Applications of Hydraulics&Pneumatics : Session 10

8/3/2019 Applications of Hydraulics&Pneumatics : Session 10

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1

10pplications of

Hydraulic Pneumatics&By: Alireza Safikhani

History of Pneumatics

The term "The term "PneuPneu" is Greek for breath or wind. The modern" is Greek for breath or wind. The modern

term "Pneumatics" refers to the study of air movement.term "Pneumatics" refers to the study of air movement.

Early man learned to work with wind as theyEarly man learned to work with wind as they

used sails to propel their boats. Today peopleused sails to propel their boats. Today people

still utilize air/wind for windsurfing, sailing andstill utilize air/wind for windsurfing, sailing andhand gliding.hand gliding.


Windmil ls were used to pump water andWindmil ls were used to pump water and

grind grain and have been in existencegrind grain and have been in existence

for a number centuries.for a number centuries.



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Development . . .

ToTo--dayday pneumatics play an important role inpneumatics play an important role in

automation. Therefore machines which were onceautomation. Therefore machines which were onceoperated manually are being replaced byoperated manually are being replaced by

pneumatic actuators.pneumatic actuators.

This is a modern dayThis is a modern dayexample of an airexample of an air

brake in a truckbrake in a truck

Areas of use

IndustryIndustry

TradeTrade Rail transportRail transport

Air transportAir transport

Motor vehiclesMotor vehicles

MiningMining

ShippingShipping

MedicineMedicine

ConstructionConstruction

DefenceDefence

Application areas

Clamping toolsClamping tools

Feed unitsFeed units Lifting and loweringLifting and lowering

Opening and closingOpening and closing

SwivelingSwiveling

Pneumatic pressesPneumatic presses

Door controlDoor control

Rotary transfer tablesRotary transfer tables Tool loadingTool loading

1- Generation of linear motion

TurntablesTurntables

Industrial robotsIndustrial robots Welding clampsWelding clamps

TackersTackers

EjectorsEjectors

VibratorsVibrators

TransportationTransportation

MovementMovement

BrakingBraking

Generation of linear motion . . .


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Generation of linear motion . . .Generation of linear motion . . .

Screw driversScrew drivers

GrindersGrinders

Thread cuttersThread cutters

DrillsDrills

ShearsShears

NibblersNibblers

2- Generation of rotary motion Generation of rotary motion . . .


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SequenceSequence controlcontrol

MonitoringMonitoring

ProtectingProtecting

LockingLocking

CountingCounting

DecelerationDeceleration

StorageStorage

ScanningScanning

3- Applications in control

Workshop airWorkshop air

Paint sprayingPaint spraying

Pneumatic postPneumatic post

ExtinguishersExtinguishers

Monitoring unitsMonitoring units

4- Others

Others . . . Properties of pneumatics

High power density of drivesHigh power density of drives

Low power to weight ratio at high speedsLow power to weight ratio at high speeds

Innate explosion proofInnate explosion proof Insensitive to external influences such as high and lowInsensitive to external influences such as high and low

temperatures, dirt, mechanical vibration, humidity andtemperatures, dirt, mechanical vibration, humidity and

electrical noiseelectrical noise

Drives can be overloaded until standstill is reachesDrives can be overloaded until standstill is reaches

No return piping necessaryNo return piping necessary

Simple conversion of energy into rotary, as well as linearSimple conversion of energy into rotary, as well as linear

motionmotion


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Properties of pneumatics . . .

Speed and force easily andSpeed and force easily and continuously controllable over acontinuously controllable over a

wide rangewide range

Energy can be transmitted over long distancesEnergy can be transmitted over long distances

Simple maintenance of devices due to uncomplicatedSimple maintenance of devices due to uncomplicated

constructionconstruction

High reliability, operational dependability and long life ofHigh reliability, operational dependability and long life of

drives and control devicesdrives and control devices

Functionally reliable even underFunctionally reliable even under adversadversee operatingoperating

conditionsconditions Economical application in control equipment and drivesEconomical application in control equipment and drives

Disadvantages of pneumatics . . .

Preparation necessaryPreparation necessary

Stable Speeds not possible due to compressibility ofStable Speeds not possible due to compressibility ofairair

High energy costsHigh energy costs

Efficiency reduced by leakageEfficiency reduced by leakage

Transmission of Energy by Pneumatics

CylindersCylinders

MotorsMotors ModulesModules

1- Drives 2- Energy control

Directional valvesDirectional valves

Flow control valvesFlow control valves Isolating valvesIsolating valves

Pressure valvesPressure valves3- Control

Manual controlManual control

Electrical controlElectrical control

Electronic controlElectronic control Pneumatic controlPneumatic control

DistributionDistribution

GenerationGeneration CompressionCompression

4- Energy supply

Control and device engineering

Are Unthinkable nowadays

Without Pneumatics


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Composition of air

The air we breathe isThe air we breathe is

springy, squashy andspringy, squashy and

fluid in substancefluid in substance

We take it for grantedWe take it for granted

that w herever there isthat wherever there is

space it will be fil ledspace it will be filled

with airwith air

Air is composed mainlyAir is composed ma inly

of nitrogen and oxygenof nitrogen and oxygen

Composition by Volume

Nitrogen 78.09% N2Oxygen 20.95% O2Argon 0.93% ArOthers 0.03%

Atmospheric pressure

The atmosphericThe atmospheric

pressure is caused bypressure is caused by

the weight of air abovethe weight of air aboveusus

It gets less as we climbIt gets less as we climb

a mountain, more asa mountain, more as

we descend into a minewe descend into a mine

The pressure value isThe pressure value is

also influenced byalso influenced by

changing weatherchanging weatherconditionsconditions

Standard Atmosphere

A standard atmosphere is defined byA standard atm osphere is defined by

The Interna tional Civil Aviation Organisation.The International Civil Aviation Organisation.

The pressure and temperature at sea level isThe pressure and temperature at sea level is

1013.251013.25 mil l imill i bar absolute and 288 K (15bar absolute and 288 K (15 OOC)C)

1013.25 m bar

ISO Atmospheres

ISO Recommendation R 554ISO Recommendation R 554

Standard Atmospheres for conditioning and/or testing ofStandard Atmospheres for conditioning and/ or testing ofmaterial, components or equipmentmaterial, components or equipment

2020OO

C, 65% RH, 860 to 1060 mbarC, 65% RH, 860 to 1060 mbar 2727OOC, 65% RH, 860 to 1060 mbarC, 65% RH, 860 to 1060 mbar

2323OOC, 50% RH, 860 to 1060 mbarC, 50% RH, 860 to 1060 mbar

TolerancesTolerances 22OOCC 5%RH5%RH

Reduced tolerancesReduced tolerances 11OOCC 2%RH2%RH Standard Reference Atmosphere to which tests made at otherStandard Reference Atmosphere to which tests made at other

atmospheres can be correctedatmospheres can be corrected

2020OOC, 65% RH, 1013 mbarC, 65% RH, 1013 mbarNo qualifying altitude is given as it is concerned only with theNo qualifying altitude is given as it is concerned only with theeffect of temperature, humidity and pressureeffect of temperature, humidity and p ressure


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Atmospheric pressure

We see values ofWe see values of

atmospheric pressureatmospheric pressure

on a weather mapon a weather map

The lines called isobarsThe lines called isobars

show contours ofshow contours of

pressure inpressure in mill ibarmill ibar

These help predict theThese help predict the

wind direction andwind direction and

forceforce

LOW

1015 mb

1012 mb

1008 mb

1000 mb

996 mb

Mercury barometer

Atmospheric pressure canAtmospheric pressure can

be measured as the heightbe measured as the height

of a l iquid column in aof a l iquid column in avacuumvacuum

760 mm Hg = 1013.9760 mm Hg = 1013.9

mil l ibarmil l ibar approximatelyapproximately

A w ater barometer tubeA water barom eter tube

would be over 10 metreswould be over 10 metres

long. Hg = 13.6 times thelong. Hg = 13.6 times the

density of Hdensity of H 22OO

For vacuum measurement 1For vacuum measurement 1

mm Hg = 1mm Hg = 1 TorrTorr760760 TorrTorr = nil vacuum= nil vacuum

00 TorrTorr = ful l vacuum= full vacuum

760 mm Hg

Atmosphere and vacuum

The power ofThe power of


is apparent in industryis apparent in industry

where pick and placewhere pick and placesuction cups andsuction cups and

vacuum formingvacuum forming

machines are usedmachines are used

Air is removed fromAir is removed from

one side allowingone side allowing


on the other to do theon the other to do theworkwork

Industrial compressed air

Pressures are inPressures are inbar gbar g

gauge pressure ( the valuegauge pressure ( the value

above atmosphere)above atmosphere)

Zero gauge pressure isZero gauge pressure is


Absolute pressures are usedAbsolute pressures are used

for calculationsfor calculations

Pa = Pg + atmospherePa = Pg + atm osphere

For quick calculationsFor quick calculations

assume 1 atmosphere isassume 1 atmosphere is

1000 mbar1000 mbar

For standard calculations 1For standard calculations 1

atmosphere isatmosphere is1013 mbar1013 mbar

Lowrange

TypicalIndustrialrange

01

2

3

4

5

6

7

8

9

10

1112

13

14

15

16

17

0

1

2

3

4

5

6

7

8

9

1011

12

13

14

15

16

Absolutepressurebara

Gaugepressurebar

g

Full vacuumAtmosphere

ExtendedIndustrialrange


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Pressure

11 bar = 100000 N/ mbar = 100000 N/ m 22

((NewtonsNewtons per squareper square

metre)metre)

1 bar = 10 N/ cm1 bar = 10 N/ cm22

For measuring lowerpressures the millibar

(mbar) is used

1000 mbar = 1 bar

For measurements inpounds per square inch(psi)1 psi = 68.95mbar14.5 psi = 1bar

Pressure units

There are many uni ts of pressure measurement.There are many un its of pressure measurement.

Some of these and their equivalents are listedSome of these and their equivalents are listed

below.below.

1 bar = 100000 N/ m1 bar = 100000 N/ m 22

1 bar = 1001 bar = 100 kPakPa

1 bar = 14 .501 bar = 14.50 psipsi

1 bar =1 bar = 10197 kgf/ m10197 kgf/ m 22

1 mm Hg = 1.334 mbar approx.1 mm Hg = 1.334 mbar approx.

1 mm H1 mm H 22O = 0.0979 mbar approx.O = 0.0979 mbar approx.

11 TorrTorr = 1mm Hg abs (for vacuum)= 1mmHg abs (for vacuum)

Pressure and force

Compressed air exerts aCompressed air exerts a

force of constant value toforce of constant value to

every internal contactevery internal contact

surface of the pressuresurface of the pressure

containing equipment.containing equipment.

Liquid in a vessel wil l beLiquid in a vessel wil l be

pressurised and transmitpressurised and transmit

this forcethis force

For every bar of gaugeFor every bar of gauge

pressure, 10pressure, 10 NewtonsNewtons ar eare

exerted uniformly over eachexerted uniformly over each

square centimetre.square centimetre.

Pressure and force

The thrust developed by aThe thrust developed by a

piston due to air pressure ispiston due to air pressure is

the effective area m ultipl iedthe effective area multipl ied

by the pressureby the pressure

Thrust =D2

40

PNewtons

D mm

P bar

Where

D= The bore of a cylinder in mmP= The pressure in bar.We require an answer in Newtons

1bar = 100000 N/m2

D2

is therefore divided by 1000000 to bringit to m2 and P is multiplied by 100000 tobring it to N/m2. The result is a divisionby 10 shown in the product 40 above


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Pressure and force

The force contained by aThe force contained by a

cylinder barrel is thecylinder barrel is the

projected area multipl ied byprojected area multipl ied bythe pressurethe pressurel

D

Force =D . l . P

10

Newtons

WhereD= the cylinder bore mm

l = length of pressurised chamber mmP= the pressure in bar

Pressure and force

If both ports of a doubleIf both ports of a double

acting cyl inder areacting cyl inder are

connected to the sameconnected to the samepressure source, thepressure source, the

cylinder wil l move out duecylinder wil l move out due

to the difference in areasto the difference in areas

either side of the pistoneither side of the piston

If a through rod cyl inder isIf a t hrough rod cyl inder is

applied in this way it w il l beapplied in this way it wil l be

in balance and not move inin balance and not move in

either directioneither direction

Pressure and force

In a balanced spool valve the pressure acting at any port wil lIn a balanced spool valve the pressure acting at any port w il l

not cause the spool to move because the areas to the left andnot cause the spool to move because the areas to the left and

right are equal and wil l produce equal and opposite forcesright are equal and wil l produce equal and opposite forces

P1 and P 2 are the supply and exhaust pressuresP1 and P 2 are the supply and exhaust pressures

P1 P2

Pressure and force

In a balanced spool valve the pressure acting at any port w il lIn a balanced spool valve the pressure acting at any port wil l

not cause the spool to move because the areas to the left andnot cause the spool to move because the areas to the left and

right are equal and wil l produce equal and opposite forcesright are equal and w il l produce equal and opposite forces

P1 and P 2 are the supply and exhaust pressuresP1 and P 2 are the supply and exhaust pressures

P1P2


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Low temperature drier

For applications requiringFor applications requiring

air supplies with m ore thanair supplies with m ore than

water droplets removedwat er droplets removed A low temperature dryerA low temperature dryer

can process compressed aircan process compressed air

to a dew point of just aboveto a dew point of just above

freezingfreezing

A low cost and convenientA low cost and convenient

device to usedevice to use

Bypass Valve

Humid air in

Dry air out

Drain

Low temperature drier

Humid air enters the firstHumid air enters the first

heat exchanger where it isheat exchanger where it is

cooled by the dry air goingcooled by the dry air going

ou tou t

The air enters the secondThe air enters the second

heat exchanger where it isheat exchanger where it is

refrigerat ed. It is cooled torefrigerat ed. It is cooled to

temperatures between + 2temperatures between + 2

and + 5and + 5 CC

The condensate is collectedThe condensate is collected

and drained awayand drained away

As the dry refrigerated airAs the dry refriger ated airleaves it is warmed by theleaves it is warmed by the

incoming humid airincoming humid air

M

Dry air out

Humid air in

Drain

Refrigerationplant

Low temperature drying

If 1 cubic metre of ful ly saturated compressed air ( 100 % RHIf 1 cubic metre of ful ly saturated compressed air ( 100 % RH

) is cooled to just above freezing point, approximately 75%) is cooled to just above freezing point, approximately 75%

of the vapour content wil l be condensed out. When it isof the vapour content wil l be condensed out. When it is

warmed back to 20warmed back to 20 OOC it wil l be dried to nearly 25% RHC it wil l be dried to nearly 25% RH

-40

-20

0 10 20 30 40 50

0

20

40

Grams of water vapour / cubic metre of air g/m360 70 80

TemperatureCelsius

25% RH 50% RH 100% RH

If 1 cubic metre of ful ly saturated compressed air ( 100 % RHIf 1 cubic metre of fully saturated compressed air ( 100 % RH



warmed back to 20warm ed back to 20OOC it wil l be dried to nearly 25% RHC it wil l be dried to nearly 25% RH

-40

-20

0 10 20 30 40 50

0

20

40


TemperatureCelsius

25% RH 50% RH 100% RH

Low temperature drying


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If 1 cubic metre of ful ly saturated compressed air ( 100 % RHIf 1 cubic metre of ful ly saturated compressed air ( 100 % RH



warmed back to 20warmed back to 20 OOC it wil l be dried to nearly 25% RHC it wil l be dried to nearly 25% RH

-40

-20

0 10 20 30 40 50

0

20

40


T

emperatureCelsius

25% RH 50% RH 100% RH

Low temperature drying Flow units

Flow is measured as aFlow is measured as avolume of free air per unitvolume of free air per unitof timeof time

Popular units are :Popular units are :

Litres or cubicLitres or cubicdecimetres per seconddecimetres per secondl/ sl/ sor dmor dm33/ s/ s

Cubic metres per minuteCubic metres per minutemm33/ m/ m

Standard cubic feet perStandard cubic feet perminute (same as cubicminute (same as cubicfeet of free air)feet of free air) scfmscfm

1 m1 m 33

/ m = 35.31/ m = 35.31

scfmscfm

1 dm1 dm 33/s = 2 .1/s = 2.1 scfmscfm

11 scfmscfm = 0.472= 0.472 l/ sl/ s

11 scfmscfm = 0.0283 m= 0.0283 m 33/min/min

1 cubic metreor 1000 dm3

1 litre or

cubic decimetre

1 cubic foot

Free air

Litres actual volume

All volumes are 1 Litre of free air

1 2 4 16

0

1.0

0.5

0.25

0.125

0.0625

8

Flow figures are quoted aslitres of free air per unit oftime

N litres of free air at anypressure will take up aspace of N litres whenreleased to atmosphere (forthis example assumed as1000mbar)

The actual volume taken upby 1litre of free air is shownat various absolute and

gauge pressures

bar a

bar g 0 1 3 157

Air filtration quality

ISO 8573ISO 8573 --1 Compressed air1 Compressed air

for general usefor general use

Part 1 Contaminants andPart 1 Contaminants and

quality classesquality classes

Allowable levels ofAllowable levels of

contamination are given acontamination are given a

quality class numberquality class number

Specified according to theSpecified according to the

levels of theselevels of these

contaminants:contaminants:

solid particlessolid particles

waterwater

oi loi l

An air quality class is statedAn air quality class is stated

as three air quality numbersas three air quality numbers

e.g. 1.7.1e.g. 1.7.1

solidssolids 0.10.1 m maxm max

and 0.1 mg/ mand 0.1 mg/ m 33 maxmax

water nwater not specifiedot specified

0.01 mg/ m0.01 mg/ m 33 maxmax


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Compressed air quality

Class

particlesize max

m

Solids

concentration

mg/m3

Water

Max PressureDew point OC

Oil

concentrationmg/m3

1 0.1 0.1 70 0.012 1 1 40 0.13 5 5 20 14 15 8 + 3 5

5 40 10 + 7 25

6 - - + 10 -

7 - - Not Specified -

maximum

Pressure dew point is the temperature towhich compressed air must be cooled beforewater vapour in the air starts to condense intowater particles

ISO 8573-1

70 Applied Circuits

Applications of Hydraulics&Pneumatics : Session 10

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