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Pneumatics is the use of pressurized gas to affect mechanical motion.
Pneumatic power is used in industry, where it is common to have factory units plumbed for compressed air although other compressed inert gases can be, and are used in smaller or self-contained systems. It also has applications in, among others, dentistry, construction, and mining.
Examples of pneumatic systems
- Pneumatic tools:
- Pneumatic drill (jackhammer) used by road workers
- Pneumatic nailgun
- Pneumatic switches
- Pneumatic actuator
- Air compressors
- Vacuum pump
- Barostat systems used in Neurogastroenterology and for researching electricity
- Cable Jetting, a way to install cables in ducts
- Pneumatic mail systems
- Air brakes on buses and trucks
- Air brakes, on trains
- Air engines for pneumatically powered vehicles
- Lego pneumatics can be used to build pneumatic models
- Pneumatic Launchers, a type of spud gun
- Pneumatic air guns
- Holman Projector, a pneumatic anti-aircraft weapon
Gases used in pneumatic systems
Pneumatic systems in fixed installations such as factories use compressed air because a sustainable supply can be made by compressing atmospheric air. The air usually has moisture removed and a small quantity of oil added at the compressor, to avoid corrosion of mechanical components and to lubricate them.
Factory-plumbed, pneumatic-power users need not worry about poisonous leakages as the gas is commonly just air. Smaller or stand-alone systems can use other compressed gases which are an asphyxiation hazard, such as nitrogen - often referred to as OFN (oxygen-free nitrogen), when supplied in cylinders.
Any compressed gas other than air is an asphyxiation hazard - including nitrogen, which makes up approximately 80% of air. Compressed oxygen (approx. 20% of air) would not asphyxiate, but it would be an extreme fire hazard, so is never used in pneumatically powered devices.
Portable pneumatic tools and small vehicles such as Robot Wars machines and other hobbyist applications are often powered by compressed carbon dioxide because containers designed to hold it such as soda stream canisters and fire extinguishers are readily available, and the phase change between liquid and gas makes it possible to obtain a larger volume of compressed gas from a lighter container than compressed air would allow. Carbon dioxide is both an asphyxiant and poisonous, and can also be a freezing hazard when vented.
Comparison to hydraulics
Both pneumatics and hydraulics are applications of fluid power. Pneumatics uses an easily compressible gas such as air or a suitable pure gas, while hydraulics uses relatively incompressible liquid media such as oil. 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
- Cleanliness
- Air is used by a machine and is then exhausted to the atmosphere - no return line is necessary.
- Any leaks will be of air (which is much less of a problem than oil leaks in Hydraulics).
- Availability
- Air is freely available in the pneumatics.
- Most factories are pre-plumbed for compressed air distribution - which makes it very easy to set up a manufacturing process.
- Simplicity of Design And Control
- Machines are easily designed using standard cylinders & other components. Control is as easy as it is simple ON - OFF type control.
- Reliability
- Pneumatic systems tend to have long operating lives and require very little maintenance.
- Because gas is compressible, the equipment is less likely to be damaged by shock. The gas in pneumatics absorbs excessive force, whereas the fluid of hydraulics directly transfers force.
- Storage
- Compressed Gas can be stored, allowing the use of machines when electrical power is lost.
- Safety
- Very small fire hazards (compared to hydraulic oil).
- Machines can be designed to be overload safe.
Advantages of hydraulics
- Fluid does not absorb any of the supplied energy.
- Capable of moving much higher loads and providing much higher forces due to the incompressibility.
- 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 Logic
Pneumatic logic systems are often used to control industrial processes, consisting of primary logic units such as:
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.
See also
External links
- www.pneumatics.be - didactic website - for students - how pneumatics works
- U.S. Department of Energy - Improving compressed-air system performance
- Fluid Power Educational Foundation - Advancing and supporting hydraulic and pneumatic education
Wikipedia content modification information:
- This page was last modified on 28 November 2008, at 23:58.
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