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.
