistage centrifugal pumps, which have multiple impellers surrounded by the diffusers, the pressure of the fluid would be gradually increased and reached to the highest one stage after another. After that, the pressurized fluid would be sent out along the diffuser or volute through the discharge outlet, and the procedures are finished.


What are the pros and cons of a centrifugal pump?


● pros

The centrifugal pumps are usually compared with the other type of the pumps called the positive displacement pumps, which work by a different principle. The positive displacement pumps are used for fluids with high viscosity at lower speeds, and provide a fixed volume of fluids for their applications. Since the centrifugal pumps work with relatively high speeds, the efficiency of their works considerably exceeds that of positive displacement pumps. 

In addition, a well-primed centrifugal pump can effectively sense pressure differentiation from the fluid that it receives, and further increase or decrease the flow rate as is required. In contrast, for a positive displacement pump, its ability to sense the changing of fluid pressure is weaker than the centrifugal pump, which makes it ineffective to work on fluid with low viscosity.


● cons

The weakness of a centrifugal type is in the viscosity of fluids that it can effectively work with, which is because of the construction and the high speed of operation. The key of a centrifugal pump is the impeller, which consists of several curved vanes. When the substances that are contained in the high viscous fluid pass through the vanes, they may be obstructed, which not only makes the impeller malfunction, but also causes premature failures. 

Even though the slightly high viscous fluid is able to pass through the impeller of the centrifugal pump, the high-speed rotation of the impeller may cause damage to the shear-sensitive mediums, which also cause failures of the operation. That’s the reason why positive displacement pumps are preferred to work on fluid with higher viscosity.


Where can a centrifugal pump be applied?

As mentioned above, there are a variety of applications that the centrifugal pumps are fit for, and the wide range of applications can be categorized into domestic, municipal, commercial, agricultural, or industrial usage as below.


● Domestic centrifugal pumps

In this category, the most common one has a lot to do with the water supply system. From the water pressure booster pumps that are used to increase the pressure of water for daily use, to the circulating pumps that are specialized in recirculating hot water in conjunction with the water heater, the centrifugal pumps work well in providing water to these applications.


● Municipal centrifugal pumps

The municipal centrifugal pumps are dedicated to water and wastewater processing plants, which deal with the discharging of wastewater. Also, the centrifugal pumps can be used in the fire protection sprinkler systems for putting out the fire caused accidentally.


● Commercial centrifugal pumps

In the commercial centrifugal pumps, the supply of water is the most common as well. Besides, they can also be used in the air conditioning systems, which improve the quality of air spread to the atmosphere.


● Agricultural centrifugal pumps

The agricultural centrifugal pumps can be seen in the irrigation of the plants, since the plants require not only sunlight, but also constant water supply in order to grow up.


● Industrial centrifugal pumps

For the industrial usage of the centrifugal pumps, they are widely applied in the manufacturing, chemicals, pharmaceutical, food production, or aerospace industries as well.


Conclusion

A centrifugal pump works by a simple principle, which utilizes the centrifugal force when the impeller inside the pump rotates, to move the fluids with low viscosity at high flow rates and high pressure efficiently. 

The construction of a centrifugal pump can be either open, semi-enclosed, or enclosed impeller, with a volute or diffuser around the impeller. Furthermore, the several impellers and diffusers can make up multistage pumps as well. 

These variations of construction in combination with the natural operating principle make the centrifugal pumps be widely used in various applications, whether for domestic, municipal, commercial, agricultural, or industrial usage.

 

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