Nepedia
Back to Discover
Advanced Reader
💻

Pump

technology Maturity 7-9 Next article →

A pump is a mechanical device designed to move fluids. Fluids include both liquids and gases. Some pumps even move slurries, which are mixtures of solids and liquids. Most pumps work by converting electrical energy into hydraulic or pneumatic energy. Hydraulic energy relates to liquids, while pneumatic energy relates to gases. Pumps are essential in many industries. They pull water from wells and filter water in aquariums. In the car industry, they manage fuel injection and engine cooling. The energy industry uses them to move oil and natural gas. In medicine, pumps assist in manufacturing drugs or act as artificial body parts, such as an artificial heart.

Jet pump
Jet pump

Mechanical pumps can be placed inside the fluid they move or outside of it. Engineers classify them by how they move the fluid. There are three basic types: positive-displacement, centrifugal, and axial-flow pumps. In a centrifugal pump, the fluid's direction changes by ninety degrees as it passes over an impeller. An impeller is a rotating part that moves the fluid. In axial-flow pumps, the direction of the fluid flow remains unchanged. To ensure reliability, many centrifugal pumps follow global engineering standards like ISO 2858 or API 610. These rules define how parts are built and how they must perform.

Centrifugal 2
Centrifugal 2

Positive-displacement pumps work by trapping a fixed volume of fluid. They then force that volume into a discharge pipe. This process often uses an expanding cavity on the suction side to pull liquid in. As the cavity collapses on the discharge side, the liquid is pushed out. Because the volume remains constant during each cycle, these are called constant flow machines. However, a slight increase in internal leakage can occur as pressure rises. This prevents the flow from being perfectly constant.

Gear pump
Gear pump

Safety is critical when using positive-displacement pumps. Unlike centrifugal pumps, they do not have a "shutoff head." This means they can keep pushing fluid even if a valve is closed. If a discharge valve is closed, pressure will build up. This can cause the discharge line to burst or the pump to break. To prevent this, engineers install a relief or safety valve. An external relief valve can return fluid back to a supply tank.

LobePump en
LobePump en

Positive-displacement pumps are divided into several sub-types. Rotary-type pumps use a rotating mechanism to create a vacuum. This vacuum draws the liquid into the pump. Gear pumps are a simple version using two meshed gears to push liquid. Screw pumps use two or three screws with opposing threads to drive the fluid.

Lysholm screw rotors
Lysholm screw rotors

Peristaltic pumps use rollers to pinch flexible tubing. This forces the liquid forward. Because they are easy to clean, they are popular for dispensing food and medicine.

eccentric pump
eccentric pump

Another category is reciprocating positive-displacement pumps. These use parts that move back and forth, such as pistons, plungers, or diaphragms. To create suction, the pump pulls a plunger outward to decrease chamber pressure. When the plunger moves back in, it increases the pressure. This opens a discharge valve to release the fluid. These pumps can be simplex, with one cylinder, or more complex, like quad-cylinder models. In the 19th century, they were used heavily as boiler feed water pumps for steam engines.

Hand pump-en
Hand pump-en

Specific designs serve specialized needs. A progressing cavity pump uses a helical rotor inside a rubber stator. These can create high pressure, reaching 90 PSI per stage on water. Diaphragm pumps use a flexible membrane to move hazardous or toxic fluids safely. Some small devices, like hand soap dispensers, are also piston displacement pumps. Even low-cost espresso machines use vibratory pumps. These use a spring-loaded piston driven by alternating current. However, they are limited to intermittent use because they can overheat in about one minute.

Progressive cavity pump animation
Progressive cavity pump animation

Finally, the study of pumps connects to the natural world. In biology, many chemical and biomechanical pumps have evolved in living things. Scientists sometimes use biomimicry to develop new mechanical pumps. Biomimicry is the practice of looking at nature to solve human engineering problems. By studying how biological pumps work, engineers can create more efficient machines for the future.

680 words

Where will your curiosity go next?

Keep exploring at your chosen reading level.

🖼️ Images & Media (23)
File:Jet pump.jpg
Jet pump.jpg
File:Wasserwerk pumpe01.jpg
Wasserwerk pumpe01.jpg
File:LobePump en.svg
LobePump en.svg
File:LobePump3DAnimationArrows.gif
LobePump3DAnimationArrows.gif
File:Pompe à palettes.gif
Pompe à palettes.gif
File:Hand pump-en.svg
Hand pump-en.svg
File:Old hand water pump.jpg
Old hand water pump.jpg
File:Gear pump.svg
Gear pump.svg
File:Lysholm screw rotors.jpg
Lysholm screw rotors.jpg
File:Progressive_cavity_pump_animation.gif
Progressive_cavity_pump_animation.gif
File:lobbenpomp.gif
lobbenpomp.gif
File:eccentric pump.gif
eccentric pump.gif

+ 11 more

More to explore

🔬 Go deeper

More advanced topics to explore

🪜 Step back

Simpler topics to build understanding

What is Nepedia?

A free, ad-free encyclopedia for children. Every article is written at five reading levels, so the same page works for a five-year-old and a fifteen-year-old — use the level switcher above to see this one change. No account needed to read.