Pneumatics vs Hydraulics

Both pneumatics and hydraulics are applications of fluid power.

Pneumatics uses an easily compressible gas such as air or a suitable gas, while hydraulics cannot compress liquid such as oil or hydraulic fluid. Most industrial pneumatic applications use pressures of about 80 to 100 pounds per square inch (psi) (500 to 700 kPa/0.7 Pa). PSI is another measure of force to area. Hydraulic 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
· Design and Control Simplicity

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o Machines are easily designed using cylinders & other equipment. Control is as easy as it is simple: ON and OFF switch type controls.

· Being Reliable

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o Pneumatic systems have long operation lives and need very little maintenance.
o 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 transfers force.

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Storage
o Compressed Gas can be stored, allowing the use of machines when electrical power is lost. Ex. Propane gas for a barbecue.

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Safety
o Capable of small fire hazards (compared to hydraulic oil).
o Machines can be designed to be overload safe.

Advantages of Hydraulics

* Fluid does not absorb any of the supplied energy, it transfers the energy.

* Capable of moving much higher loads and providing much higher forces due to the incompressible factor.

* 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.

source Science Ray