In many fluid pumping applications, pumps have to be placed above the level of liquid, allowing air into the line, which can lead to challenges such as overheating and pump failure. To avoid these issues, self-priming pumps are used to evacuate the air before moving liquids. At Gainesville Industrial Electric (GIE), we offer a variety of self-priming pumps to suit the needs of various applications.
Self-Priming Pumps 101
What Is Self-Priming?
Pumps that are partially or completely above the fluid level allow air into the suction line, which must be evacuated or displaced before the pump can move the liquid. Self-priming pumps are capable of removing air at startup before beginning its normal pumping functions.
Are Centrifugal Pumps Self-Priming?
Centrifugal pumps do not have seals between the suction and discharge sides of the pump, meaning they are not self-priming and cannot evacuate gases and air if the pump is above fluid level. To make a centrifugal pump self-priming, it can be surrounded by a tank to ensure that it is always immersed in a liquid and that it has the necessary lubrication and cooling to prevent the pump from overheating.
How Do Self-Priming Pumps Work?
To avoid the mixing of air and water, self-priming pumps create a partial vacuum to discharge water while also evacuating any air. It does this by combining the air and water during the priming process, forcing the air to rise and the water to sink or go down. Gravity then pulls the air-free water back into the impeller, where it mixes with the remaining air in the suction line.
This process repeats until all air is evacuated and a vacuum forms in the suction line. Once this happens, atmospheric pressure forces the water into the suction line and towards the impeller to allow pumping to begin.
Self-priming pumps are used in various industrial and commercial facilities, from steel mills, power plants, and sewage treatment facilities to wineries, breweries, and more. Common applications include:
Pumping water, fuels, clear or gray water, raw sewage, industrial wastewater, and more
Liquid transfer systems
Basement floodwater pumps
Bailing out boats
Increasing water pressure
Self-Priming Pump Solutions
At GIE, we offer the following self-priming pump solutions:
FPS self-priming pumps are built to handle clear water and solids. They can handle solids up to 3 inches in diameter or length, and the pumps are built with self-priming mechanisms to mitigate the risk of becoming air-bound. At GIE, we provide FPS self-priming pumps in electric drive, frame mount drive, and gas engine drive varieties. Gas engine varieties can provide up to 27 horsepower, depending on the model.
These self-priming pumps can handle clear water for a variety of commercial and industrial applications. They are available in portable contractor pump styles, with enclosed impellers, and with bronze fittings to integrate with virtually any applicable system. Gould’s self-priming end suction pumps can handle up to 250 PSI and fluid temperatures of 250°F.
These self-priming pumps are designed to be placed anywhere from 10 to 20 feet above the fluid level without the risk of becoming air-bound. Along with clear water, they can handle solids of different sizes depending on the specific model chosen. Marlow specializes in vertical in-line pumps that can be used in industrial petroleum and chemical systems.
Contact GIE for Your Pump Needs
Self-priming pumps are crucial in ensuring that air does not interfere with pumping operations. At GIE, we have been providing high quality industrial electric motors, pumps, parts, and various repair and maintenance services since 1959. Our experienced staff and commitment to quality ensures products that meet or exceed customer expectations. To learn more about our self-priming pumps, contact us or request a quote today.
Centrifugal and positive displacement pumps are powerful tools that can move fluid through complex industrial and municipal systems. But it’s essential to choose the right equipment for your facility’s needs. Here, we’ll discuss the differences between the two pump types, the fluids they can handle, and some of the most popular applications of each pump.
Difference Between Centrifugal Pumps and Positive Displacement Pumps
. Fluid Transfer Mechanisms
Both centrifugal and positive displacement pumps transfer water from an inlet point to an outlet point at a controlled degree of force and quantity. However, the mechanisms they use are different. Positive displacement pumps draw fluid into a cavity, or displace the fluid, and then force the fluid out of the cavity through suction. Centrifugal, or aerodynamic, pumps have a spinning impeller that draws the fluid into the pump and forces it out of the outlet point at an increased velocity.
. Types of Fluid Transferred
Each type of pump works best with different types of fluid. Positive displacement pumps can handle highly viscous fluids, and their flow rate can increase as the fluid gets thicker. Centrifugal pumps, on the other hand, can’t handle viscous fluids as well because of the frictional losses. Also, positive displacement pumps can handle shear sensitive fluids—or fluids that change when force, stress, or pressure is applied—whereas centrifugal pumps cannot; the impellers present a risk to the fluid. Positive displacement pumps can also handle intermittently dry periods and can start without being primed by liquid in the system. Centrifugal pumps need liquid in the unit to kick-start the pressurized control.
There are several different types of positive displacement and centrifugal pumps, each of which uses slightly different mechanisms and can handle different loads but which still uses the basic concepts of positive displacement and rotational force to cause movement. Facilities should first decide whether a positive displacement or centrifugal pump is the best choice based on pressure and flow rate demands, the type of fluid being moved, and the required suction lift before choosing a specific pump type and model.
Pump Performance Comparison
One of the key differences between the performance of positive displacement and centrifugal pumps is the flow rate. Positive displacement pumps maintain a constant flow rate, even as pressure changes, but the fluid moving out of centrifugal pumps is a varying flow rate based on pressure.
. When to Use a Centrifugal Pump?
Centrifugal pumps excel at pumping thin liquids with low viscosity levels. These include water, thin oils and fuels, and chemicals. They’re the most commonly used category of pump for high-volume applications that demand high flow rates at low pressures. Some popular applications include:
Municipal water and water supply systems
Air conditioners and water circulators
Petrochemical and light fuel transfer stations
With a vortex impeller, centrifugal pumps can even handle some fluids with solids. However, they work best when pumping consistent high-volume quantities of water.
. When to Use a Positive Displacement Pump?
Positive displacement pumps, on the other hand, excel at high-pressure and low flow rate applications with viscous fluids. These pumps work well in the following applications:
Municipal sewage systems
Oil processing centers
Manufacturing centers that produce or process thick pastes and other viscous materials
Complex facilities such as food processing plants and other manufacturing facilities benefit from a mix of both types of pumps. Food processing operations will need centrifugal pumps for adding water to batches, for example, but need positive displacement pumps to control the movement of thicker compounds. Oil processing centers may need positive displacement pumps for processing crude oil while they can use centrifugal pumps for handling thinner, lighter by-products.
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