The document provides an overview of the Aditya Birla Group, a large Indian conglomerate. It discusses the company's origins in the 19th century with Seth Shiv Narayan Birla starting a cotton trading business. It expanded into various industries in the early 20th century under Ghanshyamdas Birla. The group now operates in over 40 countries with over 120,000 employees. The document also describes the cement production process used by the group's cement division, including mining of raw materials, crushing, blending, preheating and the rotary kiln production of clinker.

1. CHAPTER -1
INTRODUCTION
1.1 COMPANY PROFILE
The Aditya Birla Group is a conglomerate named after Aditya Vikram Birla,
Headquaters in Aditya Birla Center in Worli, Mumbai, India. It operates in 40
countries with more than 120,000 employees worldwide. The group was found by
Seth Shiv Narayan Birla in 1857. The groupinterests in sectors such as viscose staple
fiber, metals, cement, v Corporation Limited previously known as Birla Jute and
Industries Limited, belong to the Miscose filament yarn,branded apparel,carbon black,
chemicals, fertilizers, insulators, financial services, telecom, Bpo and it services.
1.2 ORIGIN & GROWTH
The roots of the Aditya Birla Group date back to the 19th century in the
picturesque town of Pilani, setamidst the Rajasthan desert. It was here that Seth
ShivNarayan Birla started trading in cotton, laying the foundation for the House of
Birla.Through India's arduous times of the 1850s, the Birla business expanded rapidly.
In the early part of the 20th century, our Group's founding father, Ghanshyamdas
Birla, set up industries in critical sectors such as textiles and fibre, aluminium, cement
and chemicals.
Fig 1.1- Plant View From Cement Silo Top
As a close confidante of Mahatma Gandhi, he played an active role in the
Indian freedom struggle. He represented India at the first and second round-table
conference in London, along with Gandhiji. It was at "Birla House" in Delhi that the
luminaries of the Indian freedom struggle often met to plot the downfall of the British
Raj.
Ghanshyamdas Birla found no contradiction in pursuing business goals with the
1

2. dedication of a saint, emerging as one of the foremost industrialists of pre-
independence India. The principles by which he lived were soaked up by his
grandson, Aditya Vikram Birla, our Group's legendary leader.
1.3CORPORATE SYMBOL
The corporate symbol of concentric circles around a triangle represents the very
multi dimensional nature. The apex of triangle is a visual representation of the force
that drives the entire corporation the unifying force in search of excellence. The
various sub-business units are diverse in interest and operation. But they are held
together by centripetal drive. The circle represents the inspiration to explore new
frontiers of growth.
1.4 PRODUCT CHART
2
J U T E
D I V I S I O N
C E M E N T
D I V I S I O N
A U T O T R I M
D I V I S I O N
B I R L A C A R B I D E &
G L A S S
ADITYA BIRLA CORPORATION LIMITED

3. 1.5 AWARDS
Awards
C A P E X I L A w a r d s e v e r y y e a r , s i n c e 1 9 9 0 .
“Bhama Shah Samman” from the Rajasthan Government for Educational Activities for Aditya Birla Cement Works in 1996-97.
VEC-IIT, Madras recognized Aditya Birla Cement Works For “Excellence In Improving Machinery Health Condition” in 1997.
“WorkersEducationTrophy”awardedbycentralBoardofWorkersEducation,UdaipurMinistryoflabor,GovernmentofIndia,forAdityaBirlaCementWorks in1998-99andagainin2001-02.
3
B I R L A
V I N O L E U M
B I R L A
S Y N T H E T I C S

4. “Lal Bahadur Shastri Memorial National Award” for Excellent Pollution Control Implementation by Aditya birla Cement Works in 2002-03.
“Best Supporting Core Plant” by Regional Training Centre, Nimabhera in 1998-99, 2000-01 & 2001-02.
“Awards to Captive Mines” (Safety Week Celebration in Udaipur Region) by DGMS, Udaipur 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002.
1.6 CEMENT DIVISION
The cement division of aditya Birla Corporation Limited has six plants as
under table. Chittor units aditya Birla share is around Rs.350 Crores, which is 34% of
the company’s turnovers. These plants manufacturing the verity of cement like:
a) Ordinary Portland Cement (OPC) of 33,43 and 53 Grade
b) Pozzolana Portland Cement (PPC) with china clay and Fly ash.
CHAPTER-2
BASIC LAYOUT OF CEMENT
2.1 MINING
The process of mining which is use dhereto extract Limes one from the Earths
Opencast mining. The process of mining includes three things:
Prospecting: It is the process of finding potential at place from where very useful &
bulk quantity of limestone can be extracted
Fig 2.1- Mining
Drilling: After providing with a better place for mining, the process of drilling takes
place in which the place is drilled with the drilling machines, for inserting the
dynamites.
4

5. Blasting: After drilling holes, this place is blasted by blasting materials inserted
inside the drilled part to break the huge rocks into pieces.
2.2 CRUSHER
These pieces of rocks are brought near to the crusher & are further processed.
Fig2.2-Raw Material Processing
The crusher crushes these collected rocks into fine pieces of 50 mm size. It just breaks
down the huge rocks into compatible sizes with Impact /hammer mechanismsm
2.3 PRE-HOMOGENIZATION OF RAW MATERIAL:
In this process this crushed material l is arranged in the form of piles
with the help of stacker, to make it available for picking it up for further
processing.
Fig 2.3-Stacker
Here definite pile size is fixed. Laterite [Iron ore] is also mixed in this process. This
piled material is then reclaimed by the Reclaimed.
5

6. Fig 2.4-Reclaimer
The function of Reclaimed is just to reclaim the definite amount of material from the
pile & provide it to conveyor belt, which conveys this picked up material to the raw-
mill. Reclaimed ensures equal distribution of material over conveyor belt. Before
conveying the material to raw-mill, the magnetic separation process takes place to
remove all the magnetic material accompanying the raw material.
2.4 RAW MILL
In Raw-mill section, this conveyed material is transferred into hopper
which feeds and regulated amount of material to the mill. This feeding is carried
out with TFG (Triple Feed Gate), which is a hydraulic gate used to avoid
overfeeding of material in mill. Raw-Mill consists of large rollers, which is used to
grind this crushed material into fine powder. This fine powder is collected & is
stored in Raw-mill silos, which is called Raw-Meal for Kiln.
.
Fig 2.5 -Vertical Roller Mill
The raw materials are usually quarried from local rock, which in some places is
6

7. already practically the desired composition and in other places requires the
addition of clay and limestone, as well as iron ore, bauxite or recycled materials.
The individual raw materials are first crushed, typically to below 50 mm. In many
plants, some or all of the raw materials are then roughly blended in a
"prehomogenization pile." The raw materials are next ground together in a raw
mill. Silos of individual raw materials are arranged over the feed conveyor belt.
Accurately controlled proportions of each material are delivered onto the belt by
weigh- feeders. Passing into the raw mill, the mixture is ground to raw mix. The
fineness of raw mix is specified in terms of the size of the largest particles, and is
usually controlled so that there are less than 5%-15% by mass of particles exceeding
90 μm in diameter. It is important that the raw mix contain no large particles in
order to complete the chemical reactions in the kiln, and to ensure the mix is
chemically homogeneous. In the case of a dry process, the raw mill also dries the
raw materials, usually by passing hot exhaust gases from the kiln through the mill,
so that the raw mix emerges as a fine powder. This is conveyed to the blending
system by conveyor belt or by a powder pump. In the case of wet process, water is
added to the raw mill feed, and the mill product is a slurry with moisture content
usually in the range 25-45% by mass. This slurry is conveyed to the blending system
by conventional liquid pumps.
2.5 PREHEATER
In this the Raw-Meal stored in raw mill silo is first preheated before
feeding it to Kiln section. For heating this material here, mainly pulverized Coal /
Pet coke is used which is procured from various places. This imported coal / pet
coke is first crushed in crusher, then grinded to fine powder in vertical coal mill &
then this powdered coal is stocked in coal mill silos.
Fig 2.6-Preheater Section
A proper amount of coal powder is sucked from coal mill silos & then fired
through burners for preheating the raw meal at Pre-calciner and Kiln.
7

8. 2.6 KILN
Aditya birla Cementplant has a 75 mtrs long kiln having diameter of 5.0 mtrs
for manufacturing OPC clinker supplied by M/s polysiusThyssenkrupp Germany. The
clinker is produced by burning the finely ground raw meal (Mixture of Limestone+
Additives like Bauxite & Laterite) known as kiln feed in a rotary kiln. The
temperature in the burning zone is usually 1400-1450 deg.C and the residence time in
the kiln is 25 minutes. The process taking place in the kiln system consist of a
temperature dependent decomposition of the raw material minerals according to the
nature, followed by a recombination of the liberated free reactive oxides forming
clinker minerals, the most important being C3S(Alite - Tricalcium Silicate), C2S
(Belite - Dicalcium Silicate), C3A (Tricalcium Aluminate)and C4AF
(TetracalciumAlumino Ferrite). The clinker formation sequence as a function of the
temperature can briefly be characterised as follows:
Table 2.1 Clinker Formation Sequence
Temp.
(deg.C)
Description of Process
Type of
Reaction
100 Drying & evaporation of free water Endothermic
100-400 Elimination of absorbed water Endothermic
400-750 Decomposition of clay minerals Endothermic
Kaolinite – Metakaolinite
600-900 Decomposition of Metakaolinite to reactive oxides Endothermic
600-1000 Decomposition of carbonates to free reactive oxides Endothermic
800-1300
Combination of reactive oxides to form intermediate
clinker minerals
Exothermic
1300-1380 Formation of aluminates & ferrites Endothermic
1250-1450 Formation of Alite (C3S) Endothermic
The process takes place in an oxidising environment. Among the chemical process
described above, the reaction rate of the first five groups of reaction comprises the
decomposition of the
8

9. Fig 2.7-General Layout of Rotary Kiln
minerals in the raw meal and the liberation of reactive oxides is determined by the rate
of the heat transfer to the solid material in 6-stage ILC preheater. The reaction rate of
the two last groups of clinker forming reactions is determined in the rotary kiln by the
contact rate of the mutual chemical reactive compounds present in different solid
phases and later in the burning zone by the diffusion of the reactive compounds in the
clinker melt. The overall chemical reactions transforming the mixture of raw material
minerals in the raw meal to the mixture of the clinker minerals in the clinker is
endothermic (heat consuming). Clinker formed in kiln is cooled inside the Polytrack
cooler from 1450 deg.C to around 110 oC and then it is stored in clinker silo having a
storage capacity of 45000 tons.
2.7 COOLER SECTION
In this section, hot clinker coming out from kiln is fed. This hot clinker is
cooled from air stream produced by various cooler fans. This cooled clinker is
stacked in clinker stock piles. The clinker is then fed to cement mill for further
processing.
2.8 CEMENT MILL
The final manufacturing stage at a cement plant is the grinding of cement
clinker from the kiln, mixed with some 4-6% gypsum, into a fine powder. It is
important to obtain a certain specific surface for the finished cement so that hydration
can take place and concrete strength develops within a reasonable time. In addition to
the specific surface, also the particle size distribution influences the strength
properties especially the late strength.
9

10. Fig2.8-CementMill
At Aditya Birla Cement, we have two combi circuit grinding ball mills with roller
press having capacity of 200 tph each. Two dosimat feeders feed the material, clinker
& gypsum. Gypsum is mixed with clinker during grinding operation for retarding
setting time and to increase the workability of cement. Clinker and gypsum in
required proportions are fed to roller press the output of the roller press pass through
V-separator and product of V-separator feed to the single chamber ball mill through
the inlet chute of the mill. The mill inlet consists of a chute for material and a pipe for
sucking in ventilation air. The air intake is provided with a throttle valve so as to
ensure a suitable negative pressure at the inlet and to avoid dust nuisance around the
surrounding area. The grinding is affected by grinding media.. A charge consisting of
25, 20 and 15 mm steel balls is used in chamber for fine grinding. Total
approximately 155 MT grinding media is loaded in each mill.
At the outlet of the mill, the ground material flows through an outlet grate to dynamic
separator by mechanical conveyors, for fine separation as grinding system is closed
circuit mill. Grinding in close circuit makes it possible to obtain a very finely ground
cement. Another advantage is that it is easy to change from one grade of cement to
another grade by adjustment of the separator speed . Cement produced in closed
circuit mill has narrow particle size range and the quantity of 3 to 30 microns fraction
is more in comparison to open circuit mill, resulting in to more late strength. The mill
ventilation air carries a small portion of the fine material, which is dedusted in highly
efficientBag-House.
Fig 2.9-Cement Mill Processing
10

11. Finished product with separator air is passed through multiclones where finished
product is separated and stored in cement silos with the help of mechanical conveyor.
2.9PACKING PLANT
This is the final processing plant in which cement is packed into sacks. There
are 3 packers in the plant. each packer consists of 8 nozzles. The speed of rotation of
the nozzle machine is 4.5 rpm i.e. 36 bags come out every minute out of the plant.
they are then sent to either truck loading or wagon loading through conveyer.
Fig 2.10 Rotary Packer Machine
2.10 DISPATCH
Once the production of cement is complete, the finished product is transferred
using bucket elevators and conveyors to large, storage silos in the shipping
department. Most of the cement is transported in bulk by railway, truck, or barge, or
in 50 kg multiwall paper bags. Bags are used primarily to package masonry cement.
Once the cement leaves the plant, distribution terminals are sometimes used as an
intermediary holding location prior to customer distribution. The same types of
conveyor systems used at the plant are used to load cement at distribution terminals.
Fig 2.11-Truck Loading
11

12. Fig 2.12-Wagon Loading
2.11 CENTRAL CONTROL ROOM (CCR)
To accomplish this long process for definite amount of mixing &
process control for controlling various processes of the plant, as it is operated
fully automatically, that is, no manual operation is needed, for which an upgraded
& better control system is needed. And for making the control system functional
& to take care of various electronic measuring systems, where the field
electronics have its necessity. The plant is equipped with PLCs (Programmable
Logic Controls) controlling the whole processes of the plant from a single office
namely CCR (Central Control Room) with PCs controlling the operation of each
machine in the plant all around 24 hours driving each & every electrical
machines with definite supplies & frequency for accomplishing cement
manufacturing.
Fig 2.13-Central Control Room
12

13. 27
CHAPTER-3
INSTRUMENTATION & AUTOMATION IN CEMENT
3.1. HISTORY & ADVANCES IN AUTOMATION:
The modern cement plant today is equipped with latest technology of automation.
The automation of cement plant is comparable to any industry such as steel, petroleum
etc.
Some of the rate feats of Indian Cement Industry are :
• First programmable controller was introduced in 1978.
• Thyristor/Transistor based analogue variable speed AC drive in various applications.
• First fuzzy control for cement got commissioned in 1987.
• Most powerful advance SCADA/DCS are in use since 1986-2000.
• The cement plants in India are very competitive today; they are very efficient in terms
of thermal & electrical energy consumption, in terms of productivity.
• Some of the latest Plants commissioned in 2004 are operating at 72kWh/ton of
cement. Today we can control plant from remote distance. The same can be
demonstrated at Chittorgarh.
• The CCR of typical Cement Plant of 1 million tons/annum capacity is equipped with
atleast 4-Operator Stations (OS).
• Seven colour desktops are available for Kiln, raw mill & Cooler burning view and
some communication facility such as Phones, Wireless and PA system etc.
3.2. NEEDS OF PROCESS CONTROL AUTOMATION:
Every Industrial Process has three types of main flows:
• Material Flow
• Energy flow
• Information Flow
So the aim of Plant Automation is to identify the Information flow i.e. to take related
information and control Material & Energy Flow in desired manner.

14. 27
3.3. BENEFITS OF AUTOMATION:
 Increase in production
 Improvement in quality
 Reduction in cost
 Optimal use of available resources
 Environmental pollution control
 Safety
3.4. TYPICAL AUTOMATION MEASUREMENT IN CEMENT
PLANT :
 Crusher–
o BRG Temperature
 Stacker & Reclaimer –
o Maximum level of material
o Maximum travel
 Ball Mill –
o BRG Temperature
o Oil flow & Pressure
o Sound level
 Vertical Mill –
o Vibration
o Presence of metal
 Kiln System –
o BRG Temperature
o Shell & Lining temperature
o Position (L.S. UP, DN)
 Larger Motors –
o WNG & BRG Temperature
o Cooling Air flow & PR

15. 27
 Elevators –
o Alignment
o Speed Monitor
 Conveyors –
o Alignment (Belt Sway)
o Speed Monitor
TABLE 3.1. CRUSHER
S.No. Equipment Location Application
1. Apron Feeder Crusher To measure & control speed of apron
feeder
2. Laterite Feeder Crusher To measure & control the feed of Laterite
(Additive)
3. Wireless
Communication
Crusher, Stacker,
Reclaimer
To send & receive information from & to
CCR from moving equipments.
4. Power Measurement Power Calculation
TABLE 3.2. RAW MILL
S.No. Equipment Location Application
1 Weight Feeders Inlet to Mill To feed & control limestone & Laterite to raw mill
inlet in raw mill.
2 Metal Detector To detect metal pieces on belts.
3 Metal Separator To separate metal pieces from raw material which is
detected by metal detector.
4 Power Mill Power
TABLE 3.3. ESP, GCT & PREHEATER
S.No. Equipment Location Application Other information
1. Thermocouple Bottom of
cyclone
For cyclone
material
temperature.
K Type
2. Thermocouple top of
cyclone
For cyclone gas
temperature.
K Type
3. Draught
(PR Tx.)
Bottom of
cyclone
For cyclone
bottom draught
Gives idea of material feeded in
cyclone & also idea of cyclonic
action taking place
4. ESP panel ESP Panel To measure &

16. 27
control kV & mA
TABLE 3.5.PACKING PLANT
S.No.Equipment Location6 Application Other
information
1. Level sensors In various
hoppers/tanks, feeding
MAT. To PKR.
To sense level E &H/ Sapcon
make
2. Proximity
Switches
Bag conveying belts To sense belt running
3. Limit
Switches
Packer For providing various
safeties in PKR like
pendulum switch, pull cord
surrounding PKR etc.
4. Solenoid
Valves
Packer For performing various
actions
Involved in bag filling to
evacuation.
TABLE 3.6.KILN & COOLER SECTION
S.No. Equipment Location Application Other information
1. Thermocouple Kiln inlet For measuring Kiln inlet
temperature.
K Type
2. RTD Kiln Roller For measuring kiln inlet
temperature
Shoe type RTD
3. RTD Kiln Gear
Box
For measuring kiln roller brg
temperature
Simple PT-100 RTD
4. RTD Kiln Motor For measuring kiln G.Box
oil temperature
Simple PT-100 RTD
5. Analyzers Kiln Inlet For measuring kiln motor
WDG & BRG. Temperature
02 0-10%, co 0-2%,
nox 0-3000 PPM
6. Tacho Kiln Drive Kiln Speed Hubner make
7. Solid flow
Feeder
C.F.Silo Material feed to Kiln J&N, Ranchi
TABLE 3.4. BELTS
S.No. Equipment Location Application
1. Speed Moniter Tail End To sense the rotation.

17. 27
8. ESP panel ESP panel To measure & control kV &
mA
Hind Rectifier
controller
CHAPTER- 4
SENSOR
A sensor is a device that measures a physical quantity and converts it into a signal
which can be read by an observer or by an instrument. For example, a mercury-in-glass
thermometer converts the measured temperature into expansion and contraction of a
liquid which can be read on a calibrated glass tube. A thermocouple converts temperature
to an output voltage which can be read by a voltmeter. For accuracy, all sensors need to
be calibrated against known standards.
4.1. USE
Sensors are used in everyday objects such as touch-sensitive elevator buttons and
lamps which dim or brighten by touching the base. There are also innumerable
applications for sensors of which most people are never aware. Applications include cars,
machines, aerospace, medicine, manufacturing and robotics.
A sensor's sensitivity indicates how much the sensor's output changes when the measured
quantity changes. For instance, if the mercury in a thermometer moves 1 cm when the
temperature changes by 1 °C, the sensitivity is 1 cm/°C. Sensors that measure very small
changes must have very high sensitivities.Ideal sensors are designed to be linear. The
output signal of such a sensor is linearly proportional to the value of the measured
property. The resolution of a sensor is the smallest change it can detect in the quantity
that it is measuring.
4.2. LEVEL SENSOR
4.2.1. GENERAL APPLICATION OF LEVEL SENSOR :
Level Sensors designed to provide accurate and reliable level information of Solids
(Powder & Lumps), Liquids and Slurry
applications for point level detection in storage
Bins, Silos, Hoppers, Tanks and any other
vessels where material is stored, processed and
discharged even at high temperature/pressure.
Figure 4.1 Level Sensor

18. 27
4.2.2. FUNCTION OF LEVEL SENSOR :
The oscillator generates low-power RF signal which is used to provide signals
equal in frequency phase and amplitude to both, active section and shield section of the
probe. The signal applied to the shield is held constant by use of compensating amplifier.
The detector is then used to compare the fixed shield signal with active signal which
varies with the dielectric constant of the material in contact with the probe. Difference in
the signals compared by the detector cause the output relay to activate. The contacts of
the output relay to when activated are used to indicate the presence or absence of material
in the vessel at the probe level.

19. 27 CHAPTER-5
RESISTANCE THERMOMETER
Resistance thermometers, also called resistance temperature detectors or resistive
thermal devices (RTDs), are temperature sensors that exploit the predictable change in
electrical resistance of some materials with changing temperature. As they are almost
invariably made of platinum, they are often called platinum resistance thermometers
(PRTs).
5.1. TYPES

20. 27
Film thermometers have a layer of platinum on a substrate; the layer may be
extremely thin, perhaps one micrometer. Advantages of this type are relatively low
cost and fast response. Such devices have improved in performance although the
different expansion rates of the substrate and platinum give "strain gauge" effects
and stability problems.
Wire-wound thermometers can have greater accuracy, especially for wide
temperature ranges. The coil diameter provides a compromise between
mechanical stability and allowing expansion of the wire to minimize strain and
consequential drift.
5.2. FUNCTION
Resistance thermometers are constructed in a number of forms and offer greater
stability, accuracy and repeatability in some cases than thermocouples. While
thermocouples use the Seebeck effect to generate a voltage, resistance thermometers use
electrical resistance and require a power source to operate. The resistance ideally varies
linearly with temperature. Resistance thermometers require a small current to be passed
through in order to determine the resistance. The two most common ways of measuring
industrial temperatures are with resistance temperature detectors (RTDs) and
thermocouples. Selection criteria: - Temperature, time, size, and overall accuracy .
CHAPTER-6
PROGRAMMABLE LOGIC CONTROL
6.1. INTRODUCTION
A programmable logic controller (PLC) or programmable controller is a digital computer
used for automation of electromechanical processes, such as control of machinery on
factory assembly lines, amusement rides, or lighting fixtures. PLCs are used in many
industries and machines, such as packaging and semiconductor machines. Unlike general-
purpose computers, the PLC is designed for multiple inputs and output arrangements,
extended temperature ranges, immunity to electrical noise, and resistance to vibration and
impact. Programs to control machine operation are typically stored in battery-backed or
Figure 5.1 Film thermometers
Film thermometers Film
thermometers
Figure 5.2 Wire-wound thermometers

21. 27
non-volatile memory. A PLC is an example of a real time system since output results
must be produced in response to input conditions within a bounded time, otherwise
unintended operation will result.
;
6.2. WHAT IS PROGRAMMABLE LOGIC CONTROL ?
A programmable logic controller (PLC) is a special data processor used as controller for
machines in industrial processes. As a part of process control, a programmable logic
controller is used to monitor input signals from a variety of input points which report
events and conditions occurring in a controlled process. During the execution of a stored
control program, they read inputs from the controlled process and, per the logic of the
control program, provide outputs to the controlled process.
On primary basis PLC is having following advantages over any other controlling element
invented before its invention :-
 Cost effective specially for controlling complex systems.
 Flexible and can be re-applied to control other systems quickly and without much
manipulation in the programme.
 Computation abilities allow us do more sophisticated control.
 Trouble shooting allows us to make programme more efficiently, hence reduce
down time.
The purpose of a PLC was to directly replace electromechanical relays as logic
elements, substituting instead a solid-state digital computer with a stored program,
able to emulate the interconnection of many relays to perform certain logical tasks.

22. 27
6.3. BLOCKS OF PLC
6.3.1. Inputs
6.3.2. Output
6.3.3. Memory
6.3.4. Central Processing unit(CPU)
6.3.5. Power Supply
6.3.1. INPUTS
Input signals are real time signals. They may be analogdigital, lowhigh
frequency etc. But in general case they are represented as various voltages to the
programmable controller they can be from Switches, Pushbuttons, Proximity sensors etc.
6.3.2. OUTPUTS
Output signals are generally a digital signal which is applied to three categories of
output devices.
• Discrete (Pilot lights, Solenoid Valves etc.)
• Register (Drive Panel meters)
• Analog (Drive signals to variable speed)
Figure 6.1 PLC Block Diagram

23. 27
6.3.3. MEMORY
It is the main storage area of a PLC, which is used to hold the set of instruction to
be executed by the processor/programming devices. Its size may very from 256 bytes to
several mega bytes.
6.3.4. CPU
Central processing unit is the brain of PLC controller. CPU itself is one of the
microcontroller. It perform task which are necessary to fulfill the function of PLC. Earlier
it was 8 bit microcontroller such as 8051 but now these are 16 and 32 bit
microcontrollers. CPU takes care of following functions :-
• Scanning I/O devices (BUS traffic control)
• Program execution
• Memory Read/Write
• External device communication
6.3.5. POWER SUPPLY
Power supply unit converts line voltage to a required voltage which is needed by
solid state components. Most PLC controllers work on 24 volt DC to 220 volt DC.
6.4. MAIN ELEMENTS OF PLC
While manufacturing as well as while programming a PLC following things are
necessary to keep in mind both by the manufacturer and user, they are :
6.4.1. Ladder Logic
6.4.2. Programming
6.4.3. PLC Connection
6.4.4. Ladder Logic Inputs
6.4.5. Ladder Logic Outputs
6.4.1. LADDER LOGIC
Ladder logic is the main programming method used for PLC’s. Ladder logic has
been developed to mimic relay logic. By selecting ladder logic as the main programming
method, the amount of retraining needed for engineers and trades people was greatly
reduced. Modern control system still include relays, but these are rarely used for logic.
The example is shown in figure 2 does not show the entire control system, but only the
logic. When we consider a PLC these are inputs, outputs and the logic. Figure 2 shows a
more complete representation of PLC.
Here, there are two inputs from push buttons. We can imagine the inputs as
ctivating 24 volt DC relay coils in the PLC. This is turn drives an output relay that
switches 115 volt AC, which will turn on a light. Note, in actual PLC’s inputs are ver

24. 27
relays, but outputs are often relays.
The ladder logic in the PLC is actually a computer program that the user can defined and
modify. Notice that both of the input push buttons are normally open, but the ladder logic
inside the PLC has one normally open contact, and one normally closed contact. Ladder
logic in the PLC does not needs to match the input and outputs.
The figure shows a simple ladder logic which consist of one NO-contact, NC-contact and
a contactor, can be consider as a simple relay controller.
6.4.2. PROGRAMMING
The first PLC’s were programmed with a technique that was based on relay logic
wiring schematics. This eliminated the need to teach the electrician, technicians and
engineers how to program a computer – but, this method has stuck and it is the most
common technique for programming PLC today. Another example of ladder logic is
shown in figure.
To interpret the diagram imagines that the power is on the vertical line of the left hand
side, we called this the hot rail. On the right hand side is the neutral rail. In the figure 3
there are two rungs, and on each rung there are combinations of inputs (two vertical lines)
and outputs (circle). If the input are
opened or closed in the right combination
the power can flow from the hot rail,
through the inputs, to power the outputs,
and finally to the neutral rail. An input
can come from a sensor, switch or any
other type of sensor. An output will be
some device outside the PLC that is
switched ON or OFF, such as lights or
motors. In the top rung the contact are
normally open and normally closed. This
means if input A is on and input B is off,
then power will flow through the output and activate it. Any other combination of input
Figure 6.2 Ladder Logic
Figure 6.3 Example of Ladder Logic

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PROCESS
P L C
Connections
to Actuators
Feedback from
Sensors/Switche
s
Figure 6.4 PLC Connection
values will result in the output X being off.
6.4.3. PLC CONNECTIONS
When a process is controlled by a PLC it uses input from sensors to make
decisions and update outputs to drive actuators, as shown in figure 4. the process is a real
process that will change over time. Actuator will drive the system to new states (or
modes of operation). This means that the controller is limited by the sensors available, if
an input is not available, the controller will have no way to detect a condition.
The control loop is a continuous cycle of the PLC reading inputs, solving the ladder
logic, and then changing the outputs. Like any computer this does not happen instantly.
Figure 4 shows the basic operation cycle of a PLC.
When power is turned on initially the
PLC does a quick sanity check to ensure
that the hardware is working properly. If
there is a problem the PLC will halt and
indicate there is an error. For example, if
the PLC battery is low and power was
lost, the memory will be corrupt and this
will result in a fault. If the PLC passes
the sanity checks it will then scan (read)
all the inputs.
After the input values are stored in memory the ladder logic will be scanned (solved)
using the stored values not the current values. This is done to prevent logic problem when
inputs change the output will be scanned (the output values will be changed). After this
the system goes back to do a sanity check, and the loop continues every scan. Typical
times for each of the stages are in the order of milliseconds.
6.4.4. LADDER LOGIC INPUT
PLC inputs are easily represented in ladder logic. There are three types of inputs shown.
The first two are normally open and
normally closed inputs, discussed
previously. The IOT (Immediate
Input) function allows input to be
read after the input scan, while the
ladder logic is being scanned. This
allows ladder logic to examine input
values .
6.4.5. LADDER LOGIC OUTPUT
In ladder logic there are
II
T
Normally Open, an active input X will
close the contact and allow power to
flow
Normally Closed, power flows when
the input X is not open
Immediate inputs will take current
values, not those from the previous
input scan. (NOTE: this instruction is
actually an output that will update the
input table with the current input
values. Other input contacts can now be
used to examine the new values.)
X
X
X
Figure 6.5 Ladder Logic Input

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multiple type of outputs, but these are not consistently available on all PLC’s. Some of
the output will be externally connected to devices outside the PLC, but it is also possible
to use internal memory locations in the PLC.
Three types of output are shown in figure.
The first is the normal output, when
energized the output will turn on,
and energize an output.
The circle with a diagonal line
through is a normally on output.
When energized the output will turn
off. This type of output is not
available on all PLC types. When
initially energized the OSR (One
Shot Relay) instruction will turn on
for one scan, but then be off for all
scans after, until it is turned off.
The L (latch) and (unlatch)
instruction can be used to locks output on. When an L output is energized the output will
turn on indefinitely, even when the output coil is reenergized. The output can only be
turned off using a U output. The last instruction is the IOT (Immediate Output) that will
allow outputs to be updated without having to wait for the ladder logic scan to be
completed.
6.4.6. COMMUNICATIONS
PLC’s have built in communications ports usually 9-Pin RS232, and optionally
for RS485 and Ethernet. Modbus, BACnet or DF1 is usually included as one of the
communications protocols. Other options include various field buses such as DeviceNet
or Profibus. Other communications protocols that may be used. Most modern PLCs can
communicate over a network to some other system, such as a computer running a
SCADA (Supervisory Control and Data Acquisition) system or web browser.
PLCs used in larger I/O systems may have peer-to-peer (P2P) communication between
processors. This allows separate parts of a complex process to have individual control
while allowing the subsystems to co-ordinate over the communication link. These
communication links are also often used for HMI devices such as keypads or PC-type
workstations. Some of today's PLCs can communicate over a wide range of media
including RS485, Coaxial, and even Ethernet.
CHAPTER-7
OS
R
When power is applied (ON)
the
output X is activated for the left
output, turned off for the output
An input transition on will cause
the output x to go on for one
scan
X
X
X
Figure 6.6 Ladder Logic Output

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CONCLUSION
It was just like a dream come true for me to pursue training in Aditya Birla
Cement ltd. It was really a learning experience for me to have a feel of different
Industrial aspects.
In this period I have Learnt those things, which I could not get from books i.e., the
practical experience under the guidance of learned professionals.
Special thanks for my college and Aditya Birla Cement Work .
REFRENCE