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By K. T. Jadhav

Size : B5, Pages: 428; Price : Rs. 390.00

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- 1. i PROCESS DYNAMICS AND CONTROL Mr. K. T. Jadhav B. Tech (Petrochemical Engineering ) Dr. B. A. Tech. University, Lonere. M.E. (Chemical Engineering) M. S. University, Baroda. Presently Head and Assistant Professor, Department of Chemical Engineering , D. Y. Patil College of Engineering and Technology, Kolhapur. CHINTTAN PUBLICATIONS 4/8, Anandnagar, Paud Road, Kothrud, Pune-411038.
- 2. ii First Indian Edition 2006 This Book contains information obtained from authentic and highly regarded resources. Reprinted Material is quoted with permission, and resources are indicated. A wide variety of references are listed. Reasonable efforts have been made to publish reliable data and information, but the author and the publisher cannot assume responsibility for the validity of all materials or for the consequences of their use. Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfilming, and recording or by any information storage or retrieval system, without prior permission in writing from the publisher. The consent of Centre: Technical Co-ordination does not extend to copying for general distribution, for promotion, for creating new works, or for resale. Specific permission must be obtained in writing from Chinttan Publications for such copying. Direct all enquiries to Centre: Technical Co-ordination: 8888101055 and 9226269333. Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation, without intent to infringe. Customer care: 8888101055, 9226269333 (WhatsApp) Visit our Web site at www.chinttanpublications.in The Indian Edition : Rs. 390.00 PROCESS DYNAMICS and CONTROL 1st Edition By K. T. Jadhav © 2006, Chinttan Publications 4/8, Anandnagar, Paud Road, Kothrud , Pune – 411038. Mobile: 8888101055,9226269333. E-mail: chinttanpublications@gmail.com and Printed in Pune.
- 3. iii PREFACE This book has the aims of: To provide fundamentals of Process Dynamics and Process Control. This book is written in such a simple and easy way to understand the language, so students will not only understand it completely but also they will enjoy its reading. Each chapter contains simple theory, carefully selected examples and various exercises to ensure that students clear understanding of the concept and its applications. Reasonable Efforts have taken to make this book simple, clear and focused. This book covers entire syllabus of process dynamics and control. There is a thorough coverage of topics like dynamic behaviour of various systems, transfer functions, basic mechanism of control system, control aspects, controllers, control valves and stability analysis of given control system by Routh test, Root locus method and Bode Diagram, etc. Courses for which suitable The book more than covers the Process control related part of the Diploma / Bachelors / Masters Degree in Chemical, Engineering, Instrumentation Engineering Petrochemical Engineering, Polymer Technology, Petroleum Engineering, Bio- Technology and Instrument Technology. It is also seen as being of value to students of MSc, BSc, Instrumentation and Technology Science. Background knowledge assumed A basic knowledge of science and mathematics has been assumed. The science required is basic physical science. Key elements of science are developed in appropriate chapters. The mathematics required is just the ability to handle the numbers, integration, summation, interpret graphs and in a few instances handle simple algebraic equation. Mr. K. T. Jadhav
- 4. iv ACKNOWLEGEMENT I would like to give my deep sense of gratitude to the Chairman Hon’ble Sanjay D. Patil, Principal Dr. A. N. Chapgaon, Director Bridg. U. D. Thorat and Director of Admin. Col. S. K. Joshi for constant encouragement and support. I am also thankful to my colleagues and friends for timely help and support which encourage me to write this book. I give special thanks to my Publisher Mr. Chintan Dewalia, Mr.Vinod Kapse and his staff of Centre: Technical Co-ordination for their countless efforts and support for bringing this book with great care and innovative ideas. Suggestion from readers will be highly appreciated. K. T. Jadhav
- 5. v Dedicated to... My Parents and My Wife
- 6. TABLE OF CONTENTS vi TABLE OF CONTENTS CHAPTER 1 - BASIC PRINCIPLES OF PROCESS CONTROL 1-28 1.1 Historical background 1 1.2 Process control system 2 1.3 Languages of process control 3 1.4 Basic principles and objectives of process control 4 1.5 Laplace transform 5 1.6 Forcing functions 9 1.7 Initial and final value theorem 13 1.8 Process modeling and analysis 14 1.9 Formulating process models 15 1.10 State space model 16 1.11 Transfer functions model 17 Solved Problems – 1.1 to 1.7 19 Unsolved Problems 27 CHPATER 2 - FIRST ORDER SYSTEMS 29-62 2.1 Mercury in glass thermometer 29 2.2 Transfer function 32 2.3 Time constant 33 2.4 Transient response of first order system 34 Solved Problems – 2.1 to 2.6 46 Unsolved Problems 62
- 7. PROCESS DYNAMICS AND CONTROLS vii CHAPTER 3 - PHYSICAL EXAMPLES OF FIRST ORDER SYSTEMS 63-126 3.1 Single liquid level system 63 3.2 Single liquid level system with constant outlet 66 3.3 Resistance – capacitance system 67 3.4 Mixing process 70 3.5 Constant stirred tank heater 72 3.6 First order systems are in series 74 3.7 Generalization of non interacting systems in series 81 3.8 Linearization of non linear systems 83 3.9 Transportation lag or dead time 86 3.10 Comparison between non interacting and interacting system 88 Solved Problems – 3.1 to 3.11 89 Unsolved Problems 124 CHAPTER 4 - SECOND ORDER SYSTEM 127-156 4.1 U tube manometer 127 4.2 Damped vibrator 130 4.3 Damped coefficient 133 4.4 Transient response for second order system 134 4.5 Characteristics of under damped system for step change 140 4.6 Comparison of first order system and second order system 143 Solved Problems – 4.1 to 4.4 144 Unsolved Problem 154 CHAPTER 5 - MECHANISM OF CONTROL SYSTEM 157-178 5.1 Control system for continuous stirred tank heater 157
- 8. TABLE OF CONTENTS viii 5.2 Block diagram of the control system 158 5.3 Feedback control systems 160 5.4 Servo & regulator control problems 161 5.5 Development of block diagram 163 Solved Problem – 5.1 to 5.2 168 CHAPTER 6 - FINAL CONTROL ELEMENT & CONTROLLERS 179-212 6.1 Pneumatic control valves 179 6.2 Valve characteristics 181 6.3 Valve sizing 182 6.4 Valve positioners 183 6.5 Transfer functions for the control valve 185 6.6 Control hardware for temperature of leaving stream through heat exchanger 188 6.7 Controllers 190 6.8 Comparison of the controllers 194 6.9 Applications of the controllers 196 6.10 Chemical reactor control system 197 Solved Problems – 6.1 to 6.5 201 Unsolved Problems 211 CHAPTER 7 - OVERALL TRANSFER FUNCTION 213-228 7.1 Open loop & closed loop transfer function 213 7.2 Overall transfer functions for change in set point 214 7.3 Overall transfer function for change in load variable 216 Solved Problems – 7.1 to 7.6 218 Unsolved Problems 227
- 9. PROCESS DYNAMICS AND CONTROLS ix CHAPTER 8 - TRANSIENT RESPONSE OF CONTROL SYSTEMS 229-258 8.1 Offset 229 8.2 Proportional controller for servo mechanism control problem 230 8.3 Proportional controller for regulator mechanism control problem 232 8.4 Proportional integral controller for servo mechanism control problem 234 8.5 Proportional integral controller for regulator mechanism control problem 236 8.6 Proportional derivative controller for servo mechanism control problem 238 8.7 Proportional derivative controller for regulator mechanism control problem 241 8.8 PID controller for servo mechanism control problem 243 8.9 PID controller for regulator mechanism control problem 245 Solved Problems – 8.1 to 8.3 248 Unsolved Problems 257 CHAPTER 9 – STABILITY CRITERION OF CONTROL SYSTEM 259-276 9.1 Stability of control system 259 9.2 Characteristics equation 259 9.3 Stability criterion 260 9.4 Routh - Hurwitz stability criterion 261 Solved Problems – 9.1 to 9.5 264 Unsolved Problems 276 CHAPTER 10 - ROOT LOCUS METHOD 277-300 10.1 Root locus method 277 10.2 Rules for plotting root locus diagram 277 10.3 Nature of root loci 280 Solved Problems – 10.1 to 10.3 281 Unsolved Problems 299
- 10. TABLE OF CONTENTS x CHAPTER 11 - INTRODUCTION TO FREQUENCY RESPONSE 301-340 11.1 Bode diagram 301 11.2 Bode diagram for first order system 301 11.3 Bode diagram for first order systems in series 304 11.4 Bode diagram for second order system 305 11.5 Bode diagram for transportation lag 306 11.6 Bode diagram for proportional controller 308 11.7 Bode diagram for proportional integral controller 309 11.8 Bode diagram for proportional derivative controller 311 11.9 Bode diagram for proportional integral derivative controller 313 11.10 Rules for plotting Bode diagram for the control system 317 11.11 Bode stability criterion 317 11.12 Gain and phase margin 318 11.13 Ziegler Nichols optimum controller settings 320 11.14 Cohen and Coon rules 322 11.15 Nyquist stability criterion 325 Solved Problems – 11.1 to 11.2 328 Unsolved Problems 339 CHAPTER 12 - ENHANCEMENT OF SINGLE LOOP PID FEEDBACK CONTROLLERS 341-348 12.1 Cascade control 341 12.2 Feed forward control 343 12.3 Ratio control 344 12.4 Selective control 345 12.5 Split range control 346
- 11. PROCESS DYNAMICS AND CONTROLS xi CHAPTER 13 – INDUSTRIAL APPLICATIONS 349-356 13.1 Process control symbols 349 13.2 Stirred tank heater 351 13.3 Batch reactor 351 13.4 Distillation column 352 13.5 Compressor 352 13.6 Surge vessel level 353 13.7 Heat exchangers 353 13.8 Plug flow reactor 354 *13.9 Steam drum level 355 13.10 Plant wide control 355 13.11 Ph control 356 CHAPTER 14 – PROCESS INSTRUMENTATION 357-378 14.1 Elements of instrument 357 14.2 Static characteristics of an instrument 358 14.3 Dynamic characteristics of an instrument 359 14.4 Functions of instruments 359 14.5 Temperature measuring instruments 360 14.6 Pressure measuring instruments 366 14.7 Level measuring instruments 371 14.8 Flow measuring instruments 374 IMPORTANT QUESTION OF GATE EXAM 379-416 REFERENCES 417 INDEX 419-421
- 12. INDEX CENTRE : TECHNICAL CO-ORDINATION 419 INDEX A Amplitude ratio, 45,139,302,317 Asymptotes, 279 angles, 279 B Batch reactor, 351 Bimetallic Thermometer, 360 Block diagram, 158-167 chemical reactor, 197-200 standard block diagram, 159 Bode diagram, 301-317 Controllers, 308-316 first order system, 301 rules for plotting bode plot, 317 second order system, 305 transportation lag, 306-307 C Capacitance, 33,67-71 *Cascade control, 341-343 Characteristics equation, 259-264 roots of characteristics equation, 261-264 Chemical reactor control system, 196-200 Closed loop transfer function, 213-217 Comparator, 158-159 Cohen and Coons rules, 322-325 Compressor, 353 Constant stirred tank heater, 71-73, 57-59 Control hardware, 188-190 Control elements, 158 Controlled variables, 158-160 Controller, 166-167,190-196,308-316 Proportional, 166-167, 190-191, 308 proportional – integral, 191-192, 309-311 proportional – derivative, 192-193, 311-313 PID Controller, 193-194, 313-316 Control valve, 179-188 air to open, 179-180 air to close, 180-181 mechanism, 179-181 transfer function, 185-188 Corner frequency, 302-316 Critically damped system, 133, 136-137, 138 Cross over frequency, 319 Cyclic frequency, 142-143 D Damped vibrator, 130-133 Damping coefficient, 133-134 Dead time, 85-87 Dead zone, 358-359 Decay ratio, 141-142 Derivates, 8-9 Laplace transform, 8-9 Distillation column, 352 Drift, 358 E Elements, 157-159 of control systems, 158-159 of instruments, 357-358 F Feedback control, 160-161 negative feedback, 160-161 positive feedback, 161 Feed forward control, 343-344 Final control element, 158-159,167 Final value theorem, 13 First order system, 29-45, 63-80, 301-304 impulse change, 36-38 in series, 73-80 interacting system, 77-80, 38 non interacting system, 73-77, 88 sinusoidal change, 41-45, 301-304 step change, 34-36 time constant, 33-34 transfer function, 32-33 Float and tape liquid level, 370-371 Forcing function, 9-13 Flow measuring instruments, 372-377 Impulse, 11 Ramp, 12 Sinusoidal, 12 Step, 10 Formulating process models, 15-16 Frequency response, 301-319 Bode diagram, 301 first order, 301-304 second order, 305-306 transportation lag, 306-308 Function of instruments, 359-360
- 13. PROCESS DYNAMICS AND CONTROL CENTRE : TECHNICAL CO-ORDINATION 420 G Gain margin, 320 Gain, 190-194, 321-322 of controller, 190-194 ultimate, 321-322 GATE exam questions, 379-415 Generalization of non interacting systems, 80-82 H Heat exchangers, 354 Heaters, 71-73, 157-160 I Impulse change, 36-38, 137-139 Impulse function, 11 Initial value theorem, 13 Integral action, 191-196 Interacting system, 77-80, 88 Interface level measuring unit, 372 Ionization of vacuum gage, 369-370 L Lag Transfer, 82 Phase, 139-140 Laplace transform, 5-9 Languages of process control, 3 Level measuring instruments 370-372 Linearization, 82-85 Liquid level system, 63-67 constant flow outlet, 66-67 Load variable, 158-167 M Manometer, 127-130 Manipulated variable, 158-160 Measuring element, 165-166, 157-160 Mercury thermometer, 29-32 Mec leod vacuum gauge, 368-369 Mixing process, 70-71 Mechanism of control system, 179-181 Multi loop systems, 341-347 N Natural frequency, 142-143 Natural period of oscillation, 143 Negative feed back system, 160-161 Non interaction system, 73-77 transfer function, 77 Non linear system, 82-85 Nyquist stability criterion, 325-328 O Offset, 229-247 P controller, 230-234 PI controller, 234-238 PD controller, 238-243 PID controller, 243-247 Open loop transfer function, 213 Optical pyrometer, 364 Over damped system, 133, 137, 138 Overall transfer function, 213-217 Closed loop system, 213-217 Open loop system, 213 Overshoot, 140-141 P Period of oscillation, 142-143 Phase angle, 45 Phase lag, 140 Phase margin, 320 Plant wide control, 355 Plug flow reactor, 354 Positive feedback, 161 Potentiometer, 365-366 Process instrumentation, 357-377 Process control symbols, 349-350 Pressure gauges, 366-367 Pressure measuring instruments, 366-370 Pressure spring thermometer, 362-363 Proportional controller, 166-167, 308-309, 230-234 transfer function, 190-191 Proportional integral controller, 191-192, 194-196, 234-238 transfer function, 191-192 Proportional derivative controller, 192-193, 194- 196, 238-243 transfer function, 192-193 Proportional integral derivative controller, 193-194, 195-196, 243-247 transfer function, 193-194 R Radiation pyrometer, 363-364 Ramp change, 38-41 Ramp function, 10, 12 Ratio control, 344-345 R C circuit, 67-70
- 14. INDEX CENTRE : TECHNICAL CO-ORDINATION 421 Regulator problems, 162-163, 232-247 Resistance, 63-70 Linear resistance, 63-67 Resistance thermometer, 364-365 Response time, 142 Rise time, 142 Root locus, 277-281 plotting of diagram, 281 rules for plotting, 277-281 Roots of characteristics equation, 261-264 Routh Hurwitz criterion, 261-264 routh array, 262-263 stability criterion, 261-262 S Second order system, 127-143, 305-306 impulse change, 137-139 sinusoidal change, 139-140 step change, 134-136 transfer function, 127-133 Selective control, 345-346 Sensitivity, 190-194, 359 of controller, 190-194 of instruments, 359 Sinusoidal change, 41-45, 139-140 first order, 41-45 second order, 139-140 Servo mechanism control problems, 161-162 Split range control, 346-347 Stability, 259-264 Bode stability criterion, 317-318 Definition, 259 Routh test, 261-264 State space model, 16-17 Static characteristics, 358-359 Steam drum level, 355 Steady state gain, 190-194 Step function, 10 Stirred tank reactor, 71-73, 157-160, 351 block diagram, 158-159 transfer function, 164-165 Surge vessel level, 353 T Taylor’s series of expansion, 83-84 Temperature measuring instruments, 360-366 Thermocouples, 33-34 Time constant, 361-362 Transfer function, 32 Transfer function model, 18-19 Transfer lag, 81-82 Transducer, 188-189 Transportation lag, 85-87, 306-308 transfer function, 87 Transform, 5-9 Laplace transform, 5-9 Translation, 13-14 of function, 14 of transform, 13 U Under damped system, 133-143 Ultimate value, 140-142 Ultimate period, 321-322 U tube monometer, 127-130 V Valve, 179-188 Characteristics, 181-182 Coefficient, 182-183 equal percentage, 182 hysteresis, 183-184 linear, 179 positioners, 183-184 sizing, 182-183 transfer function, 185-188 Z Zeros, 278-281 Open loop, 278-281 Ziegler Nichols controller settings, 320-322

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