As the most powerful media to distribute signals and power, fluid, either in liquid or gas form, has many uses in industry. Liquids and gases basically can be distinguished by the relative likelihood pemampatannya and the fact that the fluid may have a surface that is free, is being enlarged gas meets his place. In the field of engineering, the term describes pneumatic fluid systems that use air or gas, and hydraulics applies to systems that use a lubricant or oil.
Pneumatic systems are used extensively in otomatisasimesin-production machine and the source of the automatic controller. For example, a pneumatic circuit that converts compressed air energy into mechanical energy is used widely, and various types of pneumatic controllers found in the industry. Because the system of pneumatic and hydraulic systems are often compared to each other, then the following we will provide a comparison between the two systems in short, between the two systems.
The differences are as follows:
1. Air and gas compressible medium oil can not be compressed.
2. Air shortage of lubricating properties and always contains water vapor. The function of the oil is as fluid hydraulics and lubricants.
3. The normal operating pressure pneummatika system is much lower than sistent hydraulics.
4. The output power pneumatic system is much smaller than the hydraulics system.
5. Accuracy of pneumatic actuators is worse at low speeds, while the precision of hydraulic actuators can be made to satisfy all conditions of speed.
6. In the pneumatic system external leakage is allowed up to a certain level, but internal leakage must be avoided because effective pressure difference agakkecil. In the hydraulics system, internal leaks diperbolehkansampai certain level, external tetapikebocoran harusdihindarkan.
7. Not required pipe back on the system when used pneumatic air, while return pipe is always needed by the hydraulics system.
8. The pneumatic system’s normal operating temperature is 5 ° to 60 ° C (41 ° to 140 ° Fahrenheit). But the pneumatic system can operate at temperatures of 0 ° to 200 ° C (32 ° to 392 ° F). Pneumatic system is not sensitive to changes in temperature, tetapisebaliknva with the hydraulics system, the fluid friction caused by the immense speed depends on the temperature. Normal operating temperature for the system hydraulics is 20 ° to 70 ° C (68 ° to 158 ° F).
9. The pneumatic system is fireproof and explosion, hydraulics systems were not so.
Figure 2.19 (a) Pneumatic Temperature Control System
Figure 2.19 (b) Hydraulic Control System (Engine Speed Control)