Instrumentation Fundamentals for Process Control

by de Sa; Douglas O

• ISBN13: 9781560329015
• ISBN10: 1560329017
• eBook ISBN(s): 9781351438070
• Format: Hardcover
• Copyright: 2001-07-09
• Publisher: CRC Press
• More Book Details

Summary

A practical introductory guide to the principles of process measurement and control. Written for those beginning a career in the instrumentation and control industry or those who need a refresher, the book will serve as a text or to supercede the mathematical treatment of control theory that will continue to be essential for a well-rounded understanding. The book will provide the reader with the ability to recognize problems concealed among a mass of data and provide minimal cost solutions, using available technology.

Table of Contents

Preface	xxi
Introduction: Concepts in Instrumentation for Process Control	xxiii
Fundamentals of Process Control	xxiii
Illustration: A Simple Control System	xxviii
Components of the System	xxviii
Operation and Regulation	xxx
Modern Instrumentation and its Evolution	xxxi
Summary	xxxiv
Road Map Through this Book	xxxv
Primary Devices and Measurements	xxxv
Process Control	xxxvi
Applications	xxxvi
Final Control Devices	xxxvi
Installation of Instrumentation	xxxvi
Modern Control Systems	xxxvi
Notations Used in this Book	xxxvii
Notations Used in Chapters on Measurements	xxxvii
Notations Used in Chapters on Control	xxxvii
Part I PRIMARY DEVICES AND MEASUREMENTS	1	(124)
Flow Measurement	3	(28)
Basic Theory of Flow	3	(3)
Primary Differential-Pressure Devices	6	(8)
The Venturi Meter	6	(2)
Other Primary Differential-Pressure Devices	8	(1)
Venturi Flumes	9	(1)
Orifice Plates, Dall Tubes, and Flow Nozzles	9	(2)
Measuring Devices for Viscous Liquids	11	(1)
The Target Meter	12	(1)
Positive-Displacement Meter (Oval-Gear Type)	13	(1)
Differential-Pressure-Measuring Instruments	14	(2)
Differential-Pressure Cells	14	(1)
U-Tube Manometers	14	(1)
Ring Balances	15	(1)
Bell-Type Meters	15	(1)
Slack Diaphragm	16	(1)
Virtually Obstructionless Flow-Measuring Instruments	16	(9)
The Electromagnetic Flowmeter	17	(1)
The Vortex Flowmeter	18	(1)
The Turbine Flowmeter	19	(1)
The Coriolis Mass Flowmeter	20	(3)
Ultrasonic Flow Measurement	23	(1)
The Doppler-Effect Ultrasonic Flowmeter	23	(1)
The Time-of-Flight Ultrasonic Flowmeter	24	(1)
Hot-Wire Anemometers	25	(1)
Data Required to Provide a Measurement of Process Flow	25	(2)
Process Fluid	25	(1)
Process Parameters	26	(1)
Physical Location	26	(1)
Primary Device	26	(1)
Application	27	(1)
Criteria for Selecting a Suitable Flow-Measuring Instrument	27	(1)
Sensing Elements	27	(1)
Operating Range	27	(1)
Aggressive Fluids	28	(1)
Materials of Construction	28	(1)
Chemical Seals	28	(1)
Summary	28	(3)
Pressure Measurement	31	(20)
Basic Theory and Definitions	32	(1)
Pressure-Measuring Devices	33	(6)
The U-Tube Manometer	33	(1)
The Bourdon Tube Sensor	34	(1)
The Bellows-Type Sensor	35	(1)
The Diaphragm Capsule	35	(1)
Measuring Absolute Pressure	36	(1)
The Strain Gauge Sensor	36	(1)
The Piezoresistive Sensor	37	(1)
The Resonating-Microstructure Sensor	37	(1)
The Deforming-Microstructure Capacitive Sensor	38	(1)
Using Pressure Measurement to Determine Liquid Level	39	(3)
Open-Top and Closed Vessels	39	(1)
The Submersible Diaphragm Sensor	40	(1)
Air Reaction Method: The Bubble Tube	40	(2)
Using Pressure Measurement to Determine Slurry Level or Slurry Flow: Liquid Reaction Method	42	(1)
Data Required to Provide a Measurement of Process Pressure	42	(1)
Process Fluid	42	(1)
Process Parameters	42	(1)
Physical Location	42	(1)
Application	43	(1)
Criteria for Selecting a Suitable Pressure-Measuring Instrument	43	(4)
Operating Range	43	(1)
Sensing Elements	43	(1)
Pressure Pulsation	44	(1)
Aggressive Fluids	45	(1)
Materials of Construction	45	(1)
Chemical Seals	45	(1)
Material of the Seal	45	(1)
Considerations for Chemical Seals	46	(1)
Fill Fluids for WIKA Seals	47	(1)
Summary	47	(4)
Temperature Measurements	51	(24)
The Temperature Scales	51	(2)
Temperature Measurement Systems---Mechanical	53	(3)
Solids: The Bimetallic Thermometer	53	(1)
Liquids: Mercury-in-Steel and Aromatic Petroleum Liquid Systems	54	(1)
Gas- and Vapor-Filled Systems	55	(1)
Correcting Filled Systems	55	(1)
Temperature Measurement Systems---Electrical	56	(9)
Thermocouples	56	(3)
Thermal Resistive Sensors	59	(1)
The Gas Scale	59	(1)
The Platinum Scale	60	(1)
International Practical Scale of Temperature (IPST)	61	(1)
Radiation Pyrometry	62	(3)
Data Required to Provide Measurement of Process Temperature	65	(1)
Process Fluid	65	(1)
Process Parameters	65	(1)
Physical Location	66	(1)
Application	66	(1)
Criteria for Selecting a Suitable Temperature-Measuring Instrument	66	(4)
Operating Range	66	(1)
Sensing Elements	67	(1)
Liquid Filling	68	(1)
Vapor-Pressure Elements	68	(1)
Thermocouples	69	(1)
Base Metal	69	(1)
Rare Metal	69	(1)
Resistance Temperature Detectors	70	(1)
Aggressive Fluids	70	(1)
Materials of Construction	70	(1)
Summary	70	(5)
Level Measurement	75	(20)
Definition of Level	75	(1)
Devices for Measuring Level	76	(12)
The Buoyancy Sensor	76	(1)
The Float-Actuated Sensor	77	(2)
The Capacitance Level Sensor	79	(1)
The Differential-Pressure Cell as a Level Sensor	80	(3)
The Ultrasonic Level Sensor	83	(1)
The Radar Level Sensor	84	(1)
Level Switches	84	(1)
The Radiometric (Radioactive Source) Level Sensor	85	(1)
The Hydrostatic Tank Gauge (HTG)	86	(1)
Applications of the Hydrostatic Tank Gauge	87	(1)
Data Required to Provide a Measurement of Process Level	88	(1)
Process Fluid	88	(1)
Process Parameters	88	(1)
Physical Location	88	(1)
Application	89	(1)
Criteria for Selecting a Suitable Level-Measuring Instrument	89	(1)
Operating Range	89	(1)
Sensing Elements	89	(1)
Aggressive Fluids	90	(1)
Materials of Construction	90	(1)
Chemical Seals	90	(1)
Summary	90	(5)
Analytical Measurements	95	(30)
Chemical Analysis in Process Control	95	(1)
Hydrogen Ion Concentration or pH	96	(5)
Atoms and Ions	96	(1)
The Normality of Solutions	96	(1)
Theory of Electrolytic Dissociation	97	(1)
Electrolysis	98	(2)
The pH Scale	100	(1)
Measuring pH	101	(2)
The Standard Hydrogen Reference Electrode	101	(1)
The pH Electrode	101	(2)
Conductivity of Liquids	103	(1)
Measuring Conductivity	103	(1)
Chromatography	104	(7)
The Katharometer	105	(1)
The Ultrasonic Detector	106	(1)
The Pellistor Detector	107	(1)
The Paramagnetic Oxygen Analyzer	108	(1)
Instrument Construction	108	(1)
Working Principle of the Paramagnetic Oxygen Analyzer	109	(1)
The Nondispersive Infrared (NDIR) Gas Analyzer	110	(1)
Data Required to Provide an Analytical Measurement in a Process	111	(2)
Process Fluid	112	(1)
Process Parameters	112	(1)
Physical Location	113	(1)
Application	113	(1)
Criteria for Selecting a Suitable Analytical Measuring Instrument	113	(1)
Type of Measurement Required	113	(1)
Operating Range	114	(1)
Aggressive Fluids	114	(1)
Materials of Construction	114	(1)
Summary	114	(11)
Appendix	118	(3)
Problems	121	(4)
Part II PROCESS CONTROL	125	(66)
Gain	127	(12)
Basic Elements of a Controller	127	(1)
Basic Elements of Control	128	(2)
Relationship Between Gain and Feedback	130	(3)
Gain of a Combination of Units	133	(2)
Negative Feedback Application Example	135	(1)
Summary	136	(3)
Delays or ``Lags''	139	(10)
Lags Associated with Control	139	(4)
Measurement Lags	139	(1)
Distance/Velocity Lags	140	(2)
Transfer Lags	142	(1)
Example 7.1	143	(1)
Example 7.2	144	(2)
Summary	146	(3)
Control Actions	149	(14)
A Practical Three-Term Process Controller	149	(1)
Basic (Simpler) Controller Actions	150	(2)
On-Off Action (The Simplest)	150	(1)
Multistep Actions	151	(1)
Floating Actions	152	(1)
Mathematical Functions Used in Automatic Process Controllers	152	(5)
Proportional Control Action	154	(1)
Integral Control Action	155	(1)
Derivative Control Action	156	(1)
Combining the Basic Controller Equations	156	(1)
Proportional Band of a Controller	157	(1)
Summary	158	(5)
Control Equations	163	(14)
Processing a Signal Within a Controller	163	(2)
At the Input	163	(1)
At the Comparator	164	(1)
At the Control Unit	164	(1)
At the Output	165	(1)
Illustrations of Typical Process Controller Actions	165	(7)
Proportional Action	165	(2)
Integral Action	167	(2)
Proportional Plus Integral Action	169	(1)
Proportional Plus Integral Plus Derivative Action	170	(1)
Integral Saturation or Windup	171	(1)
Summary	172	(5)
Controller Tuning	177	(14)
Control Term Interaction in a Three-Term Controller	177	(2)
Methods of Loop and Controller Tuning	179	(8)
The Frequency Response Method	180	(1)
Alternative Tests to Obtain Plant Data	180	(4)
Ziegler-Nichols Method	184	(2)
A Practical Methodology for Control Loop Tuning	186	(1)
Summary	187	(4)
Part III APPLICATIONS	191	(96)
Flow, Pressure and Level Control	193	(10)
Flow	193	(3)
Pressure	196	(2)
Level	198	(2)
Summary	200	(3)
Control of a Stirred Reactor and Product Composition	203	(8)
A Reaction Process	203	(1)
Control of Temperature	204	(3)
Illustration: Control of a Stirred Reactor	204	(3)
Control of a Mixing Process	207	(2)
Summary	209	(2)
Surge Control of Centrifugal Compressors	211	(28)
Introduction to Centrifugal Compressors	211	(6)
Surge in Centrifugal Compressors	211	(1)
Operating Range of a Centrifugal Compressor	212	(1)
Theory of Compression	213	(1)
Inherent Instability of Centrifugal Compressors	214	(1)
The Search for a Solution---Fluid Mechanics of Compressors	214	(3)
Linear Method of Compressor Control	217	(11)
The Batch Action Controller	224	(1)
Enhancing the Basic Linear Control Scheme for Gas Temperature Variation	225	(3)
Nonlinear Methods of Control---Compressors with Inlet Guide Vanes	228	(1)
The Asymmetric Controller	229	(1)
Multiple Compressor Configurations	230	(3)
Compressors in Series	230	(1)
Compressors in Parallel	231	(2)
Summary	233	(6)
Control of Steam Generation Plant	239	(30)
Introduction to Steam Generators (Boilers)	239	(1)
Principles of Steam Generation---A Review	239	(2)
The Steam Generator or Boiler	241	(2)
General Description of the Process Plant	243	(1)
Plant Operation	244	(1)
The Control System	245	(19)
Water and Steam Circuit	246	(1)
Turndown	246	(1)
Steam Drum Level---(``Drum Level Control'')	247	(1)
Three-Element Feedwater Control	248	(1)
Real-System Behavior	249	(1)
Single-Element Feedwater Control	249	(1)
Two-Element Feedwater Control	249	(1)
Fuel and Air Circuit	250	(1)
Fuel Combustion	250	(3)
Master Pressure Control	253	(2)
Multiple-Fuel Firing Systems	255	(1)
Preferential Fuel Firing	256	(1)
Control Valve Rangeability	257	(2)
Fuel and Air Cross Limiting and Oxygen Trim of Combustion Controls	259	(1)
Combustion of Additional Elements in the Fuel	260	(1)
Combustion Air Temperature Control	261	(2)
Furnace Pressure Regulation	263	(1)
The Complete Control System	263	(1)
Fuels	264	(1)
General Topics	264	(1)
Summary	264	(5)
Process Dryers	269	(18)
Introduction to Process Drying	269	(5)
Principles of Solids Drying	269	(1)
Some Basic Definitions	270	(1)
The Wet- and Dry-Bulb Hygrometer	270	(1)
Visualizing the Drying Process	271	(3)
Psychrometry	274	(1)
Pulp Product Drying in the Food-Processing Industry	275	(2)
Process Drying Equipment	277	(3)
Batch-Type Dryers	277	(1)
Fluidized-Bed Dryers	277	(1)
Air-Lift Dryers	277	(1)
Spray Dryers	278	(1)
Longitudinal-Type Dryers	278	(1)
The Steam-Tube Dryer	278	(1)
Dryer Operation	279	(1)
The Control System	280	(2)
Analysis of the Fluidized Bed Dryer	282	(1)
Operation	282	(1)
The Control System	282	(1)
Summary	283	(4)
Part IV FINAL CONTROL DEVICES	287	(48)
Control Valves	289	(28)
The Need for Good Process Plant Design	289	(1)
Description of a Typical Industrial Control Valve	290	(4)
The Body	290	(1)
Connections	290	(1)
Plug	291	(1)
Stem	291	(1)
Seat	291	(1)
Yoke	292	(1)
Actuator Stem	292	(1)
Actuator Spring	292	(1)
Actuator	293	(1)
Stem Connector	294	(1)
Valve Types	294	(4)
Rotary-Plug Valve	294	(1)
Butterfly Valve	295	(1)
Ball-Type Valve	296	(1)
Diaphragm-Type Valve	297	(1)
Valve Characteristics	298	(2)
Valve Porting	299	(1)
Control Valve Sizing	300	(6)
Sizing Equations Offered by Various Valve Manufacturers	301	(1)
Fisher-Rosemount	301	(1)
The Foxboro Company	302	(1)
Worcester Controls (Ball-Type Control Valves)	303	(2)
Masoneilan	305	(1)
Cavitation, Flashing and Rangeability of Control Valves	306	(2)
Pressure Drop Across a Control Valve	308	(2)
Some Reasons for Control Valve Failure and Methods to Overcome Them	310	(1)
Using Variable-Speed Pumps in Place of Control Valves	311	(1)
Are Positioners Necessary with Every Control Valve?	312	(1)
Electrical Control Valve Actuators	313	(1)
Summary	313	(4)
Power Cylinders and Control Drives	317	(18)
The Power Cylinder	317	(7)
Pneumatic Actuation	317	(1)
Hydraulic Actuation	318	(1)
Electrohydraulic Systems	318	(1)
Method of Operation---The Skil 416/7 Actuator	319	(2)
Pumps	321	(1)
Details of the Hydraulic Actuators	321	(3)
Pneumatic Systems	324	(1)
Links and Levers	324	(1)
Control Drives	324	(1)
Mounting Pneumatic Power Cylinders	325	(1)
Heavy Electrical Motor-Driven Actuators	325	(7)
Example: The Rotork Actuator	325	(4)
Cabling and Fusing	329	(1)
Typical Actuator Specification	329	(3)
Summary	332	(3)
Part V INSTALLATION OF INSTRUMENTATION	335	(18)
Considerations in Proper Installation	337	(16)
General Cautions	337	(1)
Installing Flow Devices	338	(5)
Straight Pipe Runs	338	(1)
Minimizing Process Noise	338	(1)
Orifice Plate Installations	339	(1)
Valve Manifolds Used on Differential-Pressure Installations	339	(1)
Requirements for Impulse Lines	340	(2)
Equalizing Static Pressure Heads	342	(1)
Sequences Necessary When Operating a Three-Valve Manifold	342	(1)
Installing a Coriolis Flowmeter	343	(1)
Installing a Magnetic Flowmeter	343	(1)
Installing Pressure Devices	343	(1)
Need for Consistent Engineering Units	343	(1)
Use of a Snubber	343	(1)
Compound-Range Instruments	344	(1)
Measuring Differential Pressure between Widely Separated Points	344	(1)
Installing Temperature Devices	344	(2)
Use of Thermowells	344	(1)
Installations with Thermocouples	345	(1)
Installing Level Devices	346	(1)
Necessary Transmitters	346	(1)
Precautions in Measuring Level	347	(1)
Installing Analytical Devices	347	(1)
Tips on Control Applications	348	(2)
Split Ranging	348	(1)
Compensating Flow Measurements for Pressure and Temperature Variations	349	(1)
Avoiding Difficulties in Tuning	349	(1)
Summary	350	(3)
Part VI MODERN CONTROL SYSTEMS	353	(166)
Distributed Control Systems (DCS)	355	(30)
Development of Modern Control Systems	355	(4)
The Early Years: The First Control Devices	355	(1)
Continued Development: The Age of Pneumatics	356	(1)
The Motive Power: The Air Supply	356	(1)
Further Development: The Electronics Age	357	(2)
Split-Architecture Control Systems: The Forerunner of DCS	359	(5)
A Typical Real Split-Architecture System	359	(2)
Drawbacks of Analog Systems	361	(1)
Addition of Digital Components to the Split-Architecture System	362	(1)
Breakdown of the Process into Manageable Segments	363	(1)
The First True Digital Control Systems	364	(2)
Multiple-Processor Systems: The Need for Standard Communications	366	(2)
Topologies of Representative DCSs	368	(4)
Operation of a Typical DCS	372	(5)
A Typical Control Loop	372	(3)
Process Alarming	375	(2)
Progressive Trends in DCS Technology	377	(2)
Ease of Data Manipulation: Microsoft Windows NT	377	(1)
The Fieldbus Concept	378	(1)
Summary	379	(6)
Implementing Control Schemes with a DCS	385	(26)
Introduction: Using the Foxboro I/A Series to Illustrate Design of a Control Scheme	385	(1)
Control Schemes	385	(5)
Diagrammatic Representation of a Flow Control Scheme	386	(1)
SAMA Method	386	(3)
The ISA Method	389	(1)
FoxCAE Method	389	(1)
Typical Data Requirement for a single Input to a DCS	390	(4)
Specimen of Data for an Analog Input	390	(4)
Block Diagram of the AIN Block	394	(1)
Further Development of the Flow Control Scheme for Delivery of a Metered Quantity	394	(3)
The ``Standard'' Control Block	397	(1)
The ``Enhanced'' Control Block: Inclusion of Adaptive Control	398	(3)
Further Development of the Scheme to Include Flow Ratio Control	401	(4)
Automatic/Manual Transfer---The Implications	403	(2)
Block Types Available on the I/A Series System	405	(3)
Summary	408	(3)
Communications, Signal Processing, and Data Handling	411	(26)
The Need for a Standard Protocol	411	(4)
Development of MAP and TOP	411	(1)
The Process Industry Scenario	412	(1)
The Commercial Scenario	413	(1)
The Protocols	413	(1)
Token Passing	414	(1)
Collision Detection	414	(1)
The Open-System Interconnection Model (ISO Seven-Layer Model)	415	(5)
The Physical Layer	415	(1)
The Data Link Layer	416	(1)
The Network Layer	417	(1)
The Transport Layer	417	(1)
The Sessions Layer	417	(1)
The Presentation Layer	418	(1)
The Applications Layer	418	(2)
Packet Switching	420	(2)
Signal Processing	422	(4)
Frequency-Shift Keying	422	(1)
Field/Process Signals	422	(1)
Analog-to-Digital Converters	423	(1)
Multiplexing	424	(1)
Amplitude Modulation	425	(1)
Phase-Shift Keying	426	(1)
Signal Conditioning Using Operational Amplifiers	426	(4)
Summary	430	(7)
Electrical Safety: Power and Grounding	437	(20)
The Basis of Electrical Safety Design	437	(1)
Approaches to Safety Design	437	(1)
Explosion- versus Flameproof	438	(1)
Bodies Responsible for Safety in Europe and the United States: Comparison of Standards	438	(4)
Locations or Areas	439	(1)
Operational Categories for Equipment	439	(1)
Gas Classification	440	(1)
Temperature Classification	440	(1)
A Typical Intrinsically Safe Loop	440	(1)
Simple Apparatus	441	(1)
Process Plant Cabling Requirements	441	(1)
Shunt Diode Barriers	441	(1)
Categories of Interfaces: Zener Barriers and Galvanic Isolators	442	(1)
The Zener Barrier	442	(1)
The Galvanic Isolator	442	(1)
Comparison between the Zener Barrier and Galvanic Isolator	443	(1)
Installation of Intrinsically Safe Cabling and Equipment	443	(4)
Conductors and Cables	443	(2)
Wiring Connection Terminals	445	(1)
Cable L/r Ratio	445	(2)
Plant Grounding	447	(4)
Common-Mode Voltage	448	(1)
Earth Currents	449	(1)
The Use of Isolation Transformers	450	(1)
UK Requirements	451	(1)
Typical Power and Grounding Arrangement for an Instrumentation System	451	(1)
Summary	452	(5)
Process Alarm Systems	457	(18)
The Philosophy Behind Process Alarming	457	(1)
Process Alarm Setting	458	(1)
Process Alarm Initiation	459	(4)
Two-Wire Transmission Circuits	459	(2)
Setting the Alarm Trips	461	(2)
Visualizing the Alarm Condition via a Process Alarm Annunciator	463	(3)
The Alarm Annunciator	465	(1)
DCS Process Alarm Systems	466	(3)
Emergency Shutdown Systems (ESDSs)	469	(2)
Summary	471	(4)
Boolean Logic	475	(24)
Numerical Representation in Electrical Form	475	(2)
Conversion of One System to Another	477	(1)
Binary to Decimal Conversion	477	(1)
Decimal to Binary Conversion	477	(1)
Logic Blocks	477	(2)
Definitions of the Logic Functions	478	(1)
Algebraic Symbols for the Logic Functions	479	(1)
Truth Tables	479	(4)
Constructing a Truth Table	479	(1)
Basic Operations	480	(1)
Conventions in Boolean Algebra	481	(2)
De Morgan's Theorem	483	(1)
Minimization Methods	483	(9)
Algebraic Minimization: The Quine-McCluskey Method	483	(4)
Graphic Minimization: The Karnaugh Map	487	(4)
The Don't Care Situation	491	(1)
Other Logic Functions	492	(1)
Relay Logic Systems	492	(3)
Structure of a Relay	493	(1)
The Relay as a Boolean Device	493	(1)
A Typical Motor Start/Stop Circuit	494	(1)
Summary	495	(4)
Sequential Logic	499	(20)
Continuous Versus Batch (Sequential) Processes	499	(1)
A Typical Batch (Sequential) Operation	499	(7)
The Starting Point of a Batch Control Scheme	499	(1)
The Process Analysis	499	(1)
Design Considerations---``Inerting''	500	(1)
Product Ingredient Addition	501	(1)
Product Processing	501	(1)
Compliance Testing of Product During Manufacture	502	(1)
Product Processing---Continued	503	(1)
Wash Cycle and Solvent Recovery	503	(1)
Second Reactor Product Processing	503	(1)
Process Line-Pigging Operation	504	(2)
The Namur Standard for Batch Operations	506	(1)
Specifying a Batch Operation: Grafcet	507	(6)
The Primitives	507	(3)
Sequences	510	(1)
Syntax and the Rules of Evolution	511	(2)
The Continuous Control Aspects of a Batch Control Operation	513	(2)
Summary	515	(4)
Bibliography	519	(2)
Index	521