FLUID POWERGeneration, Transmission and Control FLUID POWERGeneration, Transmission and Control

FLUID POWERGeneration, Transmission and Control

Jagadeesha T.Assistant ProfessorDepartment of Mechanical and Production EngineeringNational Institute of Technology, Calicut, Kerala

Dr. Thammaiah GowdaProfessor and HeadDepartment of Mechanical and Industrial Production EngineeringAdichunchanagiri Institute of Technology, Chickmagalur, Karnataka

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FLUID POWER : Generation, Transmission and Control

Jagadeesha T.

Jagadeesha T. is currently working as an Assistant Professor in the Department of Mechanical and Production Engineering at National Institute of Technology (NIT), Calicut (Kerala). He earned his BE (Mechanical) degree from NIT, Surathkal ( Karnataka); ME (Machine Tools) degree from PSG college of Technology; Master of Science (Manufacturing and Automation) from National University of Singapore; and Master of Science (AMNS) from Singapore MIT alliance. He is the recipient of the prestigious JRD Tata Scholarship and SMA (Government of Singapore) Scholarship. He has 20 years of experience in the industry, teaching, academic research, consultation, and has excellently completed many projects with reputed organizations. He has worked with TATA Engineering Locomotive Company (India), TVS Suzuki (India), IBM Pvt. Ltd (Singapore), ASM (Singapore), and Applied Materials (Singapore and United States), APP Systems and Services (Singapore), ST Microelectronics (Singapore), Chartered Semiconductor Manufacturing (Singapore), and Sitronics (Singapore). He has developed workbooks on Fluid Power Control, Mechanical Vibration, Machine Design, Machining Science, and IC Engines. He is the co-author of the textbook Mechanical Vibration. He is a member of several professional bodies in India and abroad. He is a Certified Professional Engineer (Australia). His innovative research on BPSG CVD process won the best IFIT award at ST Microelectronics, Singapore. He has bagged more than 30 quality suggestion awards at TELCO and Best Employee award three times at ST Microelectronics, Singapore. He teaches Solid Mechanics, Mechanics of Machinery, Dynamics of Machinery, Design of Machine Elements, Fluid Power and Control at NIT Calicut.

Dr. Thammaiah Gowda

Dr. Thammaiah Gowda is presently working as a Professor and Head in the Department of Mechanical and Industrial Production Engineering at Adichunchanagiri Institute of Technology, Chikmagalur (Karnataka). Dr. Gowda obtained his BE (Mechanical) degree from SJCE (University of Mysore), ME (Machine Design) degree from UVCE (Bangalore University), and PhD from UBDT College of Engineering (Kuvempu University). He has more than 40 years of teaching experience. He teaches Mechanical Vibration, FEM, Tribology and Bearing design, Mechanics of Materials, Design of Machine Elements, Kinematics of Machines, Dynamics of Machinery, Automatic Control Engineering, CAD/CAM, Theory of Elasticity and Plasticity at AIT. He has published several research papers in international, national journals and conferences. Dr. Gowda has co-authored the textbook Mechanical Vibration. He has guided seven PhD and MSc students.

About the Authors

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We have written this book for students and engineers in mechanical, production, automobile, and mechatronics engineering who wish to understand fluid power science and apply it in solving the engineering problems. This book is primarily designed for the use of graduate and postgraduate students, as well as students who are preparing for AMIE and various other competitive examinations. For the practicing engineers, it is hoped that this book will be a very useful reference of collected information that will assist in the solution of many problems encountered in the application of fluid power in the industry.

We have endeavored to present the subject in a simple and rational way. In preparation of this book, we have taken advantage of the vast experience gained in the course of our work during the last 30 years. It has been our aim to show the basic principles underlying fluid power by means of providing typical examples. Empirical formulae have been used only when it is not practi-cal to use mathematical analysis. It has been our experience that a sound knowledge of mechanics of fluid is very essential to take up the study of Fluid Power Control and Design. It is expected that the students using this book have completed a course in applied mathematics.

The main objective of writing this book has been to give a clear understanding of the concepts underlying fluid power con-trol. We have strived to teach the subject on a scientific basis, to maintain the physical perceptions in the various derivations and to give the short comprehending solution to a variety of complex problems. The parameters kept in mind while writing the book are coverage of contents to suit syllabi of various Indian Universities, prerequisite knowledge of the user of this book, lucidity of writing, clarity of thoughts and variety of solved and unsolved numerical problems, including problems from competitive examinations.

Despite the importance and relevance of the subject, it is observed that the subject has not been given its justified importance in the undergraduate engineering course curriculum of Indian Technical Institutes. In most cases, the subject has been taught as an elective course. In almost all cases, the subject has been set aside for advanced reading in the postgraduate section. We feel that the subject should be a separate one in the undergraduate level, where fundamentals of physics of fluid power control should be taught with great care and with sufficient mathematical exposure.

Organization of the Book

The 21 self-contained chapters in this book have been systematically organized as follows:

Chapter 1:1. This chapter gives a brief introduction to the fluid power industry and then develops the basic concepts for power delivery with fluids. Elementary hydraulic and pneumatic circuit components have been presented along with their advantages and disadvantages.Chapter 2:2. This chapter contains an outline of corpuscular aspects of fluid mechanics and some practical applications.Chapter 3:3. This chapter introduces us to properties and functions of hydraulic fluids normally used in the industry. The primary aspect of this chapter is the determination of properties of fluid. Now the industry has begun to consider the use of less mineral oil content as both supply and environmental issues have started dominating many new applications.Chapter 4:4. This chapter discusses the various governing laws used in fluid power. Students should focus on chapters 2, 3 and 4, as the success of future study depends on these chapters.Chapter 5:5. This chapter deals with various fittings used in fluid power systems. The guidelines to select pipes, hoses and tubings have been discussed in this chapter.Chapter 6:6. In this chapter, various energy losses have been discussed in great detail. It also contains design problems containing all kinds of losses.Chapter 7:7. This chapter discusses the various pumps used in fluid power industries.Chapters 8 and 9:8. These two chapters complement Chapter 7 and are all about the interaction between hydraulic actuators and hydraulic motors.Chapter10:9. This chapter introduces hyrdostatic transmission systems.Chapter 11 to Chapter 13:10. These chapters introduce various control valves to control direction, pressure and flow.Chapter 14:11. This chapter describes the various circuits and control methods and also the various methods of controlling hydraulic actuators.

Preface

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viii Fluid Power: Generation, Transmission and Control

Chapter 15:12. This chapter involves a more detailed mathematical treatment of a wider range of flow control valves.Chapter 16: 13. This chapter presents the linear analysis of the hydraulic systems and servo mechanism.Chapters 17 and 18:14. These chapters deal with proportional control valves and servo valves. In both the chapters, the mechanical aspects of valves, the valve actuation mechanisms and valve performance have been discussed.Chapter 19:15. This chapter is concerned with the storing of fluid energy using accumulators.Chapter 20:16. Characteristics of auxiliary components used in fluid power have been covered in this chapter.Chapter 21: 17. This chapter deals with the maintenance of fluid power systems.

Apart from all these, each chapter contains Multiple-Choice Questions, Review Questions, Exercises, Solved Examples, and Frequently Asked Questions of various Indian universities’ examinations (Short-Answer Type). Presentation of the subject in SI units and simple language makes the book useful for effective teaching and application.

Salient Features of the Book

1. Presentation of basic theory in simple and readily understandable form.2. A balanced presentation of mathematical and concept approaches.3. Large number of solved problems and unsolved problems picked up from various Indian technical institutes and

universities.4. Each chapter has a concise and comprehensive treatment of topics with strong emphasis on fundamental concepts. A

number of theoretical questions and unsolved exercises have been given for practice so as to widen the horizon of com-prehension of the topic.

Guidelines for Instructors

This book has been written as textbook for one-semester course in fluid power. It is expected that the course will be taught to undergraduate and graduate students. In most engineering curricula, fluid power control is an elective course. Students inter-ested in machine design, mechatronics, automobile, manufacturing and production engineering make room in their course of study.

We have found that 10 problems in 1 week is an ample assignment. Certain problems can be assigned to the students as the take-home assignment to solve them using MATLAB.

This book is supplemented with solution manual for each chapter. Solution manual contains answers for Review questions and detailed solutions to Exercise problems given at the end of each chapter. This is available on request for instructors. Kindly mail to acadmktg@wiley.com

Guidelines for Students

Mathematics is intimately concerned with the study of Fluid Power. In order to study the characteristics of fluid power sys-tems, students have to resort to understanding the physical meaning and modeling of the system and write the characteristic equations. To solve the fluid power problems by MATLAB, knowledge of matrix algebra is essential. Good knowledge of fluid mechanics is also very much essential to derive full benefit from this textbook.

Although every care has been taken in correcting proofs and checking numerical examples, errors may be present and further suggestions to improve upon remain. We will be highly grateful to the readers for any feedback. Please send your feedback to Jagdishsg@nitc.ac.in

Jagadeesha T. Thammaiah Gowda

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This book took almost a decade in its making. During that period, a multitude of friends, clients, and associates have provided us with support, helped us solidify our ideas regarding the fluid power control theory. We remain ever grateful to all of them. We wish to place on record our deep sense of gratitude to our teachers, our parents and our families for encouraging us to pursue an academic career.

Jagadeesha T. would specifically like to thank his wonderful wife Vasanthi and his son Ramkumar for their love, patience and endless sacrifices. He would also like to thank his sister Prabhavathi T., without whose presence, encouragement and com-fort, this textbook would have remained merely a good intention. Acknowledgements are due to several of his close associ-ates and team leaders in India and abroad. These include: Ashok Kumar, Head (Operations), Yogesh Kale, Head (Design) of Harith Grammer (TVS-Suzuki Group), Hosur; Louis Kim, Head (Thin films), Chartered Semiconductor Manufacturing Ltd., Singapore; Guruvaiah, Head (Controls), Shiv Kumar, Head (Fluid power), Trivedi, Head (Machine design) of TELCO, Pune ; Ricky Tan, Director (Automation), Md. Johari, Head (Tooling) of IBM Singapore Pvt. Ltd.; N. Sreekanth, Head (CAD/CAM), Kenny Kwan, Head (R&D) of ASM Technologies, Singapore; Joseph Ong, Head (CVD), Stanley Teo, Head (PVD) of ST Microelectronics, Singapore; James Lee, Director (Operations), Melvin Leo, Staff Engineer (Applications), APP Systems and Services, Singapore; Young Yee, Staff engineer (Process), Applied Materials, Korea; Young Yap, Director (Process), Applied Materials, Singapore; Ganesan, Staff Engineer (Equipment), Infineon, Malaysia.

Acknowledgements are also due to several of his colleagues at National Institute of Technology, Calicut. These include Dr. M.N. Bandyopadhyay, Director, who provided ideal learning atmosphere at NIT Calicut; Dr. A. Ramaraju and Dr. R. Sridharan for their encouragement and guidance. His boundless gratitude to Dr. T.J. Sarvoththama Jothi, Dr. Sudhakar Subudhi, Dr. N. Selvaraju and Dr. Mahesh Kumar for their help.

Dr. Gowda wishes to thank his wife M.S. Leelavathy, who stood by him throughout the preparation of the manuscripts with the resulting missed vacations and family weekends. He also wishes to thank his sons Ullas and Uttam, and his brother Paneesha Gowda for their love and affection. His special thanks to H.N. Suresh for his timely assistance.

It takes a team of many people and lots of hard work to create a quality textbook. Thanks most certainly to Wiley India for publishing this book in a short period. Many thanks to Mr. Praveen Settigere (Sr. Manager Acquisitions, Wiley India) who set the tone for excellence and who provided the vision and leadership to create such a quality product. Thanks are also to Ms. Meenakshi Sehrawat (Executive Editor, Wiley India) and Mr. Rupnarayan Das (Associate Editor, Wiley India) who worked long hours to improve our prose and produce this text from the first page of the manuscript to the final, bound product. We would also like to thank Mr. Rakesh Poddar (Production Editor, Wiley India) for meticulously managing the production-related jobs.

Acknowledgements

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Table 1 English alphabets

a Acceleration, m/s2 p Pressure, MPaA Area in m2 ppiston Pressure on piston, MPaArod Area of rod in m2 prod Pressure on rod, MPaApiston Area of piston in m2 p2 Inlet pressure, MPaAAnnulus Area of annulus in m2 p2 Outlet pressure, MPaAinlet Area at inlet, m2 Q Flow rate in LPM or m3/sAoutlet Area at outlet, m2 q Flow rate through valve in LPM or m3/sAv Area of valve in m2 ∆p Pressure drop in bar, or PaB Thickness of gear, m ∆pp Pressure drop across pump, Pac Radial clearance ∆pm Pressure drop across motor, PaCd Coefficient of discharge R Resistance, ΩCp Specific heat, W/kg °C RR Outer radius of output shaft, mD Diameter of piston, m RV Outer radius of vane, mDp Diameter of pipe, m Re Reynolds number, dimensionlessDi Inside diameter, m S Stroke, sDo Outside diameter, m S Stroke length of piston pumps, m DR Diameter of ring of vane pump, m T Time, sDC Diameter of cam ring of vane pump, m T Time constant, sd Diameter of rod, m Tq Torque, NmE Voltage drop, V TA Actual torque, NmEtotal Total energy, J TT Theoretical torque, NmE Eccentricity in vane pump, m V Volume, m3

F Force applied, N VD Displacement volume, m3

Finlet Force at inlet, N Vin Inlet volume, m3

Foutlet Force at outlet, N Vout Outlet volume, m3

G Gain ∆V Change in volume, m3

H Head of fluid in m v Velocity of flow or actuator, m/sHp Energy input to pump, J vforward Forward velocity of actuator, m/sHm Energy output from motor, J vret Retraction velocity of actuator, m/sHL Energy loss due to friction, J v1 Inlet velocity, m/sI Current, A v2 Outlet velocity, m/sI Moment of inertia, m4 W Weight, NLh Length of pipe Wd Work done, JK Roughness factor X Horizontal displacement, mK Ratio of outside diameter to inside diameter of pipe y Vertical displacement, mL Width of gear teeth, m Y No. of pistons in piston pumpsM Module of gear, m Z Elevation in, mn Revolution per second (RPS) Z1 Elevation at inlet, mN Revolution per minute (RPM) Z2 Elevation at outletP Power, W

Nomenclature

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xii Fluid Power: Generation, Transmission and Control

Table 2 Greek alphabets

a Pressure angle of gear w Angular velocity, rad/s

b Bulk modulus, MPa wn Natural frequency, Hz

be Effective bulk modulus, MPa h Efficiency, %

m Absolute viscosity, cP hm Mechanical Efficiency, %

v Kinematic viscosity, cSt ηmm Mechanical Efficiency of motor, %

r Mass density, ηmp Mechanical Efficiency of pump, %

ρoil Mass density of oil ho Overall efficiency, %

ρair Mass density of air q Inclination of lever, deg

ρwater Mass density of water q1 Inlet temperature, °C

ρmercury Mass density of mercury q2 Outlet temperature, °C

g Specific weight e Damping ratioγ oil Specific weight of oil d Logarithmetic decrement, m

γ water Specific weight of water µm Micron

t Shear stress, MPa f Inclination of cylinder

s Tensile stress, MPa

Table 3 Abbreviations

CNC Computer numerically controlledNC Normally closedNO Normally openFCV Flow control valveDCV Direction control valvePRV Pressure relief valveCF Coefficient of frictiondB decibelHP Horse power, HPSV Specific volume, m3/kgSG Specific gravityKE Kinetic energy, JPE Potential energy, JVI Viscosity indexVG Viscosity gradeOD Outer diameter, mID Inner diameter, mFOS Factor of safetyWP Working pressure of hose, MPaTF Transfer functionBP Burst pressure of hose, MPaHGR Heat generation rate, W

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Contents

About the authors vPreface viiAcknowledgements ixNomenclature xi

1 Introduction 1

Learning Objectives 1 1.1 Introduction 1 1.2 Fluid Power and Its Scope 1 1.3 Classification of Fluid Power Systems 3 1.4 Hydrostatic and Hydrodynamic Systems 4 1.5 History of Fluid Power 4 1.6 Advantages of a Fluid Power System 5 1.7 Disadvantages of a Fluid Power System 6 1.8 Basic Components of a Hydraulic System 6 1.8.1 Advantages of the Hydraulic System 7 1.8.2 Disadvantages of the Hydraulic System 8 1.9 Basic Components of a Pneumatic System 8 1.9.1 Advantages of a Pneumatic System 9 1.9.2 Disadvantages of a Pneumatic System 91.10 Comparison between Hydraulic and Pneumatic Systems 91.11 Comparison of Different Power Systems 91.12 Future of Fluid Power Industry in India 10 Summary 11 Objective-type Questions 11 Fill in the Blanks 11 State True or False 11 Review Questions 11 Answers 12

2 Properties of Fluid 13

Learning Objectives 13 2.1 Introduction 13 2.2 Solids and Fluids 13 2.2.1 Distinction between a Solid and a Fluid 13 2.2.2 Distinction between a Gas and a Liquid 13 2.3 Density, Specific Weight, Specific Volume and Specific Gravity 13 2.3.1 Density 13 2.3.2 Specific Weight 14 2.3.3 Specific Volume 15 2.3.4 Specific Gravity 15 2.4 Pressure 16 2.4.1 Pressure at the Bottom of a Column of Liquid 17 2.4.2 Atmospheric Pressure and Absolute Pressure 17 2.4.3 Gauge Pressure and Absolute Pressure 17 2.5 Compressible and Incompressible Fluids 19

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xiv Fluid Power: Generation, Transmission and Control

2.6 Bulk Modulus (Volume Modulus of Elasticity) 20 2.7 Reynolds Number 22 2.8 Types of Fluid Flow 22 2.9 Ideal Fluid 222.10 Viscosity 232.11 Viscosity Index 28 Summary 29 Key Equations 29 Objective Type Questions 29 Fill in the Blanks 29 State True or False 30 Review Questions 30 Exercises 30 Answers 31

3 Fluids for Hydraulic Systems 33

Learning Objectives 33 3.1 Introduction 33 3.2 Functions of Hydraulic Fluids 33 3.2.1 Ideal Viscosity 34 3.2.2 Lubrication Capability 36 3.2.3 Demulsibility 37 3.2.4 Good Chemical and Environmental Stability (Oxidation and Corrosion Resistance) 37 3.2.5 Neutralization Numbers 37 3.2.6 Incompressibility 37 3.2.7 Fire Resistance 38 3.2.8 Low Flammability 39 3.2.9 Foam Resistance 39 3.2.10 Low Volatility 39 3.2.11 Good Heat Dissipation 39 3.2.12 Low Density 39 3.2.13 System Compatibility 39 3.3 Additives in Hydraulic Fluids 40 3.4 Types of Hydraulic Fluids 40 3.5 Factors Influencing the Selection of a Fluid 42 Summary 42 Objective-Type Questions 42 Fill in the Blanks 42 State True or False 42 Review Questions 43 Answers 43

4 Governing Principles and Laws 45

Learning Objectives 45 4.1 Introduction 45 4.2 Brief Review of Mechanics 45 4.2.1 Energy 45 4.2.2 Power 46 4.3 Pascal’s Law 47 4.3.1 Multiplication of Force 47 4.3.2 Practical Applications of Pascal’s Law 59 4.4 Conservation of Energy 64 4.5 The Continuity Equation 65

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Contents xv

4.6 Bernoulli’s Equation from Newton’s Law 68 4.7 Bernoulli’s Equation from Energy Consideration 68 4.8 The Energy Equation 70 4.9 Elements of Hydraulic Systems and the Corresponding Bernoulli’s Equation 704.10 Torricelli’s Theorem 794.11 Siphon 80 Summary 83 Key Equations 83 Objective-Type Questions 84 Fill in the Blanks 84 State True or False 84 Review Questions 84 Exercises 84 Answers 87

5 Distribution of Fluid Power 89

Learning Objectives 89 5.1 Introduction 89 5.2 Choice of Distribution 89 5.3 Conductor Sizing 90 5.4 Burst Pressure and Working Pressure 90 5.5 Steel Pipes 91 5.6 Screwed Connections 95 5.7 Steel Tubing 96 5.8 Compression Joints 97 5.9 Plastic Conductors 1005.10 Flexible Hoses 100 5.10.1 Designation of Hoses 1015.11 Rotary Couplings 1035.12 Quick Disconnect Couplings 103 Summary 104 Key Equations 104 Objective-Type Questions 105 Fill in the Blanks 105 State True or False 105 Review Questions 105 Exercises 105 Answers 106

6 Energy Losses in Hydraulic Systems 107

Learning Objectives 107 6.1 Introduction 107 6.2 Laminar and Turbulent Flows 107 6.3 Reynolds Number 108 6.4 Darcy–Weisbach Equation 109 6.5 Frictional Losses in Laminar Flow 109 6.6 Frictional Losses in Turbulent Flow 110 6.6.1 Effect of Pipe Roughness 110 6.7 Frictional Losses in Valves and Fittings 111 6.8 Equivalent Length Technique 111 Summary 122 Key Equations 122 Objective-Type Questions 122

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Fill in the Blanks 122 State True or False 123 Review Questions 123 Exercises 123 Answers 124

7 Hydraulic Pumps 125

Learning Objectives 125 7.1 Introduction 125 7.2 Classification of Pumps 125 7.2.1 Classification Based on Displacement 125 7.2.2 Classification Based on Delivery 127 7.2.3 Classification Based on Motion 127 7.3 Pumping Theory 128 7.4 Gear Pumps 128 7.4.1 External Gear Pumps 129 7.4.2 Internal Gear Pumps 130 7.4.3 Gerotor Pumps 131 7.5 Lobe Pumps 134 7.5.1 Advantages 135 7.5.2 Disadvantages 135 7.5.3 Applications 135 7.6 Screw Pumps 136 7.7 Vane Pumps 137 7.7.1 Unbalanced Vane Pump with Fixed Delivery 137 7.7.2 Pressure-Compensated Variable Displacement Vane Pump (an Unbalanced

Vane Pump with Pressure-Compensated Variable Delivery) 138 7.7.3 Balanced Vane Pump with Fixed Delivery 138 7.7.4 Advantages and disadvantages of Vane Pumps 139 7.7.5 Expression for the Theoretical Discharge of Vane Pumps 140 7.8 Piston Pumps 140 7.8.1 Bent-Axis-Type Piston Pump 140 7.8.2 Swash-Plate-Type Piston Pump 142 7.8.3 Radial Piston Pump 142 7.8.4 Volumetric Displacement and Theoretical Flow Rate of an Axial Piston Pump 144 7.9 Comparison of Hydraulic Pumps 1467.10 Pump Performance 1467.11 Pump Performance Curve 1507.12 Pump Noise 1517.13 Pump Cavitation 152 7.13.1 Factors Causing Cavitation 152 7.13.2 Rules to Eliminate (Control) Cavitation 1527.14 Pump Selection 153 7.14.1 Maximum Operating Pressure 153 7.14.2 Maximum Delivery 154 7.14.3 Type of Control 154 7.14.4 Pump Drive Speed 154 7.14.5 Types of Fluid 154 7.14.6 Fluid Contamination 154 7.14.7 Pump Noise 155 7.14.8 Size and Weight of a Pump 155 7.14.9 Efficiency 155 7.14.10 Cost 155

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Contents xvii

7.14.11 Availability and Interchangeability 156 7.14.12 Maintenance and Spares 156 Summary 160 Key Equations 160 Objective-Type Questions 161 Fill in the Blanks 161 State True or False 161 Review Questions 161 Exercises 162 Answers 162

8 Hydraulic Actuators 165

Learning Objectives 165 8.1 Introduction 165 8.2 Types of Hydraulic Cylinders 165 8.2.1 Single-Acting Cylinders 165 8.2.2 Double-Acting Cylinder 167 8.2.3 Telescopic Cylinder 168 8.2.4 Tandem Cylinder 168 8.3 Standard Metric Cylinders 172 8.4 Cylinder Force, Velocity and Power 173 8.5 Acceleration and Deceleration of Cylinder Loads 175 8.5.1 Acceleration 175 8.6 Various Methods of Applying Linear Motion Using Hydraulic Cylinders 179 8.7 First-, Second- and Third-Class Lever Systems 186 8.7.1 First-Class Lever System 186 8.7.2 Second-Class Lever System 187 8.7.3 Third-Class Lever System 187 8.8 Cylinder Cushions 191 8.8.1 Cushioning Pressure 192 8.8.2 Maximum Speeds in Cushioned Cylinders 193 8.9 Cylinder Mountings and Strength Calculations 195 8.9.1 Piston Rod Ends 196 8.9.2 Protective Covers 196 8.9.3 Piston Rod Buckling 1968.10 Design of Cylinder Barrel 198 8.10.1 Cylinder Expansion Due to Hoop Stress 198 Summary 199 Key Equations 199 Objective-Type Questions 200 Fill in the Blanks 200 State True or False 200 Review Questions 200 Exercises 201 Answers 202

9 Hydraulic Motors 205

Learning Objectives 205 9.1 Introduction 205 9.2 Applications 205 9.3 Comparison Between a Hydraulic Motor and an Electric Motor 206 9.4 Classification of Hydraulic Motors 206 9.5 Gear Motors 206

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xviii Fluid Power: Generation, Transmission and Control

9.6 Vane Motors 207 9.7 Piston Motors 208 9.7.1 Axial Piston Motors 208 9.7.2 Bent-Axis Piston Motors 209 9.7.3 Radial Piston Motors 210 9.8 Semi-Rotary Actuators 211 9.8.1 Vane-Type Semi-Rotary Actuator (Single Vane) 211 9.8.2 Two-Vane-Type Semi-Rotary Actuator 211 9.8.3 Analysis Of a Semi-Rotary Single-Vane Motor 211 9.9 Chain and Sprocket Semi-Rotary Actuator 2129.10 Rack and Pinion Rotary Actuator 2139.11 Hydraulic Motor: Theoretical Torque, Power and Flow Rate 2139.12 Performance of Hydraulic Motors 2149.13 Performance Curves for a Variable Displacement Motor 220 Summary 222 Key Equations 222 Objective-Type Questions 223 Fill in the Blanks 223 State True or False 223 Review Questions 223 Exercises 223 Answers 224

10 Hydrostatic Transmission 225

Learning Objectives 225 10.1 Introduction 225 10.2 Advantages of a Hydrostatic Transmission 225 10.3 Components o f a Hydrostatic Transmission System 225 10.4 Analysis of a Hydrostatic System 226 10.4.1 Pump Characteristics 226 10.4.2 Motor Characteristics 227 10.4.3 Variable-Capacity Pump/Fixed-Capacity Motor Unit 229 10.4.4 Fixed-Capacity Pump/Variable-Capacity Motor Unit 234 10.4.5 Variable-Capacity Pump/Variable-Capacity Motor Unit 237 Summary 251 Key Equations 252 Objective-Type Questions 252 Fill in the Blanks 252 State True or False 252 Review Questions 253 Exercises 253 Answers 253

11 Directional Control Valves 255

Learning Objectives 255 11.1 Introduction 255 11.2 Directional Control Valves 255 11.2.1 Classification of DCVs based on Fluid Path 256 11.2.2 Classification of DCVs based on Design Characteristics 256 11.2.3 Classification of DCVs based on the Control Method 256 11.2.4 Classification of DCVs based on the Construction of Internal Moving Parts 256 11.3 Actuating Devices 258 11.4 Check Valve 260

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Contents xix

11.4.1 Advantages of a Poppet Valve 260 11.4.2 Disadvantages of a Poppet Valve 261 11.5 Pilot-Operated Check Valve 261 11.6 Shuttle Valve 261 11.7 Two-Way Direction Control Valves 262 11.7.1 2/2-Way DCV (Normally Closed) 262 11.7.2 2/2-Way DCV (Normally Opened) 263 11.7.3 Application of 2/2 DCV 263 11.8 Three-Way Direction Control Valves 264 11.8.1 3/2-Way DCV (Normally Closed) 264 11.8.2 3/2-Way DCV (Normally Opened) 265 11.8.3 Applications of 3/2 DCV and 3/3 DCV 265 11.9 Four-Way Direction Control Valves 267 11.9.1 Applications of 4/2 DCV and 4/3 DCV 26811.10 Solenoid-Actuated Valve 27211.11 Pilot-Operated Direction Control Valves 272 11.11.1 Applications of Pilot-Operated Valve to Control the Table of a Surface Grinder 27311.12 Piston Overlap 27411.13 Miscellaneous Industrial Circuits 27411.14 Direction Control Valve Mounting 27711.15 DCV Specifications 27811.16 Material for DCVs 278 Summary 283 Key Equations 283 Objective-Type Questions 283 Fill in the Blanks 283 State True or False 284 Review Questions 284 Exercises 284 Answers 285

12 Pressure-Control Valves 287

Learning Objectives 287 12.1 Introduction 287 12.2 Pressure-Relief Valves 287 12.2.1 Simple Pressure-Relief Valve 288 12.2.2 Compound Pressure Relief Valve (Pilot-Operated Pressure Relief Valve) 289 12.3 Pressure-Reducing Valve 292 12.4 Unloading Valves 295 12.4.1 Direct-Acting Unloading Valve 295 12.4.2 Pilot-Operated Unloading Valve 295 12.5 Counterbalance Valve 298 12.5.1 Application of a Counterbalance Valve 299 12.6 Source of Pilot Pressure in Counterbalance Valves 300 12.7 Pressure Sequence Valve 300 12.7.1 Application of a Sequence Valve 301 12.8 Cartridge Valves 302 12.8.1 Poppet-Type Cartridge Valves 302 Summary 304 Key Equations 304 Objective-Type Questions 305 Fill in the Blanks 305

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xx Fluid Power: Generation, Transmission and Control

State True or False 305 Review Questions 305 Exercises 305 Answers 306

13 Flow-Control Valves 307

Learning Objectives 307 13.1 Introduction 307 13.1.1 Functions of Flow-Control Valves 307 13.1.2 Classification of Flow-Control Valves 308 13.2 Speed-Controlling Circuits 311 13.2.1 Meter-In Circuit 311 13.2.2 Meter-Out Circuit 311 13.2.3 Bleed-Off Circuit 312 Summary 323 Key Equations 324 Objective-Type Questions 324 Fill in the Blanks 324 State True or False 324 Review Questions 324 Exercises 324 Answers 326

14 Hydraulic Circuit Design and Analysis 327

Learning Objectives 327 14.1 Introduction 327 14.2 Control of a Single-Acting Hydraulic Cylinder 327 14.3 Control of a Double-Acting Hydraulic Cylinder 328 14.4 Regenerative Cylinder Circuit 329 14.4.1 Expression for the Cylinder Extending Speed 329 14.4.2 Load-Carrying Capacity During Extension 330 14.5 Pump-Unloading Circuit 330 14.6 Double-Pump Hydraulic System 331 14.7 Counterbalance Valve Application 331 14.7.1 Valve Operation (Lowering) 332 14.7.2 Valve Operation (Lifting) 332 14.7.3 Valve Operation (Suspension) 332 14.8 Hydraulic Cylinder Sequencing Circuits 332 14.9 Automatic Cylinder Reciprocating System 33314.10 Locked Cylinder Using Pilot Check Valves 33414.11 Cylinder Synchronizing Circuits 334 14.11.1 Cylinders in Parallel 334 14.11.2 Cylinders in Series 33514.12 Speed Control of a Hydraulic Cylinder 336 14.12.1 Analysis of Extending Speed of Cylinder (Controlled) 336 14.12.2 Meter-In Versus Meter-Out Flow-Control Valve Systems 337 14.12.3 Speed Control of a Hydraulic Motor 33714.13 Fail-Safe Circuits 33814.14 Circuit for Fast Approach and Slow Die Closing 33914.15 Rapid Traverse and Feed, Alternate Circuit 340 Summary 373 Key Equations 373 Objective-Type Questions 374

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Contents xxi

Fill in the Blanks 374 State True or False 374 Review Questions 375 Exercises 375 Answers 377

15 Flow and Force Analysis of Valves 379

Learning Objectives 379 15.1 Introduction 379 15.2 Four-Way Spool Valves 379 15.2.1 Critical Center Valve 379 15.2.2 Open Center Valve (Underlapped Four-Way Valve) 381 15.3 Three-Way Spool Valves 382 15.3.1 Critical Center Valve 382 15.3.2 Open Center Valve (Under lapped Three-Way Valve) 384 15.4 Flapper Nozzle Valve 384 15.5 Special-Purpose Valves 386 15.5.1 Poppet Valves 386 15.5.2 Single-Stage Relief Valve 387 15.6 Pressure-Compensated Flow-Control Valve 388 15.6.1 Forces 388 15.6.2 Flow Rates 389 summary 392 Key Equations 392 Objective-Type Questions 392 Fill in the Blanks 392 State True or False 392 Review Questions 393 Exercises 393 Answers 394

16 Dynamic Analysis of Fluid Systems 395

Learning Objectives 395 16.1 Introduction 395 16.2 First-Order Systems 395 16.3 First-Order Fluid System 396 16.4 First-Order Electrical System 396 16.5 First-Order Fluid Hydraulic Servomechanism 397 16.5.1 The First-Order Equation 398 16.5.2 The Step Input 398 16.5.3 Response as a Function of Time 399 16.5.4 Ramp Input and Response for the First-Order Systems 399 16.5.5 Harmonic Input and Response 400 16.5.6 Harmonic Response of First-Order Systems 400 16.6 Graphical Representations 402 16.7 Harmonic Response Locus 403 16.8 Logarithmic Plots 403 Summary 410 Key Equations 410 Objective-Type Questions 411 Fill in the Blanks 411 State True or False 411 Review Question 411

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xxii Fluid Power: Generation, Transmission and Control

Exercises 411 Answers 412

17 Proportional Control Valves 413

Learning Objectives 41317.1 Introduction 413

17.2 History of Proportional Control Valves 413 17.3 Proportional Solenoids 414 7.3.1 Proportional Solenoids 414 17.4 Design Considerations of Proportional Control Valves 416 17.4.1 Force Position Control 416 17.4.2 Spool Positional Control 418 17.4.3 Proportional Pressure Control 419 17.4.4 Two-Stage Proportional Valves 420 17.4.5 Two-Stage Proportional Directional Control Valves 420 17.4.6 Two-Stage Proportional Relief Valve 421 17.4.7 Proportional Flow Control 421 17.5.1 Response Speed and Dynamic Characteristics 423 17.5.2 Hysteresis Effect 423 17.5.3 Null Position 424 17.6 Some Applications of Proportional Control Valves 424 17.6.1 Control of Actuators 424 17.6.2 Speed Control of Hydraulic Motors 425 17.7 Analysis of Proportional Valves 426 17.7.1 Overrunning Load 428 Summary 434 Key Equations 435 Objective-type questions 435 Fill in the Blanks 435 State True or False 435 Review Questions 435 Exercises 436 Answers 436

18 Servo Valves 437

Learning Objectives 437 18.1 Introduction 437 18.2 History of Electro hydraulic Servomechanisms 437 18.3 Electrohydraulic Servomechanism Concepts 438 18.4 Servo Valves 439 18.4.1 Torque Motor 439 18.4.2 Valve Spools 441 18.4.3 Valve Configurations 442 18.4.4 Single-Stage Spool-Type Servo Valve 442 18.4.5 Two-Stage Servo Valve 442 18.4.6 Double-Flapper Nozzle Pilot Stage 443 18.4.7 Jet Pipe Servo Valve 444 18.4.8 Pressure Flow Characteristics 445 18.4.9 Valve Performance 446 18.4.10 Gain and Feedback 447 Summary 453 Key Equations 453 Objective-Type Questions 453

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Contents xxiii

Fill in the Blanks 453 State True or False 454 Review Questions 454 Exercises 454 Answers 454

19 Accumulators 457

19.1 Introduction 457 19.2 Accumulator Selection 461 19.2.1 Sizing Accumulators for Isothermal Condition 461 19.2.2 Sizing Accumulators for Adiabatic Condition 462 19.2.3 Sizing Accumulators for Emergency Reserve 462 19.2.4 Sizing Accumulators for Pulsation Damping 462 19.2.5 Sizing Accumulators for Hydraulic Line Shock Damping 462 19.2.6 Sizing of Additional Gas Bottles 463 19.3 Applications of Accumulators 463 Summary 474 Key Equations 474 Objective-Type Questions 474 Fill in the Blanks 474 State True or False 475 Review Questions 475 Exercises 475 Answers 476

20 Accessories Used in Fluid Power Systems 477

Learning Objectives 477 20.1 Introduction 477 20.2 Functions of Seals 477 20.2.1 Classification of Hydraulic Seals 477 20.3 Durometer Hardness Tester 482 20.4 Reservoirs 482 20.4.1 Features of a Hydraulic Reservoir 483 20.4.2 Types of Reservoirs 484 20.4.3 Sizing of the Reservoir 484 20.4.4 Reservoir Design and Construction 486 20.5 Fluid Conditioners 487 20.5.1 Centralized Hydraulic System 487 20.5.2 Individual versus Centralized Systems 487 20.6 Filters and Strainers 488 20.6.1 Causes of Contamination 488 20.6.2 Types of Filters 489 20.6.3 Beta Ratio of Filters 492 20.7 Heat Exchangers 492 20.7.1 Sizing of Heat Exchangers 493 Summary 501 key equations 501 Objective-Type Questions 502 Fill in the Blanks 502 State True or False 502 Review Questions 502 Exercises 503 Answers 503

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xxiv Fluid Power: Generation, Transmission and Control

21 Maintenance of Fluid Power Systems 505

Learning Objectives 505 21.1 Introduction 505 21.2 The Importance of Cleanliness 506 21.3 Importance of Oil and Filter Changes 506 21.3.1 Draining the System 506 21.3.2 Cleaning and Flushing the System 506 21.3.3 Filling the System 506 21.3.4 Preventing Leaks 506 21.3.5 Preventing Overheating 507 21.4 Problems Caused By Gases in Hydraulic Fluids 507 21.4.1 Free Air 507 21.4.2 Entrained Gas 507 21.4.3 Dissolved Air 507 21.5 Troubleshooting Guides 508 21.5.1 Fluid Maintenance 508 21.5.2 In-Operation Care of Hydraulic Fluid 508 21.6 General Safety Rules for Electricity and Electronics 512 21.6.1 Solenoid Valves 513 21.7 Maintaining and Disposing of Fluids 515 Summary 515 Objective-Type Questions 515 Fill in the Blanks 515 State True or False 516 Review Questions 516 Answers 516

Appendix A 517

Appendix B 527

Appendix C 529

Appendix D 531

Appendix E 535

Glossary 537

Frequently Asked Questions 543

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