A: A centrifugal pump is any pump—whether it’s submersible or above ground, that is using centrifugal force to move water, fluid, or whatever it is, from one point to another. It uses an impeller and diffuser or volute style system.
The centrifugal pump is easily the most popular choice of pump to transfer liquids of all kinds. If you ask for an explanation of what a centrifugal pump is, there’s a long answer and a short one. The short answer is it’s a pump that uses a rotational impeller to move fluid with centrifugal force.
You will find these pumps in use more than any other style in many industries. Agriculture, municipal, petroleum, chemical, and more all depend heavily on centrifugal pump usage.
A centrifugal pump is very useful because it can usually handle a large volume of fluid at a high flow rate. It also can adjust its flow rate over a wide spectrum.
They are typically designed to handle low viscosity fluids such as light oil or water. Fluids that are higher in viscosity such as 20W oil will need more horsepower on a centrifugal pump for it to work properly. For fluids on the more extreme scale of viscosity, such as oils over 30W—positive displacement pumps are the more efficient choice.
Inner Workings of a Centrifugal Pump
A centrifugal pump is used to create flow or bring a liquid from a lower level and raise it to another level. The pump works on a fairly simple mechanism. It takes rotational energy from a motor and converts it to energy in a moving liquid.
The two main components that make this conversion possible are an impeller and casing. The impeller is what generates the rotation and the casing is airtight and surrounds the impeller. Fluid enters the casing, makes contact with the impeller blades, and is pulled into the diffuser in the casing. When the fluid is passing through the impeller it gains velocity and pressure.
These factors should be considered when choosing a suitable centrifugal pump for your project:
- Fluid Viscosity – Generally, a centrifugal pump is best suited for low viscosity fluids since the action of the pump creates a high fluid shear.
- Gravity And Density Of Fluid – These two characteristics directly impact the power needed to pump the fluid being moved. The higher the density and gravity of the fluid, the more work the pump will have to do. So, when working with fluids other than water, keep that in mind.
- Operating Pressure And Temperature– Conditions such as pressure and temperature are a critical factor in any application. High-pressure pumping, for example, requires special seals and gaskets. Additionally, the casing may need to be modified to retain the pressure levels needed for high-pressure environments.
- Net Positive Suction Head (NPSH) and Cavitation – NPSH refers to the pressure a fluid exhibits on the suction end of the pump. The NSPH needs to be high enough to avoid the formation of cavities or bubbles in the fluid. It causes a pressure drop which can damage the impeller and lead to other issues.
- Vapor Pressure Of Fluid – Vapor pressure is the pressure at a given temperature where the fluid will convert to vapor. It also is an important factor to know to avoid cavitation. Accidentally dry running the pump can cause serious damage to the pump bearings.
Since pumps are used in such a wide range of applications, they come in different capacities and sizes. You also need to consider the pressure and requirements of volume for the operation you need the pump for. Horsepower is also another important factor to consider regarding the volume and discharge pressure.
Who Needs A Centrifugal Pump
Because the centrifugal pump is the go-to choice for many industries it makes sense that they are a major player across the board. These pumps are used in so many industries on a wide spectrum—it’s not like it’s all petroleum-related industries. They are used to supply water, bolster fire protection systems, sewage, and more. However, the following sectors below are the top five that make extensive use of centrifugal pumps:
- Oil & Energy – Used to pump crude, mud, slurry; also used by power plants and refineries.
- Industrial & Fire Protection – Heating and air conditioning, ventilation, boiler feed, pressure boosters, fire sprinklers.
- Waste Management– Wastewater processing, municipal plants, drainage.
- Agriculture– flood protection, irrigation, lakewater filtration.
- Chemical Industry– Hydrocarbons, petrochemical.
- Food Processing– Cellulose, sugar refining, beverage production.
Types of centrifugal pumps
Centrifugal pumps are broken down into several classifications that depend on factors such as application, construction, ISO, and design. Therefore a pump can be classified into more than one group or it can also stand on its description. Some of these groups include:
By Number of Impellers
- Single-stage – This pump only has one impeller it’s simple in design and maintenance is also simple. Geared towards large flow rates in low-pressure applications. Most often used in pumping services of high flow with low or moderate total dynamic head (TDH).
- Two-stage – As the name implies this pump boasts two impellers that operate in tandem. It’s often used for medium head applications.
- Multi-stage – Following the order, this one has at least three impellers and maybe more depending on the application. Mainly used in high head scenarios.
*What is Pump Head?
In laymen’s terms, pump head is pressure that is defined as the height a pump can raise fluid. It is important as it evaluates a pump’s ability to do the job you’re asking of it.
Type Of Case-Split
- Axial split – In an axial split pump the volute casing is split on an axis and the split runs along the centerline of the shaft. These pumps are usually mounted in a horizontal orientation for ease of access for maintenance.
- Radial split – Similar to an axial split except it is split perpendicular to the centerline of the shaft.
By Impeller Design
- Single suction – In this suction action, the single-suction impeller only allows fluid to enter the blades from one end. Its design is simple—however, it has a higher axial thrust imbalance because the flow is only coming from one side.
- Double suction – If single-suction only has flow coming from one side, obviously a double suction must allow flow from both sides. Split-case pumps are usually the type of pumps that feature double suction.
Centrifugal Pump Units
A centrifugal pump is a very efficient piece of machinery but it isn’t useful in and of itself. It needs to be coupled with other equipment to achieve its real usage. The combination of equipment that enables the pumps to work as intended is called a pumping unit.
A centrifugal pump unit at the minimum includes two main components— a pump and the driver. In most cases, the driver is an electric motor of varying horsepower. However, this isn’t always the case—some are driven by natural gas engines or steam-powered turbines.
We Carry All The Components To Build Your Pump Unit
If you need a quality centrifugal pump unit, Gulf Coast has the parts you need from industry leaders such as Goulds, Franklin Electric, and more. Contact us today and we can get your order started.