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Textbook Festo Didactic 574181 en Hydraulics Electrohydraulics Fundamentals T B P A B A T P M1 M2

Festo worldwide Hydraulics Electrohydraulics · Hydraulics Electrohydraulics Fundamentals ... Janki k/Warszawy ul. Mszczonowska 7 ... St. Constantin 17 010217 Bucuresti

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Page 1: Festo worldwide Hydraulics Electrohydraulics · Hydraulics Electrohydraulics Fundamentals ... Janki k/Warszawy ul. Mszczonowska 7 ... St. Constantin 17 010217 Bucuresti

Textbook

Festo Didactic

574181 en

HydraulicsElectrohydraulicsFundamentals

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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]

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CanadaFesto Inc.5300 Explorer DriveMississauga, Ontario L4W 5G4Tel. +1 (0)905 624 90 00,Fax +1 (0)905 624 90 01E-mail: [email protected]

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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]

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DenmarkFesto A/SIslevdalvej 1802610 RødovreTel. +45 70 21 10 90, Fax +45 44 88 81 10E-mail: [email protected]

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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]

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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]

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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]

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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

Page 2: Festo worldwide Hydraulics Electrohydraulics · Hydraulics Electrohydraulics Fundamentals ... Janki k/Warszawy ul. Mszczonowska 7 ... St. Constantin 17 010217 Bucuresti

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.

Page 3: Festo worldwide Hydraulics Electrohydraulics · Hydraulics Electrohydraulics Fundamentals ... Janki k/Warszawy ul. Mszczonowska 7 ... St. Constantin 17 010217 Bucuresti

© 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

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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

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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

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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

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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

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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

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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

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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

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© 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.

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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).

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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

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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