Difference Between Hydraulic and Pneumatic

Hydraulic vs Pneumatic

In engineering and other applied sciences, fluids play a major role in designing and building useful systems and machinery. The study of fluids allows applications in engineering in various designs and constructions, ranging from a design and construction of a reservoir and irrigation system to medical equipment. Hydraulics focus on the mechanical properties of liquids and the pneumatic focuses on the mechanical properties of gases.

More about Hydraulic

Hydraulic mainly works as the foundation for fluid power; that is, generation and transmission of power using liquids. Pressurized liquids are used in transmission of mechanical power from the power generating component to power consuming component. As the working fluid, a liquid with low compressibility is used, such as oil (ex. Brake fluid or transmission fluid in a vehicle). Due to incompressibility of the fluids, hydraulic based equipment can operate on very high loads, delivering more power. The system based on hydraulics can operate from low pressure to very high pressure levels in the range of mega Pascal. Therefore, many heavy duty systems are engineered to work on hydraulics, such as mining equipment.

Hydraulic systems offer high reliability and precision as a result of their low compressibility. A compressed liquid responds to even a minute change in the input power. Supplied energy is not absorbed significantly by the fluid, resulting in higher efficiency.

Due to higher loads and pressure conditions, the strength of the hydraulic system components is also designed to be higher. As a result, hydraulics equipment tends to be larger in size with a complex design. High load operating conditions wear the moving parts rapidly, and maintenance costs are higher. A pump is used for pressurizing the working fluid, and the transmission tubes and mechanisms are sealed to withstand high pressure and any leakage leaves visible marks and may cause damage to external components.

More about Pneumatic

Pneumatic focuses on the application of pressurized gases in engineering. Gases can be used to transmit power in mechanical systems, but the high compressibility limits the maximum operating pressure and loads. Air or inert gases are used as the working fluid, and the maximum operating condition pressures in pneumatics systems are in the range of several hundred kilo Pascal (~ 100 kPa).

Reliability and precision of the pneumatic systems tend to be lower (especially at high pressure conditions) though the equipment has a higher lifetime and maintaining costs are low. Because of the compressibility, pneumatic absorbs the input power and efficiency is lower. However, to a sudden change in input power, gases absorb the excess forces and the system becomes stable, avoiding damage to the system. Therefore, overload protection is integrated, and systems are safer. Any leakage in the system leaves no traces, and the gases are released to the atmosphere; physical damages due to leakage are low. A compressor is used for pressurizing the gases, and the pressurized gas can be stored, allowing the device to work on cycles rather than on continuous power input.

What is the difference between the Hydraulic and Pneumatic?

  • The working fluid in hydraulics is a liquid, whereas the working fluid of the pneumatic is a gas.
  • Hydraulics can operate on higher loads and pressure (~ 10 MPa), while pneumatic operates on much lower load and pressure (~ 100 kPa).
  • Hydraulic equipment tends to be larger in size while, pneumatic equipment tends to be smaller (the difference is based on the application).
  • Hydraulic system has higher efficiency than pneumatic in terms of transmission.
  • Hydraulic systems use pumps to pressurize the working fluid, while pneumatic systems use compressors.