Pneumatics (from Greek ‘wind, breath’) is a branch of

engineering Engineering is the use of scientific method, scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehicles, and buildings. The discipline of engineering encompasses a broad rang ...

that makes use of gas or pressurized air. Pneumatic systems used in industry are commonly powered by compressed air or compressed inert gases. A centrally located and electrically-powered compressor powers

cylinders A cylinder (from ) has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base. A cylinder may also be defined as an infini ...

, air motors, pneumatic actuators, and other pneumatic devices. A pneumatic system controlled through manual or automatic solenoid valves is selected when it provides a lower cost, more flexible, or safer alternative to

electric motor An electric motor is an electrical machine that converts electrical energy into mechanical energy. Most electric motors operate through the interaction between the motor's magnetic field and electric current in a wire winding to generate forc ...

s, and hydraulic actuators. Pneumatics also has applications in

dentistry Dentistry, also known as dental medicine and oral medicine, is the branch of medicine focused on the teeth, gums, and mouth. It consists of the study, diagnosis, prevention, management, and treatment of diseases, disorders, and conditions ...

construction Construction is a general term meaning the art and science to form objects, systems, or organizations,"Construction" def. 1.a. 1.b. and 1.c. ''Oxford English Dictionary'' Second Edition on CD-ROM (v. 4.0) Oxford University Press 2009 and ...

mining Mining is the extraction of valuable minerals or other geological materials from the Earth, usually from an ore body, lode, vein, seam, reef, or placer deposit. The exploitation of these deposits for raw material is based on the economic ...

, and other areas.

Gases used in pneumatic systems

A solenoid actuated pneumatic butterfly valve

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 is added at the compressor to prevent corrosion and lubricate mechanical components. Factory-plumbed pneumatic-power users need not worry about poisonous leakage, as the gas is usually just air. Any compressed gas other than air is an asphyxiation hazard—including nitrogen, which makes up 78% of air. Compressed

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as we ...

(approx. 21% of air) would not asphyxiate, but is not used in pneumatically-powered devices because it is a fire hazard, more expensive, and offers no performance advantage over air. Smaller or stand-alone systems can use other compressed gases that present an asphyxiation hazard, such as nitrogen—often referred to as OFN (oxygen-free nitrogen) when supplied in cylinders. Portable pneumatic tools and small vehicles, such as Robot Wars machines and other hobbyist applications are often powered by compressed

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is t ...

, 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 requires. Carbon dioxide is an asphyxiant and can be a freezing hazard if vented improperly.

History

The origins of pneumatics can be traced back to the first century when ancient Greek mathematician Hero of Alexandria wrote about his inventions powered by steam or the wind. German physicist Otto von Guericke (1602 to 1686) further developed the idea. He invented the vacuum pump, a device that can draw out air or gas from the attached vessel. He demonstrated the vacuum pump to separate the pairs of copper hemispheres using air pressures. The field of pneumatics has changed considerably over the years. It has moved from small handheld devices to large machines with multiple parts that serve different functions.

Comparison to hydraulics

Both pneumatics and

hydraulics Hydraulics (from Greek: Υδραυλική) is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid coun ...

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 . Hydraulics applications commonly use from , but specialized applications may exceed .

Advantages of pneumatics

*''Simplicity of design and control''—Machines are easily designed using standard cylinders and other components, and operate via simple on-off control. *''Reliability''—Pneumatic systems generally have long operating lives and require little maintenance. Because gas is compressible, equipment is less subject to shock damage. Gas absorbs excessive force, whereas fluid in hydraulics directly transfers force. Compressed gas can be stored, so machines still run for a while if electrical power is lost. *''Safety''—There is a very low chance of fire compared to hydraulic oil. New machines are usually overload safe to a certain limit.

Advantages of hydraulics

* Fluid does not absorb any of the supplied energy. * Capable of moving much higher loads and providing much lower forces due to the incompressibility. * The hydraulic working fluid is practically compressible, 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" pressurized air to release the pressure on the load. * Highly responsive compared to pneumatics. * Supply more power than pneumatics. * Can also do many purposes at one time: lubrication, cooling and power transmission.

Pneumatic logic

Pneumatic logic systems (sometimes called air logic control) are sometimes used for controlling industrial processes, consisting of primary logic units like: * And units * Or units *Relay or booster units *Latching units *Timer units * Fluidics amplifiers with no moving parts other than the air itself Pneumatic logic is a reliable and functional control method for industrial processes. In recent years, these systems have largely been replaced by electronic control systems in new installations because of the smaller size, lower cost, greater precision, and more powerful features of digital controls. Pneumatic devices are still used where upgrade cost, or safety factors dominate.

Examples of pneumatic systems and components

* Air brakes on

bus A bus (contracted from omnibus, with variants multibus, motorbus, autobus, etc.) is a road vehicle that carries significantly more passengers than an average car or van. It is most commonly used in public transport, but is also in use for cha ...

es and

truck A truck or lorry is a motor vehicle designed to transport cargo, carry specialized payloads, or perform other utilitarian work. Trucks vary greatly in size, power, and configuration, but the vast majority feature body-on-frame constructi ...

s * Air brakes on trains * Air compressors * Air engines for pneumatically powered vehicles * Barostat systems used in neurogastroenterology and for researching electricity * Cable jetting, a way to install cables in ducts * Dental drill * Compressed-air engine and compressed-air vehicles * Gas Chromatography *

Gas-operated reloading Gas-operation is a system of operation used to provide energy to operate locked breech, autoloading firearms. In gas-operation, a portion of high-pressure gas from the cartridge being fired is used to power a mechanism to dispose of the spen ...

* Holman Projector, a pneumatic anti-aircraft weapon * HVAC control systems * Inflatable structures *

Lego pneumatics Lego pneumatics is a variety of Lego bricks which use air pressure and specialised components to perform various actions using the principles of pneumatics. History The LEGO pneumatics components were first introduced as part of the LEGO Techn ...

can be used to build pneumatic models * Pipe organ ** Electro-pneumatic action ** Tubular-pneumatic action * Player piano * Pneumatic actuator * Pneumatic air guns * Pneumatic bladder * Pneumatic cylinder * Pneumatic launchers, a type of spud gun * Pneumatic mail systems *

Pneumatic motor A pneumatic motor (air motor), or compressed air engine, is a type of motor which does mechanical work by expanding compressed air. Pneumatic motors generally convert the compressed air energy to mechanical work through either linear or rotar ...

* Pneumatic tire * Pneumatic tools: ** Jackhammer used by road workers ** Pneumatic nailgun * Pressure regulator * Pressure sensor *

Pressure switch A pressure switch is a form of switch that operates an electrical contact when a certain set fluid pressure has been reached on its input. The switch may be designed to make contact either on pressure rise or on pressure fall. Pressure switches ...

* Launched roller coaster * Vacuum pump * Vacuum sewer

Notes

References

* Brian S. Elliott, ''Compressed Air Operations Manual'', McGraw Hill Book Company, 2006, . * Heeresh Mistry, ''Fundamentals of Pneumatic Engineering'', Create Space e-Publication, 2013, .

External links

Four Ways to Boost Pneumatic Efficiency
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