CHEM-E7140 - Process Automation Lecture 1: Introductory concepts of process control, introduction to...

CHEM-E7140 - Process Automation

Lecture 1: Introductory concepts of process control, introduction to control system implementation

Contents

• Introduction to process automation• Benefits of process automation• Main Functions of the Process Automation Systems• Systems Architecture• Open system• Instrumentation and Communications• Field bus

Introduction to process automation

• Process automation system allows optimal control of the process by utilizing equipment such as measuring and actuators devices of the process automation system. Automatic information processing between these devices and information channels

• The control system of the process is connected to process instrumentation through the process interface

• Process interface transfers all the required information from the process to the system and the system’s control information to the process

• The graphical interface provides the users, with the processed data from the process and the users’ actions to the systems, for further processing


• Process automation is used to optimize processes and plants economically and environmentally by utilizing information collected from a plant


• Process automation– Stands for the production and process related gathering,

transfer, processing and storage of information

• Process management systems– Include all the tools and procedures, which help the personnel

to operate a plant or a process in the desired way

• Besides process control, parts of the production and quality control related functions are automated and integrated into a plant’s information and automation system

Automation hierarchy

© Knowpap2004

Information isrefined and its

amount decreases

Number of functions anddegree of time citicalness

increases

Measurements and actuators

Process control

Process management

Contents


Benefits of process automation

• Less shutdowns and breaks in the production• Raw-material and chemical savings stem from more

precise control of the process, typically via lowered chemical feeds

• More flexible production• The level of environmental discharges has decreased

due to reduction of the excess of chemicals and, for example, due to better controlled burning processes


• The financial benefit of an automated process comes from more efficient operation of processes and from financial optimization


• improvement gained in a product’s quality with computerized control and on-line analysis


• A decrease in quality variance can be seen• after on-line control has been applied to the system

Contents

• Introduction• Main Functions of the Process Automation Systems• Systems Architecture

– Distributed Control Systems– Programmable Logic Controller-based Automation System

• Open system• Instrumentation and Communications• Field bus

Main Functions of the Process Automation Systems

Main Functions of the Process Automation Systems• An automation systems’ function can be roughly divided

into: – basic functions– The basic system’s supporting functions

Main Functions of the Process Automation Systems: Basic functions• Collection of measurement data• Process control• Process management• Process monitoring and supervising

Main Functions of the Process Automation Systems: Supporting functions are• Data collection and reporting• Self diagnostics• Configuration of application and systems maintenance• Bus interfaces (serial buses to analyzers, control logics

of a single device and parallel automation systems as well as information systems)

Contents

• Introduction to process automation• Benefits of process automation• Main Functions of the Process Automation Systems• Systems Architecture



Systems Architecture

– Relay, timers• Robust and fast (usually used for safety circuits)

– Basic control• Yksittäisten säätöpiirien toteutus

– Distributed Control System (DCS)• Extensive / demanding process control tasks

– Programmable Logic Controller (PLC)• Programmable Logic Controller was created at first, to replace relay

and switch-based logic systems in the retailing industry• PLCs have become more common in DCD systems due to the

development of technology and increasing calculation speed of microprocessors

Contents

• Introduction to process automation• Benefits of process automation• Main Functions of the Process Automation Systems• Systems Architecture



Distributed Control Systems

• DCS systems are based on separated units, which have their own processor. Those units are usually called stations; stations are connected together by a bus.

• Today, lower-level controls are carried out by a microprocessor equipped with a memory controller and advanced controls are carried out, for example, with a PC.


• The most crucial stations of the DCS are:– Process station– Control room station– Application/configuration station– Different special-purpose stations

• Data collection and reporting stations• Bus station• Alarm station

– Networks and bus solutions

Distributed Control Systems: Process station• The process station is the most critical level of the

automation system (works independently from other stations)

• The process station runs the process interface:– Measurement data collecting and processing ( for example,

scaling and alarm generating)– Controls and locks the actuators as well as takes care of group

start-up and sequence control

Distributed Control Systems: Process station• Process stations’ functions:

– Connections to motor logics and to other process and control stations

Distributed Control Systems: Process station

Advanced controlBasic control

Process station where an advanced control is handled by PC

Distributed Control Systems: Control or operation station• The control or operation station’s function is to support

an operator’s work by, giving him or her, a clear general picture of the process and to provide good conditions for flawless work.

• Operation station functions:– Process diagrams, measurements’ and controls’ position-

specific monitors– Alarm, sequence and trend monitors– Process operations

Distributed Control Systems: Control or operation station• The operations terminal’s devices

– Frame, Power source, (CPU), memory unit, interface cards to system bus (can be implemented also with PC)

– Display and operation station

Distributed Control Systems: Control or operation station

Distributed Control Systems: Control or operation station

DisplayOperation terminal

Information processing

Distributed Control Systems: Special-purpose stations - The interface/connecting station

• The interface/connecting station has connections to different information systems and to parallel automation systems– Practical implementation often requires the

application-specific programming

Distributed Control Systems: Special-purpose stations – Logging and reporting stations

• The logging and reporting station’s task, is to collect and store information. It also performs some computing and edits data to form a printable report

Distributed Control Systems: Special-purpose stations – Logging and reporting stations

• usually a separate computer (UNIX or MS Windows 2000 / 7)

• A lot of storage and possibility for back-ups (Tape drive)• Not necessarily included in the base system (sold as an

option)

Distributed Control Systems: Special-purpose stations – Alam station

• The alarms station’s task is, to take care of storage of the alarm and event history and additionally, for example, to control the alarm printers

DatabaseInformation processing

Distributed Control Systems: Special-purpose stations – Application and configuration station

• Application and configuration station are used for programming, changes, maintenance and documentation of automation application

Distributed Control Systems: Networks and bus solutions• Typically, process automation system’s bus solutions

can be divided in three layers– Field bus,– System bus– Plant bus

Distributed Control Systems: Networks and bus solutions• Field bus

– Connects i/o-frames to process stations– 500 m long, 1 Mbit/s (128kBytes/s)

• System bus– Connects process, control room and specific control stations of

the same department together– 2 km coaxial cable (optical cable), 2 Mbit/s

Distributed Control Systems: Networks and bus solutions• Plant bus

– Connects departments together and to plant-level workstations– 10-100 Mbit/s

Distributed Control Systems: Networks and bus solutions

Contents

• Introduction• Main Functions of the Process Automation Systems• Systems Architecture



Programmable Logic Controllers

• A PLC is a microprocessor-based technology and is capable of processing measured data according to the programmed setting and program-like rules and multiple PLCs may be present in the same process

• PLC-system has its software configured for each controlled process, to meet its requirements. Configuration, in this particular case, means programming

• The number of PLCs depends on the distribution level and complexity of the system


• PLC programming languages (IEC 61131-3)– Ladder Logic (LL)– Instruction List (IL)– Function Block Diagram (FBD)– Structured Text (ST)– Sequential Flow Chart (SFC)


• Recently, PLCs have become more common due to the development of technology and increasing calculation speed of microprocessors– New functionality has been added to programmable logic

controllers

• PLC manufacturers have also developed PLC programming tools more efficient and accessible– More versatile control solutionst


• A “Soft-PLC” solution is an ordinary PC, with specialized software installed on it, which performs all calculations and logical operations.

• It also has an interface card so it can be connected to a plant’s instrumentation components.

Contents


Open System

• Open architecture makes it possible to build a system by combining devices of different manufactures– Customer may pick the best software or hardware supplier for

different parts of its automation system

• The architecture of an automation system is layered, where details of one layer are hidden from the others by using standard application protocol interfaces (API)

• Systems with an open architecture have three common properties:– Portability– Joint use– Capability of integration

Open System

Contents

• Introduction• Main Functions of the Process Automation Systems• Systems Architecture• Open system• Instrumentation and Communications• Field bus

Instrumentation and Communications

• Measurement technology is a very important part of a plant’s automation

• To keep a process constantly under control it’s important to measure the process’s state in real time when possible, in other words, to collect data from the process

Instrumentation and Communications

Cabling

measurement

Processstation

feed

Instrumentation and Communications: Collection and processing of measurement data

• Basic measurements of process industry are– Temperature– Pressure– Flow– Level

• Measuring of material properties– Density– Moisture– pH– Conductivity


• A measurement system consists of the following parts– Sampler, measurement sensor– Measurement converter and transmitter– Cabling to an I/O card– Analog-to-digital converter and data preprocessing


• The sensor, converts the measured property to a property that can be detected.

• It generates a signal, proportional to the measured value by converting, for example– temperature to voltage– flow rate to pressure difference and

pressure difference to current


• Electrical magnitude is usually weak and must by strengthened with an amplifier

• The transmitter converts the signal to electrical standard messages– Pneumatic standard message (20-100kPa)– Electric analog message: potential message

(1-5 V DC or 2-10 V DC)– Electric analog message: current message

(4-20 mA DC)– Digital message

IInstrumentation and Communications: Collection and processing of measurement data

• Standard messages are sent to an I/O-card through cabling– Cabling is usually done in the following order

• From transmitter to field box• From field box to cross-connection box• From cross-connection box to I/O card


Prohibus PA

Prohibus DP AC 800 CM -controller

I/O(analogmeasurements)

Transmitter andfield box

Cross-connectionbox

Cross-connections


• At I/O card– The electrical signal is converted by an A/D-converter into digital

form (~quantisation)• Converting resolution is usually 12 or 16 bittiä

(accuracy 212 = 4096 tai 65536)

– Then the signal is filtered, scaled and converted into some engineering unit

Instrumentation and Communications: Actuator controls

• The signals used controlling the process have to be converted to analog form with a D/A –converter

• Then the signal in the form of a current message is sent to the field equipment.

• The actuators control consists of the following components:– Forming the control message format and a D / A conversion– Cabling of standard message to amplifier

• Structure of an actuator device– Servomotor– Transmission– Actuator– Various auxiliary equipment, such as positioners, limit switches, position

transmitters

Instrumentation and Communications : Actuator controls

• Actuators provide control / adjustment message proportional to the mechanical motion or force

• Actuators, for example. – Speed controlled pump– Control valves

Instrumentation and Communications : Interface to automation system

• Process connection is implemented with variety of interface cards– Analog input and output cards

• 1-16 kanavaa, 0/4-20 mA, 0-10 V

– Binary interfaces• 8-48 channels, 24 V-, 48 V-, 110 V-, 220V~

– Special cards, such as resistance sensor, thermometer,the interrupt input cards (5-10 ms), pulse counters

• Interfaces to analyzers and, for example, to Programmable logic controllers are implemented with separate interface cardsa

Instrumentation and Communications : Interface to automation system

Centralized I/O interface Distributed I/O interface

Contents


Fieldbus

• Fieldbus uses a digital data transmission

• Makes– possible to transfer information about many process variables

simultaneously– Fieldbus technology enables the transfer of multi-level diagnostic

information, thus making predictive maintenance possible– Two-way communication from automation systems to field

equipment makes it possible to perform maintenance operations such as confi guration and calibration tasks from a workstation

• Decreased startup and operating costs during the whole lifetime of a system

• Remote diagnostic properties of field equipment

Fieldbus

• International field bus standard includes eight different standard definitions:– Foundation Fieldbus– ControlNet– Profibus– P-Net– Fieldbus Foundation High Speed Ethernet– SwiftNet– WorldFIP ja– Interbus

• There are also many other standardized and manufacturer’s own solutions

Fieldbus

• Mainly two field bus solutions are competing for market share at the moment, the German-European Profibus and the Foundation Fieldbus developed by an international organization

• The basis for the Profibus technology is plant automation and programmable logics. In terms of a device bus solution there is Profibus DP, and as an instrumentation bus, Profibus PA

• Instrumentation bus-technology developed by Fieldbus Foundation (FF) is named H1 and the plant bus is a higher level HSE (High Speed Ethernet) based solution.

Fieldbus

Aalto / KM / BK / Process control – Automation system

Plant and Control Network (TCP/IP)

Flotation Cell

Engineering Workplace 1

History Server or (Product management server CPM+)

CombinedAspect and ConnectivityServer

FF H

SE

Engineering Workspace

2-5

FF H1

1 - tank

Profibus DP

Profibus PA

ProfiNET

Heat Exchanger

Plant and Control Network (TCP/IP)

Firewall& Router

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