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IDC Technologies

Industrial Automation

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ISBN 978-87-403-0004-8

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1

Introduction to Plant Design

12

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Instrumentation documentation

17

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Basic Control Concepts

23

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Control modes in closed loop control

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Cascade Control

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Feed forward Control

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Automatic feedforward

35

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10

Time matching as feedforward control

36

3
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First term explanation(disturbance free PV)

37

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1

Introduction

39

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Internal Model Control

41

5 
Industrial Data Communications and Wireless

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Open Systems Interconnection (OSI) model

45

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Fiber Optics

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Data Highway Plus /DH485

5
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AS-i

5
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Profibus

5
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360°
thinking


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© Deloitte & Touche LLP and affiliated entities
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Industrial Ethernet

59

5
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Wireless Fundamentals

64

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Installation and Troubleshooting

65

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Network threats, vulnerabilities and risks

74

5
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Securing a network by access control

77

5
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Intrusion detection systems

79

5
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VPNs and their security

81

5
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1

Introduction

84

6
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1

Introduction

87

7
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3

SIS configurations for safety and availability targets

101

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5

Selection of safety controllers

110

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Programming tools

112

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9

Guide to Regulations and Standards

114

8 
Hazardous Areas and Intrinsic Safety

118

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Zonal Classification

120

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4

Methods of explosion protection

124

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Intrinsic safety

127

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Certification (components)

130

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Non Sparking concept

131

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Other protection concepts

135

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Industrial Automation

Contents

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Fault finding and repairs

139

9 SCADA

141

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SCADA Systems Software

143

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Introduction to the PLC

158

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An alarm system

161

10 
Project Management of I&C Projects

167

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Time management

169

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Integrated cost and time management

171

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Risk Management

173

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1

179

Basic Measurement performance terms and specifications

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Industrial Automation

Contents

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3

Pressure Measurement

181

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Temperature Measurement

188

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Resistance Temperature Detectors (RTDs)

189

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Infrared Pyrometers

191

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Flow Measurement

191

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Magnetic Flowmeters

196

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Main Technology Trends

202

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Market Predictions

204

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Industrial Automation

Preface

Preface
Industrial Automation is a discipline that includes knowledge and expertise from various branches of engineering including
electrical, electronics, chemical, mechanical, communications and more recently computer and software engineering
...

Industrial Automation Engineers have always drawn new technologies and implemented original or enhanced versions to
meet their requirements
...

IDC Technologies has been in the business of bringing together the domain gurus and the practicing engineers under an
umbrella called training
...

The breadth and depth of Industrial Automation is enormous and justice cannot be expected from a book of a few hundred
pages
...

This book delivers a critical blend of knowledge and skills, covering technology in control and instrumentation, industry
analysis and forecasts, leadership and management - everything that is relevant to a modern control and instrumentation
engineer
...
These highly practical
materials provide you with solid skills in this often neglected area for control and instrumentation engineers
...
We have made an effort to include IEEE/ANSI/NEMA references wherever possible
...

The terms ‘earth’ as well as ‘ground’ have both been in general use to describe the common power/signal reference point
interchangeably around the world in the Electro-technical terminology
...
In this book, we chose to adopt the term ‘ground’ to denote the common electrical reference point
...


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In addition to the industrial production with which it is popularly associated, it now covers a number of
unexpected areas
...
Automation engineering
is a cross sectional discipline that requires proportional knowledge in hardware and software development and their
applications
...
 This picture has changed since computers and software have made their way into
every component and element of communications and automation
...
No other domain demands so much
quality from so many perspectives of the function, yet with significant restrictions on the budget
...

This book is structured to walk you through a précised life cycle of the various automation activities of a plant
...


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1

Introduction to Plant Design

Plant design (process plant design, power plant design, etc
...
Such plants can be built for chemical,
petroleum, utility, shipbuilding, and other facilities
...


2
...

‘Feasibility’ study is the name given to a small design project that is conducted to determine the scope and cost of
implementing the project from concept to operation
...

Start by creating a basic flow diagram that illustrates the objective for the proposed plant; this diagram is called a “Process
Block Diagram”
...
2
...
1 is where it all starts
...
This is a diagram of the concept, giving a very broad view of the process
...
With this philosophy diagram complete, there is a need to determine the technical requirements
...


Figure 2
...
2
...
The idea behind the PFD is to show the entire process (the big picture) on as few drawing sheets as
possible, as this document is used to develop the process plant and therefore the process engineer wants to see as much
of the process as possible
...


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Mass balance: In its most simple form, what goes in must come out
...


Process description
• The process description details the function / purpose of each item of equipment in the plant
...
There will be batches of caffeinated and
decaffeinated coffee, the coffee tanks and pipelines must be thoroughly cleaned between batches
• Milk supply – There will be an option for low fat or full cream milk, the milk supply should be sufficient for
three days operation and should be kept as close to freezing as possible to ensure longevity of the milk
• Sugar supply – Sugar will be supplied in a syrup form, we will offer the coffee with no sugar, 1 teaspoon (5
ml of syrup) or two teaspoons (10 ml of syrup)
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Industrial Automation

I&C Drawings and Documentation

• Liquid characteristics – A detailed description on analysis of each liquid type in the system
...

• Specific operating conditions linked to the process – The installation operates 24 hours a day, 365 days a
year
...

PFD now starts to look something like the Figure 2
...


Figure 2
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2
...

The PFD defines “The flow of the process” The PFD covers batching, quantities, output, and composition
...
The P&ID provides
direct input to the field for the physical design and installation of field-run piping
...


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It accomplishes this by showing all of the piping, equipment, principal instruments, instrument loops, and
control interlocks
...

The typical plant operation’s environment uses the P&ID as the principal document to locate information about the
facility, whether this is physical data about an object, or information, such as financial, regulatory compliance, safety,
HAZOP information, etc
...
Once thoroughly conversant with the PFD & Process description, the engineers from the relevant disciplines
(piping, electrical & control systems) attend a number of HAZOP sessions to develop the P&ID
...
2
...
These standards must define the
format of each component of the P&ID
...
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3 Completed P&ID

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3

I&C Drawings and Documentation

Instrumentation documentation

Instrumentation documentation consists of drawings, diagrams and schedules
...
Of all the disciplines in a project, instrumentation is the most interlinked and therefore
the most difficult to control
...

• Design
• Design criteria, standards, specifications, vendor lists
• Construction
• Quantity surveying, disputes, installation contractor, price per meter, per installation
• Operations
• Maintenance commissioning

2
...
All the instruments of the same type (tag) are listed
together; for example, all the pressure transmitters ‘PT’ are grouped together
...
1 Instrument list

2
...
2

Instrument location plans

The instrument location drawing is used to indicate an approximate location of the instruments and junction boxes
...
This drawing
is also used to give the installation contractor an idea as to where the instrument should be installed
...
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Industrial Automation

2
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I&C Drawings and Documentation

Cable racking layout

Use of the racking layout drawing has grown with the use of 3D CAD packages; this drawing shows the physical layout
and sizes of the rack as it moves through the plant
...
4 Cable racking layout

2
...
4

Cable routing layout

Prior to the advent of 3D CAD packages, the routing layout used a single line to indicate the rack direction as well as
routing and sizes and was known as a ‘Racking & Routing layout’
...
5 Cable routing layout

2
...
5

Block diagrams – signal, cable and power block diagrams

Cable block diagrams can be divided into two categories: Power and Signal block diagrams
...


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6 Block diagram

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2 Field connections / Wiring diagrams

Field connections / Wiring diagrams

Table 2
...
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Industrial Automation

I&C Drawings and Documentation
Table 2
...
5 Loop diagrams

2
...


2
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1

The Load List

The load list is used to total the power supply requirements for each device per plant area or process
...
The sample table shown below is a typical layout of a load list
...
6 Sample

2
...
2

The Single Line Diagram

The single line diagram (sometimes called the one line diagram) uses single lines and standard symbols to show electrical
cables, bus bars and component parts of a circuit or system of circuits
...
Duplication of a 3-wire system is reduced by showing single devices on a single wire
...


2
...
3

The schematic diagram (main and circuit)

Schematic diagram shows both the main circuit and the control circuit in far greater detail; here all three lines of a 3-phase
system are shown
...


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2
...
4

Plant layout drawings

The plant layout drawing gives a physical plant layout, where equipment is drawn to resemble the plant item it represents
...
4
...


2
...
6

Installation Details

The installation detail shows the layout of the equipment and gives an itemized list of all the equipment on the drawing
as well as notes on the installation
...
4
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The notes detail various items like specification references (paint, powder
coating) and general notes
...
4
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It gives a source and destination for each cable and specifies
the type of cable
...

Hazardous area drawings: A plant location drawing (in both plan and elevation) which shows, by means of overlays,
plant area classifications (by zone and gas group) for potential leak hazards throughout a plant
...
These are most often used in the basic IEC programming language in PLCs, but are sometimes
used in hardwired relay circuits
...
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Industrial Automation

Process control

3 Process control
3
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1
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1 Block diagram showing the elements of a process control loop

Two of the most important signals used in process control are called
• Process Variable or PV
• Manipulated Variable or MV
In industrial process control, the Process Variable or PV is measured by an instrument in the field and acts as an input to
an automatic controller which takes action based on the value of it
...

The variable to be manipulated, in order to have control over the PV, is called the Manipulated Variable
...
Here, the valve position is called the Manipulated
Variable and the measured flow becomes the Process Variable
...
2

Principles of Control Systems

To perform an effective job of controlling a process, we need to know how the control input we are proposing to use will
affect the output of the process
...

• What will be the response curve or trajectory of the response?
The answers to these questions are best obtained by creating a mathematical model of the relationship between the
chosen input and the output of the process in question
...
The following section introduces
the principles that should apply to most practical control loop situations
...
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Industrial Automation

Process control

Figure 3
...
2, we see a controller signal that will operate on an input to the process, known as the ‘manipulated variable’
...
The output may also
be affected by other conditions in the process or by external actions such as changes in supply pressures or in the quality
of materials being used in the process
...

The challenge for the process control designer is to maintain the controlled process variable at the target value or change
it to meet production needs whilst compensating for the disturbances that may arise from other inputs
...

The value of a process model is that it provides a means of showing the way the output will respond to the input actions
...

For example in Figure 3
...
The outflow from the tank passes through a valve with a resistance R to the output flow Q2
...
We know that Q2 will increase as H increases and when
Q2 equals Q1 the level will become steady
...
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Industrial Automation

Process control

Figure 3
...


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4 Elementary block diagram of tank process

3
...
1

Stability

A closed loop control system is stable if there is no continuous oscillation
...
The criteria for stability are these two conditions:
• The Loop Gain (KLOOP) for the critical frequency <1;
• Loop Phase Shift for the critical frequency < 180°
...
2
...

A signal with this frequency is decaying in magnitude, if the gain for this signal is below 1
...


3
...
3

Loop phase shift for critical frequency

Consider the situation where the total phase shift for a signal with that frequency has a total loop gain of 1
...
Increasing the Gain or Phase Shift
destabilizes a closed loop, but makes it more responsive or sensitive
...

The gain of the loop (KLOOP) determines the OFFSET value of the controller; and offset varies with Set point changes
...
2
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Industrial Automation

Process control

• Open Loop
• Feed Forward
• Closed loop
On-Off control: The oldest strategy for control is to use a switch giving simple on-off control, as illustrated in Figure 3
...

This is a discontinuous form of control action, and is also referred to as two-position control
...

Above the SP, the controller is ‘off ’ and the MV is at a minimum
...
5 Response of a two positional controller to a sinusoidal input

Modulating control: If the output of a controller can move through a range of values, this is modulating control
...
That is, it must have upper and lower limits
...
It can be used in both open loop and closed loop
control systems
...
The open loop control does not self-correct, when these PV’s drift
...
It is seen as a form of open loop control as the PV is not used directly
in the control action
...
The principle is shown below in Figure 3
...


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6 The feedback control loop

The idea of closed loop control is to measure the PV (Process Variable); compare this with the SP (Set Point), which is
the desired, or target value; and determine a control action which results in a change of the OP (Output) value of an
automatic controller
...

ERR = PV - SP
If ERR = SP - PV has to be used, the controller has to be set for REVERSE control action
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Industrial Automation

3
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3
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The automatic controller needs to correct the controllers OP, with an action
proportional to ERR
...

Proportional error and manual value: This is called as starting value manual
...
In order to have an automatic correction made, that means correcting from the manual starting term, we
always need a value of ERR
...

Proportional band: Controllers Proportional Band is usually defined, in percentage terms, as the ratio of the input value,
or PV to a full or 100% change in the controller output value or MV
...
3
...
This means that it controls towards no error
(ERR = 0)
...
The combination of both is called as PI-control
...


3
...
3

Derivative control (D)

The only purpose of derivative control is to add stability to a closed loop control system
...

Since the rate of change of noise can be large, using D-Control as a means of enhancing the stability of a control loop is
done at the expense of amplifying noise
...
This results in a PD-Control or PID-Control
...

Formula for D-Control:

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3
...

The following list contains the most important objectives for tuning of a controller:
Minimization of the integral of the error : The objective here is to keep the area enclosed by the two curves, the SP and
PV trends; to a minimum
...
7 Integral on error

Minimization of the integral of the error squared: As shown in Figure 3
...
In such cases, special weight must be given to the magnitude
of the deviation of PV from SP
...
This gives error squared (error squared = error * weight)
...


Figure 3
...
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Industrial Automation

Process control

Fast control: In most cases, fast control is a principle requirement from an operational point of view
...
This quite often results in instability, or prolonged settling
times from the effects of process disturbances
...
In particular, the effects of noise, excessive process disturbances and unrealistically
fast controls have to be considered here
...
If we control an open
tank, we do not want the tank to overflow as a result of overshoot of the level
...
Similar considerations exist everywhere, where danger of some sort exists
...


3
...
1

Continuous cycling method (Ziegler Nichols)

This method of tuning requires determining the critical value of controller gain (KC) that will produce a continuous
oscillation of a control loop
...
The controller gain value
(KC) then becomes known as the ultimate gain (KU)
...
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Industrial Automation

Process control

• A venturi flow meter with a 4-20 mA output feeding into…
• a PID controller which in turn has a 4-20 mA output that controls
...

When the product of the gains of all four of these component parts equals one, the system will become unstable when
a process disturbance occurs (a set-point change)
...

Then measure the frequency of oscillation (the period of one cycle of oscillation), this being the ultimate period PU
...
This gain value, when multiplied with the
unknown process Gain(s), will give a Loop Gain, KLOOP, of 1
...


3
...
3

Damped cycling tuning method

This method is a variation of the continuous cycling method
...

The steps of closed loop tuning (damped cycling method) are as follows:
• Put the Controller into P-Control Only
• Select the P-Control to ERR = (SP - PV)
• Put the Controller in Automatic Mode
• Make a Step Change to the Set point
• Take action based on the Observation
...
5

Cascade Control

If the OP of the temperature controller TC drives the SP of this newly added fuel flow controller FC, then there is a
situation that the OP of the temperature controller TC then drives the true flow and not just a valve position
...
This concept is called ‘cascade control’
...
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Industrial Automation

Process control

Figure 3
...
5
...
Controllers can be set up to make use of PVTracking or not
...


3
...

(temperature controller, TC, in this case
...
If selected,
PV-Tracking can take place in the primary controller as it would occur in normal manual mode
...
7

Feed forward Control

If, within a process control’s feedback system, large and random changes to either the PV or Lag time of the process occur,
the feedback action becomes very ineffective in trying to correct these excessive variances
...

The result of this is that the accuracy and standard of the process becomes unacceptable
...


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8

Manual feedforward control

Here, as a disturbance enters the process, it is detected and measured by the process operator
...

This form of feedforward control relies heavily on the operator and his knowledge of the operation of the process
...


3
...
Feedforward controllers then change the value
of their manipulated variables (outputs) based on these measurements as compared with their individual set-point values
...
These calculations have to take into account all the exact effects that the disturbances will have
on controlled variables
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Industrial Automation

Process control

Pure feedforward control is rarely encountered; it is more common to find it embedded within a feedback loop where it
assists the feedback controller function by minimizing the impact of excessive process disturbances
...
10

Time matching as feedforward control

Time taken for a process to react in one direction (heating) is different to the time taken for the process to return to its
original state (cooling)
...

Normally Lead/Lag compensators as tools are used to obtain equal dynamic behavior
...
A problem of special importance is the drifting away of the PV
...
There are always
factors not accounted for
...


3
...
1 Process dead time
Overcoming the dead time in a feedback control loop can present one of the most difficult problems to the designer of a
control system
...

If the time from a change in the manipulated variable (controller output) and a detected change in the PV occurs, any
attempt to manipulate the process variable before the dead time has elapsed will inevitably cause unstable operation of
the control loop
...
10 illustrates various dead times and their relationship to the PV reaction time
...
10 Reaction curves showing short, medium and long dead times

3
...
The easiest solution is
to “de-tune” the controller to a slower response rate
...


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...

Ziegler and Nichols determined the best way to “de-tune” a controller, to handle a dead time of D minutes, is to reduce
the integral time constant TINT by a factor of D2 and the Proportional constant by a factor of D
...

If, however, we could inform the controller of the dead time period, and give it the patience to wait and be content until
the dead time has passed, then detuning and making the whole process very sluggish would not be required
...


3
...
It is produced by
running the controller output through a model that is designed to accurately represent the behavior of the process without
taking any load disturbances into account
...

• The first represents all of the process behavior not attributable to dead time
...

• The second represents nothing but the dead time and consists simply of a time delay, what goes in, comes
out later, unchanged
...
13

Second term explanation(predicted PV)

The second term introduced into the feedback path is an estimate of what the PV would look like in the absence of both
disturbances and dead time
...

It thus predicts what the disturbance-free PV will be like once the dead time has elapsed
...
11 The smith predictor in use

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Industrial Automation

Advanced Process Control

4 Advanced Process Control
4
...
It is composed of different kinds of process
control tools, for example, model predictive control (MPC), statistical process control (SPC), Run2Run (R2R), fault
detection and classification (FDC), sensor control and feedback systems
...


4
...
2
...

Generally speaking, adaptive control systems have achieved great success in aircraft, missile, and spacecraft control
applications
...

In industrial process control applications, however, traditional adaptive control has not been very successful
...
2
...
Robustness
is usually defined as the minimum requirement a control system has to satisfy to be useful in a practical environment
...

Robust control methods are well suited to applications where the control system stability and reliability are the top
priorities, process dynamics are known, and variation ranges for uncertainties can be estimated
...


4
...
3

Predictive Control

Predictive control, or model predictive control (MPC), is one of only a few advanced control methods used successfully
in industrial control applications
...


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Predictive control is a control
algorithm based on the predictive model of the process
...
It emphasizes the function of the model, not the structure
of the model
...
It calculates future control actions based on a penalty function
or performance function
...
The moving time interval is sometimes called a temporal window
...
If there is a mismatch between the model and process, or if
there is a control performance problem caused by the system uncertainties, the predictive control could compensate for
the error or adjust the model parameters based on on-line identification
...
2
...
Its great success in space, aerospace, and military
applications has changed our lives in many ways
...
The defined objective set is also provided
...
In practice, optimal control is very well suited for space, aerospace, and military
applications such as the moon landing of a spacecraft, flight control of a rocket, and the missile blocking of a defense missile
...
2
...
There are different definitions regarding intelligent
control, but it is referred to as a control Para diagram that uses various artificial intelligence techniques, which may include
the following methods:
• Learning control,
• Expert control,
• Fuzzy control, and
• Neural network control
...


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...

The knowledge base is built by human expertise, system data acquired on-line, and inference machine designed
...
It is not well suited for continuous control
issues
...
It represents knowledge or experience in a mathematical format that process and system dynamic characteristics
can be described by fuzzy sets and fuzzy relational functions
...

Neural Network Control: Neural network control is a control method using artificial neural networks
...
Artificial neural networks are also used as one of the key elements in the model-free adaptive controllers
...
3

Internal Model Control

The Internal Model control (IMC) philosophy relies on the Internal Model principle, which states that “control can be
achieved only if the control system encapsulates, either implicitly or explicitly; some representation of the process to be
controlled”
...
Consider the example shown in the diagram below
...
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Industrial Automation

Advanced Process Control

Figure 4
...
Suppose

G̃p (s) is a model of Gp(s)
...


4
...
1

The IMC Strategy

In practice, however, process-model mismatch is common; the process model may not be invertible and the system is
often affected by unknown disturbances
...
Nevertheless, it forms the basis for the development of a control strategy that has the potential to
achieve perfect control
...
3
...
1 Model Predictive Control(MPC)
Model predictive control, or MPC, is an advanced method of process control
...
The models are
used to predict the behavior of dependent variables (i
...
e
...
In chemical processes, independent variables are most often set points of
regulatory controllers that govern valve movement (e
...
valve positioners with or without flow, temperature or pressure
controller cascades), while dependent variables are most often constraints in the process (e
...
product purity, equipment
safe operating limits)
...
The MPC then sends this set of independent variable moves to the corresponding regulatory controller set
points to be implemented in the process
...
3
...
2 Model Representations
MPC is widely adopted in the process industry as an effective means to deal with large multivariable constrained control
problems
...

This aims at minimizing a performance criterion over a future horizon, possibly subject to constraints on the manipulated
inputs and outputs, where the future behavior is computed according to a model of the plant
...
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Industrial Automation

Advanced Process Control

Predictive Constrained Control: PID type controllers do not perform well when applied to systems with significant
time-delay
...
It
overcomes the debilitating problems of delayed feedback by using predicted future states of the output for control
...
Controller-loop interaction exists
such that the action of one controller affects other loops in a multi-loop system
...
Loops that have single input single output (SISO) controllers may therefore not be suitable for these
types of applications
...

A multivariable controller, whether it be a Multiple Input Single Output (MISO) or a Multiple Input Multiple Output
(MIMO) is used for systems that have these types of interactions
...
The algorithm evaluates multiple process inputs, predicts the direction of the desired control variable, and
manipulates the output to minimize the difference between target and actual variables
...

Dynamic Matrix Control: Dynamic Matrix Control (DMC) is also a popular model-based control algorithm
...
This model is used in parallel with the on-line process
in order to predict future output values based on the past inputs and current measurements
...
Statistical
Control Charts are used to provide an operational definition of a “special cause” for a given process, using process data
...
If the plotted statistic exceeds these limits, the process is considered to be out of statistical control
...

“On-line SPC” is the integration of automatic feedback control and SPC techniques
...


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...
1

Introduction

Data communication involves the transfer of information from one point to another
...
Modern instrumentation is almost wholly concerned
with the transfer of digital data
...
Types of link include copper wire, optical fiber, radio and microwave
...
A modem,
for example, works by using a digital data stream to modulate an analog signal that is sent over a telephone line
...
The word ‘modem’ is derived
from modulator and demodulator
...
e
...
The structure in which devices communicate is known as a protocol
...
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Industrial Data Communications and Wireless

The standard that has created an enormous amount of interest in the past few years is Ethernet
...


5
...

The OSI model reduces every design and communication problem into a number of layers as shown in Figure 5
...
A
physical interface standard such as RS-232 would fit into the layer 1, while the other layers relate to the protocol software
...
1 OSI model representation: two hosts interconnected via a router

The OSI model is useful in providing a universal framework for all communication systems
...
It is anticipated that groups of manufacturers in different areas of industry will
collaborate to define software and hardware standards appropriate to their particular industry
...


5
...
1

Protocols

As previously mentioned, the OSI model provides a framework within which a specific protocol may be defined
...


Figure 5
...
com

Industrial Automation

5
...
The current version of the standard refers to DCE as Data Circuit-terminating Equipment
Figure 5
...


Figure 5
...
3
...
The description encompasses the more generally used full-duplex operation
...
com

Industrial Automation

Industrial Data Communications and Wireless

Figure 5
...
4 shows the operation with the initiating user terminal, DTE, and its associated modem, DCE, on the left of the
diagram and the remote computer and its modem on the right
...
In this case, there
is no RTS/CTS interaction at either end
...


5
...
Fiber optic cables act as waveguides for light, with
all the energy guided through the central core of the cable
...
Little of the energy in the signal is able to escape into the cladding and no energy can
enter the core from any external sources
...


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...
The light ray will then travel through the core of the fiber, with minimal loss in power, by a series of
total internal reflections
...
5 illustrates this process
...
5 Light ray traveling through an optical fiber

5
...
1

Applications for fiber optic cables

Fiber optic cables offer the following advantages over other types of transmission media:
• Light signals are impervious to interference from EMI or electrical crosstalk
• Light signals do not interfere with other signals
• Optical fibers have a much wider, flatter bandwidth than coaxial cables and equalization of the signals is not
required
• The fiber has a much lower attenuation, so signals can be transmitted much further than with coaxial or
twisted pair cable before amplification is necessary

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Industrial Automation

Industrial Data Communications and Wireless

• Optical fiber cables do not conduct electricity and so eliminate problems of ground loops, lightning damage
and electrical shock
• Fiber optic cables are generally much thinner and lighter than copper cables
• Fiber optic cables have greater data security than copper cables

5
...
2

Fiber optic cable components

The major components of a fiber optic cable are the core, cladding, coating (buffer), as shown in Figure 5
...
Some types
of fiber optic cable even include a conductive copper wire that can be used to provide power to a repeater
...
6 Fiber optic cable components

The fiber components include:
• Fiber core
• Cladding
• Coating (buffer)
• Strength members
• Cable sheath
There are four broad application areas into which fiber optic cables can be classified: aerial cable, underground cable,
sub-aqueous cable and indoor cable
...
5

Modbus

Modbus Messaging protocol is an Application layer (OSI layer 7) protocol that provides client/server communication
between devices connected to different types of buses or networks
...
Also note that the Modbus Messaging protocol used with Modbus
Serial is the same one used with Modbus Plus and Modbus TCP
...
e
...
These serve as
indications of the requested services on the server side
• Modbus responses, i
...
the response messages sent by the servers
...
com

Industrial Automation

Industrial Data Communications and Wireless

The interaction between client and sever (controller and target device) can be depicted as follows
...


Figure 5
...
8
...
8 Modbus serial ADU format

Modbus functions can be divided into four groups or ‘Conformance Classes’
...

Conformance Class 0 is the minimum set of useful commands for both controllers and target devices
...

Table 5
...


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...
2 Conformance Class 1 commands

Function Code 7 usually has a different meaning for each PLC family
...
These include,
but are not limited to:

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SETASIGN

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...
3 Conformance Class 2 commands

There are also others such as Function Code 20 (read general reference), Function Code 21 (write general reference) and
Function Code 24 (read FIFO queue) but they are considered to be outside the ambit of this section
...
These include
Function Codes such as 9 (program: Modicon 484), 10 (poll: Modicon 484) and 19 (reset communications
link: Modicon 884/u84)
...
The descriptions use the current rather than the classic terminology
...
4 Modicums addresses and Function Codes

5
...
1
...
It enables the controller to read one or more discrete
inputs in a target device
...
The data field of the response frame consists of a count of the discrete
input data bytes followed by that many bytes of discrete input data
...
com

Industrial Automation

Industrial Data Communications and Wireless

The discrete input data bytes are packed with one bit for the status of each consecutive discrete input
...
e
...
If the
number of discrete inputs read is not an even multiple of eight, the last data byte will be padded with zeros on the high
end
...
Once again
this is not consistent with a big-endian approach
...
e
...
The target device’s response indicates that discrete input 10001 is OFF and discrete
input 10002 is ON (Figure 5
...

• ‘Reference number’ refers to the input discrete with the lowest address
• ‘Bit count’ refers to the number of input discretes (‘number of points’) to be read and can vary between 1
and 2000
• ‘Byte count’ refers to the number of bytes required to return the requested input discrete values and is
calculated as ((bit count + 7) / 8)
‘Bit values’ refer to the actual values of the individual inputs or ‘input data’

Figure 5
...
5
...
It is a LAN system for industrial control
applications, allowing networked devices to exchange messages for the control and monitoring of processes at remote
locations in the industrial plant
...


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...
The
Physical layer is implemented with RS-485 and functions over shielded twisted pair cable
...
This results in transmission of data at 1 Mbps
...
10 Modbus Plus protocol stack

Unlike Modbus, Modbus Plus is a proprietary standard developed to overcome the ‘single-master’ limitation prevalent
in Modbus Serial
...
6

Data Highway Plus /DH485

There are three main configurations used in Allen Bradley data communications:
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It uses a half-duplex (polled) protocol and rotation of link mastership
...
6kbaud
...
6kbaud
...

Note that both systems implement peer to peer communications through a modified token passing system called the
‘floating master’
...
Both systems use a differential signaling system similar
to RS-485
...


5
...
Its main advantage is that it enables the retention of the existing 4-20mA instrumentation
cabling whilst using, simultaneously, the same wires to carry digital information superimposed on the analog signal
...
It uses a
Frequency Shift Keying (FSK) technique based on the Bell 202 standard
...
The average value of the 1200/2400Hz sine wave superimposed on
the 4-20mA signal is zero; hence, the 4-20mA analog information is not affected
...
11 Frequency allocation of HART signaling system

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...
Setting the smart device polling address
to a number greater than zero implies a multi-drop loop
...

The HART protocol has two formats for digital transmission of data:
• Poll/response mode
• Burst (broadcast) mode
In the poll/response mode, the master polls each of the smart devices on the highway and requests the relevant information
...
Although this mode is fairly fast (up to 3
...
The protocol
is implemented with the OSI model using layers 1, 2 and 7
...
8

AS-i

Actuator Sensor-interface is an open system network developed by eleven manufacturers
...
Most of these devices do not
require multiple bytes to adequately convey the necessary information about the device status, so the AS-i communication
interface is designed for bit-oriented messages in order to increase message efficiency for these types of devices
...

Modular components form the central design of AS-i
...

Provision is made in the communications system to make ‘live’ connections, permitting the removal or addition of nodes
with minimum network interruption
...
g
...


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...
9

Industrial Data Communications and Wireless

DeviceNet

DeviceNet, developed by Allen Bradley, is a low-level device oriented network based on CAN (Controller Area Network)
developed by Bosch (GmbH) for the automobile industry
...
DeviceNet is classified as a field bus, per specification IEC-62026
...
The DeviceNet specification is an open specification and available
through the ODVA
...
A single, four-conductor cable (round or flat) provides both power and data communications
...
Reverse wiring protection is built into all nodes,
protecting them against damage in the case of inadvertent wiring errors
...
e
...



...
12 illustrates the positioning of DeviceNet and CANBUS within the OSI model
...
Unlike most other field buses, DeviceNet does
implement layers 3 and 4, which makes it a routable system
...
They share the same upper layer protocols (implemented by CIP, the Control and Information Protocol)
and only differ in the lower four layers
...


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Industrial Automation

Industrial Data Communications and Wireless

Figure 5
...
the OSI model

5
...
It supports single-cable wiring of multi-input sensor blocks,
pneumatic valves, complex intelligent devices, smaller sub-networks (such as AS-i), and operator interfaces
...
It adheres to the OSI model, ensuring that devices from a variety of different
vendors can communicate easily and effectively
...

The bus interfacing hardware is implemented on ASIC (Application Specific Integrated Circuit) chips produced by multiple
vendors, and are based on RS-485 as well as the European EN50170 Electrical specification
...

The number of nodes is limited to 127
...
The message size can be up to 244 bytes of data per node per message (12
bytes of overhead for a maximum message length of 256 bytes), while the medium access control mechanisms are polling
and token passing
...

• Master devices control the bus and when they have the right to access the bus, they may transfer messages
without any remote request
...
e
...
They may only
acknowledge received messages or, at the request of a master, transmit messages to that master
...


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...
11

Industrial Data Communications and Wireless

Foundation Fieldbus

Foundation Fieldbus allows end-user benefits such as:
• Reduced wiring
• Communications of multiple process variables from a single instrument
• Advanced diagnostics
• Interoperability between devices of different manufacturers
• Enhanced field level control
• Reduced start-up time
• Simpler integration
...
This provides the features noted above because of:
• Reduced wiring due to the multi-drop capability
• Flexibility of supplier choices due to interoperability
• Reduced control room equipment due to distribution of control functions to the device level
• Increased data integrity and reliability due to the application of digital communications
...
Three of them correspond to OSI layers 1, 2 and 7
...
The user layer provides a standardized
interface between the application software and the actual field devices
...
12

Industrial Ethernet

Early Ethernet systems (of the 10 Mbps variety) use the CSMA/CD access method
...
Ethernet network interface cards are relatively cheap and
produced in vast quantities
...
However, CSMA/CD
is a probabilistic medium access mechanism, there is no guarantee of message transfer and messages cannot be prioritized
...
From 100BaseT onwards they are capable of full duplex
(sending and receiving at the same time via switches, without collisions) and the Ethernet frame can be modified to make
provision for prioritization and virtual LANs
...

Ethernet technology has, however, made rapid advances over the past few years
...
An indication of this trend is the
inclusion of Ethernet as the level 1 and 2 infrastructure for Modbus/TCP (Schneider), Ethernet/IP (Rockwell Automation
and ODVA), ProfiNet (Profibus) and Foundation Fieldbus HSE
...
com

Industrial Automation

Industrial Data Communications and Wireless

5
...
1 10 Mbps Ethernet
The IEEE 802
...
3) defines a range of media types that can be used for a network
based on this standard such as coaxial cable, twisted pair cable and fiber optic cable
...


5
...
2 100 Mbps Ethernet
100BaseT is the shorthand identifier for 100 Mbps Ethernet systems, viz
...

100BaseT4 was designed to operate at 100 Mbps over 4 pairs of Cat3 cable, but this option never gained widespread
acceptance
...


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One of the limitations of hub-based (CSMA/CD) 100BaseT systems is the size of the collision domain, which is only 250
meters or 5
...
This is the maximum size of a network segment in which collisions can be detected, being
one tenth of the maximum size of a 10 Mbps network
...
As a result, networks larger than 200 meters must be logically interconnected by storeand-forward devices such as bridges, routers or switches
...
The use of bridges and routers for traffic segregation,
in this manner, is often done on industrial Ethernet networks
...

The format of the frame has been left unchanged
...


5
...
3 Gigabit Ethernet
1000BaseX is the shorthand identifier for the Gigabit Ethernet system based on the 8B/10B block encoding scheme
adapted from the fiber channel networking standard, developed by ANSI
...

• 1000BaseSX is the short wavelength fiber version
• 1000BaseLX is the long wavelength fiber version
• 1000BaseCX is a short copper cable version, based on the fiber channel standard
...
1000BaseT is based on a different encoding scheme
...
It uses the same frame format as 10
Mbps and 100 Mbps Ethernet systems, and operates at ten times the clock speed of Fast Ethernet, i
...
at 1Gbps
...

Despite the similar frame format, the system had to undergo a small change to enable it to function effectively at 1Gbps
in CSMA/CD mode
...
This is equivalent to 4
...
Without this increased slot time the collision domain would have
been impracticably small at 25 meters
...


5
...
The Internet (known as ARPANet in its early years),
was part of a military project commissioned by the Advanced Research Projects Agency (ARPA), later known as the
Defense Advanced Research Agency or DARPA
...


61
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...
Although they were developed by different bodies
and at different points in time, both serve as models for a communications infrastructure and hence provide ‘abstractions’
of the same reality
...

Whereas the OSI model has 7 layers, the ARPA model has 4 layers
...

• The OSI session, presentation and applications layers are contained in the ARPA process and application
layer
...

• The OSI network layer maps onto the ARPA Internet layer
...

The relationship between the two models is depicted in Figure 5
...
13 OSI vs ARPA models

TCP/IP, or rather the TCP/IP protocol suite is not limited to the TCP and IP protocols, but consists of a multitude of
interrelated protocols that occupy the upper three layers of the ARPA model
...

As depicted in Figure 5
...
As the message proceeds along the
Internet, this header and trailer could be replaced depending on the type of network on which the packet finds itself be that X
...
The IP datagram itself would remain untouched, unless it has to be fragmented and
reassembled along the way

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...
14 Internet frame

The Internet layer: This layer is primarily responsible for the routing of packets from one host to another
...

The process/application layer: This layer provides the user or application programs with interfaces to the TCP/IP stack
...

Routing: Unlike the host–to–host layer protocols (for example, TCP), which control end–to–end communications, IP is
rather ‘shortsighted
...


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14

Industrial Data Communications and Wireless

Wireless Fundamentals

Wireless communication is the transfer of information over a distance without the use of electrical conductors or “wires”
...
The term wireless technology is generally used for mobile IT equipment
...
Other examples of wireless
technology include GPS units, garage door openers and/or garage doors, wireless computer mice and keyboards, satellite
television and cordless telephones
Wireless communication involves:
• Radio frequency communication,
• Microwave communication, for example long-range line-of-sight via highly directional antennas, or shortrange communication, or
• Infrared (IR) short-range communication, for example from remote controls or via IRDA
...

In the last 50 years, the wireless communications industry experienced drastic changes driven by many technology
innovations
...

Examples of wireless technology at work :
• Security systems
• Television remote control
• Cellular telephones
...
Common examples of wireless equipment in use today include:
• Cellular phones and pagers
• Global Positioning System (GPS)
• Cordless computer peripherals
• Cordless telephone sets
• Satellite television
...
Perhaps the most common use is to connect laptop users who travel
from location to location
...
A wireless transmission
method is a logical choice to network a LAN segment that must frequently change locations
...
com

Industrial Automation

Industrial Data Communications and Wireless

• To span a distance beyond the capabilities of typical cabling
• To avoid obstacles such as physical structures, EMI, or RFI
• To provide a backup communications link in case of normal network failure
• To link portable or temporary workstations
• To overcome situations where normal cabling is difficult or financially impractical, or
• To remotely connect mobile users or networks

5
...
Radio is often selected in
preference to using landlines for a number of reasons:
• Costs of cables and laying can far exceed that of radio telemetry systems
• Radio systems can be installed faster than landline systems
• Radio equipment is very portable and can be easily moved
• Radio can be used to transmit the data in any format required by the user
• Reasonably high data rates can be achieved compared to some landline applications
• Radio can be used as back up for landlines
The various aspects of radio and microwave communications that demand further detail in discussion are listed below:
• Components of a radio link
• Radio spectrum and frequency allocation
• Summary of radio characteristics for VHF/UHF radio telemetry systems
• Radio modems
• How to prevent inter-modulation problems
• Implementing a radio link
• Miscellaneous considerations

5
...
Industrial communications systems do not always respond to the tried and tested approaches
that worked with hardwired inputs and outputs
...
com

Industrial Automation

Industrial Data Communications and Wireless

• High levels of electrostatic/electromagnetic interference on the communications link
• High traffic loads on the link, resulting in intermittent communications
• Electrical surge or transient through the communications system resulting in hardware damage
The impact on the communications system ranges from outright failure (with no communications possible) to intermittent
communications depending on the severity of the problem
...

General comments on troubleshooting: Obviously, there is no cut and dried method of testing
...
However, a few rules are useful in troubleshooting a communications system
effectively
...

• Check grounding and earthing setups
...
com/Mitas
www
...
com

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...

• Use the diagnostics packages provided as part of the system to compare the number of packets transmitted
to packets dropped
...

• Do simple diagnostic tests using simple utilities such as ‘ping’ or ‘netstat’ to identify what is happening on
the network

5
...
1 RS-232
Since RS-232 is a point-to-point system, installation is fairly straightforward and all RS-232 devices use either DB-9 or
DB-25 connectors
...
None of the RS-232 standards define which
device uses a male or female connector, but traditionally the male (pin) connector is used on the DTE and the female
connector (socket) is used on DCE equipment
...
It is often
asked why a 25-pin connector is used when only 9 pins are needed
...
It was originally thought that, in the future,
more hardware control lines would be needed hence the need for more pins
...
16
...
This means that the A and B wires are referenced to each other
...
A ‘zero’ is then transmitted
when the line voltages are reversed
...
Up to 32 devices can be connected on one system without a repeater
...


67
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...
15 RS-485 chip

Note: ProfiBus DP and FMS use RS-485 at the Physical layer and therefore all the RS-485 installation and troubleshooting
guidelines apply
...
16
...
Some common problems related to Modbus installations are listed below
...

• Hardware problems include mis-wired communication cabling and faulty communication interfaces
• Software (protocol) related issues arise when the controller application tries to access non-existent target
devices’ nodes or uses invalid Function Codes, addresses non-existent memory locations in the target
devices, or specifies illegal data format types, which obviously the target devices do not understand
...
16
...
There is no polarity requirement at the node’s transceiver, so the data cable pair may be connected either
way at a node
...
There are limits on the maximum
number of nodes per segment, the number of repeaters, and the lengths of cable segments on the Modbus Plus network
...
This avoids possible
duplicate address problems with other units on the network
...
Other issues are related to the actual configuration
of the communication hardware itself
...
com

Industrial Automation

Industrial Data Communications and Wireless

5
...
5 Data Highway
Data Highway Plus wiring troubleshooting: Inspect the cable closely for wiring problems if the operation of the network
appears intermittent
...

Data Highway Plus network diagnostics: Many of the errors are the result of excessive noise on the network and can
be corrected by examining the actual wiring and removing the source of noise, if possible
...

A few errors (identified in the diagnostics registers on the interface module) worth mentioning are:
• ACK Time out
• Contention
• False poll
• Transmitted messages and received messages
• Data pin allocation
...
ie
...
admissions@ie
...
com

Length: 1O MONTHS
Av
...
In fact,
DH485 is identical to RS-485 while Data Highway Plus is essentially a transformer isolated version
...


5
...
6 HART
Beside the actual instruments that require calibration, the only major problem that can occur with HART is the cable
length calculation
...
This, in turn, depends on:
• The series load resistor
• Cable resistance
• Cable capacitance
• The number and total capacitance of the field devices
• The resistance of, and position of other devices in the loop
The main reason for this is that network must pass the HART signal frequencies without excessive loss or distortion
...
In
addition, it should be confirmed that the loop has a bandwidth of at least 2500 Hz
...


5
...
7 AS-i
The AS-i system has been designed with a high degree of ‘maintenance friendliness’ in mind and has a high level of builtin auto-diagnosis
...
)
• Maintenance related cable errors (counter poling the AS-i cable)
The fault diagnosis is displayed by means of LEDs on the master
...


70
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...
16
...
The first type of problem is of an electronic
nature, where a specific node (e
...
a network interface card) malfunctions
...

The second type is related to the medium that interconnects the nodes
...
Open
and short circuits in the signal path are caused by faulty connectors or cables
...
Signal
distortion and attenuation can be caused by incorrect termination, failure to adhere to topology guidelines (e
...
drop
cables too long), or faulty connectors
...
16
...
Most problems will be experienced at the commissioning phase,
and could theoretically be attributed to the cabling, the LAN devices (such as hubs and switches), the Network Interface
Cards (NICs) or the protocol stack configuration on the hosts
...
This effectively rules out wiring problems
for new installations, although old installations could be suspect
...
Care should nevertheless be taken to ensure that intelligent (managed) hubs and switches are correctly
set up
...


5
...
10 TCP/IP
This section deals with problems related to the TCP/IP protocol suite
...
These
protocols need a network infrastructure as well as a medium in order to communicate
...


71
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...

The easiest way to confirm this, apart from checking the network configuration via the control panel and visually confirming
that TCP/IP is installed for the particular NIC used on the host, is to perform a loop–back test by pinging the host itself
...
0
...
1
...

Other possible problems include:
• A host failing to obtain an automatically assigned IP address
• Reserved IP addresses
• Duplicate IP addresses
• Incorrect network ID – different netIDs on the same physical network
• Incorrect subnet mask
• Incorrect or absent default gateway(s)
• MAC address of a device not known to user
• IP address of a device not known to user
• Wrong IP address
...


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...

Troubleshooting Radio: When troubleshooting an existing system, it is worth checking on a few issues discussed earlier
...


5
...
While low cost desktop
computing brought the power of the digital age to millions of users, the real power of distributed computing has been
unleashed by interconnecting the computers via networks, which made sharing of hardware and data resources possible
...

Integrity: safeguarding the accuracy and completeness of information and processing methods
...


5
...
1 Security in the context of Industrial automation systems
The use of computer based systems for industrial automation is now commonplace
...
A Distributed Control System (DCS) is a higher-end industrial
automation network used for the control of more complex, special purpose equipment and processes
...

• Supervisory Control And Data Acquisition (SCADA) systems, which collect data from geographically
dispersed resources and allow remote monitoring and control usually used in utility systems such a electric
power and water supply
...
17
...


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...

Two other technologies need to be mentioned in this regard
...
Security was not, however, the primary objective of the VLAN; it was rather the need to reduce congestion of
the networks
...
18

Network threats, vulnerabilities and risks

The goal of network security is to prevent an attack on the assets of the target system from succeeding and in case it
cannot be prevented, to minimize the risks due to undesirable consequences
...
” It is not just anyone who can pose a real and
serious threat to a network
...

So we have:
• Threats
• System knowledge
• Motivation
• Vulnerabilities which these threats employ to attack the target assets
• Consequences of attacks
...

Threats from those with adequate system knowledge and the motivation to mount an attack exist
...
That an attack will happen is only a matter of time and should be considered a certainty
...

The assets being protected can include many things, some of them tangible and the others not
...


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...
Trade secrets are essentially intellectual property, which can be stolen or
destroyed, in their physical form
...
Refer to Figure 5
...


Figure 5
...
All these elements need to be present
for an attack on a network
...


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Industrial Automation

Industrial Data Communications and Wireless

A security incident happens when an attacker finds a vulnerability that can be used to break into the system
...
The security incident has to be countered by the security measures (firewalls, encryption etc
...
If these measures fail, the attack becomes successful, opening up the system
and the organization to the risks of security failure, (shown in the innermost circle)
...


5
...
To determine these security policies, one needs to think about the business and examine the risks
...
You need to budget, to find the best way to spread the available
money across the security options - and accept the unavoidable fact that it is not going to be perfect
...
These principles are applicable not
just to business networks as is commonly presumed, but to automation networks as well
...

Connectivity to the Internet by different segments of the organization is quite essential from a business point of view
...
This means that there is a need for connecting Industrial Automation
networks to the business networks and then on to external organizations/services through the Internet
...

All these needs, coupled with the inherent weaknesses in the technologies used make the network administrator’s task
far more complex
...
Many attacks take place from within the organization
...

In fact, security of networks should not be looked at in isolation but should be a subject of a systematic study
...
com

Industrial Automation

5
...
Threats are thus faced by organizations not only from insiders
(those who operate from within the local network) but also from outsiders accessing an organization’s resources through
the Internet
...
Since the Internet
is an untrusted network, the information resources of an organization have to be protected by providing security at the
point of connection to the Internet using a ‘perimeter router’ - the simplest form of firewall
...

Firewalls are also provided to separate the internal as well as external users from important network assets such as the
application servers and other servers providing FTP services, email services etc
...
ACLs can be used to block packets from specified source addresses, packets bound for
specified destination addresses or to indicate that a packet is carrying information of specific interest
...
Using a certain
pre-determined set of rules, a firewall acts as a filter for incoming packets of information
...

Firewalls protect sites from attacks by outsiders who use the inherent vulnerabilities in the TCP/IP protocol suite
...
There are several types of firewalls, from
perimeter routers that can provide access control, to more powerful firewalls that can protect against vulnerabilities in
the TCP/IP protocol, to even more powerful firewalls that can filter packets based on the content of the traffic
...


5
...

The security of any network depends on the control of who can access it and for what purpose
...
It is equally, if
not more applicable to users who access the network from a remote location using public communication media such
as the Internet
...
Authorization defines attributes and privileges of resources, which each user is authorized to access and the
activities that can be legitimately performed
...
Authorization thus provides a method for remotely controlling access where needed
...
com

Industrial Automation

Industrial Data Communications and Wireless

5
...
1 Use of the remote security database
The security information is stored in local security servers forming part of the network being accessed
...
With a very large number
of users, multiple network access servers become necessary
...

A remote security database can make the management of Network Access servers simpler
...


5
...
2 Encryption
Encryption is an important component of data security
...
One way of sending this information is
to instead send a value calculated by a hash algorithm
...

All organizations are wary of sending their data over untrusted or public networks since there is always a possibility of
the data being captured and read or modified
...
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...

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Industrial Automation

Industrial Data Communications and Wireless

Encryption helps in:
• Maintaining data integrity
• Maintaining privacy
• Ensuring that the data is authentic
Encryption refers to the deliberate alteration of data using a key (which is a fixed length string of bits) so that the data is
meaningless to anyone intercepting the message unless he has the key
...
It is essential that both sender
and receiver share the key
...
It is possible to attack an encrypted message (an attempt to decode it) using the
‘brute force’ method through an automated process of trying out all possible key combinations
...
A 128 bit string will take thousands of years of computational time to break by
‘brute force’ method and is therefore considered safe
...

In addition to user authentication, Certification Authorities (CA) also provide digital certificates containing the public key
...
This process of managing public keys is known as the Public Key Infrastructure
(PKI)
...
The use of the PKI is important in situations
that require a non-repudiation feature
...
22

Intrusion detection systems

An intruder is one who attempts to gain unauthorized access to a network
...
An intruder detection system can identify an intrusion
and send alerts to specified users as it is happening so that necessary measures can be taken
...
In the event of the network security devices
failing to stop an attack for whatever reason, an IDS will act as a back-up measure to detect the attack taking place and
initiate a suitable response
...
They are:
• The absence of proper network policies
• Improper system configuration
• Technology weaknesses
...
com

Industrial Automation

Industrial Data Communications and Wireless

Network-based IDSs: Network-based IDSs monitor the network packets flowing through a specific section of the network
to detect an intrusion
...

Host-based systems: In a host-based IDS system, detection agents are deployed on all computers and report intrusions to
a managing agent installed on a central computer
...
Host-based IDSs are not suitable for large networks
...

A response to an attack can be either active or passive
...
Usually, an alarm is by means of a pop-up window on the
administrative console
...
23

VLANs

When a LAN is divided into segments using a switch, with each port serving a smaller number of network nodes, the
chances of collision reduces
...
In some cases, machines that require very
high bandwidth (for example, a server or a high performance workstation) are connected directly to a switch port, thus
enabling them to have almost the entire bandwidth of one segment dedicated to them
...
Product design teams may
be cross functional groups and usually exist for short periods of time
...
In these cases, more packets have to travel from one physical segment (or switch port) to another,
thus increasing the network loading
...

A VLAN logically groups switch ports into workgroups
...

Benefits of a VLAN: VLANs offer a number of advantages over the traditional LAN implementation:
• Performance improvement
• Improved security
• Ability to set up virtual workgroups
• Reduced administration
• Reduced cost
...
com

Industrial Automation

5
...
Since the Internet is a public medium where the traffic
is prone to interception or modification, unlike the privacy offered by dedicated leased circuits, security issues play an
important role in the implementation of a VPN
...


5
...
1 Types of VPN
VPN solutions are essentially of three distinct types:
• Inter-site or inter-LAN VPNs
• Remote access VPNs
• Extranets
While all the three of these types of connectivity are essential from the enterprise viewpoint, most of the savings result
from Remote Access VPN
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Industrial Automation

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• A dial-up Internet connection offers good bandwidth and is therefore becoming acceptable to more users,
particularly those using applications based on client server technology and multi-tier architectures that
conserve bandwidth
• A local dialup connection using a reliable Internet Service Provider (ISP) offers a very high degree of
availability and Quality Of Service (QOS) level compared to direct dial up through long distance lines
...
24
...
A 5-tier
model proposed by the Gartner Group sums up these issues and can be a starting point
...
17
...
17 A 5-Tier model for VPN implementation

The 5 tiers are: security, scalability, manageability, simplicity and quality of service
...
Scalability, manageability and simplicity are functional requirements and will depend on present and
perceived future needs, particularly the issue of scalability
...


5
...

Wireless networks serve as the transport mechanism between devices, among devices and the traditionally wired networks
(such as Enterprise networks and the Internet)
...
Unlike a
traditional LAN, which requires a wire to connect a user’s computer to the network, a WLAN connects computers and
other components to the network using an Access Point (AP), which connects to the wired Ethernet LAN via an RJ-45
port
...
Users move
freely within the cell with their laptop or other portable network devices
...


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25
...
To mitigate these risks, agencies need to adopt security measures and practices that help
bring their risks to a manageable level
...
In
performing the assessment, they should consider existing security policies, known threats and vulnerabilities, legislation
and regulations, safety, reliability, system performance, the life-cycle costs of security measures and technical requirements
...
The security
administrator should periodically reassess the policies and measures in place because computer technologies and malicious
threats are continually changing
...


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1

Introduction

HAZOP stands for Hazard and Operability
...
It
is also finding applications in the planning of operational activities such as emergency response and disaster management
...

For a new facility, ideally a HAZOP workshop would be carried out at the end of the detailed design stage when all P&IDs
have been finalized and issued for detailed design and construction
...
1 HAZOPS should be done when the design is ready for detail engineering

Therefore, in practical terms, the HAZOP workshop is carried out as late as possible in the detailed design stage when
P&IDs are as complete as possible while still allowing sufficient time for HAZOP recommendations to be considered and
incorporated into the design
...
2

HAZOP Workshop

In preparation for the HAZOP workshop, the facilitator will have agreed with the client/project on:
• Terms of reference
• Documents required
• Team membership and availability
• Team Structure
• Team attitudes
• Estimated duration of workshop
• Venue for workshop meetings
• Reporting method

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...
2
...
The
IEC 61882 standard describes the study leader’s skills and duties as follows
...

• Conduct the study
• Ensure the results are documented
Who is in the team?
In addition to the team leader the essential players are:
• Recorder or “scribe”
...

• Project engineer (may also be designer)
...

• Instrument/control engineer
...

• Contractor and Client representatives
...
2
...


6
...
3

Quality HAZOP Reports

Reporting: Depending upon the client/project, the required format of the report may vary
...


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2
...
The task of Hazard analysis includes
...

• Estimating the consequences to persons, environment and plant
...

Two methods of hazard analysis are widely used
...

Fault tree analysis: looks at a hazard event and resolves the causes into basic events
...
2
...

Policy Issues: Additional issues that must be considered for a complete evaluation of the benefits and costs of food safety
risk reductions relate to information, public versus private intervention, accurateness of illness estimates, marginal benefitcost analysis and efficiency in production
...
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Industrial Automation

Safety Instrumentation and Machinery

7 
Safety Instrumentation and
Machinery
7
...
The successful implementation
of a safety system project depends on the support and knowledge of other disciplines as well as being dependent on a full
commitment from company management structures
...
Without proper support structures and a good understanding by all involved in defining safety
requirements the safety instrumentation on its own will be unlikely to deliver the levels of safety that are expected of it
...
It is the responsibility of the instrument engineer to involve colleagues from other disciplines in the safety
package
...


7
...
1

Safety system basics

7
...
1
...
They perform “safety instrumented functions”
by acting to prevent the hazard or mitigating the consequences
...
These are terms generally used in engineering standards
...


Figure 7
...
” In other words safety depends on the correct functions being
performed
...
It is a
useful term because it distinguishes the active safety system, in its range of uses, as a system that must function properly
to provide safety
...
com

Industrial Automation

Safety Instrumentation and Machinery

7
...
1
...
2 Structure of a Safety Instrumented System

Figure 7
...
Items within the boundary must be engineered
to the standards required for functional safety systems
...


7
...
2

Risk reduction and safety integrity

There is a common saying in the control systems world: “if you want to control something, first make sure you can
measure it
...
Therefore, Risk
is to be measured before controlling it
...
1
...
1 Measurement of risk
Risk can be evaluated qualitatively or quantitatively
...
These terms are only effective if everyone has a good understanding of what they mean in
the context of use
...
If the terms are well defined
or “calibrated” against a scale of values that is generally accepted the qualitative risk measurement can be very effective
...


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...
1
...
2 Safety integrity
The degree of confidence that can be placed in the reliability of the SIS to perform its intended safety function is known
as its “Safety Integrity”
...
One of these aspects will be the hardware reliability of the equipment and the
way it responds under all conditions
...
1
...

This will enable us to see how the SIL target can be adjusted to provide best overall value from the plant safety systems
...
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Belt and braces

Figure 7
...
Essentially, this concept identifies “belts and braces” involved in providing protection against
a hazardous event or in reducing its consequences
...
shows the concept where the core risk, due to a hazard, is
seen to be contained by successive layers of protection leaving a minimal or acceptable risk level at the outside boundary
...
For a SIS to be effectively designed and implemented, the following key aspects of a SIS project will have to be assured
...
1
...
Understanding risk management will show us how the application of Safety Instrumented Systems
is an integral part of the overall task of managing risk in a company
...
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Industrial Automation

Safety Instrumentation and Machinery

The meaning of safety management: Safety management involves the provision of a safe working environment for all
persons involved in the manufacturing process
...

The fundamental components of safety management will include:
• Having a systematic method of identifying and recording all hazards and risks presented by the subject plant
or equipment
• Ensuring that all unacceptable risks are reduced to an acceptably low level by recognized and controllable
methods that can be sustained throughout the life cycle of the plant
• Having a monitoring and review system in place that monitors implementation and performance of all safety
measures
• Ensuring all departments and personnel involved in safety administration are aware of their individual
responsibilities
• Responding to regulatory requirements from national and local authorities for the provision of adequate
safeguards against harm to persons and the environment
...
Safety management is effectively the same as the more general term, risk management, but applied
specifically to risks associated with harm to persons, property or environment
...

Managing risk
• Requires rigorous thinking
...

• Encourages an organization to manage pro-actively rather than reactively
...

• Requires balanced thinking “Recognizing that a risk-free environment is uneconomic (if not impossible) to
achieve, a decision is needed to decide what level of risk is acceptable”
...

Conclusions from risk management: We have seen how the generalized models for risk management are directly applicable
in safety management
...
The selection of measures involves balancing the level
of safety achieved against the cost of achieving it
...
com

Industrial Automation

Safety Instrumentation and Machinery

When we look at the new application standards for Safety Instrumented Systems it is easy to recognize the same principles
being applied
...


7
...
5

The legal framework for process safety

Most industrialized countries have legal frameworks in place that are similar in nature and have been substantially improved
in recent years
...
This aims to deal
with the fact that many accidents can be traced back to failures to manage the various aspects of safety from identification
of hazards through to training and continued monitoring of safety performance
...
The most
commonly seen principle is that all potentially hazardous activities must be subject to a risk assessment process
...
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Industrial Automation

Safety Instrumentation and Machinery

In the case of process industries, plants having a known hazardous process or having major accident potential are required
to develop a comprehensive safety case for inspection by authorities
...
They are required to carry out process hazard analysis studies at frequent intervals to ensure
the plant risk assessments and treatment methods are up to date with the current version of the plant
...
1
...


Figure 7
...
Which one is to be used?

Figure 7
...
The safety equipment products bought from a system supplier or instrument
vendor should be engineered in accordance with IEC 61508
...


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...
Perhaps the most significant
feature to note is that conformity to this standard requires both technical items and the overall management of the safety
project to be in compliance with the mandatory parts of the standard
...
The standard covers electrical, electronic and programmmable electronic systems and lays down standards
of engineering and quality assurance for both hardware and software
...
However it is of great value to both
manufacturers and end users and despite some criticisms of its complexity, it has been adopted by many large processing
companies as their standard reference for design and operation of Safety Instrumented Systems
...
1
...

The safety life cycle is an orderly sequence of design and builds stages with each activity being mapped out with essential
requirements that must be satisfied at each phase
...
Figure 7
...


Figure 7
...
The hazard study
identifies hazards and a hazard analysis leads to the estimation or ranking of risks
...
As this
stage progresses, the project team will continue to carry out verification exercises to ensure that the design remains true
to the SRS and that the SRS remains true to the hazard studies
...
com

Industrial Automation

Safety Instrumentation and Machinery

Before the SIS enters service, it will be subjected to a rigorous validation exercise that involves testing of the functions
against the details defined in the SRS
...

Change management procedures remain in force throughout the safety lifecycle and any recorded changes are recycled
back through the relevant design and testing stages
...


7
...
8

Introduction to safety PLCs

Safety PLCs have become the dominant form of logic solver in the past 10 years through their ability to provide shared
logic solver duties for many safety functions within one SIS
...

Safety PLCs are specially developed for their tasks through the provision of extensive diagnostic coverage using internal
testing signals operating between scanning cycles of the application logic
...

The software of a safety PLC is specially developed to have a range of error detecting and monitoring measures to provide
assurance at all times that the program modules are operating correctly
...


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Industrial Automation

Safety Instrumentation and Machinery

One major objection to safety PLCs has been their cost and this is particularly a problem for small plant applications
...


7
...
9

The cost of ownership

Having discussed something of the project activities and some technical aspects of safety system, it may be helpful to
consider the issues of cost and justification for installing an SIS
...

From the management perspective, it will be essential to have a measure of the costs involved in buying, maintaining and
operating a safety system
...
It will help to have an approximate cost model that can be used as a basis
for establishing the total costs involved in SIS
...


7
...
The main steps are:
• Identification of plant scope and its hazards
• Evaluation of any risks to determine risk reduction needs
• Allocation of risk reduction duties to SIS and non-SIS layers of protection
• Development of the safety requirements specification
• The building and testing of the SIS to specification (known as the realization phase)
• Installation and testing of the SIS
• Operation and maintenance of the SIS
• The managing of changes to the SIS design or equipment
Each phase of the lifecycle requires input information and delivers output information
...

IEC 61508 offers a safety lifecycle model that will serve any project and many companies may elect to use this version for
their applications
...


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...
2
...
Box numbers are
used to reference a detailed set of clauses defining the requirements of the standard for that activity
...
7 IEC 61508 SLC version

Developing the overall safety requirements: The first 4 phases deal with the tasks of defining the scope of the plant,
identifying hazards and risks and deciding the overall safety requirements
...

Safety allocations: Once the overall safety targets have been established, the SLC moves on to the “Safety Allocations”
phase where the various layers of protection are defined and allocated a certain portion of the risk reduction task
...

Realization phase: These stages are followed by the “realization” phase
...
Large sections of IEC 61508 are concerned with the
details of the realization phase and there are whole lifecycle models for the activities contained within this stage
...
com

Industrial Automation

Safety Instrumentation and Machinery

Validation and operations: Once the SIS has been built, the lifecycle activities move on to the “installation, commissioning
and validation”
...
This activity is seen particularly in the form of the
final site acceptance testing using methods that test the SIS response under plant operating conditions in the most realistic
way possible
...


7
...
2

IEC 61511 SLC Version

Shown in Figure 7
...
Comparing this version with the 61508 model, we can see that the tasks
have been grouped into more familiar sets of activities that will match up easily to the natural progression of a process
safety project
...
8 IEC 61511-safety lifecycle model

Phase 1: Hazard and risk assessment
The model refers us to Clause 8
...

The first phase of the SLC delivers a sound basis of information about the hazards and records assumptions made about
the risks
...

IEC 61511 does not set out to provide detailed requirements for the hazard and risk assessment phase
...


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...

The objectives of this phase are to:
• Allocate safety functions to protection layers
• Determine required safety instrumented functions (SIF)
• Determine the associated SIL for each SIF
The requirements clause requires us to identify all risk reduction measures and define each Safety Function (SIF) with
its own SIL
...
This phase with the preceding two included is known in IEC 61511 as “Stage 1”
...
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Safety Instrumentation and Machinery

SIS design and engineering: clauses 11 and 12
The requirements of this section comprise all the essential design constraints that the standard mandates
...

Clause 12 describes the requirements for the application software engineering and includes selection criteria for the
utility software
...
The specially restricted versions used in
safety PLCs are described here as “Limited Variability Languages “or LVLs
...
Completion of the design and engineering activities is also known in the standard as “Stage 2”
...

SIS Installation, commissioning and validation: clauses 12
...
Clause 12
...

After installation, Clause 14
...
3 outlines the commissioning requirements in terms of essential features that must be
checked
...

Clause 15 then describes the essential requirements for safety validation
...
Validation is of critical importance to safety system installations because it is the only way of knowing
that the final result of the design and building effort can provide the required safety
...

SIS operation and maintenance: clause 16
This phase covers the operating life of the SIS on the plant
...
The objectives are to ensure that the required SIL is maintained during Operation and
Maintenance (O&M) and conversely to see that maintenance is adequate to keep the SIL at its intended level
...

SIS modifications: clause 17
The objectives of this phase, defined in clause 17, are: “those modifications to any safety instrumented system are properly
planned, reviewed and approved prior to making the change; and to ensure that the required safety integrity of the SIS is
maintained despite any changes made to the SIS
...
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Industrial Automation

Safety Instrumentation and Machinery

The completion of a modification activity is also known as “Stage 5”
SIS decommissioning: clause 18
This phase is similar to the modification phase because it requires an impact analysis on the effects on safety of decommissioning
...
7
Clause 7 of IEC 61511 details the requirements for verification, which is essentially aimed at establishing that each phase
has been completed properly and that the results are verified to be in accordance with the objectives of that phase and
is traceable to the input information
...
Clause 5 of IEC 61511 discusses these requirements
...


7
...
The design process is
concerned with finding suitable instruments in an independent SIS loop that has a structure or architecture appropriate to
the SIL reliability targets
...
If the
instrument is good, there is less need of redundancy for safety but this choice has to be made within a framework of rules
...
3
...
Figure 7
...
The
preliminary evaluation of these points can be done at the concept stage and these points should be confirmed before the
final design
...
com

Industrial Automation

Safety Instrumentation and Machinery

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...
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Industrial Automation

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Figure 7
...
We will consider one of the ways in which hardware
design can be developed to minimize the hardware failures
...


Safety reliability versus availability for production
Functional safety is achieved by the SIS doing the safety job and when failures occur, the system must act in a manner
that still ensures safety
...
e
...
For a single channel SIS,
this usually means shutting down the process even if it is only for the reason that the safety system has found a fault
...

What is desired is a plant where safety is achieved at a reasonably economic cost
...


7
...
3

Architectures and fault tolerance concepts

Fault tolerance is one of the most important underlying principles of all safety systems whether used in chemical plants,
machinery, automobiles or in business planning
...

7
...
3
...

Dangerous detected failure: If the dangerous fault can be detected by some method of diagnostic testing or by the way
the circuits are arranged, it will be known as a “revealed” or “overt” fault
...

Safe failure: Conversely this is a failure that “does not have the potential to put the safety instrumented system into a
hazardous or fail-to-danger state
...

Safe detected failure: Some safe failures may not be revealed by causing a trip but they may be detected by other means
such as a diagnostic test
...
Where redundant instruments of the same design or the same
principles are used, the likelihood of common mode failures can be in the range 5% to 20 % of all failures
...


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...
Hence a fault tolerance level of 1 means that a single dangerous
fault in the equipment will not prevent the system from performing its safety functions
...

Safe failure fraction: This parameter is vitally important for the safety integrity or confidence level and it will determine
if greater levels of fault tolerance has to be built into a given application
...
3
...
See Figure 7
...
It is not
always as simple as identifying the instruments and the valves or motors because the signal transmission and conversion
devices will also fall into the sensor and actuator subsystem
...


Figure 7
...
Because they are working
in series, any failure of a sub-system will contribute to the failure of the overall SIS
...


7
...
4
...
They are supported by the wiring and process
connection arrangements
...
They are also
the area where most engineers have a chance to exercise their skills and judgment in design, selection and maintenance
...
com

Industrial Automation

7
...
2

Safety Instrumentation and Machinery

Sensor types

Sensors are devices that can represent the value or status of a chosen parameter in a form suitable for decision-making
in the SIS logic solver
...
11
...
11 Categories of sensors

There are two basic categories of sensors: switches and transmitters that are discussed below
...

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Such a list also helps to identify ways in which the EUC control system can fail and create
a hazardous event
...
4
...
The devices used by the SIS to actuate the protective function should more correctly
be called final elements
...
Or they are simply motor
starter contactors that must be de-energized to break the power supply to the drives that must be tripped
...
These applications require backed up (i
...
redundant) power supplies to operate heavy-duty power
isolating contactors or to drive motorized valves
...

In all cases there must obviously be a high degree of assurance that the final element will do the job when called upon to
act
...


7
...
4

Guidelines for application of field devices

The application of any measurement and control device for duties in a safety instrumented system must take into account
two primary considerations:
• The device must be applied using the best design techniques to minimize failures
• The device should meet the design requirements of IEC 61508 or IEC 61511
Given the diversity of failure modes, the design techniques required to minimize the fail-to-danger rate will be application
dependent
...
Then
review spurious trip rates to see if they are acceptable
...
com

Industrial Automation

Safety Instrumentation and Machinery

Separation: Ensure separation between BPCS and SIS sensor/actuator systems as far as practicable
...

Redundancy: Use redundancy where a reduction in fail to danger rate is needed or where a low spurious trip rate is essential
...

Armed with the knowledge of failure possibilities and knowing the redundancy rules we should now be ready to specify and
select particular types of instruments for any given application
...


7
...
5

Instrument selection

The IEC standards do not attempt to dictate what instruments to use
...

The selection is almost entirely dependent on the application; hence it is not practicable to list any hard and fast rules about
what instruments to use
...

Flow meters
• Vortex Shedding and Magnetic Flow meters are preferred due to proven performance
• Head-type flow measurements are to be avoided, if possible, due to impulse line problems – leakage,
condensation, freezing and drift
Temperature sensors
• RTD and Thermocouple types: require burnout detection and alarm
• Be careful to locate sensors properly
• Ensure probes are seated in thermo wells
• Avoid thermistor types
• Infra red types with diagnostics
Pressure
• Gauge, differential pressure and absolute pressure types are very reliable
• Ensure range and trip setting are compatible
• Ensure impulse lines do not risk condensate build up or blocking
• Use remote diaphragm seals instead of long leg links, but: beware of drift; beware of vacuum effects on
diaphragms

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Industrial Automation

Safety Instrumentation and Machinery

• Proximity switches available with diagnostics
• Check leakage currents in OFF state to avoid false ON condition at SIS
Selection factors
• Material compatibility
• Shut off duty, shock loadings, leakage, fire resistance
• Speed of response
• Element types most used are: Ball, Gate, and Globe
• Butterfly valves used on air systems, large sizes
• Spring/actuator performance margins
...

It is important for keeping the safety integrity of field devices in order that details of the installation do not lead to
accidental malfunctions
...
Hence segregation of shutdown system wiring and special identification are features that
will repay the extra effort involved
...
4
...


The two items that have a major

impact on field devices are instruments with self-testing diagnostics and bus communications
...


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Self-testing and safe responses to faults will help increase the safe failure fraction of a field device
...
Firstly, there are the general reservations about the risks of programmable
systems in safety applications
...

One of the main purposes of IEC 61508 and IEC 61511 was to address these types of issues and find ways of dealing with
them
...
In brief, the answers to the above
possible problems are:
• Instruments using PES should be manufactured using hardware and software engineering procedures in
accordance with IEC 61508
• Limited ranges of software instructions should be made available to the end user to program the instrument
within a tested range of configurations
• The program of the instruments should be password protected
Unless the above requirements are met, the fault tolerant rating of the instrument is loaded down by comparison with a
non-PES version (see Redundancy section)
...
5

Selection of safety controllers

The logic solver stage of an SIS is where all the decisions are made to execute the safety function
...
For example, a
high-pressure trip switch connected directly to a solenoid valve releasing a shut off valve
...

Traditionally, relay systems have been used for the logic function and these remain an attractive option for simple
applications
...
The need for interfacing to the operator increases
and often there is a linkage between one trip function and another
...
There is a need to be sure that all logic functions
perform in such a way that start up and other plant operations interact smoothly with trip systems - the sophistication
of the safety function begins to increase
...


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The new standards addressed
many of the potential problems of using basic PLCs for safety and have delivered a range of requirements that are usually
satisfied by the specially designed safety PLCs
...
Rather
than declare these PLC’s unacceptable, it has made provision for these to be used with the safeguards being well defined
...
This
chapter outlines the operating principles of various types of logic solver, which should assist, with the initial steps of
selecting the type and scope of logic solver to be used for the project
...
6

System integration and application software

The objective of this module is to provide some guidance on how to deal with the application software stages of a SIS
project
...

As soon as PLCs began to appear in safety systems, the specialists realized that there was a great danger that systematic
design errors could be introduced into the logic solver through problems with operating systems and through errors in
the application logic
...

Unacceptable in a safety system is an unpredictable response to a hazard demand
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Industrial Automation

Safety Instrumentation and Machinery

IEC 61508 was the first major standard to lay down basic concepts and requirements for the control of systematic errors
in software for safety applications
...
The impact of this approach
is found in the availability, for end users, of certified operating systems supported by certified programming packages
...
IEC 61511 has provided a more
practical set of requirements and guidance notes designed for the application stage of a safety project while still following
all the essential requirements of IEC 61508
...
7

Programming tools

For most process plant applications, the engineer will require access to a configuration package supplied as part of the
PES solution package
...

It is a fundamental requirement of a safety certified PLC that the integrity of the whole software package is assured
...

IEC 61511 part 2 describes the programming and support tools as “the developers’ workbench”
...
12 Programming tools

Tasks
• Configures logic solver I/O and communication subsystems
• Programs the logic and arithmetic functions of the application
• Facilitates testing of applications

7
...
Machines are part of our lives
and our safety is dependent on the machines being safe for us to use at all times
...
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Industrial Automation

Safety Instrumentation and Machinery

The following are the aspects that show how a machine should be made safe
...
No chance of it falling on
someone
...
No chance
of explosions or radiation
...
If there’s a risk that this can
happen, then protection measures are required; fixed guards, movable guards, area sensing devices that stop
the machine quickly if someone is in the danger zone
...

• Functionally safe: All the stops switches, guards and safety sensing devices are there to protect us must
function properly
...

Safety measures based on sensors and control systems that are designed to ensure safe working of the machines are also
known as Safety-Related Electrical Control Systems (SRECS)
...
8
...
The machinery safety system may also provide protection for the
machine itself or other machines against damage due to malfunctioning of the machine
...
These prevent a person from being hurt by the machine, but in many
cases the situation will require a logical action from the control system to prevent movement or other physical events from
happening until safe conditions are proved to exist
...
Those parts of the basic control system, as well as any specially provided safety parts, are known
as the “safety related parts of the control system”
...
In other words; the sensors, logic or evaluation
units and the final drive interlocks and contactors or valves all belong to the safety control system
...
(SRECS)
...
8
...
(SIS) or emergency shutdown system
...

• Machinery safety systems have been traditionally defined for performance by “safety categories” but will in
future be moving to the same basis of SILs for complex and/or programmable safety systems
...
com

Industrial Automation

Safety Instrumentation and Machinery

• Process plant safety is subject to different regulations and design standards from those applicable to
machinery safety, but the basic principles are essentially the same
...

• Is the hazard coming from the process or from the machine?
• Which regulations are applicable?
• What design standard shall we apply?
If the hazard is due to the process, the plant safety systems can deal with it
...


7
...



...

• Safe Manufacture – this includes design and installation of plant and equipment
...


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© Deloitte & Touche LLP and affiliated entities
...

Essentially, the safety of machinery must be tackled from two sides:
• The manufacturers and suppliers must build machines that are safe to use
• The users of machines (i
...
employers and workers) must ensure the machines are used in a safe manner and
the workplace environment is safe for the workers
...

• Secondary sources - comprising of regulations, directives and decisions
...

• Non-legally-binding - sources-opinions and other non-treaty acts (such as guidelines, resolutions,
communications etc
...

These include:
• Mandatory essential provisions, which apply to the product
...

• The manufacturer is provided with the opportunity to certify conformity with the relevant directives
...

• Legislation no longer specifies that specific standards have to be met
...

• The manufacturer achieves conformity by compliance with a national law or regulation
...

The CE mark is the characteristic symbol shown in the Figure 7
...


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13 The standard CE mark signifying a claim to conform to relevant directives

The products, which come under European Directives, and are to be placed on the market in the EU, must bear CE marking
as it is a legal requirement
...
The CE mark shall be distinct, visible, legible
and indelible
...
9
...
9
...
1 Type A Standards – Basic Standards
These provide essential information for all machine builders
...
This defines the
way standards are to be written
...
This defines the
concepts of machine safety and specifies the general principles and techniques to help machine designers
achieve safety
...
This defines how to assess the risk of injury
or damage to health, so that appropriate safety measures can be selected
...
9
...
2 Type B Standards – Group standards

B standards are subdivided into two groups,
• Group B1: These cover higher-level safety aspects for design and are always applicable
...
g; ergonomic
design principles, safety distances from potential sources of danger, minimum clearances to prevent crushing
of body parts
...
These are applied when
required
...
g; emergency stop equipment, two-hand controls, interlocking/ latching, non-contact protective
devices, safety-related parts of controls
...


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This is the standard that defines our
control system functions into safety categories such as 1,2, 3 or 4
...

7
...
1
...
These inform machine
manufacturers and users about the specific safety precautions they should take and safety devices they should use
...
g
...


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Industrial Automation

Hazardous Areas and Intrinsic Safety

8 
Hazardous Areas and Intrinsic
Safety
8
...
Causes can be accidental or deliberate, but unless structures have been built to safe fire standards, and sound
emergency procedures are used, heavy loss of life can result
...

Other Explosions: Great loss of life occurred in Halifax, Nova Scotia, Canada in 1917 when a ship carrying explosives
collided with another
...
One of the worst non-mining explosions occurred in 1974 at the Mt St Candice Convent in Hobart, when
seven died in a boiler explosion
...
The resulting deadly cloud
caused the deaths of approximately 2,000 people living close-by
...
6 million litres of chemicals in the heart of Melbourne and loomed as a potential disaster
...
These may also include the use of electrical equipment
in the vicinity of water, the risk of personal injury from moving or falling parts, or even the presence of biological hazards
...
com

Industrial Automation

8
...
1

Hazardous Areas and Intrinsic Safety

Basis of area classification

The first step in Area Classification is to list and identify the areas in the plant where there is the possibility of a conducive
atmosphere for explosion or fire to occur
...

It is useful to understand what a Non-hazardous (safe) Area is
...
It is also called a “safe
area” and includes most control rooms
...
Each installation will be different in some respect and therefore
each site must be examined on its individual merits
...
e
...

• A situation where explosive atmosphere occurs frequently, or if infrequently may persist for a considerable
time, i
...
primary
...
e
...

The above criteria are used in classifying the areas under ‘Source of Release’ methodology of classification
...
2

Zonal Classification

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...
2
...
Zones are
classified as shown in the table below
...
This is as per IEC 79:

8
...
2

Dusts

In respect of dust, the situation had been much more fluid
...


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In carrying out an area classification, it is necessary to:
• Identify those parts of the plant where flammable dust can exist including, where appropriate, the interior of
process equipment
• Assess the likelihood of occurrence of a flammable atmosphere thereby establishing the appropriate zonal
classification
• Delineate the boundaries of the zones taking into account the effect of likely air movement
• Take into account, when assessing the area classification of a plant, the influence of the classification of
adjacent plants

8
...
1 Area classification

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...
3
...


8
...
2

Sources of release

The basic elements for establishing the hazardous zone types are the identification of the source of release and the
determination of the grade of release
...

If it is established that the item may release flammable material into the atmosphere, it is necessary, first of all, to determine
the grade of release in accordance with the definitions, by establishing the likely frequency and duration of the release
...


8
...
3

Type of zone

The likelihood of the presence of an explosive gas atmosphere and hence the type of zone depends mainly on the grade
of release and the ventilation
...


8
...
4

Extent of zone

Consideration should always be given to the possibility that a gas which is heavier than air may flow into areas below
ground level for example pits or depressions and that a gas which is lighter than air may be retained at high level, for
example in a roof space
...

Release rate of gas or vapor: The greater the release rates the larger the extent of the zone
...
com

Industrial Automation

Hazardous Areas and Intrinsic Safety

• Geometry of the source of release
• Release velocity
• Concentration
• Volatility of a flammable liquid
• Flashpoints of flammable liquids
• Liquid temperature
...

Ventilation: With increased ventilation, the extent of the zone will be reduced
...

Relative density of the gas or vapor when it is released
• The horizontal extent of the zone at ground level will increase with increasing relative density and the
vertical extent above the source will increase with decreasing relative density
...
3
...
The grade of release will depend upon:
• The zone type of the adjoining area
• The frequency and duration of opening periods
• The effectiveness of seals or joints;

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Industrial Automation

Hazardous Areas and Intrinsic Safety

Openings are classified as A, B, C, and D with the following characteristics:
• Type A: Openings not conforming to the characteristics specified for types B, C or D
• Type B: Openings that are normally closed (for example automatic closing) and infrequently opened and
which are close fitting
• Type C: Openings normally closed and infrequently opened, conforming to type B, which are also fitted with
sealing devices
• Type D: Type D openings are effectively sealed, such as in utility passages (for example ducts, pipes) or can
be a combination of one opening type C adjacent to a hazardous area and one opening type B in series
...
3
...
e
...
Two main types of ventilation are thus recognized:
• Natural ventilation
• Artificial ventilation, general or local
...
4

Methods of explosion protection

When electrical equipment is to be located in a hazardous area it must be designed manufactured and certified for that
purpose
...

The zonal classification of the hazardous area that the equipment is to be located in will, or partially, determine the
equipment’s method of protection
...
Care must be
taken not to confuse the term ‘explosion protected’ with the North American term of ‘explosion proof ’ used to describe
their hazardous area equipment
...

Each technique of protection is assigned a code letter depicting the type of protection
...
4
...

Pressurized (Ex ‘p’) - if clean dry air or an inert gas is pumped into an enclosure housing electrical equipment and a positive
pressure is maintained at 50Pa with respect to the surrounding atmosphere then flammable gas or vapour will be excluded
...


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E
...
and to reduce the temperature
of electrical equipment by airflow passing over the equipment
...


8
...
2

Prevention of sparking (criterion b)

This involves selecting components or equipment that will not provide a source of ignition when in normal use
...
The design and manufacture of this equipment
assures safety against ignition through ensuring that the temperature of the equipment will not become excessive and that
the incidence of arcs and sparks in normal service is prevented
...


8
...
3

Explosion containment (criterion c)

If a gas / air or vapour / air mixture manages to enter an enclosure that contains electrical equipment and that mixture
is ignited then this enclosure must be robust enough to contain the explosion and ensure that the escaping products of
the explosion do not cause ignition outside of the enclosure
...


8
...
4

Energy limitation (criterion d)

This involves the limitation of energy into a hazardous area so that there is insufficient energy allowed into the circuit to
cause ignition
...
With intrinsic safety, there is always the need for a certified interface unit such as a Zener barrier
or galvanic coupler to couple the supply from the safe area to the intrinsically safe equipment in the hazardous area
...
5

Flameproof concept Ex d

This method is also widely used along with the equally popular Ex ‘e’ concept
...
If a gas / air or vapor / air mixture enters the enclosure in sufficient quantities and ignites,
the enclosure will contain the effects of the ignition
...


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5
...

A flameproof enclosure is defined in the standards as: ‘An enclosure for electrical apparatus that will withstand an internal
explosion of the flam­ able gas or vapor which may enter it without suffering damage and without communicat­ng the
m
i
internal flammation to the external flammable gas or vapor for which it is designed, through any joints or structural
openings in the enclosure’
...
Where there is a joint, however, or where a spindle or shaft passes through the
enclosure, the products of the explosion can escape
...
The misconception that it should be ‘gas-tight’ is misplaced
...
On the other hand, it is not the aim to require joints to be deliberately spaced to give an opening
...

Length of Flame Path: The shortest path traversed by a flame through a joint from the inside to the outside of an enclosure
...
ie
...
admissions@ie
...
com

Length: 1O MONTHS
Av
...

Pressure Piling: A condition of rise in pressure resulting from ignition of pre-compressed gases in compartments or
subdivisions other than those in which ignition was initiated and which may lead to a higher maximum pressure than
would otherwise be expected
...


8
...
2) analogy can be used to explain the objective of Intrinsic Safety
...


Figure 8
...

An IS circuit is defined in Standard IEC 60079-11 as:
“A circuit in which any spark or thermal effect produced in the condition specified in this international standard, which
include normal operation and specified fault conditions is not capable of causing ignition in a given explosive gas
atmosphere
...
com

Industrial Automation

Hazardous Areas and Intrinsic Safety

The standard repeats and qualifies this where it declares that three basic criteria must be satisfied;
• Separation from other circuits
• Temperature classification; and
• The inability to cause ignition by sparking
...
These criteria and the requirement for separation from other circuits provide
the high integrity necessary
...
Electrical energy can only produce heat or sparks when electricity
is flowing
...
The components of
the circuit do not pose a threat unless electricity is passing through them, in which case they must be part of a ‘circuit’
...

A ‘circuit’ can mean any of the following arrangements, increasing in complexity:
• A single cable looped through a hazardous area
• An assembly of electrical components working together as an electronic device (such as an instrument)
• A number of assemblies can be interconnected in the same circuit
...
Under probable fault conditions
acting within or onto the circuit, the circuit must still not be able to emit heat or sparks in sufficient quantities to cause
ignition where it encounters a hazardous area
...

The possible ‘faults’ are predicted by careful examination of what failure mechanisms could occur
...
These
components are termed, ‘safety components’ and are in-built into the operation of the circuit
...


8
...
It is generally
denoted by adding suffix ‘e’, i
...
, Ex ‘e’
...


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The aim of this type of protection is to avoid the occurrence of ignitable sparks
and thus have a distinctly higher degree of safety compared with conventional electrical apparatus
...
No switches or switching
mechanisms are allowed in this concept of protection
...

This protection aims are mainly reached by applying the following principles:
• The enclosures are designed in such a way that the entry of moisture and dirt in hazardous quantities is
prevented
...

Enclosures must guarantee the minimum Protection standard IP 54 even under severe external mechanical
forces
• Internally, the clearance and creepage distances must also be so dimensioned that even under harsh ambient
conditions, no short circuits via creepage paths or flashovers can occur
• The electrical connection terminals are designed in such a way that it is not possible for the cable connected
to them to come loose
• The dimensioning of the apparatus in electrical terms ensures that no inadmissible temperatures can occur
inside or on outer parts of the apparatus
...
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Industrial Automation

8
...
In an Ex ‘e’
junction box for example, the enclosure will be impact tested
...

The main uses of this technique are found in higher power circuits such as induction motors, fluorescent lighting fittings,
junction boxes, and terminal housings
...

When applied to junction boxes, an Ex ‘e’ enclosure is given an ‘enclosure factor’ when certified
...
Terminals mounted in the box must be component approved
...

Construction requirements: The standards permit the construction of apparatus in such a way that during normal
operation of the equipment, it is unlikely to become a source of ignition
...

This is as opposed to the inclusion of specific electrical or mechanical techniques to prevent ignition, which are applied
in some of the other methods
...
9

Principles of testing

As we have seen that increased safety apparatus calls for a high degree of integrity of material and manufacturing and
hence its assessment involves checking that the manufacturer has complied with the design parameters of the standard
...
This
is required to be done to establish the minimum distance, also known as creepage distance, required between the live
parts or live parts and ground
...
Two
electrodes spaced 4 mm apart are used to apply the test voltage
...

Ceramic material is exempted from this test
...
Unlike flameproof
apparatus, all surfaces, including internal surfaces of the apparatus, are considered
...
g
...

For the apparatus to pass the tests not only for itself, but also for the components that are housed in it, they should also
be within the limiting temperature range as per limits of the insulating material used
...
g
...
6, e
...
insulation of motor windings
...
com

Industrial Automation

Hazardous Areas and Intrinsic Safety

Degree of protection tests: As this is an important aspect of protection and the apparatus has to meet various levels of
protection against the ingress of solid objects or water are specified which must be tested in accordance with codes and
standards as specified for degrees of protection provided by enclosures for electrical apparatus (IP Code)
...
10

Non Sparking concept

The most widely used forms of explosion protection, which utilize the technique of energy limitation, are non-sparking
and intrinsic safety
...
These differences
deal mainly with the application of safety factors
...
Each does have its merits, which is why it is not
uncommon to see the two techniques used together
...
g
...
It could be argued that the overall installation is less safe with Ex ‘n’ than with Ex ‘i’ with only a marginal cost
saving
...
This raises the concern that area classification may be influenced
in order to accommodate Ex ‘n’ apparatus
...
10
...
”
The general requirements of such apparatus are that it shall not, in normal operation:
• Produce an arc or spark unless
• The operational arc or spark occurs in an enclosed break device
• The operational arc or spark has insufficient energy to cause ignition of a flammable atmosphere
• The operational arc or spark occurs in a hermetically sealed device
...
)
• Develop a surface temperature or hot spot capable of causing ignition of an external flammable atmosphere
...
)

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...
10
...
This is if it is operated well within its
rating and installed in areas where the risk of contact with a potentially flammable atmosphere was adequately low (Zone
2 only)
...
9 in Australia and IEC 60079-15 internationally, eventually emerged
to formalize the concept of good design using industrially graded apparatus and this was termed Type ‘n’ equipment
...

More recently, the method was re-designated Type ‘n’ under BS 6941:1988
...
Discontinuous
contacts were permitted provided the resultant spark could be shown non-sparking
...
The system is deemed safe in normal operation only and faults in the equipment
or components and their effect on the explosion protection integrity are not considered
...


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Industrial Automation

8
...
3)
...
3 Explosion / Fire triangle

This is a useful technique because an artificial ‘safe area’ having sufficient integrity can surround virtually any electrical
equipment
...
The system is not used often due to:
• High cost, and
• Inconvenience of equipment accessibility of this solution
The system is expensive to operate and maintain because the clean air must be pumped and controlled by other equipment
exposed to the hazardous area
...
The problems associated with this tend to complicate area classification
...
Disposal of used air, if it is likely to contain gas during the initial
purge, must be handled such that it does not convert a safe area to a hazardous area
...
Any uncertified equipment
may be placed in an enclosure where an inert gas or air is supplied and maintained at a slightly higher than atmospheric
pressure level
...


8
...
1 Definitions
Control of the atmosphere within a room or apparatus enclosure permits the safe use of electrical apparatus, which in
the absence of the control would be unsuitable
...

In some cases the two methods cannot be regarded as independent but for the purpose of this discourse the follow­ng
i
definitions apply:
Pressurizing: It is a method of safeguarding, whereby air or inert gas in a room or en­ losure, is maintained at a pressure
c
sufficient to prevent the ingress of the surrounding atmosphere, which might be flammable
...


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...
With static pressurization, the overpressure is created before
the system is commissioned by charging the enclosure with protective gas and maintained solely by the sealing of the
enclosure without any protective gas being supplied in the hazardous area
...
A maximum
oxygen concentration of 1 per cent by volume is permitted
...

Purging: This is a method of safeguarding whereby a flow of air or inert gas is maintained through a room or enclosure
in sufficient quantity to reduce or prevent any hazard, which could arise in the absence of the purge
...
Where the object is to ‘prevent’ a hazard, ‘sufficient’ shall take account of the highest
likely rate of release of flammable material within or into the room or enclosure)
...

Pressurizing/ Purging: This is a method of safeguarding employing both pressurizing and purging
...
With closed outlet, a supply of protective gas (instrument air or inert gas) is
sufficient to compensate for the leakage flow from the pressurized enclosure and pipelines
...
Pressurization with leakage compensation and pressurization with
continuous flow are based on a similar technical principle
...
Due to its drawbacks in operation, static pressurization is not widely used
...


8
...
2 Principles of application
The type of protection, pressurized apparatus “p” encloses electrical equipment or systems representing potential ignition
sources in a tight enclosure
...
This
overpressure prevents penetration of flammable gas or combustible dust from outside into the enclosure and hence the
coincidence of an explosive atmosphere and an ignition source
...
In such cases, flammable gases are
fed via a pipeline to the analyzer in a pressurized enclosure
...

The area containing the flammable gas (i
...
the pipelines and analyzer) is described as a containment system
...

With unlimited release, overpressure must be created by an inert protective gas, which prevents oxygen from penetrating
the enclosure
...


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In principle, any non-explosion protected apparatus and systems may be installed in the enclosure
...
12

Other protection concepts

There are additional concepts that are not so widely used, but have been developed and find their use in specific applications
...


8
...
1 Ex ‘o’: oil filling
This is one of the separation methods where the oil is used as a separation medium
...
4 was originally conceived for high power equipment
...

The definition of Ex ‘o’ protection concept in standards is,
‘A type of protection in which the electrical apparatus or parts of the electrical apparatus are immersed in a protective
liquid in such a way that an explosive atmosphere which maybe above the liquid or outside the enclosure cannot be ignited
...
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...

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Hazardous Areas and Intrinsic Safety

Figure 8
...
12
...

‘A type of protection in which the parts capable of igniting an explosive atmosphere are fixed in position and completely
surrounded by filling material to prevent the ignition of an external explosive atmosphere
...
It
cannot be used in situations where movement is required, i
...
, for the protection of relay contacts
...
12
...
It may be
thought of as the method of electrical protection using solids whereas Ex ‘o’ uses liquid and Ex ‘p’ uses gas
...
’
In other words encapsulation is used to prevent flammable gases from reaching a potential source of ignition within the
encapsulated apparatus
...
13

Earthing and Bonding

Correct “Earthing” is primarily required for the assurance of general electrical safety, reducing the risks to both human
life and installations
...
com

Industrial Automation

Hazardous Areas and Intrinsic Safety

Electrical “earthing” is required for five main purposes:
• To reduce the risk of personnel shock
• To operate electrical protective devices
• To guard against lightning surges
• To control electrostatic discharge
• To minimize electrical interference
...
13
...
Research
shows that the limbs have a resistance of about 500 Ohms
...
The effect of electricity penetrating the skin can be liked to the characteristics of a zener diode with
a reverse breakdown voltage of 5 to 10 V
...


8
...
2 Hazardous area considerations
Structural or fault currents arising from electrical equipment operating in hazardous areas must not become a source of
heat or sparks
...


8
...
3 Definitions
There is a subtle but essential difference between earthing and bonding, which must be understood
...

“Bonding” is where voltage differences between electrical conducting parts are eliminated
...
In this way there are two return paths
acting in parallel, which enhances the integrity of an earthing system
...
The other connection is to ensure that significant voltage differences do not appear
between devices
...
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Hazardous Areas and Intrinsic Safety

Figure 8
...
This is an advantage in that the two paths reduce the impedance
...


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13
...
These are unavoidable and
have to be coped with in the course of devising strategies
...

• Parasitic capacitance
• Fault currents

8
...

In the UK, BS5345 states specific reference to the Star-point Neutral Earthing system of the incoming supply
...
A Canadian standard allow
the designation of an Earth reference but does not state to what else it is to be connected to other than the Barrier earth
...
15

Fault finding and repairs

There is no right or wrong way to fault find on instrument loops and systems
...


8
...
1 Fault finding routine
It is usual for a fault to be investigated by following a logical routine, an example of which is shown in Figure 8
...


Figure 8
...
com

Industrial Automation

Hazardous Areas and Intrinsic Safety

8
...
2 Safety assessment of testing
There is a legal ‘duty of care’ on all industrial personnel that adequate precautions are taken so as not to endanger life or
investment during the course of work
...


8
...
3 Test equipment
There is a great variety of test equipment available on the market
...

The following are the types of tests conducted
...
The test used is for the circuit to withstand 500Vac
rms for one minute
Low voltage insulation test: The principle of this test is applying a low voltage source and monitoring the current taken
with an adequately sensitive measuring instrument
The 500Vac test: The high voltage test to instrumentation should be performed as shown in Figure 8
...
This is preferably
carried out in the safe area or if necessary in the hazardous area
...
7 High voltage testing of instruments

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1

Introduction and Brief History of SCADA

SCADA (Supervisory Control and Data Acquisition) has been around as long as there have been control systems
...
Supervisory
control was exercised by the operator manually operating various control knobs
...


9
...
1

Fundamental Principles of Modern SCADA Systems

SCADA refers to the combination of telemetry and data acquisition
...
The required control actions are then conveyed back to the process
...
As needs grew
to monitor and control more devices in the plant, the PLCs were distributed and the systems became more intelligent and
smaller in size
...



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Figure 9
...

• The data can be displayed in any way the user requires
...

• The operator can incorporate real data simulations into the system
...

• The data can be viewed from anywhere, not just on site
...

• Different operating skills are required, such as system analysts and programmer
...

• The operator can see only as far as the PLC
...
1
...
The master station displays the acquired data and also allows the
operator to perform remote control tasks
...
com

Industrial Automation

9
...
3

SCADA

SCADA Software

SCADA Software can be divided into two types, Proprietary or Open
...
These systems are sold as “turn key” solutions
...

Citect and WonderWare are just two of the open software packages available on the market for SCADA systems

9
...
4

SCADA and Local Area Networks

To enable all the nodes on the SCADA network to share information, they must be connected by some transmission
medium
...

Nodes need to share this transmission medium in such a way as to allow all nodes access to the medium without disrupting
an established sender
...
Connection of the SCADA network to
the LAN allows anyone within the company, with the right software and permission, to access the system
...


9
...
5

Modem Use in SCADA System

Figure 9
...
This
distance can vary from tens of meters to thousands of Kilometers
...
With this system the devices needed are a PC,
two dialup modems and the RTU (assuming that the RTU has a built in COM port)
...


9
...
6

System Implementation

When first planning and designing a SCADA system, consideration should be given to integrating new SCADA systems
into existing communication networks in order to avoid the substantial cost of setting up new infrastructure and
communications facilities
...


9
...
3
...
com

Industrial Automation

SCADA

Figure 9
...
These features depend on the hardware to be
implemented
...
2
...
com

Industrial Automation

SCADA

• Alarms shared to all clients
• Alarms displayed in chronological order
• Dynamic allocation of alarm pages
• User-defined formats and colors
• Up to four adjustable trip points for each analog alarm
• Deviation and rate of change monitoring for analog alarms
• Selective display of alarms by category (256 categories)
• Historical alarm and event logging
• Context-sensitive help
• On‑line alarm disable and threshold modification
• Event-triggered alarms
• Alarm-triggered reports
• Operator comments that can be attached to alarms
Trends
• Client server architecture
• True trend printouts (not screen dumps)
• Rubber band trend zooming
• Export data to DBF, CSV files
• X/Y plot capability
• Event based trends

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This is limited only by the PLC
architecture (typically 300 to 40,000 points)
Access to Data
• Direct, real‑time access to data by any network user
• Third‑party access to real‑time data, e
...
Lotus 123 and EXCEL
• Network DDE
• DDE compatibility: read, write and exec
• DDE to all IO device points
• Clipboard
Database
• ODBC driver support
• Direct SQL commands or high level reporting

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9
...
2

SCADA

The SCADA Software Package

Whilst performance and efficiency of the SCADA package with the current plant is important, the package should be easily
upgradeable to handle future requirement
...

There have been two main approaches to follow in designing the SCADA system:
• Centralized, where a single computer or mainframe performs all plant monitoring and all plant data is
stored on one database which resides on this computer
...

An effective solution is to examine the type of data required for each task and then to structure the system appropriately
...

There are typically five tasks in any SCADA system
...

• Input/Output Task
...

• Alarm Task
...

• Trends Task
...


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...
Reports are produced from plant data
...

• Display Task
...


9
...
3

System Response Times

These should be carefully specified for the following events
...


9
...
4

Specialized SCADA Protocols

A Protocol controls the message format common to all devices on a network
...
The CSMA/CD protocol
format is also used
...
2
...
1 Introduction to Protocols
The transmission of information (both directions) between the master station and RTUs using time division multiplexing
techniques requires the use of serial digital messages
...
Efficiency is defined as:
Information Bits Transmitted ÷ Total Bits Transmitted
Security is the ability to detect errors in the original information transmitted, caused by noise on the communication
channel
...
Implementation in hardware and software requires the minimum in complicated logic, memory storage, and
speed of operation
...

• Information; which provides the data in a coded form to allow the receiver to decode the information and
properly utilize it
...
com

Industrial Automation

SCADA

• Message Termination; which provides the message security checks and a means of denoting the end of the
message
...
At the receiver the same operations are performed on
the data and compared with the received check bits
...

A typical example of commonly used asynchronous message format is shown in Figure 9
...


Figure 9
...
2
...
2 Information Transfer
Master to Remote Data Transfer: Information transmitted from master to remote is for the purpose of device control, set
point control, or batch data transfer
...
This is provided in the form of a sequence of messages,
commonly called a select-before-operate sequence, as shown in Figure 9
...


Figure 9
...
5:
• Message establishment and message termination fields are not shown
• Function code specifies the operation to be performed by the RTU
...
com

Industrial Automation

SCADA

• Set point provides the value to be accepted by the RTU
• A remote to master checkback message is derived from the RTU point selection hardware in order to verify
that the RTU has acted correctly in interpreting the control selection
...
The basic sequence is shown in Figure 9
...


Figure 9
...
6:
• Message establishment and message termination fields are not shown
...

• Data identification identifies the amount and type of data requested by the master station
...
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9
...
4
...

HDLC is a bit based protocol
...

Asynchronous Balanced Mode (ABM): In this mode each node has equal status and can act as either a secondary or
primary node
...
7 below
...
7 HDLC Frame Format

Contents of Frame: The contents of the frame are briefly as follows:
The flag character is a byte with the form 01111110
...
This requires the transmitter to insert a ‘0’ after a sequence of five 1’s in the text (i
...
non flag characters)
...

The address field can contain one of three types for the request or response message to or from the secondary node:
• Standard secondary address
• Group addresses for groups of nodes on the network
• Broadcast addresses for all nodes on the network (here the address contains all 1s)
Where there are a large number of secondarys on the network, the address field can be extended beyond 8 bits by encoding
the least significant bit as a 1
...

The control field is indicated in Figure 9
...
Note that the send and receive sequence numbers are important to detect and
correct errors in the messages
...


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...

• In a multidrop link, a normal response mode frame is sent by the primary node with the P/F bit set to 1
together with the address of the secondary
...
Alternatively if the
receiving node is unable to accept the set up command a disconnected mode frame is returned
...

• The primary node then sends an unnumbered frame containing disconnect in the control field
...

• A similar approach is followed for a point to point link using asynchronous balanced mode except that both
nodes can initiate the setting up of the link and the transfer of information frames, and the clearing of the
point to point link
...

• In NRM mode if the secondary has no further data to transfer, it responds with a receiver not ready frame
with the P/F bit set to 1
...
2
...
4 The CSMA/CD Protocol Format
The CSMA/CD protocol is not as comprehensive as HDLC and is concerned with the method used to get data on and off
the physical medium
...

The format of a CSMA/CD frame which is transmitted is shown in Table 9
...
The data frame consists of a 48 bit source and destination
address, 16 bits of length or type fields, data and a 32 bit CRC field
...

Table 9
...


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...
2
...
It is
designed as an open, interoperable and simple protocol specifically for SCADA controls systems
...
The physical
layer is generally designed around RS232 (V
...

The DNP is well developed as a device protocol within a complete SCADA system
...
These devices can be coupled as a multi-drop fieldbus system
...
DNP does not specify a single physical layer
for the Serial bus (multi-mode) topology
...
The application program can integrate DNP with other protocols if the SCADA software
permits
...


9
...
6

New Technologies in SCADA Systems

A few of the new developments that are occurring in SCADA technology will be briefly listed below
...

• Rapid Improvement in LAN Technology for Master Stations
• Man Machine Interface
• Remote Terminal Units
• Communications

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3

SCADA

Distributed control system (DCS)

SCADA technology has existed since the early sixties and there are now two other competing approaches possible Distributed control system (DCS) and Programmable logic controller (PLC)
...
DCS systems
have evolved into providing very sophisticated analogue (e
...
loop) control capability
...
The data
highway is normally capable of high speeds - typically 1 Mbps up to 10 Mbps (see Figure 9
...


Figure 9
...
3
...

A DCS is a process-oriented system and it treats the control of the process, (the chemical plant, refinery or whatever) as
its main task, and it presents data to operators as part of its job
...
Interestingly enough, the remote equipment is merely there
to collect the data - though it may also do some very complex process control
...
g
...
When the DCS operator wants to see information he/she usually makes a request
directly to the field I/O and gets a response
...


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...
The ‘quality’ of data shown to the
operator is an important facet of SCADA system operation
...

There are many other differences, but they tend to involve a lot of detail
...
It frequently needs to do event processing and data quality validation
...

• A DCS is always connected to its data source, so it does not need to maintain a database of ‘current values’
...


9
...
2

DCS Controller

A DCS controller is a high-performance device capable of handling hundreds of discrete or regulatory control loops per
second
...
But a user
can customize his control configuration to meet the application requirements
...

Control modes: A basic DCS controller has thefollowing operating modes:
• Manual mode
• Automatic mode
...

• Backup cascade mode
...
com

Industrial Automation

SCADA

Figure 9
...
3
...


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SCADA

Functions from I/O scanning through regulatory and logic control to more advanced control strategies can be easily
implemented through the DCS advanced controller
...

Conceptually, a DCS controller can be thought of as partitioned into ‘slots’ of various types
...

A tagged slot is referred to as a ‘data point’ or ‘point’ in some DCS systems
...

Following are some of the different types of data points that can be configured into a DCS controller slot:
• Regulatory PV
• Regulatory control
• Digital composite
• Logic
• Device control
• Array
• Flag
• Numeric
• Timer
• String, etc
...
3
...
Some common control algorithms follow
...
One can choose from one of the two forms of this algorithm; the interactive (real)
form, and the non-interactive (ideal) form
...
4

Introduction to the PLC

“PLC” means “Programmable Logic Controller”
...
It can be easily programmed or changed as per the application’s requirement
...


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In a programming device, the PLC control logic is first developed and then transferred to the PLC
...
4
...

• It can conduct counting, calculation and comparison of analog process values
...

• It responds to the changes in process parameters within fractions of seconds
...

• It is cost effective for controlling complex systems
...
4
...
10 shows the basic block diagram of a common PLC system
...
10   Block diagram of a PLC

As shown in the above figure, the heart of the “PLC” in the center, i
...
, the Processor or CPU (Central Processing Unit)
...

• Input and output modules are the media for data exchange between field devices and CPU
...

• A programming device is a computer loaded with programming software, which allows a user to create,
transfer and make changes in the PLC software
...


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...
4
...

• A medium system has I/Os ranging from 500 to 5,000
...


9
...
4

Components of the PLC system

CPU or processor: The main processor (Central Processing Unit or CPU) is a microprocessor-based system that executes
the control program after reading the status of field inputs and then sends commands to field outputs
...
The PLC knows the real status of field
devices, and controls the field devices by means of the relevant I/O cards
...

Operating station: An operating station is commonly used to provide an “Operating Window” to the process
...


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5

SCADA

Considerations and benefits of SCADA system

Typical considerations when putting a SCADA system together are:
Overall control requirements
• Sequence logic
• Analog loop control
• Ratio and number of analog to digital points
• Speed of control and data acquisition
Master/Operator control stations
• Type of displays required
• Historical archiving requirements
System consideration
• Reliability/availability
• Speed of communications/update time/system scan rates
• System redundancy
• Expansion capability
• Application software and modeling
Obviously a SCADA system’s initial cost has to be justified
...


9
...
Control Systems, whether
a conventional Control Desk or a Computer/PLCs System with SCADA or a Distributed Control System (DCS), provides
a man-machine-interface to monitor and control the plant equipment and processes
...
com

Industrial Automation

SCADA

Alarm Systems are an integral part of man-machine interface
...
Alarm systems indicate the abnormal conditions and problems of the plant
and equipment to the operators, enabling them to take corrective action and bring the plant/equipment back to normal
conditions
...

An alarm system brings the following to the notice of the operator:
• problems that need operator attention
• process changes that require corrective action
• unsafe operating conditions before Emergency Shut-down of the plant
• hazardous conditions
• deviations from desired/normal conditions

9
...
1

Functions of the plant or process operator

An alarm system helps/assists the operators in monitoring and controlling the plant, equipment and processes within safe
and normal operating conditions
...

Generally, the functions of a plant operator are inclusive of the following activities but are not limited to:
• safe and normal operation of plant/equipment
• production at optimum levels
• identification of abnormal, hazardous and unsafe plant/equipment conditions and taking corrective action
• fault identification and communication of faults to maintenance
The above mentioned function and task priorities of a plant operator change with the changing conditions of the plant
...
com

Industrial Automation

9
...
2

SCADA

Functions of an alarm system

The main function of an alarm system is to direct the attention of an operator towards the plant abnormal conditions
that need timely assessment and/or timely corrective action(s)
...

When an abnormal condition arises, the alarm system gives an alarm in the form of an audible warning, flashing or blinking
alarm indication and an alarm message
...
In a good alarm system, guidance or help messages on how to respond and take corrections are also provided
...

Such feedback is generally provided on supplementary display screens that can be accessed by selecting an alarm in the
Alarm list
...
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...
4

SCADA

Alarm system design

Designing an alarm system is a process
...
To determine the importance and reliability of an alarm, it is necessary to carry
out a qualitative and quantitative risk assessment to consider whether the alarm is safety related and whether it is to be
implemented on an independent stand-alone system as opposed to the process control system
...


9
...
5

Assessment of risk

Risk is a measure of the probable rate of occurrence of a hazard and its severity
...

Alarms are configured and presented to the operator to take corrective action(s) and minimize the sub-optimal operations of
the plant/equipment or to protect plant/equipment from damages that can lead to injury to people, damage to environment
and/or economic losses
...


9
...
6

Protection provided by the alarm system

Protection provided by an alarm system can take place in two ways
...


9
...
7

Safety related alarms

As per the international standard IEC 61508, an alarm system, whether electrical or electronic or programmable, should
be considered as safety related only if:
• It is a claimed part of the facilities for reducing the risk(s) from hazards to people to an acceptable or
tolerable level, and
• The claimed reduction by the alarm system in the risk(s) is significant
...
1,
• It is designed, operated and maintained as per the requirements defined in the standard,
• It is independent and separate from the process control system, unless the process control system itself has
been identified as a safety related system and implemented accordingly
...
6
...
The consequences of alarm failure or the alarm
being missed need to be identified
...


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Any hazard to people should be in the
form of formal risk assessment for the plant
...


(iii)

Expected frequency of the risk occurrence should be estimated
...
Appropriate frequency of occurrence may be specified as once a
week or once in month, etc
...


(v)

Are any reliability claims made in the plant, in terms of safety and protection, provided by the
alarm? Do these reliability claims require the alarm to be classified as a safety related alarm? If an
alarm is not safety related, then what are the economic and/or environmental risks involved in
implementing the alarm within the process control system?

(vi)

It is important to know the implications of alarm failure due to alarm sensor/instrument failure
...
Should the alarm
sensor/instrument be made redundant?

(vii)

How effective will the operator response to the alarm be? If the operator cannot take any corrective
or preventive action to prevent the risk, then the alarm hardly provides any benefit and should
not be configured as an alarm
...
6
...
The response must be clearly defined for each alarm
...


(iii)

If required, additional displays should be developed that provide the operator with information to
help him decide how to respond in different conditions of the plant
...


9
...
10 Alarm prioritization
(i)

The likely safety, economic and environmental consequences of the operator not responding to
the alarm should be assessed
...


(iii)

It should be determined whether it will be required to change the priority of the alarm depending
on changes in the operating conditions
...
com

Industrial Automation

SCADA

9
...
11 Alarm settings
(i)

What is the normal range for the alarmed process variable? What should be the alarm settings for
alarming the safety hazard, and/or economic losses and/or environmental damages?

(ii)

How many alarms should be set for the process variable – Low, Low-Low, High, High-High and
what should the settings be for these alarms?

(iii)

Is there a need for changing the alarm setting depending on plant operating conditions?

(iv)

During normal plant operation, what are the fluctuations in the process variable to be alarmed?

9
...
12 Alarm suppression
(i)

If the alarm is likely to be generated during large disturbance/upset in the plant or during plant
trips, then the alarm should be suppressed using a suitable logic
...

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1

Fundamentals of project management

Operations and projects share a number of characteristics in that they are:
• Planned, executed, and controlled
• Constrained by resource limitations
• Performed by people
Projects are, however, different from operations (such as maintenance or repair work) in that they are temporary endeavors
undertaken to create a unique product or service
...


10
...
1 Project management
Project management is the application of specific knowledge, skills, tools, and techniques to plan, organise, initiate, and
control the implementation of the project, in order to achieve the desired outcome(s) safely
...


10
...
2 Project life cycle
Projects proceed through a sequence of phases from concept to completion
...

There are only a limited number of generic lifecycles
...
Consequently the initial starting point
for managing the project is to define the type, and select an appropriate life cycle model as the planning framework
...
1
...
The organization
of the project team directly influences the probability of achieving a successful outcome
...
1

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1  Project structures within organizations

The organization of the project team is characterized by:
• The principal or project sponsor
...

• The project manager
...

• A project control officer or group, if this function is not undertaken by the project manager
...


10
...
4 Project planning
The project planning phase is critical to the effective implementation and control of the project and the basis for project
success is established during this phase
...
The basic
element required to properly define the PQP is the Work Breakdown Structure or WBS
...
com

Industrial Automation

10
...
e
...


10
...
1 Project planning
The principal aim of project management is to effectively utilize the available resources in order to achieve the planned
objective(s)
...
These comprise:
• The ‘Critical Path’ method (also known as the Activity on Arrow or AoA method)
• The ‘Precedence’ method (also known as the Activity on Node or AoN method)
Precedence network analyses are normally presented graphically, either as the network diagram itself, or as a time-scaled bar
chart known as a Gantt chart
...


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• Preparation of the logic sequence to determine the relationships between the activities
...

• Analysis of the network
...
3

Cost Management

Effective cost management is a key element of successful project management
...

Cost management includes the processes required to ensure that the project/contract is completed within the approved
budget
...
Estimates are prepared to meet two
different objectives:
• As the basis for determining the economic feasibility of a project
• As the basis for cost management of the project
...
The budgeting process
should establish a cost baseline that provides:
• The basis against which project performance may be measured
• A forecast payment schedule to allow for funds management by the principal
Financial control: The definition of financial controls should extend to:
• Controls over the commitment of funds, i
...
financial authority
• Controls over the approval of expenditure, i
...
authorization of payments
Change control: Effective change control is a vital element of project cost control
...


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Cost reporting: The basic objective of the financial report must be to provide an accurate status report of forecast financial
cost versus approved budget
...
e
...


10
...

Earned value analysis: Earned Value Analysis (EVA) is the analytical part of what is known as Earned Value Management
(EVM), so the two names are often used interchangeably
...

A significant benefit of the EVM approach is that most of the data can be presented graphically, in one macroscopic view
of the project progress
...
5

Management of project team

Projects exist to create a unique product or service within a limited time frame
...
If
there is more than one person working in a project then it is called a team
...


10
...
1 Creating a team culture
Cultures within the project team are a reflection of the project manager’s preferences and style
...
com

Industrial Automation

Project Management of I&C Project

• Setting realistic performance expectations for each team member
• Delegating effectively (instead of over-supervising)
• Publicly rewarding good performance
• Acknowledging legitimate concerns and conflicts within the team
At each stage the project manager can communicate values that move the team to the next stage
...


10
...
2 Team motivation
There are certain issues that spur on individuals within the team to even greater achievements, and other issues that stifle
performance
...
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Industrial Automation

10
...

Definition of ‘risk’: Risk is the exposure to a process or event that prejudices the successful achievement of the project
outcome, by adversely impacting on cost, time, or functional objectives
...
6
...

Risk identification: The purpose of this step is to identify all the risks, including those not under the control of the
organization, which may impact on the framework defined above
...

Risk analysis: The objectives of risk analysis are to:
• Assign a level of risk to each identified event
• Provide data to assist the assessment and treatment processes
• Separate minor, acceptable risks from others requiring further consideration

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e
...

Risk assessment: Risk assessment is the process of comparing the levels of risks determined from the analysis process
against the acceptance criteria previously established
...

Risk treatment: Risk treatment involves identifying the range of options available for treating risks identified as requiring
action in the previous stage, evaluating those options in respect of each risk, and developing and implementing risk
treatment plans
...

Monitoring and review: Monitoring and review of all elements of the risk management programme is essential
...
Few risks remain
static and factors impacting on the likelihood or consequences may change
...


10
...
The issues addressed include:
• The basis of Commonwealth law
• The essential elements of contracts
• Procurement strategies
• Tendering
• Vitiating factors, i
...
those factors that reduce or remove the legal force of the contract
• Termination of contracts
• Extensions of time
• Remedies available for breach of a contract
• Penalties and bonuses

10
...
1 The Commonwealth legal system
In the Commonwealth legal system the Legislature makes the laws, the Executive administers the laws and the Judiciary
decides in the case of disputes or transgressions of the laws
...
com

Industrial Automation

Project Management of I&C Project

The only way in which rules can be enacted so as to apply generally is by Act of Parliament
...


10
...
2 Elements of contracts
• The contract may be oral, or written, or implied by the conduct of the parties
...
It is then a formal
simple contract
...
The period of limitation is 12 years for breach of
contracts made under seal
...

• A contract made by deed must be under seal
...


360°
thinking

The essential requirements for a contract to be legally enforceable are:


...


360°
thinking


...
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Industrial Automation

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10
...
3 Procurement strategy issues
Consideration of the appropriate strategy should include the following factors:
• Risk preferences of the Principal
• The requirement to demonstrate a competitive process
• The need and/or ability to properly define scope of work prior to commencement
• The need or ability to exercise control over the operations of the Contractor
• The need to achieve early completion
There are a number of separate aspects to be considered when determining construction procurement strategy
...
7
...
Contracts of each type
may or may not be subject to cost escalation: if not, they are described as ‘fixed price’ contracts
...


10
...
5 Delivery strategies
For service delivery contracts the principal delivery strategies are:
• Defining service requirements based on inputs to be provided
...


10
...
6 Tendering
The law relating to tendering practice is in a process of change as the result of recent case law developments, primarily in
Canada
...
Previously it
was generally regarded, at least by the practitioners, that no contractual obligations arise prior to acceptance of a tender
...


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7
...
g
...
7
...
This arises from:
• Performance
• Agreement
• Passage of time
• Frustration
• Repudiation
• Determination
• Operation of law

10
...
9 Time for completion and extensions of time
• Time for completion
• Provisions to extend the time for completion
• Determination of extensions of time
• Notification of the time extension
• Acceleration
• Payment arising from an extension of time

10
...
10 Remedies for breach of contract
Damages for breach of contract are governed by two considerations, namely the remoteness and the measure of damages
...
This
sum is either a liquidated damage or a penalty
...
com

Industrial Automation

Project Management of I&C Project

The right to an action for damages may be released by:
• Release under seal
• Release by accord and satisfaction
• Fluxion of time, i
...
the right to claim damages is extinguished by the passage of time
...
7
...
Penalties and bonuses
A penalty is a sum in the nature of a threat to secure performance
...

Building contracts may provide for a bonus to be paid, for example for early completion, or for completion below a
defined price
...

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...


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...
1

Basic Measurement performance terms and specifications

There are a number of criteria that must be satisfied when specifying process measurement equipment
...
It
determines how precise or correct the measurements are to the actual value and is used to determine the suitability of
the measuring equipment
...

Budget/Cost: Although not so much a specification, the cost of the equipment is certainly a selection consideration
...
Even if all the other specifications are met, this can
prove an inhibiting factor

11
...
In these circumstances the following
may need to be considered:

11
...
1 Hysteresis
Hysteresis is the difference in the output for given input - when the input is increasing and output for same input when
input is decreasing
...
1
...
com

Industrial Automation

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Figure 11
...


11
...
2 Linearity
Linearity expresses the deviation of the actual reading from a straight line
...
2
...


Figure 11
...
2
...
Repeatability is generally within the accuracy range of a device and is different from hysteresis in that the
operating direction and conditions must be the same
...
When a control system sees a change
in the parameter it is controlling, it will adjust its output accordingly
...


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2
...
A slow responding device may not be suitable for an
application
...
3

Pressure Measurement

Let us first discuss the principles of pressure measurement

11
...
1 Bar and Pascal
Pressure is defined as a force per unit area, and can be measured in units such as psi (pounds per square inch), inches of
water, millimetres of mercury, pascal (Pa, or N/m²) or bar
...


11
...
2 Absolute, Gauge and Differential pressure
The pascal is a means of measuring a quantity of pressure
...
However when the pressure is measured
relative to the atmospheric pressure, then the result will be termed pascal (Gauge)
...


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3
...
Static pressure is the
result of the weight of all the air molecules above that point pressing down
...
3 shows static pressure acting on hand and static pressure measuring device
...


Figure 11
...

This extra pressure is over and above the (always-present) static pressure, and is called the dynamic pressure
...
Dynamic pressure occurs when a body is moving through the air, or the air is
flowing past the body
...
Total pressure is the sum of the static pressure and the dynamic pressure
...
3
...
As pressure is applied internally, the tube straightens and returns to its
original form when the pressure is released
...
com

Industrial Automation

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Helix and Spiral Tubes: Helix and spiral tubes are fabricated from tubing into shapes as per their naming
...
The amount of straightening or uncoiling is
determined by the pressure applied
...

One end of the Bellows is fixed and the other moves in response to the applied pressure
...

Diaphragm: Many pressure sensors depend on the deflection of a diaphragm for measurement
...

Manometer: The simplest form of a manometer is that of a U-shaped tube filled with liquid
...
If there is a difference in pressure, then the heights
of the liquid on the two sides of the tube will be different
...
The bell instrument is used in applications where very low pressures are required to be measured,
typically in the order of 0-250 Pa
...
3
...
A change in
pressure causes a change in resistance as the metal is deformed
...
If the elastic limit is exceeded then permanent deformation will occur
...
Figure 11
...


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...
4   Wheatstone circuit for strain gauges

Strain gauges are mainly used due to their small size and fast response to load changes
...
The principle is similar to that of a guitar string
...
As the pressure changes on the diaphragm so does the tension on the wire, which affects the frequency that
the wire vibrates or resonates at
...

Piezoelectric: When pressure is applied to crystals, they are elastically deformed
...
When a crystal is deformed, an electric charge is generated for only a few seconds
...


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Industrial Automation

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Because these sensors can only measure for a short period, they are not suitable for static pressure measurement
...
The sensor is energized electrically with a high frequency oscillator
...
The movement is transferred from the process medium to the core by use of
a diaphragm, bellows or bourdon tube
...
Three coils are wound onto the same insulating tube
containing the high permeability iron core
...

Equal voltages are induced in the secondary coils if the core is in the centre
...

When the core is moved from the centre position, the result of the voltages in the secondary windings will be different
...


Figure 11
...


LVDTs are sensitive to vibration and are subject to mechanical wear
...
5  Linear variable differential transformer

11
...
6 Installation Consideration
There are a number of points to consider in a pressure measurement application
...

• Location of Process Connections
• Isolation Valves
• Use of Impulse Tubing
• Test and Drain Valves
• Sensor Construction
• Temperature Effects
• Remote Diaphragm Seals

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...
4

Level Measurement

11
...
1 Principles of Level Measurement
11
...
1
...
However, there are numerous ways to measure level that require different
technologies and various units of measurement
...

Microprocessor based devices can indicate level or volume
...
4
...
1 Point Detection
Point detection can also be provided for all liquids and solids
...
4
...
4
...
1 Simple Sight Glasses
A visual indication of the level can be obtained when part of the vessel is constructed from transparent material or the
liquid in a vessel is bypassed through a transparent tube
...


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...
4
...
2 Gauging Rod Method
This requires a little more manual effort than the sight glass, but is another very simple and cheap method of accounting
for level
...


11
...
3 Buoyancy Tape
There are two main types of buoyancy tape systems available:
Float and Tape Systems: One common form of level measuring system uses a tape or servo motor which is connected
to a float
...

Other systems use the float method by sensing the position of the float magnetically or electrically
...
e
...


11
...
4 Hydrostatic Pressure
Some of the different types of level measurement with pressure are:
• Static pressure
• Differential pressure
• Bubble tube method
• Diaphragm Box
• Weighing
• Static Pressure

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...
The pressure is related to the height by the following:


P = h
...
In fact, any instrument that can measure pressure can be
calibrated to read height of a given liquid, and can be used to measure liquid level in vessels under atmospheric conditions
...
5

Temperature Measurement

11
...
1 Principles of Temperature Measurement
Temperature measurement relies on the transfer of heat energy from the process material to the measuring device
...

There are two main industrial types of temperature sensors:
• Contact
• Non contact
Contact: Contact is the more common and widely used form of temperature measurement
...
The rate and proportion of
change is different between the three types, and also different within the type classes
...
com

Industrial Automation

11
...
6
...
This
voltage is called an emf (electro-motive force) and is proportional to temperature
...
As the two junctions are at different
temperatures a thermal emf is generated
...


Figure 11
...

The relationship between mill-volts and temperature is not linear
...


11
...
Figure 11
...
The transducer is the temperature sensitive resistor itself, with the sensor
being a combination of the transducer and electronics that measure the resistance of the device
...
The electrical
resistance generally increases with temperature, and the device is defined as having a positive temperature coefficient
...

The temperature coefficient defines how much the resistance will change for a change in temperature, and has units of
ohms/oC
...

Apart from Platinum, other metals are used for RTDs such as Copper and Nickel
...


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7  Typical RTD and thermowell construction

11
...
The principle of temperature measurement with a
thermistor is that its resistance changes with temperature
...

A thermistor is a bulk semiconductor device, and as such can be fabricated in many forms
...
Size does vary from a bead of 1mm to a disc of several centimeters in diameter and thickness
...
This is done by varying the
doping and semiconductor materials
...
ie
...
admissions@ie
...
com

Length: 1O MONTHS
Av
...
Some thermistors have a near linear
temperature resistance relationship, others are available with a sharp change in slope (sensitivity) at a particular
characteristic temperature
...
9

Infrared Pyrometers

Any object with a temperature above absolute zero will radiate electromagnetic energy
...

Infrared or radiation pyrometers use an optical system to focus the radiated energy onto a sensing device
...
In selecting an effective radiation
pyrometer, a wavelength-band needs to be chosen that is not transmitted by the material
...

There are a number of different types of infrared pyrometers:
• Total radiation
• Single wavelength
• Dual wavelength

11
...
The time of flight is used, and since the distance between points is known it is possible to measure any
change in conditions
...

Typical Applications: Acoustic pyrometers are used when requiring an average temperature or the temperature over a
large area or volume of gas
...
They work over a very large
temperature range and are useful for mapping thermal contours
...


11
...
11
...
1
...
com

Industrial Automation

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Table 11
...
This by itself does not give any information about the quantity of fluid
...
Most volumetric flow equipment
measures the velocity and calculates the volumetric flow based on a constant cross sectional area
...
A
where:

v is the velocity



A is the cross sectional area



Q is the volumetric flow rate

Mass flow rate can only be calculated from the velocity or the volumetric flow rates if the density is constant
...

W=Q
...
com

Industrial Automation

Latest Instrumentation and Valve Development

The flow of gases is normally measured in terms of mass per unit time
...
Some flowmeters, such as Coriolis meters, measure the
mass flow directly
...
Mass flow is calculated from the density
and the volumetric flow as shown above
...
This type of measurement is referred to as the inferred method of measuring mass flow as shown
in Figure 11
...


Figure 11
...
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11
...
This technique requires the pressure
to be measured on both sides of an imposed restriction in the path of normal flow
...

Differential pressure devices works on the principle of inducing a change in pressure by placing a restriction in the line of
flow
...

The restriction in the pipe is called the primary element
...
This device can measure and calculate the flow rate
...

The velocity of flow is related to the square root of the differential pressure
...
12
...


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9
...


Figure 11
...
A flume
forces the liquid into a narrower channel and in doing so only incurs a head pressure drop of about 1/4 of that for a weir
of equal size
...
Sme of the
more common types for open channel flow measurement are:
• Float and cable
• Ball float
• Air bubbles
• Pressure sensing
In closed applications, and even in pipes, ultrasonics is often used to determine the level
...
12
...
The principle of operation is that the flow
stream displaces a float placed in the stream
...

It is because of the low viscosity and high velocity that the frictional resistance of the flow is negligible compared to the
resistance of the obstruction (float) placed in the flow stream
...
This provided stability and
centering of the float, and is where the designation of rotameter came from
...
com

Industrial Automation

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The rotameter consists of a tapered measuring tube and a float
...
A balance is achieved between the force
of the flow stream and the weight of the float
...
Figure 11
...


Figure 11
...
13 Magnetic Flowmeters
Electromagnetic flowmeters, also known as magmeters, use Faraday’s law of electromagnetic induction to sense the
velocity of fluid flow
...
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The conductive material in the case of a magmeter is the conductive fluid
...
13
...

Transit Time: The transit-time flowmeter device sends pulses of ultrasonic energy diagonally across the pipe
...
Figure 11
...

Each location contains a transmitter and receiver
...


Figure 11
...
With the Doppler Effect meter, a beam of ultrasonic energy is transmitted diagonally through the pipe
...
Since the objects are moving,
the reflected ultrasonic energy has a different frequency
...
Figure 11
...


Figure 11
...
com

Industrial Automation

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It is quite common for only one sensor to be used
...
These can also be
mounted outside of the pipe
...
13
...

Although most meters can infer mass flow rate from volumetric flow measurements, there are a number of ways to
measure mass flow directly:
• The Coriolis meter
• The thermal mass flowmeter
• Radiation density

11
...
Process plants consist
of hundreds, or even thousands, of control circuits all networked together to produce a product
...
Each of these control loops is designed to keep
some important process variable such as:
• Pressure
• Flow
• Level
• Temperature
The control valve assembly typically consists mainly of the valve body, the internal trim parts, and an actuator to provide
the motive power to operate the valve
...

Basic Types of control valves: There are two basic types of control valves: rotary and linear
...
Rotary-motion valves have ball, butterfly, or plug
closures
...


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13  Linear valve

Linear Valve Features:
• A tortuous flow path
• A low recovery
• The throttling of small flow rates
• A variety of special trim designs
• Suitability to high-pressure applications
• Be flanged or threaded
• A separable bonnet

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14  Rotary valves

Rotary Valve Features:
• Streamlined flow path
• High recovery
• More capacity
• Less packing wear
• Can handle slurry and abrasives
• Flangeless
• Integral bonnet
• High rangeability
In addition to linear and rotary, control valves are also classified according to their guiding systems and the types of
services they are used in
...
14
...

• Globe Valves
• Gate Valves
• Butter Fly Valves
• Eccentric Disc Valves
• Ball Valves
• Rotary Plug Valves
• Diaphragm Valves
• Pinch Valves

11
...
2 Control Valve characteristics
The performance and behavior of the control valve is dependant on the type of actuation
...
Different combinations of these parameters give a peculiar pattern of operation through
the total travel of the valve opening
...


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1

Main Technology Trends

Some of the main technology trends in industrial automation are discussed in this section
...
The introduction of wireless sensor
networking (WSN) represents just such a sea change
...

In contrast to P2P and P2MP connections, WSN utilizes self-forming, self-healing mesh networking to enable field devices
to be deployed cost effectively without the need for site surveys or specially trained field technicians to manually configure
directional antennas
...

However, WSN will not be appropriate for all industrial automation applications
...

Productivity: The fundamental purpose of industrial automation is to improve productivity – generate increased output
with reduced costs and facilitate increased output by reducing the costs
...


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Increased productivity means things
are made more cheaply and more quickly
...
All of these effects,
from a lack of information, cost money
...
In today’s information age, data needed to make decisions should be made available to all workers in an
effortless fashion
...

Data important to decision making should be easily accessible to workers through database driven, dynamic web portals
or other centralized corporate applications
...
These
applications can be implemented either using off-the-shelf software or with specific customisation for the industry
...

Offshore Outsourcing: In this era of globalization, entrepreneurs are always looking ahead to beat competition
...
The concept involves taking internal company functions and paying an outside firm
to handle them, which enables the entrepreneurs to divert their full attention towards core competencies
...

Although Software outsourcing is the buzzword in the industry, outsourcing of all kind of business is now happening
...
Some of them are discussed below:

12
...
Every country in the world
is competing
...
And they’re moving strongly into high-tech
...
com

Industrial Automation

Forecasts and Predictions

• The city of Wenzhou, Eastern China produces 70% of the world’s metal cigarette lighters
• Walmart – Buys $18 billion from China, providing a direct link to the US consumer

12
...
3
...

It will be possible to produce new materials with desired properties: smaller, stronger, tougher, lighter and more resilient
than anything that has ever been made
...
For example, nano structured membranes are being developed for efficient filtering of pollutants from
water or air
...


12
...
2 Machine to machine networking
The convergence of smart devices with the internet is creating a new inflection point
...

This will far surpass human communications in scope, value, and sheer numbers
...
Eventually reaching tens of billions of connections, machines will
communicate with each other, as well as with data mining and processing systems that will automate the communication
and interpretation of the mass of data they gather
...


12
...
3 Complex adaptive systems
Complex adaptive systems yield significant advances through reduced software, faster and easier installation, robust
performance, vastly improved flexibility, capability to handle very much larger I/O point-counts
...
Complex adaptive systems are
robust because the behavior is not dependent on single, or even multiple failure points
...
CAS has the ability to achieve much higher levels of performance through emergent behavior
and self-organizing capabilities
...
com

Industrial Automation

Forecasts and Predictions

12
...
4 Wireless Connections
The connectivity infrastructure is moving very quickly to connect everyone and everything to the Internet, not only
through high-speed DSL and cable-modems, but soon through wireless
...
Connecting automation products with conventional wire beyond
the confines of a typical system enclosure is still a major hindrance in the typical factory
...

Wireless mobility and information services already bring voice, entertainment, Internet access and safety services into
cars and trucks
...


12
...
5 Fully automated factories
Automated factories and processes are too expensive to be rebuilt for every design change - so they have to be highly
configurable and flexible
...

With technology available today, fully automated factories - in a truly realistic sense - are quickly becoming an accepted fact
...


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---