This book provides a clear and concise overview of the basic principles of pneumatics technology, the design of pneumatic systems and the applications of the same for a host of engineering solutions, including industrial control. Designed primarily as an undergraduate textbook for mechanical, production, automobile and mechatronics engineering disciplines, it covers the subject in sufficient detail to be of use to postgraduate students as well as those preparing for competitive examinations.
The book employs numerous examples to bring forth the basic principles underlying the use of pneumatic power; it also provides physical interpretations of mathematical analyses for understanding the solutions of complex problems with ease.
Salient features:
T Jagadeesha is an assistant professor in the Department of Mechanical and Production Engineering at the National Institute of Technology (NIT), Calicut, Kerala. He teaches solid mechanics, mechanics of machinery, dynamics of machinery, design of machine elements, fluid power control, computational methods, industrial automation and robotics and mechatronics.
Preface xv Acknowledgements xvii 1. INTRODUCTION TO PNEUMATICS 1.1 Pneumatics and Its Meaning 1 1.2 History of Pneumatics 2 1.3 Pneumatic Systems 2 1.4 Choice of working Mediums 2 1.5 Advantages of Pneumatics over Hydraulics 4 1.5.1 Differences between hydraulic and pneumatic systems 5 1.6 Characteristics of Pneumatic Systems 5 1.7 Applications of Pneumatics 6 1.8 Properties of Air 7 1.8.1 Composition 7 1.8.2 Free air and standard air 8 1.8.3 Atmospheric pressure, gauge pressure and absolute pressure 8 1.8.4 Variation of pressure with altitude 10 1.8.5 Pressure ranges 10 1.9 Gas Laws 11 1.9.1 Boyle’s law 11 1.9.2 Charles’ law 13 1.9.3 Gay-Lussac’s law 14 1.9.4 General gas equation 15 1.10 Basic Components of Pneumatic Systems 16 1.11 Comparison of Hydraulic and Pneumatic Systems 18 1.12 Comparison of Different Power Systems 19 1.12.1 Electrical power transmission 19 1.12.2 Mechanical power transmission 20 1.12.3 Hydraulic power transmission 20 1.12.4 Pneumatic power transmission 20 Summary 22 Exercises 23 2. PREPARATION OF COMPRESSED AIR 2.1 Air Preparation 27 2.2 Classification of Air Compressors 28 viii Contents 2.2.1 Reciprocating compressors 28 2.2.2 Rotary compressors 34 2.2.3 Dynamic displacement compressors (turbo compressors) 37 2.3 Comparison of Different Compressors 37 2.4 Control of Compressors 38 2.5 Selection and Specification of Compressors 38 2.6 Importance of Secondary Treatment 39 2.7 Aftercooler 39 2.7.1 Functions of compressed air aftercoolers 40 2.7.2 Types of aftercoolers 40 2.8 Drying of Compressed Air 41 2.8.1 Types of air dryers 41 2.8.2 Theory of drying 45 2.9 Storage of Compressed Air 49 2.9.1 Air receivers 49 2.9.2 Sizing of air receivers 51 Summary 55 Exercises 56 3. CONDITIONING AND DISTRIBUTION OF COMPRESSED AIR 3.1 Fluid Conditioners 61 3.1.1 Air filters 62 3.1.2 Air regulator 64 3.1.3 Air lubricator 66 3.1.4 Filter–regulator–lubricator (FRL) unit 67 3.2 Air Distribution System 69 3.3 Guidelines for Component Selection 82 3.4 Guidelines for Compressor Sizing 83 Summary 87 Exercises 88 4. PNEUMATICS ACTUATORS AND AIR MOTORS 4.1 Pneumatic Actuators 92 4.2 Types of Pneumatic Actuators 93 4.2.1 Types of pneumatic cylinders (Linear actuators) 93 4.3 Standard Metric Cylinders 108 4.3.1 Graphic symbols for cylinders 109 4.4 CylinderMountings 110 4.5 Cylinder Force, Velocity and Power 111 4.6 Acceleration and Deceleration of Cylinder Loads 112 4.7 Linear Motion Using Pneumatic Cylinders 114 4.7.1 Vertical cylinder 114 Contents ix 4.7.2 Horizontal cylinder 115 4.7.3 Inclined cylinder 115 4.8 Rotary Actuators 120 4.8.1 Vane type actuators 120 4.8.2 Rack and pinion rotary actuator 122 4.8.3 Helix spine rotary actuator 123 4.9 Air Motors 123 4.9.1 Vane motor 125 4.9.2 Piston motor 126 4.9.3 Diaphragm air motor 127 4.9.4 Turbine motor 128 4.9.5 Gear motor 128 Summary 129 Exercises 130 5. PNEUMATIC CONTROL VALVES 5.1 Valves 134 5.2 Direction Control Valves 135 5.2.1 Types of direction control valves 135 5.2.2 Non-return valves 158 5.2.3 Flow control valves 163 5.2.4 Pressure control valves 164 5.3 Valve Specification 167 5.4 Valve Sizing 167 5.4.1 Valve sizing of flow control valves 167 5.4.2 Sizing of direction control valves 173 Summary 177 Exercises 178 6. SINGLE ACTUATOR CIRCUITS 6.1 Pneumatic Circuits and Pneumatic Circuit Diagrams 181 6.2 Single Acting Cylinder Control 182 6.2.1 Direct control of a single acting cylinder 182 6.2.2 Indirect control of single acting cylinder 183 6.2.3 Control of a single acting cylinder using an ”OR” valve 185 6.2.4 Control of single acting cylinder using an ”AND” valve 186 6.2.5 Control of a single acting cylinder using a ”NOT” valve 186 6.3 Direct Control of a Double Acting Cylinder 187 6.3.1 Indirect control of double acting cylinder using a memory valve 189 6.4 Supply and Exhaust Air Throttling 189 6.4.1 Supply air throttling 190 6.4.2 Exhaust air throttling 190 6.5 Methods of Checking the End Position of a Cylinder 191 x Contents 6.5.1 Use of limit switches 191 6.6 Pressure Dependent Controls 199 6.7 Time Dependent Controls 201 Summary 210 Exercises 211 7. MULTI ACTUATOR CIRCUITS – PART I 7.1 Single Actuator vs Multi Actuator Circuits 218 7.2 Classic or IntuitiveMethod 219 7.2.1 Coordinated and sequential motion control 219 7.2.2 Demonstration of the classic method 219 7.2.3 Elimination of signal conflict 231 7.3 Cascade Method 234 7.3.1 Demonstration of the cascade method 234 7.4 Step Counter Method 245 Summary 286 Exercises 286 8. MULTI ACTUATOR CIRCUITS – PART II 8.1 Pneumatic Logic Control 292 8.2 Signal Processing Logic Gates 293 8.2.1 OR Gate 294 8.2.2 AND Gate 295 8.2.3 NOT (Inverter) Gate 295 8.2.4 NAND Gate 296 8.2.5 NOR Gate 297 8.2.6 XOR Gate (Exclusive OR) 298 8.2.7 XNOR (Exclusive NOR) Gate 299 8.2.8 NAND and NOR Universality 299 8.3 Boolean Algebra 300 8.3.1 Boolean algebra equalities or Identities 301 8.3.2 DeMorgan’s Theorem 303 8.3.3 Sum of Products (SOP) 309 8.3.4 Product of Sums (POS) 311 8.3.5 Analysis Using SOP and POS and Truth Table 312 8.4 General Analysis of Karnaugh–VeitchMaps 315 8.4.1 Condition of Adjacency 315 8.4.2 Logic Circuit Design with Karnaugh–Veitch Mapping Method 321 8.5 Compound Circuit Design 338 8.6 Combinational Circuit Design 341 Summary 344 Exercises 345 Contents xi 9. ELECTRO-PNEUMATIC CONTROL 9.1 Introduction 351 9.2 Control Electrical Devices 352 9.2.1 Push button switches 352 9.2.2 Limit switches 354 9.2.3 Pressure switches 355 9.2.4 Solenoids 356 9.2.5 Relays 358 9.2.6 Time delay relays (Timers) 359 9.2.7 Temperature switch 360 9.2.8 Reed proximity switches 360 9.2.9 Electronic sensors 362 9.2.10 Electric counters 367 9.3 Electro-pneumatics Circuits for Single Actuators 368 9.3.1 Direct control of single acting cylinder 368 9.3.2 Indirect control of a single acting cylinder 369 9.3.3 Direct control of a double acting cylinder 369 9.3.4 Indirect control of a double acting cylinder (5/2 valve, single solenoid) 370 9.3.5 Indirect control of a double acting cylinder (5/2 valve, double solenoid) 371 9.3.6 Control of a double acting cylinder, OR logic (Parallel circuit) 372 9.3.7 Control of a double acting cylinder, AND logic 373 9.3.8 Latching circuits 373 9.3.9 Double acting cylinder with automatic return (Spring return) 376 9.3.10 Direct control of a double acting cylinder with automatic return (double solenoid) 377 9.3.11 Indirect control of a double acting cylinder with automatic return (double solenoid) 377 9.3.12 Automatic return of a double acting cylinder (using proximity switch) 378 9.3.13 Oscillating motion of a double acting cylinder (Forward) 378 9.3.14 Oscillating motion of a double acting cylinder (Return) 379 9.3.15 Control systems with timed response 379 9.3.16 Control of a double acting cylinder using an electric counter with two end sensors 381 9.3.17 Oscillation of a double acting cylinder using proximity switches 383 9.3.18 Control of a double acting cylinder using a pressure switch 383 9.3.19 Control of a double acting cylinder using a delay on and off timer and counter 384 9.3.20 Control of a double acting cylinder using a reed switch for initial sensing 385 9.4 Electro-pneumatic Circuits for Multi Actuators 391 9.4.1 Two-group electro-pneumatic circuits 391 xii Contents 9.4.2 Design of three group electro-pneumatic circuits 400 Summary 404 Exercises 405 10. PNEUMATIC CIRCUIT DESIGN USING PLCs 10.1 Introduction 423 10.2 Features of Programmable Logic Controllers 424 10.3 Hardwired Control System 424 10.4 PLC Systems 425 10.5 Major Components of PLC 426 10.6 Programming of PLC 427 10.7 PLC Timers 431 10.8 PLC Counters 432 10.9 PLC Memory Elements 433 10.10 Logic Design and PLC Circuits 449 10.11 Areas of Application of a PLC 449 10.12 PLC Standards 450 Summary 451 Exercises 451 11. INTRODUCTION TO FLUIDICS 11.1 Fluidics Defined 455 11.2 Historical Background 456 11.3 Advantages and Disadvantages of Fluidics 456 11.4 Coanda or Wall Attachment Effect 457 11.5 Basic Fluidic Devices 458 11.6 Schmitt Trigger 464 11.7 Turbulence Amplifier 464 11.8 Fluid Sensors 465 11.8.1 Types of fluid sensors 465 11.9 Application Examples 468 11.9.1 Control of a double acting cylinder 468 11.9.2 Control of two double acting cylinders in sequence 469 11.9.3 Continuous automatic reciprocation of a hydraulic cylinder 470 Summary 471 Exercises 472 12. HYDROPNEUMATICS 12.1 Introduction 474 12.2 Hydropneumatic Circuits 475 12.2.1 Air-oil reservoir 475 12.2.2 Hydraulic check units 477 12.2.3 Air-oil intensifier 478 Contents xiii 12.3 Comparison of Hydropneumatic, Hydraulic and Pneumatic Circuits 482 Summary 483 Exercises 484 13. MAINTENANCE AND TROUBLESHOOTING OF PNEUMATIC SYSTEMS 13.1 Maintenance of Pneumatic Systems 485 13.2 General Maintenance Procedure 487 13.3 General Maintenance Guide 487 13.4 General Troubleshooting Guide 493 13.5 General Troubleshooting Procedure 493 Summary 508 Exercises 509 Index 511