CHEM-E7140 - Process Automation
Lecture 1: Introductory concepts of process
control, introduction to control system
implementation
Contents
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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
Introduction to process automation
• Process automation is used to optimize processes and
plants economically and environmentally by utilizing
information collected from a plant
Introduction to process automation
• 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
Information is
refined and its
amount decreases
Number of functions and
degree of time citicalness
increases
Process management
Process control
Measurements and actuators
© Knowpap2004
Contents
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Introduction to process automation
Benefits of process automation
Main Functions of the Process Automation Systems
Systems Architecture
Open system
Instrumentation and Communications
Field bus
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
Benefits of process automation
• The financial benefit of an automated process comes
from more efficient operation of processes and from
financial optimization
Benefits of process automation
• improvement gained in a product’s quality with
computerized control and on-line analysis
Benefits of process automation
• 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
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
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Collection of measurement data
Process control
Process management
Process monitoring and supervising
Main Functions of the Process Automation
Systems: Supporting functions are
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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
– Distributed Control Systems
– Programmable Logic Controller-based Automation System
• Open system
• Instrumentation and Communications
• Field bus
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
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Introduction to process automation
Benefits of process automation
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
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.
Distributed Control Systems
• The most crucial stations of the DCS are:
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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
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
Process station where an advanced control is handled by PC
Basic control
Advanced control
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’ positionspecific 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
Information processing
Operation terminal
Display
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: Specialpurpose 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: Specialpurpose 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: Specialpurpose 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
Information processing
Database
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
– Distributed Control Systems
– Programmable Logic Controller-based Automation System
• Open system
• Instrumentation and Communications
• Field bus
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
Programmable Logic Controllers
• PLC programming languages (IEC 61131-3)
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Ladder Logic (LL)
Instruction List (IL)
Function Block Diagram (FBD)
Structured Text (ST)
Sequential Flow Chart (SFC)
Programmable Logic Controllers
• 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
Programmable Logic Controllers
• 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
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Introduction to process automation
Benefits of process automation
Main Functions of the Process Automation Systems
Systems Architecture
Open system
Instrumentation and Communications
Field bus
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
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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
feed
measurement
Process
station
Cabling
Instrumentation and Communications:
Collection and processing of measurement data
• Basic measurements of process industry are
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Temperature
Pressure
Flow
Level
• Measuring of material properties
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Density
Moisture
pH
Conductivity
Instrumentation and Communications:
Collection and processing of measurement data
• A measurement system consists of the following parts
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Sampler, measurement sensor
Measurement converter and transmitter
Cabling to an I/O card
Analog-to-digital converter and data preprocessing
Instrumentation and Communications:
Collection and processing of measurement data
• 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
Instrumentation and Communications:
Collection and processing of measurement data
• 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
Instrumentation and Communications:
Collection and processing of measurement data
Prohibus DP
AC 800 CM -controller
Transmitter and
field box
Cross-connection
box
Cross-connections
I/O
(analog
measurements)
Prohibus PA
Instrumentation and Communications:
Collection and processing of measurement data
• 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:
Collection and processing of measurement data
Instrumentation and Communications:
Collection and processing of measurement data
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
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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
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Introduction to process automation
Benefits of process automation
Main Functions of the Process Automation Systems
Systems Architecture
Open system
Instrumentation and Communications
Field bus
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:
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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
Fieldbus
Aalto / KM / BK / Process control – Automation system
Engineering
Workspace
2-5
Firewall
& Router
Plant and Control Network (TCP/IP)
History Server
or (Product
management
server CPM+)
Combined
Aspect and
Connectivity
Server
Engineering
Workplace 1
Plant and Control Network (TCP/IP)
FF HSE
Flotation Cell
FF H1
Heat Exchanger
ProfiNET
1 - tank
Profibus
DP
Profibus
PA