@jauhar123 | Posted 14 Jun. 2019
Hydraulic fluid is not compressible, so it is safer and much more controllable than pneumatics (at the same power levels ). For example, if a 3,000 psi hydraulic tank burst, it would release a small amount of fluid to bring the tank pressure down it 0 psi. Conversely, breaking the valve off the end of a 3,000 psi inert gas (pneumatic) tank has resulted in the tank shooting through multiple cement walls, destroying everything in its path.
Pneumatics are used in situations where high pressures are not required or where contamination is not acceptable. For example, pressurized industrial control systems typically use low pressure (~ 100 psi) oil-free compressed air because it is clean and will not gunk up control system components; also slow leaks are not harmful to the environment.
Hydraulic systems are stiffer, have higher power density, cost more and because of the first 2 have become key in many high performance industrial systems which in turn has made a market driving high quality reliable hardware. Festo Pneumatics are great for lighter factory automation where the compliance of actuators operated by air does not present a problem.