Basic Principles of Pneumatics and Electro-Pneumatics

213 Pages·2009·26.746 MB·English

by  Frank Ebel, Siegfried Idler, Georg Prede, Dieter Scholz

Pneumatics
Electropneumatics
Fundamentals
FESTO
Textbook
Festo Didactic
573030 EN
Order No.: 573030
Edition: 12/2009
Authors: Frank Ebel, Siegfried Idler, Georg Prede, Dieter Scholz
Graphics: Doris Schwarzenberger
Layout: 05.11.2010, Frank Ebel
© Festo Didactic GmbH & Co. KG, 73770 Denkendorf, Germany, 2010
Internet: www.festo-didactic.com
E-mail: [email protected]
The copying, distribution and utilization of this document as well as the communication of its contents to
others without expressed authorization is prohibited. Offenders will be held liable for the payment of
damages. All rights reserved, in particular the right to carry out patent, utility model or ornamental design
registration.
Contents
Foreword _____________________________________________________________________________ 11
1 Applications in automation technology _______________________________________________ 13
1.1 Overview ________________________________________________________________________ 13
1.2 Characteristics of pneumatics _______________________________________________________ 14
1.2.1 Criteria for working media __________________________________________________________ 15
1.2.2 Criteria for control media ___________________________________________________________ 15
1.3 Development of pneumatic control systems ____________________________________________ 16
2 Basic concepts of pneumatics _______________________________________________________ 17
2.1 Physical principles ________________________________________________________________ 17
2.1.1 Newton's law ____________________________________________________________________ 17
2.1.2 Pressure ________________________________________________________________________ 18
2.2 Properties of air __________________________________________________________________ 19
2.2.1 Boyle's law ______________________________________________________________________ 19
2.2.2 Gay-Lussac's law _________________________________________________________________20
2.2.3 General gas equation ______________________________________________________________ 21
3 Compressed air generation and compressed air supply__________________________________ 22
3.1 Preparing the compressed air _______________________________________________________ 22
3.1.1 Consequences of poorly prepared compressed air ______________________________________ 22
3.1.2 Pressure level ____________________________________________________________________ 23
3.2 Compressors _____________________________________________________________________ 23
3.2.1 Reciprocating piston compressor ____________________________________________________ 23
3.2.2 Diaphragm compressor ____________________________________________________________ 24
3.2.3 Rotary piston compressor __________________________________________________________ 24
3.2.4 Screw compressor ________________________________________________________________ 25
3.2.5 Flow compressor__________________________________________________________________ 25
3.2.6 Regulation _______________________________________________________________________ 25
3.2.7 Duty cycle _______________________________________________________________________ 26
3.3 Air reservoirs _____________________________________________________________________ 27
3.4 Air dryers ________________________________________________________________________ 29
3.4.1 Refrigeration dryer ________________________________________________________________ 30
3.4.2 Adsorption dryer __________________________________________________________________ 30
3.4.3 Absorption dryer __________________________________________________________________ 31
3.5 Air distribution ___________________________________________________________________ 34
3.5.1 Sizing of the piping ________________________________________________________________ 34
3.5.2 Flow resistance ___________________________________________________________________ 34
3.5.3 Pipe material _____________________________________________________________________ 35
3.5.4 Pipe layout ______________________________________________________________________ 36
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Contents
3.6 Service unit ______________________________________________________________________ 37
3.6.1 Compressed air filter ______________________________________________________________ 37
3.6.2 Pressure regulator _________________________________________________________________ 39
3.6.3 Lubricator ________________________________________________________________________ 41
3.6.4 Service unit combinations __________________________________________________________ 43
4 Drives and output devices ___________________________________________________________ 45
4.1 Single-acting cylinders _____________________________________________________________ 45
4.1.1 Design ___________________________________________________________________________ 46
4.1.2 Fluidic muscle _____________________________________________________________________ 46
4.2 Double-acting cylinders ____________________________________________________________ 48
4.2.1 Cylinder with end-position cushioning ________________________________________________ 48
4.2.2 Tandem cylinder __________________________________________________________________ 49
4.2.3 Cylinder with through piston rod _____________________________________________________ 50
4.2.4 Multi-position cylinder _____________________________________________________________ 50
4.2.5 Rotary cylinder ____________________________________________________________________ 51
4.2.6 Semi-rotary drive _________________________________________________________________ 51
4.3 Rodless cylinders _________________________________________________________________ 52
4.3.1 Band cylinder _____________________________________________________________________ 52
4.3.2 Sealing band cylinder ______________________________________________________________ 52
4.3.3 Cylinder with magnetic coupling _____________________________________________________ 53
4.4 Handling technology_______________________________________________________________ 53
4.4.1 Swivel/linear drive unit ____________________________________________________________ 54
4.4.2 Pneumatic grippers_________________________________________________________________ 54
4.4.3 Suction cups _____________________________________________________________________ 56
4.4.4 Vacuum generators _______________________________________________________________ 56
4.5 Cylinder properties ________________________________________________________________ 58
4.5.1 Piston force _______________________________________________________________________ 58
4.5.2 Stroke length ____________________________________________________________________ 59
4.5.3 Piston speed ______________________________________________________________________ 60
4.5.4 Air consumption __________________________________________________________________ 60
4.6 Motors ___________________________________________________________________________ 62
4.6.1 Piston motors _____________________________________________________________________ 63
4.6.2 Vane motors _____________________________________________________________________ 63
4.6.3 Geared motors ___________________________________________________________________ 64
4.6.4 Turbine motors (flow motors) _______________________________________________________ 64
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Contents
5 Directional control valves __________________________________________________________ 65
5.1 Applications _____________________________________________________________________ 65
5.1.1 Solenoid valves___________________________________________________________________ 65
5.1.2 Actuating a single-acting cylinder ____________________________________________________ 65
5.1.3 Actuating a double-acting cylinder ___________________________________________________ 66
5.2 Design __________________________________________________________________________ 67
5.2.1 Poppet valves ____________________________________________________________________ 68
5.2.2 Slide valves ______________________________________________________________________ 68
5.2.3 Pneumatic performance data ________________________________________________________ 69
5.2.4 Actuation methods for directional control valves ________________________________________ 71
5.3 2/2-way valves ___________________________________________________________________ 72
5.4 3/2-way valves ___________________________________________________________________ 72
5.4.1 3/2-way hand slide valve ___________________________________________________________ 72
5.4.2 3/2-way stem actuated valve________________________________________________________ 73
5.4.3 3/2-way pneumatic valve ___________________________________________________________ 74
5.4.4 3/2-way solenoid valve ____________________________________________________________ 76
5.5 Piloted directional control valves 78
5.5.1 How the pilot control stage works with manually and mechanically actuated
directional control valves 78
5.5.2 Piloted 3/2-way roller lever valve ____________________________________________________ 78
5.5.3 How the pilot control stage works with solenoid actuated directional control valves ___________ 80
5.5.4 Piloted 3/2-way solenoid valve ______________________________________________________ 81
5.5.5 Comparison of piloted and directly actuated valves______________________________________ 82
5.6 5/2-way valves ___________________________________________________________________ 82
5.6.1 5/2-way pneumatic valve ___________________________________________________________ 82
5.6.2 5/2-way double pilot valve _________________________________________________________ 83
5.6.3 Piloted 5/2-way solenoid valve ______________________________________________________ 85
5.6.4 Piloted 5/2-way double solenoid valve ________________________________________________ 86
5.7 5/3-way valves ___________________________________________________________________ 87
5.7.1 5/3-way pneumatic valves __________________________________________________________ 87
5.7.2 Piloted 5/3-way solenoid valve with mid-position closed _________________________________ 88
5.7.3 Influence of the mid-position ________________________________________________________ 90
5.8 Flow rates of valves _______________________________________________________________ 91
5.9 Reliable operation of valves _________________________________________________________ 92
5.9.1 Assembling roller lever valves _______________________________________________________ 92
5.9.2 Installing the valves _______________________________________________________________ 92
6 Shut-off valves, flow control valves and pressure regulators, valve combinations ____________ 93
6.1 Shut-off valves ___________________________________________________________________ 93
6.1.1 Non-return valves _________________________________________________________________ 93
6.1.2 Processing elements_______________________________________________________________ 93
6.1.3 Dual-pressure valve: logic AND function _______________________________________________ 94
6.1.4 Shuttle valve: logic OR function______________________________________________________ 94
6.1.5 Quick exhaust valve _______________________________________________________________ 95
6.1.6 On-off valves _____________________________________________________________________ 96
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6.2 Flow valves ______________________________________________________________________ 96
6.2.1 Flow control valvess _______________________________________________________________ 96
6.2.2 One-way flow control valves ________________________________________________________ 97
6.2.3 Supply air flow control _____________________________________________________________ 98
6.2.4 Exhaust air flow control ____________________________________________________________ 98
6.2.5 Application of the flow control method ________________________________________________ 98
6.3 Pressure regulators ______________________________________________________________ 100
6.3.1 Pressure regulator _______________________________________________________________ 100
6.3.2 Pressure-relief valve ______________________________________________________________100
6.3.3 Pressure sequence valve __________________________________________________________ 101
6.4 Valve combinations ______________________________________________________________ 101
6.4.1 Time delay valves ________________________________________________________________ 102
7 Valve terminal technology ________________________________________________________ 104
7.1 Measures for optimising individual valves ____________________________________________ 104
7.2 Advantages of optimised individual valves ____________________________________________ 104
7.3 Optimised valves for manifold assembly 105
7.4 Electrical connection of valve manifolds ______________________________________________ 106
7.5 Modern installation concepts 107
7.5.1 Advantages of modern installation concepts __________________________________________ 107
7.5.2 Control components for reduced installation complexity_________________________________ 107
7.5.3 Valve/sensor terminal 108
7.5.4 Wiring with multi-pin plug connection 108
7.5.5 Structure of a fieldbus system 109
7.5.6 Mode of operation of a fieldbus system ______________________________________________ 110
7.5.7 Fieldbus types 110
8 Proportional pneumatics 111
8.1 Proportional pressure regulators 111
8.1.1 Function of a proportional pressure regulator _________________________________________ 111
8.1.2 Application for a proportional pressure regulator 112
8.1.3 Controlling the test device _________________________________________________________ 112
8.1.4 Equivalent circuit diagram for a proportional pressure regulator 113
8.1.5 How a proportional pressure regulator works 113
8.2 Proportional directional control valves _______________________________________________ 114
8.2.1 Functions of a proportional directional control valve ____________________________________ 114
8.2.2 Application for a proportional directional control valve __________________________________ 115
8.2.3 Equivalent circuit diagram for a proportional directional control valve 115
8.2.4 Flow rate signal function of a proportional directional control valve 116
8.3 Pneumatic positioning drive 117
8.3.1 Application for a pneumatic positioning drive 117
8.3.2 Structure of a pneumatic positioning drive ____________________________________________ 117
6 © Festo Didactic GmbH & Co. KG 573030
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9 Basic principles of electrical engineering ____________________________________________ 118
9.1 Direct current and alternating current 118
9.2 Ohm's law ______________________________________________________________________ 119
9.2.1 Electrical conductor ______________________________________________________________ 119
9.2.2 Electrical resistance ______________________________________________________________ 120
9.2.3 Source voltage __________________________________________________________________ 120
9.3 Electrical power _________________________________________________________________ 120
9.4 How a solenoid works ____________________________________________________________ 121
9.4.1 Structure of a solenoid ____________________________________________________________122
9.4.2 Applications of solenoids __________________________________________________________ 122
9.4.3 Inductive resistance with AC voltage 122
9.4.4 Inductive resistance with DC voltage_________________________________________________ 123
9.5 How an electrical capacitor works ___________________________________________________ 123
9.6 How a diode works _______________________________________________________________ 124
9.7 Measurements in an electrical circuit ________________________________________________ 125
9.7.1 Definition: Measuring _____________________________________________________________ 125
9.7.2 Safety measures _________________________________________________________________ 126
9.7.3 Procedure for measurements in an electrical circuit_____________________________________ 126
9.7.4 Voltage measurement ____________________________________________________________ 126
9.7.5 Current measurement_____________________________________________________________ 127
9.7.6 Resistance measurement __________________________________________________________ 127
9.7.7 Error sources when taking measurements in an electrical circuit 128
10 Components and modules in the electrical signal control section ________________________ 130
10.1 Power supply unit 130
10.2 Pushbuttons and control switches 131
10.2.1 Normally open contacts 131
10.2.2 Normally closed contacts __________________________________________________________132
10.2.3 Changeover switches _____________________________________________________________ 132
10.3 Sensors for position and pressure sensing ____________________________________________ 133
10.3.1 Limit switches ___________________________________________________________________ 133
10.3.2 Proximity sensors ________________________________________________________________ 134
10.4 Relays and contactors ____________________________________________________________ 140
10.4.1 Structure of a relay _______________________________________________________________ 140
10.4.2 Applications of relays _____________________________________________________________ 141
10.4.3 Remanence relays________________________________________________________________ 142
10.4.4 Time delay relays ________________________________________________________________ 142
10.5 Structure of a contactor ___________________________________________________________ 143
10.6 Miniature controllers _____________________________________________________________ 145
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Contents
11 Operating sequence descriptions ___________________________________________________ 149
11.1 Function charts for processing machines and production systems _________________________ 149
11.1.1 Scope of validity of the function chart ________________________________________________ 149
11.1.2 Displacement-step diagram ________________________________________________________ 150
11.2 Sequence description by means of GRAFCET to EN 60848________________________________151
11.2.1 The basic principle of a GRAFCET ____________________________________________________ 152
11.2.2 Steps __________________________________________________________________________ 152
11.2.3 Transition condition ______________________________________________________________ 153
11.2.4 Actions_________________________________________________________________________ 154
11.2.5 Sequence selection ______________________________________________________________ 158
11.2.6 Returns and jumps _______________________________________________________________ 159
11.2.7 Structuring of GRAFCETs __________________________________________________________159
11.2.8 Example of a slot cutting device ____________________________________________________ 160
12 Structure of circuit diagrams _______________________________________________________ 162
12.1 Pneumatic circuit diagram 162
12.1.1 Position of the symbols in the pneumatic circuit diagram 162
12.1.2 Position of cylinders and directional control valves 162
12.1.3 Identification key for components ___________________________________________________ 163
12.2 Electrical circuit diagram 166
12.2.1 Block diagram ___________________________________________________________________ 166
12.2.2 Operational circuit diagram ________________________________________________________ 166
12.2.3 Schematic diagram _______________________________________________________________ 166
12.2.4 Schematic diagram for an electropneumatic control system 167
12.3 Terminal connection diagram_______________________________________________________ 172
12.3.1 Requirements for the wiring________________________________________________________ 172
12.3.2 Wiring via terminal strips __________________________________________________________ 172
12.3.3 Structure of terminals and terminal strips ____________________________________________ 174
12.3.4 Terminal assignment _____________________________________________________________ 174
12.3.5 Structure of a terminal connection diagram ___________________________________________ 175
12.3.6 Creating a terminal connection diagram ______________________________________________ 175
13 Safety measures with electropneumatic control systems _______________________________ 180
13.1 Hazards and protective measures 180
13.2 Effect of electric current on the human body 181
13.2.1 Effect of electric current 181
13.2.2 Electrical resistance of the human body ______________________________________________ 182
13.2.3 Variables influencing the risk of accident _____________________________________________ 183
13.3 Protective measures against accidents with electric current ______________________________ 184
13.3.1 Protection against direct contact ____________________________________________________ 184
13.3.2 Earthing ________________________________________________________________________ 184
13.3.3 Protective extra-low voltage _______________________________________________________ 185
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Contents
13.4 Control panel and indicators _______________________________________________________ 185
13.4.1 Main switch _____________________________________________________________________ 185
13.4.2 EMERGENCY STOP _______________________________________________________________ 186
13.4.3 Control elements of an electropneumatic control system ________________________________ 186
13.5 Protecting electrical equipment against environment influences _________________________ 189
13.5.1 Identification of the degree of protection ____________________________________________ 190
14 Symbols and circuit symbols _____________________________________________________ 192
14.1 Symbols for pneumatic components ________________________________________________ 192
14.1.1 Symbols for the power supply section ______________________________________________ 192
14.1.2 Symbols for valves _______________________________________________________________ 194
14.1.3 Symbols for directional control valves ______________________________________________ 194
14.1.4 Symbols for non-return valves, flow control valves and quick exhaust valves _______________ 197
14.1.5 Symbols for pressure regulators ___________________________________________________ 198
14.1.6 Symbols for operating elements ___________________________________________________ 199
14.1.7 Symbols for other components 201
14.2 Circuit symbols for electrical components ___________________________________________ 202
14.2.1 Circuit symbols for basic functions __________________________________________________ 202
14.2.2 Circuit symbols for electromechanical drives _________________________________________ 204
14.2.3 Circuit symbols for relays and contactors ____________________________________________ 205
14.2.4 Circuit symbols for sensors ________________________________________________________206
Standards ____________________________________________________________________________ 207
Index ____________________________________________________________________________ 208
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Contents
10 © Festo Didactic GmbH & Co. KG 573030