Comparison of pneumatics to Hydraulics

Comparison of Pneumatics 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.