Thursday, July 27, 2017

How do Jet Pumps Work?



Jet pumps are also called ejector pumps. They are devices capable of handling and transporting all forms of motive fluid including gas, steam, or liquid. They can be considered mixers or circulators, since the intake combines multiple fluid sources. Multiple inlets are used to draw in a constant stream of fluid, using pressure to create lift through suction. The combination of intake pressure and velocity of the liquid or gas jets the media up from a well, tank, or pit through the pump to the discharge point.

Jet pumps are less efficient than typical centrifugal pumps due to such factors as friction loss, but may be more efficient when working with combined media that includes gases and in variable well conditions where the surface characteristics involve turbulence.

Jet pumps are centrifugal pumps with an ejector (venturi nozzle) attached at the discharge outlet. They function based upon the Venturi effect of Bernoulli's principle - utilizing 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.

Jet pumps consist of three sections: a centrifugal pump, a jet ejector package, and a foot valve.

The centrifugal pump generates the force which circulates the motive fluid through the ejector, typically using an impeller powered by a motor.

The jet ejector package (the nozzle, venturi, and various connections) is often separate from the pump before installation. Ejector components are carefully engineered to match the flow rate of a specific pump. During installation, it is important to read the ejector package instructions and set the package up correctly for the specific horsepower of the pump.

The foot valve is the section connected to the well or target resevoir. It receives fluid into the system and feeds the pump, filters debris and sediment from entering the system, and maintains the pump prime, preventing backflow.

Types

There are four main types of jet pumps, which vary based on application and size.

1. Deep well jet pumps are used in high volume applications, such as oil wells, which range from 800-15,000 feet in depth. The ejectors in these pumps are put down the well.
2. Shallow well pumps are used in applications where the media is close to the surface, such as residential wells. The ejectors in these pumps are bolted to the nose of the pump.
3. Convertible jet pumps are "convertible", meaning they can be set up to be used for either deep or shallow well applications.
4. Miniature jet pumps are used for smaller (typically commercial) applications, such as aquariums.

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