In the world of fluid energy application, the difference between hydraulics and pneumatics is often covered exhaustively. These two types of power circuits are actually similar in several ways in which both use a fluid to channel mechanical energy, as well as in executions, terminology and components.
Both systems also require a certain type of pump and some valves to control the force and speed of the actuators. The difference between pneumatics and hydraulics lies in the means used to transmit power. Tires use easily compressible gases such as air or pure gas. Meanwhile, hydraulics use relatively incompressible liquid media such as mineral oil, ethylene glycol, water, synthetic types or fluids resistant to high temperature fire to enable the transmission of energy.
Due to this main difference some other aspects about these two power circuits also follow their example. Industrial pneumatic applications use pressures ranging from 80 to 100 pounds per square inch, while hydraulics use 1,000-5,000 psi or more than 10,000 psi for specialized applications.
In addition a tank would be needed to store the oil from which the hydraulic system could extract in case of deficit. However in a pneumatic system air can simply be extracted from the atmosphere and then purified through a filter.
It can be understood in the following video: