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Very Useful Information about Centrifugal Pumps

Aug. 31, 2020

Centrifugal Slurry PumpA centrifugal pump operates by transferring rotational energy from one or more driven rotors called impellers. The effect of the impeller increases the velocity and pressure of the fluid and directs it to the pump outlet. By virtue of its simple design, centrifugal pumps are well known and easy to operate and maintain

What is a centrifugal pump?

A centrifugal pump is a mechanical device designed to move fluid by rotating energy from one or more driven rotors, called impellers. The fluid enters the fast rotating impeller along its axis and is discharged through the blade tip of the impeller along its circumference through the centrifugal force. The effect of the impeller increases the velocity and pressure of the fluid and also directs it to the pump outlet. The pump housing is specially designed to compress the fluid coming from the pump inlet, channel it into the impeller, and then decelerate and control the fluid before discharging.

How does a centrifugal pump work?

The impeller is a key component of a centrifugal slurry pump. It consists of a series of curved blades. These are usually sandwiched between two discs (a closed impeller). For fluids with entrained solids, open or semi-open impellers (supported by a single disc) are preferred.

The fluid enters the impeller along its axis ("eye") and flows out along the circumference between the blades. The impeller is on the side opposite to the eye, connected to the motor through the drive shaft, and rotates at a high speed (usually 500-5000rpm). The rotating movement of the impeller accelerates the fluid through the impeller blades into the pump casing.

There are two basic designs of pump housing: volute and diffuser. The purpose of both designs is to convert fluid flow into controlled discharge under pressure. In the volute, the impeller is offset, effectively forming a curved funnel whose cross-sectional area toward the pump outlet increases. This design increases the fluid pressure towards the outlet.

The same basic principles apply to diffuser design. In this case, the fluid pressure increases as the fluid is discharged between a set of fixed blades around the impeller. The diffuser design can be customized for specific applications, so efficiency can be improved. When it is beneficial to avoid the increased shrinkage of the diffuser blades, the volute is more suitable for applications that entrain solids or high-viscosity fluids. The asymmetry of the volute design will cause greater wear on the impeller and driveshaft.

What are the main features of centrifugal pumps?

There are two main series of pumps: centrifugal pumps and positive displacement pumps. Compared with the latter, centrifugal pumps are usually designated for higher flow rates and low viscosity liquids as low as 0.1 cP. In some chemical plants, 90% of the pumps used are centrifugal pumps. However, in many applications, positive displacement pumps are preferred.

What are the limitations of centrifugal pumps?

The effective operation of the centrifugal froth pump depends on the constant high-speed rotation of its impeller. For high-viscosity feeds, the efficiency of centrifugal pumps is getting lower and lower: the resistance is greater, and higher pressures are required to maintain a specific flow. Therefore, in general, centrifugal pumps are suitable for low-pressure, high-volume, pumping applications for liquids with a viscosity between 0.1 and 200 cP.

Slurry such as mud or high-viscosity oil can cause excessive wear and overheat, which can lead to damage and premature failure. Positive displacement pumps usually run at fairly low speeds and are less prone to these problems.

Any pumping medium sensitive to shear (separation of emulsions, slurries, or biological liquids) will also be damaged by the high speed of the centrifugal pump impeller. In this case, it is preferable that the rotational speed of the displacement pump is lower.

Another limitation is that, unlike positive displacement pumps, centrifugal pumps cannot provide suction when dry: they must first be primed with pumped fluid. Therefore, centrifugal pumps are not suitable for any application with intermittent supply. In addition, if the feed pressure is variable, the centrifugal pump will produce a variable flow; the positive displacement pump is not sensitive to pressure changes and will provide a constant output. Therefore, in applications requiring precise metering, positive displacement pumps are preferred.

What is the main purpose of the centrifugal pump?

Centrifugal pumps are commonly used to pump water, solvents, organics, oils, acids, alkalis, and any "dilute" liquids in industrial, agricultural, and household applications. In fact, there is a design of a centrifugal pump that is practically suitable for any application involving low viscosity fluids.

The centrifugal pump design provides a simple and low-cost solution for most low-pressure, high-flow pumping applications, involving low-viscosity fluids such as water, solvents, chemicals and light oil. Typical applications include water supply and circulation, irrigation, and the transfer of chemicals in petrochemical plants. For applications involving high-viscosity fluids (such as heavy oil and slurries) (especially under high pressure), complex feeds such as emulsions, food or biological fluids, and where precise metering is required, positive displacement pumps are preferred. We are a slurry pump manufacturer, if you are interested in our products, please feel free to contact us.

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