Although there are some similarities between hydraulic systems and pneumatic fluid power systems themselves, there are some key differences in not only the way that they operate and their mechanical makeup but in their industrial applications.
In this article, we will explain, clearly and concisely how hydraulic systems work, how hydraulic fluids and pneumatic systems work and answer the question of how are hydraulic and pneumatic systems different.
Understanding the Basics
Hydraulic Systems
Hydraulic systems or hydraulic machines make use of pressurised fluid, commonly hydraulic or mineral oil, to transmit power, fluid power into mechanical energy. This is then used to power tools, powerful machinery and heavy equipment such as construction vehicles, cranes and farm machinery.
Hydraulic systems are closed systems or vacuum systems. Hydraulics rely on the closed aspect because they are pressurized systems; the fluid power comes from the pressurised system. Any hydraulic fluid leaks or contaminants including air compromise the hydraulic system functionality.
Pneumatic Systems
Pneumatic systems operate using compressed air. The pressure from the compressed air can either be converted into mechanical force or it can be used for cushioning purposes.
They do not have to be closed systems, indeed some pneumatic systems take in air, compress it, and then release it such as a bicycle pump. However, some pneumatic systems are closed systems especially those that use compressed air flow or gas such as nitrogen.
Power Transmission
Hydraulic Power Transmission
In a hydraulic system, fluid such as hydraulic oil is used to transmit power. This enables it to generate higher force.
Pneumatic Power Transmission
In a pneumatic system, compressed gas or pressurised air is used to transmit power.
System Efficiency
Hydraulic systems are generally considered to be more efficient when considering power and strength than hydraulic applications.
However, pneumatic systems and vacuum pumps are usually more efficient when considering precision and cleanliness.
Control and Precision
Hydraulic system control mechanisms
A pneumatic system, because it uses air which can be compressed, can be far more precise although it may lack the power that a hydraulic system has.
Safety and Environmental Considerations
Pneumatic systems make use of air which is compressed in an air compressor and the pressurized air is then released still as clean as it was when it entered the system. This makes pneumatic systems more environmentally friendly than hydraulic systems.
Hydraulic fluids and hydraulic pumps are typically made of mineral oil, this can be a contaminant and hazard if spilled or otherwise released into the environment and so requires proper disposal. This also makes hydraulic systems not suitable for use in, for example, food industries.
Another environmental consideration is the noise that each system creates. Hydraulic systems are noisier than pneumatic or electrical systems.
Cost and Maintenance
A full hydraulic pump system is very likely to be more costly to both install and maintain. This is because hydraulic systems are usually far more complex than pneumatic systems.
A pneumatic system is likely to require more regular maintenance however, it will still be likely to have, overall, a lower operating cost.
Conclusion
Knowing these key differences between the pneumatic actuators and hydraulic systems is essential when thinking about which would be better for your particular needs.
If power is the most important factor then a hydraulic system is likely to be a better choice.
For precision and/or cleanliness then a pneumatic system might be your preferred option.