Pneumatics

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Table of Pneumaticks, 1728 Cyclopaedia


Pneumatics (from the Greek πνευματικός pneumatikos, coming from the wind) is the use of pressurized gas to do work in science and technology.

Pneumatics was first documented by Hero of Alexandria in 60 A.D., though the subject had been known before then.

Application

Pneumatics is employed in a variety of settings. In dentistry applications, pneumatic drills are lighter, faster, and simpler than an electric drill of the same power rating (because the prime mover, the compressor, is separate from the drill and pumped air is capable of rotating the drill bit at extremely high rpm). Pneumatic transfer systems are employed in many industries to move powders and devices. Pneumatic tubes can carry objects over distances. Pneumatic devices are also used where electric motors cannot be used for safety reasons, such as deep in a mine where explosive dust or gases may be present.

Examples of pneumatic tools:

electricity

Comparison to Hydraulics

Both pneumatics and hydraulics are applications of fluid power. Pneumatics uses air, which is compressible, while hydraulics uses relatively incompressible liquid media such as oil or water. Most industrial pneumatic applications use pressures of about 80 to 100 pounds per square inch (psi) (500 to 700 kilopascals). Hydraulics applications commonly use from 1,000 to 5,000 psi (7 to 35 MPa), but specialized applications may exceed 10,000 psi (70 MPa).

Advantages of pneumatics

  • The working fluid is very light in weight so supply hoses are not heavy.
  • Because the working fluid is (mostly) just air, there is usually no need for a return line for the working fluid and leaks of the working fluid tend not to be messy.
  • Because air is compressable, the equipment is less likely to be damaged by shock. The air in pneumatics absorbs excessive force, whereas the fluid of hydraulics directly transfers force.

Advantages of hydraulics

  • Higher energy density owing to the much higher working pressures usually employed.
  • The hydraulic working fluid is basically incompressible, leading to a minimum of spring action. When hydraulic fluid flow is stopped, the slightest motion of the load releases the pressure on the load; there is no need to "bleed off" pressurised air to release the pressure on the load.

Pneumatic Components

Common industrial pneumatic components include:

Pneumatic Logic

Pneumatic logic systems are often used to control industrial processes, consisting of primary logic units such as:

  • And Units
  • Or Units
  • 'Relay or Booster' Units
  • Latching Units
  • 'Timer' Units

Pneumatic logic is a reliable and functional control method for industrial processes. In recent years, these systems have largely been replaced by electrical control systems, due to the smaller size and lower cost of electrical components. Pneumatic devices are still used in processes where compressed air is the only energy source available or upgrade cost, safety, and other considerations outweigh the advantage of modern digital control.

External links

See also

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