Chapter 7 Pneumatic Systems Kasrul

PNEUMATICS SYSTEM
Chapter 7
Properties of Compressed Air
Availability
Easily stored in large volumes
Simplicity in design and control
Provides linear and rotary movement
Low system cost due to low component
cost
Properties of Compressed Air
Components have long working life

resulting in longer system reliability
Environmentally friendly
Safety issues are minimized e.g.. Fire
hazards; unaffected by overloads
(actuators stall or slip)
Pneumatic actuators in a system do not
produce heat (except for friction)
Pneumatic system
A pneumatic system uses compressed air, and this

usually stored in a pressure vessel called an air
receiver.
Air, from atmosphere, is delivered to the air receiver
by a motor-driven compressor. Unlike the hydraulic
pump, the compressor is controlled by a pressure
switch on the air receiver and either starts/stop on
demand or vents to atmosphere when the receiver is
charged.
Pneumatic system
The cylinder movement is again controlled by a

directional control valve, but air returned from the
cylinder vented to atmosphere.
A pneumatic system is an open system, the air
being obtained from and returned to the
atmosphere.
Pneumatic systems also require clean dry air. A
practical pneumatic system has additional air
treatment elements not present in a hydraulic
system.
Pneumatic power supply
Electric motor drives an air compressor.

Air
inlet to the compressor
is supply
likely to be
Pneumatic
power
filtered and via a silencer to reduce the noise
level.
Pressure relief valve provide protection
against the pressure in the system rising
above the safe level.
Since the air compressor increases the

Pneumatic
power
supply
temperature
of the
air there
is likely to
be cooling system and to remove
contamination and water from the air via
a filter and water trap.
An air receiver increases the volume of
air in the system and smoothes out any
short term pressure fluctuations.
Pneumatic Compressor
The compressors compress the air from atmospheric

pressure to the desired working pressure.
The compressor converts air at atmospheric pressure
into high pressure by changing it volume.
Compressed air serves as a source of pneumatic
energy by producing pressurized air.
Two types of pneumatic compressor:
Positive Displacement Compressor

Dynamic Compressor (Blowers)

Confine the air within a closed space and compress it
by decreasing the volume of the space.
Basically producing a low volume high pressure air
supply.
Two types:
Reciprocating piston compressor

Rotary piston compressor
Reciprocating piston compressor
Most widely used.

When higher pressure is required, a multistage compressor
is used.
Reciprocating compressors
Two stage reciprocating compressors
Air Compression
Reciprocating:
Single stage
Double Stage
Rotary piston compressor
Compressor with rotating piston

Advantage over reciprocating compressor: Compact
dimensions, quiet running and smooth, steady air delivery.
Disadvantage: slightly reduced efficiency and lower
operating pressures
Two types:
Vane compressor
Screw compressor
Vane compressor
Same operation as Vane pump.
Screw compressor
Uses two intermeshing counter-rotating screws.

These mesh with a clearance of a few thousandths of an
inch, and are driven by timing gears.
As the screw rotate, pocket of air are carried from the inlet
port to the outlet port.
Vane compressor
Screw compressor
Air Compression Rotary:
Vane
Screw
Draw air in one side and compress it by mass acceleration.

Dynamic compressor accelerates the air by rapidly turning
the rotor blade.
Basically they are large volume low pressure device.
Two types of blower

Centrifugal type
Axial type
Axial type
Centrifugal type
A Basic Pneumatic System

Air Production and Distribution System
Refrigerated Air Dryer
Compressor
Pressure Gauge
Check Valve
Motor
Tank
Drain
Pressure
Switch
Line Filter
A Basic Pneumatic System

Air Consumption System
Air Line Take-off

Directional Valve
Conditioning
Actuator
Unit
Drain
Compressor
Air Receiver
A pressure Vessel (Tank) normally made of metal and installed
either horizontally or vertically. This vessel provides a volume of air
to be utilized by the system and reduced the loading and unloading
of the compressor.
Air Receiver (Tank)
Air Treatment
All atmospheric air carries both moisture and dust
Inlet Filter
Used to remove large particle dirt from

entering the system.
Used to prevent excessive

wear of cylinder, piston rings
and other moving parts in the
initial stage of the system
Air Dryer
Compressed air cannot hold the same amount of moisture as non
compressed air. Once the air is compressed, some of the moisture
condenses in the tank and is removed through a drain valve. The remaining
moisture will rust internal components of the system and must be removed.
One way this is done by sending the air through an air conditioned chamber
which will condense more of the moisture which is present.
Regulating and Conditioning

The compressed air to be used in a system needs to be treated
because of contamination inside the system. An example of this
could be the scaling of piped or worn seal material. A line filter is used
to collect water and solid impurities. A Lubricator is used to vaporize
oil into the air stream to lubricate moving parts in the system such as
air tools
A regulator is used to adjust the
line pressure to a lower usable
pressure needed for some tool
applications.

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PNEUMATICS SYSTEM

Properties of Compressed Air

Properties of Compressed Air

Components have long working life

A pneumatic system uses compressed air, and this

The cylinder movement is again controlled by a

Pneumatic power supply

Electric motor drives an air compressor.

Since the air compressor increases the

The compressors compress the air from atmospheric

Two types of pneumatic compressor:

Positive Displacement Compressor

Positive Displacement Compressor

Reciprocating piston compressor

Positive Displacement Compressor

Reciprocating piston compressor

Most widely used.

Two stage reciprocating compressors

Positive Displacement Compressor

Rotary piston compressor

Compressor with rotating piston

Positive Displacement Compressor

Same operation as Vane pump.

Uses two intermeshing counter-rotating screws.

Positive Displacement Compressor

Positive Displacement Compressor

Air Compression Rotary:

Dynamic Compressor (Blowers)

Draw air in one side and compress it by mass acceleration.

Two types of blower

Dynamic Compressor (Blowers)

A Basic Pneumatic System

A Basic Pneumatic System

Air Line Take-off

Air Receiver (Tank)

Used to remove large particle dirt from

Used to prevent excessive

Regulating and Conditioning

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