Introduction to Hydraulics and Pneumatics

FLUID POWER SYSTEM
Fluid power system is power transmission system in which, the transmission of power takes place by means of “oil under pressure” or “compressed air”.
If “oil under pressure” is used in the system for power transmission, then the system is called “hydraulic system”.
If “compressed air” is used in the system for the power transmission then the system is called “pneumatic system”.

If large force and low speed is needed, then hydraulic system should be selected.
Because, oil is incompressible. Its volume will not change with increase in pressure. Pressure can be increased to any amount, nothing happens to volume of oil.
More the pressure of oil, more will be the force developed.
Hydraulic systems are slower in operation because, oil has more viscosity. Oil can not flow fast as compressed air.

If less force and higher speed is required, then pneumatic system should be selected.
As air is compressible in nature, it can not be pressurized to large amount of pressure. Since the pressure of compressed air is less (about 10 bar), force developed is also less.
Pneumatic systems are faster in operation because, air has very less viscosity. It can flow very quickly. Air rushes in to the cylinder once the valve is opened and within no time, the cylinder extends.

If compressed air is readily available in the industry, then pneumatic system is preferred.
In many industries, air compressed plant is already installed, as compressed air is needed for different processes. In such case, we can use the compressed air for operating pneumatic system.

Advantage of fluid power system:
1. Fluid power system avoids mechanical linkage (such as belts pulley, chains, sprockets, gears etc.) to a greater extent.
2. Hence, breakdowns are reduced and production will increase.
3. “design and construction” of fluid power system is easy, simple and compact, as pipes are flexible, can be bent and accommodated in the available space.
4. Automatic and safety circuits are possible, which is very important to increase rate of production and safety to avoid accidents.
5. Fluid power system are more flexible to cope-up with the design changes. Any modification in design can easily in the existing and the fluid power system.
6. Vibration and noise, wear ad ear etc. are reduced, as the mechanical linkages are replaced by the pipes.
7. If overloaded, the system stalls, the system starts working once the load is reduced.
8. Maintenance, servicing, lubrication etc. are simple and easy.


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