Hydraulics and pneumatics are branches of mechanics with important applications in various settings. They are used in different kinds of equipment in industries and commercial processes, as well as households. Hydraulic technology happens to be the more popular system, though.
What makes hydraulic systems preferable? Why is it that even wheelchair lifts that use a micro power pack and other personal equipment use this system instead of pneumatics? Learn about their differences and find out which is the superior system in the brief discussion below.
Liquid vs. gas
The main difference between hydraulic and pneumatic systems lies in the medium they use. While they both use fluids to direct mechanical energy, they vary in the type of fluid used. The former uses liquid while the latter uses gas. In case you are confused, yes, gas is also a fluid. Anything that tends to flow and takes on the shape of its container is a fluid.
Hydraulic systems use liquids such as water, ethylene glycol, mineral oil, and synthetic liquids created to be resistant to fire and extreme temperatures. These liquids are relatively incompressible. Pneumatic systems, on the other hand, make use of air, which is a compressible medium. This compressibility factor results in another difference: responsiveness or delay in reaction. Pneumatic systems have delays in movement because they still have to compress air to produce the desired movement. With hydraulics, there is almost no delay in the reaction. As the motor initiates movement, the tube in the hydraulic cylinder moves almost instantaneously.
Because of the differences mentioned above, the two systems also vary in their setup. A hydraulic system requires a tank for containing the liquid while a pneumatic setup needs a compressor. The former tends to be inherently larger than the latter because of the presence of a tank or liquid container. For pneumatic systems, containers are unnecessary as the compressor only has to draw (and filter if necessary) the air it needs from the environment.
Which is better?
The answer to this question depends on the application. For settings that need compactness, the pneumatic option is the way to go. This is why it is the mechanism used in precision drills for dentistry. Dentist chairs, nail guns, ground tampering equipment, as well as the brakes used in buses, trucks, and trains also utilise pneumatic systems. Hydraulics is the preferred mechanism in dump truck lifts, car lifts, forklifts, as well as wheelchair lifts as it is capable of exerting more force.
Since the liquid medium used in hydraulic devices is relatively incompressible, the system can handle applications requiring 1,000 to 5,000 psi of pressure (even more than 10,000 psi in industrial settings). Pneumatic instruments are only in the 80 to 100 psi range. Hence, if more force is needed, the former is the more sensible choice. However, if compactness is a primary factor to consider, it makes more sense using the latter.
Both hydraulic and pneumatic systems serve vital purposes that remain relevant at present. It cannot be said that one is better than the other unless the discussion is confined to a specific application. Neither of them is heading to obsolescence anytime soon.