1、American Water Works Association 6666 W. Quincy Ave., Denver, CO 80235 (303) 794-771 1 . y!: : 4 e_ Erratum to M2 Instrumentation and Control (March ZOCZ) Corrections to figures: .- . . : : 1. .- - Motorized Conveyor Belt 7 . *.;. . -. . .- - .- . On page 151, Figure 8-9 should be as follows: 100 1
2、tI Linear - / Valve position as percent of open On page 158, Figure 8-16 should be as follows: On page 158, Figure 8-17 should be as follows: 0 Tank z- - - - - a z- - A Transfer Pumo To Adjust =- Dosage TO Process Positive Displacement Chemical Metering Pump On page 159, Figure 8-18 should be as fol
3、lows: Storage BaA 11 t Instrumentation and Control AWWA MANUAL M2 Third Edition American Water Works Association MANUAL OF WATER SUPPLY PRACTICES-M2, Third Edition Instrumentation and Control Copyright O 2001 American Water Works Association All rights reserved. No part of this publication may be re
4、produced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information or retrieval system, except in the form of hriaf excerpts or quotations for review purposes, without the written permission of the publisher. Library of Congress Catalogi
5、ng-in-Publication Data Instrumentation and control.- 3rd ed. p. cm. - (AWWA manual ; M2) New ed. of: Automation and instrumentation. 1983. Includes bibliographical references and index. ISBN 1-58321-125-X 1. Waterworks-Automation. I. American Water Works Association. II. Automation and instrumentati
6、on. III. Series. TD491 .A49 no. M2 2001 TD487 628.11 628.1 s-dc21 2001055311 Printed in the United States of America American Water Works Association 6666 West Quincy Avenue Denver, CO 80235 ISBN 1-5832 1 - 125-X Printed on recycled paper Contents List of Figures, v List of Tables, xi Foreword, xiii
7、 Acknowledgments, xv Chapter 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 The Water Utility System, 1 How to Use This Manual, 3 Reference, 4 Chapter 2 Hydraulics and Electricity . . . . . . . . . . . . . . . . . . . . . . . 5 Hydraulics, 5 Electricity, 18 Referenc
8、es, 39 Chapter 3 Motor Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Introduction, 41 Motors, 41 Variable Speed Motor Control, 49 Variable Speed Motor Control Systems, 50 Motor Control Logic, 52 Chapter 4 Flowmeters . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9、. . . . 67 Meter Categories, 67 Meter Coefficient of Discharge, 68 Venturi Flowmeters, 69 Modified Venturis, 74 Orifice Plate Flowmeters, 74 Magnetic Flowmeters, 76 Turbine and Propeller Flowmeters, 80 Sonic Flowmeters, 84 Vortex Flowmeters, 86 Averaging Pitot Flowmeters, 89 Variable Area Flowmeters
10、, 92 Open Channel Flow, 94 General Installation Precautions, 98 Signal Output and Transport, 99 References, 100 Chapter 5 Pressure, Level, Temperature, and Other Process Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 Pressure, Level, and Temperature, 102 Elect
11、ric Power and Equipment Status, 110 Process Analyzers, 112 General Considerations, 119 References, 119 . 111 Chapter 6 Secondary Instrumentation . . . . . . . . . . . . . . . . . . . . . 121 Introduction, 121 Signal Standardization, 121 Signal Power and Transmission, 122 Transmitters, 124 Controller
12、s, 124 Recording and Indicating Hardware, 126 Function Modules, 128 Converters, 129 Chapter 7 Telemetry . . . . . . . . . . . . . . . . . . . . . Analog Telemetry, 133 Tone Multiplexing, 137 Amplitude Modulation Tone, 137 Frequency Shift Keying Tone, 138 Communication Media and Channels, 138 Referen
13、ce, 142 131 Chapter 8 Final Control Elements . . . . . . . . . . . . . . . . . . . . . . . . 143 Valves, 144 Valve Summary, 153 Pumping Systems, 154 Miscellaneous Final Control Elements, 157 Chapter 9 Basics of Automatic Process Control . . . . Feedforward Control, 162 Feedback Control, 163 Feedforw
14、ard vs. Feedback Control, 164 Manual vs. Automatic Control, 165 Automatic Feedforward Control Methods, 166 Automatic Feedback Control Methods, 168 References, 178 . . . . . . . 161 Chapter 10 DigitalControl and Communication Systems . . . . . . . . . 179 Digital Control Systems, 180 Communication Sy
15、stems, 188 Applications and Site Planning, 194 Technology Trends, 196 References, 197 . . . . . . . 199 Chapter 11 Instrument Diagrams . . . . . . . . Glossary, 207 Index, 215 List of AWWA Manuals, 225 iv Figures 2-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8 2-9 2-10 2-11 2-12 2-13 2-14 2-15 2-16 2-17 2-18 2-19a
16、2-19b 2-20 2-2 1 3- 1 3-2 3-3 3-4 3-5 3-6 3-7 3-8 3-9 3-10 Pressure in a tank, 7 Pressure in containers of various shapes, 7 Water level in an unpressurized system, 8 Fluid levels in a vacuum system, 8 Flow velocity as a function of cross-sectional area, 9 Flow-velocity profiles, 9 Determination of
17、static pressure, 9 Water in pipe with pressure, no flow, 10 Total head, 11 Elevation head, 11 Flowing without friction, 12 Velocity head, 12 Flowing with friction, 13 Flowing with friction, 15 Mechanical leverage compared to .,ydraulic I,rce, 16 Hydraulic force, 17 Differential areas, 17 Transformer
18、 symbol, 24 Delivery voltage at 480 VAC using electric utilitys transformer, 25 Delivery voltage at 21,000 VAC using water utilitys transformer, 25 Main substation with switchgear, 26 Complete one-line with load center and motors, 28 Induction motor rotors, 43 Motor starter contactor coil, 53 Motor
19、starter circuit with one switch, 53 Motor starter circuit with two switches, 54 Maintained contact switch symbol, 54 Momentary contact switch symbols, 54 Momentary start switch circuit, 55 Control relay coil symbol, 55 Control relay contact symbols, 55 Three-wire motor control circuit, 56 V 3-11 3-1
20、2 3-13 3-14 3-15 3-16 3-17 3-18 3-19 3-20 3-21 3-22 3-23 3-24 3-25 4-1 4-2 4-3 4-4 4-5 4-6 4-7 4-8 4-9 4-10 4-11 4-12 4-13 4-14 4-15 4-16 4-17 5-1 5-2 5-3 Three-wire motor control circuit with two control locations, 57 Ladder diagram with line numbers, 57 Status indicating light symbol, 58 Motor cir
21、cuit with indicating lights, 58 Selector switch symbol, 58 Motor circuit with local-remote switch, 59 Hand-off-auto switch, 59 HOA motor circuit, 60 Float-operated level switch symbol (closes on rising level), 60 Float-operated level switch symbol (opens on rising level), 60 Automatic pump control o
22、ff of a float switch, 61 Three-wire control using two level switches, 61 Three-wire control using two level switches with lock-out-stop switch, 63 Three-wire control using two level switches with lock-out-stop switch and a low-level interlock switch, 64 Electrical ladder diagram symbol legend, 65 Th
23、e Venturi tube, 69 Venturi meter and flow tube, 70 Troubleshooting guide for a differential pressure transducer, 72 Orifice plate, 75 Magnetic flowmeter, 77 Example of a troubleshooting flowchart, 78 Propeller and turbine meters, 81 Troubleshooting procedures for turbine meter, 82 Ultrasonic time-of
24、-flight flowmeter, 84 Vortex flowmeter, 87 Vortex flowmeter troubleshooting guide, 88 Averaging Pitot flowmeter insertion tube, 90 Variable area flowmeter, 92 Common types of weirs, 95 Free flow over a weir, 96 Parshall flume, 97 Typical flow straighteners, 99 Bourdon, bellows, and diaphragm pressur
25、e sensors, 103 Typical LVDT application, 103 Diaphragm seal, 104 vi I 5-4 5-5 5-6 5-7 5-8 5-9 5-10 5-11 5-12 5-13 5-14 5-15 5-16 5-17 5-18 5-19 5-20 5-21 5-22 6- 1 6-2 6-3 6-4 6-5 6-6 6-7 7-1 7-2 7-3 7-4 8- 1 8-2 8-3 8-4 8-5 Variable capacitance pressure sensor, 104 Float-type, level-sensing system,
26、 105 Stage recorder, 106 Bubbler, 106 Admittance probe, 107 Variable resistance level sensor, 108 Ultrasonic level sensor, 108 Typical temperature elements, 109 Thermowell, 110 Motor current sensor, 111 Light scatter turbidity, 113 Surface scatter, 114 pH system, 114 Immersion and flow-through pH sy
27、stems, 115 Chlorine membrane probe, 116 Amperometric chlorine residual analyzer, 117 CO2 buffering, 117 Particle counter, 118 Streaming current monitor, 118 Typical single compressor system, 124 Power supply, 125 Basic controller, 125 Analog indicator, 126 Analog and digital indicator, 126 Circular
28、recorder, 127 Strip chart recorder, 127 Telemetering, 132 Typical digital telemetering system, 134 Schematic of a typical PDM system, 135 Nomenclature of frequencies, 140 Components of control, 144 Solenoid with cylinder actuator, 145 Solenoid with details, 145 Single-phase motor, 146 Pneumatic posi
29、tioner cut away, 147 vii 8-6 8-7a 8-7b 8-8 8-9 8-10 8-11 8-12 8-13 8-14 8-15 8-16 8-17 8-18 8-19 8-20 8-21 9-1 9-2 9-3 9-4 9-5 9-6a 9-6b 9-7a 9-7b 9-8 9-9a 9-9b 9-10a 9-10b 9-lla 9-llb 10-1 10-2 Electronic positioner circuitry, 147 Rotary valve requires torque, 148 Linear valve requires thrust, 148
30、Piping configurations, 149 Control characteristics, 151 Butterfly valve, 151 Plug valve, 152 Gate valve, 152 Globe valve, 152 Discharge pressure control via series valve, 156 Discharge pressure control via bypass valve, 157 Pneumatic conveying system, 158 Chemical feed system (liquid), 158 Chemical
31、feed system (dry), 159 Typical rotary paddle volumetric feeder, 159 Screw-type volumetric feeder, 160 Gravimetric feeder (belt type), 160 Generic control loop, 162 Feedforward control of chlorine contact channel, 163 Feedback control of chlorine contact channel, 164 Compound control of chlorine cont
32、act channel, 166 Generic feedback control timing graph, 169 On-off control of a reservoir, 170 On-off control timing graph, 170 Gap-action control of a reservoir, 171 Gap-action control timing graph, 171 Proportional control inputoutput relationship, 172 Proportional control of a reservoir, 173 Prop
33、ortional control timing graph, 173 Integral control of a reservoir, 175 Integral control timing graph, 175 Proportional-plus-derivative control of a reservoir, 177 Proportional-plus-derivative control timing graph, 178 Digital control system, 181 Operating system, 187 viii 10-3 10-4 10-5 Networks, 1
34、92 11-1 11-2 11-3 11-4 Layers of communications, LAN, WAN, 190 Reference model for open system interconnection, 190 General instrument or function symbols, 201 Function designations for relays, 202 Standard instrument line symbols, 203 Example of PI some will be hydraulic systems, using water or oil
35、 pressure for power sources and control; some will be pneumatic systems, using compressed air for power, control, and instrumentation; and some will be electrical systems for power, control, and instrumentation. A swing check valve will close automatically, for example, when not forced open by the f
36、low of water through it. An indicating pointer can be positioned by a system of cable and pulleys to provide position indication. Oil or water pressure can be used to hold a valve closed, whereupon the loss of pressure will cause it to open automatically. Similarly, compressed-air pneumatic systems
37、can be arranged to cause devices to operate automatically; pneumatic instrumentation and control systems are used extensively. Electricity is used more than any other source of power for control and instrumentation. Generally, an electrical system, together with various mechanical, hydraulic, and pn
38、eumatic subsystems, allows an operator to supervise and control the water system. These electrical systems may include any or all of the following: Power system, using local, remote, or automatic control Telemetering, monitoring, and alarm system Communication system, data acquisition, and data proc
39、essing Operations are performed automatically for several reasons: the operator does not have to do them the operator cannot do them they can be done faster and better automatically they can be more efficient As with automation, instrumentation is an extension of the operator. Instru- ments see, feel, measure, and record information for the operator. Instruments can perform a variety of operations, including: measuring monitoring comparing remembering signaling regulating calculating switching transmitting receiving recording indicating
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