Centrifugal Pumps Explained
Pumps are mechanical devices that move gases and liquids. While these devices use several different mechanisms to transfer fluids from one point to another, a centrifugal pump is one of the most popular and commonly used pumps in industries to typically transport low viscosity fluids. This guide provides an overview of the centrifugal pump, its working principle, and some of the popular applications to help you select the right pump for your specific fluid transport requirement.
What is a Centrifugal Pump?
A centrifugal pump converts the mechanical energy of the fluids into hydraulic energy using centrifugal force. This energy transfer happens through an impeller installed inside the pump, which increases the fluid’s velocity and pressure and also directs the fluid towards the pump outlet.
From power generation, oil & gas, mining, and agriculture to chemical and pharmaceutical manufacturing, centrifugal pumps find applications across a range of industry verticals. These rotating machines offer higher efficiencies, handle large fluid quantities, and adjust their flow rates over a wide range. Due to their simple design, centrifugal pumps are also easy to operate and maintain.
How does a Centrifugal Pump work?
A centrifugal pump consists of an impeller, which is a shaft-mounted rotor consisting of a series of curved vanes. A circular casing houses the impeller. In order for the centrifugal pump to work, fluid enters from the center of the impeller, called ‘eye.’ The impeller receives power from an external energy source, usually a motor, which causes the shaft and the mounted impeller to rotate.
The rapid rotation of the impeller generates centrifugal force, which causes the fluid entering from the center to move rapidly along the impeller vanes, which increases the fluid velocity. As the high-velocity fluid exits the impeller, it is made to flow through stationary volutes within the pump casing. These volutes convert much of the increased velocity of the fluid into pressure. The casing profile finally directs the high-pressure fluid towards the discharge point of the pump.
The mechanism described above is of a single-stage centrifugal pump, which indicates one impeller and one volute. A multistage centrifugal pump consists of multiple impellers and volutes to meet different pressure head requirements according to the specific application.
Factors Affecting the Performance of Centrifugal Pump
When selecting a centrifugal pump for your application, consider the following factors to ensure effective and efficient performance.
A centrifugal pump is suitable for low viscous fluids. Due to the unique pumping action, high-viscosity fluids resist flow along the impeller vanes. High pressure is required to maintain the desired flow rates, which consumes more energy and leads to inefficient pump performance. It is also important to consider the specific density and gravity of the fluid, as heavier fluids will require the pump to work more.
Priming and Supply Pressure
Unlike positive displacement pumps that can suck the fluid directly for the intake, centrifugal pumps require initial priming with the pumped fluid, which is usually achieved through a vacuum device. These pumps are also not suitable in cases where the supply pressure is intermittent. Inconsistent supply pressure will result in variable flow, and hence, the pump will not be useful where an accurate flow rate needs to be maintained.
Net Positive Suction Head (NPSH)
NPSH is another requirement when using centrifugal pumps for moving fluids. The term defines the necessary pressure required at the suction side of the pump to ensure constant flow rates and is high enough to avoid cavitation. Cavitation is a phenomenon that refers to the formation of bubbles or cavities in the fluid due to low pressure around the impeller. If the bubble formation continues for a longer period of time, it can affect performance and pump life.
To ensure efficient pump performance and avoid cavitation, manufacturers provide NPSH data in the form of centrifugal pump performance curves that can help you identify Net Positive Suction Head Required (NPSHR) against the calculated Net Positive Suction Head Available (NPSHA).
Applications of Centrifugal Pumps
A centrifugal pump finds applications across a range of industry verticals requiring movement of fluids. Here are some of the major applications of these pumps.
- Pumping water and other low to medium viscous fluids
- Domestic and industrial water supply
- Sewage and slurries pumping
- Fire protection sprinkler systems
- Food and beverage production
- Crude oil and slurry pumping in oil & gas industries
- Refrigeration and air conditioning
- Handling chemicals like solvents, acids, bases, oils, organics, etc.
- Transferring lactose and other drugs in the pharmaceutical industry
- Irrigation and drainage
As the oldest and largest pump distributor in the Northeast, Hayes has the right selection of industrial pumps, as well as commercial and municipal pumps to fit your needs. Talk to one of our engineers to get assistance in selecting the right centrifugal pump for your unique fluid transportation requirements.