Blaise Pascal first discovered the physical behavior of a fluid like air and water. Pascal found that when a force was applied to the end of a container of liquid, the force was transmitted equally in all directions.  Pascal also discovered that pressure is equal to force divided by the area on which it acts or the formula:

Force = Pressure x Area 

    In pneumatics, force is produced by air pressure acting on the surface of a piston or valve. A force of 100 kPa is known as 1 bar.  Normal atmospheric pressure ( the force exerted on a square meter of land at sea level by a square meter column of air rising from sea level to the outer atmosphere) is approx 101.3 kPa (1.013 bar). 

   A technologist must know the function of each component in a pneumatic system, and they must also have a good 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.

    Compressors come in many shapes and sizes, but they all work on the same principle.  Compressed air is produced in a compressor and stored in the receiver.  Air is pumped through a check valve into the lower metal  tank called the receiver.  When the air inside the receiver reaches the required pressure, a pressure regulating switch turns off the pump.  

    Pressure control valves control the amount of power produced by the cylinders, which converts the potential energy of the compressed air into kinetic energy at the device.  Pneumatic control valves direct the air flow, while flow control valves regulate the speed of the air. 

    The single action spring return cylinder extents when air pressure is applied to the diameter area of the cylinder.  The cylinder will stay extended until the pressure is relieved, and the spring returns the cylinder rod to the normal position. 

    The Force must be higher than the spring return pressure and any load it is requires to move.  If the Area is 3.14 square inches (diameter of the cylinder is 2 inches so a 1 inch radius squared times 3.14 or Pi) and the Pressure is 100 pounds per square inch then the following calculation will give you the force.

    1 X 3.14 X 100 pounds per square inch = 314 pounds of force. 

    The spring requires 50 pounds of force.

    314 - 50 = 264 pounds.  The cylinder without friction would  be able to lift  264 pounds of load.

   Valves control the switching and routing of the air in a pneumatic system.  While reviewing the operation of cylinders, you may have already discovered that valves not only have to control the flow of compressed air, but they also have to control the flow of the exhausted air to the atmosphere. There are many types of valves used in pneumatic switching circuits.   We will discuss just two types:

   The 3/2 valve is used to control a single acting spring return cylinders which has a single input of air. The input air going to the single acting spring return cylinder is connected to port 2.  When 3/2 valve is pushed, the air supply will flow from port 1 through the valve and on to port 2 to extend the cylinder.  When the push lever is returned, the 3/2 valve will shift back and the single acting spring return cylinder will retract, exhausting the air to the atmosphere through port 3.
    The number 3 signifies that the valve has three ports, while the number 2 signifies that the valve has 2 directions or states.  (Example Below)

 The 5/2 valve is used to control a double acting return cylinders which has a double input of air. The input air going to the double acting cylinder is connected to port 2.  When the 5/2 valve is pushed, the air supply will flow from port 1 through the valve and on to port 2 to extend the cylinder.  When the push lever is returned, the 5/2 valve will shift back allowing air from port 1 to flow through the valve and out of port 4 to the cylinder, and the double acting cylinder will retract, exhausting the air to the atmosphere through port 3.
    The number 5 signifies that the valve has five ports, while the number 2 signifies that the valve has 2 directions or states.  (Example Below)