4. Less expensive thanhydraulc systems.5. Valve operations aremucheasierinpneumatic systems.

Disadvantages:1.It issuitable for low pressureapllications (upto 17bar).2. Precise position and velocity control is not possible.3. It requires seperatelubricator unitwhich may induce excessive wear and corrosion.

Typical applications:

Stamping,Drilling, punching, clamping, assembling, riveting, material handling and logic controlling operations.

Properties of air:

Air - 78% nitrogen, 21% oxygen,and1% othersuch as argon carbon di oxide.Air isheavier than gases.The reference point for pressure is mean sea level where the atmospheric pressure is 1.013 bar.Air density changeswith respect to changes in pressure and temperature.

AIR COMPRESSOR An air compressor is a machine for compressing air from a low intake pressure usually

atmospheric pressure to higher delivery pressure, by reducing the volume of air.

RECIPROCATING AIR COMPRESSORSReciprocating design may be either single stage or multi stage compressor. Fig below shows a single stage aircompressor

SINGLE STAGE COPRESSOR:

1.During downward stroke low pressure atmospheric air drawn into the cylinder through inlet valve2. At the end of the stroke the inlet valve closes.3. During upward movement of the piston the pressure rises continuously upto desired level 4. After which the delivery valve is opened.5. Since single piston is used for compression from initial inlet pressure to final desired pressure in one compressive step, this is knoen as single stage compressor.

MULTI STAGE COMPRESSOR :

1. A Compressor having two or more compressive stages is known as multistage compressor

2. If single cylinder is used for high pressure air, the cylinder size will be too large and the temperature rise is high.3. This higher temperature rise leads to expansion air which inturn needs enormous effort of the piston to compress, finally result in damage of the cylinder.Thus it is necessary to use multistage compression with intercooling arrangement to get high pressure air.4. In multi stage compressors, successive cylinder size decrease and the intercooling removes a significant portion of the heat of compression.5. This increases air density and the volumetric efficiency of the compressor.

fig below shows themulti stage air compressor

ROTARY VANE COMPRESSOR:1. In this design the cylinderical sotted rotor is off center to the housing and turns inside the housing.2. Each rotor slot is fitted with a rectangular vane.3. As the rotor spins the vanes are kept in contact with the housing by centrifugal force and there fore slides in and out .4. As rotor turns, air trapped between the vanes. 5. Air is pushed out during the other half of each revolution as the space decreases.

Rotary screw compressor:A rotary screw compressor compresses air between two intermeshing screws andoil is

used as a coolant to remove some ofthe heat of compression.

Above figure shows top view of single stage rotary compressor.1. Compression is done by allowing the trapped air in the small space between meshing elements.2. Screws rotate in opposite direction.

Filter Regulator Lubricator Unit:A trio combination unit is a fluid conditioning unit thatinclude a filter,regulator and

lubricator as a single unit in all pneumatic systems.It is frequently known as filter-regulator-lubricator (FRL) unit.

The explaination of the above three units are follows:I.Air Filter:

1.An air filter is a device used to remove contaminnts from the air befroeit reaches the pneumatic components such as valves and actuators.

2 Air line filters are generally fitted with a filter with element that removes contaminants in the range of25 to 50 microns.

3. Air enters through the inlet and flows through the deflector plate, causing the air to swirl.4.This swirl removes the larger particles. 5. Centrifugal force causes water and larger solid to be hurdled against the interior wall.6. Then gravity carries them down to the bottom, which is called quiet zone,where there isno air flow.7. The baffle seperates thequiet zone and prevent these particles from re-entering the air stream..8. Then air is passed through the filter element where smaller particles are filtered.9. Theshroud blocks the air entering the filter element before removing larger particles.

II. Air Regulator:1.Air pressure regulators are used to regulate the supply pressre which are fluctuating in

nature that causes inconsistancy in machine performance.

FIG. Air regulator2. Air flowfrom inlet to outlet through main poppet. The main poppet stem has a light

spring on the bottom and a diaphragm at the top. 3. When the outlet pressure is high the fluid flowtothe diaphragm through pilot

openeng, causing the diaphragm to deflect upward against the main spring. 4.The main poppet follows the motion ofthe diaphragm due to the stem. This stops

theflow from inlet by the main poppet.5. The pressure setting of the reguator can be modified by changing the compression of

the main spring with the adjusting screw.6.Further pressure increase even after the main poppetclosed caused the diagram to

continue deflecting upward and pull away from the main poppet stem. This causes a small hole to be uncovered in the diaphragm, allowing excessive pressure to be relieved through the vent.

7. This is also known as SELF RELIEVING REGULATOR.