pneumatics and pneumatic systems

PNEUMATICS AND PNEUMATIC SYSTEMS

1. What does the term 'Pneumatics' refer?

• The term 'pneumatics' has been derived from the Greek word ‘pneuma', which means air, wind, or breath.

• Definition: The pneumatics may be defined as that branch of engineering-science which deals with the study of the behaviour and application of compressed air.

• Like hydraulics, pneumatics is a branch of the fluid power technology. Thus the pneumatics is the technology that deals with the generation, control, and transmission of power using pressurised air.

2. Pneumatic Systems

• Pneumatic system is the one that uses a pressurized gas to transmit and control power. 

• However, almost all pneumatic systems prefer to use air rather than some other gas as their fluid medium.

• The compressed air is popularly used as the fluid medium in pneumatic systems due to the following reasons:

(i) Air is abundantly available.

(ii) It is safe to use (as it has the fire-proof characteristics).

(iii) It is very cheaper in cost.

(iv) Easier maintenance and easy handling.

(v) It can be exhausted easily to the atmosphere after use.

Note 

We have already presented the basic components, layout, advantages, disadvantages and applications of a pneumatic system in section 1.8, in Chapter 1. For continuity and better readability, some of those topics have been presented again.

3. Advantages of Pneumatic Systems Over Hydraulic Systems

(What are the reasons for considering the use of Pneumatic Systems instead of Hydraulic Systems ?)

In many applications, the pneumatic systems are preferred over the hydraulic systems, due to the following reasons :

1. Since the weight density of gas is many times lesser than liquid, therefore inertia effect of pneumatic components are lesser than hydraulic system components. Thus the force required to accelerate gas (air) is much lesser than that required to accelerate an equal volume of oil.

2. Since viscosity of air is much lesser than that of oil, therefore the pneumatic systems experience lesser frictional pressure and power losses than the hydraulic systems.

3. Unlike in hydraulic systems, pneumatic systems can exhaust its fluid medium (air) to the atmosphere after completing its assigned task. This reduces the requirements of special designs for reservoirs and leak-proof systems.

4. Pneumatic systems are comparatively cheaper in cost than the hydraulic systems.

5. Pneumatic systems provide better operational advantages when compared to hydraulic systems.

6. Compared to hydraulic systems, pneumatic systems are lesser in weight.

7. Unlike in hydraulic systems, leakage of air in pneumatic systems will not affect the system performance very much (because the air compressor supplies the pressurised air continuously).

4. Disadvantages of Pneumatic Systems

The main disadvantages of pneumatic systems are given below:

1. Due to the high compressibility of air, pneumatic systems cannot provide precise actuator control and precise positioning control.

2. Due to compressor design limitations, pneumatic systems can be applied only to low- pressure (less than 17 bars) applications; whereas hydraulic systems can be applied to high-pressure (upto 700 bars) applications.

5. Applications of Pneumatic Systems

Like hydraulic systems, the application of pneumatic systems can be found in almost all industries/fields. However some of the industrial applications are listed below:

1. Stamping,

2. Drilling,

3. Hoisting,

4. Punching,

5. Assembling,

6. Clamping,

7. Riveting,

8. Materials handling,

9. Logic controlling, and

10. Hammering.

6. Selection of Hydraulic and Pneumatic Systems

(Choice of Working Medium and System).

For a given application, there is no hard and fast rule to follow to decide which of the system should be used. However, the following guidelines may be followed for the selection :

1. If the application requires a very high pressure or an extremely accurate feed, then an oil hydraulic system can be used.

2. If the application requires speed, a medium amount of pressure, and only a fairly accurate feed, then an air pneumatic system can be used.

3. If the application requires only a medium amount of pressure and a feed of greater accuracy, then a combination of air and hydraulic systems can be used.