%silltr
BASIC
NEUMATICS
Indianapolis,
IN 46556
Rev.0100
Copyright1997
Pori # SttlCT-Pl-IX
DO NOT COPYWITT{OUTWRITTENPERMISSION
TAgLE
l INTRODUCTION
do?
Whatcan Pneumatics
Propertiesot Compr6ss6dAir
oF cot{tENts
Mainlinefiller
Air Dislribution
DeadEnd Line
RingMain
SecondaryLines
AutomalicDrains
SizingCompressedAir Mains
Materialslor Piping
StandardGas PiPe(SGP)
Table4.21 PipeSizeSp€cificalion
StainlesssteelPipes
CopperTube
RubberTube('Air Hose")
Plastictubing
1
1
2
SYSTEM
2 THEBASICPNEUMATIC
the air Productionand dislributionsvstem e
4
The Air Consumption
Syslem
AIRTHEORY
3 COMPRESSED
Units
Pressur€
Prooertiesof Gases
lsothermicchange(Boyle'sLaw)
lsobaricchange
CharlesLaw
Lawof Gay Lussac
lsochoricchange
Adiabatic(lsentropic)change
StandardVolume
Flow
Bernoulli'sEquation
Air Humidity
Relativehumidity
Pressur€and Flow
Useof the diagram:
Formulae:
6
6
I
10
10
11
11
11
11
12
12
12
12
12
13
15
16
16
'
ANDDISTRIBUTIONI9
4 AIRCOMPRESSION
Compressors
19
Reciprocating
Compressors
19
SinglestagePistonCompressor
19
Two stagePistonCompressor
19
Diaphragmcompressor
20
Rotarycompressors
21
Rotaryslidingvanecompressor
21
Screwcompressor
21
Compressorrating
21
VolumetricEtficiency
22
Thermaland OverallEfficiency
22
CompressorAccessories
23
Air receiver
23
Sizinga receiver
23
lnletfilter
23
Air Dehydralion
24
Altercoolers
24
Air cooled
24
Watercooled
24
Air dryers
26
Drying
Absorption(deliquescent)
26
Adsorption(dEsiccanl)Drying
27
Hetrigerant
drying
28
-
29
29
30
JU
21
?1
35
.tc
?F
AE
36
36
5 AIRTBEATMENT
Fillering
StandardFilter
Air Ouality
Filteringlevels
PressureFlegulation
StandardBegulator
PilotOperatedRegulator
Filter-Regulator
Characteristics
Sizingol Regulatorsand Filters
CompressodAir Lubrication
Proportional
Lubricators
F.R.LUnits
Siz€and lnstallation
38
38
38
40
40
42
42
M
45
45
46
46
46
48
rt8
6 ACTUATORS
Lin€arCylinders
SingleActingCylinder
DoubleActingCylinder
CylinderConstruction
Cushioning
SpecialCylinderOptions
DoubleRod
Non BotalingBod
Twin Rod
FlatCylinder
TandemCylinder
MultiPositionCylinder
CylinderMounting
FloatingJoints
BucklingStrength
CylinderSizing
CylinderForce
Th€oreticalForce
BequkedForce
49
49
49
49
50
-
9U
51
51
51
52
52
52
53
54
54
55
55
55
J5
57
TABLE oF Co
Load Fatio
SpeedControl
Air Flowand Consumption
RotaryActuators
Rackand PinionType
VaneType RotaryActuators:
SizingRotaryActuato|s
Torqueand Inertia
Sp€cialActuators
LockingCylinder
Rodlessrylinders
Wilh magneticcoupling,unguided
Guidedtypes,with magneticcoupling
Guided,with mechanicalcoupling
SlideUnits
HollowRod Cylinder
linearRotatingCylinder
Air Chuck(GrippeO
7 DIRECTIONAL
CONTROLVALVES
ValveFunctions
Symbol
Portldentification
Monostableand bistable
ValveTypes
PoppetValves
SlidingValvss
SpoolValves
Elastomerseal
MetalSeal
PlaneSlid6Valve
RotaryValves
ValveOperation
Mechanicaloperation
Carewhen usingRollerLevers
ManualOperation
Air Operation.
PilotedOperation.
SolenoidOperation
DirectPiping
Manifolds
Sub Bas€s
MultipleSub Bases
GangedSub Bases
ValveSizing
Indicationsfor Flowcapacity
Orificesin seriesconnection
Flow capacity of lubes
Valveswith Cylinders
AuxiliaryValves
TENTS
Non-RetumValves
SpeedConlrollers
ShutlleValve
QuickExhauslValves
58
59
60
63
63
63
63
63
66
66
66
66
67
67
68
68
69
69
88
88
88
90
91
8 BAS|CCIBCUITS
91
lntroduction
ol
FlowAmplilication
91
SignalInversion
o,
Selec{ion
MemoryFunction
92
Timetunctions
93
Delayedswitchingon
94
Delayedswitchingotf
94
Pulseon switchingon
94
Pulseon releasinga valve
95
CylinderControl
96
ManualControl
96
SingleActingCylinder
96
DirectOperationand Sp€edControl 96
IntedockAND Function
97
InverseODeration:
NOT Function
97
DoubleactingCylinder
98
Direct Control
98
Holdingthe end positions
98
DetectingCylinderPositions
99
oo
AutomaticFetum
RepsatingStrokes
101
Control
S€quenc€
101
Howto describea sequ€noe
101
Nomenclature
101
Sequenceof lwo Cylinders
102
103
Singl€Cycle/ R€peatingCycle
OpposingCommands
104
with a Pulse
Elimination
104
Clamping:PressureControl
104
CascadeSystem
105
70
70
70
71
71
71
72
73
73
73
74
74
75
76
76
78
76
T7
78
79
80
80
81
81
81
82
82
83
84
85
88
APPENDIX
Symbols
Air Tr€atmentEquipment
Actuators
Valves
Circuits
BasicRules
RestPosition
CircuitLayout
Nomenclature
SampleDiagrams
-
-
108
108
108
109
109
111
111
111
112
113
115
P N E U T , A T I CT E C H N O L O G Y
INTRODUCTION
A fluidpowersystemis one thal transmitsand controlsenergythroughthe useof pressurizedliquidor gas'
In Pneumatics.
this mediais air.This of coursecomesfromthe atmosphereand is reducedin volumeby
thus incr€asing
its pressure.Compressedair is mainlyusedto do workby actingon a pistonor
compression,
vane-- producingsomeusefulmotiontor instance.
Whilemanytacetsof industryusecompressedair,the generalfieldof IndustrialPneumaticsis considered
here.
The corect use ol pn€umatic
controlrequiresan adeguateknowledgeof pneumaticcomponentsand their
of lh€
functionlo ensuretheirintegralionintoan etficienlworkingsysiem.lt is alwaysthe r€sponsibility
d€signerto certifysafetyin all conditions-- includinga failedcondition.As with any otheronergysource,
compressedair can causeharmif not properlyapplied.
sequenceror olherlogiccontrollermay be currenlly
Althoughelectroniccontrolusinga programmable
speciliedit is stillnecessarylo knowthe basicfunctionof lhE pneumaticcomponents.
This bookdealswiththe t9chnologyof the componentsin controlsystems,describingtypesand design
and introducesthe
teaturesof air treatmontequipment,actuatorsand vafues,methodsof inlerconneclion
pneumatic
basic
circuits.
W H A T C A N P N E U M A T I C SD O ?
The applications
tor compressedair are limitless,lrom the optician'sgentleuseof low pressureair to test
fluidpressurein the humaneyeball,the multiplicityol linearand rotarymotionson roboticprocessmachines,
Ij to the hightorcesrequiredtor pneumaticpressesand concretebreakingpneumaticdrills.
'
and varietyof pneumaticcontrolat work,in a
The shortlist belowseNesonlyto indicateth€v€rsatility
expandingindustry.
continuously
. Operationof systemvalvesfor air,wateror chemicals
. Operationof heavy or hot doors
. Unloadingof hopp€rsin building,steelmaking,miningand chemicalindustries
. Rammingand tampingin concreteand asphaltlaying
. Littingand movingin slab moldingmachines
. Cropsprayingand operationot othertractorequipment
. Spraypainting
. Holdingand movingin woodworkingandfumituremaking
. Holdingin jigs and fixturesin assemblymachineryand machinetools
. Holdingtor gluing,heatsEalingor weldingplastics
. Holdingtor brazingor wolding
. Formingoperationsof bending,drawingand flattening
. Spotweldingmachines
. Riveting
. Op€rationof guillotineblades
. Bottlingand fillingmachines
. Woodworkingmachinerydrivesand teeds
. T€strigs
. Machinetool,workor toolfeeding
. Componentand materialconvevortransfer
DO NOT COPYWTTHOUTWRITTENPERMISSION
P
EU ATtc TEcHt{oLocY
. Pn€umalicrobots
. Autogauging
. Air separationand vacuumlifiingot thin sheots
. Dentaldrills
. and so muchmore...newapplicationsars developeddaily
PROPERTIES
OF COMPRESSED
AIR
Someimportant
reasons
torthewideuseofcompressed
ahinindustry
arai
Avallablllty
Mostfacto.iesand industrialplantshavea compressodair supplyin workingareas,and portable
compressorscan servemor€remolesituations.
Storag6
It is easilystoredin largevolumesif required.
Slmpllclty ot Deslgn and Control
Pneumaticcomponentsare of simpledesignand are easilyfittedto provideextensiveautomated
systemswithcomparatively
simplecontrol.
Cholce of Movement
ll offersboth linearmovementand angularrotationwith simpleand continuouslyvariabl€operational
sDeeds.
Economy
Installation
is of relativelylow cost due to modestcomponentcost.Thereis also a low maintenance
cosl due to long life withoutservice.
Rellablllty
Pneumaliccomponentshavsa longworkinglife resultingin highsystemreliability.
Reslstanceto Envlronment
It is largelyunatf€ctedin the hightemperature,
dustyand corrosiveatmospheresin whichother
systemsmay fail.
Environmentally
Clean
It is cleanandwithproperexhaustairtr€atTent
canbeinstalled
to cleanroomstandards.
Satety
It is nota fire hazardin highriskareas,andthe systemis unattectedby ovedoadas ackratorssimply
stallor slip.Pneumatic
actuators
do notproduceheat-- oth6rthanfriction.
DO NOT COPYWITHOUT WRITTEN PERMISSION
P N E U l , t A T t cT E c H N o L o c Y
SYSTEM
2 T H E B A S I CP N E U M A T I C
Pneumaticcylinders!rotaryactuatorsand air motorsprovidethe forceand movemenlof moslpneumatic
controlsystems,to hold,move,form,and proc€ssmatetial.
are requiredi.e. air serviceunilslo
To operateand controltheseacluators,olher pneumaticcomponents
pr€par€lh€compressedair and valvesto controllhe pressur€,tlowand directionof movementof lhe
actualors.
A basicpneumaticsystem,shownin tig 2.1, consislsof two mainsections:
. The Air Productionand DistribulionSystem
. The Air ConsumingSystem
Fig. 2.1 Th€BasicPn€umatic
System.
Th€componentpartsand theirmaintunctionsare:
NY S T E M
H E A I B P R O D U C T I OA
NN D D I S T R I B U T I OS
O corpr"""o,
pressureis compressedand deliv€redat a higherpressureto the
Air takenin at atmospheric
pneumaticsystem.lt thustransformsmechanical€nergyintopneumaticenergy.
Electrlc Motor
Suppliesthe mechanicalpowerto the comprossor.lt transformselectricalenergyinto m€chanical
€n€rgy.
@ PressureSwltch
pressure
Controls
theelectricmotorbysensing
thepressur€
in thetank.lt is setto a maximum
at
pressure
whichit stopsthemotor,anda minimum
atwhichit restarts
it.
@ checkvalve
Letsthe compressedair fromth€compressorintoth6 tankand preventsit leakingbackwhenthe
compressoris stopped.
DO NOT COPYWTTHOUTWRITTENPERMISSION
-.t-
P N E U U A T t cT € c H N o L o c Y
@ranr
Stor€sthe compr€ss€d
air. lts size is dofin€dby the capacityof the compressor.The
largerthe volume,th€ longerth€interualsbetweencompr€ssorruns.Mostsystems
shouldbe designedtor a 50o/o
dutycycle,providingat least2x syslemdemandin storage.
@ Prcssure
cauge
Indicatesthe TEnkPressure.
@ AutoDrain
Drainsall the walercondensingin the tankwithoutsupervision.
@ s"hty v"tr"
Blowscompressedair otf if th€pressurein the tank shouldriseabovethe allowed
pressure.
@ Retrlgerated
Alr Dryer
Coolsthe compressedair to a tew degreesabovefreezingpointand condensesmostof the air
humidity.This avoidshavingwaterin the downstrcamsystem.This devicemusl be pr€cededby an
aftercooler(notshownin the simpledrawing)and not directlyinline withthe compressoror it will be
over-tax€d.ldeally,inletair temperatureshouldbe ambientor roomtemperature.
@ unerlner
Beingin the mainpipe,this filtermusl havea minimalpressuredropand the capabilityof oil mist
r€moval.lt helpsto keepthe linetreefrom dust,wat€r,and oil.
THE AIR CONSUMPTION
SYSTEM
(D lttt"t*ott
Forconsumption,
airis takenofftromthetopof themainpipeto allowoccasional
cudensateto slayin
th€mainpipe.Wh€nit reach€s
a lowpointa watertake-oftfrombeneaththepipewillllowintoan
Automatic
Drainandthecondensate
willbe removed.
Normally
therewouldbea unionin thepipeanda
shut-offvalv€to allowmaintenance
to the.dorvnstream
componanlsr
@ luto o."tn
Everydescendingtube shouldhavea drainat its lowestpoint. The mostetlicientmethod
is an Auto Drain,whichpreventswaterfrom remainingin the lube shouldmanualdraining
be neglected.Directlyabov€the Auto Drainis an expansionchamb6r,allowinglhe air to
cool (through€xpansion)and removemore€ntrainedliquid.
0
alr ServlceUnlt
Conditionsthe compressedair to providecleanair at optimumpressure,and occasionally
adds
lubricantto €xtendthe life of thosepneumaticsystemcomponentsthat ne€dlubrication.
@ Dlrectlonalvalve
Altematelypressurizesand exhauststhe cylinderconnectionsto controlthe directionof movemem.
Shownas an indiMdualdevice,ther€may b6 a numberof directionalvalvesgroupedon a manifold.
DO NOT COPYWITHOUT WRITTEN PERMISSION
-4-
PitEUrrartcTEcHNoLocY
6
Adu"to,
Transformsthe potential€nergyof the compressedair intomechanicalwork.Shownis a linearcylinder,
it can alsobe a rolaryactualoror an air tooletc.
@ SpeedGontrollers
Allowan easyand steplessspeedadiustmentot the actuatormovement.
We will discussthesecomponenisin moredeiailin sections4 to 7, aftera lookat the theoryof
compressed
air.This is a musttor understanding
whathappensin a pneumaticsystem.
DO NOT COPYWTTHOUTWRITTENPERMISSION
-5-
P
EU ATIc TEcH OLOGV
3 C O M P R E S S EADI R T H E O R Y
JNITS
The Intemational
Syslemof Unilshasbeenin acceptanceworldwidesince1960,but the USA,UK, and
Japanstillusethe lmperialSystemlo a greatextent.
ll is exir€melyimportanlthat,in this€vershrinkingworld,all measurem€nt
systemsbecomecleady
underslood.The delinitivestudyot pneumaticson an inlernational
scalerequiresfamiliarityand competence
witheitherset of units;thereforethis documentwill employbothEnglishand Sl units.
Quantity
Mass
kngth
Time
Temperature,absolute
(Celsius)
TemDeraturc
Radius
Angle
Area, Section
Volume
Speed(velocity)
Angular Speed
Acc€leration
Inertia
Force
Weight
Symbol
m
second
Kelvin
'c
DegreeCelsius
2, CoMPoSEDUNrrs:
m
meter
Radian(n/m)
a,F,1-6,e.p I
A,S
m2
squaremeter
v
mt
cubic meter
v
m s''
meterper second
s'
radiansper second
a)
m s-2
nreterper sec.per sec.
J
m2 kg
kilogram per squaremtr
F
N
Newton
G
N
Earth acceleration
T
L E
Impulse
5
K
Ns
Work
Potentialenergy
Kinetic energy
Torque
Power
Pressurc
Standardvolume
Volume flow
Energy,Work
Power
Ngme
SI Unlt
1 . B A s I cU N I T s :
kg
kilogram
m
meter
w
E,W
E,W
M
P
J
J
t'
J
w
NewtonSecond
Joule= Newton meter
Joule
Joule
Joule
Watt
3. RELATTDTo CoMPnDSSED
ArR
p
Pa
Pascal
vn
In3n
Standad Cubic Meter
o
tn-n s'
Std. cubic meters/ s€c
E,W
Joule
N'm
P
w
Watt
Table3.1 Sl Unitsusedin oneumatics
DO NOT COPYWTTHOUTWRITTENPERMISSION
Remarks
0"C= 273.16
K
= kg ' rn's'2
9.80665m's-2
= kg . m2's-2
0.5-m-i
= J's-l
=N m''
at0 =0'Candp
=760 nm Hg
Pa.m3= N.m
p'O=N'm.s-r=W
-6-
P
EU
ATIc TEcHI{oIoGY
To nam€unitsby powersof l€n,smallerandlargerthantheabovebasicunits,a numbero( prctixeshave
b€€nagreeduponandarelistedbelow.
Powet
10-1
1O-2
iO-3
10-6
Preflx
Svmbol
d
c
m
deci
centi
milli
micro
Pourer
Preflx
Svmbol
101
fi2
103
tO6
Deka
Heclo
Kilo
Mega
da
h
k
M
],
Table3.2Prefixes
torpowersof ten
This l€adsus to a kPa (kilo-pascalor 1/100b ol a BAR)and an MPa (1,OOO,OO0
pascalsor 10 BAF).
Practicewiththeseprefixesand pay attentionto whatth€symbolrepresentsin termsof powersof ten. Pay
specialattentionto the difterencebetweenM and m,
Convertinglrom on€standad of unitsto anotheris welldocum€nted.
Convertingis easiestwh6ndealing
withan answer--- 6.9.whendea,ingwith a mathematical
formula,use one standardonly (tor all terms)and
thenconvertthe answer, Be awarethat formulaemay changewhenexpressedin difierentunitsor standards.
The tablesfollowingshowa comparisonbetweenthe MetricSl unitsand the lmperialunits.
Magnitude
Mass
L:ngth
TemDeraturc
Area. Section
Metric Unit (m)
kg
s
m
m
mm
n'
Facaorm +e
2,?05
0.o3s27
3.281
l.094
0.03937
sq. ft.
so.inch
cu. yard
cu. inch
cu. fl-
Volume
n'
m'
VolumeFlow
n'/min
dm3Jmin ffmin)
N
bar
Force
pound
ounce
foot
yard
inch
l.8oC+32
cm2
Pressure
Enelish(e)
dm3
scfm
scfm
ooundforce (lbf,)
lbf./sq.inch(psi)
10.76
0.155
1.308
0.06102
0.03531
35.31
0.0353r
0.2u8
14.5
Table 3.3aConversionof Units
DO NOT COPYWIHOUT WRITTENPERMISSION
Fsctor e +m
0.4535
?,8.3527
0.3048
0.914
25.4
('F-32)/1.8
0.0929
6.45t6
0.76/.5
16.388
2832
0.02832
28.32
4.448/.
0.06895
PNEU ATtc TEcHNoLocY
Engli$ to fil.lrlc
(itulriply By-To
llrlric lo Englilh
(Mulridy
Lqrgnl
Fn
hln
cm
m
Arr
md
crrf
mt
Volumr
mmt
cm'(cc)
L
L
By-To
mNs
in
in
0.0391
0.0394
0,3937
32E,|0
n
obrain
-)
Fo.c.
gl
kgf
N
2.iDs r 'loi lbf
lbf
2.2016
lbl
0.2248
Ke!
Fm = micron(miclongb4
mm- millitnoto,
am r conlimeter
mils-0,001 ilch
h-hch
n - foot
cr - culic cgntmater
L = titsr
gal (U.S,). U.S.gallon
9 r gram
kg - kilogl8m
oz. ouhoo
h-pdd
t6387
16.387
0.0283
26.329
3.785
mm3
cm! (cc)
mt
En.tty
ft.h
fi.lb
kwr
t.366
1.356
3,6
N.m
J
MJ
rwh
Volum0
inr
in'
lf
It3
gal(U,S.)
L
t.356
0.7157
W
kW
ll.lUg
np
W!lehl
ot
b
Powra
f.br's
hp
28,3i8
0.4536
k9
Tlmparaluat
qC- 5A"F'32)
Forca
bt
bt
bl
453.6
0,4536
ia.4lEa
sl
kE
Flov..b
SCFMx 2E.57- Nltnin
0.7375
0.7375
0.n7E
oz
b
O.005il
2.2046
mrf
qe
l|t,
Pll
Psl
Pri
Prt
Pg
Pii
psi
Pouar
w
kw
W.ighr
g
k9
645.16
6.,1516
0.0929
0,00142
0.0197
0.0t97
0,145
la.5o
la.4a
'|4,7
Enrgy
N.m
J
MJ
0.7375
l.3al
kg/cm,
xgl',rr,
kPa
bar
kgy'cm'l
Aru
in
id
tf
Praatur!
in{Hp)
h(HS)
psi
psi
psi
Prrt|0fa
mm(H,O)
mn(Hg)
bn
kPs
bar
kg/cm?
aln
inr
in'
ff
lf
gal (U.s.)
r 10'
2.s357
0.0s5t8
6 897
0.06697
0.07G1
pm
mm
cm
tn
It. b
li. h
6.10x 105
0.0610
35.320
0.0353
o.fi12
N.m
kg' m
2.51
25.,4
2.!A
0.046
0.73?5
1ag
h'
h'
ir
r.659
0.13811
L.n!tl
mls
in
in
Ir
lorNr
N.n
kg.m
0.616
0,1550
10.765
Obtain-)
Toqoc
n. b
It. lb
fi.lb ll.lb
T!npar.hr!
'F-(1.8r"C)+32
Flo{ r.b
Numint0.035.SCFli
gf= gram- forcr
kgl-tilogratn.brcs
lbfepound-krcr
N.m-nanlon-Ddtr
k9.m.lilog.t|t|.m.br
lt.lb.loqt.pound
mm (HrO). rnllorb( *abr
collmn
h (Hp) . inche! rabr coltm
nm (Hg) - nilllnote. mcrcuy
colurm
in (Hg). ind|ge tne|trty
colu|m
N
p€|squarshdl
pri I pounds
kPa. klopasc€ls
atn . qtrnospher.3
J - iruL
MJ. firegajoulo
W-wa[ lW. kibwn
t!'\lh. bloratt-hour
hp. horsaporver
€ ' dogff8 C€|rtglade
'F - d.gr€e Fahmh.il
! - lgcon(b
Nunin - Nofiul lit l! F9r
ninub
SCFi = Sd. cllitic feet per
rnirute
B.aic FgnnlLr
Orda ciEumle.anoa. |!O - 2fi
Ord. a'r8. d.
Fotce=Prg9qjr€xAfea
C.ylir{t€rVolurre(md eide)(pislonaraa . t9d cross-r€c1ion
a|oa) r d()Ie
Cflinder Volume(headend) tigton a.ga x *.!ko
Tor$re - h.co t p€rp€odd/hr
dlr.r€c ftgrn $haft
Table3.3b Conversionof Units
DO NOT COPYWITHOUT WRITTENPERMISSION
-8-
P N E u r i t a r t cT E c H N o L o c Y
P R E S S UR E
ll shouldb€notedthatthe Sl unitof pressureis th€ pascal (Pa)
I Pa= I N/m2(Newtonpersquaremerer)
This unil is extremelysmalland so, to avoidhugenumbersin practice,an agreementhas been madeto
use lhe bar as a unitot 100,000Pa.
100,000Pa = 100 kPa = 1 lxr
It correspondswithsutticientaccuracyfor practicalpurposeswiththe old metricunit kgf/cm".Moreprecise
equivalentsare I STDatm =14.696psi =1.01925bar =i.03329 kgrt/cm'?.
ln Englishunitspressureis expressedin psl (almostnev€rretenedlo as p.s.i.as one wouldexpect),or
poundsp€rsquarelnch,also relatinga torceto an area.
Physlca
iloteorology
Pneumatlca
500 kPa
i p
t
45r
I
:
!
irn,
200 kPa
Atmospheric
Pressu16
II
l'' I
100kPa
1050mbar
30 in Hg
Standard
14.696psi
Vacuum
Flg. 3.4 the varioussystemsof prcssureindication
A pressurein the contextof pneumaticsis assumedas bver-pressurei.e. aboveatmosphericpressure
'and is commonlyreferredto as gaugo (also geg€)pressure(GA or pslg).
A pre*surecan also be expr€ssedas absolut€pressure (ABS or psla) i.e, a pre*surerelativeto a tull
vacuum. In vacuumtechnologya pressurebelowatmosph€ric
i.e. under prcssu]a is us€d.
The variouswaysof indicatingpressurear€illustratedin fig 3,4, usinga standardatmosph€ric
pressureof
1013m/baras a reterence.Notethat this is not 1 bar, althoughfor normalpneumaticcalculationsthe
dilferencecan be ignored.
DO NOT COPYWTHOUT WRITTEN PERMISSION
-9-
PNEU
ATIC TECHNOLOGY
F n o p e n n e so F G A s E s
t S o T H E R M I CC H A N G E( B O Y L E ' SL A W )
to its voltlme",
the pressureof a givenmassof gas is inverselyproportional
"...withconstanttemperature,
or: P' Y= constant
v=1i p=1
p1xVl
p2xV2
=
=
p3xV3
Fig. 3.5 illustration
of Boyle'sLaw
lf volumeV.= 1 m3ata standard absolutepressureot 101325Pa is compressedat constanltemperature
to a volumeV = 0.5 m"then:
p , . v . ,=
P",V"P"=#
i.e. p"=
to1325m.i.n3
u
202650Pa
o3n3
TheratioV1^r'2is the"Compression
Ratio"cr
witha gaugepressure
of 4 bar,
' { =
\2
aill=l3 =
a.gs
1013
Thetablebelowshowsthe pressureratiofor pressuresfrom 1 to
10 barabs.
p
cr
1
0.987
2
1.987
3
2.974
4
3.961
5
4.918
6
5.935
7
6.922
8
7.908
8.895
10
9.882
Notethe differencebetweenr€ducinga volumeot atmospheric
air to halt,1:2.026and the pressureratioat
a gaugepressureof 1 bar (2 sps),1:1.987!Butthis is theory;- no adiustmentis madetor practicewhenw€
simplyuse gaugepressur€in bar +11
lf volumeV, = 1 ff at a standardabsolutepressureof 14.7psi.is compressed
at constanttemp€rature
lo a
volumeV, = 0.5ft" then:
o1.lA
P,.V, = P"'V" P"=-t
.
i.e. p, =
LA7pd(L fr
= 29.4 Psla
-
DO NOT COPYWNHOUT WRITTENPERMISSION
-10-
PNEU ATIc TEcHtIoLoGY
Calculalingthe compressionratioin lmp€rialor Englishunitsis donein the sameway, p, convertedto
absolulepressure(add 14.7psi) dividedby 14.7psi (oneatmosphere).
P(pslq)
cf
10
1.68
30
20
2.36
40
3.72
3.04
50
4.4
70
5.76
60
5.08
80
6.44
90
7.12
100
7.80
On lh€olher handit wouldbe wrongto use Boyle'sLaw in pneumatics.In the caseof toolsas well as
cylindersthe changeis neverlsothermicbut alwaysAdiabaticchange.(Seefunherbelowand pg. 58 - 61
I S O B A R I CC H A N G E
Charles Law
'...at constantprossure, giv€n
a
massol gas increasesin volume
Celsiusrisein temperature-- --l-
459f,
bv# of its volumelor everydegree
191gysrvoprisein temoerature.
Law ot Gay Luaaac
v1
T1
and w=+
w=E
Y/7= constant,so
Exampfe
1: W = 100m3,I1 =9.9, 72=2O.C,W=?
We haveto use the absolutetemperaturesin K, thus
100
;;;=
ztr
v2
:;;,
.tJ
W=
1 n n . ? q -?
'-:::::
273
= 107.326m'
i
_>-T
Exampfe2: !4 = 100ff, f 1 = 40"F,T2= AO"F,VZ= ?
Wehaveto useth€absolute
tomp€ratures
in H (Rankine),
thus
1oo- v2
4997
539?
vz= 19!Ij!2Z=1ssrt"
4997
I S O C H O F I CC H A N G E
'at constantvolume,the pressureis proportional
to the temperatur€"
('lsochoric"comestromth€ Greekwordsropo Osad"chora'),for
space,fieldetc. , and roo- , "iso' = equal)
P1.P2
so TT:T,Z
ano
T2
P=nT1
Wheref is the absolutetemp€rature
in K (Kelvin)or R (Rankine).
->T
The previousrelationships
are combin€dto providethe generalgas equation:
p't v1
pzw
DO NOT COPYWTTHOUTWRITTEN PERMISSION
-11-
P
EUHATIC TECHNOLOGY
basistor calculalionto designor sel€ctpneumaticequipment
This law providssone of the mainth€ofetical
\
twhen temperature
changeshaveto be considered.
( I S E N T R O P l C )C H A N G E
ADTABATTC
The previousLawsassumea slowchange,so onlythe two considered
magniludesare changing.h praciice,for example-- whenair flowsintoa
cylinder,this is nol the caseand 'adiabaticchang€'occurs.ThenBoyle's
Law ' p.Vis constant" changesto p. lA= constant.
It wouldtake too muchtimeto go intogr€aterd€tail,the diagram
illustratesthe ditferenceclearlyenough:w€see that thereis a lossof
volumewhenpressurebuildsup quickly.We will meetthis law againwhen
of cylinders.
discussingthe air consumption
S T A N D A R DV O L U M E
it is necessaryto reterall
betweenvolume,pressureand temperature,
Dueto thesemutualr€lationships
(m"r),
the
Delined
as the air quantityof
volume, standard cubic meter
daia on air volumeto a standardized
pressure
(101325
Pa)-- or the
and
an
absolute
ol
760
mm
Hg
1.293kg massal a temperatureof ooC
pressure
(absolute
14.7psi) havinga
(scf)
is
cubic
foot
of
air
at
sea
l€vel
of
standardcubic foot
which on€
temperatureof 680Fand a relativehumidityof 360/o.
FLOW
The basicunitfor volumetlow "O' is the NormalCubicMeterper second(m"%).In pneumaticpractice
volum€sare expressedin termsof lit€rsper minute(l / min)or normalcubicdecimetersper minute(dm?min).
l The usualnon-metricunittor volumetlowis the "standardcubicfoot p6r minute",(sclm).
)
Bernoulll's Equatlon
Bernoullistates:
'lf a liquidof specific
througha tub€withvaryingdiameters,the totalenergyat
aravityflowshorizontalty
point1 and 2 is the same'
or,pt + | p. v't2= Fe+ L
2 P'v2z
The relationship
betweenpressure,the velocity
ol the air, andthe densityot the air (p) appliesto
gases if the flow speeddoes not €xc€ed3a)0m/s
approx.(1083tusec).Velocity(tysec)can be
calculated:
-->
-----+
v1
Flg. 3.6 illustralionof Bemoulli'sLaw
v= 0.054Q/D'?(O is cfm, D is i.d. in inches)
Applications
of this equationare the venturitube
and tlowcompensalion
in pressureregulators.
AIR HUMIDITY
Atmospheric
air alwayscontainsa percentageof watervapor.The amountof moisturepresentwill depend
on the atmospheric
humidityand temp€rature.
Whenatmospheric
air coolsit will reacha certainpointat whichit is saturaledwith moisture,this is known
polnt.
the
dew
lf
the
air coolsfurtherit can no longerreiainall lhe moistureand th€su|plusis expelledas
\as
Tminiaturedropletsto torm a condensate.
DO NOT COPYWIIHOUT WRITIEN PERMISSION
-12-
P N E U I I A T IT
cEcHNoToGv
The actualquantityol waterlhat can be r€taineddependsentirelyon temperalufe;1mt of compr€ss€d
air
is only capableof holdingthe samequantityof watervaporas 1m3of almosphericair.
The tablebelowshowsthe numberof gramsof waterper cubicmeter(andcubicteet)tor a wide
lemperalurerangetrom-40'C to +40"Cand from--400Fto 200 oF.The boldline refersto atmosphericair with
fhe volumeat the lemperaturein question.The thin line givesthe amountof waterpet StandardCubic .
dimension.All air consumptionis normallyexpr€ssedin standardvolume;this makescalculationunnecessary.
Forthe lemperaturerangeof pneumalicapplications
the tablebelowgivesth€exactvalues.The upp€rhalt
refersto temperatures
abovelr€ezing,the lowerto belowfreezing.The upperrowsshowthe contentof a
slandardcubicmeter,the loweronesthe volumeat th€giventemperature.
Temperature oC
g/m'n *(Standard)
0
5
6.99
9.86
g/m (Atrnospheric) 4.98
Temperrture oC
0
4.98
g/m'n (Standard)
6.E6
9.5t
-10
2.28
3
-5
3.36
g/m (Atmospheric)
4.98
Temperstur€oF
giftr *(Srandard)
gifC (Ahospheric)
32
.137
Temp€rature"F
32
.t37
s/fC (Shndard)
g/ft' (Atmospheric)
.r37
40
.188
.185
30
ItA
.177
l5
20
25
30
35
t3.76 18.99 25.94 35.12 4 7 . 1 9
l0
4.98
60
.4
- 3t J
20
.083
.085
40
OJ.UJ
13.04 17.69 23.76 3t.64 4 1 . 8 3 5 4 . 1 1
-t5
1.52
-20
1.00
l.6l
1.08
60
.78
.71
l0
.053
.056
100
1.48
t.z9
0
.033
.036
-25
0.u
-30
0.4
-35
0.25
0.15
0.7
0.45
o.29
0.18
120
2.65
2.2?
-10
.020
.023
140
4.53
3.67
-20
.ot2
.014
40
lm
160
7.44
5.82
-30
.007
.009
I l.8l
8.94
40
.004
.005
Tabla 3.7 WaterSaturationof Air (DewPoint)
The term g/tf standardr€fersto a volumeat gzoF.At BooFit.svolumeis extendedto l+ (80-32) or l.i tf
459?
Consequently
to haveone standardcubicloot at 80oF,1.1tf of atmosphericair at 800Fare requiredwith all its
watercontent;so that makes1.1 x 0.71= 78 gramsol water.
Relative humtdlty
With the exceptionof extremeweatherconditions,such as a suddentemperaturedrop, atrnosphericair is
neversaturated.The ratioof the actualwatercontenlandthat of the dew pointis calledrelativehumidity,and
is indicatedas a percentage.
Relatlvehumldlty (r.h.) =
actual water content
saturatlonqu.ntlty (dewpoint)
1ovh
Erample 1: Temperature25oG,r.h.65"/0.Howmuchwateris crntainedin 1 m3?
Dewpoint2soo= 24glm".0.65= 15.6g/mt
Whenair is compressed,its capacityfor holdingmoisturein vaporform is onlythat of its reduced
volume. Hence,unlessthe temperaturerisessubstantially,
waterwill condenseout.
Erample 2: 1o m3 ol almosphericair at 15oc and 65yor.h. is compresssdto 6 bar gaugepressure.The
temperatureis allowedto riseto 25oC. How muchwaterwill condenseout?
FromTable3.7:At 1soo,10 m3of air canholda maximumof 13.04g/m..10m"= 130.4g
DO NOT COPYWTTHOUTWRITIEN PERMISSION
-13-
P NE U A T I c T E c H t t o L o G Y
At 650/o
r.h.the air will conlain130.4g '0.65= 84.9g {a)
The reducedvolumeol compressedair at 6 bar pressur€can be calculated:
pl'v1 = pzvz =
p;
v1 = v2 = +H#
'10m3= 1.44
mc
of 23'76g '1'44 = 34.2g (b)
FromTable3.7 1.44m3ofair at 25oCcanholda maximum
equalsthe totalamountof waterin the air (a) minusthe volumethat ihe compressedair
Condensation
(b),
can absorb hEnce84.9- U.2 = 50'6 I of waterwill condenseoul'
to avoidharmfuletfectein lhe
Thiscondensatemuslbe r€movedbeforethe compressedair is distributed,
lineand the pneumaticcomponents.
Example3: Temperalure800F,r.h.65%. Howmuchwateris conlainedin I ff?
Dewpoint80"F= 0.71g/ ff. 0.65- o.aog/ff
Observethat the metric chart dimenslonswould exhlbll ldentical relationshipswhen convertedto
lmperialunlts.
g HzO/m 3
500
't5
t0
5
0.1
€0
from-€0 to aboul+80"C
Flg. 3.8 Dewpointsfor temp€ratures
the thin curveat
Th€boldcurveshowslhe saturationpointsot a cubicmeterat the relatedtemperature,
standardvolume.
DO NOT COPYWITHOU'f WRITTENPERMISSION
-14-
P N E U I , | A T ITc E c H N o L o G Y
P R E S S U R EA N D F L O W
The mostimportantrelatlonshlptor pnGumatics
is that b€twe€npressur€and flow.
THEYARENOTTHESAME.DO NOTTHINKTHEYARE INTERCHANGEABLE
TEFMS..,e.g.a 'Iow
conlrolis nol a regulalor(repeatas r€quiroduntilretained),lt is the relationshiobetweentlow and pressure
that we will nowconsider.
ll thereis no tlow,the pressurein an entiresystemis the sameat everypoint,but whenthereis flowfrom
one Pointto another,th€pressurein the latterwill alwaysbe low€rthatat the first.This differenceis call€d
pressuredrop.ll dspendson threevalues:
. initialpressure
. volumeof f low
. llow resistanceof the connection
The flow resistancefor air has no unit;in electricityits equivalentis Ohm (Q). In pneumatics,th6 opposile
of resislanceis used,the equivalenlflow section(S, kv or C" factor)-- a conductancevalue.The equivalent
tlowsectionS is expressedin mm' and representsthe areaof an oriticein a thin plate(diaphragm)which
crsatesthe samerelationshipb6tw6enpressuresand flow as th6 €lementdetinedby it. Valveshave
complicatedoritic€shapes,thereforelhe flow ratethroughlhe deviceis measuredfirst,and thenthe device
may be assignedthe corresponding
equivalentflowsection.An easyapproximation
wouldbe that:
C, ol 1= 18Smm',e.g.equivalent
orificeof 18 mm' equalstheflowof aC, i.
This relationshipis by dotinitionthe sameas in electricity,wherefuoltagedropequalscurrenttimes
resistance".
This can be transformedfor pneumaticsto "pressuredropequalsflowdividedby FlowSection",
only,whilethe electricunitsare dkectlyproportional,
lhe relationshiplor air is very complexand neversimply
proportional.
In electricity,a cun€ntot 1 A (oneAmpere)creates,overa rosistorof I Ohm,a voltagedropof 1
Volt. Regardlessif this dropis trom 100to 99 or from 4 to 3 volts,the pressuredropoverthe sameobiectand
withthe samestandardvolumeflow varieswiththe initialpressureand alsowiththe temperature.Reason:the
compressibility
of the air.
For definingone ot the four interrelated
data,mentionedpreviously,fromthe oth6rthra6,we requirea
diagram.
10
Sonic Flow
(jn (s..4r/ ,nin)
_
O (dmgn/min)
Flg, 3.9 Diagramshowingth€ relationship
betw€€npressureand flowfor an oriticewith an equival€ntFlow
Sectionof 1 mm"
DO NOT COPYWTTHOUTWRITTENPERMISSION
PNEU
ATIC TECHNOLOGY
The trianglein the lowerrightcornermarksthe rang€of "sonicflowspeed".Whenthe airrlowreachesa
speedcloseto lhe spe€dof sound'flowcan no longerincrease-- what€verthe ditferenceof pressure
betweeninputand outputmightbe. As you can s€e,all the curvesdropverticallyinsidethis triangle.This
meansthat the flowno longerdependson the pressuredrop,but onlyon the inputpressure.
lJse of the diagram:
The pressurescaleat the lettside indicatesbothinputand outputpressure.At the firstverticallineon the
lett,whichrepresentsa zgroflow,inputand outpulpressuresarethe same.The variouscurves,lor inpul
pressureslrom 1 to 10 bar,indicatehowthe outpulpressuredecreaseswithincreasingflow'
Example1:lnputpressure6 bar,pressuredrop 1 bar = outputpressure5 bar.We followthe curve"6'to the
pointwhereit cutsthe horizontallinemarked'$. Fromtherewe go verticallydownto the Flowscale
(dottedline)and tindabout55 ymin.The 9.44 l/minwrittenbelowthat lineis the exactvalue,calculated
'StandardVolume
withthe formulafurtherbelow.Theseinputand outputpressuresdefinethe so-call6d
FlowOn",a figuretoundin valvecataloguesfor a quickcomparisonot the flowcapacityot valves.
The VolumeFlowof 9.44 l/minappliesto an element(Valve,fining,tub€etc.)withan equivalentorifice"S"
of 1 mm'. lf an €lementhasfor examplean "S' ot 4,5 mm',the flowwouldbe 4.5 timeshigher,in this case4.5
. 54.44limin= 245 Umln
Example2: Givenan elementwilh an 'S'ol 12 mm",a workingpressureof 7 barand an air consumptionot
willresult?
600ymin.Whatoutputpressure
witha llowof ff = 50 l/minthroughan
A flowof 600l/minthroughan"y ot 12mm"corresponds
€quivalent
Weneedthisconversion
fortheuseof thediagramof lig.3.9.Wenow
sectionof 1 mm'?.
line
withth6verticallinetor 50l/min.A horizontal
followthecurvestarting
ai 7 baruntilit intersects
about6.3bar.
towardstheDressure
scaleindicates
Formu tae:
Whenit is requiredto havea mor€exactvaluethanthat whichcan be estimatedfromthe diagram,the flow
can be calculatedwith one of the two followingformulae.
A glanceat the diagramof fig. 3.9 makesit clear,thattheremustbe ditfer€ntlormulaelor the sonicflow
rangeand the "subsonic"flowcondition.The transientfromsubsonicto sonicflow is reached,wh€nthe
pressurcratioof the absoluteinputand outsutpressuresis l€ssor equalto 1.896:
pl + 1,013<1.896. (pA+1.013)
Sonic tlow:
pl + 1.013> 1.896. (pa +1.013)
Subsonlcflow:
The Volumeflow Olor subsonicfloweouals:
' (pl -pa) (vmin)
Q = x2.2 .5.{(pa + 1.013)
andfor sonicflow:
O= 11,1.S.(p1 + 1.013)(Umin)
'
Soundis, after all, vibrating air molerules.Thus the "speedof sound" (sonic condition, Mach #) is the t€rminalvelocity
I for air movemenl For comprcssedair to !!99 therc mustbe a prcssuredrop -- andmaximumflow occursat a certain %
pressuredrop. Therc can be a greaterpressuredrop (up to 100%)but maximumflow (for whatev€rsizeorifice) occursat
46% of pr
DO NOT COPYWTII{OUT WRTTTENPERMISSION
-16-
P
EUTATtcTEcHNoLocY
whersS inmm'and
p inbar;22.aisa constant
andper
withthe€ouarion
, whichis litersper60 seconds
ffi
torce(delinedbytherulingpressure).
Notethata pneumalic
systsmcannev6roperat€
as a supply
satislactorily
undersonicflowconditions,
pressure
of,forexample,
6 barwouldgiveuslessthan2.7barforwork.
Erample3:W€catculate
th€flow,assumed
in example
2, withaninputpressure
of 7 bar,a totalequival€nt
flowsectionof 12mm2forvalvsandtubesandthecalculated
pressure
working
ot 6.3bar:
't2
Q = 22.2. . !7.313'0.7 = 602.74Umln.
Thisshowsthattheaccuracy
pneumatic
of thediagramis sufficient
forpractical
us€.
tn Imperlal unlts
The formulafor subsonicflow: e = 224€lc."
And lor sonicflorir: Q=0.486C, (p2+14.7)
P
t,.
ro!
=
at)
n
e
'
=
r9
.|l
Downstreamprasauro(wrtical [nes) in psig
Flg. 3.10Air tlowcurvesfor a deMcehavinga C, of 1.0 (deriv€dfrom the abovetwo tormulae)
Flowat a certainpressuredropcan be deriv€dfrom Fig.3.10.
Selectlh€ pl (upstreampressur€)lrom the diagonallineand tollowstraightacrossto the verticalaxis-- this
is the maximumflowat that pressure.Nowsel€cta pressuredroptrom€itherthe bottomnumbers
pressure)or from the numberson th€outerarc of the gfaph(Ap in psi). Next,lollovvthe curveol
(downstr€am
the selec{edpl untilit intersectsyourp2 or Ap s€lectionand thenfollowstraightacrossfrom that pointto the
verticalaxisto find tlowin sctm.
DO NOT COPYWTIIIOUT WRITTENPERMISSION
-17 -
P N E U T , | A T I CT E C H N O L O G Y
The resultsare linear,€.g.il the devicein applicationhasa C, ot 2.0 multiplyyour resultlrom tig' 3' 10 by 2, C,
of 0.5 multiplyby one half,etc.
Observ€thatcriticalllow occursat a cgrlainpressuredrop- to discoverthis for yourselffind 100psig on the
46
diagonalcriticalflowline.Dropstraightdownto the p2 horizontalaxisand notethat p2 is approximately
46%producesmaximumflow.Therecan be a
psia.This confirmsthat a pressuredropot (approximatelyl
greaterdropin pressurebut tlow wlll not Increase.
(withso many
Obsorvethat useof Fig.3.10 requitesa knownpressuredrop.In realworldapplications
estimateof whata
a
safe
variables)this knowledgeis difficultto comeby, so lhe cautiousindividualwill relyon
pressur€
The NFPA
is
very
difficult.
drop
desir€dpressuredrop;ught to be. Predictinga system'sactual
pressure
dropof 15%.
(NationalFluidPowerAssociation,
a maximum
a U.S.standardsgroup)recommends
Example1:Howmanysctmwill flowthrougha valvewitha C, of 1.0 givena supplypressureot 80 psig and a
20 psi pressuredrop?
Fromthe chartFig.3.10find 80 psigon the criticalflowline.Next,lind 60 psig (80 psigminusa 20 psi
pre*suredrop)on the horizontral
axis at the bottom.Movingverticallyfromthe 60 psigtind the
intersection
of the 80 psigcurve(fromthe criticalllow line)and movestraightacrossto the verticalaxis
38 scfmwill be tound,
wherethe answerot approximately
Example2: A flowof 40 sctmis requiredfor an applicationand supplyis 60 psig.WhatsizeC" mustall
comDonents
exceed?
Fromthe chartFig.3.10findlh€ scfmot a C" ot l.0. It the applicationflowsto atmosphere(e.9.a
"blow-off)the criticalflowsc{mwill be used;if the applicationinvolvosotherdevices(e.9,cylindersor
actuators)usethe ruleof thumb157opressuredrop.Observethatat 60 psigsupplya q of 1.0orifice
24
will flowapproximately
36 scfm.Witha 15"/.pressuredrop (p2is 51 psig)the llow is approximately
sctm-- andthusa C" of morelhan 1.66will provide40 scfm(1.66x 24 = 40).
on C" pleasereterto pages84 and tollowingdealingwilh sizingof componentsand
For moreinformation
sy$ems.
DO NOT COPYWTIFIOUTWR]TTENPERMISSION
-18-
P N E U A T T cT E c H N o L o c Y
COMPRESSORS
engrgyof an eleclricor combustionmotorinlo the pot€nlialenergy
A compr€ssor
conv€rtsthe mechanical
of comoressedair.
and Rotary.
Air compressors
lall intotwo maincategories:Reciprocating
withinthesecat€goriesare shownin fig 4.1.
The principaltypesot compressors
Compressors
Displacement
usedfor PneumalicSystems
Fig. 4.1The MainCompressor'types
RECIPROCATINC
GO M P R E S S O R S
SIngle stage Plston Compressor
pressureis
Air tak€nin at atmospheric
r
t compressedto the requiredpressurein a single
stroke.
Downwardmov€mentof th€pistonincreases
volumeto createa loweroressurethanthat of
the atmosphere,
causingair to ent6rthe cylinder
throughthe inletvalve.
At the end of the stroke,the pistonmoves
upwards,th€inletvalveclosesas the alr is
compressed,
forcingthe oulletvalveto open
dischargingair intoa r6c6iv6rtank.
Thistypeot compr€ssor
is gen€rallyus€din
systemsrequiringair in the 3-7 bar rang€.
Flg. 4.2 SingleStagePistonCompressor
Two stage Platon Compressor
In a single-stage
compressor,
whenair is compressedabove6 bar,the excessiveheatcreatedgreatly
reducesth€efficiency.Becauseof this,pistoncompressorsusedin industrialcompressed
air syslemsare
usuallytwo stages,
pressureis compressedin two stagesto the finalpressure.
Air takenin at atmospheric
\
)
DO NOT COPYWTIIIOUT WRITTENPERMISSION
- 1 9-
PNEU ATIc TEcH oLoGY
It the finalpressur€
is 7 bar,the firststage
normallycompresses
the air to approximately
3 bar,afterwhichit is
cooled,ll is thenfed
inlo the secondslage
cylinderwhichcomDressesit to 7 bar.
The compressedair
ent€rslhe second
stag€cylinderat a
9reatlyreduc€dtemperatur€afterpassing
throughlhe int6rcooler,thus improving
etficiencycomparedto
that ot a singlestage
unit.The final delivery
temperaturemay be in
th€ regionof 120"C.
Flg. 4,3 Two StagePistonCompressor
Dlaphngm compressor
+
Diaphragmcompressorsprovidecompressed
air in the 3-5 bar rangetotallytree of oil and are
thereforewidelyus€dby tood,pharmaceutical
and similarindustries.
Output
The diaphragmprovidesa changein chamber
volume.This allowsair intakein the downstroke
and compressionin the up stroke.
Smallertypes,witha fractionalHP electric
motorand smallreseryoirmakepossibleportable
compressoci,ideallor spraypainting,
Flg. 4.4 DiaphragmCompr€ssor
DO NOT COPYWTMIOUTWRITTEN PERMISSION
-20-
P N E U M A T I CT E C H N O L O G Y
I R O T A R YC O M P R E S S O R S
I
Rotaty stldlng vane comPressor
mounted
This hasan eccentrically
rotorhavinga seriesof vanessliding
in radialslols.
As the rolorrotales,cenldtugal
,orceholdsthe vanesin contaclwith
the statorwall and the space between
th6 adiacentbladesdecreasestrom
the
air inletto outlet,so compressing
air.
Lubricationand sealingis
achievedby inlectingoil intoth€air
streamnearthe inlet.The oil also acts
as a coolantto limitthe delivery
tempe€ture.
Fig.4.5 Van€Compressor
9crew compressor
Two meshinghelicalrotorsrotatein opposite
directions.The freespacebetweenthem
decr€asesaxiallyin volumeand this
compressesthe air trappedbetweonthe rotors
1 (figa.6.).
a
'
Oil floodingprovideslubricationand sealing
betweenlhe two rotatingscrews.Oil separators
remov€this oil fromthe outletair.
(
Drive
(
Continuoushighflow ratesin €xcessof 400
m"/minare obtainabletromlhes€machinesat
pressuresup to l0 bar.
thistype
Moreso thanthe VaneCompressor,
of compressoroffersa continuouspulse-free
delivery.
The mostcommonindustrialtype of air
machine,
compressoris stillthe reciprocaling
althoughscrewand vanetyp€sar€tinding
increasingfavor.
Flg 4.6 Scr6wComprossorPrinciple
C O M P R E S S O RR A T I N G
or /min,dm13/sor
capacityor outputis statedas StandardVolumsFlow,givenin m3yy's
A compressor
litors/min. Th€capacitymay alsob€describedas displacedvolume,or 'TheoreticallntakeVolume",a
tigure.For a pistoncompressorit is basedon:
theor€tical
Q (Umin)= (pistonareain dm') x (strokelengthin dm) x (# ot tirststagecylinders)x (rpm)
O (cfm)= ((pistonareain in'?)x (strokelengthin inches)x (# ol lirsi stagecylinders)x (rpm))/ 1728
I
J
onlythe firstsiagecylindershouldbe considered.
In the caseof a two-stagecompressor,
The effectivedeliveryis alwayslessdueto volumetricand thermallosses.
DO NOT COPYWTIHOUT WRITTENPERMISSION
-21 -
P N E U u a r r cT E c H i r o L o c v
The volumeloss is inevitable,as it is not possibl€to dischargeall of lhe compressedair tromthe cylinder
at the end ot lhe compressionstroke,thereis somespacelett,the secalled "deadvolume".
Thermallossoccursdue to the lact that duringcompressionthe air assumesa very hightemperature;
thereloreits volumeis increasedand decreaseswhencoolingdownto ambienttemperature(seeCharlesLaw
in section3).
Volumetrlc Et clency
.. treeair delivered
I ne ratlo:
expressedas a p€rcentageis knownas lhe volumelricetficiency,and will vary
-Eii;;;ft;with lhe size,type and makeot machine,numberof stagesand ths tinal pressure.The volumetricefficiency
ot a two-siagecompressoris lesslhan that of a singlestag6typ€as bothth€firstand secondstagecylindeis
havg d€advolum€s.
Thermal and Overall Etficlency
Besidethe lossesdescribedabove,thereare also thermalefiects,whichlowerthe €tticiencvot the air
compr6ssion.
Theselossesreducethe overalletficiencyfurtherdependingon th€compressionralioand load.
A compressorworkingat almosttull capacityaccumulatgsgreatheatandioses efficiency.In a two srage
compressor,the compressionratioper stageis lessand th€air, partlycompressedin a firststagecylinder,is
cooledin an inter-cool€r
beforecompression
to tinalpi€ssurein a secondstagecylinder.
Example:lf the atmosphericair,takenin by a firsl stagecylinder,is compressedto a thirdof its volume,the
absolulepressur€al its outletis 3 bar.The heat,developedby this relativelylow compression,
is
correspondingly
low.The compressedair is then led to a secondstagecylinder,throughthe intercooler,and then againreducedto a thirdof its volume.The linal pressureis then 9 bai abs.
The heatdev€lopedby compressing
the sameair volumein a singlestagedirecttytromatmospheric
pressurelo 9 bar.!.,wouldbe muchhigherand the ov€rallefficiencyseverelyreduced.
The diagramin fig. 4.7
comparesthe typicaloverall
efficienciesof singlsand two
stagecompr€ssors
with
901"
varioustinalpr€ssures.
I
Totall8O7o
For low final pressures,a
Etlicienw70%
singlestagecompressoris
I 6o%
better,as its purevolum€tric
I
efticiencyis higher.With
increasingfinal pressure
FinalPressure
however,thermallosses
becomemoreand more
importantand two stag€types,
Flg. 4,7 OverallefficiencyDiagram
havinga higherthermal
etficienry, becom€preterable.
I
The specltic energy con3umptlon is a measureof.theoveralleflicienryand can be us€dto €stimatethe
genoratingcost of compressedair.As an averagefigure,it can be assumedthat one kW of olectricalenergyis
neededfor the productionof 120-150ymin(= 0.12...0.15mgn/ min/ kW),tor a workingpressureof Z bar or 1
HP ot electricalenergyis neededto produce4-5 cfm at a workingpressureof 100 psi.
Exactfigureshaveto be establishedaccordingto the type and size of compressor.
DO NOT COPYWTIHOUT WRJTTENPERMISSION
-2-
P N E U M A T I CT E C H I { O L O G Y
roM P R E S S OARC C E S S O R I E S
AIR RECEIVER
or vertically
inslalledhorizontally
An air r€@iveris a pressurevesselot weldedste€lplateconslruction,
to receiv€ihe compressodair,therebydampingthe initialpulsations
lrom the aftercooler
direc y downstream
in lhe air llow.
Its main,unctionsat€io storesutticientair to meettemporaryheavydemandsin excessof compressor
'unloading'ot lhe compressor,but il also providesadditional
capacity,and minimizefr6quent'loading'and
coolingto precipitateoil and moisturecirded ov€rfromthe aftercooler,beforethe air is distributedfurther' To
this end it is an advantageto placethe air receiverin a cool location.
The vesselshouldbe fittedwitha safeg valve,pressur€gauge,drain,and inspectioncoversfor checking
or cleaninginside.
Slzlng a tecelver
Air receiversare sizedaccordingto the compressoroutput,sizeof th€syslemand wh€lherthe demandis
r€latively
constanlor variabl€.
in industrialplants,supplyinga network,are normallyswilchedon and otf
Electrically
drivencompressors
This needsa certain
b€tweena minimumand a maximumpressuro.Thisaontrolis called"automatic".
minimumreceivervolumeto avoidoverfrequentswitching.
Mobilecompressors
witha combustion€nginearc notstoppedwhena maximumpressureis reach€d,bul
the suctionvalvesare liftedso thatlhe air can freelyflowin and out of the cylinderwithoulbeingcompressed.
and runningidle is quitesmall.ln this caseonlya small
The pressuredifferencebelweencompressing
is needed.
IJ receiver
'
For induslrialplants,the rul€of thumbfor the sizeof the reservoiris:
Air recelvercapaclty > compr€ssoroutput of compressedair pcl minute, (Not FreeAlr)
Somewouldsuggesta factorof x1.5whensizinga receivertor a largesystem,and as muchas x3 for small
comoressors.
Exampletcompressordelivery600 cfm (freeair)and an outputpressureof 100psi,Whatsize rec€iveris
r€quired?
t P"v=l
p1+ 147
Where V = capacityof r€ceiver
Q = compressoroutpul(clm)
plsssurc
Pa = atmosph€ric
P1 = compressoroutsul pressure
=77lf as a minimumnumber,a prudentsuggestionmightbeginwith 120ft".
V = (600'14.7y(10O+14.7)
INLET FILTER
A typicalcityatmosphorecancontain40 millionsolidparticl€s,i.e.dust,dirt,pollen,etc.per m".ll this air
wouldbe 320 millionpartsy'ms
or 7.8 millionparts/ff, An
werocompressed
to 7 bar,lhe concentration
importantconditiontor th6 roliabilityand durabilityol a compressoris that it mustbe providedwitha suitable
. and efficientfilterto preventexcessivewearof cylinders,pistonrings,€tc.whichis causedmainlyby the
I abrasiveeftectof thes€impurities.
DO NOT COPYWTTTIOUTWRITTENPERMISSION
-23-
PNEU ATtc TEcHNoLoGY
The lilter mustnot b€too tine as the compressoretticiencydecreasesdue to highresistanceto airflow,.and
so v€rysmallparticles(2-5y) cannotbe removed.
The air intakeshouldb€sitedso that,as lar as possible,cleandry air is drawnin, with intakepipingol
sufticionllylargediameterto avoidexcessivepressuredrops. Whena silenceris used,it may be arranggdto
includethe ah filter,whichwill be locatedupstr€amot the silencerposition,so that it is subject€dto minimum
pulsalionetf€cts.
AIR DEHYDRATION
AFTERCOOLERS
Atterfinalcompression,
the air will b6 hot and whgncooling,will depositwaterin considerablequantitiesin the
airlin€system,whichshouldbe avoidBd.The mosteftectiveway to removethe maiorpartof this condensate
is to subieclthe air to aftercooling,
immediatelyaftercompression.
Aflercoolersare heatexchangers,beingeitherair-cooledor watercool€dunits.
Alr cooled
Consistingof a nestof tubes
throughwhichthe compressedair
flowsand over whicha lorceddratt
of cold air is passedby meansol a
fan assembly.A typicalexampleis
shownin fig.4.8.
The outl€ttemperatureof the
cooledcompressedair shouldbe
approximately
15"C (60oF)above
the ambientcoolingair
temperature.
Flg. 4.8 Principleof an Air CooledAttercooler
Water cooled
Essentially,
a st€elshellhousingtubeswith watercirculatingon on€sideand air on the other,usually
arrangedso that the llow is in oppositedirectionsthroughthe cooler.The
is shownin fig. 4.9
Air Input
AirOutsut
CoolingWaterOUT
Fig.4.9Principle
ol a WaterCooledAftercooler
A water-cooled
aftercooler
should€nsurethattheairdischarged
wouldbeapproximately
1ooo(50oF)
abovethetemperature
of thecoolingwater.
An automatic
drainattached
to or integral
withtheaftercooler
removes
theaccumulated
@ndensation.
DO NOT COPYWTTHOUTWRITTEN PERMISSION
-24 -
PNEU ATtc TEcHt{oLoGY
that
gauge,andit is recommended
witha satetyvalve,pressure
shouldbeequipped
Attercoolers
areincluded.
to monitorairandwaterlemp€ratur€s
themometers
or sensors
DO NOT COPYWTIHOUT WRMTEN PERMISSION
-25-
PitEU ATlc TEcHNoLocY
AIR DRYERS
Aftercoolers
cool the air to within10-1socof the coolingmedium.The conlroland operatingelementsot
th€pneumaticsystemwill normallybe al ambienttemperature(approx.20cC).This may suggestlhat no
lurthercondensatewill be precipilated,
and that the remainingmoisturepassesout withthe exhaustair
releasedto almosphere.However,the tomperatureof the air leavingthe aftercoolermay be higherthanthe
sunoundinglemperalurethroughwhichthe pipelinepasses,for exampleduringnighttime.This situationcools
the compressedair turther,thus condensingmoreof the vaporintowater.
The measureemployedin lhe dryingot air is loweringthe d6w point,whichis the temperatureat whichthe
air is fullysalurat€dwith moisture(i.e.100%humidity).The lowerthe dew point,the lessmoistureremainsin
the comoressedair.
Thereare threemaintypesof air dryersavailable,whichoperateon an absorption,adsorplion,or
refrig€rationprocess.
Absorptlon (dellquescent) Drylng
The compressedair is forcedthrougha
dryingagentsuchas dehydratedchalkor
magnesiumchloridewhichremainsin solid
form,lithiumchlorideor calciumchloridewhich
reactswiththe moistureto form a solution
whichis drainedfromthe bottomof the vessel.
The dryingagenlmustb€ replenishedat
regularintervalsas the dew pointincreasesas
a functionof consumptionof the saltduring
operation,but a pressuredew pointof soc at 7
bar is possible(40 oFat 100 psi).
The mainadvantagesof this methodare
that it is of low initialand operatingcost,but
the inlett€mperature
mustnot exceed3OoC,
th€chemicalsinvolvedare highlycorrosive
necossitaiingcarelully monitoredfiltefing to
ensurethat a fine conosivemist is not canied
ov€rto the pneumaticsystem.
Flg. 4.10 Principleof the AbsorptionAir Dryer
DO NOT COPYWNHOI..TTWRITTENPERMISSION
PNEU$ATIC TECHNOLOGY
ldsorptlon (deslccant)Drylng
A chemicalsuchas silica
gel or aclivaledaluminain
granularform is contain€din a
verticalchamberto physically
adsorbmoisturetromthe
compressedair passing
throughit. Adsorptionis a
physicalprocessof a liquid
adheringto lhe surtaceol
certainmaterials(a sponge
absorbs,retainingmoisture
intErnally-- adsorbis a
surfaceetfect).Whenthe
dryingagentbecomes
by
saturatedit is regenerated
drying,heating,or, by a flow
of previouslydriedah as in fig.
4.11.
Wet comoressedair is
suppliedthrougha directional
controlvalveand passes
throughdesiccantcolumn1.
The driedair flowslo the
outletport,
Column1
Column2
OutputDryAir
Exhaust
InputWetAir
AirDryer
of theAdsorption
Fig,4.11Principle
Between10-20%of the dry
air passesthroughorifice02 and column2 in reversedirectionto re-adsorbmoisturetromthe desiccantto r€generateit,
The dry air entersthe saturatedchamberand expands(droppingthe temperaturefurth€r,makingthe dry
process),The regenerating
air €ffectively
evenmoredry to facililatethe regenerating
airllowgoesthento
by a timeror a sensorto altematelyallowthe
exhaust.Th€directionalcontrolvalveis switchedperiodically
supplyair to one columnand regsn€rating
the other,to providecontinuousdry air.
Extrem€lylow dew pointsare possiblewiththis method,for example- 40oC(whichis, oddlyenough,-40
"F).
A colorindicatormay be incorporated
in the desiccantto monitorthe degreeof saturation.Microlilteringis
essentlal on the dryeroutleito preventcarryoverof adsorbentmist.Initialand operatingcostsare
comparatively
high,but maintenance
costst6ndto be low.
DO NOT COPYWTTHOUTWRITTENPERMISSION
- 2 7-
P
E U m A T t cT E c H N o L o c Y
nel gerant drylng
Thisis a mechanical
unitincorporating
circuitandtwoh€atexchangers.
a retrigeration
Humidhightemperature
air is Dre-cooled
in the tirsl
heatexchangerO by
translerringpartol its heatto
the cooledoulpulair.
It is thencooledby the
retrigeratorprincipleof heat
€xtractionas a resultol
evaporatingFreongas in th6
refrigerator
circuit,in heat
exchanger@. At this time,
moistureand oil mists
condenseand are
automatically
drained.
The cold dry air retum
pipepasseslhroughair heat
exchanger@ and gainsheat
tromthe incominghigh
temperaturG
air. This
pr6v6ntsdew formingon the
dischargeoutlet,increases
volumeand lowersrelative
humidity.
DryAir OUT HotAir lN
O Heat Exchanger
inputair / outpulair
@ HeatExchanger
inputair / treon
@ Freoncooler
@ Ventilator(tor 3)
@ Freon
@ Thermostatic
@ Airfilter
@ Auto Drain
.i> Heat
Flg. 4.12 Principleof the Refrigerated
Air Dryer
Anoutputtemperature
ol 2oCis possible
by modemmethods,
although
an outputairtemperature
of SoCis
sufficient
tor mostcommonapplications
of compressed
air.lnlettemperaturos
maybe upto 60oCbutit is more
economical
lo precoolto runat lowerinlettemperatur€s.
As a generalrule,thecostof dryingcompressed
airmaybe 10.20%of thecostof compressing
air.
Thecostof notdryingcompressed
airis seenin increased
maintenance
of all pneumatic
components
us€d
in lhe system,pluslhe associated
increased
dowhtime,
farexceeding
thecostsof addinga dryingsystem.
DO NOT COPYWTTHOUTWRITTEN PERMISSION
P
EUMATICTECHNOLOGY
l V l a i nl i n e f i l t e r
A largecapacityfiltershouldbe installedafter
oil
the air receiverlo removecontamination,
and wat€rlrom the
vaporsfromthe compressor,
air. Properselectionmustbe sizedaccordingto
the systemflow.ln som€casesthereare lwo
mainlinefillers(onein reservesoryingas
backupduringthe filterelementchange-- which
shouldbe a r€gularlyscheduledmainlenance
item).
FillerCartridge
Bowl
Thisfiltermusthavea minimumpressure
dropandthe capabilityto removeoil vaporlrom
the compressorin orderto avoidemulsitication
(seenas a white,milkyliquid)
withcondensation
in the line.
It has no deflector,whichrequiresa certain
minimumpressur€dropto tunctionproperlyas
the 'StandardFiltei' discussedlaterin the
sectionon Air Treatment.A built-inor an
attachedaulo drainwill ensurea regular
waler.
dischargeof accumulated
Glass
DrainValve
Fi9.4.13TypicalLineFilter
The lilter is generallya quick-change
cartridgetype.
Notethat the propersystempositionfor this deviceis afterthe dryingsystem,notiust atterthe compressor.
[IR DISTRIBUTION
systsmcarryingthe air to the variousconsumors.
The air mainis a permanentlyinstalleddistribution
can be al th€irhighestlevels- whichfosters
Typicallyinstalledat the ceilinglev6l(whereth6 temperatures
processand
in the installation
entrainedmoisture),the air maincan be a tremendoussourceof contamination
duringnormaluse.
Duringthe installationprocesscars mustbe takento reducethe metalfilings,pipedope,and otherforeign
seem
materialsthal will be general€dfromassembly.The largesiz€of mostair mainsmakescontamination
is seenrelativeto the extremely
acceptable( a questionof relalivityat this point),yet whenthe contaminalion
in mod6mautomationcomponents(valves,actuators,gripp€rs.....)
the eflectcan be
smalltol€rances
disastrous.
(connecting
two buildings,p€rhapsbeing
It the air maincomesin contactwithoutsideair temperatures
routedunderground,
etc,)it will serveas a moistureproducer.
As manymainsare ironpipe,rustis the eventualby-product.Careful€xamination
shouldbe madewhen
reusingolderpipesto createa new airline.ll the opportunitypresentsitselfand a new airlineis to be cr6ated,
considerthe pipingconfiguration
as well.
Thereare two mainlayoutconligurations:
DEADENDLINEand RINGMAIN.Afterexamining4.14and
wouldbe prelerredfor bettersupplyflow.The
4.15it shouldbecomeapparentthat the Ringmainconfiguration
pip€)
but lhe advantagescan be enjoyedeverydayot
additionalcost is a one-timeconcem(lorthe additional
operation.
DO NOT COPYWTTHOUTWRTTTENPERMISSION
P
Eu Atrc TEcHNoLocy
-^
-...
i
:.._
.\.:..
( \ .
Flg. 4.14TypicalDeadEnd LineMains
To assistdrainage,the pipeworkshouldhavea slopeof about1 in 100 in the directionof flow and it should
be adequatelydrained.At suitableint€rvalsth€maincan b€broughtbackto its originalheightby usingtwo
longsweeprightangleb6ndsand arranginga drainleg at the low point.
RINGMAIN
:
,
t
I
a
i
!
....'
Flg.4.15TypicalRingMain
DO NOT COPYWITHOUTWRITTEN PERMISSION
P N E U A T T cT E c H N o L o G Y
Thaswlll reduce
In a ring mainsvstemmainair can be f€dtromtwo sidesto a pointol high consumption.
I pressur"diop. Howeverthis drivescondensatein anydirectionand sutftcientwatertake-otfpointswithAuto
Drainsshouldbe provided.lsolatingvalvescan be inslalledto dividethe air mainintosections.This limilsthe
ar€athat will be shul downduringperiodsof mainlenanceor repaar.
S E C O N D A R YL I NE S
Unlessan efficientaftercoolerand air dryerare installed,the compressedair distributionpipeworkacts as
a coolingsurfaceand wat€rand oil will accumulatethroughoutits length.
Branchlinesaretakenotf the top of the mainlo preventwaterin the mainpipelrom runningintolhem,
insteadof intodrainagetubeswhichare takentromthe bottomof the mainpipeat eachlow poinlof it. These
shouldbe trequentlydrainedor littedwithan automalicdrain.
The Waterremains
The Waterrunsintolhe
Auto Drain
Fig 4.15Take-ofistor air (a) and Water(b)
Autodrainsare mor6€xpensiveto inslallinitially,butthis is otfsetby the man-hourssavedin the operalion
of the
of the manualtype. With manualdrainingneglectleadsto compoundproblemsdue to contamination
the tub€guidesthe float,and is
inlernallyconnectedto atmospherevia the lilter,a reliefvalve,
holein the springloadedpiston
and alongthe stemof the manual
operator.
The condensateaccumulates
at the bottomof the housingand
whenil riseshighenoughto lift
the floatfrom its seal.the
pr€ssurein the housingis
transmittedto the pistonwhich
movesto the righlto openthe
drainvalveseatand expelthe
water.The floal thenlowerslo
Pressure
ReliefValve
Manual
Operation
Fig. 4.17 FloatTypeAuto Drain
shutotf the air supplyto the piston.
The reliefvalvelimitsthe pressurebehindthe pislonwhenthe floatshutsthe nozzle.This pre-setvalue
ensuresa consislentpistonre-settingtim6as the capturedair bleedsotf througha tunctionalleak in th€ reliet
valve.
DO NOT COPYWTTHOUTWRITTENPERMISSION
-31 -
P N E U A T T cT E c H N o L o c Y
Fig4.18showsan electricallydriventype,whichperiodically
purgesthe condensateby a rotatingcam
wheeltrippinga lever-operated
poppetvalve.
It otfersthe advanlag6s ot beingableto
work in any orientalion
and is highlyresistant
to vibration,so lending
ilseltto use in mobile
compressors,
and bus
or lruck pneumatic
systems.
Fig. 4,18 MotorizedAuto Drain
S I Z I N GC O M P R E S S E D
AIR MAINS
The cost of air mainsrepresentsa highproportionof the initialcost of a compressedair installation.A
reductionin pipediameter,althoughloweringthe investmentcost,will increasethe air pressuredrop in the
system,potentiallythe op€ratingcostswill riseand will exceedthe additionalcost of th€largerdiameter
piping.
Also,as laborchargesconstitutea largepartof the overallcost,and,as this costvariesvery littlebetween
pipe sizes,the cost of installingsay a 25 mm Dia borepipe is similarto that ol a 50 mm Dia pipe. Butthe flow
capacityof the 50mmDia pipewill be tourtimesthat ot 25 mm pipe.This additionalvolumemay equaltwo or
thre€(or more)receivertank volumes,reducingcompressordutycycles.
In a closedloop ring mainsystem,the supplyfor any particulartake-otfpointis fed by two pipepaths.
Whendeterminingpipesize,this dualfeedshouldbe ignored,assumingthat at any time air will be supplied
throughone pipeonly.
The sizeof the air mainand branchesis determinedby th€limitationof th€air velocily,normally
recommended
at 6 m/s,whilesub-circuitsat a pressureof around6 bar and a few mete6 in lengthmaywork
at velocili€sup to 20mls. The pressuredropfromthe compressorto the end of the branchpipe shouldnot
exceed0.3 bar.The nomogram(figa.l9) allowsus to determineth€ requiredpipe diameter.
Bendsand valvescauseadditionalflow resistance,whichcan be expressedas additional(equivalent)
pipe
lengthsin computingthe overallpressuredrop.Table4.20Oivesth€equiva6ntlengthsforthe variousfittings
commonlyused.
Example(a) To det€tminethe sizeot pip6thatwill pass 16800Uminol free air with a maximumpressuredrop
of not morethan 0.3 bar in 125 m ot pipe.The 2 stagecompressorswitcheson at 8 bar and stopsat 10
bar;the av€rageis 9 bar.
3o kPa pressuredropin 125 m of pipeis equivalentto
ffi
=o.24 kpaI m.
Refeningto Nomogram4.19:Drawa linefrom 9 baron the pressureline through0.24 kPa/ m on the
pressuredrop lineto cul lhe referenc€line at X.
Join X to 0.28m3n/s and drawa lineto intecectthe pipesize linesat approximat€ly
61 mm.
Pipewitha minimumboreof 61 mm can b€used.a 65 mm nominalborepipe (seeTable4.21)has a
boreol 68 mm and wouldsatisfythe requirements
withsomemargin.
Example(b) lf th€ 125 m l€ngthof pipe in (a) abovehas a numberof littingsin the line,e.g.,two elbows,two
90" bends,six standardteesand two gatevalves,will a largersiz€pipe be necessaryto limitthe
pressuredropto 30 kPa?
DO NOT COPYWTIHOUT WRITTENPERMISSION
P N E U M A T I CT E C H N O I O G Y
In Table4.20,column"65 mm Dia',we findthe lollowingequivalentpipelength:
2.8m
2. 1.4m
twoelbows:
=
1 . 6m
six standardlees:
2'0.8 m
6 . 0.7 m
=
4.2m
two gatevalves:
2 . 0.5 m
=
1 . 0m
two90obends:
Total
9.6 m
10 m additionalpipelengthThe twelvefittingshavea flow resistanceequaltoapproximately
The "E rectiveLength"ot the pipeis thus 125+ 9.6 -135 m
= 022 kPa/ m
and the allowed4p I r, *#P
r35 m
Relerringagainto nomogramin fig 4.19:The pipesize linewill now cut at almoslthe samedia;a
nominalborepipeot 65 mm,withan actualinnerdiameterot 68 mm will be satistactory.
Note:
Th6 possibilityof futureair demandsshouldbe taien intoaccountwhendeterminingthe sizeof mainsfor a
new installation.
DO NOT COPYWITHOLITWRITTENPERMISSION
-3{}-
P
E u f r t A T t cT E c H t r t o L o c Y
J
2
1.5
1
2.O
1.75
0.5
o.4
1.5
6
7
..-8
1.0
0.9
0.8
o.7
0.6
0.3
6t
1.5". 40
, , o . 1 . .25! 35
0.5
9:
0.4
10
11
'12
o.3
0.25
o::.
0.15
"p
kPa/m
= bar/100m
PipeLength
Flg. 4.19 Nomogramfor Sizingthe MainsPipeDiameter
DO NOT COPYWTIIJOUT WRITTEN PERMISSION
0.05
0.04
0.03
o.025
0.02
0.015
0.01
P N E U M A T I CT E C HN O L O G Y
Type of Flttlng
Nominalplpe 6lze (m!n)
65
40
50
30
1.4
0.8
l
.
l
0.5
0.7
0.4
0.3
0.8
0.6
0.5
0.4
0.2
0.3
0.1
2.6
3.0
1.6
1 . 8 ?.2
1.0
1.2
t.1
2.0
t.2
l.l
0.8
0.5
0.6
4.0
3.4
2.0
2.4
l.l
0.8
0.4 0 . 5
0.3 0.3
0.1
0.2
0.1
0.5
0;l
0.4
0.4
o.2 0.2
0.1
2.7
1,6
2.1
1.4
0.5
0.7
0.9
main
fittings
tor
lhe
Pipe
Lengths
Table 4,20 Equivalent
t5
Elbow
90' Bend(lono)
90' Elbow
180' Bend
GlobeValve
GateValve
StandardTee
SideTee
20
25
80
1.8
0.9
5.2
0.6
0.9
100
2.4
1.2
5.4
125
3.2
1.5
7.1
4.1
9.4
0.9
t.z
t.2
t.5
4.1
6.4
Materlels for Ptplng
Standard Gas Pipe (SGP)
The air mainis usuallya steelor malleableiron pipe. This is oblainablein blackor galvanizedlorm, which
is lessliableto corrode.Thistype of pipingcan be screwedto acceptthe rang€of proprietarymalleable
fittings.For over80 mm Dia,weldedflangesare oflenmoreeconomicalto installralherthancut threadsinto
largepipes.The specifications
ol the CarbonSt6elStandardGas Pipe(SGP)are:
Nominal Width
B
6
l/8
8
v4
l0
3/8
tn
Outside Dia.
mm
10.5
13.8
Thicknesc
mm
2.0
I t.J
25
3?
40
Iv4
I ltz
48.6
50
65
2
2|n
60.3
2.8
2.8
3.2
3.5
3.5
3
76.1
88.9
114.3
3.65
3.65
4.05
45
l5
20
75
100
3t4
21.7
27.2
34.O
Mass
ks/m
0.4t9
0.652
0.851
1.310
1.680
2.430
3.380
3.890
5.100
6.510
8.470
12.100
T a b l e 4 . 2 1 P i p eS i z e S p e c i t i c a t i o n
Stainless steel pipes
Th€seare primarilyusedwhenvery largediametersin longstraightmainlinesare required.
Copper Tube
Wherecorrosion,heatresislanceand highrigidityar€required,coppertubingup to a nominaldiameterof
40 mm can be used,but will be relativelycostlyovet28 mm. Dia. Compression
fittingsusedwith annealed
qualitytubingprovideeasyworkingtor installation.
DO NOT COPYWTIHOUT WRITTENPERMISSION
-35-
P N E U M A T t cT E c H N o L o c Y
FlubberTube ("Air Hose")
Rubberhoseor reintotced
plasticis mostsuitable
tor airactuaiedhandloolsas it otterstlexibility
tor
treedomof movement
tortheoperalor.
Thedimensions
of pneumatic
RubberHoseare:
Nominal Width,
inches
v8
v4
3/8
tn
5/8
3t4
I
1u4
I ltz
1 3t4
2
2lt4*
2 v2*
OutsideDia.
Mm
lnside Dia.
mm
9.2
10.3
t8.5
2t.7
74.t0
29.0
3.2
6.3
35.4
45.8
a<A
52.1
60.5
66.8
8 1 l.
90.5
Inner SectionalArea
mm2
8.04
9.5
t2.7
t5.9
19.0
31.8
38.1
44.5
50.8
57.r
31.2
70.9
r27
t99
284
507
794
I140
1560
2030
25ffi
63.5
3170
fable 4.22 RubberhoseSpecitication.
Ctorh-wrapp€d
hose
*Rubberhoseis mainly
recommended
for toolsand olherapplicationswherethe tub€is exposedto
m€chanical
wear.
Plastic tubing
Commonlyusedfor the interconnection
of pneumaticcomponents.
Withinils workingtemperature
limitationsit hasobviousadvantagestor installation,
allowing€asycuttingto length,and rapidconnectionby
eithercompressionor quick-fitfinings.
greatertl€xibilityfor tighterbendsor constanlmovementis required,a softergradenylonor polyurethane
. lf
is available,but it has lowermaximumsafeworkingpressures,Be awarethat its o.D., nofits intemal
dimension,callsout tubing.A %"tube hasa typicall.D. of only0.12S".
DO NOT COPYWTHOTJT WRITTENPERMISSION
-36-
P N E U l , t a T l cT E c H N o L o G Y
Flttlngs ln Systems
byvariousmethods
pneumatic
areconnected
componenls
In systems,
The INSERTtype providesa reliable
retainingforceinsideand oulsideof the
tub€.The sleevepressesthe tubewhen
screwingin th€cap nut. The tube (inserl)
enteringintothe tube reducesits inner
diameterand thus represenlsa
extraflow resistance.
considerabl€
Insertsleevesare not reusable.
Fig. 4.23 Exampleof an lnsertFitling.
The PUSH- lN connectionhasa large
retainingforceand the useof a special
profilesealensurespositivesealingfor
pressureand vacuum.Thereis no additional
as the connectionhasthe
flow restriction,
sameinnerflowsectionas the inner
diameterof th€fittingtube.
Reusablelor hundr€dsof inserlions.
Flg.424 Exampleof a Push-inFitting,elbowtype
The SELF-SEALING
fittinghas a builtin
mechanismso that air doesnot exhaust
atterremovalof the tube and is also
applicablefor copperfree applications.
a. lf no tube is push€din, a check
valveshutsotf the fitting.
b Whena tube is inserted,it opens
lhe air flow by pushingth6 chec*valve
from its seat.
Flg. 4.25 Exampleof a Self-SealFitting.
DO NOT COPYWTTHOUTWRITIEN PERMISSION
P
E U r r A T t cT E c H a { o L o c Y
5 AIRTREATMENT
moisture
air carriesbothdustand moislure.Aftercompression,
As describedpreviously,all atmospheric
will
be
caried
over.
that
condens€sout in the aftercoolerand receiverbut therewill always bo some
Moreovertineparticlesof carbonizedoil, pipescaleand otherforeignmatter,suchas wornsealingmaterial,
All of this is likelyto haveinjuriouseffectson pneumaticequipmentby increased
tormgummysubstances.
sealand componentwear,seal expansion,corrosionand stickingvalves.
the air shouldbe furthercleaned(tiltered)as nearas possibleto the point
To removBthesecontaminants,
Lubrication'
also
includes
Pressure
Begulationand occasionally
Air
treatment
ol use.
FILTERING
S T A N D A R DF I L T E R
The standardtilteris a combinedwaterseparatorand lilter. It the air has not beende-hydraled
quantityof waterwill be collectedand the lilter will holdbacksolidimpuritiessuch
beforehand,
a considerable
as dustand rustoarticles,
CleanAir
PilotValve
Baffle Plate
DrainValve
QuietZone
Bowl
BowlGuard
-.'i\.7
DrainValve
Symbol
SymbolFilter/Separator
Filter/Separator
with Auto Drain
Fig. 5.1 TypicalFilter/Water
Separatorand an AutomaticDrainas option
The waterseparationoccursmainlyby a rapidrotationof the air,causedby the detlector at the inlet. The
heavierparticlesot did, walerand oil arelhrownoutwardsto impaclon the wall of the ftlterbowlbetore
runningdownto collectat the bottom.The liquidcanthenbe drainedoff througha manualdraincock or an
the separatedliquid
automaticdrain.The baffle plate createsa quietzonebeneathth€swidingair, pr€venting
intothe air stream.
frombeingre-entrained
DO NOT COPYWTIT{OUTWRITTENPERMISSION
P N E U A T T cT E c H N o L o c v
The filterelementremoveslhe tinerparticlesof dust,rust scaleand carbonizedoil as the air flowsthrough
to the oullel. The standardelementwill removoall contamination
Darticlesdownto 5 micronsin size. Some
elomentscan be easilyr€moved,cleanedand re-useda numberof tim€sbetoreneedingto be r€placed
becauseof excessivepressuredrop.
The bowlis normallymadefrom polycarbonate.
For satetya metalbowlguardmustprotectit. For
chemicallyhazardousenvironmenlsspecialbowl materialsmustbe used.Wherethe bowlis exposedto heat,
sparkselc, a metalbowlshouldbe used.
lf the condensateaccumulatesat a highrateit is desirableto provideautomaticdraining.
The righthandside of Fig.5.1 showsa floattype of autodrainunitbuilt-infor standard,ilter.
Micro Filters or Coalesc€rs
Wherecontamination
by oil vaporis undesirable,
a micro-tilteris used.Being
a Durefilterit is not
equippedwith a detlector
ptate.
Filt€ringTissue
0.3 pm
The alr tlows from the
inlet to the center of th€
fllter cartridge then outwards through the outlet.
Dustis trappedwithin
the microfilterelement,the
oil vaporand watermistis
conv€rtedintoliquidby a
coalescingactionwithin
the lilter material,torming
dropson the filtercartridge
lo collecl at th€ bottomof
the bowl.
Sub-microFiltfrs
A sub-microfilterwill
removevirtuallyall oil and
waterand alsoline
Particlesdownto 0.01of a
micron,to provide
maximumprotectionfor pn€umaticprecisionmeasuringdevices,electrostatic
spraypainting,cleaningand
dryingot electronicassembliesetc -- the principleof operationis the sameas a microlilter,but its fifur
elementhas additionallayerswitha higherliltrationefficiency.
Filter Selection
The sizeof air filterlhat is requh€dtor a particularapplicationis dependenton two factorsi
a) The maximumflow of compressedair usedby the pneumaticequipment.
b) The maximumacceptablepressuredropfor the application.
provideflowpressurediagramsto enablecorrectsizingto be done.
Manufacturers
DO NOT COPYWNHOUT WRITTEN PERMISSION
-39-
PNEU$ATIC TECHNOIOGY
, lt shouldbe notedthat usinga standardfiltertor the applicationmightnot separateas etficientlybecauseof
I a lowerflowvelocity.
A ! FO U A L I T Y
:ILTEBINGLEVELS
Fig5.3 illustratesditferentlevelsof purityfor variousapplications.
Air froma compressorpassesthroughan aftercoolerwithan autodrainto removecondonsate.As the air
coolslurtherin the air receiver,an autodrain,installedon the bottomremovesmoreoondensale.Additional
drainsmay be tittedto all low pointson the pipeline.
The svslemdividesintothreemainparts:
Branches(1 and 2)
provideair directlrom the
air receiver.Branches(3 6) useair conditionedby a
type ot dryer.
retrigerated
an
Branch7 incorporates
additionaldryerot the
adsorptiontype.
Refdgerated
AirDryer
Standardfiltersin sub
Compressor
branchesI and 2.
equippedwithautodrains
removecondensate:
subbranch2 beinghigher
buritybecauseof th€
a MicroFilter
microtilter. Subbranches
dry
3 5, use refrigerated
b Sub-microFilter
air.Thus.branch3
c OdorRemovalFilter
requiresno autodrain,
branch4 needsno pre
d AdsorbtionAir
lihe ng and branch5
givesan improvedlevelot
air purityusinga micro
filterand sub microfilter,
the moisturehavingbeen
removedby a refrigerated
typeof air dry6r.
3
4
5
6
7
Flg. 5.3 SchematicDelinitionof 7 Degreesof Filtration
an odor r€movalfilter.An adsorptiontypedryereliminatesall risk of
Sub branch6 incorporates
at lowlemp€ratures
in sub branch7.
condensation
Typical applicationsare listed in Table 5.4.
DO NOT COPYWTIHOUT WRITTENPERMISSION
-40-
P N E U M A t I cT E C H N O L O G Y
Number
Removalof:
Dustpanicles>5F Liquid oil
>99%Sarurated
humidity
46%.
Dustpanicles>0.31rOil misr
>99.9%
Saturated
humidity99%.
Humidityto an aunospheric
dewpointof -l7'C
Funherasin (l ).
Dustpanicles>0.3uOil mist
>99.9%Humidityup to an
atmospheric
dew pointof
Application
Wheresomesolid impurities,
humidityandoil canbe
acceDted.
Wberetheremovalof dustand
bui a cenain
oil dominaaes,
canbe
amountof condensation
risked.
Wherethercmovalof humidily
is imperativebut tracesof fine
dustandoil areacceDtable.
Whereno hurnidity,fine dust
andoil vaporareacceptable.
-t7"c.
Typical Examples
Workshopair for clamping,
blowing,simplepneumatic
drives.
Generalindustrialequipment
pneumaticconirolsanddrives
metallicjoints, air
Sealless
toolsandair motors.
Similarto (l) but asthe air is
dry additionally generalspray
Daintins.
Processcontrol,measuring
equipment,high qualityspray
painting,coolingof foundry
andinjectionmoldingdies.
Dust particles>0.01U
Oil mist >99.9999%Humidity
as(4).
Where purc air, practically free Pneumaticprecisionmeasuring
from anyimpurityis required. devices,electrostaticspray
painting, cleaningand drying
of electronicassemblies.
as(5) with additionalodor
Whereabsolutelypurc air, as
Pharmacy,food industdesfor
removal.
packaging,air transportand
in (5), but odor freeair is
brewing.Breathineair.
reouircd.
all impuritiesasin (6) but with Whereevery risk of
Drying electroniccomponenb
an atmosphericdew point
s
condensation
duringexpansion Storageof pharmaceutical
below-30" C.
Marine measuringequipment
and at low temperaturesmust
be avoided.
Air transportof powder.
Table 5.4 Definitionand typicalapplications
of the sevenqualitiesof air
DO NOT COPYWTTHOUTWRITTENPERMISSION
P N E U T / t A T I CT E C H N O L O G Y
b n e s s u n eR E G U L A T T o N
rapidwearwilltakeplacewilh
aboveoptimum,
at pressures
is necessary
becausa
Regulation
o{ pressure
it resultsin poorefficiency.
because
pressure
too
low
is
uneconomical
is
littleor noincrease
that
in output.Air
S T A N D A R DR E G U L A T O R
AdiustingKnob
Pressureregulatorshavea pislonor
diaphragmto balancelhe outputpressure
againstan adiustablespringforce.
The secondarypressureis set by lhe
adiuslingscrewloadinglhe settingspringto
holdthe mainvalveopen,allowingllow from
the primarypressurepl inlelportlo the
secondarypressurepz outlotport.Thenthe
pressurein the circuilconnectedto the outlel
risesand actson the diaphragm,creatinga
littingforceagainstthe springload.
Whenconsumption
starts,pAwill initially
dropand the spring,momentarily
stronger
than the liftinglorce {rom p2 on th€
diaphragm,opensthe valve.
Adjusling
Spindle
SettingSpring
Diaphragm
p2
PI
alve Spring
Fig 5.5. Principleot the PressureRegulator
lf the consumptionratedrops,p2 willslightlyincrease,this increasesthe forceon the diaphragmagainst
the springforce-- diaphragmand valvewillthen lift unlillhe springforceis equaledagain.The airflowthrough
the valvewill be reduceduntilit matchesth6 consumplionrateand the outputpressureis maintained.
lf the consumptionrateincreases,p2 will slightlydecrease.This decreasesthe forceon lhe diaphragm
againstthe springtorce,diaphragmand valvedropuntilthe springforceis equaledagain.This increaseslhe
airflowlhroughthe valveto matchthe consumptionrate.
Withoul air consumF
tion the valv€is closed.lf
the secondarypressur€
risesabovethe set valu€
by virtueot:
. re-settingthe
regulatorto a loweroutlet
pressure,or
. an eliemal r€verse
thrustfroman actualor,
the diaphragmwill liftto
openth€relievingseatso
thal excessoressurecan
be bledoff throughthe
vent holein the rigulator
body.
DoNOTrelyonthis
orificeas anexhaust
flow
Path.
I
Believing
P1
a
b
Fig. 5.6 RelievingFunction
DO NOT COPYWITHOUT WRTTTENPERMISSION
-42-
P N E U M A T I cT E C H I t o L o G Y
Wilh v€ryhighllow ratesthe valveis wide
open.The springis ther€toreelongatedand lhus
weakerand the equilibriumbetweenp2 on th€
diaphragmareaand the springoccursat a lower
level.This problemcan be corr€ct€dby creatinga
thirdchamberwitha conneclionlo lhe outout
channel.In thischanneltheflowvelocityis high.
As €xplainedin section3, the staticpressureis
then low (Bemoulli).As pOis nowat a lowerstatic
pressure,the balanceagainstlhe weakened
springal highflow ratesis compensated.
The etfectcan be improvedby insertinga tube
in the connection,cut at an anglewiththe opening
orientedtowardsthe outlet(fig 5.8).
p1
Fig. 5.7 Principleof a FlowCompensated
Regulator
Thereis stillan inconvenience
in the regulator
of fig. 5.7: if the inletpressurepl increases,a
higherlorce is actingon the bottomof the valve,
tryingto closeit. That meansthat an increasing
inputpressuredecreasesthe outputpressur€and
vice ve6a. A valvehavingequalsurfaceareasfor
bothinputand outputpressurein bothdirections
can eliminatethis.This is realizedin the regulator
of fig. 5.8
The mostimportanlparlsar€:
(O Adiustingspindle
@ SettingSpring
O RelievingSeat
@ Diaphragm
@ FlowComoensation
Chamoer
(D FlowCompensation
ConnectionTube
O vatve
@ O-Ringlor Pressur€Compensation
0 ValveSpring
@ O-Ringfor FtowCompensation
Flg. 5.8 FullycompensatedPressure
Regulator
DO NOT COPYWTII{OI]T WRITTENPERMISSION
- 43-
PNEU ATtc TEcHNoLoGY
I L O T O P E R A T E DR E G U L A T O R
The piloloperatedregulatoroftersgreateraccuracyof pressureregulationacrossa largetlow rang6'
Thisaccuracyis obtainedby replacingthe seningspringot a standardregulatorwith pilotpressurelrom a
smallpilotregufdorsit6don the unit.
The pilotregulatoron top ol the unitsuppliesor exhaustspilotair onlyduringcorrectionsof the oulput
pressure.Thisenablesthe regulatorto achievevery highllow ratesbut ke6psthe settingspringlenglhto a
minimum.
SettingSpring
PressureRelief
PilolDiaphragm
PilotValve
Diaphragm
P1
MainValve
MainValve
MainSecondary
Pressure
Reliel
Flg 5.9 PilotPressureRegulator
DO NOT COPYWTTHOUTWRITIEN PERMISSION
P N E U M A T T cT E c H N o L o c y
F I L T E F . R E GU L A T O R
Air filleringand pressureregulationis combin€din the
singlelilt€rregulatorto providea compactspac€savingunit.
Charccterlstlcs
A regulatorsizeis selectedto give the flow requiredby the
applicationwitha minimumol pr€ssurevarialionacrossthe
tlow rangeot the unit.
Manufacture6providegraphicalinlormationregardingthe
tlow characteristics
ol their€quipment.
Th€mostimportantis
the Flow/ pA diagram.lt showshow pA decreaseswith
increasingflow.(Fig.5.11).The curvehasthreedistinct
portions:
1. the inrush,witha smallgap on the valvethat doesnot
yel allowrealregulation
2. the regulationrangeand
3, the saturationrange;lhe valveis wideopenand further
r€gulationis impossible
p 2 ^
(bar)o
a
(bar)
6
0
2000
4000
>
6000
O (l/min)
Fig 5.10 Typical Filter Regularor
Flg.5.11 TypicalFloWPressure
Chancteristics:
a: Regulator,b: Filter
DO NOT COPYWTTHOUTWRITTEN PERMISSION
P N E U M A T T CT E C I I N O L O G Y
S I Z I N GO F B E G U L A T O R SA N D F I L T E F S
I
FRLelementshaveto be sizedin accordancewiththe requiredflowcapacity.For Regulalols,lhe average
range(ll in ti9.5.11a).Thesizeof lhe tilteris
volumellowshouldbe theonein the middleot the regulating
" (nota Line Filte0,a minimumpressuredrop
definedby the pressuredrop,For a'StandardFilter/Separator
With maximumflow,AAp (allowableor desirabledeltap)
of about0,2 bar is requiredto €nsurefunctioning.
shouldhoweverb€keptbelow1 bar.
The sizeis theretoredetinedby the requiredflow,not by the connectionsizeof the component.Modular
systemsgivethe capabilitylo adaptthe connectionthreadto lhe availablelube size.
} O M P B E S S E DA I R L U B R I C A T I O N
Lubricationis no longera necessityfor the majorityof modernPneumaliccomponentsare availableprelubricatedfor life.
of modemhighcycling
The life and performance
of thesecomponentsare tullyup to the requirements
processmachinery.
The advantagesol "non-lube'systemsinclude:oil levels.
a) Savingsin the cost ol lubricationequipment,lubricatingoil and maintaining
b) Cleanermorehygienicsystems;of particularimportancein foodand pharmaceutical
induslries.
for a healthier,saferworkingenvironmenl.
c) Oilfree atmosphere,
To 6nsurethey are continuallylubricated,a certainquantityof
Certainequipmentstillr6quireslubrication.
is
to
the
compressed
by
means
of
a lubricalor.
oil added
air
' R O P O R T I O N A LL U B R I C A T O R S
to lhe flow rate,
ln a (proportional)
lubricatora pressuredropbotweeninletand outlet,directlyproportional
is crealedand littsoil fromthe bowlintothe sightfeed dome.
With a tixedsizeot restriction,
a greatlyincreasedflow ratewouldcreatean excessivepressuredropand
producean air/oilmixturethat had too muchoil,{loodingthe pneumaticsystem.
Converselya decreasedflow ratemaynol createsufficientpr€ssuredropresultingin a mi)durewhichis too
lean.
crosssectionslo producea conitant
To overcomethis problem,lubricatorsmusthaveself-adiusting
mixture.
Air enleringa lubricator(as shownin Fig 5.12)followstwo paths:it llowsov€rthe dampervaneto the
outletand also entersthe lubricatorbowlvia a checkvalve,
Wh6nlhereis no flow,the samepressureexistsabovethe surfaceot the oil in th€bowl,in the oil tubeand
the sighlteeddome. Consequ€ntly
thereis no movementof oil.
Whenair llowsthroughthe unit,lhe dampervaner€strictorcausesa prgssuredropb€tweenthe inletand
outlet. The higherthe flow,the greaterthe pressuredrop.
zon€immediately
Sincethe sightleed domeis connectedby the capillaryholeto the low-pressure
afterthe
pressure
vane,
the
is
lower
than
that
in
the
bowl.
damper
in the dome
This pressureditferenceforcesoil up the tube,throughthe oil checkvalveandJlowregulatorintothe
dome.
Once in the dome,the oil seepsthroughthe capillaryholeinlo the mainair streamin the areaof the
highestair velocity.The oil is brokenup into minusculeparticles,atomizedand mixedhomogeneously
withthe
air by the turbulencein the vortexcreatedby the dampervane.
WRITTENPERMISSION
DO NOT COPYWTTHOLTT
-46-
P
EU ATtc TEcHNoLoGY
FletlllPlug
SightFeedDome
Capillary
Conn€ction
Oil Thronb
CheckValv€
DamoerVane
Oil Tube
BowlGuard
SinteredBronze
Oil Filler
Fig 5.12 Proportional
Lubricator
The dampervaneis madelrom a flexiblematerialto allowit to bendas flow increases,wideningthe tlow
path,to proportionally
adjustthe pressuredropand thus maintaina constantmixturethroughout.
The oil throttleallowsadjustm€ntof the quantityot oil tor a givenpressuredrop. The oil checkvalve
retainsthe oil in the upperpart ot th€tubewhenthe air flowt€mporarily
stops.
The air checkvalveallowsthe unitto be refilledunderpressure,whileworkcan normallygo on.
The conectoil feed ratedependson operatingc-onditions;
but a g€neralgude is to allowone or two drops
per cycleof th6 machine.
A pure(no-additives)
minoraloil of 32 c€nti-stokes
(lSO standardVG32).Some
viscosityis recommended
oil companieshavea specialoil tor compressedair lubrication,
with a highcapacityto absorbmoislurewithout
lossof lubricatingproperties.
DO NOT COPYWNHOI}T WRITIEN PERMISSION
-47-
P N E U I , A T I CT E C H N O L O G Y
Lub.lcator
I' F . R . L .
UNITS
Modulartilter,pressureregulatorand lubricator
elementscan be combinedintoa serviceunitby
joiningwithspacersand clamps.Mounting
can be easilyfitted
bracketsand olheraccessories
in morerecenldesigns.
SlZE AND INSTALLATION
The combinalionunitmuslagainbe sizedfor
the maximumtlow rateof the system.
Manulaclurers
willgenerallyprovidethis
information.
Mostsystemsrequirean approvedshul-otfor
lockoul valve.ln addition,thereare doviceslhat
allowan EmergencyStoptunctionand a slowslart
option,whereair is introducedto lhe syst€mat a
reducedrate.
Flg. 5.13 TypicalFBL Unitin a modular
design
instruclions.For
Forconectplacementand operalionof thesedevicesconsultthe manufacturers'
th€reshouldbe a way to stopair flowatterthe F.R.L.unitand belorethe unit,isolatingthe F.R.L.
maintenance
for repair.In mostcases,the EmergencySlopshouldbe downslreamo{ the F.R.L,to preventbacKlowing
(reverseflow)the filter(whichcouldcauseelementcollapse),the regulator(diaphragmcouldbe damaged),
andthe lubricator(drivingoil mistinsidethe tilterelement).
DO NOT COPYWITHOI.JTWRITIEN PERMISSION
PNEU ATtc TEcHNoLocY
6 ACTUATORS
by piston
is obtained
canbelinearor rotary.Linearmovement
Theworkdoneby pneumatic
actuators
pinion
type
actuators
and
rack
and
vane
or
to
270'
by
up
reciprocating
rotary
motion
wilh
an
angle
rylinders,
continuous
rotation
by airmotors.
I N E A RC Y L I N D E R S
Pneumaticcylindersof varyingdesignsare the mostcommonpowercomponentsusedin pneumatic
are derived:
Thereare lwo basictypesfromwhichspecialconslructions
automation.
. Singl€-acting
cylinderswithone air inl€tto producea pow€rstrokein one direction
. Double-aciing
cylinderswilh two air inletsto produceextendingand relractingpowerstrokes
I N G L E A C T I N GC Y L I N D E F
A singleactingcylinderdevelopsthrustin one directiononly.The pistonrod is retumedby a fittedspringor
by externalforcefromthe loador spring.
It maybe a 'push'or 'pull"type(lig6.1)
SinteredBronzeFiller
Stoo
Spring
Fig. 6,1 TypicalSingleActingCylinder,SpringRetractedor'Push" type
Singleactingcylindersare usedlor clamping,marking,eiectingetc. Theyhavea somewhatlowerair
consumption
comparedwiththe equivalentsizeot doubleactingcylinder.Howeverthereis a reductionin
thrustdue to the opposingspringforce,and so a largerboremay be required.Alsoaccommodating
the
springresultsin a longeroveralllengthand limitedstrokelength.
O U B L E A C T I N GC Y L I N D E R
Withthis actuator,thtustis developedin bothelitendingand retractingdirectionsas air pressureis applied
alternatelyto oppositesidesof a piston. The thrustavailableon the retractingstrokois reduceddue to the
smallerettectivepislonarea,but is onlya consideration
if the cylinderis to 'pull' the sameload in both
dir€ctions.
Rod Seal/
Rod
ISOSymbol:
Fig. 6.2 DoubleActingCylinder
DO NOT COPYWTTHOUTWRITTENPERMISSION
P
EU ATtc TEcHNoLocy
Cyllnder Constructlon
The conslructionol a doubleactingcylind€ris shown. The barrelis normallymadeot s€amlesstubewhich
may be hardcoatedand super-finished
on ths innerworkingsurfac€lo minimizewearand friction.The end
caps maybe aluminumalloyor malleableironcastingsheldin placeby tie rods,or in the caseot smalle!'
cylinders,fil intothe barreltube by screwlhreador be crimpedon. Aluminum,brass,bronzeor stainlesssteel
may be us6dtor the cylinderbodyfor aggressiveor unsafeenvironments.
Seal
Guiding
or Wear
Pislon
Magnetic
Cylinder
Ring
Seal
Ring
Barrelor
Frontor RodCover
Backor
Head
Cover
Tube
ScraperRing/
Bod-Seal
Blind
End
Rod End
PistonRod
t
L
1
(
ISO Symbol
CushionSeal
Cushion
Barrel
Tie Rod
Tie Rod Nut
Flg. 6.3 the componentpartsof a doubleactingcylinderwithair cushioning
Varioustypesof sealsensurethat the cylinderis airtight.
Cushlont ng
Pneumaticcylindersare capableot very highsp€edand considerable
shockforc€scan be d€v€lop€d
on
the end of the stroke.Smallercylindersotlenhavefixedcushioning,i.€.rubberbufters,to absorbthe shock
and preventinternaldamageto the cylinder.Oh largercylinders,the impactetfectcan b€absorb€dby an air
cushionthat deceleratesthe pistonoverthe lastportionof the stroke. This cushiontrapssomeof the
exhaustingair nearthe end of the strokebeforeallowingit to bleedoft moreslowlythroughan adjustable
n€edlevalve(fi9.6.4).
Fig. 6.4 Principleof the Air Cushion
DO NOT COPYWTTHOUTWRITTENPERMISSION
-50-
PNEU ATtc TEcHNoLoGY
1 The normalescapeof the exhaustingairto the outletportis closedoft as the cushionpistonentersthe
fcushion
restriction
Port.Thetrappedair is
seal,so thattheair canonlyescapethroughme adjuslable
piston.
to a relativelyhighpressure,whichbrakesthe inertiaof the
compressed
Whenthe pislonreverses,lhe cushionsealacts as a checkvalveto allowairflowto the piston.lt howover
of the piston.The cushioningstrokeshouldthereforebe as
restrictsthe air flowand delaysthe acceleration
possible.
shorlas
To decelerateheavyloadsor highpistonspeeds,an extemalshockabsorberis required.It the piston
speedexceedsabout5OOmrn/san externalmechanicalstop mustb€provided,whichis alsothe casewith
built-incushioning.
S P E C I A LC Y L I N O E RO P T I O N S
,ouble Rod
ISOSymbol
Fig. 6.5 Principleof lhe doublerod
A doubl€rod makesa cylinderstrongeragainstside load,as it hastwo bearingsat the widestdistance
possible.Thistypeof cylinderis ottenmountedwiththe rodstixedand the cylinderitselfmovingto displacea
oart.
ton Botatlng Rod
The pistonrod of a standardcylinderrotatesslightlyas thereis no guideto prevontthis.Thereforeit is not
possibleto directlymounta tool,e.g.a cuningblade.
Forlhis kindof application,
wh€reno
considerable
torqueis exercis€don the tool,a
cylindGrwithnon-rotating
rod can be used.The
suppliersspecitythe maximumallowabletorque.
As tig. 6.6 shows,lwo flat plan€son the rod and
a fittingguidepreventthe rotation.
It showsalso howa torquecrealesa high
forceon the edgesof the rod profile,whichwill
damageit in the longrun.
DO NOT COPYWITHOLTTWRITIEN PERMISSION
P N E U $ A T r cT E c H N o L o c Y
Twln Rod
Thistype o, cylindgrhas a highlateralload resistanceand highnon-rotatingaccuracy.Thesecompactdual
rod cylindersare of highprecisionand idealfor pickand placeoperations.Do not assumethatthe dual
cylinders€qualthetheoreticalforceof ong largercylinder'stheoreticalforce,€,9.two 25 mm.boresin a dual
rod cylinderproducehalfthe torceol one 50 mm borecylinder(provethisto yourselt).
Sectlon A-A
Symbol;
Unofficial:
rso:
A
-'-+i
Fig. 6,7 Twin RodCylinder
FIet Cylinder
A cylindernormallyhas squarecoversand,generally,a roundcylinder.By stretchingthe pistonto a
relativelylong rectangularshapewith roundends,it achievesthe sameforceas a conventionalcylinder.The
advantage,of course,is the savingin spaceachievedif they are to be stackedtogeth€r.Suitablefor mostnon
rotatingapplications.
SectlonA-A
rsosymbor,Fll
Flg. 6.8 Principleof a FlatCylinder
Tandem Cylinder
A tandemcylinderis two doubleactingcylindersioinedtogetherwith a commonpistonrodto form a single
unit.
ISO Symbol:
Fig. 6.9 Principleof the TandemCylinder
pressurizing
By simultaneously
bothcylinderchambersthe outputforceis almostdoublethal of a standard
cylinderof the samediameter.lt oflersa higherlorce froma givendiameterol cylinder,theretoreit can be
usedwh€reingtallation
spaceis restricted.
DO NOT COPYWNHOUT WRITIEN PERMISSION
PNEU ATIc TEcHNOLOGV
Multl Posltlon Cyllnder
The two end positionsot a standardcylinderprovidetwo fixedpositions.lf morethantwo positionsare
requir€d,a combinalionof two doubleactingcylindersmaybe usod.
Thereare hvoprinciples:
Forthreepositions,the ass€mblyon the lett is required;it enablesusersto tix the cylinder.lt is very
suilabletor verticalmovements,
e.g. in handlingdevices.
The secondis to mounttwo independent
cylinderstogetherbackto back.This allowsfour ditferent
positions,butthe cylindercannotbe tixed.A combination
wilh threecylindersof diflerentstrokelength
gives8 posilions,one withlour 16,but a ratherexolicstructureis requiredand the movement,when
cylindersrun in oppositedirections,is very unstable.
Stroke Lengths
Positions
100 200 300
4
ISO Symbols:
Fig. 6.10Thiee andfourpoiitioncylinder
DO NOT COPYWIIIIOUT WRITTENPERMISSION
-JJ-
4
4
P N E U i t a t t cT E c H N o L o G Y
CYLTNDER
MOUNTING
To ensurethal cylindersare correcllymounted,manutaclurers
oftera selectionot mountingsto meetall
requirementsincludingpivotingmovementusingswiveltype mountings.
BearCl€vis
Flg. 6.11The variousmethodsof CylinderMounting
Floatlng Joints
To accommodate
unavoidable
"misalignment'betweenthe
cylinderrod movementand the
drivenobiect,a lloatingioint must
be fittedto the pistonrod end.
3(
Flg 6.12"Floatingjoinf
The investm€ntin thes€
deviceswill insur€longercylinder
life and morereliableoperation-lar exceedingthe cost of the
deviceitselt.
DO NOT COPYWTTHOUTWRITTENPERMISSION
-54-
P N E U M A T t cT E c H N o L o c Y
f,uckllng Sttength
.h
,M
Whenan excesslhrustis applied
lo a cylinderthe bucklingslrenglh
This
mustbo takenintoconsideralion.
excessthrustcan manifestitselfwhen
lhereis -:
1 -: Compressing
Str€ss.
2f\
2 -: lf lhe stressedpart,i.e.a
cylinder,
is longandslender.
's
The bucklingstrengthdepends
greatlyuponthe mountingmethod.
Thereare four maincases:
'&
1. Rigidlyfixedon onesideand
looseat the oppositeend.
M
2. Pivotingon bothends.
3. Rigidlyfixedon one side,
pivoiingon the other.
Fig.6.13 Thefourmounting
4. Rigidlytix6dat bothends.
lo
The above-mentioned
conditionsapplyif a cylinderliftsor pushesa load;it is lhen sub.iected
compressing
stress.lf a certainspecifiedstrokelengthis exceeded,the cylindercan "br€akout'sidewaysand
seizethus renderingthe cylinderuseless.To avoidunnecessarylossof timeand money,checkwiththe
lengthlable"in the supplier'scatalogue.Th€generalruleof thumbis if the strokeof cylindersabove
mm boreis threetimesthe diameleror, in the caseof smallercylinders,the strokeis tive timesthe bore
the cylinderis pushinga load.
Y L I N D E RS I Z I N G
Y L I N D E RF O R C E
heoretlcel Force
Linearcylindershavethe followingstandarddiametersas r€commended
in ISO:
8, 10,12, 16,20,25,32,40,50,63,80,100,125,140,160,200,250,320 mm
The forcedevelopedby a cylinderis a functionof the pistondiameter,the operatingair pressureand the
resistance.Forthe theoreticalforc€,the thruston a stationarypislon,the frictionis neglect€d.
This,
force,is calculatedusingthe tormulae:
Force(N)
Force(lbt.)
(N/m2),
Pistonarea1m2)' airpressure
or
(lbf./in2)
Pistonarea(in2). airpressure
Thustor a double acting cyllnder:
FE= +
Extending
strcke:
.d- A
Where(D = pislondiameter,p9 = Working(gauge)pressure)
Retractingstroke:Fg =
t
. tB - &l . n
where(d= pistonroddiamerer)
DO NOT COPYWTHOUT WRITTENPERMISSION
P
E U M A T t cT E c H N o L o G Y
lor a singleactlngcyllnder:
FEs= =
4
' d 'p
- Fs (Fs = Springforceat the end of stroke)
It may be quickerlo use a diagramsuchas lhe one in fig. 6.14,showingthe theoreticalforcetor 10,7and 5
bar , or any similarsuppliersinformationto selecta cylindersize.
10
rooozj
z
-;,2.
500
400
300
?50
200
150
r25
100
---,7
p : (bar)
lq-t- - 7.
=:v7-
-4i -2
40
30
.44
m
12.5
10
5.
7
-.-71--Z
1 -
I 2
../
7-,
---------_
15{)00
.z
z.
5000
4m0
-.4
2500
2000
1500
{E
d----
===-rt=='-t
-.2-_L-2.
- - r - /
4
.zx.
:2.
6 (mm)
Fig.6.14 Theor€ticalForceof pneumaticcylinders,trom 2.5 to 30 mm (leftand top scales)
and from32 to 300 mm (rightand bottomscales)for 19,.1-a"ng,5
bg!.workingpressure
Example: Determinethe theoreticalsizeof a cylinderoperatingat a pressureof 6 bar that wouldgeneralea
clampingforceof 1600N.
ttf
Assumingan extendingstroke:-
Transposing:
D=
Fe=
i
G'p
4'1600 N
r'600000N/m2
= 0.0583m = 58.3mm.
A 63 mm. Dia.cylinderwouldbe selected,the largersize providingextratorceto overcomefrictional
resisiance.
By usingthe diagram,we lookfor 1600N on the ForceScaleat the rightside and find 1500as a dashedline.
We followit to the left untilwe reacha poinlbetweenlhe PressureLinesfor 5 and 7 bar and find an
intersectionbotween50 and 63 mm Dia.on the DiameterScaleon the bonom.Thereis no doubtthat
the samediameteris correctfor 1600Nas well as 1500N,
DO NOT COPYWTIFIOUTWRITIEN PERMISSION
P N E U M A T TTcE c H No L o c Y
.lequlred Force
The requiredforcedependson lhe massol lhe load,the angleof movementor elevation,lhe triction,the
workingpressureand the ettectivepislonarea,
The loadconsistsof the Weightof the mass(Fig.6.15a), the ForceB representedby the trictionlacior
(Fig.6.15c). The re-partitionof theselorcesdependg
timesmass(Fig.6.15b) and the requir€dacceleration
plane
(elevation)as shownin tig' 6.15d.
horizontal
with
the
on the angleof the cylinderaxis
F= G. (sina+
F=G
l'-;l
+
@
F=y.G
W6 --tn2. , v2
@
@
Fig 6.15Thecomponentforc€sof the LOAD
A horizontalmovement(elevation= 0") has onlyfrictionto overcome.Frictionis definedby the friction
coetficientU,whichvariesbetweenabout0.1 to 0.4 for slidingmetalparts,and about0.005for iron,rollingon
iron(0.001for ballson the ring in a ballbearing).Thiscoetficiententersthe formulaas a cosine,whichvaries
from 1 tor horizontalto 0 for vertical.
The massrepr€sents
a load,equalto itrsweight,whenth6 movemenlis vertical(90'elevation),The weight
equals,on a lalitudeof
is th€forc6creatodby the earth'sacceleration
on the mass.The earth'sacceleration
450(Standardlor Europeand N. America),9.80629m.s'"or 32.17ft sec?.Witha horizontalmovementthe
The entirecylinderthrustis thenavailablefor
weightis a zero loadas it is fullybornby the construction.
The loadof the massvariesthereforewiththe inclinationtrom 0 to 1000/".lts valueas a factoris
sineof the inclinationangle,0 for horizontal,1 for verlical:
DO NOT COPYWITHOUT WRITTENPERMISSION
P N E U i T A T TT cE c H N o L o c Y
LOAD RATIO
This ratiois generay referredto as "Lo' and equab
. 100%
##
A cylindorshouldnot havea high€rloadratiothan about85%. It an accuralespeedcontrolis requir€dor
loadlorcesvarywidely,60-700/0
shouldnot be exceeded-- perhapsno morethan soyoin vertical
applications.
Table6.16giv€sthe Load Ratiofor cylindersfrom25 to 1OOmm dia.and variouselevationsand two
trictioncoetficients
tor rolling(0.01)and slidingsteelparts(0.2).
Cyl.Dia
Mass(kg)
T
u
60"
po.2
0.01
25
32
40
100
50
25
12.5
180
90
45
22.5
63
80
100
(87.2) (s6.7) 71.5
51.8
.+o.o
48.3
400
200
100
50
650
300
150
75
1000
500
250
't25
'r600
800
400
200
30'
p
p 0.2
0.01
84.9 50.9
342.5 25.4
67.4
tr
(s5.6)
54.9
47.8
53
78.4
39.2
/oa ll
46.6
aa7
55.8
27.9
73.9
37
(ee.2)
54.6
47.6
52.4
72.4
39
(86)
46.3
51.6
27.4
68.3
36.8
(e4.4)
47.2
(e7.6)
48.8
CU
(87) (e6.5) 71.3
43.5 48.3 35.7
82.3 (s1.2)67.4
41.1 45.6 33.7
85 (s4.3) 69.7
42.5 47.1 34.8
(87) (vo.c,
43.5 48.3
71.4
35.7
84.8
42.4
80.1
40.1
82.8
41.4
84.4
42.2
50.8
25.4
4A
24
49.6
24.8
50.8
25.4
o/.J
65.7
32.8
67.3
itJ.o
1.1
0.55
22
11
3.9
2
78
39
20.3
10.9
79.9
40
20
0
1
0.5
1
4.1
1.9
0.9
0.5
3.9
2
1
0.5
4
2
1
0.5
Table 6.16 LoadRatiosfor 5 barworkingpressureand trictioncoefticientsof 0.01and 0.2
DO NOT COPYWTTHOU"T
WRITTENPERMISSION
80
40
20
10
ls.s
J5.O
31 .8
It 0.2
2.2
4
EA
e
0,01
4
2.2
'|
4.4
250
125
oc
.tc
50
45'
p
It 0.2
0.01
81.8
37.8
18.9
9.4
74.1
ov
19.5
9.8
79.9
40
20
10
P N E U A T T cT E c H N o L o c Y
'I
A morepracticalhelptor findingthe correctcylinderdiameterwouldbe to knowlhe allowedloadunder
variousconditions,
Therelore,table6.17showsth€massol the totalloadin kg that resultsin a LoadRatioot
85%,lt is basedon 5 barworkingpr€ssureon the cylind€rand againlhe two frictioncoefticients0,01tor
rolling(l€ttcolumn)and 0.2 for sliding(rightcolumn).Thesevaluesare the maximummassol the totalload.
30"
e
0.01
o.z 0.01 n t
106
42.5
25
3 t . 5 2t23
25
24.5
77
196
40.5
46.2
3920
45
5
4
.
8
58.2
32
39.2
107
272.5
56.4
76.3
64.2
80.9
5450
40
54.5
62.5
100.2 t67.3 126.4 8500
50
97.7
88
Il9
85
1
5
5
t39.8
r
8
9
t59.2 265.5 200.5 13500 675
63
135
428
80
250
225.5
305
256.7
323.5 21775 1 0 8 9
zl7.'l
476.2
390.8
669.2
100
340.2 390.5
352
505.s 34020 l 7 0 l
wilh 5 bar
Table.6.17Massin kg tor cylinderstrom25 to |00 mm Dia.for a LoadRattoot 85olo
workingpressure.
?
CYL. Dia
u:
2t.2
60'
0.01 0.2
0.01
30
0.2
P E E DC O N T R O L
The speedof a cylinderis delinedby the extraforcebehindthe piston,abovethe torceopposedby the
load.The loadratioshouldn€varexceed85o/o
approx.The ,owerlhe loadratiothe benerthe speedcontrol,
especiallywhenthe loadis subiectto variations.A positivespeedcontrolis obtainedby throttlingthe exhaust
ot the cylinderby meansof a €peed Conlrollef,whichis a combinationol a checkvalve,to allowfreeflow
towardsthe cylinder,and an adjuslablethroftle(needlevalve).An exampleol speedcontrolis shownin the
s€clionon valvesin the chapt€ron AuxiliaryValves.To get a conslantspeed,the Load Ratioshouldbe
apprcx.75"/".
Forc€is mass(Wg) timesacceleration.
The unitsarefor torce:kg . m . s'"and for acceleralion:
m . s'. In
EnglishunitsW = lbs and g = 32.17tvsec".
Example:Massof the load 100 kg, workingpressure5 bar,CylinderDia 32 mm, horizontalmovementwitha
friclion coefficientot 0.2. The theoreticalforce is 401.2 N
Table6.16showsthis caseand 90 kg massa load ratiool43.9 "/..
oh.
Thusfor1ooxg:ns.s.$ = 48.8
The Forceof the load is 48.8% of 401.92N = 196 N. Witha cylinderetficiencyof 95%,95 - 48.8%=
46.2o/oof the torceis lettfor the acceleration
of the load.This is 185,7N. The acceleration
is therefore:
.
.
=
185.7kg m s-2/ 1OOkg 1.857m' s-2.Withoutcontrol,the pistonwouldth€oretically
approach2 m/s
afterone second."Theoretically"meansif th€reis no limiiationto the accessof compressedair behind
and no backpressurein fronl of lhe piston.
The limitationof the exhaustairflowcreatesa pn€umatic
load,whichis definedby the pistonspeedandth€
volum€tlowthroughthe restrictionof the speedcontroll€r.
Any incr€aseof the pistonspeedincreasesth6
opposingtoroe.This limitsand stabilizesthe pistonspeed.The higherthe pneumaticpartof the toial load is,
the strongerit can stabilizeth€pistonspeed.
Witha loadratiool 8570and a cylinderefficiencyof 95%, 10 p€rcentof the torceis stabilizingthe
pneumaticload.Whenthe mechanicalloadshowsa variationof * 5olothereis a compensation
of haltthe
influence.Witha load ratioof tor example50%,thesevariationswill no longerhaveany visibleetfecton the
soeeo.
DO NOT COPYWTTHOUTWRITTENPERMISSION
-5v-
P N E U A T T cT E c H N o L o c y
Nole that tor a subtlespeodcontrol,the flowcapacityof the tube has to be muchhigherthan that of the
speedcontrollersetling.With a tubewhichis too smallin diameterthe tubelor a greatpart,limitsthe flowand
changingthe needlepositionhas littleefiect.
AIR FLOWAND CONSUMPTION
Thereare two kindsof air consumptiontor a cylinderor pneumaticsystem.
The.firstis the averageconsumptionper hour,a tigureusedto calculatethe energycost as partof the total
cosl priceol a productand to estimatethe requiredcapacityof compressorand air main.
The secondis lhe peakconsumptionof a cylinderrequiredto ascertainthe conectsizeof its valveand
conneclingtubes,or lor a wholesystem,to properlysizethe F.R.L.unitand supplytubes.
The Air Consumption
ot a cylinderis definedas:
Pistonarea ' Strokelength numberof singlestrokesper minute' absolutepressurein bar,
Explanation; Whenthe pistonis againstthe cylindercov€r(fig.6.18a), the volumeis zero.Whenwe pull the
rod out unlillhe pistonis on the oppositeend,the cylinderis filledwith atmosphericpressureof lOlg25
Pa- (fig.6.18b), Whenthe pressuretromthe supplyenters,the sweptvolumetimesthe gauge
pressurein bar is added,in additionto lhe atmosphericpressureof 10132Spa.
A-
a
dfn
K
F-b--'tl
--+'
l= /.- s -!-E
P.19-z
Y = D 2 ' ! .s.PP'
nres
nm2 {
rft
Frtn
rrnqfte
Fig 6.18TheoreticalAir Consumptionol a cylinder
Withthat,the theoreticalair consumptionof a cylinderis fqrthe ext€ndingstrokeas indicatedin fig.
6.lSandlortheretumstrokeAB.s.(p+patm).WithA=D2.n/4wegetforoutstroking
D (m) . D (m) . rd4.(p + 1.013).Stroke(m) . n (strok€s/ min) . 103(l / min),or
D(mm).D(mm).nt4. (p+ 1.013). Stroke(mm). n (srrokes
/ min). 10€(t/ min).
(Wherep = th6gsugepressureandn = the numberol srhglostokes).
For lhe returnstroke,D is replacedby (D-d).
The consumption ot the tubes bet\ een valveand cylinderequals:
InnerTube Dia.(mm.).InnerTube Dia.(mm). Tube L€ngth(mm). Gaugepressurein Mpa (0.1 bar)
Table6.19 givesthe th€oretical
air consumptionper 1OOmm stroke,for variouscylinderdiamete6and
workingpressures:
DO NOT COPYWTTHOUTWRITTENPERMISSION
-60-
P N E u f iA T t c T E c H t i l o L o cY
Pistondis.
20
7<
32
3
0.124
0.194
0.3r9
Working Pressurein bar
5
6
4
0.217
0.186
0.155
0.243
0.398
o.622
0.291
0.477
0.340
0.557
0.870
0.248
0.388
0.636
0.993
0.746
l.t)J
r.359
1.165
0.97t
50
2.158
2.465
r.850
t.542
63
3.4't9
3.975
2.983
2.487
EO
4.661
5.436
6.2t1
3.III
3.886
100
ot doubleactingcylindersfrom20 to 100 mm dia,
Table6.19TheoreticalAir Consumption
per
in liters
100mm stroke
40
0.498
0.777
|.235
t.93
Example1. Findtheenergycostperhourof a doubleactingcylinderwithan 80 mm.dia.anda 400 mm.
strokewith t2 doublestrokesper minuteand a workingpressureof 6 bar
In table6.19we see that an 80 mm dia.cylinderconsumes3.5 liters(approx.)per 100mm strokeso:
O /100 mm stroke. 400 mm stroke. numberot strokesper min . forwardand retumstroke = 3.5 ' 4
. 24 = 336 Umin.
In the paragraph'Thermaland OverallEtliciency"
in section4, we tindan electricalconsumption
ot 1
kw tor 0.12- 0.15m3/minwitha workingpressureof 7 bar.To produce1 mgn/ minwe require
thereforeapproximately
I Kw of electricpower.
We assumea currencyin whichone kW hr (kilowatl-hour)
costs5 c6nts.
Thecostofproducing
flowof .| r3"hin isthen ffififW
a volume
= 40cents/ hr.
0.336m3ry'min
. 40 cents/ hr = 13.4cents per hour.
In ourexample:
1mg/min
The sum of all the cylinderson a machine,calculatedlhal vvay,repres€nts
the air consumption
as energy
cosl,
It shouldhoweverbe notedthat,
. the consumption
ligur€sin the abovetabledo not includethe 'dead volume"at eitherend ot the
stroke,il any, northal for the connectingtubes.
. the transferof energyis notwithoutlosses(seefurtherbelow).
Forsizing the valve ot an individualcylinderwe needanotherfigure:the peaktlow. lt d€pendson the
highestcylindersp€ed.The highestsum of the peakflowsol all simultaneously
movingcylindersdefinesthe
tlowon whichthe FRL unlt hasto be sized.
We may no longernegl€ctthe thermallosses.In the sectionon the propertyof gaseswe discussed
'adiabatid'change,whichmeansthatthereis no timeto exchangeany heat.Boyle'sLaw,
?.y= constanf is
no longerapplicable,but changesto, ?.lf = constant".The €xponentK (kappa)for air is 1.4.The tableot the
compressionratiotablefrom page7 is reproducedbelowwithan additionalrowfor p.t^ = constantand one
withthe ratiolsothermic/ adiabaticcomoression,
1
2
4
5
6
tl
10
I
Pabs
crisothermic 0.987 1.987 2.974 3.961 4.948 5.935 6.923 7.908 8.895 9.882
cl adiabatic 0.991 1.633 2.178 2.673 3.133 3.576 3.983 4.38 4.749 5.136
factor
I
1 . 2 1 6 1.365 '1.482 1.579 1.66 1.738 1.80 1.873 1.924
DO NOT COPYWITHOUT WRITTENPERMISSION
-61-
PNEU ATIcTEcHNoLoGY
To compensate,or the phenomenarelatedto this change,withoutmakingthingstoo complicated,the
theoreticalvolum€tlow has to be multipliedby a ,actor1.4,whichrepresentsa fair averagecontirmedin a
high numberot practicaltests.This tigureis lessthan in theory,but the changeis generallynot 100%
adiabalic.
Table6.20showsthe liguresof table6. 19,but withthiscorreclionfactor.
Piston dis.
20
25
32
40
50
63
EO
100
3
o.174
o.272
0.446
0.697
t.088
1.729
2.790
4.355
WorkinePr€ssure
in bsr
!
4
6
o.2t7
0.260
0.304
0.340
0.408
0.476
0.557
0.668
0.779
0.870
!.044
1.218
1.360
1.631
r.903
2.t59
2.590
3.021
4.t76
4.870
3.482
5.440
6.525
7.6t1
1
0.347
0.543
0.890
L391
2.174
3.45r
5.565
8.696
Table6.20AirConsumption
of doubleactingcylinders
in litersper100
strokecorrected
tor loss€sbyadiabalic
change
Example2:A cylinderof 63 mm dia.and 500 mm slrokeworksal 6 bar.Whichis the realair consumptionfor
15cyclespermin?
. nr4.500mm. sotrin.
O= 1.4. (63mmr2
ffiff
.16-66634;1s1
= 453.19s
Umin
By usingthe table,we find 3.021yminper 100 mm skoke.This ligurehasto be multipli€dby 150,tor 5
times100mm strokeand30 timesperminute:150/min.3.021liters= 453.15l/min.
DO NOT COPYWTIHOTJTWRITTENPERMISSION
PTIEU ATIC TECHNOLOGY
horanvA C T U A T O R S
R A C K A N D P I N I O NT Y P E
The outputshatthas an integralpiniongeardrivenby a rackanachedto a doublepiston. Standardangles
of rotationare 90" or '180'.
Rack
Pinion
ISOSymbol:
Fig 6.21 Backand PinionRotaryActuator
VANETYPE BOTARYACTUATORS:
Air oressureacls on a
vane, which is attached to the
outputshaft. A titiedrubb€r
, seal or €lastomercoating
sealsthe vaneagainst
leakage.
Elastomer
Damper
A specialthr€e
dimensionalsealsealsthe
stopperagainstthe shaftand
the housing.The size of the
stopperdelineslhe rotalion
angleof 90, 180or 270'.
Adjustablestopsmay be
providedto adjustany angle
ot rolationof the unit.
,rOar*$
180'
900
Fig 6,22VaneTypeRotaryActuator
I Z I N G R O T A R YA C T U A T O R S
orque and Inartia
Linearcylindershavea cushionto reducethe impactwhenlhe pistonhitsthe cover.The capacityof the
f'
cushioningis the kineticenergyit can absorb.This6n€rgy€quaV! ' vZ.lt is mostimportantwhena loadis
propelledwith littletrictionand highspeed.
DO NOT COPYWTTHOUTWRTTTENPERMISSION
-63-
P N E U M A T I Tc E c H N o L o c Y
Thesedynamicsare evenmoreimportantto understandin the caseof a rotaryacluator.A tree stopof a
rotatingmasswithoutcushioningor overloadingrisksbreakingthe pinionor vane,The allowableenergy
publishedby the manutacturer
muslbe caretullyrespected.
J=m.r
a
6 J=m. V-
c
J=m.
rl 2+122
T
I
I
+I ri
d
J' = m .
r 2
4
a
J=m.
v
I
,#,*,
I
' i l Ea -
!-::-!.
-'d-mb= n,t r
y r=m".**'o.F
-
a+b
ll
2 . ^ '2
ta2+c2 +lho'oo#"
i
'
1 J = n a Ti- 1 2
Fig. 6.23 Formulaefor the momentol inertiaof variousbodyshapes
To definethis energywe needto knowthe inertiaof the rotatingmass.Thinkol its materialbeing
composedof extremelysmallparts;the sum of the massof eachindividualpart,multipliedby the squareot its
distancetromth6 rotationaxis givesthe tolal inertia.
The basiccaseis a cylinder,lts inertia€qualsits masstimesthe squareof the radius:
J = m. f.
(kg.m2)
DO NOT COPYWITHOUT WRITIEN PERMISSION
-&-
P N E U M A T I C T E C HN O L O G Y
The inertiaot morecomplicatedformshasto be calculatedwiththe helpof tormulator specificshapes'Fig.
6.23showsthe formulaelor a numberof basicshapes.
hasto be splitup intobasicelementsand the parlialinertiatoialed.For examplea
A rotatingconstruction
chuckon an arm as in fig. 6.23k is addedto the ineriiaof the arm by multiplyingits masswilh the squareol
the distanceof its centerof gravitytromthe rotationaxis.
a shock
Wheneverpossible,rotatingmasseshaveto be stoppedagainsta mechanicalstop,pr€ferably
absorber.lt shouldbe placedas far fromthe axisas possibleas in tig. 6.24a.Any closerto the centerwould
createa reaclion,seefig. 6.24b.lf an €xternalstopon the arm itsellis not possible,it can be donewitha
stopperleveron the oppositeend of the shaft.This is subiectto highreactionforcesand shouldbe doneonly
withthe consenlof the supplier,
StopperLeveron
souareShaftEnd
c
ShockAbsorbers
Stops
Fig. 624 Stoppinga rotatingarm
The inertiator rotatingobiectsis whatlhe movingmassis to a linearmovement.The energyis dofinedby
its speed.For a rotation,the speedis definedby the ?ngular Speedaf. lt is expressedin radiansper second.
Fig.6.25illustratestheseexpressions.
o-- |
rao
' = 7o
1 rad:o= 57.3'
of angularspeed
Fig. 6.25 Definitions
As for the cushioningcapacitytor linearmovements,
tor the maximumallowedenergyto be stoppedby a
rotaryactuatorwe haveto considerthe tinalspeed.An acceleration
by compressedair, if not limitedby a
may be consideredto be almostconstant.The movementstartsat zeroand
stabilizingback-pressure,
reachesaboutdoublethe averagespeed(Strokepertime)at the end of stroke.
DO NOT COPYWITHOUT WRITTENPERMISSION
-09-
P N E U M A T t cT E c H N o L o c Y
Fortastpneumatic
movemenls,
calculations
haveto bebasedontwicetheaveragesp€edasfig.6.26
Low Speed
.- FinalSpeed
Hlgh Speed
- AverageSpeed
Flg. 6.26Averageand tinalspeed
S P E C I A LA C T U A T O R S
L O C K I N GC Y L I N D E R
A cylindercan be fitted
witha lockingheadin placeof
the standardend cover.
It will holdthe pistonrod in
any position.The locking
actionis mechanical,so
ensuringthe pislonrod is
securelyheld,evenin the
caseof pressurebreakdown.
Fig. 6.27TypicalLockingCylinder
R O D L E S SC Y L I N D E R S
With magnetlc coupllng, ungulded
MagneticRingswith
oppositopolarity
lron Discs
Stainl€ssSteel
fig 6.28.TypicalRodlessCylinderwith magn€ticcouplingbetweenpistonand caniage
A conventional
cylinderof say 500 mm.strokemay havean overalloulstrokeddimensionof 11OOmm. A
rodlesscylinderof the samestrokecan be installedin a muchshorterspaceot approximately
600 mm. ll has
particularadvantageswhenvery longstrokesare required.
The magneticretainingforcelimitsthe forceavailabletroma magnetically
couplodtype of rodlesscylinder.
It equalsthat of a normalrodcylinder,up to 7 bar workingpressure,but withdynamicshocksa separationof
the caniagefromthe pislonis possible.Verticalmovementsare therefor€not recommended,
unlessa saletv
marginspecifiedby the supplieris obseN€d.
DO NOT COPYWTTHOUTWRITIEN PERMISSION
-66-
PNEU ATtc TEcHNoLoGY
I
Whenthe couplingbetweenthe carriageand
the loadcannotbe donein the centerlineol the
cylinder,but at a cerlaindistance(X in fig.6.29),
the allowabletorcedecreasesdrastically.The
data,spocifiedby lhe supplierhasto be
respecledto avoiddamageto the cylinder.
Fig 6.29 SideLoadX reducesthe allowable
load
Gulded types, wlth magnetlc coupllng
Dependingon the kindof guideused,lhe problemof sideloadcan be solvedor madeworse.Withball
and alsothe slrokelength.Precisionguideshowever
bearingsfor the guide,a side loadcan be considerable
haveso littletolerancethat the slight€stdetormationincreasestriction.Forthesetypes,the strokelenglhis a
maintactorfor the allowabletorce.Suppliersgivedatator any possiblemounlingorientationand side load.
Fig.6.30showsa
guid€drodlesscylinderwithmagneticcouplingbehveenpistonand carriage'
Fig. 5.30 Rodlesscylinderwithguides,ShockAbsorbersand cylinderswitches
It is r€commended
that the carriageis deceleratedsoftlywithshockabsorberson bothends;in fig. 6.30
theyare builtin. A rail holdsadjustableswitches,operatedby a magnetbuill-into the carriage.
Guided, with mechanlcal coupllng
Carrier
CoveringStrip
SealBelt
Cushioning
Tube
Piston
Cushioning
Seal
Fig.5.31RodlessCylinderwith mechanicalcoupling
For littingor movingheavierloads,a "slottedcylinder"typeexcludesthe riskot disconnection
of the carrier
fromthe pistonunderdynamicshocks,but it is nottotallyleakfree unlikethe magnetically
coupledtype.
DO NOT COPYWTTHOUTWRITTENPERMISSION
P r { E UA T r cT E c H N o L o c Y
SLIDE UNlTS
The slideunitis a precisionlinearactuatorof compactdimensions,whichcan be usedon robotic
manutacluring
and assemblymachines.
, f f i " 8
Fig. 6.32TypicalSlideUnit
Preciselymachinedwork mountingsurfacesand parallelpistonguiderodsensureaccuratestraight-line
movementwhenbuiltin as part of the construction
of a transterand positionmachine.
In one position,the bodycan be tixedand the rodswith end barscan move(b). Upsidedown,the end bars
touchthe mountingsurfaceand lhe bodycan move(c). In bothcases,the valvecan be connectedto the fixed
part,eitherby the portsA and B, or Al and Bl in fig. 6.32a.
HOLLOW ROD CYLINDER
This actuatoris speciticallydesignedfor .pickand place.applications.
The hollowrod
providesa direclconnectionbetw€ena
vacuumsourceand a
vacuumpad,attached
to the rodsworking
end.The connecting
tube at the rearof the
cylinderremainsstatic,
whilethe rod extends
and retracts,
Vacuum
Connection
(stationary)
Fig. 6.33 HollowRodGylinderwith a non movingvacuumconnection
DO NOT COPYWTTHOUTWRITIEN PERMISSION
-68-
P N E U U A T t cT E c H N o L o G Y
|'rne
l n R o r A T r N cc Y L T N D E R
A so-calledrotatingcylinderis an assemblyot a linearcylinderwitha rotaryactuator.A rotatingarm can be
attachedto the shattand be equippedwitha gripperor vacuumpad to pickup wolk piecesand deposilthem
handling.
"pickand place"uni or materials
in anotherlocationafterrotatingthe arm.Thisgivesa
Fig. 6.34TypicalRotatingCylinder
\ I R C H U C K( G R I P P E B )
An actuatordesignedto
gripcomponentsin robotic
typeapplications.
Opened
MainPiston
I The typeshownhas
two opposingpistons,to
openand clos€the iaws.
SecondaryPiston
SpeedControlScrew
Fig.6.35TypicalPneumaticFulcrumTypeGripper
Fig.6.36showsthreetypicalapplications
of the lasttwo elements:
Flg. 6,36Typical
Applications
of the
RotatingCylinder
andAir Gripper
DO NOT COPYWITHOUT WRTTTENPERMISSION
-69-
P N E U M A T t cT E c H N o L o c Y
7 D I R E C T I O N A LC O N T R O LV A L V E S
V A L V EF U N C T I O N S
A directionalcontrolvalvedeterminesthe tlowot air betwe€nits portsby opening,closingor changingils
The valvesare describedin termsot: lhe numberof ports,the numberof switching
internalconnections.
positions,its normal( not operated) positionand the methodot operation.The firsttwo pointsare normally
expressedin the t€rms5/2, 312,2!2elc.The tirstfigurerelateslo th€numberol ports(excludingpilotports)
and the secondto the numberol gosilions.
The mainIunctionsand
are:
Principal Construclion
Symbol
Function
Application
2y2oN/oFF
Air motors and
withoulexhaust. pneumatictools
3/2 Normally
closed (NC),
pressurizing
or
exhaustingthe
outDutA
3/2Normally
open(NOl
prcssurizing
or
exhausting
the
outDutA
Singleacting
cylinders(push
type),pneumaric
signals
Singleacting
cylinders(pull
type),inverse
pneumaticsignals
4/2 Switching
betweenoutput Doubleacting
A andB, with
cylinders
comrnonexhaust
4
2
5 1 3
5/2: Switching
betweenoutput Doubleacting
A andB, with
cylinders
sePaBte...
exhausts.
5/3,Opencenter: Double acting
As 5/2 but with cylinders,with the
possibilityto deoulputs
pressurizethe
exhaustedin
mid-oosition
cvlinder
5/3 Closed
Double acting
centenAs 512
cylinden,with
but with rnidstopping
positionfully
possibility
shutoff
5/3 Pressurized Specialapplicenter:
cations,i.e.
Locking Cylinder
Table 7.1 ValveSymbols,Principles,descriptionand mainapplications
DO NOT COPYWTI}IOUT WRITTENPERMISSION
-70-
P N E U M A T IT
c E c HN o L o G Y
PORTlDENTIFICATION
The denominations
of the variousporlsare not uniform;thereis moretraditionthan respecledslandard.
Originally,the codespreviouslyusedlhe olderhydraulicequipmenthavebeenadapted.'P" for the supply
portcomesfrom"pump",lh€ hydraulicsourceot fluid€nergy
The outletof a 2/2 or 3/2 valvehas alwaysb€en"A",the s6cond,antivalentoutputporl "8".
The exhausthas initiallybeen"R" from Return(to the oil tank).The secondexhaustport in 5,/2valveswas
th€nnamedS, or the former"R1"and the latt€r"R2".
The pilolport initiatingthe powerconnectionto portA hasoriginallybeencoded"Z (thetwo elitreme
bners in lhe alphabetbelongstogether)and the other.y'.
Afler20 yearsbargainingaboulpneumaticand hydraulicsymbols,one ot the ISO workgroupshadthe
idealhat porlsshouldhavenumbersinsteadof letters,delayingthe terminationof the standardISO 1219by
anolher6 years.Supplyshouldbe "1",the outputs2'and "4', the pilotportconnecting"l"with 2" is then"12"
etc.Table7.2 showsthe tour mainsetsof port identifications
in use.Preterredare now the numbers.
Supply NCoutput NOoutput
A
P
P
P
A
A
2
1
B
B
B
Exhaustof
NC
R
R1
EA
4
3
exhaustof
NO
s
R2
EB
5
Table 7.2 Typicalportidentitications
Pilottor NC Pilotfor NO
z
z
PA
12
Y
Y
PB
14
M O N O S T A B L EA N D B I S T A B L E
Springreturnedvalvesare monostable.
They havea definedprefenedpositionto whichthey automatically
retum.
A bistablevalvehas no preferredpositionand remainsin eitherpositionuntilone of its two impulsesignals
are operated.
VALVE TYPES
The two principalm€thodsof construction.are
Poppetand Slidewitheitherelastic.ormetalseals,Fig.7.3
relatesto the variouscombinations.
Directional
Control
Valves
MetalSeal
Flg. 7,3 The varioustypesof valvesand sealingmethods
DO NOT COPYWTTHOUTWRITTENPERMISSION
P N E U M A T T CT E C H N O I O G Y
P O P P E TV A L V E S
Flowthrougha poppetvalveis controlledby a discor pluglittingat rightanglesto a seat,withan elastic
seal.
Poppetvalvescan be two or threeporl valves,f or a lour or five portvalvetwo or morepoppelvalveshave
Fig. 7.4 The maintypesot poppets
In a) the inlelpressuretendsto liftthe sealott its seat requiringa sutficientforce(spring)to keepthe valve
closed.In b) the inletpressuroassistslhe returnspringholdingthe valveclosed,butthe operatinglorcevaries
thereforewithditfer€ntpressures.Thesetactorslimitthesedesignsto valveswith l/8" portsor smaller.
A
a
ISO Svmbol
Fig.7.5.Mechanically
operatedpopp€tvalv€
P
F
Fig7.5 a) showsa NC 3/2 poppelvalveas shownin fig.7.4 b.
position(a),theoutletexhauslsthroughthe plunger.Whenoperated(b) the exhaust
ln its non-operaled
porl closesand the airflow'sfromthe supplyport P to the outletA.
Design7.2 c) is a balancedpoppetvalve.The inletpressureacts on equalopposingpistonareas.
NC NO
ISOSymbol
Fig 7.6 Balancad3/2 PoppetValve
Thisfeatureallowsvalvesto be connectedup normallyclosed(NC)or normallyopen (NO).
Normallyopenvalvescan be usedto loweror retumsingleactingcylind€rsand are morecommonlyused
in satetyor sequencecircuits.
DO NOT COPYWITHOUT WRITTENPERMISSION
-72-
P
E U M A T T Tc E c H N o ! o c Y
S L I D I N GV A L V E S
Spool,rotaryand planeslidevalvesusea slidingactionto op€nand closeports.
Spool Valves
A cylindricalspoolslideslongitudinally
in the valvebodywilh the air tlowingat rightanglesto the spool
movemenl.Spoolshaveequalsealingareasand are pressurebalanced.
Elastomet seal
Commonspooland seal anangem€nlsare shownin tig. 7.7 and7,8.In fig 7.7 O-ringsare tittedin grooves
on the spooland movein a metalsleeve.Two of themare crossingoutputports,whichare lhereforedividedin
a greatnumberol smallhol6sin the sleeve.
Flg.7,7SpoolValvewithO-Ringsonthespool,crossing
thecylinderports
Thevalvein fig.7.8hassealsfittedin thevalvebody,whichar6keptin position
by meansof sectional
spacers
Flg. 7.8 SpoolValvewith sealsin the housing
Fig 7.9 sho|s a spoolwith oval rings.Nongof th6m haveto crossa porti butlust to open or closeits own
seat.Thisd€signprovidesa leakagefree sealwith minimumfrictionandthereforean €xtremelylong life.
Flg. 7.9 Valvewithoval ringspool
DO NOT COPYWTTHOUTWRITTEN PERMISSION
P N E U M A T t Tc E c H N o L o G Y
Itetal Seal
Lappedand matchedmetalspooland sleev€valv€shavevery low trictionalresistance,rapidcyclingand
longworkinglife. But 6venwitha minimalclearanceol 0.003mm,a smallinternalleakagerate
exceptionally
as longas the cylinderhasnot to be heldin a positionby
of aboutone l/minoccurs.Thishas no consequence
a 5/3 valvewithclosedcenlertor sometime.
EBPEA
EBPEA
Flg. 7.10 Principleof the seallessSpooland SleeveValve
,lane Slide Valve
Flowthroughthe portsis controlledby the positionof a slidemadeol metal,nylonor otherplastic.The
slideis movedby an elastomersealed,air operat€dspool.
Flg. 7.11 5/2 PlaneSlideValve
DO NOT COPYWITHOUT WRITIEN PERMISSION
-74-
P N E U t r t A T t cT E c H
oLocY
notary Valves
A m€lalporleddiscis manually
rotatedto interconnect
imbalance
is
theportsin thevalvebody.Pressure
employed
lo forcethediscagainstits matingsurfaceto minimize
leakage.
Thepressure
supplyis abovethe
disc.
tffi
P
F
ISO Symbol
A B
rT--r]
PEX
A E T
t--l
IT TI
PEX
t-vt
A B
PEX
ffi
PEX
Fig 7.12 Sectionthrougha RotaryDiscValveand a discfor a 4/3 tunctionwith closedcenter
DO NOT COPYWTTHOUTWRITTEN PERMISSION
-75-
P N E U U A T t cT E c H N o L o c Y
I
U A L V EO P E R A T I O N
MECHANICAO
L PERATION
A
On an automatedmachine,
mechanically
operaledvalvescan
detectmovingmachineparlsto
providesignalstor the automatic
conlrolof lhe workingcycle.
n
n
tldt
t-l
A
!ol/
-e+
=r
:E
l:Ez
:
:
Plunger StraighlBoller Square Roller
The maindirectmechanical
operators
areshownin 1i9.7.13
e
RollerLever
Operators
Fig 7.13The mainM€chanical
Cate when using Roller Levers
Specialcaremustbe takenwhenusingcamsto operaterollerlevervalves.Fig.7.14 illustratesthis:the
utilizedportionof the rollerstotaltravelshouldnot go to the end ot stroke.The slopeot a cam shouldhavean
angleof about30"; steeperslopeswill producemechanicalstresseson the lev€r.
PT: Pre-travel
OT.: Over Travel
TT.:Total
W FollerStroke
to
beutilized
Fig. 7.14Carewith RollerLeversand Cams
Th€one way roller (or idle r€turnroller)will only operatewhenthe controlcam strikesthe actuatorwhen
movingin one direction.In the reversedireclionthe rollercollapseswithoutoperatingthe valve.
U I A N U A LO P E B A T I O N
Manualoperationis generally
obtainedby attachingan operator
head,suitabletor manualcontrol,
ontoa mechanically
operated
valve.
lry
Flush
'
l-r-\
E]
Baised
TfI
,ffi'
Mushroom
Flg. 7.15The mainmonostableManualOperators
Manuallyoperated,monostable(springretumed)valvesare generallyusedtor starting,sloppingand
otherwisecontrollinga pneumaticcontrolunit.
For manyapplicalionsit is
moreconv€nient
if the valve
ftsposi on. Fig.7.t6
marntains
showsthe moreimoortanltvoes
ol bistablemanualoperators
Im
l--r
E
\
m
t-,
-1
\ \
1+r
:
:
RotatingKnob
Toggle
Key
Flg. 7.16BistableManualOperators
DO NOT COPYWTTHOUTWRITTENPERMISSION
-76-
P NE U I I I A T I Tc E c H N o L o G Y
AIR OPERATION.
Directionalcontrolvalves,usedas "PowerValves",shouldbe locatedas closeas possibleto ils aclualor
and be swiichedby remolecontrolwith a pneumaticsignal.
A monostsbleair operatedvalveis switchedby air pressureactingdirectlyon one side ot the spoolor on
a pislonand returnedto ils normalpositionby springtorce.The springis normallya mechanicalspring,but is
can also be an "air spring"by applyingsupplypressureto the spoolend,oppositeto the pilol port,or a
combinationof both.In the lattercase,the pilotside requir€sa biggeretfectivearea,whichis providedby a
piston.
Air connection
for
spnngassistanc€
Pistonwith twice the ar€a
of th€ spoolal sping side
Fig.7.17 A2 Ait operatedValve,with ah assistedspringretum
Air assistedspringretumgivesmoreconstantswitchingcharacteristics,
and higherreliability.
In fig 7.18an ak springis providedthroughan internalpassagefrom the supplyportto act on the smaller
diameterpislon.Pressureappliedthroughthe pilol portontothe largerdiameterpistonactuatesthe valve.
This methodof returninglhe spoolis oftenusedin miniaturevalvesas it requiresvery littlespace
r
A
ISOSymbol
I
I
ir t4
I
!
ri
I
Flg 7.18Ah operated3/2 Valvewith air springreturn
The air-operated
valvesdiscussedso far havebeensinglepilotor monostabletyp€s,but the more
commonair operatedvalvefor cylindercontrolhasa doublepilotand is designedto restin eitherposition
(bisiable).
PA
EAPEB
NFPA labels
EB
Fig. 7.19 Bistable,air operat€d5,/2Valve
DO NOT COPYWITHOUT WRTTTENPERMISSION
-77 -
P N E u l t A T t cT E c H N o L o G Y
pulsehaslastbeenappliedto the pilotport"P8",shiftinglhe spoolto ihe dghl
In tig,7.19,a shortpressure
I andconnecting
through'EA".Thevalvewill
thesupplyport"P'lo thecylinderport'8". Port"A' is exhausted
'memoryfunction''
remainin this operatedpositionuntila countersignalis received.This is referredto as a
Bistablevalvesholdlheir operatedpositionsbecauseol lriction,but shouldbe installedwiththe spool
the positions
horizontal,especiallyif the valveis subiectedto vibration.In the caseot metalsealconstruction,
are lockedby a delenl.
Plloted Operation.
A directoperationoccurswhena force,appliedto a pushbutton,rolleror plunger,movesthe spoolor
poppetdirectly.Withindirect,or "piloted"operation,the externaloperaloracts on a smallpilotvalvewhichin
tum switchesthe mainvalvepneumalically.
JIS lab€ls:
Fig 7.20 IndireclMechanicalOperation
Fig.7.20a showsa 5/2 Valvewilh indhector ?iloted" n€chanicaloperationin its normalposition.Th€
magnitieddetailsin b and c showthe pilotpartin normal(b) and in operatedposition(c).
DO NOT COPYWITHOUT WRITTENPERMISSION
-78 -
P
EU ATIc TEcHNoLocY
S O L E N O I DO P E R A T I O N
Electropneumatically
and electronically
controlledsyslemsare discuss€din a laterbookin this seriesand
it is sufficienlat this stageonly to considerthe electricaloperationof directionalcontrolvalves.
In smallsizesolenoidvalves,an ironarmaluremovesinsidean airtighttube.The armatureis finedwith an
elastomerpoppeland is liftedtroma supplyseat in the bodyby the magnetictorce ol the energizedcoil. Fig
7.21a.
P
R
ISO Symbol
--=
D t:-_
FlgT,21 a:2J2,b: 3/2 directsolenoid,springretum,poppettypevalve.
b)
A 3/2 valvehas also an exhaustseaton top and the armaturean elastomerpoppetin its top end (Fi9.7.21
Directlyoperated5/2 solenoidvalvesrelyon the electromagnetic
forceof the solenoidto movethe spool
(1i97.221.
lt can only be a seallesslappedspooland sleevetype withoutfriction.
Flg. ?.22 Directsolenoidoperated512Valvewithspringretum
To limitthe sizeof th6 solenoid,largerand elastomersealedvalveshaveindirect(piloted)solenoid
oo€ration.
R2
JIS Symbol
Fi$.7.23 5/2 monostableSolenoidValv€withelastomercoatedspool
DO NOT COPYWITHOUT WRITTEN PERMISSION
-79 -
P N E U M A T I CT E C H I I O L O G Y
it will retum,by meansof springs,whenbolh solenoids
, The 5/3 valvehas a third(center)positionto which
rarede-energized.(lig
7.241
JIS Symbol
Fig Z.24.Pilotoperated 5/3 Solenoid Valve with closed center and spring centeringvalve mounting
I R E C TP I P I N G
The mostcommonmethodof connectionto a valveis to screwfittingsdirectlyintothe threadedportsof a
so-calledbodyportedvalve.This methodrequiresone fittingfor eachcylinder,piloland supplyportand one
types,exceptfig. 7,22' whicn
silencertor eachexhaustporl,All the valvesshownpreviouslyare body-ported
is sub basemounted,.
ANIFOLDS
Manifoldshavecommonsupplyand exhaust
channElsior a givennumberof bodyported
separatelyto
valves.The outputrs
are conn€cted
eachvalve,
Cylinder Ports
AandB
Fig.7.25showsa manitoldwithtourvalvesof
difterenltunctions:a 5,/3.a bistableand two monostabletypesof the sameseries.
A manifoldshouldbe orderedlo accommodate
the requirodnumberof valves,ext€nsionis not
possible,but usinga blankingkit can sealspare
positions.
that
With5 or morevalvesit is recommended
air is suppliedand silencersmountedat bothends,
Common
Supply
Common
for
Exhausts
A andB Ports
'
Fig.7.25TypicalManifold
DO NOT COPYWTTHOUTWRITTENPERMISSION
-80-
P N E u t , A ' I cT E c H N o L o G Y
SUB BASES
Valveswithall of theirportson one lace are designedto be gasketmounledon a sub base,to whichall lhe
externalconnectionsare made.Thisallowsquickremovaland replacemenlof a valvewilhoutdisturbingthe
lubing.Generally,a basemountedvalvehas a slightlybetterflow capacitythan a body-portedvalveof the
sametype.Fig.7,22showsa typicalbasemountedvalve.
M U L T I P L ES U B B A S E S
In a similarway to lhe manifold,
multiplesub basessupplyand
exhausta numberol valvesthrough
commonchannels.Alsothe cylinder
portsare providedin the sub base.
Multiplesub basesalso haveto
be orderedlor the reouirednumber
of valvesand are ableto be blanked
otf in the sameway as manifolds.
Fig.7.26showsa manitoldwith
lour basemounttypes3ii2Solenoid
Valves,The commonexhaustports
are to be equippedwilh Silencers,
prelerablyon bothendsto avoid
back-pressure.
This is not only
recommended
tor soundelimination
but also tor dust protection,
ValveOulputs
. (A Porrs)
Fig. 7.26 MultipleSub Basewithtour 3/2 Valves
G A N G E DS U B B A S E S
GangedSub Basesare assemblies
ol individualbas€s,whichallowany
reasonablenumberto be assemblsd
intoone unit.This systemhasth€
advantageof allowingextensionor
reductionof the unit if the systemis
altered,withoutdisturbingthe existing
comoonents.
Thereis stillthe oDtionto
blankotf positions,il required.
Fig.7.27showsa typicala$sembly,
equipp€dwilh one monostableand two
bistablesolenoidvalvesand a blanking
plate.The individualsub basesare
holdtogetherwithclamps.Other
constructions
mayalso haveboltsor tie
rodsfor the purpose.O Rings,inserted
in groovesaroundthe channels,
providea leakagetreeconnectionof
supplyand exhaustchannelsfrom end
to end.
Fig. 7.27 GangedSub Basewiththreevalvesand one
blankedoosition.
DO NOT COPYWITHOUT WRITTEN PERMISSION
PNEU ATtc TEcHNoLoGY
V
A L V ES I Z I N G
t
I N D I C A T I O N SF O F F L O W C A P A C ] T Y
Portdimensionsdo not indicatethe flowcapacityof the valve.The selectionot the valvesizewill depend
on the requiredtlowrale and permissiblepressuredropacrosslhe valve'
provideintormationon lhe flowcapacityof valves.Flowcapacilyis usuallyindicatedas
The manutacturers
the so called"standardtlow" On in litersof lree air per minuteal an inletpressureot 6 bar and an outlet
pressureof 5 bar,or witha flowfactor,Cv or kv, or wilhthg equivalentFlowSection"S".Thesefactorsrequire
lormulaeor diagramsto definethe tlowundervariouspressureconditions.
The Cv faclor of 1 is a llow capacityof one US Gallonol waterper minute,witha pressuredropof 1 psi.
The kv factor of 1 is a llow capacityof one literol walerper minutewitha pressuredropol 1 bar.
The equivalentFlow Section "S" of a valveis the flow sectionin mm2ol an orilicein a diaphragm,
b€tweenpressureand flow.
creatingthe sam€relationship
All threemethodsrequirea formulalo calculatethe airtlowundergivenpressureconditions.Theyare as
tollows:
C=400'Cv'
r_.013)
Q=21.94'kv
LtJ
t-=---:-=-;;-|
Q = 2 2 . 2 ' s' .vt (sD- z + r u J . s , | . A' p. '. 1 l\; t; -n-! + e
WhereCv, kv =Coefficients
ol flowand S =EquivalentFlowSectionin mm2
Q = Flowratestandardliters/min
p2 = Outletpressureneededlo moveload(bar)
pressuredrop(bar)
Ap or EAp = Permissible
0 = Air temperaturein *C
Withthis,the dimensionof 'a" O *
To lind the llow capacily,theseformulaeare transtormedas follows:
v
Cv=
4 0 0 . J F 2 + 1 . 0 1 3 ). A p
k v =
2 7 . 9 4 . 4 @ 2 + l - 0 1 3 ). A p
S
222. l@2 + r-013). Ap
=
DO NOT COPYWTTHOUTWRITTENPERMISSION
-82-
P
E U M A T I cT E c H i I o L o G Y
1 C v = l kv=
The normalflow Ontor othervarioustlow capacityunitsis:
The Relationshio
betweentheseunitsis as tollows:
rs =
981.5 68.85 54.44
1
14.3
18
1.26
o.o7 1
0.055 o.794 1
Note:The outcomeof this calculationgivesin fact not the flow capacityof the valve,as we simplystated
above,but tor the assemblyof lhe valveand the connectingtubesand tilling.To get as muchtlow
capacity,thal of the valvehas to be higher.Howmuchhigher?
Orlllces In series connectlon
Beforewe can determinelhe sizesot valveand tubing,we haveto lookat how pressuredropsovera
numberot subsequentorificesin series.The formulafor the resulting"S" is:
s total=
l
t
1
s12*sl*"'sn,
To avoidunnecessarily
dealingwithsuchtormulaewe looktor a thumbrule.Fig.7.28.1and Fig.7.28.2
showthe relationship
betweena numberof orificesin.seriesconnoctionand the resultingflow.
C"=l
C'=l
C;l
C,=l
C;l
C;l
C"=t
Flg.7.28.1In Seriescircuit,all deviceshavinga C" of 1 and the resultingimpacton the circuit,sovsrallC,
\i_
--+
C,-=t
_><_><_#
=.x><+<_=
-..>---.>
c,=1.4
C,=1.4
C,=1.73 c"=1.73 C"=1.73
G".v"=1'0
C,*=1.0
c,=1
C-"=r
C"=2
C,=3
C*"=0.9g
C"*=o.06
C,=2
C"=2
Q,=2
C"-=1.0
c,=4
C,"r.=0.84 C",l/|=0.89
C*=0.82
Flg. 7.28.2Orificesin seriesconnectionand resultingllow
Retumingto our topic,we can say that it is mostobviousto haveaboutth€sameflow capacityfor th€
valve and the connectingtube withits fittings.We considerthesepartsas two equalflow capacitiesin series
connectionand lo havethe calculatedtlowthroughbothparts,the requiredsectionhasto b€multipliedwith
1.4(\E ).
NOTEthat eventhoughthe C, is larg€rit reduces(whenaddedin series)the systemC, -- a chainis only
as strongas its weakestlink.The smallestoriticedeterminesthe llow for the circuit.
DO NOT COPYWTII{OUT WRITTEN PERMISSION
-83-
P
E U T , A T I CT E C H N O L O G Y
llow clplcrrY oF TuBEs
Stillunknownis the tlowcapacityof tubesand tittings.The formula,or the equivalentsectionot a tubeis:
r=
Lrr
S = s . .fr- where c is the tube co€tlicient(s€e below),d the Pipe lD and L th€ tube length in mm.
I L
in
a = 2.669' Q . d0.155 wh€req is thetubecoetlicient
fr
ct is 1.6tor gas pipeand 2.0 tor Plastic,Rubberand CopperTubes.The two formulaecan be unitedto
a2.655
S = q , 2.669.:--lf
vL
that wilh very shorttubesit is no longervaluable.For
This tormulahas,however,lhe inconvenience
as the effective
example:a tube8x6 mm with0.1 m lengthwouldhavean S ot 65 mmz.This is impossible,
areaof the innertube diam€t€ris only28.26mm2.Thereforethe aboveformulafor Stotalhasto be appliedfor
correction.
Youcan by-passall thesecalculalionsby readingthe equivalentSectionof nylontubes,normallyusedfor
pneumatics,
fromthe diagram7,29.
'i:
L
I
I
!
;
\
\
*
20
10
0
0.02
0.05
0.1
o.2
0.5
5
1
0
ube Lengthin m
Fig. 7,29tho equivalentFlowSectionS in mm2of the cunenttubesizesand length
DO NOT COPYWITHOUT WRITTENPERMISSION
-84-
P N E U T T A T TT Ec c H N o L o c Y
The FlowSectionol littingshas to be specifiedin the catalogues.The totalof a tub€lengthwith ils two
tittingscan be calculatedwilh the tormulaabove.To reducethe needot its use to exceptions,you can tind the
s€ctionsfor the mostcurrenttubeassembli€sin table7.30.
Tube Material
Dia,
(mm)
4x2.5
N,U
l m
Lenqth
0.5 m
1.86
3.87
6x4
N,U
6.12
7.78
8x5
U
10.65
13.41
8x6
N
t6.&
20.28
l0 x 6.5
U
20.19
24.50
l0 x 7.5
N
28.U
12x8
U
12x9
N
Fittinss
Inserrype
O n e ' lo uch
elbow
straisbt elbow
sraight
1.6
1.6
4.2
5.6
6
6
l3.l
t.4
(9.5)l l
ll
l8
t4.9
(t2) l 6
l7
2t.6
26.1
35
(24r30
33.38
30
(23)26
33.18
39.16
J)
(24)30
43.79
5r.00
45
(27135
29.5
25
41.5
35.2
46.1
39.7
50.2
Table 7.30 EquivalentFlowSectionof currenltubeconnections
58.3
Total
0.5 m tube+
2 stn. fittinss
1.48
3.r8
3.72
5.96
6.73
9.23
10.00
r3.65
r2.70
15.88
19.97
22.t7
20.92
25.05
?9.45
32.06
Table7.30showsth€flow capacityol currenttubesand fittings,basedon so called"push-in"or'On6
Touch"littings$tg.4.22),havingthe sameinnerdiamet€ras the tube.Insertfittings(fig.4.21)reducethe flow
considerablyr
especiallyin smallersizes,and shouldbe avoidedfor pneumatics.
Valves wlth Cylinders
We now retumto the cylinderconsumption.
This is firstof all th€p6akflow,dependingon speed.
Secondwe haveto definethe allowablepressuredrop,a maiorligurein calculatingthe valvesize.An
assumptionol aveEge velocitymay be made,sincemaximumtlow is achievedat a pressuredropof
-- lor our purposes23"/.is the maximumallowablepressuredrop (halfof 46%)-- the
approximately
46010
NFPAstatesa 157omaximumpressuredrop is d6sir6d.
The actualsizeol the valvehasto be muchhigherlhan the theoreticalvalue,to compensatefor the
additionalpressuredropin the connectingtubesand fittings,as discussedabove. But if th€maximumflow is
determined(limited)by the finingsand tubingpart of the circuit-- changingthe valvefor a largerflow
capabilitywill not havean etfect. E.g.il lhe valvehasa C" of 2 and th€tubingand fittingscollectivelyhavea
C, of 1 -- the systemwill not be improvedby a valvewitha C" 4); noie Fig.7 28.2.
To makethingseasy,all the calculationsmentionedbeforcon lhis subject,table7.31,givesyou the
requiredequivalentsectionS tor the valv€and tor the selectionot a suitabletubeand fittingsassemblylrom
table7.30.Th6 tableis basedon a supplypressure6 bar (approx.90 psig)and a pressuredropof 1 bar (15
psig)beforethe cylind€r.lt includesalsoth6 lossby adiabaticpressurechangeand th€temperalure
coetficientfor 20'G. Usuallythis will sufficefor mostrealworldapplications.
DO NOT COPYWTTHOUTWRITIEN PERMISSION
-85-
P N E U T / | A T I CT E C H N O L O G Y
dla.mm
8,10
12,16
20
25
32
40
50
63
80
100
125
140
160
50
0.1
0.12
o.2
0.35
0.55
0.85
1.4
2.'l
3.4
5.4
a.4
10.6
13.8
100
0.1
0.23
0.4
0.67
1.r
't.7
2.7
4.2
6.8
10.8
16.8
21.'l
27.6
Averageplston speed ln mm/s
150 200 250 300 400 500
0.15 0.2 0.25 0.3 0.4 0.5
1
0.36 0.46 0.6 0.72
1.2 1.6
1
0.8
0.6
3.4
2.7
2
I
1.3
c.c
3.7 4.4
2.2 2.4
8.5
6.8
5
2.6 3.4 4.3
8.1 10.8 13.5
4
5.4 6.8
A E
8.4 10.5 12.6 16.8 21
10.2 13.6 1 7 20.4 27.2
16.2 21.6 27
750
0.75
1.8
3
5
8.5
12.8
20.3
1000
1
2.4
4
6.7
11
17
27
za.z
EqulvalentFlow Sectlon in mmZ
Table 7.31EguiyalentSectionS in mm2for the valveand the tubing,lor 6 barworkingpressureand a
pressuredropol 1 bar (OnConditions)
Allhoughthe assumedpressureof 6 bar and a dropof 1 bar are a quitenormalcase (the Q^is basedon
ther€mightbe otherpressureconditions.Thenthe figuresfrom table7.31 r€quirea
the sameassumption),
conection.The diagram7.32giv€sthe percentageol the tiguresin table7.31for any practicallypossibleinput
pressuresand pressuredrop.
ct
1.8
1.6
1.4
P12
3
1.2
1
0.8
7
I
o
'10
0.6
0.4
1.25 1.5
?p in bar
Fig. 7.32CorrectionFactor"cf'for the Sectionsgivenin Table7.31,for otherpressureconditions
DO NOT COPYVVITHOUTWRITTENPERMISSION
-86-
PNEU ATtcTEcHNoLocY
The figuresbelowthe boldlineare values,whichar6 in g€neralnot coveredwith 5/2 valves.Wherethese
sizesare not available,two High Flow3/2 vatveswill do the iob.
Example1
An 80 mm Dia cylinderwitha strokelengthof 400 mm has an averageworkingpressureol 6 bar.The
maximumallowablepressuredrop is 1 bar. lf a cylinderspeedot 500 mm/secis required,what is the
minimumCv of the valve?
We find in Diagram7.31 an equivalentsectionof 34 mmz.To obtainthe Cv factorwe haveto dividethis
numberby 18:34 /18 = 1,89.
A Tub€sizeof 12 x 9 mm.with"OneTouchFittings'is requiredto get this speed.
Example2
A 50 mm Diacylinderhas to run witha speedof 400 mm/s,with an availablesupplypressureol 7 bar
and an allowablepressuredropof 2.5 bar.That meansthatthe cylindersize is basedon an eflective
pistonpressureof 4,5 bar.
Table7.31givesan S of 10.8mm2.This figureneedscorrectionfor a supplypressureof 7 bar and a ?
ot 2.5 bar.We followthe line? bar fromthe rightto the l€ftuntilit interects the verticalline of 2.5 bar p. We
find a "cf of 0.66.The requiredS ot the valveand the.tubeconnectionis therefore10.8. 0.66= 7.128mm2.
Selecta valveof this size or bigger.A tube of 8x5 or 8x6 mm Dia is suitable.
DO NOT COPYWTI}IOUT WRITTENPERMISSION
-87 -
PNEU
ATtc TEcHNoLoGY
I
A U X I L I A R YV A L V E S
N O N . B E T U F NV A L V E S
A non-returnvalveallowstreeaidlowin one directionand sealsil otf in lhe opposite.Thesevalvesare
also referredto as checkvalves.Non-retumvalvesare incorporaledin speedcontrollersand self-sealtittings
etc.
ISOSymbol
Flg 7.33 Gheckvalve
b
p e e oc o N T R o L L E B s
I
I
A "speedcontrolle/'consistsof a checkvalv€and a variablethrottlein one housing.lt is also correctly
will cali devic€sspeedcontrols
calleda Flow Control (baseduponits symbol).Manytimesmanufacturers
and,in fact,theyare reallyneedlevalves,veriiywiththe symboltobe certain.
Keepin mindthat flow controlscan onlyslowdowna cylinder;they posea restrictonin bolhdirectionsof
air flowand thereloreslowthe responseof the cylinderon boththe extendas well as the retraclstroke.In
mostcasesflowcontrolsshouldbe usedto meterthe exhaustflowot a cylinder.Thiswill providebetter
conlroland a smoothercylinderstroke.
Fig.7.32showsa typicalexamplewiththe flow indicated.In a), air flowslreelyto the cylinder,in b) it flows
backto the exhaustDortof lhe valvewitha restrictedtlow.
ISO Symbol
Fig 7.34TypicalSpeedController/ FlowControl
S H U T T L EV A L V E
This is a three-ported
valvewithlwo signalpressureinletsand on€outlet.The outletis connectedto eith€r
signalinput.lf only one inpulis pr€ssurized,
the shuttlepreventsthe signalpressuretrom escapingthrough
the exhaustedsignalporton lhe oppositeside.(Fig7.35)
DO NOT COPYWTIIIOUT WRITTENPERMISSION
-88-
P
E U A T T cT E c H N o L o G Y
ISOSymbol
Fig. 7.35ShunleValve
DO NOT COPYWITHOUT WRITTEN PERMISSION
P N E U i , A T I CT E C H T { O L O G Y
U I C K E X H A U S TV A L V E S
Thiscomponentpermilsa maximumoutstrokingpistonspeedby exhaustingthe cylinderdirectlyat its porl
witha grealllow capacity,insteadof throughlhe tube and valve.
The rubberdiscclosesoff the exhaustporton the bottomas the supplyair tlowsto the cylinder.Whenthe
direclionalcontrolvalve,connecledto the inletporton top is reversed,the supplytube is exhaust€dand the
opensthe wideexhaustport.
discliftedby the cylinderpressure.lt thencloseslhe inletportand automatically
CYL
ISOSymbol
Fig 7,36.QuickExhaustValve;a: Connection,b: Withoutpressureor cylinderunderpressure,
c: tlowto cylind€r,d: exhausting
With miniaturecylinders,it happensquiteeasilythal the volumeof the tube betlveenvalveand cylinderis
as big or evenbiggerlhan that of lhe cylinder.ln thal case,lhe air in the tube is onlycompressedand
decompressed,
but nevercompletelyevacuatedand moisturecan condensatein the tubesand disturbnormal
operation.lf a shortertube is not possible,a quickexhauslvalvecan be usedto solvethe problem.
DO NOT COPYWTTHOUTWRITTENPERMISS]ON
P N E U M A T I CT E C H N O L O G Y
I B A S I CC I R C U I T S
NTRODUCTION
BasicCircuitsare asssmbliesol valveslo pertormcertaintunctions.There area limit€dnumberot
circuitsare composed.
elementarytunclionsof whicheventhe mostsophisticated
Theselunctionscan havethe abilityto:
. Control a cylinder,or
. Operateanothervalve
- for remolecontrolfroma Panel,
- to changeone valvefunctionintoanother,
- for safetyinterlocksetc.
The lattertypeof lunctionis also relerredlo as a "logicalfunclion".Thereare four basiclogicalfunctions:
.tdenttty ("YES")
. Negatlonor Inversion ("NOT')
. AND
.OR
We will not dealwith logicalmethodsot switchinghere,but we will usethe lermsas theyclearlydescribe
functionsin a singleword.
: L E M E N T A R YF U N C T I O N S
FLOW AMPLIFICATION
A largecylinderneedsa largeAir Flow.One
can avoidhavingto manuallyoperatea large
valvewithsutficientflowcapacityby usinga
largeair operatedvalveand operatingit witha
smallermanuallyoporatedvalve.Thistunctionis
called"FlowAmplification".
This is oflen
combinedwith remotecontrol:the largevalveis
clossto the cylinderbut the smallone can be
builtintoa panelfor easyaccess.
Fig, 8.1 Flowamplification
or indirectcontrolof
S l G N A LI N V E R S I O N
The methodas shownin fig. 8.1 cen alsobe
usedto changethe functionot a valvefrom
normallyopento normallyclosedor vic6versa.
It valve@ in tig. 8.2 is operated,the
pressureon the outputof valve@ disappeaF
and reappearswhenO is released.
Fig.8.2 Signallnversion:
it valve@ is operated,
thepressure
ontheoutputof valve@ disappears
andre-appears
when@ is releas€d
DO NOT COPYWTHOUT WRITTENPERMISSION
-91 -
PNEUl|ATtc TEc HNOLOGY
SELECTION
Selectionis achievedby convertingfrom a 3l2 to a 5/2 function.
The initiatingvalveO is a small3/2
manuallyoperatodvalve,th€indir€ctly
op€raledvalve@ is a 5/2 valveof a
sufticienttlow capacitylo actuatea doubJe
actingcylinder.UsingthislunctionFlow
Amplification
is also per{ormed.
One positionof the toggleswitch"lightrs"
lhe greenindicator,the othef lights"th€ r€d.
The samefunctionis also usedtor
selectionbetweentwo circuits:one of the
portsol th€5/2 valvesuppliesfor example
an automaticcircuit,lhe other,valvesfor
manualcontrol.This makessurethat no
automaticactioncan take placeduring
manualoDeration.
Flg. 8.3 Selectionbetweentwo circuitswithone
manuallyoperatedmonostable312valve
M E M O R YF U N C T I O N
A regulartype of
lunctionreouirementis to
perpetuatea momentary
valveoperationby
holdingits signalon, until
anothermomentarysignal
switchesit permanently
otl.
The red indicatoris
"memorizing"that valv€
Flg. 8.4 Switchingtrom redto greenby trippingvalve@ and from green
@ was the last to be
to red with valve @
operatedand the green
indicatorthat valveO will
give the signalto change
over.
DO NOT COPYWTI}IOUT WRITTENPERMISSION
-92-
P N E U $ A T t cT E c H t { o L o c Y
ME FUNCTIONS
A pneumaticdelayis basedon the time requiredto changethe pressurein a fixedvolume,by the airflow
)ughan orifice,As this is a meteringfunction,subjectto changingcondilionsin supplyair,certain
inconsist€ncies
shouldbe sxpected.
In addilion,do not relyon Timealonetor circuitsatety-- e.g.thereneedsto be somepositiveindicationof
a partbeingpresent,a processbeingcompleted,anctso on.
lt, witha givenvolumeand
orificewe get the pr€ssure^ime
a in fig.8.5.Eithera
volumeor a smal16r
orifice
changeit to b.
In the caseof characteristic
a,
timedelavto switcha valvewith
switchingpressureps will be lt,
b it will be increasedlo t2.
In praclice,the pressureot the
is connectedto the pilot
oi a spring retum valve and a
speedcontrolleris usedto varythe
orifice,ils built-incheckvalve
an unrestricted
tlow in the
direclionand thereforea
res€ttime.
of compressedair,
Fig. 8.5 The pressure/ time relationship
flowinglhroughan orificeintoa volume
Thereare tourditferenttime related
functions:
1. The delayof switchingON a pressur€
signal
2. The delayof swilchingOFFa pr€ssure
signal
3. A puls€to switchON a pressuresignal
4. A pressurepulseto switchOFF,
ON
InitialSignaloFF .
a) delayedat'ON'
b) d€layedat 'OFF"
c) Pulseat "ON'
d) Pulseat "OFF'
Fig. 8.6 The four timefunctions
DO NOT COPYWITHOUT WRITTENPERMISSION
-93-
P N E U tA r t c T E c H N o L o c Y
D E L A Y E D S I ' Y I T C H t N GO N
Fig.8.7 showshow a pressur€
signalcan be delayed.The signalon
the outputport (A) of valve@ appears
E variabletim€atteroperationof the
valve@. This is due to the flow
restrictionvalveand the reservoir
(whichmay be nothingmorethan a
largediametersectionof tubing).
For a veryshortdelay,the
reservoircan be omitted.
Flg. 8.7 Delayedswitchingon
D E L A Y E DS W I T C H I N GO F F
The delayedreselof a valveis
achievedin lhe sameway as b€tore,
but insleadof limitingthe air flow
towardsthe pilotportol valveb, its
exhaustis restrictod.
Fig.8.8 showsa delayin
switchinga signalott. Atteroperating
valve(Dthe indicatorimmediat€ly
goeson, bul after releasingthe
valve,the indicatorwill slay on for an
adjustableperiod.
Flg 8.8 Delayedswitchingoff
P U L S E O N S W I T C H I N GO N
lf a signalfrom a valveis passinga
normallyopenvalve,whichis operatedwith
the samesignal,therewill b€no pressureat
the outputof the latlervalve,Howeverif its
operationis delayed,the pressurecan pass
untilthe operaliontakesetfectafterthe delay.
The resultis a pressurepulseof adiustable
durationon the outputof the normallyopen
valve.
In fig. 8.9, a pulseappearsat the outputot
the normallyopenvaNe@, whenthe vatue(D
is switchedon.
Fig. 8.9 Pulseon switchingon
DO NOT COPYWITHOUT WRITTENPERMISSION
-94-
P N E U M A T I C T E C H NO L O G Y
P U L S E O N F E L E A S I N GA V A L V E
,'
Wh€nthe pressurepulsehasto
appearatlerlhe initialsignalhas been
switchedotf,lhe pressurelo produce
it mustcom€fromanolhersource.
The methodis lo simultaneously
operatea normallyopen3Y2Valve@
and pressurizea volume@ withthe
initialsignal.WhenvalveO is
released,vafue@ switchesin its
normalposition,connectingthe
volumewithils oulput.The pr€ssure
lrom the volumewill ebb awayaftera
shortperiod,adlustableby meansof
the soeedcontroller.
signal
Fig. 8.10 Pulseon a disappearing
DO NOT COPYWTTHOUTWRNTEN PERMISSION
-95-
PNEU ATIc TEcHI{OLOGV
C Y L I N D E RC O N T F O L
M A N U A LC O N T R O L
Slngte Acttng Cyllnder
Ditect Operation and Speed Control
lf a singleactingcylinderis connectedto a
manuallyop€rated312valve,it will extendwhen
lhe valveis oDeratedand retumuDonrelease.
This is the so-called'directcontrol.'ln the caseot
a largecylinder,tlowamplificalionas shownin fig.
8.1 is applied.
The only way to regulatethe outstrokingpiston
speedof a singleactingcylinderis to throttlethe
flow intoit. The speedol the returnstroke,by
meansof the spring,is seldomlimitedin practice.
.Fig.8.11Directcontrolot a singleactingcylinder
Control from two points: On
Function
A cylinderor a valvemay
be operatedin two ditf€rent
ways,lor example,manuallyor
via a signalfrom an automatic
circuit.
lf the outputsoI two 3/2
valvesare interconnected
with
a Tee, the air comingtrom one
ol the valveswill escape
throughthe exhaustof the
olher.
A shuttle valve type
applicationavoidsthis
Droblem.
ShuttleValve
Flg. 8.12 Operationof a single
actingcylindertromtwo points
DO NOT COPYWTII{OUT WRITTENPERMISSION
-96-
P
EU
ATIC TECHNOLOGY
tntetlock: AND Function
ln somecasestwo conditionshaveto be fulfilledto allowa certainoperation.A typicalexamplecouldbe
pressmay onD operateit a satetydooris closedand a manualvalveis operated.To control
thata pn€umatic
operated3/2 valve,the inpulot the manuallyoperatedvalveis
the safetydoorit tripsa mechanically
connectedto its output,so thereis an openflow pathonlyif bothvalvesare operated'
In caselhe signalsfromthe h/vovalveseachhaveanolherpurpose,as illustratedin circuilb by the two
indicators,an air operaled312valvecanperformthe AND Function:One of the signalssuppliesit, lhe other
operatesit.
Fig. 8.13Satetyinterlock:AND Function
lnverseOperction:NOT Function
Mechanicallocks,stopsfor
productson a conveyorand
similarsituationsmightrequire
a cylinderto be energizedlor
locking.Unlockingoccursby
operatinga valve.For this
typs of applicationa normally
oD€nvalvecan be used, lf
however,the samesignalfor
unlockingmustalsostartany
otherdevice,as symbolized
by the indicator(D in fig. 8.14,
a signalinversionhasto be
used,by operatinga separate
air operatednormallyopen
valve@, witha normally
closedvalveO.
Flg, 8.14 SignalInversion:the cylinderretractswh€nvalveO is tripped
DO NOT COPYWTTHOUTWRITTENPERMISSION
P
E U M A T T cT E c H | t o L o G Y
Double actlng Cyllnder
Dirccl Conlrol
The only diflerenc€betweenthe operationof a
doubleactingand a singleactingcylinderis that
a 5,/2valvehas to be usedinsteadof a 3/2. In its
normalposition(notopsrated),port"8" is
connectedwiththe supplyport "P". lt hasto be
connectedto the rod sideof the pistonif the
cylinderis naturallyin the negativeposition.
For independent
speedcontrolin both
directionsthe speedcontrolleris attachedto both
connections.
Theirorientationis oppositeto that
of a singleactingcylinderas the exhaustingair
is throttled.This givesa morepositiveand
sleadiermovementthanthrottlingthe air supply.
Insleadof supplyingiust enoughpow€rto get the
pistonmoving,an additionalloadis addedwitha
backpressure,whichincreaseswith increasing
speed,thus compensates
variationsin the load.
i
i
i
I
.Flg.8.15 Directcontrolof a doubleactingcylinder
Holding the end positions
In mostcases,a cylinderhas to maintain
its position,evenafterlhe operatingsignal
has disappeared.
This requiresthe
"Memonf functionot fig. 8.4.A bistable
valvewill stay in positionuntilswitchedtrom
the oppositeend.
In Fig.8.16,the outgoingstrokeot a
doubleactingcylinderis initiatedwithvalve
@ and retumedwithvalve@. Valve@
maintainsits positionand thereforealsothat
of the cylinder.
Valve@ will onlyoperatewhenonryone
of the manuallyoperatedvalvesis
depressed.lf both pilotportsare
pressurizedat the sametim€the spool
maintainsits primarypositionas an equal
prcssur€on an equalareacannotoverrid€
the primarysignal.
In circuitryihis phsnomenonis knownas
'ov€rlappingcommands'and is one of the
maiorproblemsin circuitdesign.
Fig. 8.16 Maintainingthe positionsot a doubleacting
DO NOT COPYWTTHOUTWRITTENPERMISSION
-98-
PNEU
A'IC
TECHI.IOLOGY
b e r e c r r N cC Y L T N D P
E oRs t r r o N s
^utometlc Return
Valve@ in the circuitof fig. 8.16can be replacedby a rollerleveroperatedvalve,trippedat the positive
end of the cylinderstroke.Th; cylinderthenswitchesvalveO backby itseltand thus returnsautomatically.
of a cylinder.
This is reterredto as reciprocation
I
I
I
Valve@
siluatedhere
Fig. 8.17SemiAutomaticreturnot a cylinder
A problemwill arisEil valve@ is not releasedwhenthe cylinderreachesthe end ol its stroke,th6 cylinder
doesnot retum.Valve@ is unableto switchvalve@ backas longas the opposingsignallrom valveO
remains.A bistiable
valvecan only be switchedwitha pilotpressurewhenthe oppositepilotinputhas b€en
exhausted.
DO NOT COPYWTTHOUTWRITTENPERMISSION
-99-
P N E U M A T TTcE c H t { o L o c Y
ll the cylinderhas lo returnunconditionally
as soonas it reachesthe end of stroke,a simplesolutionwould
be lo transformthe signalof lhe manuallyoperaledvalveintoa pulse.This is a combinationot the two
elementarylunctionsot fig. 8.9 and 8.17.
I
I
I
ValveO
situaledh€re
F19.8,18Automaticretumof a cylinder6venwitha remainingsignal
DO NOT COPYWTTHOUTWRITIEN PERMISSION
P
EU ATICTECHNOLOGV
\
|}epeattng Slrotes
By sensingbothendsof the strokewith rollerleveroperatedvalvesand usingthemto switchthe main
valve@ bact-andlorth,the cylinderwill r€ciprocate.ln orderto stopthe motionwe applyan ANDfunctionof
valvethe
fig. 8.13.Witha bistablemanuallyoperatedvalveconnectedin serieswilh the roller-operaled
position
negative
cylinderwill ceas6to cycleif switchO is tumedotf, butas beforeit willalwaysreturnto the
@
v
Fig.8.19 Repeatingstrokeas longas valve@ is operated
S E Q U E N C EC O N T R O L
H O W T O D E S C R I B EA S E O U E N C E
A few ruleshelpus in describinga cycleof movementsin an extremelyshortbut precisemanner.
Nomenclature
Eachactuatorassumesa capital lett€r.
Its positionot rest,in whicha circuitdiagramis drawn,is definedas "Z€roPosition".The oppositeend
posilionis the "1" posilion.
Pressur€signalsto switchdirectionalcontrolvalvesare called"commands",to distinguishthemfrom other
signals,e,g.from leverrollervalves.A commandfor movinga cylinderfromthe "zero"to the "1" positionis
calt€da 'posilive"command;in the caseof cylinder?', ils codeis simply'A+".Accordingly,
th€commandto
refumcylinderA is ?-".
As the restposilionis called'zero",it is logicalto codethe valvethat sensesthe rest positionof cylinder
wim 'a6". The oppositepositionis thencalled"a1".Forclarity,signalsar€alwayscodedwith lowercase
-J"A"
letters.The sensedpositionis designatedby an index.
DO NOT COPYWTIHOUT WRITTENPERMISSION
P N E U A T T cT E c H i r o L o c Y
In Fig.8,20th€secodesar6 reproducedin a schematicsetupfor clarity.This setupis calleda "Functional
Unif , as it provideseverythingrequiredto performa machinetunctionand to conlrolit.
Direction
A
+
+
aoG
lSignals: as
Fig. 8.20 FunctionalUnitwith all codes
S E Q U E N C EO F T W O C Y L I N D E R S
Withthesecodes,we can writea sequenceof two cylinderslor examplewith:
A+, B+, A-, BThe sequenceof evenlsnow becomespatentlyobvious.
Nowcomesthe queslionof wh6r€thesecommandscomefrom.The answeris quitesimple:lrom the roller
levervalvesthat sensethe endsof the stroke.They alsoneeda cod€,againquiteself-explanatory:
lhe terminalionof a command(A+, B+)will alwaysbe signaledby the roller/l€ver
valvewiththe same
letterand an indexnumber:"at", "bt", a Zero Command A- by ao, etc.
Withthesecodeswe can writethe solutionfor thg abovementionedsequenceas tollows:
A+ -) al .+B+-)bf-+A--+i0+B-*bO
We also ne€da manuallyoperatedvalvetor startingand stoppingthe sequence,it is placedin the lin6
priorto the firstcommand,A+. Shouldthe sequenceneedto conlinuethenthe startvalveshouldbe lettopen,
but it th€circuitis switchedoff in mid-cycleit will continueto operateuntilall ot the movementsin the
sequencehavebeencomplet€dand thenthe cyclewill cometo rest.This meansthatthe lastsignalbo has
app€aredbut it is unableto passthroughthe startswitch(coded"sf). This is anotherapplicationol the
elem€ntary'AND" functionof fig. 8.13.The commandA+ needsbothsignals:bg and"sf. In switchingalgebra
this is writtenas a multiplication
in normalalgebra:"st . b0'.
DO NOT COPYWITHOUT WRITTEN PERMISSION
-102-
PNEU ATIcTEcHNoLoGY
This may be referredlo as a "closedloop' circuit.The sequenceof signalsand commandsis lhen as
lollows:
Slgna,s
Commands
The samesequenceas in the blockdiagramaboveis drawnin Fig8,21as a pneumaticcircuitwith ISO
Symbols.As we havenowcodedthe rollerlevervalvesaccordinglo theirposition,thereis no needto draw
shownnearthe cylinders,or indicatethem
valvestopographically
the circuitas a mapwiththe end-of-stroke
withnumbersas in figures8.18and8.19.
The standardis to drawall the cylindersat the top, dhectlybeneaththemlheir powervalvesand below
circuitstheremay be some
thosethe valvesprovidingthe end of strokesignals.ln moresophisticated
'sf in fig.
additionalvalvesin a levelbetweenthe mainand signalvalves.This is the casewiththe startvalve
8.21.
SIngle Cycle / nepeatlng Cycle
The type of valveusedfor startingthe sequencemakesthe ditferencebetweenthe two cycles:if it is a
monostablevalv€and we trip it, one singlecyclewill be pertormed.In the caseof a bistablevalve,the cycle
will repeatcontinuously
untilwe resetit. No matterwhenwe do it, the circuitwillalwayscompletethe cycle
andthen slop.
)
Fig. 8.21Circuitlor the sequenceA+, B+,A-, B-
DO NOT COPYWTIHOUT WRITTENPERMISSION
P N E U i I A T t cT E c H N o L o G Y
O P P O S I N GC O M M A N D S
Ellmlnatlon wlth a Pulse
Clamping: Pressure Control
Shorlslrokesingl€actingcylindersare oftenusedtor clamping.Althoughth€ycan havebuilt in switches
tor electricalcontrol,thereis no secudly,ls the parl to be machinedsutficientlyclampedto withstandthe
lorcesexeriedon it duringmachining?The only reliablesignalis one that indicatessufficientpressurebehind
lhe piston.For this a "SequenceValve"is used.lt allowsthe operatorto adjustthe minimumpressurerequired
lor secureclamping.
The pressureit hasto senseis that of the clampingcylinder,so ils pilotinputhas to be connectedwitha
Tee to the cylinderport; its outputsignalwill then startthe machiningoperation,(cylinder"8").The cylinder
haslo relurnimmediatelyaft€rthe operationis tinished,i,e.the end of the stroke,valve"b1" will providethis
intormation.
Herewe face a problem:B is unableto relurnas longas the clampingcylinderA is pressurized,but also il
musl not relumand un-clampbetorethe machiningdeviceis backin the rest position.We can againusethe
basiccircuitof fig 8.9 to solvelhis problemby transforming
the remainingsignalfrom lhe sequencevalveinto
a pulse'The cycleis startedmanuallybut in practice,lheoperatorwill inserta componentfor machiningand
th€nkeepthe buttondepresseduntilthe work is completed.Seelig 8.22for clarification.
Flg. 8,22Circuitfor clampingand machining,singlerycle
Thereis howeveran imperfection:
if the operatorrel€asesth€buttonafterthe machininghas started,the
clampwill open.We haveto preventthat.The solutionis to "memorize"the manualstartingsignalwithth€
circuitof fig. 8.16.For the tunctionol valve1 in that circuitwe useda valvetor sensingthe r€stpositionof
cylinderB, a valve"bo'. But that valveis operatedin the restposition,whenclampinghas beendoneand B
has to outstroke.
DO NOT COPYWTT}IOUTWRITTEN PERMISSION
- 104-
PNEUMATIC TEC'II'IOLOGY
This meansthereis anotheropposingcommand,whichwe haveto get rid of -- by makinga pulseof ilr
t
t That resultsin the circuitof fig. 8.23:
A
B
T-I
Fig. 8.23Clampingand machiningwith addilionallocking
Cascade System
You mustadmitthatthe way in whichopposingcommandshavebeen€liminatedin the previousexample
cannotbe lhe bestone.Theremustbe a morestraighttoMardand reliablesolution.
The tru€solutionis to switchoverlappingsignalsofi, nol by timingtricks,but by switchinga selectorvalve
as in the circuitFig,8.3,The problemis to knowwher6sucha valvehasto be put in and how it is to b6
switchedand connected.
Thereis a simpleproceduretor drawings€quential
circuits,called'The CascadeSystem". The cycleis
dividedintotwo or moregroups.For furtherexplanation
we assumethatthereare onlytwo groups.Eachone
has a supplylinetromthe selectorvalve.
The divisionof the groups,tor examplecycle"A+, B+, B-, A-" is doneas follows:
Lookingat eachcommandfrom lettto right,we can sub-dividethe commandsintogroups,the rule being
that you mayonly have1 commandin eachgroupbe it either + or - e.g.:
A+, B+
groupI
lB-, A-.1
groupll
The principleremainsthe samewith longercycles,whenit hasthreeor moregroups.lt is not necessary
thal the cyclestartswitha new group;the end-of-cycle
may be in the middleof a group.The "starustop"valve
is simplyput in the lineto lhe firsl commandot the cycle.Sometimesone hasto try untilthe leastamountot
groupshasb66nfound.
DO NOT COPYWTTHOUTWRITTENPERMISSION
P N E U M A T t cT E c H N o L o c Y
Furtherrulesare explainedin the followingblockdiagram:
all turlhercommandsin groupll
all furth6rcommandsin groupl
tirstcommand
in groupI
firstcommand
in groupll
line groupI
linegroup
O
FirstCylinderValveto be switchedin group t .
@ All end of strokevalvesin group l, exceptthe last in sequence.
@ All the commandsto the mainvalvesin group I are suppliedlrom " line group 1".
The valvesensingthe end ol the laststrokein groupt switchesthe selector;
@ the line
of groupI is exhaustedand that of groupll pressurized,
rR\
Mainvalveof the cylindermakingthe firststrokein group ll ,
\g/
@ All end-ofstrokevalvesgivingthe commandsin groupll ,exc€plthe lastone,
@ All end-ofstrokevatuesgivingcommandsin groupll are suppliedfrom 'line groupll".
@ The valvesensingthe laststrokein groupllswitchesthe selectorback.
lg. 8.24 BlockDiagramof the CascadeSystem
The steps of the circuit are now quite easy. The start switch is alwaysinsert€din the line to the first
commandol the cycle.ln the exampleabove,lhe cycleendsat the end ot a group;this is not alwaysthe case
and,as mention€dabovenol necessary.
This will be demonstrated
withone €xample:the givencycleis: A+, B+, A-, C+, D+, IL B- Glf we dividethe sequencefrcm the trontwe get the resultas belowa 3 GroupCascade:
lA+, B+,1A-, C+, D+,1D- B- C-.
lf we dividethe sequencefrcm lhe rearwe lind lhal we now haveonly2 groups,as the movementsA+,D,B-,C-can all be performedwiththe samegroupair:
A+,1B+, A-, G+, D+,1IL B- C..
The cascadevalvewill be switch€don with al and b6 switchedbackwith dt. The start/ stopvalvewill be
in the connectiontromcOto lhe commandinputA+,
DO NOT COPYWTTHOUTWRITTEN PERMISSION
P N E U I , A T I CT E C H N O L O G Y
Rememberthat bothrollerlevervalves,coded wilha zero index,haveto be drawnin the opelaledposition,
as youcan s€ein the diagramof fig. 8.25for the seguenceA+, B+, B-, A-.
A
r-ll
T-l
t#
r.
zK
Flg. 8.25 Two cylindercascade-
DO NOT COPYWTIHOUT WRITIEN PERMISSION
I
B
r-1
9K
P N E U M A T I CT E C H N O L O G Y
APPENDIX
SYMBOLS
ARE
T H E S Y M B O L SF O R F L U I D P O W E RS Y S T E M SA N D C O M P O N E N T S
H
Y
D
R
A
U L I CA N D
S T A N D A B D T Z EIDN I S O 1 2 1 9 .T H E S T A N D A R DC O M B T N E S
COMPONENT
O
F
A
P N E U M A T I CC O M P O N E N T SS. Y M B O L SS H O W T H E F U N C T I O N
A
C
C O R D I N GT O
B U T D O N O T I N D I C A T ET H E C O N S T R U C T I O NA. S A N E X A M P L E :
A
C
O
N
V
E
N
T
IONAL
I N S Y M B O LB E T W E E N
I S O , T H E R EI S N O D I F F E R E N C E
A
L
T
H
O
U
G
HS O M E
D O U B L EA C T I N GC Y L I N D E RA N D A T W I N B O D C Y L I N D E R ,
F
O
F
T H E I RO W N S Y M B O L S
M A N U F A C T U R E RH
SA V E I N T R O D U C E D
CLARIFICATION.
A I R T R E A T M E N TE O U I P M E N T
The basicSymbollor Air Cleaningand Air DryingComponentsis a diamondwiththe inpuland output
drawnas a linefromthe lettand rightcorners.The specificlunctionis indicatedinsidethe diamondwith a few
furth€rsymbols.The tablebelowwill€xplainitself.
The basicsymbolfor pressureregulatorsis a squarewiththe inputand outputdrawnin the middleof the
leftand rieht.lide.Airflowis indicatedwithan anow,the settingspringwitha zigzag,crossedby an arrowtor
Th6 rirainsymbolsare:
adjuslirbility.
ISOSYMBOLSfor AIR TREATMENT
+
+ +
,A
\I/
Air
Heater
Heat
Exchanger
Multistage Lubricator
MicroFilter
-
Pressure
Reoulation
-Z-
E-
,--E_ A
Ll s fr-++tJ:
Basic
Symbol
Adiustable Pressure Regulator
Regulator with r€lief
Setting
Spring
Units
)
FRL Unit.detailed
I
Dift€renlial Pressure
Pressure
Gauge
Regulator
FRLUnit,
simplitied
Fig. A.1 Symbolslor Air TreatmentComponentsISO 1219
DO NOT COPYWITHOUT WRITTENPERMISSION
P N E U t r t a r l cT E c H N o L o c Y
ACTUATORS
A linearcylinderis drawnas a simplitied
is madebetweenpistonandother
crosssection.Nodifference
typesof cylinders.
A rolaryactuatorhasitsownsymbol;herealso,it appliesforall kinds,withrackandpinion
or van€€tc.
Singl€ActingCylinder,
pushtype
t-n
t
T-T
l
SingleActingCylinder,
pulltype
l
DoubleActing
DoubleActingCylinderwith
adjustableair
DoubleActingCylinder,
withdoubleend rod
RotaryActuator,
doubleActing
Flg. A-2 ISOActuatorSymbols
VALVES
The basicsymbolfor a directionalcontrolvalveis a groupof squares.The inputand exhaust(s)are drawn
on the bottom,the outputson top. Thereis one squarelor eachfunction.As valveshavetwo or moredifferent
functions,squaresare linedup horizontally,
the ruleof thumbis thal eachfunctionis representedby a square:
mt \
Insidethe square,flowpathsare indicatedby anowsV
shut portsare shownwiththe symbolT.
\ betweenthe interconnected
ports,intemally
Externally,on the bottomot lhe square,air supplyis shownwitn6 anAexhaustswithV.
A supplyline is drawnas a solidline,
a pilotline is dashed
exhaustlinesare dottod
Symbolslor the operatoraare drawnon the endsof the doubleor triplesquare.
The followingoperatorsymbolsare shownfor th€left-handside,exceptthe spring,whichis alwayson the
oppositeside of an operatoras it is a res6tmechanism,bul is technicallytermedas an op€rator.ll operators
are placedon the righthandsidethey will be in reverse(flippedhorizontally).
DO NOT COPYWTHOUT WRMTEN PERMISSION
- 109-
PNEu Atlc TEcHNoLoGY
The mainopeEtorsymbolsare:
ReturnSpring(in facl not an
operator,bul a built-inelement)
BollerLever:
M
CE
general:
Manual
oPerators:
PushButton:
Mechanical(plunge0:
-.
one'wayFlollerLever:
qr-
Lever:
=
r
Button:
Push-Pull
F
\cE
i--
(F-
I
I
Delenlfor mechanicaland manualoperators(makesa monostablevalve
D&
bistable):
ni, Operationis shownby drawingthe (dashed)signalpressurelineto
rtreside of the squareithe directionof the signalllow can be indicatedby ---D--'
a trianole:
o,, oplration for pilotedoperationis shownby a rectanglewitha triangle. l-El
Thissymbolis alwayscombinedwithanotheroperator.
II
operatio
on"o solenoid
"
I
I
I
piloted
operation l7T1
solenoid
m
I The table A-3 below explainsho\r,,these symbol€lemenlsare put togetherto lom a completevalve
symbol.
I
fi'ffi' -d*h" s;li;l
d:?Hfl"
+m f,'ffi'-ffik" s&ia
^t
oR
lW
tr,
AJ LI-l
T\ rr\rr Al
T i
\ \
t ry
/
|-f-l l-
\
,
|
\
\
. \
/
\
fT-T-|.
'
Exhaust
V "='z
t
O --"'.-6!
lnput dos€d,
Inpul
Mochanical conftict€dto
OutDut
Operation
exhaust€d
O.rtout
-
/
\
\
\
/ Manuallvooerated, \ \
Open312valve,
i ,Normally
ITTFI
t
/
/
/
^ ^',
ffiil#,iilf';i'"";J\Jffi
wirhsprinsRetum
"--t#
^na,*ry
R€lum
Spnng
H NM
lnDut
dos€d.
Input
'Ouput
Fetum
M€chanicel conn€ctedto gxhaustedDpnng
Output
Operalion
o R =
rr|
M
lT\ |
I
Mechanically
Operated,
normallyclosed312
(non-passing)
ValvewithSpringReturn
ainsrpptv
6/
\o.,n"r.
Fig. A-3 Howto combineValveSymbols
DO NOT COPYWTTHOUTWRITIEN PERMISSION
- 110-
P
E U M A T t cT E c H N o L o c v
ctRcurTs
B A S I CR U L E S
A circuitdiagtamis drawnin therestpositionol thecont.olled
machine,
withthesupplyunderpressure,
but
in lhecaseof mixedcircuits,
power.Allcomponents
withoutelectrical
mustbedrawnin thepositions
resulting
fromlh6seassumptions.
Flg.A- 4 illustrates
this:
fhis cylinderchamberandthe rod sideot
pistonar€undsroressure:rod
Feat cylinder
chamberandthis line
are exhausted
Thisline is in connectionwith
lhe supplylhroughthe valve:
il is oressurized
In resttheE is no solenoid€nergized:
operator
inacliveandvalvepositiondefinsdby the spring
As springdefinesposition,
thissquareis in function
Flg. A.4 BasicRulesfor composingcircuitdiagrams
REST POSITION
Mechanically
operatedvalves,controllingthe restpositionsol the cylinderdrivenparts,are operatedin rest
and haveto be drawnaccordingly:withthe externalconnectionsdrawnto the squareon the operatorsid€.In
a normallyclosed3/2 valv€,the outputis then connectedwiththe supplyand theretoreunderpressure.
Equally,if the signallineto a monostabloair operat€dvalveis underpressure,ii hasto be drawnin the
operatedposition.
Furtherrulesar6:
ruru
ManuallyoperatedValves
delent,mustcorre€pond
wlthvalveposition
no pEssut€
|
r-l
|
T
I
| \---t_
| \
I^^,
-----6-v-
3/2,normallyclosed
.
HJ
IT
pressure
I -l.
ff. .
i/
noon,uun
\
o*ur"
-I_\ ]/VV
(,
3i/2,normallyopen
monoslable
valvesnevet ooerated
3il2,normally
bistablevalves:both positionspossible.
Fig. A-5 Bulesconcemingvalvepositions:ManualOperation
DO NOT COPYWTTHOUTWRITfEN PERMISSION
- 1 t 1-
P r ' I E UT , A T I C T € C H N O L O G Y
operatedValves
Electrically
andpneumatically
Alr operatedvalves may be operatedIn rest
jg_ejg:s_uP_+,_
Solenoldsare never operaledIn roat
Flg.A.6Rul€sfor restposilionol solenoidand air operatedvalves
Mechanically
operatedValves
No valvewlth lndex'1" ls
All valveswlth Index"0' ar€
Fig. A-7 Ruleslor restpositionof mechanically
operatedvalves
C I R C U I TL A Y O U T
In a circuitdiagram,the flowof the workingenergyis drawnfromthe bottomto th€top and the sequenceof
the workingcyclelrom th6 leftto the right.Consequ€ntly,
thd air supply(FRL)Unitis situatedin the lowerleft
corner,lhe cylinderlhat pertormsthe firststrokeof the cycl€,in the upperleftcomeretc.
The powervalvesare drawndirectlybelowtheircylinders;th6ytorma 'PowerUnit'thalis codedwitha
capitaffetter(seeNomenclalure).
In purelypneumaticcircuits,312rollerfiever
valves,controllingthe €nd
posilionsof the cylinderdrivenmachinepartrs,
are situat€din a low€rlevel.
Betweenpowervalvesand the powerunilsth€remaybe additionalvalvesto €nsurethe correclsequence
(memorylunction),and,som€times,
additionalvalvesto realizec€rtaininterlocksby logicalfunctions.Th6
bloc* diagramot fig. 6 explainsthis moreetfectivelythandescriptions.
DO NOT COPYWTTHOUTWRITTENPERMISSION
- 112-
P r ' r E U M A T rTcE c H N o L o c Y
Laststrokeof th6 cycle
Firststrokeot the cycle
LOGICLevel
Memories,
AND's,OR's,
Timingsetc.
,fsrll
tI
m
SIGNALINPUTLevel
Codes:a9, ar ,bo ,br ,%
*{I"il"ilqil
andcl
Flg, A€ The basiclayoutof.apneumalic.circuit
diagram.
NOMENCLATURE
Previously,pneumaticcircuitsweredrawn'topographically,
withthe roller-operated
valvespositionedon
top, drawnas beingoperatedby 'cams'on th6 cylinderrodends.This is the situationwe will haveon the
trainingkit whensimulatinga machinecontrol.In modemmoresophisticated
circuits,this leadsto a muttitud€
of crossinglines.The modemand only reasonabl€
methodis to linethe symbolsof theseroller-operatod
valvesup, as in Fig.A-8, and posilionthemto allowverticalsignallines,straightto theirdestination.Their
placeon th€machineis then indicatedwith a selt-explanatory
code.
This selFexplanation
is achievedby consld€dng
certainequipm€ntto form one functionalset.The starting
pointis the "PowerUnit"whichis codedwith a capitallefter.This can be in alphabetical
order,in the sequence
of the workingcycle,or initialsot th€operation,{or exampbrc" fur clamping;"D" for Drillingetc.
The (mention€d)
lunctional sef includesthe actuator,the powervalveand the two roller/lever
valvesthat
detectthe two end positions.
The rest positionis codedwith an indexf0', the fuorkingposition"with a "1". Notethat the restpositionis
the real positionof the movingmachinepartsand not that of the pistonrod.Only in simulationwitha training
kit do we consid€r'rodin" as the rest Dosition.
DO NOT COPYWTTFIOUTWRITTEN PERMISSION
-113-
P N E U M A T I C T E C HN O L O G Y
valv€s,and commands,signal
betweena signal,producedby lhe roller/lever
W6 haveto ditferentiate
.
I pressuresthai operatelhe powervalvesilnsimplecircuits,a signalcan be a command.Thenthe codeof the
signaldelinesthe source(thenow completedactionon the machin€),and the codeof th€commandtells
whichnextmovementwill be started.In morecomplicatedcircuits,a commandwill be the outpulof a valve
usedtor a logicaltunclion.
valvesoperatedin the rest positionhavean indexzero.Those
As th€r6stoositionis rc', all end-of-stroke
position")
havean index"1".Fig.A-9 showsa situationwitha littingiable
(\^,ork
in the opposlteend
op€rat€d
valv€
is switchedon in the threeversions:as a situationsketch,
starvstop
movingup and downas longas the
simulated
withthe trainingkil and lhe circuitdiagram'
looks
when
an imDression
of howlhe circuit
CIRCUIT
Flg. A-9 Comparisonof a situationsketchwiththe simulationset-upand the ckcuildiagram
DO NOT COPYWTTIIOUTWRITTENPERMISSION
-114-
P EUxA'Ic TEcHNoLoGY
S A M P L ED I A G B A M S
We will lookat this in a samplediagram.DiagramA-10is the circuittor the sequenc€:
"A+, B+, B-, A-".
ll is dividedintothe thr€elevels,the powersectionon top, the signalinputrson the bottomand in between
the 'signalproc€ssing'.
This latlerterm means,thatthe signalstromth€machinenegdadditionalsignals
ancuorfogicalinterconnection
lo g€tthe rightsequsnce.In this case,a memoryisrequiredto be switchedby
the commands"M+"and "M-".Youwill r€cognizethis valyeas the cascadevalvain tig. 8.25,whichis of
coursea memory,Logicalfunctionsare lhe seriesconnections(ANDfunctions)of lor exampl€the start/stop
valvewiththe memory.The ellect is, that as longas the cylinderA is not backin its rest positionthe startis
not effective.Onlyafteroperationof the rollerlevervalvea6,the memorywill be resetintothe drawnposition
and supplyair to lhe startvalve.This allowsrepeatingcyclesby switchingthe starystopvalve"ON".Resetting
it intothe drawnrest positionwill causethe sequenceto stopaftercompletionof the runningcycle.
POWERLevel
<A-_CommandAI
I
co'Uand-Ll
LOGICLevel
Signal
Processing
staru$op
Signalbl
and i--CommangEEi
M-l
I
- -1
.
Siqnalao and
I CommandM+
t
lI
SIGNALLevel
Checkingthe machine
Fig. A-10 SampleDiagram
DO NOT COPYWTHOUT WRITIEN PERMISSION
-115-
P N E U M A T t cT E c x N o L o c Y
Industrialpneumaticswill continueto be a reliable,costetticient,and productivemeansto automate
an eflectivewayto storeenergyand
machinesand processes.lt remains,aftera cenluryof applications,
worK.
orovroework.
orovide
E
,=i,=&!i:il{:?rdtfiiei*
smarterproducts;machinesthat will, on
an elementarylevel,thinkaboutwhat
lhey'redoingand respondto ever
changingcircumstances.Pneumatic
componentswill continueto providelhe
powerto buildthe dreamsof emerging
tuturetechnologies.
The sectionof a machineshownon
the left shouldserveas a reminderthat:
1 . lherewill alwaysbe a needlo
automale.....there
areso manyold
machinesand fixturesthat can be
mademore€fficientand more
productive
generalrule
2. simpleris b€tter.....a
o.
safestis notiust th6 bestway-- it is
the ONLYway. Neverdesigna
circuit,usea product,or operatea
machinewithoutsafetyas your
primaryconc6m.
The tuturerestson the lundamentals.
To continuein this fieldot study,consultyour localSMCotficeor distributortor additionalt6rittitles,
workbooks,and courseoflerings.
DO NOT COPYWTTHOUTWRTITENPERMISSION
- 116-
WorldWideQS\E Support...
(762-7621)
North American Branch Offices Fora branchofficenearyoucall:1-800-SMC-SMC1
SMC Pneumatics Inc. (Atlanta)
1440 Lakes Parkway,Suite 600
Lawrenceville,GA 30043
Tel: (770) 624-1940
FAX: (770) 624-1943
SMC Pneumatics Inc. (Cleveland)
2305 EastAurora Rd., Unit A-3
Twinsburg,OH 44087
Tel: (330) 963-2727
FAX:(330) 963-2730
SMC Pneumatics lnc. (Milwaukee)
16850W. Victor Road
New Berlin.Wl 53151
Tel: (414) 827-0080
FAX: (414) 827-OO92
SMC Pneumatics lnc. (Richmond)
5377 Glen Alden Drive
Richmond,VA 23231
Tel: (804) 222-2762
FAX: (80a) 222-5221
SMC Pneumatics lnc. (Austin)
2324-D Ridgepoint Drive
Austin,TX 78754
Tel: (512) 926-2646
FAX: (512) 926-7055
SMC Pneumatics lnc. (Columbus)
3687 Corporate Drive
Columbus,OH 43231
Tel: (614) 895-9765
FAX: (614) 895-9780
SMC Pneumatics Inc. (Mnpls.)
990 Lone Oak Road, Suite 162
Eagan,MN 55121
Tel: (651) 688-3490
FAX:(651)688-9013
SMC Pneumatics Inc. (Rochester)
245 Summit Point Drive
Henrietta,NY 14467
Tel:(716)321-1300
FAX:(716)321-1865
SMC Pneumatics Inc. (Boston)
Zero CentennialDrive
Peabody,MA01960
Tel: (978) 326-3600
Fax: (978) 326-3700
SMC Pneumatics Inc. (Dallas)
Ste.815
12801N. StemmonsFrutry,
Dallas,TX 75234
rel: (972\ 406-0082
FAX: (972) 406-9904
SMC Pneumatics Inc. (Nashville)
5000 LinbarDrive,Suite 297
TN 37211
Nashville,
Tel:(615)331-0020
FAX:(615)331-9950
SMC Pneumatics lnc. (S.F.)
85 NicholsonLane
San Jose,CA 95134
Tel: (408) 943-9600
FAX: (408) 943-9111
SMC Pneumatics lnc. (Charlotte)
5029-8 West W.T.Hanis Blvd.
Charlotte,NC 28269
Tel: (704) 597-9292
FAX: (704)596-9561
SMC Pneumatics lnc. (Detroit)
2990 TechnologyDrive
RochesterHills,Ml 48309
Tel: (248) 299-O2O2
FAX: (2a8) 293-3333
SMC Pneumatics lnc. (Newark)
3434 US Hwy.22 West, Ste. 110
Somerville,NJ 08876
Tel: (908) 253-3241
FAX: (908) 253-3452
SMC Pneumatics Inc. (St. Louis)
4130 RiderTrail North
Earth City, MO 63045
Tel: (314)209-0080
FAX: (314) 209-0085
SMC Pneumatics Inc. (Chicago)
27725 Diehl Road
Warrenville,lL 60555
Tel: (630) 393-0080
FAX: (630)393-0084
SMC Pneumatics Inc. (Houston)
9001Jameel,Suite180
Houston,TX77O4O
Tel: (713) 460-0762
FAX:(713)460-1510
SMC Pneumatics Inc. (Phoenix)
2001 W. MelindaLane
Phoenix,AZ85027
Tel: (623)492-0908
FAX: (623) 492-9493
SMC Pneumatics Inc. (Tampa)
8507-HBenjaminRoad
Tampa,FL 33634
Tel: (813)243-8350
FAX: (813) 243-8621
SMC Pneumatics Inc. (Cincinnati)
4598 OlympicBlvd.
Erlanger,KY 41018
Tel: (606) 647-5600
FAX: (606) 647-5609
SMC Pneumatics Inc. (L.A.)
14191MyfordRoad
Tustin.CA 92780
Tel: (714\ 669-1701
FAX:(714)669-1715
SMC Pneumatics Inc. (Portland)
14107N.E.AirportWay
Portland,OR 97230
Tel: (503) 252-9299
FAX: (503) 252-9253
SMG Pneumatics Inc. (Tulsa)
10203A East 61st Street
Tulsa.OK 74146
Tel: (918) 2s2-782O
FAX: (918) 252-9511
Europe
ENGLAND
SMC Pneumatics(U.K.) Ltd.
GERMANY
SMC Pneumatik GmbH
ITALY
SMC ltalia SpA
FRANCE
SMC PneumatiqueSA
HOLLAND
SMC Controls Bv
SWEDEN
SMC Pneumatics Sweden AB
SWITZERLAND
SMC PneumatikAG
AUSTRIA
SMC Pneumatik GmbH
SPAIN
SMC Espafra,S.A.
IRETAND
SMC Pneumatics (lreland) Ltd.
Asia
JAPAN
SMC Corporation
KOBEA
SMC Pneumatics Korea Co., Ltd.
CHINA
SMC (China) Co., Ltd.
HONG KONG
SMC Pneumatics (Hong Kong) Ltd.
SINGAPORE
SMC Pneumatics (S.E.A.)Pte. Ltd.
PHILIPPINES
SMC Pneumatics (Philippines),Inc.
MALAYSIA
SMC Pneumatics (S.E.A.)Sdn. Bhd.
TAIWAN
SMG Pneumatics (Taiwan) Co., Ltd.
THAILAND
SMC Thailand Ltd.
INDIA
SMC Pneumatics (lndia) Pvt., Ltd.
North America
CANADA
SMC Pneumatics (Canada) Ltd.
MEXICO
SMC Pneumatics (Mexico) S.A. de C.V.
South America
AFGENTINA
SMC Argentina S.A.
CHILE
SMC Pneumatics (Chile) Ltda.
Oceania
AUSTRALIA
SMC Pneumatics (Australia) Pty. Ltd.
NEW ZEALAND
SMC Pneumatics (N.2.) Ltd.
SMCoffers the samequality and engineeringexpertisein many other pneumaticcomponents
Valves
DirectionalControlValves
ManualValves
Mufflers
ExhaustCleaners
Quick ExhaustValves
Valves
ProoortionalValves
MechanicalValves
MiniatureValves
FluidValves
Cylinders/Actuators
CompactCylinders
MiniatureCylinders
RodlessCylinders
RotaryActuators
PneumaticGrippers
Vacuum
VacuumEjectors
VacuumAccessories
Instrumentation
Pneumatic
Positioners
Pneumatic
Transducers
SMC PneumaticsInc.
P.O.Box 26640, Indianapolis,lN 46226
Tel:(317)899-4440.FAX:(317)899-3102
O 1978-1999SMC Pneumatics,Inc.All RightsReserved.
RevisedOctober1999
Air PreparationEquipment
Filters-Regulators-Lubricators
Coalescing
Filters
MicroMistSeDarators
Fittings
Air Fiftings