Textbook
Festo Didactic
574181 en
HydraulicsElectrohydraulicsFundamentals
Hyd
raul
ics
Elec
troh
ydra
ulic
s, F
unda
men
tals
T
extb
ook
Festo worldwide
ArgentinaFesto S.A.Edison 2392(1640) MartínezProv. Buenos AiresTel. +54 (011) 4717 82 00,Fax +54 (011) 47 17 82 82E-mail: [email protected]
AustraliaFesto Pty. Ltd.Head Office (Melbourne)179-187 Browns RoadP.O. Box 261Noble Park Vic. 3174Tel. +61(0)3 97 95 95 55,Fax +61(0)3 97 95 97 87E-mail: [email protected]
AustriaFesto Gesellschaft m.b.H.Linzer Straße 2271140 WienTel. +43 (0)1 910 75-0, Fax +43 (0)1 910 75-250E-mail: [email protected]
BelarusIP FestoMasherov avenue, 78220035 MinskTel. +375 (0)17 204 85 58,Fax +375 (0)17 204 85 59E-mail: [email protected]
BelgiumFesto Belgium saRue Colonel Bourg 1011030 BruxellesTel. +32 (0)2 702 32 11, Fax +32 (0)2 702 32 09E-mail: [email protected]
BelgiumFesto Belgium nvKolonel Bourgstraat 1011030 BrusselTel. +32 (0)2 702 32 11, Fax +32 (0)2 702 32 09E-mail: [email protected]
BrazilFesto Brasil LtdaRua Guiseppe Crespi, 76Jd. Santa Emília04183-080 São Paulo / SP -BrasilTel. +55 (11) 5013-1600,Fax +55 (11) 5013-1801E-mail: [email protected]
BulgariaFesto EOOD1592 SofiaBul. Christophor Kolumb 9Tel. +359 (0)2 960 07 12,Fax +359 (0)2 960 07 13E-mail: [email protected]
CanadaFesto Inc.5300 Explorer DriveMississauga, Ontario L4W 5G4Tel. +1 (0)905 624 90 00,Fax +1 (0)905 624 90 01E-mail: [email protected]
ChileFesto S.A.Avenida Américo Vespucio, 760PudahuelSantiagoTel. +56 2 690 28 00, Fax +56 2 690 28 60E-mail: [email protected]
ChinaFesto (China) Ltd.1156 Yunqiao Road,Jinqiao Export Processing Zone,Pudong,Shanghai 201206Tel. +86 21 60 81 51 00, Fax +86 21 58 54 03 00E-mail: [email protected]
ColombiaFesto Ltda.Autopista Bogotá - Medellín Km 6 (costado sur)Tenjo, CundinamarcaTel. +57 (1) 865 7729,Fax +57 (1) 865 7729 Ext. 287E-mail: [email protected]
CroatiaFesto d.o.o.Nova Cesta 18110000 ZagrebTel. +385 (0)1 619 19 69,Fax +385 (0)1 619 18 18E-mail: [email protected]
Czech RepublicFesto, s.r.o.Modřanská 543/76147 00 Praha 4Tel. +420 261 09 96 11, Fax +420 241 77 33 84E-mail: [email protected]
DenmarkFesto A/SIslevdalvej 1802610 RødovreTel. +45 70 21 10 90, Fax +45 44 88 81 10E-mail: [email protected]
EstoniaFesto OY AB Eesti FiliaalA.H. Tammsaare tee 118B12918 TallinnTel. +372 666 1560, Fax +372 666 15 6E-mail: [email protected]
FinlandFesto OyMäkituvantie 9PL 8601511 VantaaTel. +358 (09) 87 06 51,Fax +358 (09) 87 06 52 00E-mail: [email protected]
FranceFesto EurlZA des Maisons Rouges8 rue du clos sainte Catherine94360 Bry-sur-MarneTel. +33 (0) 820 20 46 40 (numéro indigo),Fax +33 (0) 820 20 46 41E-mail: [email protected]
GermanyFesto Didactic GmbH & Co. KGRechbergstr. 373770 DenkendorfGermanyTel. +49 (0)711 346 70,Fax +49 (0)711 34 75 48 85 00E-mail: [email protected]
GermanyFesto AG & Co. KGPostfach73726 EsslingenRuiter Straße 8273734 EsslingenTel. +49 (0) 711 347 0, Fax +49 (0) 711 347 2628E-mail: [email protected]
GreeceFesto Ltd.40 Hamosternas Ave.P.C. 11853 AthensTel. +30 210 341 29 00, Fax +30 210 341 29 05E-mail: [email protected]
Hong KongFesto Ltd.6/F New Timely Factory Building,497 Castle Peak Road,Kowloon, Hong KongTel. + 852 27 43 83 79, Fax + 852 27 86 21 73E-mail: [email protected]
HungaryFesto Kft.Csillaghegyi út 32-34.1037 BudapestHotline +36 1 436 51 00Tel. +36 1 436 51 11, Fax +36 1 436 51 01E-mail: [email protected]
IndiaFesto Controls Private Ltd.Festo Controls Pvt. Ltd.35/3, Shamanna GardenBannerghatta RoadBangalore 560 030Tel. +91 (0)1800 425 0036,Fax +91 (0)1800 121 0036E-mail: [email protected]
IndonesiaPT. FestoJl. Tekno V Blok A/1 Sektor XIKawasan Industri BSDSerpong -Tangerang 15314Banten - IndonesiaTel. +62 (0) 21 27 50 79 00,Fax +62 (0) 21 27 50 79 98E-mail: [email protected]
IranFesto Pneumatic S.K.# 2, 6th street, 16th avenue,Km 8, Special Karaj RoadP.O.Box 15815-1485Teheran 1389793761Tel. +98 (0)21 44 52 24 09,Fax +98 (0)21 44 52 24 08E-mail: [email protected]
IrelandFesto LimitedUnit 5 Sandyford ParkSandyford Industrial EstateDublin 18Tel. +353 (0)1 295 49 55,Fax +353 (0)1 295 56 80E-mail: [email protected]
IsraelFesto Pneumatic Israel Ltd.P.O. Box 1076Ha'atzma'ut Road 48Yehud 56100Tel. +972 (0)3 632 22 66,Fax +972 (0)3 632 22 77E-mail: [email protected]
ItalyFesto SpAVia Enrico Fermi 36/3820090 Assago (MI)Tel. +39 02 45 78 81, Fax +39 02 488 06 20E-mail: [email protected]
JapanFesto K.K.1-26-10 HayabuchiTsuzuki-kuYokohama 224-0025Tel. +81 (0)45 593 5610 / -5611,Fax +81 (0)45 593 5678E-mail: [email protected]
Korea SouthFesto Korea Co., Ltd.Gasan Digital 1-roGeumcheon-guSeoul #153-803Tel. +82 1666 0202, Fax +82 (0)2 864 70 40E-mail: [email protected]
LatviaFesto SIAA. Deglava iela 601035 RigaTel. +371 67 57 78 64, Fax +371 67 57 79 46E-mail: [email protected]
LithuaniaFesto, UABPartizanų 63M50306 KaunasLietuvaTel. +370 (8)7 32 13 14, Fax +370 (8)7 32 13 15E-mail: [email protected]
MalaysiaFesto Sdn. Berhad10 Persiaran IndustriBandar Sri DamansaraWilayah Persekutuan52200 Kuala LumpurTel. +60 (0)3 62 86 80 00,Fax +60 (0)3 62 75 64 11E-mail: [email protected]
MexicoFesto Pneumatic, S.A.Av. Ceylán 3,Col. Tequesquináhuac54020 TlalnepantlaEstado de MéxicoTel. +52 (01)55 53 21 66 00,Fax +52 (01)55 53 21 66 55E-mail: [email protected]
NetherlandsFesto B.V.Schieweg 622627 AN DelftTel. +31 (0)15 251 88 99,Fax +31 (0)15 251 88 67E-mail: [email protected]
New ZealandFesto Ltd.20 Fisher CrescentMount WellingtonAucklandTel. +64 (0)9 574 10 94, Fax +64 (0)9 574 10 99E-mail: [email protected]
NigeriaFesto Automation Ltd.Motorways Centre, First Floor, Block CAlausa, Ikeja,LagosTel. +234 (0)1 794 78 20,Fax +234 (0)1 555 78 94E-mail: [email protected]
NorwayFesto ASOle Deviks vei 20666 OsloTel. +47 22 72 89 50, Fax +47 22 72 89 51E-mail: [email protected]
PeruFesto S.R.L.Amador Merino Reyna 480San IsidroLimaTel. +51 (1) 219 69 60, Fax +51 (1) 219 69 71E-mail: [email protected]
PhilippinesFesto Inc.KM 18, West Service RoadSouth Super Highway1700 Paranaque CityMetro ManilaTel. +63 (2) 77 66 888, Fax +63 (2) 82 34 220/21E-mail: [email protected]
PolandFesto Sp. z o.o.Janki k/Warszawyul. Mszczonowska 705090 RaszynTel. +48 (0)22 711 41 00,Fax +48 (0)22 711 41 02E-mail: [email protected]
PortugalFesto – Automação, Unipessoal, Lda.Rua Manuel Pinto De Azevedo, 567Apartado 8013P-4109601 PortoContact Center: 707 20 20 43Tel. +351 22 615 61 50, Fax +351 22 615 61 89E-mail: [email protected]
RomaniaFesto S.R.L.St. Constantin 17010217 BucurestiTel. +40(0)21 403 95 00,Fax +40 (0)21 310 24 09E-mail: [email protected]
RussiaOOO Festo-RFMichurinskiy prosp., 49119607 MoscowTel. +7 495 737 34 00, Fax +7 495 737 34 01E-mail: [email protected]
SingaporeFesto Pte. Ltd.6 Kian Teck WaySingapore 628754Tel. +65 62 64 01 52, Fax +65 62 61 10 26E-mail: [email protected]
SlovakiaFesto spol. s r.o.Gavlovicová ul. 183103 Bratislava 3Tel. +421 (0)2 49 10 49 10,Fax +421 (0)2 49 10 49 11E-mail: [email protected]
SloveniaFesto d.o.o. LjubljanaIC Trzin, Blatnica 81236 TrzinTel. +386 (0)1 530 21 00,Fax +386 (0)1 530 21 25E-mail: [email protected]
South AfricaFesto (Pty) Ltd.22-26 Electron AvenueP.O. Box 255Isando 1600Tel. +27 (0)11 971 55 00,Fax +27 (0)11 974 21 57E-mail: [email protected]
SpainFesto Pneumatic, S.A.U.Avenida Granvia, 159Distrito Económico Granvia L'H08908 Hospitalet de LlobregatBarcelonaTel. +34 901243660, Fax +34 902243660E-mail: [email protected]
SwedenFesto ABStillmansgatan 1Box 21038200 21 MalmöTel. +46 (0)20 38 38 40, Fax +46 (0)40 38 38 10E-mail: [email protected]
SwitzerlandFesto AGMoosmattstrasse 248953 Dietikon ZHTel. +41 (0)44 744 55 44,Fax +41 (0)44 744 55 00E-mail: [email protected]
TaiwanFesto Co., Ltd.Head Office9, Kung 8th RoadLinkou 2nd Industrial ZoneLinkou Dist., New Taipei City24450 Taiwan, R.O.C.Tel. +886 (0)2 26 01-92 81,Fax +886 (0)2 26 01 92 86-7E-mail: [email protected]
ThailandFesto Ltd.Viranuvat Building, 6th - 7th Floor.1250 Bangna - Trad Road (Soi 34)Bangna, Bangkok 10260Tel. +66 2746-8700, Fax +66 2746-8370E-mail: [email protected]
TurkeyFesto San. ve Tic. A.S.Tuzla Mermerciler OrganizeSanayi Bölgesi 6/1834956 Tuzla - Istanbul/TRTel. +90 (0)216 585 00 85,Fax +90 (0)216 585 00 50E-mail: [email protected]
UkraineDP Festoul. Borisoglebskaya,1104070, KievTel. +380 (0)44 233 6451,Fax +380 (0)44 463 70 96E-mail: [email protected]
United KingdomFesto LimitedApplied Automation CentreCaswell RoadBrackmills Trading EstateNorthampton NN4 7PYTel. ++44 (0)1604 / 66 70 00,Fax ++44 (0)1604 / 66 70 01E-mail: [email protected]
United StatesFesto Corporation (New York)395 Moreland RoadP.O. Box 18023Hauppauge, NY 11788Call Toll-free 800/993 3786Fax Toll-free 800/963 3786Tel. +1(631) 435 08 00, Fax +1(631) 435 80 26E-mail: [email protected]
VenezuelaFesto C.A.Av. 23 esquina con calle 71N° 22-62, Edif. Festo.Sector ParaísoMaracaibo - VenezuelaTel. +58 (261) 759 11 20/759 41 20/759 44 38,Fax +58 (261) 759 04 55E-mail: [email protected]
VietnamFesto Co Ltd(Cong Ty TNHH FESTO)No. 1515 – 1516 Van Dai Dong StreetWard An Phu, District 2Ho Chi Minh CityTel. +84 (8) 62 81 44 53 – 4454,Fax +84 (8) 62 81 4442E-mail: [email protected]
T B P A
BA
TP
M1 M2
Order no. 574181
Revision level: 08/2013
Authors: Renate Aheimer, Christine Löffler, Dieter Merkle, Georg Prede,
Klaus Rupp, Dieter Scholz, Burkhard Schrader
Editor: Frank Ebel
Graphics: Doris Schwarzenberger
Layout: 09/2013, Frank Ebel
© Festo Didactic GmbH & Co. KG, 73770 Denkendorf, Germany, 2013
Internet: www.festo-didactic.com
E-mail: [email protected]
Reproduction, distribution and utilisation of this document, as well as the communication of its contents to
others without explicit authorisation, is prohibited. Offenders shall be held liable for damages. All rights
reserved, in particular the right to file patent, utility model and registered design applications.
© Festo Didactic GmbH & Co. KG 574181 3
Contents
Preface ________________________________________________________________________________ 10
1 The functions of a hydraulic system __________________________________________________ 11
1.1 Hydraulics – what does it mean? _____________________________________________________ 11
1.2 Stationary hydraulics ______________________________________________________________ 11
1.3 Mobile hydraulics _________________________________________________________________ 12
1.4 Attributes of hydraulics ____________________________________________________________ 13
2 Physical fundamentals of hydraulics _________________________________________________ 15
2.1 Pressure ________________________________________________________________________ 15
2.2 Pressure transmission _____________________________________________________________ 18
2.3 Force transmission ________________________________________________________________ 19
2.4 Displacement ratio ________________________________________________________________ 20
2.5 Pressure boosting _________________________________________________________________ 21
2.6 Volumetric flow rate _______________________________________________________________ 22
2.7 Continuity equation _______________________________________________________________ 22
2.8 Pressure measurement ____________________________________________________________ 23
2.9 Temperature measurement _________________________________________________________ 24
2.10 Volumetric flow rate measurement ___________________________________________________ 24
2.11 Types of flow _____________________________________________________________________ 25
2.12 Friction, heat, pressure drop ________________________________________________________ 27
2.13 Energy and power _________________________________________________________________ 31
2.13.1 Energy __________________________________________________________________________ 31
2.13.2 Power __________________________________________________________________________ 34
2.14 Cavitation _______________________________________________________________________ 37
2.15 Throttle points ___________________________________________________________________ 38
3 Hydraulic fluids __________________________________________________________________ 40
3.1 Functions of hydraulic fluids ________________________________________________________ 40
3.2 Types of hydraulic fluid ____________________________________________________________ 41
3.3 Characteristics and requirements ____________________________________________________ 42
3.4 Viscosity ________________________________________________________________________ 43
4 Components of the power supply section _____________________________________________ 47
4.1 Drive ___________________________________________________________________________ 47
4.2 Pump ___________________________________________________________________________ 48
4.3 Couplings _______________________________________________________________________ 55
4.4 Tanks ___________________________________________________________________________ 55
4.5 Filters ___________________________________________________________________________ 57
4.5.1 Return filter ______________________________________________________________________ 59
Contents
4 © Festo Didactic GmbH & Co. KG 574181
4.5.2 Intake filters _____________________________________________________________________ 59
4.5.3 Pressure filters ___________________________________________________________________ 60
4.5.4 Filter arrangement ________________________________________________________________ 60
4.5.5 Bypass filtering ___________________________________________________________________ 63
4.5.6 Contamination indicators ___________________________________________________________ 63
4.5.7 Determining the differential pressure of a pressure filter _________________________________ 64
4.6 Cooling _________________________________________________________________________ 65
4.7 Heating _________________________________________________________________________ 66
4.8 Hydraulic accumulators ____________________________________________________________ 67
4.8.1 Design and mode of operation _______________________________________________________ 67
4.8.2 Piston accumulators _______________________________________________________________ 69
4.8.3 Diaphragm accumulators ___________________________________________________________ 70
4.8.4 Bladder accumulators _____________________________________________________________ 71
4.8.5 Safety regulations _________________________________________________________________ 72
4.8.6 Safety Equipment _________________________________________________________________ 73
5 Drives __________________________________________________________________________ 74
5.1 Hydraulic cylinders ________________________________________________________________ 74
5.1.1 Single-acting cylinders _____________________________________________________________ 74
5.1.2 Double-acting cylinders ____________________________________________________________ 75
5.1.3 End-position cushioning ____________________________________________________________ 78
5.1.4 Seals ___________________________________________________________________________ 79
5.1.5 Mounting options _________________________________________________________________ 80
5.1.6 Exhaust _________________________________________________________________________ 80
5.1.7 Characteristic data ________________________________________________________________ 80
5.1.8 Resistance to buckling _____________________________________________________________ 82
5.1.9 Selecting a cylinder _______________________________________________________________ 84
5.2 Hydraulic motors _________________________________________________________________ 85
6 Characteristic values and designs of hydraulic valves ___________________________________ 88
6.1 Characteristic values of valves _______________________________________________________ 88
6.2 Actuating force ___________________________________________________________________ 89
6.3 Designs _________________________________________________________________________ 89
6.3.1 Poppet valves ____________________________________________________________________ 90
6.3.2 Slide valves ______________________________________________________________________ 91
6.4 Switching overlap _________________________________________________________________ 92
6.5 Control edges ____________________________________________________________________ 94
7 Pressure regulators _______________________________________________________________ 95
7.1 Pressure-relief valves ______________________________________________________________ 95
7.2 Pressure-reducing valves ___________________________________________________________ 97
Contents
© Festo Didactic GmbH & Co. KG 574181 5
8 Directional control valves _________________________________________________________ 100
8.1 Functions _______________________________________________________________________ 100
8.2 Design _________________________________________________________________________ 100
8.2.1 Directional control valve designs ____________________________________________________ 100
8.2.2 Connection options for directional control valves ______________________________________ 102
8.2.3 Performance data for 4/3-way solenoid valves ________________________________________ 103
8.3 Actuation methods for directional control valves _______________________________________ 103
8.3.1 Manually and mechanically actuated directional control valves ___________________________ 104
8.3.2 Solenoid actuated directional control valves __________________________________________ 105
8.3.3 Power failures and wire breaks with solenoid actuated directional control valves ____________ 105
8.4 2/2-way valves __________________________________________________________________ 106
8.4.1 2/2-way stem actuated valve _______________________________________________________ 106
8.5 3/2-way valves __________________________________________________________________ 107
8.5.1 Directly actuated 3/2-way solenoid valve with spring return ______________________________ 108
8.6 4/2-way valves __________________________________________________________________ 109
8.6.1 Transitional positions _____________________________________________________________ 110
8.6.2 4/2-way hand lever valve with spring return __________________________________________ 110
8.6.3 Directly actuated 4/2-way double solenoid valve with detent _____________________________ 111
8.7 4/3-way valves __________________________________________________________________ 112
8.7.1 4/3-way solenoid valve, spring centred, mid-position closed _____________________________ 113
8.7.2 Influence of the mid-position _______________________________________________________ 115
8.8 Pilot control of a directional control valve _____________________________________________ 116
8.8.1 Piloted 4/3-way solenoid valve _____________________________________________________ 116
8.8.2 Comparison of piloted and directly actuated solenoid valves _____________________________ 118
9 Shut-off valves __________________________________________________________________ 119
9.1 Non-return valve _________________________________________________________________ 119
9.2 Piloted non-return valve ___________________________________________________________ 120
9.3 Piloted double non-return valve ____________________________________________________ 122
10 Flow control valves ______________________________________________________________ 123
10.1 Flow control and orifice valves ______________________________________________________ 123
10.2 One-way flow control valve ________________________________________________________ 126
10.3 Flow control valves _______________________________________________________________ 127
11 Proportional valves ______________________________________________________________ 132
11.1 Design and function of a proportional solenoid ________________________________________ 132
11.1.1 Design of a proportional solenoid ___________________________________________________ 132
11.1.2 Function of a proportional solenoid __________________________________________________ 132
11.1.3 Actuation of pressure, flow control and directional control valves _________________________ 133
11.1.4 Armature position control _________________________________________________________ 134
Contents
6 © Festo Didactic GmbH & Co. KG 574181
11.2 Design and function of proportional pressure regulators ________________________________ 135
11.2.1 Pressure-relief valve ______________________________________________________________ 135
11.2.2 Pressure-reducing valve ___________________________________________________________ 136
11.3 Design and function of proportional flow control valves and directional control valves ________ 137
11.3.1 Proportional flow control valves ____________________________________________________ 137
11.3.2 Directly actuated proportional directional control valve _________________________________ 137
11.3.3 Piloted proportional directional control valve __________________________________________ 138
11.3.4 Advantages and disadvantages of piloted proportional valves ____________________________ 139
11.4 Proportional valve designs _________________________________________________________ 140
12 Accessories _____________________________________________________________________ 141
12.1 Hoses and piping ________________________________________________________________ 141
12.1.1 Hoses __________________________________________________________________________ 142
12.1.2 Piping _________________________________________________________________________ 147
12.2 Connecting plates ________________________________________________________________ 149
12.3 Exhaust valves __________________________________________________________________ 150
12.4 Pressure gauges _________________________________________________________________ 151
12.4.1 Pressure gauge with Bourdon tube measuring unit _____________________________________ 151
12.4.2 Pressure gauge with capsule-type or diaphragm element ________________________________ 152
12.4.3 Piston-type pressure gauge ________________________________________________________ 152
12.5 Pressure sensors ________________________________________________________________ 153
12.6 Volumetric flow meters ___________________________________________________________ 153
12.6.1 Flow meter ______________________________________________________________________ 153
13 Basic principles of electrical engineering ____________________________________________ 155
13.1 Direct current and alternating current ________________________________________________ 155
13.2 Ohm’s law ______________________________________________________________________ 156
13.2.1 Electrical conductors _____________________________________________________________ 156
13.2.2 Electrical resistance ______________________________________________________________ 156
13.2.3 Source voltage __________________________________________________________________ 157
13.3 Electrical power _________________________________________________________________ 157
13.4 The function of a solenoid _________________________________________________________ 158
13.4.1 Structure of a solenoid ____________________________________________________________ 158
13.4.2 Solenoid applications _____________________________________________________________ 158
13.4.3 Inductive resistance with AC voltage _________________________________________________ 159
13.4.4 Inductive resistance with DC voltage _________________________________________________ 159
13.5 Function of an electrical capacitor ___________________________________________________ 159
13.6 Function of a diode _______________________________________________________________ 160
Contents
© Festo Didactic GmbH & Co. KG 574181 7
13.7 Measurements in an electrical circuit ________________________________________________ 161
13.7.1 Definition: measure ______________________________________________________________ 161
13.7.2 Safety instructions _______________________________________________________________ 161
13.7.3 Procedure for performing measurements in the electrical circuit __________________________ 162
13.7.4 Voltage measurement ____________________________________________________________ 162
13.7.5 Current measurement _____________________________________________________________ 163
13.7.6 Resistance measurement __________________________________________________________ 163
13.7.7 Error sources while performing measurements in an electrical circuit ______________________ 164
14 Electrical components ____________________________________________________________ 165
14.1 Power pack _____________________________________________________________________ 165
14.2 Electrical input elements __________________________________________________________ 165
14.2.1 NO contact _____________________________________________________________________ 166
14.2.2 NC contact ______________________________________________________________________ 166
14.2.3 Changeover contact ______________________________________________________________ 166
14.3 Sensors ________________________________________________________________________ 167
14.3.1 Limit switches ___________________________________________________________________ 167
14.3.2 Proximity sensors ________________________________________________________________ 167
14.3.3 Pressure switches ________________________________________________________________ 171
14.4 Relays and contactors ____________________________________________________________ 172
14.4.1 Relays _________________________________________________________________________ 173
14.4.2 Contactors ______________________________________________________________________ 174
14.5 Programmable logic controllers _____________________________________________________ 175
14.5.1 Design and function of a PLC _______________________________________________________ 176
14.6 Overall layout of the signal control section ____________________________________________ 176
14.7 Solenoids ______________________________________________________________________ 177
14.8 Spark arresting for solenoid valves __________________________________________________ 179
15 Workflow descriptions for processing machines and production systems __________________ 180
15.1 Function diagrams _______________________________________________________________ 180
15.1.1 Scope of the function diagram ______________________________________________________ 180
15.1.2 Displacement-step diagrams _______________________________________________________ 181
15.2 Sequence description by means of GRAFCET per EN 60848 _______________________________ 182
15.2.1 The basic principle of a GRAFCET ____________________________________________________ 182
15.2.2 Steps __________________________________________________________________________ 182
15.2.3 Transition condition ______________________________________________________________ 183
15.2.4 Actions _________________________________________________________________________ 184
15.2.5 Sequence selection ______________________________________________________________ 187
15.2.6 Returns and jumps _______________________________________________________________ 188
15.2.7 Structuring of GRAFCETs __________________________________________________________ 188
Contents
8 © Festo Didactic GmbH & Co. KG 574181
16 Design of circuit diagrams _________________________________________________________ 189
16.1 Hydraulic circuit diagrams _________________________________________________________ 189
16.1.1 Arrangement of circuit symbols in the hydraulic circuit diagram ___________________________ 189
16.1.2 Position of cylinders and directional control valves _____________________________________ 191
16.1.3 Identification key for components ___________________________________________________ 191
16.1.4 Technical information _____________________________________________________________ 193
16.2 Electrical circuit diagram __________________________________________________________ 194
16.2.1 Electrical circuit diagram of an electro-hydraulic control system ___________________________ 195
16.2.2 Identification of components _______________________________________________________ 196
16.2.3 Logic element tables for relays and contactors _________________________________________ 197
16.2.4 Actuated contacts and sensors _____________________________________________________ 198
16.3 Terminal connection diagram _______________________________________________________ 198
16.3.1 Structure of a terminal connection diagram ___________________________________________ 201
16.3.2 Wiring for an electro-hydraulic control system _________________________________________ 203
17 Safety measures for electro-hydraulic control systems _________________________________ 204
17.1 Hazards and protective measures ___________________________________________________ 204
17.2 Effects of electric current on the human body __________________________________________ 205
17.2.1 Effects of electric current __________________________________________________________ 205
17.2.2 Electrical resistance of the human body ______________________________________________ 206
17.2.3 Variables influencing the risk of accident _____________________________________________ 207
17.3 Protective measures against accidents with electric current ______________________________ 208
17.3.1 Protection against direct contact ____________________________________________________ 208
17.3.2 Earthing ________________________________________________________________________ 208
17.3.3 Protective extra-low voltage _______________________________________________________ 208
17.4 Control panel and indicators _______________________________________________________ 209
17.4.1 Mains switch ____________________________________________________________________ 209
17.4.2 Emergency stop _________________________________________________________________ 209
17.4.3 Control elements for an electro-hydraulic control systems _______________________________ 210
17.5 Protecting electrical equipment against environment influences __________________________ 212
17.5.1 Identification of the degree of protection _____________________________________________ 213
17.6 Safety principles for electro-hydraulic systems ________________________________________ 214
17.6.1 Layout of an electro-hydraulic system ________________________________________________ 214
17.6.2 Commissioning an electro-hydraulic system ___________________________________________ 215
17.6.3 Repair and maintenance of an electro-hydraulic system _________________________________ 215
Contents
© Festo Didactic GmbH & Co. KG 574181 9
18 Circuit symbols __________________________________________________________________ 216
18.1 Circuit symbols for hydraulic components ____________________________________________ 216
18.1.1 Circuit symbols for hydro pumps and hydraulic motors __________________________________ 216
18.1.2 Circuit symbols for valves __________________________________________________________ 217
18.1.3 Circuit symbols for directional control valves __________________________________________ 217
18.1.4 Circuit symbols for actuation methods _______________________________________________ 219
18.1.5 Circuit symbols for pressure regulators ______________________________________________ 220
18.1.6 Circuit symbols for flow control valves _______________________________________________ 220
18.1.7 Circuit symbols for shut-off valves ___________________________________________________ 221
18.1.8 Circuit symbols for cylinders _______________________________________________________ 221
18.1.9 Circuit symbols for other components ________________________________________________ 222
18.1.10 Measuring devices _______________________________________________________________ 223
18.2 Circuit symbols for electrical components ____________________________________________ 223
18.2.1 Circuit symbols for basic functions __________________________________________________ 223
18.2.2 Circuit symbols for electromechanical drives __________________________________________ 225
18.2.3 Circuit symbols for relays and contactors _____________________________________________ 226
18.2.4 Circuit symbols for sensors ________________________________________________________ 226
Standards _____________________________________________________________________________ 227
Index _________________________________________________________________________________ 228
10 © Festo Didactic GmbH & Co. KG 574181
Preface
Hydraulics is the study of the flow characteristics of fluids. This manual places emphasis on the generation
of forces and motion with the help of fluids. Hydraulic fluid is the transmission medium in the field of
hydraulics.
Hydraulics and electro-hydraulics are successfully used in many areas of industrial automation. For
example, woodworking machines, machine tools, processing systems, presses, plastics processing
machines and conveyor systems are operated all over the world with electro-hydraulic control systems.
Electro-hydraulic control systems are used for many applications in the field of mobile hydraulics as well, for
instance in farm vehicles, road construction vehicles and municipal vehicles.
As an introduction to this subject matter, this manual first of all examines the design and function of the
components which are used to set up hydraulic and electro-hydraulic control systems. The following
chapters describe operating sequences, the layout of circuit diagrams and safety measures.
Changing requirements and technical developments have dramatically altered the appearance of control
systems. The keywords “bus networking” and “proportional hydraulics” are mentioned here to mention just
two examples. Close-knit interaction of fluid engineering with microelectronics, sensor technology and
information technology results in numerous innovations in the field of oil-hydraulic drives and control
systems.
We invite readers of this manual to send us tips, feedback and suggestions for improvement.
Please send your comments and suggestions to [email protected],
or to Festo Didactic GmbH & Co. KG, P.O. Box 10 07 10, D-73707 Esslingen, Germany.
The authors
© Festo Didactic GmbH & Co. KG 574181 11
1 The functions of a hydraulic system
1.1 Hydraulics – what does it mean?
Hydraulic systems are used in modern production facilities and manufacturing equipment.
Hydraulics is understood as the generation of force and motion with the help of hydraulic fluid. The
hydraulic fluid is the energy transmission medium.
The importance of hydraulics in automation technology is a reflection of its diverse range of applications.
Basically, we differentiate between:
Stationary hydraulics
Mobile hydraulics
As opposed to stationary hydraulics, which is permanently installed at a given location, mobile hydraulics
travels on wheels or treads. One of the characteristic features of mobile hydraulics is that the valves are
frequently directly actuated by hand. In contrast, solenoid valves are used primarily for stationary
hydraulics.
Hydraulics are also used in shipbuilding, mining and aviation technology. Aviation hydraulics plays a special
role, because safety is of utmost important in this area. In order to illustrate the various functions which can
be fulfilled by hydraulics, a number of typical applications are included as examples in the following pages.
1.2 Stationary hydraulics
The following fields of application are significant in the area of stationary hydraulics:
• Manufacturing and assembly machines
• Transfer lines
• Hoists and conveyors
• Presses
• Injection moulding machines
• Mill trains
• Lifts
A typical area of application is machine tool manufacturing.
1 The functions of a hydraulic system
12 © Festo Didactic GmbH & Co. KG 574181
Figure 1.1: Lathe, press with overhead tank
Tools and workpieces are hydraulically clamped in modern CNC machine tools. Feed units and spindle drives
may also be designed with hydraulic technology.
1.3 Mobile hydraulics
Fields of application for mobile hydraulics include:
Construction machines
Dump trucks, gripper arms, loading platforms
Hoists and conveyors
Farm machinery
Hydraulics is used for many applications in the field of construction machinery. In the case of the excavator,
for example, travelling motion, as well as all working motion such as lifting, gripping, swivelling etc., is
powered by means of hydraulics.
Working motion which is executed in straight lines is generated by linear drives (cylinders), and rotary
motion is executed by means of rotary drives (motors, semi-rotary drives).
1 The functions of a hydraulic system
© Festo Didactic GmbH & Co. KG 574181 13
Figure 1.2: Mobile hydraulics, excavator
1.4 Attributes of hydraulics
Advantages of hydraulics Disadvantage of hydraulics
Transmission of great forces through the use of small
components, i.e. high power density
Environmental contamination due to oil leaks (fire hazard, danger
of accident)
Accurate positioning Susceptible to contamination
Start-up from standstill under maximum load Danger due to high pressure (cutting jet)
Gentle work and reversing Temperature sensitive (viscosity changes)
Good controllability and adjustability Unfavourable degree of efficiency
Favourable heat dissipation
Uniform, load-independent motion, because fluids are hardly
compressible at all
Table 1.1: Hydraulics – advantages and disadvantages
There are other technologies in addition to hydraulics, by means of which forces, motion and signals can be
generated in the field of control technology:
Mechanical Electrical Pneumatic
1 The functions of a hydraulic system
14 © Festo Didactic GmbH & Co. KG 574181
The fact that each technology has its own preferred range of applications must be taken into consideration.
A comparison of typical data for the three most widely used technologies – electrical, pneumatic and
hydraulic – is provided in Table 1.2.
Electrical Hydraulic Pneumatic
Leakage — Contamination No disadvantages except loss
of energy
Environmental influences Danger of explosion in certain
area, temperature sensitive
Susceptible to temperature
fluctuation, fire hazard in the
event of leakage
Explosion-proof, temperature
sensitive
Energy storage Difficult, only in small
quantities with batteries
Limited, with the help of gases Lightweight
Energy transmission Unlimited, with loss of energy Up to 100 m
flow velocity v = 2 to 6 m/s
Up to 1000 m
flow velocity v = 20 to 40 m/s
Operating speed — v = 0.5 m/s v = 1.5 m/s
Energy costs Minimal High Very high
Linear motion Difficult and expensive, small
forces, speed can only be
controlled at great expense
Easily accomplished with
cylinders, good controllability
of speed, very high forces
Easily accomplished with
cylinders, limited forces, speed
is very load-dependent
Rotary motion Easy and powerful Easy, high torque values, low
rotational speeds
Easy, not very powerful, high
rotational speeds
Positioning accuracy Accuracies of down to
±0.05 mm and better can be
achieved
Depending on how much is
invested, accuracies of down to
±0.05 mm and better can be
achieved
Accuracies of down to ±0.1 mm
are possible without load
reversals
Rigidity Very good values can be
achieved thanks to
intermediate mechanical
elements
Good because oil can hardly be
compressed at all
Poor because air is
compressible
Forces Not overload-proof, poor
degree of efficiency due to
downstream mechanical
elements, very high forces can
be achieved
Overload-proof, very high
forces can be generated with
high system pressures of up to
600 bar
(F < 3000 kN)
Overload-proof, force limited by
compressed air and cylinder
diameter
(F < 30 kN to 6 bar)
Table 1.2: Comparison, electrical – hydraulic – pneumatic