Introduction to Pneumatic Systems: Basic Requirements for Pneumatic System,Applications, Pneumatic fundamentals, Construction, working principle and operation of pneumatic power transmission system components like Power source, FRL unit, Actuators and control valves like DCV, FCV, PCV, time delay, quick exhaust, twin pressure, shuttle

1. CHAPTER 6
INTRODUCTION to pneumatic system
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Prepared by : Prof. Rahul Thaker
Department of Mechanical Engineering
Alpha College of Engineering & Technology

2. Contents
 Introduction
 Basic Components of a Pneumatic System , Advantages ,
Disadvantages
 Main Pneumatic Components
 Compressors and
 Pressure regulating components.(FRL Unit)
 Directional control valves (DCVs)
 Execution components (cylinders)
 Solenoid Actuated Dc Valves
 Control Valve
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3. PNEUMATIC SYSTEMS
 A pneumatic system is a system that uses compressed air
to transmit and control energy. Pneumatic systems are
used in controlling train doors, automatic production
lines, mechanical clamps, etc.
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4. Basic Components of a Pneumatic
System
4
Figure 1 Components of a pneumatic system
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5. Basic Components of a Pneumatic
System
5
Figure 1 Components of a pneumatic system
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6.  Air filters: To filter out the contaminants from the air.
 Compressor: Compressed air is generated by using air compressors. Air
compressors are either diesel or electrically operated.
 Air cooler: During compression operation, air temperature increases.
Therefore coolers are used to reduce the temperature of the compressed air.
 Dryer: The water vapour or moisture in the air is separated from the air by
using a dryer.
 Control Valves: To regulate, control and monitor for control of direction
flow, pressure etc.
 Air Actuator: Air cylinders and motors are used to obtain the required
movements of mechanical elements of pneumatic system.
 Electric Motor: Transforms electrical energy into mechanical energy. It is
used to drive the compressor.
 Receiver tank: The compressed air coming from the compressor is stored
in the air receiver.
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7. Advantages of Pneumatic Systems
• High Effectiveness – use of compressed air in not restricted by
distance & can easily be transported.
• High durability and reliability – Extremely durable and not damaged
easily.
• Simple Design - more suitable for use in simple automatic control
systems.
• High adaptability to harsh environments - compressed air is less
affected by high temperature, dust, corrosion, etc.
• Safety - Because they can work in inflammable environment
without causing fire or explosion.
• Easy selection of speed and pressure
• Environment friendly - The operation of pneumatic systems do not
produce pollutants.
• Economical - The costs of pneumatic systems are quite low.
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8. Disadvantages of Pneumatic Systems
• Relatively low accuracy - The volume of air may change when
compressed or heated, the supply of air to the system may not be
accurate.
• Low loading - As the cylinders of pneumatic components are not
very large, a pneumatic system cannot drive loads that are too
heavy.
• Processing required before use - Compressed air must be
processed before use to ensure the absence of water vapour or
dust.
• Uneven moving speed - As air can easily be compressed, the
moving speeds of the pistons are relatively uneven
• Noise - Noise will be produced when compressed air is released
from the pneumatic components.
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9. Main Pneumatic Components
• Pneumatic components can be divided into two categories:
1. Components that produce and transport compressed air.
2. Components that consume compressed air.
• All main pneumatic components can be represented by simple
pneumatic symbols. Each symbol shows only the function of
the component it represents.
• Pneumatic symbols can be combined to form pneumatic
diagrams.
• A pneumatic diagram describes the relations between each
pneumatic component, that is, the design of the system.

10. Production and Transportation of
compressed air
 Examples of components that produce and transport
compressed air include
Compressors and
Pressure regulating components.(FRL Unit)

11. Compressors
• A compressor can compress air to the required pressures.
• It can convert the mechanical energy from motors and
engines into the potential energy in compressed air .
• A single central compressor can supply various
pneumatic components with compressed air, which is
transported through pipes from the cylinder to the
pneumatic components.
• Compressors can be divided into two classes:
reciprocating and rotary.

12. Pneumatic Symbol for Compressor
Rotary
Compressor
Reciprocating
Compressor

13. Pressure Regulating Component
 The purpose of the fluid conditioners is to make the
compressed air more acceptable and suitable fluid
medium for the pneumatic system
 Air filter, Pressure Regulator and lubricator are now
built as packaged combination known as service units
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14. Pressure Regulating Component
Pressure regulating components are formed by various
components, each of which has its own pneumatic symbol:
I. Air Filter – can remove impurities from compressed air
before it is fed to the pneumatic components.
II. Pressure regulator – to stabilise the pressure and
regulate the operation of pneumatic components.
III. Lubricator – To provide lubrication for pneumatic
components

15. Air Filters
 The purpose of the air filter is to clean the compressed air
of all impurities and any condensate it contains.
Function of air filters
 To remove all foreign matter and allow dry and clean air
flow without restriction to regulator and then to the
lubricator
 To condensate and remove water from the air
 To arrest fine particles and all solid contaminants from
air
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Air Filters…

17. The function of the air pressure regulator is to maintain
working pressure virtually constant regardless of
fluctuations of the line pressure and air consumption.
When the pressure is too low, it results in poor
efficiencies and when the pressure is too high, energy is
wasted and equipment’s performance decay faster.
Generally pressure is regulated in pneumatic system at two
places.
 At the receiver tank
 In the load circuits
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Air Regulator

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Spring Adjusting
Screw
Body
Main Spring
Valve
Diaphragm
Dampening Spring
Vent-Hole
Pressure Regulator …

19. Air Lubricator
 The function of air lubricator is to add a controlled
amount of oil with air to ensure proper lubrication of
internal moving parts of pneumatic components.
Lubricants are used to
 To reduce the wear of the moving parts
 Reduce the frictional losses
 Protect the equipment form corrosion
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Air Lubricator…

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FILTER REGULATOR LUBRICATOR UNIT (FRL UNIT)

22. FRL UNIT…

23. The consumption of compressed air
• Examples of components that consume compressed air
include;
• Execution components (cylinders)
• Directional control valves (DCVs) and
• Assistant valves.

24. Execution Component
 Pneumatic execution components provide rectilinear or
rotary movement.
 Examples of pneumatic execution components include
cylinder pistons, pneumatic motors, etc.
 Rectilinear motion is produced by cylinder pistons, while
pneumatic motors provide continuous rotations.
 There are many kinds of cylinders, such as single acting
cylinders and double acting cylinders.

25. Single Acting Cylinder
 A single acting cylinder has only one entrance that allows
compressed air to flow through.
 Therefore, it can only produce thrust in one direction.
 The piston rod is propelled in the opposite direction by an
internal spring, or by the external force provided by
mechanical movement or weight of a load.

26. Single Acting Cylinder

27. Double Acting Cylinder
• In a double acting cylinder, air pressure is applied
alternately to the relative surface of the piston, producing a
propelling force and a retracting force.
• As the effective area of the piston is small, the thrust
produced during retraction is relatively weak.
• The impeccable tubes of double acting cylinders are usually
made of steel.
• The working surfaces are also polished and coated with
chromium to reduce friction.

28. Double Acting Cylinder

29. Directional Control Valve (DCV)
 The primary function of a DC valve is to direct or prevent
fluid flow to specific piping or system actuator.
 These valves usually consists of spool inside it which is
electrically/hydraulically controlled.
 There are two fundamental positions of these valves :
1. Working Position
2. Normal Position

30. Directional Control Valve (DCV)
 According to no. of valve ports and spool position
 DC valve can be categorized into following :
1. 2-way, 2-position
2. 3-way, 2-position
3. 4-way, 2-position
4. 4-way, 3-position and many more…

31. Directional Control Valve (DCV)
• Directional control valves ensure the flow of air between
air ports by opening, closing and switching their internal
connections.
• Their classification is determined by the number of ports,
the number of switching positions, the normal position of
the valve and its method of operation.
• Common types of directional control valves include 2/2,
3/2, 5/2, etc.
• The first number represents the number of ports; the
second number represents the number of positions.

32. Directional Control Valve (DCV)
 A directional control valve that has two ports and five
positions can be represented by the drawing in Fig., as
well as its own unique pneumatic symbol.

33. Directional Control Valve (DCV)
 Common Abbreviation used in DCV
P = Pressure line
T = Tank Line
A,B = System Actuator line
X = Pilot Line
Y = Drain Line

34. 2/2 Directional control valve
 The structure of a 2/2 directional
control valve is very simple.
 It uses the thrust from the spring to
open and close the valve, stopping
compressed air from flowing towards
working tube ‘A’ from air inlet ‘P’.
When a force is applied to the control
axis, the valve will be pushed open,
connecting ‘P’ with ‘A’ .
 The control valve can be driven
manually or mechanically, and
restored to its original position by the
spring.

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36. 3/2 Directional control valve
• A 3/2 directional control valve can be used to control a
single acting cylinder.
• The open valves in the middle will close until ‘P’ and ‘A’ are
connected together. Then another valve will open the
sealed base between ‘A’ and ‘R’ (exhaust).
• The valves can be driven manually, mechanically,
electrically or pneumatically. 3/2 directional control valves
can further be divided into two classes: Normally open
type (N.O.) and normally closed type (N.C.).

37. 3/2 Directional control valve

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39. 5/2 Directional control valve
• When a pressure pulse is input
into the pressure control port
‘P’, the spool will move to the
left, connecting inlet ‘P’ and
work passage ‘B’.
• Work passage ‘A’ will then make
a release of air through ‘R1’ and
‘R2’.
• The directional valves will
remain in this operational
position until signals of the
contrary are received.
• Therefore, this type of
directional control valves is said
to have the function of
‘memory’.

40. 5/2 Directional control valve

45. SOLENOID ACTUATED DC
VALVES
 It is an electro-mechanical device that take electrical
energy and produces a linear force by the use of
magnetism. It is basically a winding of wire around a
metal core.

46. SOLENOID ACTUATED DC
VALVES
 When the solenoid is energized, the air gap is closed
quickly and a force is developed in the direction of the
valve spool.

47. Control Valve
 A control valve is a valve that controls the flow of air.
 Examples include
 Non-return valves,
 Flow control valves,
 Shuttle valves, etc.

48. Control Valve

49. Non Return Valve
 A non-return valve allows air to flow
in one direction only.
 When air flows in the opposite
direction, the valve will close.
 Another name for non-return valve
is poppet valve

50. Non Return Valve

51. Flow Control Valve
 A flow control valve is formed by a non-return valve
and a variable throttle.

52. Shuttle Valve
 Shuttle valves are also known as
double control or single control
non-return valves.
 A shuttle valve has two air inlets
‘P1’ and ‘P2’ and one air outlet ‘A’.
 When compressed air enters
through ‘P1’, the sphere will seal
and block the other inlet ‘P2’.
 Air can then flow from ‘P1’ to ‘A’.
 When the contrary happens, the
sphere will block inlet ‘P1’,
allowing air to flow from ‘P2’ to
‘A’ only.

53. Shuttle Valve

59. ADVANTAGES AND
DISADVANTAGES Advantages:
very flexible , free-format syntax.
Supported by every product.
It can express arithmetic operations as well
as operations to aggregate data and sort data for
output.
 Disadvantages:
It is not a general-purpose programming
language and thus the development of an
application requires the use of a SQL with a
programming language.