Dcs course

Distributed Control System and Programmable Logic Control

Course Aim

The aim of this training course is to build up the procedural and
declarative knowledge required to be recognized by projects engineer that
don not have past background of DCS or PLC. This will help them to
supervise projects dealing with control systems with a strong background.
In this course, the training cycle is divided in five steps that necessitate
the cooperation between the instructor and the trainees. These steps are
shown in figure below, they are summarized as follows:
1. Define the knowledge and skills required to be developed.
2. Define the elements of each knowledge or skill.
3. Formulate a verbal phrase for the learning objective of each
element.
4. Choose an adequate instructional activity to present each element.
5. Set up an indicator to measure the outcomes of the course and
modify the training skills to adapt the vocational needs.

Define
Knowledge Determine
& Skills Elements

Measure Learning
& Correction Objectives

Instruction
Activity

Training Cycle.

1


Knowledge and Elements

 Illustrate DCS & PLC Benefits, Usage and History.
 Overview of control system history.
 Control system benefits and usage.
 Types of control

 Develop Knowledge of DCS Components (Hardware & Software).
 Infrastructure [Communication Bus, Interfaces, Controllers,
Gateways, RTU, Others].
 Hardware and technologies.
 Software [Configuration, Graphics, Alarming, Trending, System
Management, Others].

 Extend Knowledge of DCS installation and Maintenance.
 Site Installation, Commissioning and Startup.
 Diagnostics, Spares, Tools and Power Distribution.
 Maintenance [Backup, Replacements and System Installation].

 Develop Knowledge of PLC Components.
 PLC fundamentals.
 PLC Logic.

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Table of Contents

Section I
Chapter 1 Introduction
Chapter 2 Regulatory Control
Section II
Chapter 3 DCS Infrastructure
Chapter 4 DCS Hardware
Chapter 5 DCS Software
Section III
Chapter 6 Installation
Chapter 7 Maintenance
Chapter 8 Power Distribution
Section IV
Chapter 9 PLC Fundamentals.
Chapter 10 Ladder Logic And SFC

Appendices
A Electrical Relay Diagram And P&ID Symbols
B Serial Communication
C Networking
D Software Engineering

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4


Chapter 1
Control Systems

1.1 Automation System Structure

Although applications differ widely, there is little difference in the
overall architecture of their control systems. Why the control system of a
power plant is not sold also for automating a brewery depends largely on
small differences (e.g. explosion-proof), on regulations (e.g. Food and
Drug Administration) and also tradition, customer relationship.
The ANSI/ISA standard 95 defines terminology and good practices
Level
4 Business Planning & Logistics Enterprise Resource
Plant Production Scheduling Planning
Operational Management, etc.

Level Manufacturing
3 Operations & Control
Dispatching Production, Detailed Product Manufacturing Execution
Scheduling, Reliability Assurance,... System

Level
2,1,0
Batch Continuous Discrete Control & Command
Control Control Control System

1.1.1 Large Control System Hierarchy

 Administration: Production goals, planning
 Enterprise: Manages resources, workflow, coordinates activities of
different sites, quality supervision, maintenance, distribution and
planning.

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 Supervision: Supervision of the site, optimization, on-line
operations. Control room, Process Data Base, logging (open loop)
 Group (Area): Control of a well-defined part of the plant. closed
loop, except for intervention of an operator)
o Coordinates individual subgroups
o Adjusting set-points and parameters
o Commands several units as a whole
 Unit (Cell): Control (regulation, monitoring and protection) of a
small part of a group (closed loop except for maintenance).
o Measure: Sampling, scaling, processing, calibration.
o Control: regulation, set-points and parameters
o Command: sequencing, protection and interlocking
 Field: Sensors & Actors, data acquisition, digitalization, data
transmission, no processing except measurement correction and
built-in protection.

4 Planning, Statistics, Finances administration

3 Workflow, Resources, Interactions enterprise

SCADA supervision
Supervisory Supervisory
=
2
And Data
Control
Acquisition

Group Control

Unit Control
1
Field

Sensors T
& Actors A V

0 Primary
technology

Figure 1.1 Large control system hierarchy

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1.1.2 Response Time and Hierarchical Level

Planning ERP
Level (Enterprise Resource
Planning)

MES
Execution (Manufacturing
Level Execution System)

SCADA
(Supervisory Control
Supervisory and Data Acquisition)
Level
DCS
(Distributed
Control System)
Control
Level
PLC
(Programmable
Logic Controller)

ms seconds hours days weeks month years
Figure 1.2 Response Time And Hierarchical Level

1.2 What is DCS?

 A DCS is an integrated set of modules with distributed functions.
– Multi-loop controllers (10’s-100’s) that connect to field
devices
– Supervisory coordinating controllers
– Multi-loop operator stations and engineering stations
– Servers for system data management
– Control network for intercommunication
– External connections

7


Supervisory Operator
System Stations
Remote Users Controller
www Server
Engineering
Station

Remote
Server

Control Network

Multi-loop
Controller

Direct I/O Module

Other Industrial Devices

Figure 1.3 DCS Hierarchy

 A DCS, throughout the whole system, must provide:
– Performance: control must be faster than the process.
– Determinism: control must always take the same time.
– Fault tolerance: redundancy; must fail to a known state.
– Security: must have access restrictions/controls.

Even though performance, ease of use, and interoperability are key
evaluation criteria for any control system software package, the following
is intended to provide the manufacturing engineer with a concise list of
control system software evaluation criteria.
1. INTEROPERABILITY.
This refers to the interaction of all control system hardware and
software components at all levels.
2. INTERCONNECTIVITY.
This criterion is concerned with the transmission medium, which is
constrained by the network topology and how efficiently the
system’s components communicate with each other.

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3. DISASTER PROCESSING.
This component is defined by the efficiency with which the
software provides the operator with system failure information and
the ease at which the operator is permitted to bring the system back
to maximum operation after system failure.
4. DATABASE.
This refers to the software’s ability to maintain the system’s
database.
5. PROCESSES/DATA.
This criterion is concerned with the variety of processes and data
that can be controlled by the SCADA package.
6. DIAGNOSTICS.
The SCADA package’s ability to assist in the resolution of system
failures is evaluated by this diagnostic utility.
7. SECURITY.
This component is concerned with the levels of security provided
by the software.
8. MONITORING/CONTROL
Monitoring of a given process in real-time and control of that
process, within preset parameters, is evaluated by this criteria.
9. ALARM MANAGEMENT/LOGGING.
This is the category for detecting, annunciating, managing, and
storing alarm conditions.
10. STATISTICAL PROCESS CONTROL.
This is the portion of the SCADA package that evaluates the
process data. Production and quality is greatly effected by this data.
12. OPERATOR INTERFACE.
The graphical user interface (GUI) is evaluated using this criterion.

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13. TRENDING.
The software’s ability to display trending plots using historical and
current data is considered in this category.
14. REPORT GENERATION.
The production of logs and reports using current real-time data and
data retrieved from historical files is evaluated under this category.

Due to the advancements in computer technology and low cost, a
personal computer-based distributed control system can be installed for a
fraction of the cost required just a few years ago. However, prior to
selecting any piece of DCS equipment, first examine the existing
equipment, in particular the smart controllers, for network compatibility.
Then, examine and select the software to be employed.

1.3 What is PLC?

A programmable logic controller, also called a PLC or
programmable controller, is a computer-type device used to control
equipment in an industrial facility. The kinds of equipment that PLCs can
control are as varied as industrial facilities themselves. Conveyor
systems, food processing machinery, auto assembly lines…you name it
and there’s probably a PLC out there controlling it.
In a traditional industrial control system, all control devices are
wired directly to each other according to how the system is supposed to
operate. In a PLC system, however, the PLC replaces the wiring between
the devices. Thus, instead of being wired directly to each other, all
equipment is wired to the PLC. Then, the control program inside the PLC
provides the “wiring” connection between the devices.

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The control program is the computer program stored in the PLC’s
memory that tells the PLC what’s supposed to be going on in the system.
The use of a PLC to provide the wiring connections between system
devices is called soft-wiring.
Let's say that a push button is supposed to control the operation of
a motor. In a traditional control system, the push button would be wired
directly to the motor. In a PLC system, however, both the push button and
the motor would be wired to the PLC instead. Then, the PLC's control
program would complete the electrical circuit between the two, allowing
the button to control the motor.

Figure 1.4 PLC development

A PLC basically consists of two elements:
 The central processing unit
 The input/output system

1.3.1 The Central Processing Unit

The central processing unit (CPU) is the part of a programmable
controller that retrieves, decodes, stores, and processes information. It
also executes the control program stored in the PLC’s memory. In

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essence, the CPU is the “brains” of a programmable controller. It
functions much the same way the CPU of a regular computer does, except
that it uses special instructions and coding to perform its functions. The
CPU has three parts:
 The processor
 The memory system
 The power supply
The processor is the section of the CPU that codes, decodes, and
computes data. The memory system is the section of the CPU that stores
both the control program and data from the equipment connected to the
PLC. The power supply is the section that provides the PLC with the
voltage and current it needs to operate.

Figure 1.5 Microprocessor Hardware

1.3.2 The input/output (I/O) system

It is the section of a PLC to which all of the field devices are
connected. If the CPU can be thought of as the brains of a PLC, then the
I/O system can be thought of as the arms and legs. The I/O system is what
actually physically carries out the control commands from the program
stored in the PLC’s memory.

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The I/O system consists of two main parts:
 The rack
The rack is an enclosure with slots in it that is connected to the CPU.
 I/O modules
I/O modules are devices with connection terminals to which the field
devices are wired.

Together, the rack and the I/O modules form the interface between the
field devices and the PLC. When set up properly, each I/O module is both
securely wired to its corresponding field devices and securely installed in
a slot in the rack. This creates the physical connection between the field
equipment and the PLC. In some small PLCs, the rack and the I/O
modules come prepackaged as one unit.

Figure 1.6 I/O Racks

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1.4 How is a DCS different from a PLC system?

DCS PLC
Mfr sells a complete system of integrated Mfr sells some components; an SI
components. acquires others and engineers the system.
Mfr supports the system. Mfr supports the components.
On-line repair/ maintenance are the norm. Off-line repair/ maintenance are the norm.
System management built-in. System management designed per project.
Users expect to evolve/upgrade/expand a System is a one-off project (like a house).
system over 10/20/30 years. Upgrades / expansions are new projects.

1.5 Redundancy and Fault Tolerance

1.5.1 Redundancy
 Hardware redundancy
– add extra hardware for detection or tolerating faults
 Software redundancy
– add extra software for detection and possibly tolerating faults

1.5.2 Fault Tolerance
 Error Detection
 Damage Confinement
 Error Recovery
 Fault Treatment

1.5.2.1 Error Detection
 Ideal check
– Check should be independent from system
– Check fails if system crashes

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 Acceptable check
– Cost
– Reasonable check, e.g. monitor rate of change
 diagnostics
– Performed “by system on system components”
– E.g. power-up diagnostics

1.5.2.2 Damage Confinement
 Error might propagate and spread
 Identify boundaries to state beyond which no information exchange
has occurred

1.5.2.3 Error Recovery
 Backward recovery
– State is restored to an earlier state
– Requires checkpoints
– Most frequently used
– Recovery overhead
 Forward recovery
– Try to make state error-free
– Need accurate assessment of damage
– Highly application-dependent

1.5.2.4 Fault Treatment
 If transient fault: restart system, goto error-free state
 System repair
– On-line, no manual intervention, (automatic)
– Dynamic system reconfiguration
– Spare (hot or cold)

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1.5.2.5 Fault Coverage
 Measure of system’s ability to perform:
– Fault detection
– Fault location
– Fault containment
– (and/or fault recovery)
 Note:
– Recovery implies that the system as a whole is operational
– This does not imply that a “repair” occurred
– E.g. duplex system with benign fault can recover to continue
operation on one non-faulty processor

1.5.2.6 Hardware Redundancy
 Passive (static)
– Uses fault masking to hide occurrence of fault
– No action from the system is required
– E.g. voting
 Active (dynamic)
– Uses comparison for detection and/or diagnoses
– Remove faulty hardware from system => reconfiguration
 Hybrid
– Combine both approaches
– Masking until diagnostic complete
– Expensive, but better to achieve higher reliability

1.5.2.7 Passive Hardware Redundancy
 N-Modular Redundancy (NMR)
– N independent modules replicate the same function

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 Parallelism
– Results are voted on requirements: N >= 3
 TMR (Triple Modular Redundancy)

1.5.2.8 Fault tolerant structures
Fault tolerance allows continuing operation in spite of a limited
number of independent failures. Fault tolerance relies on work
redundancy.

1.5.2.9 Static redundancy: 2 out of 3
 Workby of 3 synchronised and identical units.
– All 3 units OK: Correct output.
– 2 units OK: Majority output correct.
– 2 or 3 units failure: Incorrect output.
– Otherwise: Error detection output.

Process input

sync sync

Voter

Process output

Figure 1.7 (2 out of 3) Redundancy

1.5.2.10 Dynamic Redundancy
 Redundancy only activated after an error is detected.
– Primary components (non-redundant)
– Reserve components (redundancy), standby (cold/hot standby)

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Input

Primary unit Standby unit

Switch
Output

Figure 1.8 Dynamic Redundancy

1.5.2.11 Workby and Standby
Workby Hot standby Cold standby

sync sync
on-line workby on-line standby

=?

Both computers are doing Standby is not computing Standby is no operational
the same calculations Error detection needed. Error detection needed.
at the same time Easy switchover in case Long switchover period
Comparison for easy of failure. with loss of state info.
error detection. Easy repair of reserve unit. No aging of reserve unit.
Comparator needed.
Non-redundant continuation
in case of failure?

Figure 1.9 Workby and Standby

1.5.2.12 Workby Fault-Tolerance for Integrity and Persistency
input input

synchronization synchronization

Worker Co E Worker Co E
Worker
- D Worker
- D
Matching Matching

Output Output

comparator commutator

disjunctor

output output

INTEGER PERSISTENT

Figure 1.10 Workby Fault-Tolerance for Integrity and Persistency

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1.5.2.13 Hybrid Redundancy
Mixture of workby (static redundancy) and standby (dynamic redundancy).

work- work- work- stand- stand-
by by by by by

voter

Reconfiguration work- work- work- stand-
by failed by by by
(self-purging
redundancy)

voter

Figure 1.11 Hybrid Redundancy

1.6 Microprocessor Control

For simple programming the relay model of the PLC is sufficient.
As more complex functions are used the more complex VonNeuman
model of the PLC must be used. A computer processes one instruction at
a time. Most computers operate this way, although they appear to be
doing many things at once. Consider the computer components shown in
Figure 1.12.

Figure 1.12 Simplified Personal Computer Architecture

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Input is obtained from the keyboard and mouse, output is sent to the
screen, and the disk and memory are used for both input and output for
storage. (Note: the directions of these arrows are very important to
engineers, always pay attention to indicate where information is flowing.)
This figure can be redrawn as in Figure 1.13 to clarify the role of inputs
and outputs.

Figure 1.13 An Input-Output Oriented Architecture

In this figure the data enters the left side through the inputs. (Note:
most engineering diagrams have inputs on the left and outputs on the
right.) It travels through buffering circuits before it enters the CPU. The
CPU outputs data through other circuits. Memory and disks are used for
storage of data that is not destined for output. If we look at a personal
computer as a controller, it is controlling the user by outputting stimuli on
the screen, and inputting responses from the mouse and the keyboard.
A PLC is also a computer controlling a process. When fully
integrated into an application the analogies become;
 Inputs - the keyboard is analogous to a proximity switch input
circuits - the serial input chip is like a 24Vdc input card

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 Computer - the 686 CPU is like a PLC CPU unit
 Output circuits - a graphics card is like a triac output card
 Outputs - a monitor is like a light
 Storage - memory in PLCs is similar to memories in personal
computers

It is also possible to implement a PLC using a normal Personal Computer,
although this is not advisable. In the case of a PLC the inputs and outputs
are designed to be more reliable and rugged for harsh production
environments.

1.7 Role Play

Each trainee should act a role play on the following:
1. Automation system structure.
2. What DCS and PLC and their differences?
3. Redundancy and fault tolerance.

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Chapter 2
Regulatory Control

2.1 Learning Objectives

 Introduce Regulatory Control.
 Understanding PID control.
 Differentiate between various control loops.

2.2 Introduction

Most of the applications of industrial control process used simple
loops which regulated flows, temperatures, pressures and levels.
Occasionally ratio and cascade control loops could be found. There are
many benefits for using regulatory control. One of the most important is
simply closer control of the process. Process control is one part of an
overall control hierarchy that extends downwards to safety controls and
other directly connected process devices, and upward to encompass
process optimization and even higher business levels of control such as
scheduling, inventory management.

Most control engineers would recognize the form of response
shown in figure 2.1. Actually the response could be determined by
solving a differential equation. It is more important to have a good
understanding of the physical response than to be able to predict the
solution by solving the differential equation.

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Figure 2.1 Response of simple dynamic process to step input change

Instrumentation, control and process engineers abstract the pictorial
form of the process into an iconographic diagram called "Piping and
Instrumentation Diagram", i.e. P&ID. Figure 2.2 is an example of the
P&ID.

Figure 2.2 Control loop representation used on P&IDs.

For description and analysis of a control loop, without referring to
whether it is implemented with analog or digital hardware, a block
diagram as shown in figure 2.3 is beneficial.

Figure 2.3 Simplified block diagram representation of process control loop.

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2.3 PID Control

2.3.1 Feedback Control

The principle of feedback is one of the most intuitive concepts
known. An action is taken to correct a less satisfactory situation then the
results of the action are evaluated. If the situation is not corrected then
further action takes place. Feedback control can be classified by the form
of the controller output. One of the simplest forms of output is discrete
form, also called on-off or two position control. An example of this is the
household thermostat, which activates heating unit if the temperature is
below the setting, or deactivates the unit if the temperature is above the
setting.

Figure 2.4 On-Off Control.

The idea of two position control can be extended to multi-position
control; an example is commercial air-conditioning refrigeration
equipment which is operated by loading and unloading compressor
cylinders. The ultimate extension is infinite number of positions which is
called modulating control; an example is the process controller output
that can drive a valve to any position between 0 and 100 percent, as
shown in figure 2.5.

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Figure 2.5 Flow versus position, infinite position Control.

2.3.2 Modes of Control

Feedback controllers use one, two, or three methods to determine
the controller output. These methods, called the modes of control,
including the following:
 Proportional (P)
 Integral (I)
 Derivative (D)
In general these modes can be used singly or in combination.

2.3.2.1 Proportional Mode

With a controller containing only the proportional mode, the
controller output is proportional to the measurement value only. Neither
history of the measurement value nor consideration to the rate of change
is utilized. Adjustment, i.e. tuning, of the controller is simple because
there is only one adjustment as shown in figure 2.6.

25


Figure 2.6 Relationship between input and output for proportional control.

Figure 2.7 illustrates a proportional control system. The rate of
fluid flow into the tank represents the load. To be in equilibrium, the
outflow must be the same as the inflow. The outflow is achieved by a
particular valve position where the fixed mechanism between the float,
pivot and link attain.

Figure 2.7 Proportional control.

2.3.2.2 Integral Mode
An integrator is the ideal device for automating the procedure for
adjusting the controller output bias. It is called the automatic reset.

2.3.2.3 Derivative Mode
The derivative is used to anticipate the effect of load changes by
adding a component to the controller output that is proportional to the rate
of change of the measurement. See figure 2.8.

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Figure 2.8 PID control.

2.3.3 Control Loop Structure

For microprocessor control system, control strategy is configured
by a series of software function blocks. Just like a set of hardware
modules require interconnections to form a complete control system, a set
of software function blocks also acquire interconnections, i.e. soft-wiring.

Figure 2.9 shows a simple feedback loop with the software portion
consists of three function blocks:
 An analog input block that causes the analog to digital converter to
convert the incoming 4-20mA signal to an analogous value. The value
is deposited in a memory register.
 A PID control block which obtains the measurement value from the
analog input block and compares it with the setpoint then it executes a
PID algorithm to calculate the output.
 An analog output block that obtains from the PID block the required
valve position value. The value is converted by a digital to analog
converter to 4-20mA signal.

27


Figure 2.9 Control loop hardware/software structure.

2.3.4 Control Loop Tuning

The power of PID control is that by good choice of control
parameters the controller can be adjusted to provide the desired behavior
on a wide variety of process applications. Determining acceptable values
of these parameters is called tuning the controller. A good criterion for
acceptable performance is the "quarter cycle decay" shown in figure 2.10.

Figure 2.10 quarter cycle decay criterion

Most loops are tuned by experimental techniques, i.e. trial and error.
Figures 2.11 and 2.12 give a tuning map for adjusting control parameters.

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Figure 2.11 Gain and Reset effects.

Figure 2.12 Derivative effects.

2.4 Control Loop Types
2.4.1 Ratio Control

Figure 2.13 shows the P&ID of a process heater in which the fuel
flow is measured and multiplied by the required air-to-fuel ratio; this
results in the required air flow rate, which is introduced as a setpoint of
the feedback controller. The required air-to-fuel ratio is automatically
adjusted as the output of the stack O2 controller.

29


Figure 2.13 ratio Control..

2.4.2 Cascade Control

In figure 2.14 the temperature controller cascades a steam flow
controller. The temperature controller would react to outlet temperature
drop by increasing the setpoint of the steam flow controller, which in turn
would increase the signal to the valve. The flow will quickly respond to
increased demand from the temperature controller and thus reaching the
desired setpoint of the outlet temperature stream.

Figure 2.13 Cascade Control.

2.4.3 Feedforward Control

With feedforward control, the objective is to drive the controlling
device from a measurement of the disturbance that is affecting the
process, rather than from the process variable itself. In figure 2.14, the

30


application was analyzed the variation in process inlet temperature was
the principle of disturbance. Hence, a feedforward controller is used to
drive the fuel flow controller by sensing the inlet temperature.

Figure 2.14 Feedforward Control.

2.4.4 Selector (Override) Control

There are several ways of using selector switches in control
strategies. One way is to select the higher (or lower) of several
measurement signals to pass the process variable to a feedback controller.
For example, the highest of several process temperatures may be selected
automatically to become the controlling temperature as shown in figure
2.15.

Figure 2.15 Override Control.

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2.4.5 Split Range Control

Split range control when one process variable such as plant inlet
pressure is used to manage two different output devices such as plant
bypass control valve and flow control loop for fractionation area. The 4-
12 mA signal is used to control the flow control loop. If the plant cannot
handle all incoming feed, the 12-20 mA signal control the plant bypass
valve to direct extra feed to the outside of the plant.

2.5 Role Play

The trainees are required to play roles about:
1. Introducing regulatory control.
2. Introducing modes of control.
3. Intruding control loop types.

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33


Chapter 3
DCS Infrastructure


 Introduce system infrastructure interoperability and interconnectivity.
 Illustrate system components of level 2 control.

3.2 Communication Bus

Figure 3.1: Communication Bus

The communication bus, i.e. the Nodebus, interconnects stations
(Control Processors, Application Processors, Application Workstations,
and so forth) in the system to form a process management and control
node. Depending on application requirements, the node can serve as a
single, stand-alone entity, or it can be configured to be part of a more
extensive communications network.
Operating in conjunction with the Nodebus interface electronics in
each station, the Nodebus provides high-speed, redundant, peer-to-peer
communications between the stations.
The high speed, coupled with the redundancy and peer-to-peer
characteristics, provide performance and security superior to that

34


provided by communication media used in conventional computer-based
systems. Station interfaces to the Nodebus are also redundant, further
ensuring secure communications between the stations. The Nodebus can
be implemented in a basic, non-extended configuration or it can be
extended through the use of Nodebus Extenders and Dual Nodebus
Interface Extenders.

3.2.1 Nodebus Interface

The Nodebus Interface is a module which allows direct connection
of a personal workstation (PW), with appropriate Nodebus connector card
and software, to the Nodebus figure 3.2. In this configuration, the PW
functions as a station on the node. The Nodebus Interface allows
connection of a station application workstation hosting an Ethernet
configuration to Nodebus. See figure 3.2.

Figure 3.2 Nodebus Interface Implementation (Typical)

35


An Attachment Unit Interface (AUI) cable, connects the PW or an
Ethernet hub configuration to the Nodebus via a Nodebus Interface. A
coaxial cable (ThinNet) connects an Ethernet daisy chain configuration to
the Nodebus via a Nodebus Extender. The Nodebus Interface is non-
redundant, and can be used in any of the Nodebus configurations
described.

3.2.2 Dual Nodebus Interface

The Dual Nodebus Interface (DNBI) is a module which allows
direct connection of stations to the appropriate Nodebus. Connection
between the DNBI and station is made via an AUI cable.

For data transmission security, a separate (RS-423) control cable
connects between the station and the DNBI to allow switching between
the two redundant Nodebus cables. Switching of the Nodebus cables is
controlled by the station, which transmits commands to the DNBI via the
control cable. Figure 3.3 shows connection of a station to the Nodebus
using a DNBI.

Figure 3.3 Local Connection of Station

3.2.3 Dual Nodebus Interface Extender

The Dual Nodebus Interface Extender (DNBX) is functionally
similar to the DNBI, but provides a greater cabling distance. The

36


principal transmission medium used is a coaxial Ethernet cable directly
connected to the station end by a standard Ethernet transceiver. Figure 3.4
remote connection of a station to the Nodebus using a DNBX.

Figure 3.4 Remote Connection of Station

3.3 Control Processor

The Control Processor performs regulatory, logic, timing, and
sequential control together with connected:
 Fieldbus Modules (FBMs)
 Fieldbus Cluster I/O Cards (FBCs)
It also performs data acquisition (via the Fieldbus Modules), alarm
detection and notification, and may optionally serve as an interface for
one or more Panel Display Stations.
The non-fault-tolerant version of the Control Processor is a single-width
processor module. The fault-tolerant version consists of two single-width
processor modules.

3.3.1 Enhanced Reliability

The Control Processor offers optional fault- tolerance for enhanced
reliability. The fault-tolerant control processor configuration consists of
two parallel-operating modules with two separate connections to the
Nodebus and to the Fieldbus.

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The two control processor modules, married together as a fault-
tolerant pair, are designed to provide continued operation of the unit in
the event of virtually any hardware failure occurring within one module
of the pair. Both modules receive and process information
simultaneously, and the modules themselves detect faults. One of the
significant methods of fault detection is comparison of communication
messages at the module external interfaces. Upon detection of a fault,
self-diagnostics are run by both modules to determine which module is
defective. The non-defective module then assumes control without
affecting normal system operations.

To further ensure reliable communications, the fault-tolerant
control processor performs error detection and address verification tests
in its Nodebus and Fieldbus interfaces. For enhanced reliability during
maintenance operations, the Control Processor is equipped with a
recessed reset button. This feature provides for manually forcing a
module power off and on (reboot) without removing the module from the
enclosure.

3.3.2 Diagnostics

The Control Processor uses three types of diagnostic tests to detect
and/or isolate faults:
 Power-up self-checks
 Run-time and watchdog timer checks
 Off-line diagnostics
Power-up self-checks are self-initiated when power is applied to
the control processor. These checks perform sequential tests on the
various control processor functional elements. Red and green indicators at

38


the front of the control processor module reflect the successful (or non-
successful) completion of the various phases of the control processor
startup sequence.
The run-time and watchdog timer checks provide continuous
monitoring of control processor functions during normal system
operations. The operator is informed of a malfunction by means of
printed or displayed system messages.
Off-line diagnostics are temporarily loaded into the system for the
purpose of performing comprehensive tests and checks on various system
stations and devices. Using the off-line diagnostics, a suspected fault in
the control processor can be isolated and/or confirmed.

3.4 Engineering Interface

The engineering interface, i.e. Application Processor, is
microprocessor-based application processor/file server stations. They
perform two basic functions:
 As application processor (computer) stations, they perform
computation intensive functions.
 As file server stations, they process file requests from tasks within
themselves or from other stations. Bulk storage devices used with
the Application Processors include floppy disk drives, hard disk
drives, streaming tape drives, and CD-ROMs.

The Application Processors operate in concert with other system
stations (such as communication processors, workstation processors, and
control processors), which provide the necessary means for data
input/output and operator interfacing. A smaller system can utilize a
single Application Processor, while a larger system can incorporate

39


several Application Processors, each configured to perform specific
functions. Some functions can be performed by individual Application
Processors, while others can be shared by two or more Application
Processors in the same network.
For all models of the Application Processor, applications range
from minimal functions, such as the storage of memory images, alarm
events, and historical data, to larger-scale applications such as database
management and program development.

3.4.1 Application Processor Functions

The following sections describe the major functions performed by
the Application Processors.

3.4.1.1 System and Network Management Functions

The Application Processors perform system management
functions, which include collecting system performance statistics, data
reconciliation, performing station reloads, providing message
broadcasting, handling all station alarms and messages, and maintaining
consistent time and date in all system stations. The Application Processor
also performs network management functions, which comprise that
portion of system management functions which deal with the network.

3.4.1.2 Database Management

Database management involves the storage, manipulation, and
retrieval of files containing data received and/or produced by the system.
The Application Processors utilize the industry-standard Relational Data
Base Management System.

40


3.4.1.3 File Requests

Each Application Processor contains a file manager, which
manages all file requests associated with bulk memory attached to the
Application Processor. Each Application Processor also supports a
remote file system that allows tasks in one station to share files in
another.

3.4.1.4 Historical Data

The Application Processors can be configured to contain the
Historian function, which maintains a history of application messages and
continuous and discrete I/O values. These values may represent any
parameters such as measurements, setpoints, outputs, and status switches
from stations that have been configured to collect data and send it to a
Historian. In addition, the Historian computes and stores a history of
averages, maximums, minimums, and other derived values. This
information is maintained for display, reporting, and access by
application programs. An archiving facility saves the data on removable
media, where applicable.

The Application Processors can be configured to maintain a history
of errors, alarm conditions, and selected operator actions. The occurrence
of errors, alarms, and events in other stations can be stored (for later
review and analysis) by sending a message defining the event to the
Historian in one or more Application Processors.

41


3.4.1.5 Graphic Display Support

The Application Processor supports graphic displays by storing and
retrieving display formats, by providing access to objects stored on the
Application Processor, and by storing tasks which execute in a
workstation processor. Application Processors not only provide storage of
information and file management for displays, but also execute programs
that perform display and trend service.

3.4.1.6 Production Control Software

Production control software represents a large range of packages
that require varied Application Processor resources. The following is a
list of packages provided:
 DBMS
 Historian
 Spreadsheet
 Physical Properties Library
 Mathematics Library
 BATCH
The operation and performance of the production control software are
determined by the particular Application Processor configuration.

3.4.1.7 Configuration

Configuration refers to the process of entering or selecting
parameters to define what a software package does, or to define the
environment for a software package. The Application Processors support
configuration functions by providing bulk storage for configuration
parameters and by executing some of the configuration processes.

42


3.4.1.8 Application Development Facilities

Application development tools are provided to build programs for
all system stations. These include tools to document, enter, translate, link,
test, and maintain programs written in several programming languages.
The Application Processor supports program development for all stations
(workstation processors, control processors, and so forth).
Assembly language, FORTRAN, and C programs can be written on
the Application Processor using standard operating system tools. An
optional package is available including text editors, debuggers, linkers,
revision control, and compilers, plus execution statistics functions.

3.4.1.9 User Application Program Execution

The Application Processors also execute user application programs.
These may be application packages such as special optimizations, test
data collections, special data reductions, or other packages that you may
have already developed. The allocation of resources reserved for user
application varies with each Application Processor.

3.4.2 Diagnostics

The Application Processors utilize three types of diagnostic tests to
detect and/or isolate faults:
 Power-up self-checks
 Run-time and watchdog timer checks
 Off-line diagnostics
Power-up self-checks are initiated when power is applied to the
Application Processor. These checks perform sequential tests on the

43


various Application Processor functional elements. Any malfunction
detected during the power-up self-checks is reported by means of
messages printed or displayed on a directly connected printer or terminal.
The run-time and watchdog timer checks provide continuous
monitoring of Application Processor functions during normal system
operations. For any processor model, you are informed of a malfunction
by means of printed or displayed system messages. Off-line diagnostics
are temporarily loaded into the system for the purpose of performing
comprehensive tests and checks on various system stations and devices.
Using the off-line diagnostics, a suspected fault in the Application
Processor can be isolated and/or confirmed.

3.4.3 Workstation Components

The workstation components provide user interface to all System
CRT display functions. A selection of workstation components is
available for command and data entry, along with CRT pointer
manipulation and control. These components interact with software
resident in versions of the system Workstation Processors (WPs) and
Application Workstation Processors (AWs). Many of these components
(displays and keyboards) are "common" and allow interchangeability and
simplicity in mixed technology configurations.
Workstation components include:
 Alphanumeric Keyboard
 Annunciator and Annunciator/Numeric Keyboards
 Workstation Display (with/without Touchscreen)
 Mouse
 Trackball
 Industrial Pointing Device

44


 Workstation Processor or Application Workstation Processor
 Personal Workstation
 Modular Industrial Console
Selection of the touch screen, mouse, trackball or industrial
pointing device is required for picking display objects on the CRT. The
touch screen has sufficient resolution for all functions normally
associated with a process operator. Only the mouse or trackball provides
the picking resolution necessary for engineer-related functions (for
example, building graphic displays). The touch screen associated with
Workstation Display and the annunciator type keyboards connects to a
Graphics Controller Input Output (GCIO) interface unit located beneath
the workstation display. The GCIO interfaces to the Workstation
Processor and/or Application Workstation that provide secure, high-
speed, bidirectional data flow. The alphanumeric keyboard and trackball
connect together in a functional grouping via a serial communications
link to the processors. Personal Workstations (PW) utilize separate serial
communication links for alphanumeric keyboard and mouse/trackball.
These buses allow a variety of component connections.

Figure 3.5 Table- Workstation Components.

45


3.4.3.1 Alphanumeric Keyboard

The alphanumeric keyboard is used any time text is entered into the
system. It consists of the full set of alphanumeric keys plus punctuation
and special symbol keys laid out in the standard format, and a numeric
data entry pad (with cursor control).

Figure 3.6 Alphanumeric Keyboard

3.4.3.2 Annunciator Keyboard

The Annunciator Keyboard Figure 3.7 is an array of LED/switch
pairs. It also contains a horn silence switch and a lamp-test switch. Each
LED, under control of the processor software, may be ON, OFF, or
FLASHING as determined by the process conditions. The LEDs, when
used in conjunction with the unit's audible annunciator, form an effective
means of calling a user's attention to specific areas of the system. The
switch associated with each LED can be used to invoke any pre-
configured displays or operator responses..

Figure 3.7 Annunciator Keyboard

3.4.3.3 Workstation Display with/without Touchscreen

The workstation display is an analog cathode ray tube (CRT) color
monitor supporting ultra-high resolution applications. The monitor is
suitable for mounting onto a Modular Industrial Workstation or on a

46


desktop. The monitor can include a touchscreen optional feature. Figure
3.8 shows the monitor with a tilt and swivel base mounted on the GCIO
interface unit. The GCIO interface supports the touchscreen, annunciator
and annunciator/ numeric keyboard, and audible horn options.

Figure 3.8 Table-Top Workstation Display

The optional touch screen is bonded to the front surface of the CRT
monitor. The user selects display objects by touching them on the screen.
The touch screen senses the action and sends a data signal to the
workstation processor's software indicating the position of the selection.
3.4.3.4 Trackball

The trackball is a stationary component that contains a rotatable
sphere. The trackball can be located on a table top. Rotation of the sphere
causes CRT pointer movement analogous to the mouse action. Buttons
are also provided for user selections/manipulations. See Figure 3.9

Figure 3.9 Trackball

3.4.3.5 Modular Industrial Console

Modular Industrial Consoles provide flexible mounting
arrangements of components. They allow users to configure centralized
or distributed control centers tailored to the functional requirements of
each interaction point in the plant. The modular console furniture

47


described herein may incorporate a mix of equipment - console displays,
input devices, processors, Fieldbus Modules, data storage devices, and so
on. Alternately, only display-specific equipment can be incorporated.
Modular Industrial Consoles (MICs) are ideal for supporting powerful
multiple-screen, real-time display software interactions. This combination
allows console resources to be optimally allocated to meet changing day-
to-day needs.

3.5 Operator Interface

Operating in conjunction with human interface input/output
components, the workstation processors serve as a link between the
operator and other distributed processor modules. They receive graphic
and textual information both stored internally or from application
processors and generate signals to display the information on a
workstation display. Display formats and data files are available from
bulk storage. Live display information (distributed data objects) is
available from any control -processor, or from shared system global data.
The video information displayed can include free form combinations of
text, graphic illustrations, charts, and control displays.
The workstation processors display textual information as 80 text
characters per line, with four fonts. The processors provide resizable and
restackable windows. Displays for all of the workstation processors may
also be developed using the system software running in a compatible
personal computer.
A workstation processor, together with its workstation monitor and input
components, can be configured with combinations of peripherals to suit
functions and user preferences.

48


3.6 Gateways

The architecture of the DCS permits it to be connected to other
foreign systems using a gateway module for adapting different
communication protocols. See figure 3.10.

Figure 3.10 Field Automation Subsystem

3.7 Role Play

Each trainee should introduce one of the main components:
1. Communication Bus
2. Control Processor.
3. Application Processor
4. Operator Interfaces and Gateways

49


Chapter 4
DCS Hardware


 Define fieldbus communication.
 Illustrate system components of level 1 control.
 Demonstrate interconnection between different components.
 Develop knowledge base of foundation fieldbus technology.

4.2 Fieldbus Modules

Fieldbus Modules provide connection of digital I/O, analog I/O,
and Intelligent Transmitters to control processors. There are two types of
Fieldbus Modules: Main and Expansion. Some main modules can be
expanded using an expansion module.

A wide range of Fieldbus Modules is available to perform the
signal conversion necessary to interface the control processor with field
sensors and actuators.

4.3 Fieldbus Interconnection

The Control Processor is used in three different configurations, which
provide broad flexibility in Fieldbus implementation:
 Local Fieldbus (Figure 4.1) - Used only within the enclosure.
Fieldbus Modules attach directly to the redundant local bus.

50


Figure 4.1 Local Fieldbus

 Twinaxial (Dual-Conductor Coaxial) Fieldbus Extension (Figure
4.2) - Using twinaxial cable, the Fieldbus can optionally extend
outside of the enclosure. Fieldbus Modules attach to the extended
bus through Fieldbus isolators. The twinaxial Fieldbus extension
may be redundant.

Figure 4.2 Twinaxial Fieldbus Extension

 Fiber Optic Fieldbus Extension (Figure 4.3) - The fiber optic
Fieldbus can optionally extend the distance as well as add
application versatility and security.

Figure 4.3 Fiber Optic Fieldbus Extension

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All three Fieldbus configurations use serial data communication
complying with Electronic Industrial Association (EIA) Standard RS-485.

4.4 Cluster I/O Subsystem Interfacing

The Control Processor interfaces with the Fieldbus Cluster
Input/Output Subsystem that consists of the Fieldbus, a multi-slot chassis
configuration of a Fieldbus Processor, analog/digital Fieldbus Cards
(FBCs), and power supply and power monitor card. These Cluster I/O
subsystems meet the needs of applications where a high number of
channels per card are required. Figure 4.4 shows a typical twinaxial
Fieldbus configuration.

Figure 4.4 Twinaxial Fieldbus Cluster I/O Subsystem Interface Configuration

4.5 Fieldbus Cluster I/O Subsystem

The Fieldbus Cluster Input/Output Subsystem provides full support
for analog measurement, digital sensing, and analog or discrete control
capabilities. The Subsystem integrates with the Control Processor or
Personal Workstation via the Fieldbus, and includes a multi-slot chassis
configuration made up of a Fieldbus Processor, Analog/Digital Fieldbus
Cards (FBC), subsystem main power supply, and power monitor card.

52


The Fieldbus Cluster I/O Subsystem is configurable, gathering
analog measurements, while simultaneously handling analog and digital
input and output channels. The Fieldbus Cluster I/O Subsystem is offered
in both non-redundant and redundant configurations. Each in a redundant
pair is individually addressable on the Fieldbus with a unique logical
address. In a redundant configuration, the FBPs provide switchover from
the primary FBP to the redundant FBP and back again automatically. The
FBCs are suitable in applications where a high number of channels per
card are required. They are ideal for non-isolated and isolated input signal
gathering and data acquisition systems where high quantities of "points
per cluster" areas are desired. The FBCs may be optionally connected as
redundant pairs. Various input cards are available with one of the
following three levels of isolation:
 Non-isolated - Each channel is referenced to ground and the card
itself is referenced to ground.
 Group-isolated - Electrically separate card-to-card but not channel-
to-channel on the same card.
 Isolated - Each channel is electrically separated from any other
channel, card, group, building, site, etc.

4.6 Fieldbus Processor

The Fieldbus Processor (FBP) module provides communication
between the Fieldbus Cards (FBCs) and the Control Processor. Optionally
available is redundancy for the FBP module. Each FBP module is
individually addressable via the Fieldbus. If the primary FBP fails or is
taken off-line, the secondary FBP automatically assumes control. It
remains in control until the primary FBP returns on-line (figure 4.5).

53


Figure 4.5 FBP Overview

4.7 Fieldbus Cards

The Fieldbus Cards support a variety of analog and digital I/O
signals. The FBCs convert electrical I/O signals used by field devices to
permit communication with these devices via the Fieldbus.
The FBCs can be connected in a redundant configuration via the
hardware. The redundant FBCs must be in adjacent slots and they are
connected via a hardware adapter at the interface to the field devices. In
an FBC redundant configuration, the FBP determines which FBC of the
redundant pair is to supply the data to the Control Processor. This is done
in the software by a predetermined set of conditions.

4.7.1 Analog FBCS

The analog FBCs support analog signal types and control functions
equipped with accurate signal conditioning circuitry, the analog cards
interface between process sensors and actuators.
To input an analog voltage (into DCS) the continuous voltage value
must be sampled and then converted to a numerical value by an A/D

54


converter. Figure 4.6 shows a continuous voltage changing over time.
There are three samples shown on the figure. The process of sampling the
data is not instantaneous, so each sample has a start and stop time. The
time required to acquire the sample is called the sampling time. A/D
converters can only acquire a limited number of samples per second. The
time between samples is called the sampling period T, and the inverse of
the sampling period is the sampling frequency (also called sampling rate).
The sampling time is often much smaller than the sampling period.

Figure 4.6 Sampling an analog voltage

Analog outputs are much simpler than analog inputs. To set an
analog output an integer is converted to a voltage. This process is very
fast, and does not experience the timing problems with analog inputs.
But, analog outputs are subject to quantization errors. Figure 4.7 gives a
summary of the important relationships. These relationships are almost
identical to those of the A/D converter. Assume we are using an 8 bit D/A
converter that outputs values between 0V and 10V. We have a resolution
of 256, where 0 results in an output of 0V and 255 results in 10V. The
quantization error will be 20mV. If we want to output a voltage of
6.234V, we would specify an output integer of 159, this would result in
an output voltage of 6.235V. The quantization error would be 6.235V-
6.234V=0.001V. The current output from a D/A converter is normally
limited to a small value, typically less than 20mA.

55


Figure 4.7 D/A converter

4.7.2 Digital FBCS

The digital FBCs consist of 32- and 64-channel types. Inputs can
be either voltage monitoring or contact sensing.
Contact inputs must convert a variety of logic levels to the 5Vdc
logic levels used on the data bus. This can be done with circuits similar to
figure 4.8. Basically the circuits condition the input to drive an
optocoupler. This electrically isolates the external electrical circuitry from
the internal circuitry. Other circuit components are used to guard against
excess or reversed voltage polarity.

Figure 4.8 Contact input circuitry.

Contact outputs must convert the 5Vdc logic levels on the DCS
data bus to external voltage levels. This can be done with circuits similar
to figure 4.9. Basically the circuits use an optocoupler to switch external
circuitry. This electrically isolates the external electrical circuitry from

56


the internal circuitry. Other circuit components are used to guard against
excess or reversed voltage polarity.

Figure 4.9 Contact output circuitry.

4.8 Other Modules

 0 to 20 mA Input/Output Interface
 Pulse Input, 0 to 20 mA Output Interface
 Thermocouple/ Millivolt Input Interface
 RTD Input Interface
 High Power Contact/dc Input/Output Interface

4.9 Foundation Fieldbus Technology

FOUNDATION fieldbus is an all-digital, serial, two-way
communications system that serves as the base-level network in a plant or
factory automation environment.

Figure 4.10 Foundation Fieldbus Network

57


Figure 4.11 Historical development of field devices technology.

It's ideal for applications using basic and advanced regulatory
control, and for much of the discrete control associated with those
functions. Two related implementations of FOUNDATION fieldbus have
been introduced to meet different needs within the process automation
environment. These two implementations use different physical media
and communication speeds.
 H1 works at 31.25 Kbit/sec and generally connects to field devices.
It provides communication and power over standard twisted-pair
wiring. H1 is currently the most common implementation and is
therefore the focus of these courses.
 HSE (High-speed Ethernet) works at 100 Mbit/sec and generally
connects input/output subsystems, host systems, linking devices,
gateways, and field devices using standard Ethernet cabling. It
doesn't currently provide power over the cable, although work is
under way to address this.

Figure 4.12 Field Device Capacity.

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Conventional analog and discrete field instruments use point-to-
point wiring: one wire pair per device. They're also limited to carrying
only one piece of information -- usually a process variable or control
output -- over those wires. As a digital bus, FOUNDATION fieldbus
doesn't have those limitations.

 Multidrop wiring. FOUNDATION fieldbus will support up to 32
devices on a single pair of wires (called a segment) -- more if
repeaters are used. In actual practice, considerations such as power,
process modularity, and loop execution speed make 4 to 16 devices
per H1 segment more typical.

That means if you have 1000 devices -- which would require 1000 wire
pairs with traditional technology -- you only need 60 to 250 wire pairs
with FOUNDATION fieldbus. That's a lot of savings in wiring (and
wiring installation).

Figure 4.12 Fieldbus wiring diagram.

59


 Multivariable instruments. That same wire pair can handle
multiple variables from one field device. For example, one
temperature transmitter might communicate inputs from as many as
eight sensors -- reducing both wiring and instrument costs.

Other benefits of reducing several devices to one can include fewer pipe
penetrations and lower engineering costs.

 Two-way communication. In addition, the information flow can
now be two-way. A valve controller can accept a control output
from a host system or other source and send back the actual valve
position for more precise control. In an analog world, that would
take another pair of wires.
 New types of information. Traditional analog and discrete devices
have no way to tell you if they're operating correctly, or if the
process information they're sending is valid.

But FOUNDATION fieldbus devices can tell you if they're operating
correctly, and if the information they're sending is good, bad, or
uncertain. This eliminates the need for most routine checks -- and helps
you detect failure conditions before they cause a major process problem.

 Control in the field. FOUNDATION fieldbus also offers the
option of executing some or all control algorithms in field devices
rather than a central host system. Depending on the application,
control in the field may provide lower costs and better performance
-- while enabling automatic control to continue even if there's a
host-related failure.

60


FOUNDATION fieldbus is covered by standards from three major
organizations:
 ANSI/ISA 50.02
 IEC 61158
 CENELEC EN50170:1996/A1

The technology is managed by the independent, not-for-profit
Fieldbus Foundation, whose 150+ member companies include users as
well as all major process automation suppliers around the globe.
Some suppliers have even donated fieldbus-related patents to the Fieldbus
Foundation to encourage wider use of the technology by all Foundation
members.

Interoperability simply means that FOUNDATION fieldbus
devices and host systems can work together while giving you the full
functionality of each component.

4.10 Role Play

Each trainee should introduce one of the main components:
5. Fieldbus Module and Interconnection
6. Fieldbus Processor and Clusters.
7. Foundation Fieldbus technology

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Chapter 5
DCS Software

5.1 Learning objectives

 To be familiar with main software components of DCS.
 Understand main tasks for each application.

5.2 Standard Application Packages
5.2.1 System Management
Features include:
 Display of equipment information for the station and its associated
input/output devices, buses, and printers.
 Capability for change actions directed to the associated equipment.
 Processing of station alarm conditions and messages.
5.2.2 Database Management
Features include:
 Storage, retrieval, and manipulation of system data files.
 A run-time license for the embedded use of the Relational Database
Management System.
 A spreadsheet package.

5.2.3 Historian
Features include:
 Maintenance of a history of values for process-related
measurements that have been configured for retention by the
Historian.

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 Maintenance of a history of application messages that have been
sent to the Historian.
 Maintenance of a history of alarms and error conditions which
generate messages for the Historian.
 Access to all Historian data by display and report application
programs.

5.2.4 View Display Manager
Features include:
 Presentation of the operating environment.
 Setting of the overall operating environment according to the type
of user. Process engineers, process operators, and software
engineers have access to specialized functions and databases suited
to their specific requirements and authorizations.
 Dynamic and interactive process graphics.
 Display and processing of current process alarms.
 Group and default displays for control blocks.
 Execution of embedded trending within displays.

5.2.5 Draw Display Builder
Features include:
 Graphical display configuration for viewing and control of process
operation.
 Access to graphical object palettes allowing easy inclusion of
pumps, tanks, valves, ISA symbols, and similar complex objects.
 Ready modification of existing displays using a mouse pointer,
menu items, and quick-access toolbars.
 Association of process variables with objects in the displays.

63


 Dynamic variation of object attributes such as fill level, color,
position, size and visibility with changes in the associated process
variable.
 Inclusion of operator control elements such as pushbuttons and
sliders into displays.
 A library of faceplates which may be configured by simply
specifying the compound and block name of the block to which the
faceplate is to be connected.

5.3 Alarm System

Figure 5.1 Alarm manger

Alarm Manager provides an easy-to-use graphical interface of
preconfigured alarm displays for viewing and quickly responding to
process alarm conditions. The alarm display windows present alarm
messages initiated by the control blocks and related to digital input, state
change, absolute analog, deviation, rate of change, device status
mismatch, and other alarm conditions.
Accessible from any environment, the Alarm Manager Display windows
provide:

64


 Quick, easy access to the most recent alarm messages via the Most
Recent Alarm display or Current Alarm display
 Alarm status and value information dynamically updated from the
control station
 Color-coded priority and status indicators that allow you to quickly
focus in on critical alarms
 Summary displays for different views of the alarm database based
on alarm status
 An historical list of alarms
 The capability to view subsets of alarms based on specific user-
defined criteria
 The capability to silence or temporarily mute workstation and
annunciator horns.
 Secured access to alarming functions dependent on user or system
responsibility
This set of resizable alarm displays providing a variety of current and
historic views of the process alarm database includes:
 A multi-page list of all the current alarms
 A single page of the most recent, active, unacknowledged alarms
with dynamically updating value and status fields
 Three summary displays specific to alarm status also with updating
values and statuses:
o all active, unacknowledged alarms
o all unacknowledged alarms that have returned to normal
o all active, acknowledged alarms
 A list of historized alarms related to the selected historian database
 An operations display for silencing horns, temporarily muting
horns, changing environments

65


These displays allow you to respond to alarm conditions, filter and
analyze specific alarm data, and maintain alarm message files for
reporting purposes.
The Process or Alarm button in the Display Manager (DM) window
indicates the presence of alarms (both acknowledged and
unacknowledged) and provides access to Alarm Manager Displays.
Initially, the Current Alarm Display (CAD) appears and the other
displays are easily accessible from the CAD via its default Displays
menu:
 Most Recent Alarm display (MRA)
 New Alarm display (NEWALM)
 Unacknowledged Alarms display (UNACK)
 Acknowledged Alarms display (ACKALM)
 Alarm History display (AHD)
 Operations display (OPR)
These easy-to-use displays support the following features:
 A pre-configured number of alarms per screen or page
 Pre-configured alarm message information and formatting per
alarm type
 A status area for indication of current Alarm Manager and display
status, such as horns muted, match active, display paused, initial
call-up time
 Buttons for responding to alarm conditions, such as acknowledging
or clearing alarms, and for accessing additional alarm information
and process displays
 Pull-down menus for editing, viewing, and filing functions
 A pull-down menu for accessing other displays
 Pop-up menus for quick access to commonly used functions

66


 A scroll bar and Go To Page option for moving easily through the
alarm list
Although a preconfigured set of alarm displays is provided, many aspects
of the displays and alarm message content are user configurable to
accommodate different process control applications and operational
needs. See the section on Alarm/Display Manager Configurator.

5.4 Historian

The Historian collects, stores, processes, and archives process data
from the control system to provide data for trends, Statistical Process
Control (SPC) charts, logs, reports, spreadsheets, and application
programs. The Historian software is an easy-to-use data collection tool
that allows the user to organize and enforce a plant data collection
philosophy. The Historian provides extensive data collection and
management functions, and data display functions for use by process
engineers or operators.
Typical historical data are process analog and/or digital variables
(points). The Historian can also collect and display application generated
messages. You can use the Historian to collect data in support of the
following production control functions:
 Cost accounting
 Equipment performance analysis
 Historical trending
 Information retrieval
 Inventory management
 Legal record maintenance
 Lost time analysis

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 Maintenance reporting
 Material accounting
 Process analysis
 Production reporting
 Quality control
The Historian can:
 Retrieve variables from process databases or accept data from
production control databases maintained by user application
programs.
 Perform built-in calculations on the collected data.
 Store calculated (reduced) data in a real time, relational database.
Application software in a plant-wide control system can access the
Historian database to obtain historical data for process control, production
control, and management information reporting.
You can use SPC chart displays of Historian data to monitor process
variables on-line via the Statistical Process Control Package (SPCP).
You can build displays for trending historical data via the Display Builder
and Display Configurator with Trending software.
Using the Report Writer, you can generate detailed reports of historical
data for management information.
Examples of Industrial Software that interface with the Historian are:
 Batch Plant Management
 Data Validator
 Display Manager
 Display Configurator with Trending
 Object Manager (for process data histories)
 Operator Action Journal
 Operator Message Interface
 Real-Time Data Base Manager

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 Spreadsheet
 Statistical Process Control Package
 System Monitor
 Report Writer

5.5 Draw

Figure 5.2 Draw

Draw is a display builder and configurator that allow you to create
and maintain dynamically updating process displays. Displays can
represent the plant, a process area or a detailed portion of the process.
You can draw basic objects using Draw's toolbars, menu items and
shortcut keys. You assign graphic attributes such as color and line style to
the objects, and then configure them to reflect process variable changes or
operator actions. Draw includes numerous palettes of objects such as
operator buttons, pumps, tanks, pipes, motors, valves and ISA symbols.
You can also create your own palettes for storing complex objects and
company-standard symbols. Displays can include faceplates, trends and
bitmapped images. You can easily edit your displays to reflect changes in
the process control scheme or to maximize operating efficiency and
security.

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