How does a centrifugal pump work?

Posted on Jul 13, 2020

What is a centrifugal pump?

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

There are a variety of 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 and powerful horsepower.

As the variable environments of the applications that the centrifugal pumps are dedicated to, they can be presented with some different forms in 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 fluids are sent from. Wrapped inside the external pump casing, there is one or more impellers, and each one of them 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 that are stationarily set around the circumference of impeller, or a volute casing that allows the fluids flow out radially from the impeller, and be sent out from a curved funnel with an increasing cross-sectional area toward the discharge outlet, where the fluids are delivered out to its applications.

A long cylinder pump shaft sits in the middle of the impeller, which penetrates through the pump casing and acts as the axis of the impeller. On the other side of the pump casing, there are a series of mechanical seals that are placed around the pump shaft at the back of the pump casing, in order to prevent leakage of the fluids. Outside the pump shaft and the mechanical seals, there are bearings that hold the pump shaft in place.


How does a centrifugal pump work?

The working 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 is successfully passed through the suction inlet, it would enter the eye of the impeller. With the operating of the motor of 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 of the delivering of fluid from its source, which is the piping.

Then the centrifugal force moves the fluid radially. When the fluid impact 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 reaches to the highest through the passing of each stage. 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 works by a different principle. The positive pumps are used for fluids with high viscosity at lower speeds, and provide with fixed volume of fluids for their applications. Since the centrifugal pumps work with relatively high speeds, the efficiency of their works considerably exceeds the positive displacement pumps.

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

● Cons

The weakness of a centrifugal is in the viscosity of fluids that it can effectively work with, which is because of the construction and the high speed of operation. Since 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 fluids 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 rotating of the impeller may cause damage to the shear-sensitive mediums, which also cause failures of the operation. That’s the reason why the fluids with higher viscosity would prefer to be worked with the positive displacement pumps.


Where can a centrifugal pump be applied?

As the introduction in the beginning has mentioned, there are a variety of applications that apply the centrifugal pumps to work, and the wide range of applications can be categorized into domestic, municipal, commercial, agricultural, or industrial usage that we are going to discuss here.

● Domestic centrifugal pumps

In this category of the applications of the centrifugal pumps, the most common one has a lot to do with the water supply system. Form the water pressure booster pumps that are used to increase the pressure of the water for daily use, to the circulating pumps that work for recirculate 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 that is caused accidentally.

● Commercial centrifugal pumps

In the commercial centrifugal pumps, the supplying for water is the most common as well. Besides, they can also be used in the air conditioning systems that improve the quality of air that is delivered in the atmosphere.

● Agricultural centrifugal pumps

The agricultural centrifugal pumps can be seen in the irrigation of the plants, since the plants require constantly water supply in order to be grown up.

● Industrial centrifugal pumps

In the industrial usage of the centrifugal pumps, they can be easily 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 multistage pumps as well.

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

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