What You Need to Know About Flooded Suction Pumps

Learn about the advantages and deployment options for flooded suction pumps in addition to how they are different to submersible pumps.
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Common type of flooded suction deployment

A flooded suction pump, like any other pump, is used to move liquids from one point to another. The major difference between a flooded suction and submersible pumps is that the flooded suction pump is gravity fed and mounted outside of the tank or hopper which holds the slurry or fluid. The flooded suction pump is typically positioned at the bottom or underneath the tank or hopper so that gravity will constantly feed the pump fluid while the pump is in operation. This ensures the pump is always primed and ready to operate without losing prime or taking in too much air.

Flooded suction pumps can be used in many different applications. They also have their advantages and disadvantages, which must be taken into consideration when making a slurry pump selection for your application.

Flooded suction pumps also are easier and quicker to turn on and off because the chamber and piping inside of the pump are always filled with water allowing the pump to always be primed. This can also be a disadvantage since there’s no way to completely block off the suction within the pumping chamber unless there’s a separate suction valve.

What is a Flooded Suction Pump?

As the name suggests, a flooded suction pump is designed to work by being gravity fed fluid, thus not requiring a vacuum pump for priming. Flooded suction pumps consist of a pump and motor, mounted outside of the liquid to be pumped or processed. These setups usually involve an electrically driven pump with a variable frequency drive (VFD) or a soft-start. A VFD makes sure that the pump startup is monitored correctly and can also monitor the speed or rpm of the pump in order to control the flow and pressure of the pump. A less common power source for a flooded suction pump is a direct drive diesel driven pump. This can be found in outside hopper pump applications for sand and gravel pumping, mining, drilling mud pumping, etc.

It is important to make sure the material that will be pumped is not too thick or viscous, otherwise, it may have a hard time correctly feeding to the pump, resulting in air pockets. The fluid needs to be constantly feeding the pump to prevent damage to the pump and equipment. If the material is too thick, a vacuum pump or self-priming pump may be necessary to help pull the fluid into the pump to prevent too much air buildup.

Advantages and Disadvantages of Flooded Suction Pumps

The flooded suction pump offers several major advantages over other types of pumps:

Priming: They don’t have to be primed. They are automatically primed because the fluid they will be pumping is gravity fed directly into the pump, always keeping it primed.

Efficiency: A flooded suction pump has the head pressure of liquid on the suction end to help it operate. It doesn’t need to use as much energy in drawing liquid into the pump and is, therefore, more efficient.

Maintenance & Accessibility: Since the pump is mounted outside of the tank or fluid, routine maintenance is much easier to accomplish because the pump is capable of being worked on immediately, unlike submersible pumps which must first be removed from the fluid. However, a method is needed to block off the suction and supply to allow for drainage of the volute for inspection.

There are also some disadvantages to contend with:

Potential to lose Prime: If the slurry mixture is too thick or viscous, it may not easily feed into the pump which can cause the pump to lose prime. Thus, the mixture needs to be fluid enough to constantly feed the pump to prevent this from happening.

Corrosion: Prolonged exposure to a liquid of any sort will lead to corrosion. Submersible pumps are often used to handle liquids that are corrosive and abrasive. Seals are especially prone to corrosion, which leads to leaks and damage to the motor. To counteract corrosion these pumps need to be made of corrosion-resistant material, which can make them more expensive than other types of pumps of the same capacity.

Wherever possible, flooded suction pumps should be inspected as often as possible. In this way, any necessary repairs can then be carried out to prolong the life of the pump.

Flooded Suction Pump Applications

Flooded suction pumps are ideal for pumps that need to be mounted outside of the liquid and positioned below the tank so that it can be gravity fed, which will keep the pump primed.

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