Pneumatic systems

LOW COST AUTOMATION
THROUGH
PNEUMATIC
SYSTEM
International Training Centre, Butibori
9001:2008
CERTIFIED INSTITUTE
By: Amol Khichade

CONTENTS
 About Automation
 About Pneumatics
 Applications
 Advantages & Disadvantages
 Pneumatic Standards
 Classification of Pneumatic elements
 Applications of air cylinders
 Components of Pneumatics
 Comparison between Pneumatic, Electro-pneumatic &
PLC based control system
 Air pressure losses
 Malfunctions of Pneumatic system
 General safety measures
 Basics Pneumatic circuits

•Automation is basically the delegation of human control
function to technical equipment for
•Increasing productivity
•Increasing quality
•Reducing cost
•Increasing safety in working condition.
What is Automation

Computer Numerical Control (CNC) Machine

Automation in Electronics Industry

Hydraulic System in Automobile

In general, automation in industries are classified into
three categories.
Out of the above three, pneumatic systems are used in
achieving Low Cost Automation in industries,
1) To reduce labor cost,
2) To reduce machine investment cost
3) To increase productivity
4) To reduce human efforts
INDUSTRIAL AUTOMATION
Pneumatics Hydraulics
Electrical and
Electronics

In Greek “Pneuma” means air.
Study (or) subject deal with “Pneuma” / compressed air is
called as “Pneumatics”.
Products that use compressed air as medium for operation
are called as “Pneumatic components”.
What is Pneumatics ?

 Mechanisms which
use air pressure to
apply mechanical
force and
displacement (work)
 The pneumatic
devices we use are
basically binary
actuators – either
retracted or
extended
Retracted
Cylinder
Extended
Cylinder
What is Pneumatics ?
continued…

Pneumatics is widely used by SMEs for implementing
“Low Cost Automation”
1) To reduce machine investment cost
2) To reduce the process time
3) To increase productivity, and
4) To have consistent quality
Automation .mp4
Low Cost Automation

Advantages and Limitations of Pneumatics
Advantages
 Simple
 Easy to control
 Can apply a lot of force from a small, light package
 Force is limited by air pressure and cylinder diameter
 The speeds and forces are infinitely variable

Advantages and Limitations of Pneumatics
continued…
Advantages
 Pneumatic tools when over loaded will stop and so safe,
as compared to electrical system.
 No fire hazard as in Electrical Systems. So can be
easily used in dangerous areas like mines.
 Simple in construction, the pneumatic system
components are easy to maintain & repair.
 The used air is exhausted. So no return lines as in
hydraulic system.

Disadvantages
 Smooth and uniform speeds against loads are not
achievable as in Hydraulic systems.
 Beyond certain load usage of pneumatic system is
expensive.

FORM OF OUTPUT
1. Linear motion
2. Rotary motion
3. Semi-rotary motion
APPLICATIONS
Pneumatic equipments can be used for applications, where
operation cycles need certain routine functions like
1. Pushing
2. Pulling
3. Lifting
4. Feeding
5. Clamping
6. Pressing
7. Forming, etc.

APPLICATION AREAS
1. Air brakes of automobile & trains.
2. Air engine
3. Pneumatic drills
4. Pneumatic press, power press
5. Auto motional of assembly line like automobile industry,
packaging, bottling
6. Pneumatic vehicle cleaning
7. Anti aircraft weapon
8. Pneumatic launchers
9. Vacuum pump
10. Pressure regulator
11. Cotton mills
12. Dairies
13. Forge shops
14. Foundries
15. Metal forming
16. Paper mills
17. Printings

Applications of
Pneumatic System

A double acting cylinder is used for embossing slide rules

Pins are to be fed to the next processing station using a
double-acting cylinder

Pneumatically controlled press with a stamping die

Arrangement for pushing work-piece

Small riveting machine with lever

Work piece clamping in Hacksaw cutting machine

Pneumatic injection in plunger type moulding machine

Leak test automated using pneumatic cylinders

Endurance test of spring done using pneumatic cylinders

Door opening & closing mechanism using air cylinder

Punching operation on thin sheets with air cylinder

Pneumatic cylinders used for automation in drilling machine

Pneumatic cylinders used in line feeding automation

PNEUMATIC STANDARDS
ISO 1219-1 Fluid power systems & components – Part 1:
Symbol for conventional use & data processing
applications.
ISO 1219-2 Fluid power systems & components – Part 2:
Circuit diagram
ISO 5599 Port marking of pneumatic directional control valves.
ISO 6432 Mounting dimensions of pneumatic cylinders: 8 to 25 mm
ISO 6431 Mounting dimensions of pneumatic cylinders: 32 to 320
mm.
CETOP RP41 Hydraulic & Pneumatic system circuit diagrams.
CETOP RP68P Identification code for ports and operators of pneumatic
control valve and other components.
ISO 8573 Quality classes of compressed air for general use

Classification Of Pneumatic Elements
Pneumatic elements are classified into 5 groups as
5. Working elements
Air cylinders
4. Final control elements
Flow control valve, Quick exhaust valve
3. Control elements
Directional control valves like solenoid
valves, pilot operated valves
2. Signal elements
Push button valve, Roller lever valve
1. Source & Service elements
Source – Compressor & Reservoir
Service – Filter, Regulator, Lubricator

1. Source & Service elements
1. Air
2. Compressor
3. Air Filter
4. Air Pressure Regulator
5. Air Lubricator
6. Air Service Unit
7. Pneumatic Silencer

Air
The earth is surrounded by an envelope of air known as atmosphere.
The composition of this 12 mile thick envelope. Due to the
compressibility of air, increasing the pressure causes decrease in the
volume of air.
Boyles Law: - Boyle discovered that the pressure and the volume of
a particular quantity of gas was constant provided that the
temperature did not vary.

PRESSURE MEASUREMENT
Atmospheric pressure = 1 Bar = 100Kpa = 100KNm2 = 14.5 PSI
F (Force, Newtons)
A(Area, metres squared)
P =
F
A
P (Pressure, Nm )-2

Compressors
A compressor is a machine that compresses air or another
type of gas from a low inlet pressure (usually atmospheric)
to a higher desired pressure level. This is accomplished by
reducing the volume of the gas. Air compressors are
generally positive displacement units and are either of the
reciprocating piston type or the rotary screw or rotary vane
types.
Graphic symbol

Types of compressor
•Piston Compressor
In this type of compressor a cylinder
bore encloses a moving piston. As the
crankshaft of the compressor rotate, the
piston moves within the cylinder,
similar to the piston in a car engine. As
the piston is pulled down, the volume
increases, creating a lower atmospheric
pressure in the piston chamber. This
difference in pressure causes air to
enter via the inlet valve. As the piston is
forced upwards the volume of air
reduces. The air pressure therefore
increases. Eventually the pressure
forces the outlet valve to open.

•Vane Compressor
The following figure shows a cutaway view of the sliding-vane-type
rotary compressor. The air inlet is placed where the volume of the
compression chamber is greatest, the outlet where the volume is
smallest. Consequently, as the vanes turn, the space between them is
reduced. This reduction in volume compresses the air as it travels from
the inlet to the outlet.

•Screw compressor
There is a current toward increased use of the rotary-type
compressor due to technological advances, which have produced
stronger materials and better manufacturing process. The
following figure shows a cutaway view of a single-stage screw
type compressor. Precise positioning of the screw is essential for
its performance. Oil provides a seal between the rotating screws
as well as lubricating the parts and cooling the air. The oil is
then separated from the air before it enters the system.

•Lobe compressor
In this type of compressor the rotors do not touch and
certain amount of slip exists. This slip increases as the
output pressure increases. It is therefore operated at
maximum speed for the highest efficiency. 17.3 bar is
obtainable with this type of constant displacement
compressor.
Inlet Outlet

Compressor Specification
Input volume of
air in liter/min
Input volume of
air in
cubic foot/min
Input voltage
in volt
Input frequency
in Hertz (Hz)
Input current
in Amp.
Output power in
Horse power (HP)
Output power in
Kilowatt (KW)
Rotating speed
of crankshaft in
revolution per
minute (rpm)
Output
pressure in bar
Output pressure
in pounds per
square inch (PSI)
Loudness of
output sound in
decibel (DB)

Air Filter
The air needs to be filtered to be free of moisture and contamination.
Air filter is used to do this job. The filter elements remove the particles
and moisture as small as 5 microns. Normally 30-50 micron filter is
used in pneumatic system.
Graphic symbol

Air pressure regulator
The pressure regulator is used to adjust the desired pressure for the
pneumatic system. This use a piston to sense downstream pressure
fluctuations. The piston, in turn, works against a set spring pressure.
As the pressure downstream drops it is sensed by the diaphragm and
the poppet valve opens. This adjusts the position of the poppet valve,
which limits the downstream pressure to the pre-set valve.
Graphic symbol

Air lubricator
A lubricator ensures proper lubrication of internal moving parts
pneumatics components. The proportional increase in oil mist by an
increase of air flow is achieved by the spring loaded poppet assembly.
As the flow increases and the valve opens, the area is increased and a
pressure differential created.
Graphic symbol

Air service unit
Filters, regulators and lubricators can be combined to ensure optimum
compressed air preparation for a specific pneumatic system.
Graphic symbol

Pneumatic Silencer
To decrease the noise of air in the outlet of valves, a silencer can be
used. They are made from the porous plastic or bronze. Some of them
are equipped with a control flow valve to control velocity of flow in the
outlet of valves as well.
Graphic symbol

2) SIGNAL ELEMENTS
General manual
Push button
Pull button
Push/pull button
Lever
Pedal
Treadle
Manually Operated
Rotary knob

Mechanically Operated
Plunger
Spring normally
as a return
Roller
Uni-direction or
one way trip
Pressure
Pilot pressure
Differential pressure
Detent in 3 positions

Solenoid
direct
Solenoid pilot
Solenoid pilot
with manual override
and integral pilot
supply
Solenoid pilot
with manual
override and
external pilot
supply
Electrically Operated
When no integral or
external pilot
supply is shown it
is assumed to be
integral

3) Direction Control Elements
 2/2 Direction control valve
Port & Position.mp4

Basically a valve is named in the following order
1. No. of positions
2. No. of ports
1. No. of positions
No. of positions Graphic symbol
2 position
3 position
1 2
1 2 3

2. No. of ports Symbol
2 ports
3 ports
4 ports
5 ports

1
2
3
4
5
Working ports
Symbols for valve actuations
are shown at the left hand side
or right hand side only
The lines drawn on the outside
of the square in the normal or
initial position represent the
ports
Exhaust
ports
Pressure
ports
Switching positions are shown
by squares and are drawn
adjacent to each other
Line with arrow represents
direction of flow. Shut-off
position is shown by T.
Normal position is the
switching position when the
valve is not actuated
GRAPHIC REPRESENTATION

Function 2/2
Normal position
Basic valves before
operators are added
Examples, push button operated
with spring return
2/2 DIRECTION CONTROL VALVE

Function 2/2
Operated position
Basic valves before
operators are added
with spring return

Function 3/2
Normal position
Basic valves before
operators are added
with spring return

Function 3/2
Operated position
Basic valves before
operators are added
with spring return

Function 4/2
Normal position
Basic valves before
operators are added
with spring return

Function 4/2
Operated position
Basic valves before
operators are added
with spring return

Function 5/2
Normal position
Basic valves before
operators are added
with spring return

Function 5/2
Operated position
Basic valves before
operators are added
with spring return

 Three position valves have a normal central
position that is set by springs or with a manual
control such as a lever
 The flow pattern in the centre position varies
with the type. Three types will be considered
 1, All ports sealed
 2, Outlets to exhaust, supply sealed
 3, Supply to both outlets, exhausts sealed

 All valves types shown in the normal position
 Type 1. All ports sealed
 Type 2. Outlets to exhaust
 Type 3. Supply to outlets

 All valves types shown in the first operated position

 All valves types shown in the second operated position

4) FINAL CONTROL ELEMENTS
(Flow control valve)
Throttle valve
Graphic symbol

Check valve or Non return valve
Graphic symbol

One way flow control valve
Graphic symbol

Quick exhaust Valve
Graphic symbol

LOGIC “OR” SHUTTLE VALVE
A
C
B
A
C
B
A B
C
Input Output
A B C
OFF OFF OFF
ON OFF ON
OFF ON ON
ON ON ON
Graphic symbol
 The OR logic valve has two
inputs and one output.
 The output is ON if one or two
inputs are ON
 And the output is OFF only if
all outputs are OFF.

LOGIC “AND” SHUTTLE VALVE
 The AND logic valve has two
inputs and one output.
 The output is ON only if all two
inputs are ON
 And the output is OFF if one or
more inputs are OFF.
A B
C
A B
C
A B
C
A B
C
A B
C
Popular old
symbol
A B
C
ISO 1219-1
symbol
Input Output
A B C
OFF OFF OFF
ON OFF OFF
OFF ON OFF
ON ON ON
Graphic symbol

How to actuate a single acting cylinder
Position 1 Position 2
3/2 way push button operated with spring return

How to actuate a double acting cylinder
Position 1 Position 2
5/2 way hand lever operated valve with spring return

Pneumatic Actuators
1. Pneumatic Cylinders
 Used for linear motion
2. Pneumatic Rotary Actuators
 Used for rotary motion
3. Pneumatic Semi-Rotary Actuators
 Used for linear & rotary motion

Pneumatic Cylinders
The cylinders converts the energy of the compressed air into
linear motion which extend or retract the piston rod.
Graphic symbol

Pneumatic Rotary Actuators
The rotary actuators converts the energy into a rotary motion.
Most of them is Vane air motor.
Graphic symbol

Pneumatic Semi-Rotary Actuators
Limited rotary motion can be achieved by incorporating a rack
and pinion into a linear actuator or as seen opposite by a Vane
Mechanism within the body of the cylinder.
Graphic symbol

Solenoid Valve
Graphic symbol
Direct-Acting Solenoid Valve Animation.mp4
1. Apply Current
2. Magnetic Field Builds
3. Plunger Become Attracting Magnets
4. Magnetic Force Drives Plunger

Working principle of Solenoid Valve
When an electric current flow through a coil, a magnetic
field is generated
The following applies to the
strength of the magnetic field.
•Increasing the numbers of
windings increases the field.
•Increasing the strength of
the current increase the field.
•Lengthening the coil reduces
the field.

TYPES OF SOLENOIDS
1) Push 2) Pull 3) Clapper
4) Rotary 5) Open 6) Closed

Comparison between Pneumatic, Electro
Pneumatic & PLC based control System
Parameter Pneumatic System Electro Pneumatic
System
PLC Based Control
System
Power medium Compressed air Compressed air Compressed air
Control
medium
Compressed air Electricity(AC/DC) Electricity(voltage or
current control)
Final control
elements
Pneumatically actuated
directional control valves
Solenoid operated
directional control valve
Solenoid operated
directional control valve
Signal
processing
Using logic valves, time
delay valves, pressure
sequence valves etc
Using relays, timers,
counters, pressure
switches etc
Using program elements
for logic, time-delay,
counting etc.,
Signal
elements
Permits energy flow in
the normal position
Inhibits energy flow in
the normal position
Scans for ‘1’ signal state
to allow power flow
Timers
On-delay & Off-delay
pneumatic timers
(NO/NC type)
On-delay and Off delay
electrical/electronic
timers
Program elements in on-
delay, off-delay, and
other modes
Memory
elements
Pneumatic latch (5/2-DC
double-pilot valve)
Electrical latch
(Dominant ON and
Dominant OFF circuits)
and 5/2-DC double
solenoid valve
Setting and resetting
instructions with coils or
boxes (set priority and
reset priority)
Counters
Up-counter & down-
counter(pneumatic)
Up-counter & down-
counter(electrical)
Program elements in up-
counting and down-
counting modes

Air pressure losses in pipelines

General Malfunctions in pneumatic system
Disturbances Possible causes Rectification
Machine is working, but
is weakening in
performance due to
slower operation
Upstream flow restriction or air
starvation
•Fit larger pipe
•Install larger compressor
Downstream flow restrictions •Check twisted tube/blocked silencers
downstream and renew
Lack of lubrication •Lubricate machines
•Fit air line lubricator
Actuator is weakening
in performance due to
slower operation
Flow regulator set too low •Re-adjust flow regulator
Tube twisted •Re-new
Piston rod bent •Repair or replace actuator
Barrel dented
Machine stop Failed pneumatic or electrical
supply
•Re-establish power supplies
Faulty products due to
faulty machine
adjustments or
misalignment of
components
Adjusting mechanism out of
alignment
•Re-adjust mechanism
Insufficient power to a
stamping or pressing actuator
•Increase pressure to the actuator or
replace the actuator with a large one
Leakage Loose joints, fittings or glands •Tighten loose joints, fittings or glands
Faulty or damaged fittings or
ruptured pipes and hoses
•Replace or repair the defective part

Malfunctions in Pneumatic Cylinders
With valve
connected, air
escapes out of vent
hole
(Double) cup packing is
leaking
•Replace cup packing
(Double) cup packing is
loose (or valve is defective)
•Tighten cup packing
Air escapes to
atmosphere at flange
bushing
Cup packing is leaking •Replace cup packing
Cup packing is mounted in
the wrong way
•Reverse cup packing
Air escapes at piston Groove ring is defective •Fit a new grooving
End position cushion
does not respond
Lip seal on the cushioning
plunger leaks or has been
fitted the wrong way round
•Fit a new lip seal
•Re-fit the lip seal
Single-acting
cylinder piston rod
does not return to
the end position
Composition spring is
damaged
•Fit a new spring
Misalignment of
piston/piston rod or
cylinder body
Excessive jerks •Align piston/piston rod or
cylinder body
Wrong operation •Set right the operation

Malfunctions in Pneumatic Valves
Valve leak •Dirt
•Broken seals
•Weak or broken spring
•Excessive wear
•Remove dirt
•Replace seals
•Replace spring
•Lubricate
Valve operating
mechanism fails
•Line pressure too low
•Control plunger broken
•Groove ring defective
•Corrosive damage to
surfaces by condensate
•Set control pressure
•Replace plunger
•Replace defective part
•Use proper lubricant
Valve plunger does not
return back
•Look for broken spring •Replace defective part
Sluggishness of valves •Dirt collected in the valve
especially at the groove ring
•Clean the vent hole
Valve fails to pass the
rated amount of air
•Actuating means not
stroking properly
•Bent trip cam
•Worn tripping mechanism
•Set right alignment
•Straighten trip cam
•Replace defective part
Failure of solenoid coil •Coil loosely fixed to the
solenoid stem
•Coil vibrates
•Overheating of coils
•Mismatched coils and stem
•Fix coil firmly to solenoid stem
•Fix coil firmly
•Fix coil firmly
•Use matched coils and stem

General Safety Measures
1. Keep your work place clean before and after work.
2. Use personal protective devices for all hazardous
jobs.
3. Follow the standard procedure while operating a
machine.
4. Know your job thoroughly
5. Inspect daily for damaged tubing, fittings & leaks
6. Check the interlock system at regular intervals
7. Repair or replace components that show signs of
wear or damage
8. Clean the spillage of grease, oil, etc., immediately
9. Never direct the compressed air towards yourself or
anyone else for cleaning
10. Never use the compressed air for cleaning away
chips and dust. Flying particles can be dangerous.

Basics Pneumatic circuits
A pneumatic circuit is usually designed to
implement the desired logics. However, there
are several basics circuits, which can be
integrated into the final circuit.

Air pilot control of double-acting cylinder
In single acting cylinder compressed air is applied on only one side of
the piston face. The other side is open to atmosphere. For return
movement of the piston spring is used. This actuator can produce
work in only one direction. Single acting cylinder with built in spring
the stroke length is limited due to natural length of spring. Single
acting cylinder are available in stroke length up to approximately
100mm. Due to construction and simplicity it is suitable for compact
short stroke.
Ex. 1)

Directional control valve are giving path to an air stream. It controls
actuator. The directional control valve is characterized by its number
of controlled connection or ways and by the number of switching
position.
5/2 way D.C. valve has got 2 position and 5 ports i. e. 2 exhaust, 2
outputs & 1 input.
The 5/2 way valve is used primarily as a final control element for the
control of double acting cylinder.
Ex. 2)

The 5/3 way valve has five ports and three position. In this valve
lines are closed in the middle position. This enables the piston rod of
cylinder to be stopped in any position over its range of stroke
although intermediate position of the piston rod cannot be located
accurately its symbol is as follows.
Ex. 3)

Pneumatic systems

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