e-book pneumatic_3

Air Dehydration






1 2 3





There are 2 types of Continuous cooler Air Dryer
Air Dehydration: (Aftercoolers) • Absorbance
Continuous cooler a. Air cool – the Drying
(After coolers) cooling process • Adsorption
Air Dryer is done by air Drying
b. Water cool – the • Coolant Drying
cooling process
is done by water














21
INTRODUCTION TO PNEUMATIC SYSTEM 21

Air Dehydration






1 2 3





There are 2 types of Continuous cooler Air Dryer
Air Dehydration: (Aftercoolers) • Absorbance
Continuous cooler a. Air cool – the Drying
(After coolers) cooling process • Adsorption
Air Dryer is done by air Drying
b. Water cool – the • Coolant Drying
cooling process
is done by water














21
INTRODUCTION TO PNEUMATIC SYSTEM 21

Continuous cooler





1. Air will be hot after final 4. Aftercoolers are heat

compression, thus it will exchangers, being either air
deposit water in the pipeline cooled or water cooled units.
when the air cools down. 5. It is generally equipped with a
The water deposited in the water separator with
pipeline is in considerable automatic drainage and
quantities which should be
should be placed close to the
avoided.
compressor.

2. To prevent this, cooler is 3. This process need to be 6. Nowadays, an after-cooler is

used to reduce the done immediately after built into modern
temperature of the compression by forcing the compressors to ease the
compressed air in pneumatic air to aftercooler which process.
systems. This is needed for may help to reduce the
the normal operation of amount of water produced
pneumatic systems. due to condensation.





22
INTRODUCTION TO PNEUMATIC SYSTEM 22

Continuous cooler





1. Air will be hot after final 4. Aftercoolers are heat

compression, thus it will exchangers, being either air
deposit water in the pipeline cooled or water cooled units.
when the air cools down. 5. It is generally equipped with a
The water deposited in the water separator with
pipeline is in considerable automatic drainage and
quantities which should be
should be placed close to the
avoided.
compressor.

2. To prevent this, cooler is 3. This process need to be 6. Nowadays, an after-cooler is

used to reduce the done immediately after built into modern
temperature of the compression by forcing the compressors to ease the
compressed air in pneumatic air to aftercooler which process.
systems. This is needed for may help to reduce the
the normal operation of amount of water produced
pneumatic systems. due to condensation.





22
INTRODUCTION TO PNEUMATIC SYSTEM 22

Continuous Cooler





a. Air cooled b. Water cooled


1. This type of aftercooler uses water to cool down the hot air after
This type of aftercooler uses air to cool down the compressed
air. This air cooled aftercooer consists nest of tubes as shown in compression. The arrangement of the air inlet, air outlet, water inlet
figure (a). Hot air enters the aftercooler through inlet and and water outlet are as shown in the figure (b).
passes by the nest of tubes. The air will be cooled down by 2. The flow of water and air should be opposite direction through the
means of cold air produced by fan assembled in the aftercooler. 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.





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

Click here to watch
a. Air cooled cooler b. Principle of a water cooled aftercooler
b. Water cooled cooler Image courtesy of SMC basic pneumatic manual



23
INTRODUCTION TO PNEUMATIC SYSTEM 23

Continuous Cooler





a. Air cooled b. Water cooled


1. This type of aftercooler uses water to cool down the hot air after
This type of aftercooler uses air to cool down the compressed
air. This air cooled aftercooer consists nest of tubes as shown in compression. The arrangement of the air inlet, air outlet, water inlet
figure (a). Hot air enters the aftercooler through inlet and and water outlet are as shown in the figure (b).
passes by the nest of tubes. The air will be cooled down by 2. The flow of water and air should be opposite direction through the
means of cold air produced by fan assembled in the aftercooler. 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.





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

Click here to watch
a. Air cooled cooler b. Principle of a water cooled aftercooler
b. Water cooled cooler Image courtesy of SMC basic pneumatic manual



23
INTRODUCTION TO PNEUMATIC SYSTEM 23

Air dryer





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.

a b c

3. There are three main types of air dryer Absorption Adsorption Coolant drying
available which operate on an absorption, (deliquescent) (desiccant) (Refrigerant
adsorption or refrigeration process, will be Drying Drying drying)
discussed in this section.

Images courtesy of SMC basic pneumatic manual


24
INTRODUCTION TO PNEUMATIC SYSTEM 24

Air dryer





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.

a b c

3. There are three main types of air dryer Absorption Adsorption Coolant drying
available which operate on an absorption, (deliquescent) (desiccant) (Refrigerant
adsorption or refrigeration process, will be Drying Drying drying)
discussed in this section.

Images courtesy of SMC basic pneumatic manual


24
INTRODUCTION TO PNEUMATIC SYSTEM 24

Air dryer - absorption




a. Absorption (deliquescent) Drying


1. 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.


2. 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.


3. 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
absorption air dryer characteristics, it has to be carefully monitored and filtered
so that small corrosive mists does not enter into the
Image courtesy of SMC basic pneumatic
manual pneumatic system.


25
INTRODUCTION TO PNEUMATIC SYSTEM 25

Air dryer - absorption




a. Absorption (deliquescent) Drying


1. 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.


2. 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.


3. 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
absorption air dryer characteristics, it has to be carefully monitored and filtered
so that small corrosive mists does not enter into the
Image courtesy of SMC basic pneumatic
manual pneumatic system.


25
INTRODUCTION TO PNEUMATIC SYSTEM 25

Air dryer – adsorption




b. Adsorption (desiccant) Drying

1. Desiccant air dryer has different working principle where moisture from the air stream and
onto a desiccant material is adsorbed in a reversible process. Dew points produced is low
which means this is air dryer is a good choice when process require extremely dry air.

2. Silica gel or activated alumina in granular form is used as a chemical in this drying process.
This chemical contained in a vertical chamber to absorb moisture from the compressed air
passing through it. The drying agent is regenerated by drying or heating in a regenerating
column when it becomes saturated as shown in the Figure.

3. Wet compressed air enters to the column 1 through a directional control valve and comes out
as dried air to the outlet port.

4. 10 – 20% of the dry air will pass through the orifice O2 and go to the column 2 to reabsorb
moisture from the desiccant to regenerate it. The regenerating air flow then goes to exhaust.

5. To provide continuous dry air, a timer is used to switch periodically the directional control
valve so that the supply air is allowed alternately to one column.
Principle of the heatless 6. The degree of saturation of the desiccant may be monitored by incorporating a colour
adsorption air dryer indicator.
Image courtesy of SMC basic
pneumatic manual


26
INTRODUCTION TO PNEUMATIC SYSTEM 26

Air dryer – adsorption




b. Adsorption (desiccant) Drying

1. Desiccant air dryer has different working principle where moisture from the air stream and
onto a desiccant material is adsorbed in a reversible process. Dew points produced is low
which means this is air dryer is a good choice when process require extremely dry air.

2. Silica gel or activated alumina in granular form is used as a chemical in this drying process.
This chemical contained in a vertical chamber to absorb moisture from the compressed air
passing through it. The drying agent is regenerated by drying or heating in a regenerating
column when it becomes saturated as shown in the Figure.

3. Wet compressed air enters to the column 1 through a directional control valve and comes out
as dried air to the outlet port.

4. 10 – 20% of the dry air will pass through the orifice O2 and go to the column 2 to reabsorb
moisture from the desiccant to regenerate it. The regenerating air flow then goes to exhaust.

5. To provide continuous dry air, a timer is used to switch periodically the directional control
valve so that the supply air is allowed alternately to one column.
Principle of the heatless 6. The degree of saturation of the desiccant may be monitored by incorporating a colour
adsorption air dryer indicator.
Image courtesy of SMC basic
pneumatic manual


26
INTRODUCTION TO PNEUMATIC SYSTEM 26

Air dryer - coolant drying (refrigerant drying)






1. This method cools the compresses air temperature by
removes water and causing condensation. The accumulated

moisture in liquid form is collected by an internal moisture
separator and sends it to a drain.
2. The air generated by refrigerated dryers typically with

pressure dew points between 35 and 40° F, mostly used in
general plant operations.

3. For critical processes which requires extremely dry air, this
method may not be suitable.
4. This dryer is a mechanical unit consisting a refrigeration

circuit, and two heat exchangers.
5. Refer Figure X for the sequence of the process.




Image courtesy of SMC basic pneumatic manual




27
INTRODUCTION TO PNEUMATIC SYSTEM 27

Air dryer - coolant drying (refrigerant drying)






1. This method cools the compresses air temperature by
removes water and causing condensation. The accumulated

moisture in liquid form is collected by an internal moisture
separator and sends it to a drain.
2. The air generated by refrigerated dryers typically with

pressure dew points between 35 and 40° F, mostly used in
general plant operations.

3. For critical processes which requires extremely dry air, this
method may not be suitable.
4. This dryer is a mechanical unit consisting a refrigeration

circuit, and two heat exchangers.
5. Refer Figure X for the sequence of the process.




Image courtesy of SMC basic pneumatic manual




27
INTRODUCTION TO PNEUMATIC SYSTEM 27

Air Treatment










1 2 3

Atmospheric air consists of dust Besides that, gummy substances To eliminate these contaminants,
and moisture. Dust usually will be may be formed from fine particles further air treatment is required to
removed by the filter fixed at the of carbonised oil, pipe scale and ensure the compressed air is as
intake of the compressor. other foreign matter, such as worn clean as possible to the point of
Meanwhile, moisture condenses sealing material. This can result in use.
out during the continuous cooling injurious effects on pneumatic
and drying process. However, there equipment by increased seal and
will always be some moisture component wear, seal expansion,
which will be carried over. corrosion and sticking valves.













28
INTRODUCTION TO PNEUMATIC SYSTEM 28

Air Treatment










1 2 3

Atmospheric air consists of dust Besides that, gummy substances To eliminate these contaminants,
and moisture. Dust usually will be may be formed from fine particles further air treatment is required to
removed by the filter fixed at the of carbonised oil, pipe scale and ensure the compressed air is as
intake of the compressor. other foreign matter, such as worn clean as possible to the point of
Meanwhile, moisture condenses sealing material. This can result in use.
out during the continuous cooling injurious effects on pneumatic
and drying process. However, there equipment by increased seal and
will always be some moisture component wear, seal expansion,
which will be carried over. corrosion and sticking valves.













28
INTRODUCTION TO PNEUMATIC SYSTEM 28

Air filters





1. To clean the compressed air of all 6. There are three types of air filters
impurities and any condensate it contains.


7. The standard filter is a combined
2. To remove all foreign matter
water separator and filter.



3. To allow dry and clean air flow without 8. A micro-filter is used when contamination by
restriction to regulator and then to the oil vapour is undesirable,
lubricator

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

5. To arrest fine particles and all solid 10. To provide maximum protection for
contaminants from air pneumatic precision measuring devices,
electrostatic spray painting








29
INTRODUCTION TO PNEUMATIC SYSTEM 29

Air filters





1. To clean the compressed air of all 6. There are three types of air filters
impurities and any condensate it contains.


7. The standard filter is a combined
2. To remove all foreign matter
water separator and filter.



3. To allow dry and clean air flow without 8. A micro-filter is used when contamination by
restriction to regulator and then to the oil vapour is undesirable,
lubricator

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

5. To arrest fine particles and all solid 10. To provide maximum protection for
contaminants from air pneumatic precision measuring devices,
electrostatic spray painting








29
INTRODUCTION TO PNEUMATIC SYSTEM 29

Function and principle of FRL unit





1. This component is used to 1. Single filter regulator unit
maintain the specific, precise is a combination of air
pressure required by a particular filter and pressure
application, regardless of the rise regulator which provide a
and fall of line and/or receiver compact space saving
pressure as the compressor cuts unit.
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.
Filter-regulator

Pressure (FR) Unit
Regulator
Images courtesy of SMC basic pneumatic manual


30
INTRODUCTION TO PNEUMATIC SYSTEM 30

Function and principle of FRL unit





1. This component is used to 1. Single filter regulator unit
maintain the specific, precise is a combination of air
pressure required by a particular filter and pressure
application, regardless of the rise regulator which provide a
and fall of line and/or receiver compact space saving
pressure as the compressor cuts unit.
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.
Filter-regulator

Pressure (FR) Unit
Regulator
Images courtesy of SMC basic pneumatic manual


30
INTRODUCTION TO PNEUMATIC SYSTEM 30

Function and principle of FRL unit






1. Pneumatic components usually
consist of internal moving part, thus 1. This unit combines filter,
adding controlled amount of oil regulator and lubricator as
lubricant helps to ensure proper shown in the Figure X. In
lubrication of the components. this unit, filter is the first
component followed by
2. Basically, lubricants are used to regulator and lubricator.
a. To reduce the wear of the
2. The arrangement of these
moving parts in components,
b. Reduce frictional losses components are in such a
c. Protect components and Filter-regulator- way to prevent 1 foreign
equipment from corrosion. lubricant Unit (FRL) matter from causing a
malfunction of the
regulator. Usually,
3. Lubricator is added in the form of fine
mist and it is placed near the lubricator is placed last to
equipment to be lubricated. avoid oil mist or droplets
Lubricator should never be used on - Air Lubricator from deposited in turns or
oil-less compressors. valves in the system.
Images courtesy of SMC basic pneumatic manual



31
INTRODUCTION TO PNEUMATIC SYSTEM 31

Function and principle of FRL unit






1. Pneumatic components usually
consist of internal moving part, thus 1. This unit combines filter,
adding controlled amount of oil regulator and lubricator as
lubricant helps to ensure proper shown in the Figure X. In
lubrication of the components. this unit, filter is the first
component followed by
2. Basically, lubricants are used to regulator and lubricator.
a. To reduce the wear of the
2. The arrangement of these
moving parts in components,
b. Reduce frictional losses components are in such a
c. Protect components and Filter-regulator- way to prevent 1 foreign
equipment from corrosion. lubricant Unit (FRL) matter from causing a
malfunction of the
regulator. Usually,
3. Lubricator is added in the form of fine
mist and it is placed near the lubricator is placed last to
equipment to be lubricated. avoid oil mist or droplets
Lubricator should never be used on - Air Lubricator from deposited in turns or
oil-less compressors. valves in the system.
Images courtesy of SMC basic pneumatic manual



31
INTRODUCTION TO PNEUMATIC SYSTEM 31

Valve



Valve is a component that receives internal directions which is in different forms such as manually, mechanically,
electrically and pneumatically to release, stop or discharge back through air flow. The basic function of valves is to
switch direction of the air flow.


Types of pneumatic valves



Directional control Flow control Combination
valve (DCV) valve valve

1 3 5












2 4

Non return valve Pressure control
valve



32
INTRODUCTION TO PNEUMATIC SYSTEM 32

Valve



Valve is a component that receives internal directions which is in different forms such as manually, mechanically,
electrically and pneumatically to release, stop or discharge back through air flow. The basic function of valves is to
switch direction of the air flow.


Types of pneumatic valves



Directional control Flow control Combination
valve (DCV) valve valve

1 3 5












2 4

Non return valve Pressure control
valve



32
INTRODUCTION TO PNEUMATIC SYSTEM 32

Directional Control Valve (DCV)





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




The valve is described by

a. Number of ports or openings (ways): 2-way, 3-way, 4-way, etc.


b. Methods of actuation of the valve:
i. manually actuated
ii. mechanically actuated
iii. pneumatically actuated directional control valve

iv. electrically actuated


c. Methods of return actuation: Spring return, air return and directional
control valves are devices which influence the path taken by an air
stream.





33
INTRODUCTION TO PNEUMATIC SYSTEM 33

Directional Control Valve (DCV)





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




The valve is described by

a. Number of ports or openings (ways): 2-way, 3-way, 4-way, etc.


b. Methods of actuation of the valve:
i. manually actuated
ii. mechanically actuated
iii. pneumatically actuated directional control valve

iv. electrically actuated


c. Methods of return actuation: Spring return, air return and directional
control valves are devices which influence the path taken by an air
stream.





33
INTRODUCTION TO PNEUMATIC SYSTEM 33

Directional Control Valve (DCV)





Description of basic symbols of DCV

c.
Arrowed line indicates the
direction of the flow paths
b. d.
The number of squares Lines drawn at right angles in

(boxes) referring to number the squares are known as
of switching positions the shut off positions

valve has

e.
a.
Switching positions of valve The lines on the outside of the

are represented as squares box shows connection ports
(inlet and outlet ports)







34
INTRODUCTION TO PNEUMATIC SYSTEM 34

Directional Control Valve (DCV)





Description of basic symbols of DCV

c.
Arrowed line indicates the
direction of the flow paths
b. d.
The number of squares Lines drawn at right angles in

(boxes) referring to number the squares are known as
of switching positions the shut off positions

valve has

e.
a.
Switching positions of valve The lines on the outside of the

are represented as squares box shows connection ports
(inlet and outlet ports)







34
INTRODUCTION TO PNEUMATIC SYSTEM 34

Methods of actuation of pneumatic directional control valves




roller



3/2 way roller
actuated limit
switch

pilot



3/2 way single
piloted DCV




manually actuated
mechanically actuated
5/2 way double

Pneumatically actuated solenoid DCV

Electrically actuated

Image courtesy of FESTO solenoid

35
INTRODUCTION TO PNEUMATIC SYSTEM 35

Methods of actuation of pneumatic directional control valves




roller



3/2 way roller
actuated limit
switch

pilot



3/2 way single
piloted DCV




manually actuated
mechanically actuated
5/2 way double

Pneumatically actuated solenoid DCV

Electrically actuated

Image courtesy of FESTO solenoid

35
INTRODUCTION TO PNEUMATIC SYSTEM 35

How to name a DCV?




no. of ports in a box / No. of boxes– way, method of actuation, method of return DCV


Box 2 (actuation 3/ 2– way NC pushbutton with spring return DCV
state) Box 1 (initial position)

Tips:
 Label or port marking only at the initial
2
position.
 The number of port at each box is the same
 The normal position (normally open, NO &
1 3
normally closed, NC) need to refer to the port 1
of the initial position. This is only for 3/2 way
Number of squares (boxes) = 2
DCV
Number of ports in one box = 3

method of actuation = push button



method of return = spring

Images courtesy of Library at AutomationDirect.com


36
INTRODUCTION TO PNEUMATIC SYSTEM 36

How to name a DCV?




no. of ports in a box / No. of boxes– way, method of actuation, method of return DCV


Box 2 (actuation 3/ 2– way NC pushbutton with spring return DCV
state) Box 1 (initial position)

Tips:
 Label or port marking only at the initial
2
position.
 The number of port at each box is the same
 The normal position (normally open, NO &
1 3
normally closed, NC) need to refer to the port 1
of the initial position. This is only for 3/2 way
Number of squares (boxes) = 2
DCV
Number of ports in one box = 3

method of actuation = push button



method of return = spring

Images courtesy of Library at AutomationDirect.com


36
INTRODUCTION TO PNEUMATIC SYSTEM 36

DCV Port Labeling



Direct pneumatic actuation (pilot)

Outlet always use even numbers


Supply always use number 1

Exhaust always use odd numbers (3, 5)







1
Supply

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





Symbols of DCV
Images courtesy of FESTO



37
INTRODUCTION TO PNEUMATIC SYSTEM 37

DCV Port Labeling



Direct pneumatic actuation (pilot)

Outlet always use even numbers


Supply always use number 1

Exhaust always use odd numbers (3, 5)







1
Supply

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





Symbols of DCV
Images courtesy of FESTO



37
INTRODUCTION TO PNEUMATIC SYSTEM 37

Non Return Valve (Check Valve)




1. A non-return valve allows air flow freely only in one direction and do not let the air to flow in opposite direction. This
type of valve also known as poppet type valve and is basis for the development of many combined components such
as shuttle valve, quick exhaust valve and one way flow control valve.
2. This is a unidirectional valve where it has two ports: one for the entry of fluid and the other for the discharge.

 When air flows from port 1, the check valve allows the air flow by lifting the ball
Check valve
against and come out through port 2.

 When air flows from port 2, the ball is blocked, thus no air flow is allowed to port 1.
1 2
2
Flow Cross sectional view of check
blocked Spring
valve
Spring loaded
check valve Click here to watch
poppet
working principle of
Flow
1 allowed check valve


Image courtesy of !Original: MionVector: Chris828 at Wikimedia Commons


38
INTRODUCTION TO PNEUMATIC SYSTEM 38

Non Return Valve (Check Valve)




1. A non-return valve allows air flow freely only in one direction and do not let the air to flow in opposite direction. This
type of valve also known as poppet type valve and is basis for the development of many combined components such
as shuttle valve, quick exhaust valve and one way flow control valve.
2. This is a unidirectional valve where it has two ports: one for the entry of fluid and the other for the discharge.

 When air flows from port 1, the check valve allows the air flow by lifting the ball
Check valve
against and come out through port 2.

 When air flows from port 2, the ball is blocked, thus no air flow is allowed to port 1.
1 2
2
Flow Cross sectional view of check
blocked Spring
valve
Spring loaded
check valve Click here to watch
poppet
working principle of
Flow
1 allowed check valve


Image courtesy of !Original: MionVector: Chris828 at Wikimedia Commons


38
INTRODUCTION TO PNEUMATIC SYSTEM 38

Shuttle Valve (OR Valve)




1. Shuttle valve is a three-ported valve which has two inlets and one outlet. When compressed air enters port 12, the
poppet will be pushed to port 14 and it is blocked, thus compressed air flows from port 12 to port 2.


2. This valve is also called as OR valve because port 2 able to produce output, if the compressed air is applied to
either port 12 or 14.


3. A shuttle valve may be used, when the cylinder or valve is to be actuated from two points, which may be remote
from one another.
Truth table for OR valve

Input 12 Input 14 Output 2
Shuttle valve
0 0 0

2 1 0 1

0 1 1
12 14
1 1 1
Click here to watch
Cross sectional view of shuttle valve
working principle of
Image courtesy of Prabhakar Purushothaman –
Symbol of shuttle valve OR valve
Own work, CC BY-SA 4.0, at Wikipedia


39
INTRODUCTION TO PNEUMATIC SYSTEM 39

Shuttle Valve (OR Valve)




1. Shuttle valve is a three-ported valve which has two inlets and one outlet. When compressed air enters port 12, the
poppet will be pushed to port 14 and it is blocked, thus compressed air flows from port 12 to port 2.


2. This valve is also called as OR valve because port 2 able to produce output, if the compressed air is applied to
either port 12 or 14.


3. A shuttle valve may be used, when the cylinder or valve is to be actuated from two points, which may be remote
from one another.
Truth table for OR valve

Input 12 Input 14 Output 2
Shuttle valve
0 0 0

2 1 0 1

0 1 1
12 14
1 1 1
Click here to watch
Cross sectional view of shuttle valve
working principle of
Image courtesy of Prabhakar Purushothaman –
Symbol of shuttle valve OR valve
Own work, CC BY-SA 4.0, at Wikipedia


39
INTRODUCTION TO PNEUMATIC SYSTEM 39

Dual Pressure Valve (AND Valve)




1. A dual pressure valve is also a 3-ported valve which has has two inlets and one outlet. A dual pressure valve requires two
pressurised inputs to allow an output. When compressed air enters through port A, the spool will lock and no path for the air
flow to output. Same thing applies when compressed air is supplied through port B. To enable the output X, both port A and
B need to supply with compressed air.


2. This valve is also called as AND valve because port X only able to produce output if both ports A and B applied with
compressed air.


3. Another name for AND function is interlock control. This means control is possible only when two conditions are satisfied.

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


X 1 1 1
A B 1 0 0

0 1 0
Cross sectional view of dual pressure valve
Symbol of dual Image courtesy of Prabhakar Purushothaman – 0 0 0
pressure valve Own work, CC BY-SA 4.0, at Wikipedia


40
INTRODUCTION TO PNEUMATIC SYSTEM 40

Dual Pressure Valve (AND Valve)




1. A dual pressure valve is also a 3-ported valve which has has two inlets and one outlet. A dual pressure valve requires two
pressurised inputs to allow an output. When compressed air enters through port A, the spool will lock and no path for the air
flow to output. Same thing applies when compressed air is supplied through port B. To enable the output X, both port A and
B need to supply with compressed air.


2. This valve is also called as AND valve because port X only able to produce output if both ports A and B applied with
compressed air.


3. Another name for AND function is interlock control. This means control is possible only when two conditions are satisfied.

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


X 1 1 1
A B 1 0 0

0 1 0
Cross sectional view of dual pressure valve
Symbol of dual Image courtesy of Prabhakar Purushothaman – 0 0 0
pressure valve Own work, CC BY-SA 4.0, at Wikipedia


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INTRODUCTION TO PNEUMATIC SYSTEM 40

Quick Exhaust Valve



1. Quick exhaust valve is used to maximize the speed of piston by exhausting the air rapidly to

atmosphere.
2. In many applications especially with single acting cylinders, it is a common practice to increase the
piston speed during retraction of the cylinder to save the cycle time.

3 (exhaust)
 When air flows into port 1, port 3 (exhaust) is
blocked, thus air flow to port 2 which is connected
to actuator Quick exhaust valve
2 (to cylinder)

1 2 (to
3 (exhaust)
cylinder)
 When air flows coming out from port 2, port 1 1
is blocked, thus air is rapidly released through 3
port 3 (exhaust). 2 (from (exhaust)
cylinder)
1 Symbol of quick exhaust
valve

Image courtesy of Fastek USA Quick Exhaust Valve XQ series

41
INTRODUCTION TO PNEUMATIC SYSTEM 41

Quick Exhaust Valve



1. Quick exhaust valve is used to maximize the speed of piston by exhausting the air rapidly to

atmosphere.
2. In many applications especially with single acting cylinders, it is a common practice to increase the
piston speed during retraction of the cylinder to save the cycle time.

3 (exhaust)
 When air flows into port 1, port 3 (exhaust) is
blocked, thus air flow to port 2 which is connected
to actuator Quick exhaust valve
2 (to cylinder)

1 2 (to
3 (exhaust)
cylinder)
 When air flows coming out from port 2, port 1 1
is blocked, thus air is rapidly released through 3
port 3 (exhaust). 2 (from (exhaust)
cylinder)
1 Symbol of quick exhaust
valve

Image courtesy of Fastek USA Quick Exhaust Valve XQ series

41
INTRODUCTION TO PNEUMATIC SYSTEM 41

Flow Control Valve (FCV) and One Way FCV





Flow Control Valve is used to control the flow rate of the air flow which cause the speed of Flow control valve
actuator becomes slower. (bidirectional)


This flow control valve controls air flow in both directions. The arrow indicates that the valve is
adjustable which means the amount of air flow into the actuator can be adjusted accordingly.



One-way flow control valve controls air flow only in one direction which is through the air
throttle. Generally, this valve used to control speed of actuator and is installed in the
working pressure line, between the final control valve and the cylinder ports.
One way flow
control valve The one-way flow control valve is a combination of a flow control valve and a non return
valve.
1 2
When air flows from Port 1 to 2, it will choose the throttle path to flow since check valve is
blocked. Thus, air flow is controlled.


When air flows from Port 2 to 1, it will choose check valve path because it fully open. Thus
air is free flow



42
INTRODUCTION TO PNEUMATIC SYSTEM 42

Flow Control Valve (FCV) and One Way FCV





Flow Control Valve is used to control the flow rate of the air flow which cause the speed of Flow control valve
actuator becomes slower. (bidirectional)


This flow control valve controls air flow in both directions. The arrow indicates that the valve is
adjustable which means the amount of air flow into the actuator can be adjusted accordingly.



One-way flow control valve controls air flow only in one direction which is through the air
throttle. Generally, this valve used to control speed of actuator and is installed in the
working pressure line, between the final control valve and the cylinder ports.
One way flow
control valve The one-way flow control valve is a combination of a flow control valve and a non return
valve.
1 2
When air flows from Port 1 to 2, it will choose the throttle path to flow since check valve is
blocked. Thus, air flow is controlled.


When air flows from Port 2 to 1, it will choose check valve path because it fully open. Thus
air is free flow



42
INTRODUCTION TO PNEUMATIC SYSTEM 42

Pressure Control Valve





1. Pressure Control valves are used to control pressure in a pneumatic circuit. Example of pressure control valve
are:


 Pressure regulator valve which is used to prevent pressure fluctuation in the circuit and control the outlet
pressure below a certain pressure,

 Pressure limiting valve or pressure relief valve to ensure the inlet pressure below a certain pressure and


 Pressure sequence valve which generates control signal when the valve reaches a certain pressure limit..











pressure sequence valve



Image courtesy of FESTECH




43
INTRODUCTION TO PNEUMATIC SYSTEM 43

Pressure Control Valve





1. Pressure Control valves are used to control pressure in a pneumatic circuit. Example of pressure control valve
are:


 Pressure regulator valve which is used to prevent pressure fluctuation in the circuit and control the outlet
pressure below a certain pressure,

 Pressure limiting valve or pressure relief valve to ensure the inlet pressure below a certain pressure and


 Pressure sequence valve which generates control signal when the valve reaches a certain pressure limit..











pressure sequence valve



Image courtesy of FESTECH




43
INTRODUCTION TO PNEUMATIC SYSTEM 43

Types of actuator








Actuator






Linear actuator Rotary actuator





Double acting
Single acting actuator Air motor Vane motor
actuator




Rack and pinion










44
INTRODUCTION TO PNEUMATIC SYSTEM 44

Types of actuator








Actuator






Linear actuator Rotary actuator





Double acting
Single acting actuator Air motor Vane motor
actuator




Rack and pinion










44
INTRODUCTION TO PNEUMATIC SYSTEM 44

Linear Actuator



Linear actuator can be classified into two groups; single acting cylinder and double acting cylinder
air
inlet vent cylinder rod
Single 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. Single acting cylinder



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 Symbol of single acting
acting cylinder. cylinder

Construction of single acting cylinder
Images courtesy of NPTEL Module 6

45
INTRODUCTION TO PNEUMATIC SYSTEM 45

Linear Actuator



Linear actuator can be classified into two groups; single acting cylinder and double acting cylinder
air
inlet vent cylinder rod
Single 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. Single acting cylinder



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 Symbol of single acting
acting cylinder. cylinder

Construction of single acting cylinder
Images courtesy of NPTEL Module 6

45
INTRODUCTION TO PNEUMATIC SYSTEM 45