How Do Submersible Pumps Work?Ken Thayer | November 17, 2017
If you use a well for drinking or irrigation or you’ve needed to remove standing water, you’ve probably used a submersible pump. Submersible pumps are a type of centrifugal pump designed to operate while fully submerged. They are also referred to as sub pumps or electric submersible pumps (ESP).
A wide variety of submersible pumps are available for various applications. Regardless of the pump type, there are some features they all share. In order to operate, they must be completely submerged in the pumped media and the pump motor must be completely sealed.
Submersible Pump Types
Well water pumps are a variation of well pumps first used in the oil industry in the 1920s. They are cylindrical in shape so that they can easily be lowered down a well and are typically 3” - 4” in diameter. Compared to depth limitations of other types of pumps, submersible well water pumps can operate at depths up to 400 feet. There are two types of potable water pumps, shallow-well and deep-well.
Dewatering pumps are used to remove standing water in construction, mining and sump applications. Dewatering pumps are designed for water or water with light suspended solids.
Sand, sludge and slurry pumps are heavy-duty pumps designed for the demanding application of removing large, stringy, fibrous or abrasive solids.
Solids-handling pumps are designed for handling materials such as mud, raw sewage, viscous liquids, wood chips, wastewater and other solids. Shredder pumps, also referred to as cutter pumps, cut or shear the material prior to pumping.
Submersible pumps for use in oil wells are typically electrical submersible pumps, driven by electric power. ESPs are multistage centrifugal pumps with a three-phase induction motor and a sealed chamber section. They also have a surface power control system that supplies electricity to the pump through a power cable.
In submersible pumps, the sealed motor turns an impeller, which is enclosed in the pump housing. The pump may include an intake screen, which filters out anything that is too large to pump. As the impeller rotates, pressure pushes the media into the pump inlet and the impeller accelerates the fluid and forces it into the discharge line. It is important to keep submersible pumps fully submerged while operating as they are not designed to work in air. As the pump is submerged, it eliminates the need for priming the pump and prevents cavitation.
Submersible pumps should not be confused with jet pumps, which are also used in well applications. Jet pumps are centrifugal pumps with a venturi nozzle attached at the discharge outlet. They operate based on Bernoulli's principle, using constriction to reduce pressure and provide suction. After the pump is primed a motive fluid is pumped through a standard centrifugal pump and enters an ejector. At the throat of the converging section of the ejector, the pressurized fluid is ejected at high velocity. This creates a low pressure (vacuum) at the throat, drawing the target fluid (from a well or other source) up into the nozzle.
Submersible pumps should be used for wells with depths of 25 feet to 400 feet. Shallow well jet pumps should be used for wells 25 feet or less and deep well jet pumps can be used for depths between 25 feet and 110 feet.