What is Fluid Power System?
Fluid power is the technology that deals with the generation, control, and transmission of forces and movement of mechanical element or system with the use of pressurized fluids in a confined system.
Both liquids and gases are considered fluids. The fluid power system includes a hydraulic system (hydra meaning water in Greek) and a pneumatic system (pneuma meaning air in Greek).
Oil hydraulic employs pressurized liquid petroleum oils and synthetic oils, and pneumatic employs compressed air that is released to the atmosphere after performing the work.
Difference Between Hydraulic system and Pneumatic System
- Hydraulic system uses a closed-loop system and requires special attention to protect against rust and contamination. The pneumatic system uses an open-loop system and does not require special attention against contamination.
- In a hydraulic system, the working fluid is water or oil. In a pneumatic system, the working medium is air.
- Hydraulic oil is highly flammable whereas air is inflammable.
- Ideally in a hydraulic system, the fluid is relatively incompressible and hence can be used to pressurize to high pressure. In a pneumatic system, the air is readily compressible.
- Hydraulic system is bulky due to high pressure and is used for high forces and where stiffness is required. This system is used to handle higher loads and hence the motion is relatively slow. Pneumatic system is less bulky and used for lower forces and where stiffness is not required. As the system is not bulky, it can be used for faster motion.
- Hydraulic system requires high maintenance whereas pneumatic system requires less maintenance.
- A hydraulic system usually operated at very higher pressures that transmit very high power while the pneumatic system operates at low pressures near about 5-8 bar for industrial applications.
The hydraulic system and the pneumatic system difference are tabulated in the tabulated form below.
| Hydraulic System | Pneumatic System |
| A hydraulic system is a closed-loop system. | Pneumatic System is an open-loop system. |
| It is robust in construction and maintenance cost is high. | It is simple in construction and maintenance cost is less. |
| The working fluid is hydraulic oil. | The working fluid is air. |
| As oil is incompressible, it can be pressurized to very high pressure. | Air is compressible and hence air can be pressurized to lesser pressure. |
| The system is bulky due to high pressure. | The system is less bulky as compared to a hydraulic system. |
| The accuracy of the system is high. | The accuracy of the system is not high. |
| Hydraulic oil is flammable. | Air is inflammable. |
| To protect against rust, the system needs special attention. | This system does not require any special attention. |
| Contamination control is required in this system. | Contamination control is not required in this system. |
| The power to size ratio is more. | The power to size ratio is small. |
Applications of Hydraulic System
- Hydraulic systems are widely used in automation industries.
- In the automobile industry, hydraulic system is used in power brakes, power steering, suspension system, etc.
- The missile launching system makes use of the hydraulic system.
- The agricultural sector makes heavy use of the hydraulic system. It is used in farm equipment like movers, plows, chemical and water sprayers, harvesters, etc.
- One of the most popular examples of hydraulic systems is jacks, hoists, cranes, forklifts in material handling systems.
- It is also used in transportation systems such as hydraulic elevators, winches, overhead trams.
Applications of Pneumatic System
- Instruments used in the fabrication industry such as pneumatic drills, grinders, borers, riveting machines, nut runners, etc run on a pneumatic system.
- Vacuum suction cups are used for glass handling.
- Work holding devices, clamps, stoppers make use of a pneumatic system.
- It is also used in automated machine tools, numerically controlled (NC) machine tools.
- Pharmaceutical, as well as the medical industry, makes wide use of pneumatic systems.
- The robotic industry makes wide use of pneumatic systems.
