Pneumatic systems use pressurized air to make things move. A basic pneumatic system consists of an air generating unit and an air-consuming unit. Air compressed in a compressor is not ready for use. The air has to be filtered, the moisture present in air has to be dried, and, for different applications in the plant, the pressure of air has to be varied. Several other treatments are given to the air before it reaches finally to the actuator. Figure
3.2 gives an overview of a basic pneumatic system. Some accessories are added for economical and efficient operation of system.
A typical pneumatic power system includes the following components:
1. Compressor
2. Electric motor
3. Air receiver
4. Pressure switch
5. Safety valve
6. Auto drain
7. Check valve
8. Pressure gauge
9. Air dryer
10. After filter
11. Air service unit
12. Direction control valve
13. Pneumatic actuator
1. Compressor: A device, which converts mechanical force and motion into pneumatic fluid power, is called a compressor. Every compressedair system begins with a compressor, as it is the source of airflow for all the downstream equipment and processes.
2. Electric Motor: An electric motor is used to drive the compressor.
3. Air Receiver: An air receiver is a container in which air is stored under
pressure.
4. Pressure Switch: A pressure switch is used to maintain the required pressure in the receiver. It adjusts the high pressure limit and low pressure limit in the receiver. The compressor is automatically turned off when the pressure is about to exceed the high limit and it is also automatically turned on when the pressure is about to fall below the
low limit.
5. Safety Valve: The function of the safety valve is to release extra pressure if the pressure inside the receiver tends to exceed the safe pressure limit of the receiver.
6. Auto Drain: Air condenses to give out water in the receiver and a device called auto drain directs this water out.
7. Check Valve: The valve enables flow in one direction and blocks flow in a counter direction is called check valve. Once compressed air enters the receiver via check valve, it is not allowed to go back even when the compressor is stopped.
8. Pressure Gauge: The pressure gauge tells us the pressure inside the compressor receiver.
9. Air Dryer: A device for reducing the moisture content of the working compressed air.
10. After Filter: A filter that follows the compressed air dryer and usually used for the protection of downstream equipment from desiccant dust, etc. is called an after filter. The name filter refers to a device whose primary function is the removal of insoluble contaminants from a liquid or a gas with the help of porous media.
11. Air Service Unit: Filter, regulator, and lubricator combined in one device is popularly known as an air service unit or F.R.L unit. Its purpose is to supply air to other successive applications in the line. It provides clean air at the required pressure with lubricant added to it to increase the life of equipment.
12. Direction Control Valve: Directional-control valves are devices used to change the flow direction of fluid within a pneumatic/hydraulic
circuit. They control compressed-air flow to cylinders, rotary actuators, grippers, and other mechanisms in packaging, handling, assembly, and countless other applications. These valves can be actuated either manually or electrically.
13. Pneumatic Actuator: A device in which power is transferred from one pressurized medium to another without intensification. Pneumatic actuators are normally used to control processes requiring quick and accurate response, as they do not require a large amount of motive force. They may be reciprocating cylinders, rotating motors, or may be robot end effectors.
A few more components can be added to the system; first, an air intake filter and second, an air intercooler (if a multistage compressor is used). The function of the former is to prevent the entry of vast quantities of dust and dirt along with air and the latter is to cool the air again to room temperature after it is discharged from the low-pressure compressor.