ABSTRACT
The key difference between hydraulic and pneumatic systems is the compressibility of the fluid (air). Accurate speed control is not possible. Pneumatic motors slow down as load increases, and the torque simultaneously increases to the point at which it just matches the load.
Desirable features of pneumatic systems are (1) they can be used over a wide temperature range, (2) they are clean, (3) high actuator speeds are possible, and (4) they can be stalled without damage. The undesirable features, besides compressibility, are (1) force is limited by operating pressure, which is typically 7 bar, and (2) the cost of compressed air is relatively high.
Pneumatic systems have a compressor, which maintains a supply of air under pressure in a receiver. Air is distributed from the receiver to the actuators, and then is exhausted to atmosphere. Flow control valves, analogous to those studied for hydraulic systems, are available.
Pneumatic power is a key component of many manufacturing operations, particularly where high cycle speeds are required. As with hydraulic power, the advantages and disadvantages must be clearly understood to achieve optimal performance
