Introduction to Industrial Automation

5.2   Pressurized  Air

Air has been utilized as a means of movement creation since ancient times, as can be seen from 

numerous related literature on devices and machines that were operating by utilizing pressur-

ized air. It should also be highlighted that the English term “pneumatics” originates from the 

Greek word “

πνεύμα

”, which meant “breathing” or “light blowing”, and today means “spirit”. 

Subsequently, the physical properties of air are considered well known a priori from classical phys-

ics courses, and thus no depth of analysis will be provided here.

Although it had not been utilized to a large extent in the past, pressurized air was adopted 

by industrial automations rather late in the 1960s. The real utilization of pneumatics in industry 

happened after the creation of the need to automate the largest portion of industrial operations. 

The rapid growth in this field that followed, as well as the establishment of pneumatic auto-

mations, was mainly due to the fact that there is a specific category of industrial automation 

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  Introduction to Industrial Automation

problems that can only be solved efficiently and at low cost, by the utilization of different means, 

if not pressurized air. Nowadays, there is no industrial automated production that is not utiliz-

ing pneumatic automations with pressurized air. Pressurized air has some significant advantages, 

such as:

 

◾

Air exists everywhere and in unlimited supply, and thus the cost of the raw material (air) for 

pneumatic automations is zero.

 

◾

Pressurized air can be very easily transferred through the utilization of elastic or metal-

lic pipes over long distances. Furthermore, pressurized air does not need to be returned 

to the source of its production (pressurized tank) which happens in hydraulic automa-

tion circuits.

 

◾

The compressor for generating the pressurized air does not need to be under continuous 

operation, since pressurized air can be easily stored and in large quantities.

 

◾

The variation of environmental temperature does not usually affect the operation of the 

pneumatic circuit.

 

◾

The utilization of pressurized air involves no danger of ignition or explosion, as in the case 

of utilizing an electrical actuator in an explosive environment.

 

◾

Pressurized air is a clean source of energy, since every leakage in the pipes or in the pneu-

matic devices does not create dust and dirt, a fact for example that is of paramount impor-

tance in the food, wood, medical, and high-tech industries, as in the case of integrated 

circuit production.

 

◾

Pressurized air is a very fast actuation factor. It allows for high speeds of operation 

(movement), as in the case of the pneumatic cylinders that can reach actuation speeds of 

1–2 m/s.

 

◾

Factors that influence the operation of a pneumatic automation, such as the speed and actua-

tion force, are regulating factors for the adaptation of the pneumatic system to the needs of 

an industrial application, a situation that can be easily performed in the case of pneumatics.

In general, a pneumatic automation system consists of a pressurized air production unit, a 

pneumatic circuit of pressurized air distribution, and pneumatic devices that enable the automatic 

operation of an industrial process. The first two parts, the generation and the distribution of the 

pressurized air, will not be addressed further in depth, since they do not contribute to the design 

of the overall automation scheme. More focus will be provided on the operation of different types 

of pneumatic devices, as well as on the way that these devices are controlled from an automation 

circuit.

Similar to pneumatic automations, hydraulic automations are ruled by the same philoso-

phy and principles of operation and automation, and thus will not be further analyzed here. 

However, the industrial terminology, the methods for automation, and the corresponding hydrau-

lic devices are similar to the ones in pneumatic automation, which means that an engineer with 

a very good knowledge of pneumatic automations can easily comprehend and design hydraulic 

automations as well.