1-1 Attributes of pneumatics:

There are many similarities between the ways in which pneumatic and hydraulic are used, and similar symbols are used as those of circuit which show the movement of pneumatic and hydraulic. The summary of attributes of pneumatic against hydraulic as follows:

* Hydraulic has the problems of fire, pollution, etc. on account of oil leakage, but pneumatic has not.

* Pneumatic circuit is operated under the pressure of 3 — 10Kgf/cm2 in general, and suitable for relatively low power operations because its generating power is lower than hydraulics'.

* Pneumatic is less efficient in speed control and intermediate stop than hydraulic because air is compressive, but can make it easy to Accumulate energy by means of tank according to how to use, and can be powerful in an instant by accumulating energy with small capacity compressor in case that the operation is intermittent.

* High speed operation is possible because the fluid resistance of pneumatic is less than those of hydraulic.

* the range of temperature in use of hydraulic is limited to 60 —- 70o C, but in case of pneumatic, the operation is possible up to 160o C approximately according to selection of instruments.

* Almost general factories have pneumatic piping system, so we can get the source of energy easily. Each unit of hydraulic needs hydraulic pump and circulation circuit, and numbers of working process in piping grow large.

1-2 Construction of pneumatic system

Pneumatic system is composed of 6 ~ 10 different components, which are connected systematically like Figure 1-1.

Figure 1-1 Construction of pneumatic system

1) Compressor: Compressor is equipment which transforms mechanical or electrical energy into pneumatic and classified according to size small, middle, large. It is general to generate 7~ 8Kgf/cm2 pneumatic and over 10Kgf/cm2 of generating pneumatic needs being aware of how to manage high pressure gas.

2) After cooler: In case the pneumatic of high temperature enters the equipment, troubles occur on account of flame and drain of seal materials of various kinds. After cooler is equipment which cools compressed air by water cooling or air cooling, and removes drain, etc.

3) Main-line air filter: The air which is compressed by compressor, contains dust, vapor, heated oil, etc. Main-line air filter is set up in order to remove them.

4) Refrigerated air dryer: In case pneumatic contains vapor», if this vapor is cooled down to normal temperature, the vapor is condensed into water in vent port of solenoid valve. Refrigerated air dryer is equipment which removes water of piping system that is come from vapor in compressed air by force in order to not condense vapor into water in equipment by means of dryer compressed air. (The dewing point 22°C) This system can be omitted under low pressure system.

5) Air filter: Air filter is an apparatus which removes dust and rust, and protect the using equipment from trouble. The compressed air that does not go through refrigerated air dryer does not remove drain, dust and rust in piping system.

6) Regulator for pneumatic: The compressed air that comes out of compressor has a little high pressure. This device regulates the pneumatic pressure in order to make it stable.

7) Lubricator for pneumatic: This device delivers lubricating oil by Using the flow of pneumatic in order to make smoothly operation smooth and improve the durability of using equipment.

• The functions 5~7 are mostly made up of one unit combination set.

8) Silencer for pneumatic: It makes a vent noise at the vent port when the selex valve is changed over. This device reduces such vent noise and removes noise pollution.

9) Selex valve (Solenoid valve): This device opens and shuts pneumatic or changes over the flow-direction by electrical signal, etc. The piston rod of pneumatic cylinder is used as controller of extending and retracting in Figure 1-1.

10) Speed control valve: This device controls the speed of piston rod of pneumatic cylinder by controlling the flow of pneumatic.

11) Pneumatic cylinders: This device transforms the energy of compressed air into needed power and movement. Generally a double acting cylinder holds the majority.