The difference between hydraulics and pneumatics is the medium used in each system to perform work. Hydraulics employ fluids, such as oils, while pneumatics utilize compressed gases, such as carbon dioxide or atmospheric air.
Hydraulics and pneumatics differ in several ways, but the most notable is the fact that each system uses a different medium. Both systems have their own distinct advantages and ideal applications, such as heavy lifting and operating costs. Hydraulics are most often used for larger and heavier applications, such as mining, construction and industrial machining. Using the fact that hydraulic fluids do not compress, rams, pistons, brakes and cylinders employing hydraulics can exert tremendous forces, though there are some limitations. Hydraulics do not compress and, therefore, have no spring action to protect equipment against overloads and are typically twice as expensive as pneumatic systems.
Conversely, pneumatic systems are cheaper and easier to use and maintain than hydraulics, in addition to being cleaner; a leak in a pneumatic system is vented into the atmosphere, as opposed to spraying high-pressure oil on and around the equipment. However, these systems have their own restrictions. While the gas system provides a cushion for overloads, increasing the useful life of the equipment, the applications of these systems are somewhat limited. Typical pneumatic systems operate at around 80 to 100 pounds per square inch of pressure, with pressures greater than this restricted by the materials used within the system. Some of the most common applications of pneumatic technology are jackhammers, dentistry equipment, air brakes and air-compressors.