apc pdf

BKF 3843 & PROCESS CONTROL

INSTRUMENTATION

:By Junaidi Bin

Zakaria, FKKSA UMP

JUNAIDI BIN ZAKARIA A3-2-9

013-9683471/09-5492914 [email protected]

ASSESSMENT METHOD

TEST 1 20%TEST 2 20%QUIZZES 10%ASSIGNMENTS 10%FINAL EXAM 40%

TOTAL 100%

CHAPTER REVIEW

CHAPTER 1

Introduction to Process Control

:By Junaidi Bin

Zakaria, FKKSA UMP

TaskIn your own words, - what is process control &

instrumentation - explain the importance of process

control

Learning ObjectivesDescribe the importance process controlDefine and identify controlled, manipulated

variables and disturbance for a given process

Explain the implementation of process control in industries

Explain feedback and feedforward control

When I run a kinetics experiment, how do I maintain the temperature and level at desired values?

How do I manufacture products with consistently high quality when raw material properties change?

How much time do I have to respond to a dangerous situation?

Why do I learn Process Control and Instrumentation Course

Why Is Control Necessary?

Control SystemProcess control principle

How to keep the level at

desired value, H?

h

Qin

Qout

H

Control SystemProcess control principle

Human Aided ControlThe equipment has

the local gauge/ side tube

Controlled variable-liquid level

Manipulated variable-valve

What will cause the level high/ low?

Qin

h

Qout

H

Control SystemProcess control principle

Automatic controlMachine, electronic, or

computer replace human operation

h

Qout

Controller

Actuator

Sensors

u

Qin

Categories of control systems1. Servomechanisms – change an output

variable2. Regulators – hold an output variable

Most chemical process are regulators, eg. Feedback and Feedforward

16

What is control? Control

To maintain desired conditions in a physical system by adjusting selected .variables in the system

Control System

The control systems appear to have three basic elements which is

FINALELEMENTCONTROLLERSENSOR

17

SENSOR

- The first task that of acquiring information about the process output.variables

- Sensors are usually needed for pressure , , temperature , liquid level flow

.and composition measurement-thermocouple: temperature measurement- differential pressure cell: for liquid level measurements- / gas liquid chromatographs: composition measurements

CONTROLLER

- , ‘ ’ The decision maker and hence the heart of the control system

FINALELEMENT

- , , , Pump variable speed fans compressor conveyors

Transmitter : How process information acquired by the sensor get back to , the controller and the controller decision gets back to the process

18

Process

Controller

OUTPUT

sensorFinal control element

INFORMATION

Transmitter

Transmitter

INPUT

Decision

DISTURBANCE

The feedback control configuration

Control Terminology

Controlled variables - these are the variables which quantify the performance or quality of the final product, which are also called output variables.

Manipulated variables - these input variables are adjusted dynamically to keep the controlled variables at their set-points.

Disturbance variables - these are also called "load" variables and represent input variables that can cause the controlled variables to deviate from their respective set points.

Ch

ap

ter

1

Task 1You are implementing control manually

Task 2State your own objective for this chemical

reactor.List the controlled, manipulated variables

and disturbance(s)

Answer for Task 2Level and Temperature Control

LC

TC

Answer for Task 2Composition Control

AC

JIGSAW

Classification of process control strategies

28

General Form of Control System Configuration

Structure of Open-loop System (struktur bg sistem gelung terbuka)

PROCESS

Disturbances variable

Manipulated variableControlled variable

29

FEEDBACK

Uses direct measurements of the controlled variables to adjust the values of the manipulated variables.

FEEDFORWARD

Uses direct measurements of the disturbances variables to adjust the values of the manipulated variables.

Method 1

Method 2

35

Process

Disturbances variable

Manipulatedvariable Controlled

variable

controller

Process

Disturbances variable

Manipulatedvariable

Controlledvariable

controller

§It does not required identification and measurement of any disturbance.§It is not sensitive to modeling errors.§It is not sensitive to parameter changes.

Advantages

Disadvantages

§Acts before the effects of a disturbances has been felt by the system§Is good for slow systems or with significant dead time§It does not introduce instability in the closed-loop response

§It wait until the effect of the disturbances has been felt by the system§It is unsatisfactory for slow processes§It may create instability in the close-loop response

§Required identification & measurement of disturbances§Cannot cope with unmeasured disturbance§Sensitive to process parameter variations§Requires good knowledge of the process control

Feed Back Feed Forward

36

Instrumentation Symbols

Symbols of instruments used in :process controls drawings

A : AnalyzerF : Flow rateL : Level of liquid or solids in a vesselP : PressureT : TemperatureC : ControllerV : Valve

1. Measurement and Actuation

2. Safety, Environment and Equipment

Protection

3a. Regulatory Control

4. Real-Time Optimization

5. Planning and Scheduling

Process

3b. Multivariable and Constraint

Control

(days-months )

(< 1 Second )

(< 1 second )

( seconds-minutes )

( minutes-hours )

( hours-days )

Case Study

Case 1: High pressure is dangerous. Case 2: No flow could damage the pumpCase 3: High temperature may cause

thermal loading in the columnCase 4: Quality of product at the bottom

column is the most criticalCase 5: Keep the process at smooth rate,

avoid dry column

Case 1

Case 2

Case 3

High thermal loading

TC

Case 4Adjusting the heating and flowrate

Case 5

THANK YOU