There is no record of manís first uses of air to do work. One of
the first pneumatic devices was the blow gun used by primitive man. In the
latter part of the eighteenth century, heated air was used to carry the
first balloon aloft. The heated air, being lighter than the surrounding air,
caused the balloon to rise. Every age of man has witnessed the
development of devices which used air to do work. However, man used air to
do work long before he understood it. The development of pneumatics depended
on closely fitted parts and the development of gaskets and packings. Since
the invention of the air compressor, pneumatics has become a very reliable
way to transmit power. Probably one of the most common uses of
pneumatic power is in the operation of pneumatic tools. However, you should
understand that pneumatics is also of great importance in large and complex
systems as well.
While having a knowledge of system components is essential, it is difficult
to understand the interrelationship of these components by simply watching
the system operate. The knowledge of system interrelation is required to
effectively troubleshoot and maintain a pneumatic system. Diagrams or
drawings are a valuable aid in understanding the operation of the system and
in diagnosing the causes of malfunctions. To troubleshoot pneumatic systems
intelligently, a technician must be familiar with the system on which he or
she is working. The technologist must know the function of each component in
the system and have a mental picture of its location in relation to other
components. This can best be done by studying the diagrams of the system.
A diagram may be defined as a graphic representation of an assembly or
system that indicates the various parts and expresses the methods or
principles of operations. The ability to read diagrams is a basic
requirement for understanding the operation of pneumatic systems.
Understanding the diagrams of a system requires having a knowledge of the
symbols used in the schematic diagrams.
Some of the symbols frequently used in fluid power systems are available for
review by clicking on this pneumatics
and hydraulic symbols link. Some rules applicable to
graphical symbols for pneumatic and hydraulic diagrams are as
1. Symbols show connections, flow
paths, and the function of the component represented only. They do not
indicate conditions occurring during transition from one flow path to
another; nor do they indicate component construction or values, such as
pressure or flow rate.
2. Symbols do not indicate the
location of ports, direction of shifting of spools, or position of control
elements on actual components.
3. Symbols may be rotated or reversed
without altering their meaning except in cases of lines to reservoirs and
4. Symbols may be drawn in any size.
5. Each symbol is drawn to show the normal
or neutral condition of each component unless multiple circuit diagrams are
furnished showing various
phases of circuit operation.
Pictorial diagrams show the
general location and actual appearance of each component, all
interconnecting piping, and the general piping arrangement. This type of
diagram is sometimes referred to as an installation diagram. Diagrams of
this type are invaluable to maintenance personnel in identifying and
locating components of a