Chapter 1 - Introduction to Pneumatic System

Air Dehydration

1

There are 2 types
Air Dehydration
Continuous cool
(After coolers)
Air Dryer

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23

s of Continuous cooler Air Dryer
n: (Aftercoolers) • Absorbance
ler a. Air cool – the
) cooling process Drying
• Adsorption
is done by air
b. Water cool – the Drying
• Coolant Drying
cooling process
is done by water

UCTION TO PNEUMATIC SYSTEM 2211

Continuou

1. Air will be hot after final 3. This process
compression, thus it will done immed
deposit water in the pipeline compression
when the air cools down. air to afterco
The water deposited in the may help to
pipeline is in considerable amount of w
quantities which should be due to cond
avoided.

2. To prevent this, cooler is
used to reduce the
temperature of the
compressed air in pneumatic
systems. This is needed for
the normal operation of
pneumatic systems.

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us cooler 4. Aftercoolers are heat
exchangers, being either air
s need to be cooled or water cooled units.
diately after
n by forcing the 5. It is generally equipped with a
ooler which water separator with
o reduce the automatic drainage and
water produced should be placed close to the
densation. compressor.

6. Nowadays, an after-cooler is
built into modern
compressors to ease the
process.

UCTION TO PNEUMATIC SYSTEM 2222

Continuous Cooler

a. Air cooled

This type of aftercooler uses air to cool down the compressed 1. T
air. This air cooled aftercooer consists nest of tubes as shown in c
figure (a). Hot air enters the aftercooler through inlet and a
passes by the nest of tubes. The air will be cooled down by
means of cold air produced by fan assembled in the aftercooler. 2. T
c
1
c
a
p

a. Principle of an air cooled aftercooler
(Image courtesy of SMC basic pneumatic manual)

Click here to watch
a. Air cooled cooler
b. Water cooled cooler

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b. Water cooled

This type of aftercooler uses water to cool down the hot air after
compression. The arrangement of the air inlet, air outlet, water inlet
and water outlet are as shown in the figure (b).

The flow of water and air should be opposite direction through the
cooler. Temperature of the air discharged should be approximately
10°C above the temperature of the cooling water. The accumulated
condensation is removed through an automatic drain, attached to
aftercooler. Usually, aftercoolers equipped with a safety valve,
pressure gauge, and thermometer pockets for air and water.

b. Principle of a water cooled aftercooler 2233
(Image courtesy of SMC basic pneumatic manual)

UCTION TO PNEUMATIC SYSTEM

Air dryer (d

1. Even though, compressed air passed through
an aftercooler which causes condensation
and removes most of the water, filters are
installed to remove additional water, if any.
However, if a system requires further air
treatment, air dryer is preferred.

2. Air dryer ensures most or all of the water in
compressed air is removed before it reaches
critical components or processes.

3. There are three main types of air dryer
available which operate on an absorption,
adsorption or refrigeration process, will be
discussed in this section.

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(Images courtesy of SMC basic pneumatic manual)

a b c

Absorption Adsorption Coolant drying
deliquescent) (desiccant) (Refrigerant
drying)
Drying Drying

UCTION TO PNEUMATIC SYSTEM 2244

Air dryer - absorption

1.

2.

3.
Principle of the absorption air dryer

(Image courtesy of SMC basic pneumatic manual)

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a. Absorption (deliquescent) Drying

The compressed air is forced to enter through a desiccant
which has dehydrated chalk or magnesium chloride that
remains in solid form. Lithium chloride or calcium chloride
reacts with moisture to form a solution, which is discharged
from the bottom of the container.

During operation, the dew point of the desiccant will
increase with the consumption of salt, but a pressure dew
point of 5°C at 7 bar is possible. Thus, desiccant must be
replenished regularly.

The main advantage of this method is the low initial and
operating costs, but the inlet temperature should not exceed
30°C. Since the chemicals used has high corrosive
characteristics, it has to be carefully monitored and filtered
so that small corrosive mists does not enter into the
pneumatic system.

UCTION TO PNEUMATIC SYSTEM 2255

Air dryer – adsorption

Principle of the heatless 1. Desiccant air dryer has dif
adsorption air dryer onto a desiccant material
which means this is air dry
(Image courtesy of SMC basic pneumatic
manual) 2. Silica gel or activated alum
This chemical contained in
passing through it. The dry
column when it becomes

3. Wet compressed air enter
as dried air to the outlet p

4. 10 – 20% of the dry air wil
moisture from the desicca

5. To provide continuous dry
valve so that the supply ai

6. The degree of saturation o
indicator.

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b. Adsorption (desiccant) Drying

fferent working principle where moisture from the air stream and
is adsorbed in a reversible process. Dew points produced is low
yer is a good choice when process require extremely dry air.

mina in granular form is used as a chemical in this drying process.
n a vertical chamber to absorb moisture from the compressed air
ying agent is regenerated by drying or heating in a regenerating
saturated as shown in the Figure.

rs to the column 1 through a directional control valve and comes out
port.

ll pass through the orifice O2 and go to the column 2 to reabsorb
ant to regenerate it. The regenerating air flow then goes to exhaust.

y air, a timer is used to switch periodically the directional control
ir is allowed alternately to one column.

of the desiccant may be monitored by incorporating a colour

UCTION TO PNEUMATIC SYSTEM 2266

Air dryer - coolant drying (r

1. This m
remov
moistu
separa

2. The air
pressu
genera

3. For cri
metho

4. This dr
circuit

5. Refer t

Principle of the cool
(Image courtesy of SM

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refrigerant drying)

method cools the compresses air temperature by
ves water and causing condensation. The accumulated
ure in liquid form is collected by an internal moisture
ator and sends it to a drain.
r generated by refrigerated dryers typically with
ure dew points between 35 and 40° F, mostly used in
al plant operations.
itical processes which requires extremely dry air, this
od may not be suitable.
ryer is a mechanical unit consisting a refrigeration
t, and two heat exchangers.
the diagram for the sequence of the process.

lant air dryer
MC basic pneumatic manual)

UCTION TO PNEUMATIC SYSTEM 2277

Air Treatm

1 2

Atmospheric air consists of dust Besides that, gumm
and moisture. Dust usually will be may be formed fro
removed by the filter fixed at the of carbonised oil, p
intake of the compressor. other foreign matt
Meanwhile, moisture condenses sealing material. T
out during the continuous cooling injurious effects on
and drying process. However, there equipment by incr
will always be some moisture component wear,
which will be carried over. corrosion and stick

INTRODU

ment

2 3

my substances To eliminate these contaminants,
om fine particles further air treatment is required to
pipe scale and ensure the compressed air is as
ter, such as worn clean as possible to the point of
This can result in use.
n pneumatic
reased seal and
seal expansion,
king valves.

UCTION TO PNEUMATIC SYSTEM 2288

Air fil

1. To clean the compressed air of all
impurities and any condensate it contains.

2. To remove all foreign matter

3. To allow dry and clean air flow without
restriction to regulator and then to the

lubricator
4. To condensate and remove water

from the air

5. To arrest fine particles and all solid
contaminants from air

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lters

6. There are three types of air filters

7. The standard filter is a combined
water separator and filter.

8. A micro-filter is used when contamination by
oil vapour is undesirable,

9. A sub-micro filter will remove
virtually all oil and water and also fine
particles down to 0.01 of a micron…

10. To provide maximum protection for
pneumatic precision measuring devices,

electrostatic spray painting

UCTION TO PNEUMATIC SYSTEM 2299

Function and prin

Pressure 1. This component is used to
Regulator maintain the specific, precise
pressure required by a particular
application, regardless of the rise
and fall of line and/or receiver
pressure as the compressor cuts
in and out.

2. An air pressure regulator is used
to ensure the pressure delivered
to certain components is safe by
reducing the pressure and also
ensure the amount of pressure
received by cylinder is the exact
amount of thrust required.

(Images courtesy of SMC basic pneumatic

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nciple of FRL unit

1. Single filter regulator unit
is a combination of air
filter and pressure
regulator which provide a
compact space saving
unit.

Filter-regulator 3300
(FR) Unit

manual)

UCTION TO PNEUMATIC SYSTEM

Function and prin

1. Pneumatic components usually Air Lubricator
consist of internal moving part, thus
adding controlled amount of oil (Images courtesy of SMC
lubricant helps to ensure proper
lubrication of the components.

2. Basically, lubricants are used to
a. To reduce the wear of the
moving parts in components,
b. Reduce frictional losses
c. Protect components and
equipment from corrosion.

3. Lubricator is added in the form of fine
mist and it is placed near the
equipment to be lubricated.
Lubricator should never be used on -
oil-less compressors.

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nciple of FRL unit

Filter-regulator- 1. This unit combines filter,
lubricant Unit (FRL) regulator and lubricator as
shown in the Figure X. In
basic pneumatic manual) this unit, filter is the first
component followed by
regulator and lubricator.

2. The arrangement of these
components are in such a
way to prevent 1 foreign
matter from causing a
malfunction of the
regulator. Usually,
lubricator is placed last to
avoid oil mist or droplets
from deposited in turns or
valves in the system.

UCTION TO PNEUMATIC SYSTEM 3311

Valve

Valve is a component that receives internal directions which is
electrically and pneumatically to release, stop or discharge ba
switch direction of the air flow.

Types of pneu

Directional control Flow contro
valve (DCV) valve

1 3

2

Non return valve

INTRODU

s in different forms such as manually, mechanically,
ack through air flow. The basic function of valves is to

umatic valves Combination
valve
ol
5

4 3322

Pressure control
valve

UCTION TO PNEUMATIC SYSTEM

Direc

Directional control valve controls the flow of air signals by
cancelling or redirecting signals.

The valve is described by
a. Number of ports or openings (ways): 2-way, 3-way, 4-

b. Methods of actuation of the valve:
i. manually actuated
ii. mechanically actuated
iii. pneumatically actuated
iv. electrically actuated

c. Methods of return actuation: Spring return, air return
control valves are devices which influence the path ta
stream.

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ctional Control Valve (DCV)

y generating,

-way, etc.

directional control valve

n and directional
aken by an air

UCTION TO PNEUMATIC SYSTEM 3333

Directional Control Valve (D

Description of basic symbols of DCV Arrowed line
direction of t
b.
The number of squares
(boxes) referring to number
of switching positions the

valve has

a.
Switching positions of valve
are represented as squares

INTRODU

DCV)

c. d.
Lines drawn at right angles in
e indicates the the squares are known as
the flow paths shut off positions

e.

The lines on the outside of the
box shows connection ports
(inlet and outlet ports)

UCTION TO PNEUMATIC SYSTEM 3344

Methods of actuation of pneum

(Image courtesy of FESTO) man

Ele

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matic directional control valves

roller 3/2 way roller
pilot actuated limit
switch

3/2 way single
piloted DCV

nually actuated 5/2 way double
mechanically actuated solenoid DCV
Pneumatically actuated
3355
ectrically actuated

solenoid

UCTION TO PNEUMATIC SYSTEM

Box 2 (actuation no. of ports in a box / No. of boxes– w
state) 3/ 2– way NC pushbutton with spring
Box 1 (initial position)

2

13

Number of squares (boxes)
Number of ports in one box
method of actuation = push

method of return = spring

(Images courtesy of Library at AutomationDirect.com)

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How to name a DCV?

way, method of actuation, method of return DCV
g return DCV

)=2 Tips:
x=3 ❑ Label or port marking only at the initial
h button
position.
❑ The number of port at each box is the same
❑ The normal position (normally open, NO &

normally closed, NC) need to refer to the port 1

of the initial position. This is only for 3/2 way

DCV

g

UCTION TO PNEUMATIC SYSTEM 3366

DCV Port Labeling

1

Su

Pilot 14 shows air flows from supply 1 to outlet 4 when DCV is
Pilot 12 shows air flows from supply 1 to outlet 2 when DCV is

Sy
(Images cour

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Direct pneumatic actuation (pilot)
Outlet always use even numbers
Supply always use number 1
Exhaust always use odd numbers (3, 5)

upply 3377

s actuated
s actuated

ymbols of DCV
rtesy of FESTO)

UCTION TO PNEUMATIC SYSTEM

Non R

1. A non-return valve allows air flow freely only in one direct
type of valve also known as poppet type valve and is basis
as shuttle valve, quick exhaust valve and one way flow con

2. This is a unidirectional valve where it has two ports: one fo

Check valve ❑ When air flows from port 1, the c
against and come out through po

❑ When air flows from port 2, the b
12

Flow 2
blocked
Spring loaded Sprin
check valve

poppet

Flow

1 allowed

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Return Valve (Check Valve)

tion and do not let the air to flow in opposite direction. This
s for the development of many combined components such
ntrol valve.
or the entry of fluid and the other for the discharge.
check valve allows the air flow by lifting the ball
ort 2.

ball is blocked, thus no air flow is allowed to port 1.

Working principle of a check valve
(Image courtesy of !Original: MionVector: Chris828 at Wikimedia
ng Commons)

Click here to watch
working principle of

check valve

UCTION TO PNEUMATIC SYSTEM 3388

Shuttle Valve (OR Valve)

1. Shuttle valve is a three-ported valve which has two inlets a
poppet will be pushed to port 14 and it is blocked, thus co

2. This valve is also called as OR valve because port 2 able to
either port 12 or 14.

3. A shuttle valve may be used, when the cylinder or valve is
from one another.

Shuttle valve

2

12 14 Cross sectional view of shuttle
(Image courtesy of Prabhakar Purush
Symbol of shuttle valve Own work, CC BY-SA 4.0, at Wikiped

INTRODU

and one outlet. When compressed air enters port 12, the
ompressed air flows from port 12 to port 2.

o produce output, if the compressed air is applied to

to be actuated from two points, which may be remote

Truth table for OR valve

Input 12 Input 14 Output 2
0 0
1 0 0
0 1
1 1 1

valve 1

hothaman – 1
dia)
Click here to watch
working principle of

OR valve

UCTION TO PNEUMATIC SYSTEM 3399

Dual P

1. A dual pressure valve is also a 3-ported valve which has has t
pressurised inputs to allow an output. When compressed air
flow to output. Same thing applies when compressed air is su
B need to supply with compressed air.

2. This valve is also called as AND valve because port X only able
compressed air.

3. Another name for AND function is interlock control. This mea

Dual pressure X
valve A BA

X B Cross sectional view of dual pre
A (Image courtesy of Prabhakar Pur
Own work, CC BY-SA 4.0, at Wikip
Symbol of dual
pressure valve

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Pressure Valve (AND Valve)

two inlets and one outlet. A dual pressure valve requires two
r enters through port A, the spool will lock and no path for the air
upplied through port B. To enable the output X, both port A and

e to produce output if both ports A and B applied with

ans control is possible only when two conditions are satisfied.

X Truth table for AND valve
B Input A Input B Output X

essure valve 111
100
rushothaman – 010
pedia) 000

UCTION TO PNEUMATIC SYSTEM 4400

Quick Exhaust Valve

1. Quick exhaust valve is used to maximize the speed o
atmosphere.

2. In many applications especially with single acting cy
piston speed during retraction of the cylinder to sav

3 (exhaust) ❑ When air flows into port 1,
2 (to cylinder) blocked, thus air flow to po
to actuator

1

❑ When air flows coming out from port 2, port 1
is blocked, thus air is rapidly released through
port 3 (exhaust).

1

(Image courtesy of Fastek USA Quick Exhaust Valve XQ series)

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of piston by exhausting the air rapidly to

ylinders, it is a common practice to increase the
ve the cycle time.

port 3 (exhaust) is Quick exhaust valve
ort 2 which is connected
2 (to
3 (exhaust) cylinder)
1
2 (from
cylinder) 3
(exhaust)

Symbol of quick exhaust
valve

UCTION TO PNEUMATIC SYSTEM 4411

Flow Control Valv

Flow Control Valve is used to control the flow rate of the air flow
actuator becomes slower.

This flow control valve controls air flow in both directions. The ar
adjustable which means the amount of air flow into the actuator

One way flow One-way flow control valve
control valve throttle. Generally, this valv
working pressure line, betw
12
The one-way flow control v
valve.

When air flows from Port 1
blocked. Thus, air flow is co

When air flows from Port 2
air is free flow

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ve (FCV) and One Way FCV

w which cause the speed of Flow control valve
(bidirectional)
rrow indicates that the valve is
r can be adjusted accordingly.

e controls air flow only in one direction which is through the air
ve used to control speed of actuator and is installed in the
ween the final control valve and the cylinder ports.

valve is a combination of a flow control valve and a non return

1 to 2, it will choose the throttle path to flow since check valve is
ontrolled.

2 to 1, it will choose check valve path because it fully open. Thus

UCTION TO PNEUMATIC SYSTEM 4422

Pressure Control Valve

1. Pressure Control valves are used to control pressure in a p
are:
❑ Pressure regulator valve which is used to prevent pre
pressure below a certain pressure,
❑ Pressure limiting valve or pressure relief valve to ens
❑ Pressure sequence valve which generates control sig

INTRODU

pneumatic circuit. Example of pressure control valve

essure fluctuation in the circuit and control the outlet

sure the inlet pressure below a certain pressure and
gnal when the valve reaches a certain pressure limit..

pressure sequence valve 4433

(Image courtesy of FESTECH)

UCTION TO PNEUMATIC SYSTEM

Actu

Linear actuator

Single acting actuator Double acting
actuator

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Types of actuator

uator

Rotary actuator

Air motor Vane motor
Rack and pinion

UCTION TO PNEUMATIC SYSTEM 4444

Linear Actuator – single act

Linear actuator can be classified into two groups;
single acting cylinder and double acting cylinder

1. Single acting cylinder has one air inlet to create a
power stroke in one direction (usually to extend)
and the piston returns to the home position
(retract) by means of spring force.

2. Single acting cylinders are used for applications
such as clamping, marking, ejecting etc.

3. air consumption for single acting cylinder is low
compared with the equivalent size of double
acting cylinder.

Symbol of single acting
cylinder

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ting cylinder vent cylinder rod

air
inlet

Single acting cylinder

Construction of single acting cylinder 4455
(Images courtesy of NPTEL Module 6)

UCTION TO PNEUMATIC SYSTEM