Performance Objective
...................................................... 1
The Importance of Process Control
........................................ 1
Learning
Objectives.......................................................... 1
The Importance of Process
Control.......................................... 2
Process....... 2
Process Control
................................................................ 2
Reduce Variability
...................................................... 2
Increase Efficiency
..................................................... 3
Ensure Safety
............................................................. 3
Control Theory Basics ............................................................
4
Learning
Objectives.......................................................... 4
The Control
Loop..................................................................... 5
Three Tasks.......................................................................5
Process Control Terms
............................................................6
Process
Variable...............................................................6
Setpoint ......6
Measured Variables, Process Variables, and Manipulated
Variables.....................................................7
Error ..........7
Offset..........8
Load Disturbance
.............................................................8
Control Algorithm.............................................................8
Manual and Automatic Control
.........................................9
Closed and Open Control Loops
.......................................10
Components of Control Loops and ISA Symbology
............... 11
Learning
Objectives.......................................................... 11
Control Loop Equipment and
Technology................................ 12
Primary
Elements/Sensors................................................. 12
Transducers and Converters..............................................
13
Transmitters......................................................................
13
Signals ....... 14
Pneumatic Signals
...................................................... 14
Analog Signals...........................................................
14
Digital Signals
........................................................... 15
Indicators... 15
Recorders... 16
Controllers........................................................................
16
Correcting Elements/Final Control Elements
................... 18
Actuators.... 18
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Table of Contents
iii Fundamentals of Control
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ISA Symbology ..19
Symbols .... 20
Pumps ......................................................................
21
Piping and Connections
........................................... 22
Identification
Letters....................................................... 23
Tag
Numbers................................................................... 23
ISA Symbology Review
.................................................... 26
Controller Algorithms and Tuning
........................................27
Learning
Objectives.........................................................27
Controller Algorithms.............................................................28
Discrete Controllers
........................................................28
Multistep
Controllers........................................................29
Continuous Controllers .....................................................29
Why controllers need
tuning?...................................................31
Gain ...........31
Proportional Mode
..................................................................33
Proportional Gain ............................................................33
Proportional
Band............................................................33
Limits of Proportional action
............................................34
Determining the Controller Output...................................34
Proportional Action- Closed
Loop.................................... 35 .
Integral Mode .. 37
Integral
Action................................................................ 37
Open Loop Analysis........................................................
37
Closed Loop Analysis
...................................................... 38
Reset Windup
.................................................................. 39
Summary .. 40
Derivative Mode ......................................................................
41
Derivative
Action............................................................ 41
Rate
Summary................................................................. 44
Process Control Loops.............................................................46
Learning
Objectives..........................................................46
Single Control Loops
...............................................................47
Feedback Control .............................................................47
Examples Of Single Control
Loops...........................................48
Pressure Control
Loops....................................................49
Flow Control
Loops..........................................................49
Level Control Loops
.........................................................50
Temperature Control Loops
..............................................51
