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A PROJECT REPORT ON

PLCs AND DRIVES FOR AUTOMATION SYSTEM IN

INDUSTRIAL ENVIRONMENT

BACHELOR OF TECHNOLOGY

IN

ELECTRICAL AND ELECTRONICS ENGINEERING

Submitted By

RAGHAVENDRA M.R

Under the esteemed guidance of

Sri ADISESHANAIK

Sr. MANAGER (ETL DEPT)

VIZAG STEEL PLANT

DEPARTMENT OF

ELECTRICAL AND ELECTRONICS ENGINEERING

CMRIT

ITPL, BANGALORE

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CERTIFICATE

This is to certify that the project work entitled “PLCs AND DRIVES FOR

AUTOMATION SYSTEM IN INDUSTRIAL ENVIRONMENT” is a

bonafide work carried out by Raghavendra M.R, student of CMRIT Engineering college

studying in 3rd

year

B.Tech. Department of Electrical and Electronics Engineering.

The project was carried out from 17th

Jul to 27

th Jul , 2013 and completed successfully

in the Department of Electro Technical Laboratory (ETL), Vizag Steel Plant,

Vishakapatnam successfully.

Sri Adhisesha Naik

Sr. Manager, ETL (LMMM)

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ACKNOWLEDGEMENT

I extend my gratitude to The Head of the Department of Electrical and

Electronics Engineering of CMRIT Engineering College, Training and Development

Centre, Visakhapatnam Steel Plant for giving me this opportunity to undertake the

project.

I greatly acknowledge the assistance given by my Principal without which my

exposition to the inquisitive concepts in the project would have achieved.

I deeply acknowledge the support and never ending encouragement given by the

faculty of EEE department – CMRIT Engineering college to accomplish this task.

I express my deep sense of gratitude and indebtedness to Shri AdiseshaNaik, Sr.

Manager, Electro Technical Laboratory (ETL), Vizag Steel Plant for his inspiring

guidance, untiring efforts and constant encouragement, support and suggestions for

improvement during the course of my project.

I would like to convey my hearty gratitude to L.Jyothi Assistant Manager,

L.V.Ramesh Deputy Manager, ETL LMMM, Vizag Steel Plant for providing all

necessary facilities and helpful suggestions.

I also convey my wholehearted thanks to all in Vizag steel, faculty of our college and

other members who helped in bringing out this project.

Raghavendra M.R

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Content

CHAPTER – 1

Overview of Visakhapatnam steel plant

CHAPTER – 2

Overview of LMMM

Bloom charging and discharging Equipment

Mill Equipment

CHAPTER – 3

Overview of GE-FANUC PLC

Networking of LMMM

Ethernet Switch

UTP Cables

Optical Fibers

Media Converters

CHAPTER – 4

Conclusion

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RASHTRIYA ISPAT NIGAM LIMITED

VISAKHAPATNAM STEEL PLANT (VSP)

OVERVIEW OF VISAKHAPATNAM STEEL PLANT

Steel comprises one of the most important inputs in all sectors of economy.

Steel industry is both a basic and a core industry. The economy of any nation depends

on a strong bas of iron & steel industry in that nation. Iron & steel making, as India

has known a craft for a long time. The growth of steel industry in India can be

conveniently studied by dividing the period into pre & post independence era. By

1950, the total installed capacity for ingot steel production was 1.5 million tones per

year. The capacity increased by 11 folds to about 16 million tones by nineties.

Presently in India, steel products are being produced from 4 different sources, namely

Integrated steel plants, Mini Steel Plants, Re-rolling Mills, Alloy & special steel

Plants. In Integrated steel plants, naturally occurring raw materials are processed into

finished (steel) products in various stages. These plants are highly capital intensive. If

needs approximately Rs.2500 crores of money to establish a 1 million tonne per year

steel plant.

Visakhapatnam Steel Plant is an integrated steel plant, constructed with

former USSR collaboration. It is the first based and integrated steel plant constructed

in South India, with many modern technological features, some of them for the first

time in the country. Among these are:

7 Meter tall coke ovens

Dry quenching of coke

On ground blending of sinter base mix

Conveyer charging and bell less top for Blast Furnace

Cast house slag granulation for Blast furnace

100% continuous casting of liquid steel

Gas expansion turbine for power generation utilizing Blast Furnace top gas

pressure

Hot metal desulphurization

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Extensive treatment facilities of effluents for ensuring proper environmental

protection

Computerization for process control

Sophisticated high speed and high production rolling mills.

The soviet design organization, GIPROMEZ designed the coke oven and coal

chemical plant, sinter plant and Blast Furnace. The seven meter tall coke oven

batteries with dry quenching were designed by MECON of Ranchi. The Remaining

facilities have been designed by DASTUR & CO, who are the principal consultants

for VSP.

Visakhapatnam steel plant has the following major production facilities:

3 coke oven batteries of 67 oven each having 41.6 cu.m volume

2 sinter machines of 312 Sq.m. area

2 Blast Furnaces of 3200 Cu.m useful volume

Steel Melt shop with three LD converters of 150T capacity

Light and Medium Merchant Mill of 710,000 tonnes per year capacity

Wire Rod Mill of 850,000 tonnes per year capacity

Medium Merchant & Structural Mill of 850,000 tonnes per year capacity

Captive power plant with a total generating capacity of 280 MW

Air separation plant for production of liquid Oxygen and Liquid Nitrogen

Extensive facilities have been provided for repair, maintenance as well as

manufacture of spare parts. There is a structural shop, Machine shop, foundry (with

wood working shop, forge shop), loco repair shop, Utility Equipment Repair shop.

There is Electrical Repair shop (ERS), for repair of Electrical Equipment like motors,

transformers etc.

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ELECTRICAL & ELECTRONICS DEPARTMENTS OF VSP

VSP has got mainly three working divisions in each production departments.

1. Electrical

2. Mechanical

3. Operation

Shop electrical department is the owner of all electrical equipments in each

production/Maintenance zone. This department is headed with an HOD (E) and

will be reporting to concerned zonal in charge.

Electro Technical Laboratory (ETL) department is mainly responsible for

maintenance/breakdown analysis/commissioning activities/spare procurement for

all electronic related equipments in VSP. The equipments are Drives (AC/DC), PLCs,

UPS/SPS, CNC machines, Data Acquisition Systems. Each department shall have one

site in charge who reports to zonal officer. It has got a central laboratory where

repair of failed PCBs is done.

Instrumentation department is responsible for maintaining various gauges,

monitoring systems, transducers etc.,

The entire plant and township is well connected with local

telecommunication network. And also, in individual shop, there internal

communication system. All these are maintained by Telecommunication

department.

The Information Technology (System) department, though it is a special

department coming under Computer Engineering, can be considered as electrical

and electronics based upon the huge communication network they have in the

entire plant.

Technical Services (Electrical) department is mainly responsible for

analyzing the major breakdowns, condition monitoring of several equipment etc.,

Design & Engineering (Electrical) is responsible for preparing the

specification and coordinating with the customer department for up gradation of

obsolete equipments.

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Central Maintenance Electrical department mainly deals with maintenance of

higher capacity electrical machines like HT motors.

Distribution Network (DNW) maintains High Tension electrical lines in the

plant.

Electrical Repair Shop (ERS) is responsible for repairing electrical machines

such as motors, transformers etc.,

INTRODUCTION TO TECHNOLOGICAL ADVANCEMENT

Any process can be classified into three basic units.

1. Power source

2. Control system

3. Driven system

During past several years, we find there is a stupendous advancement in the

control system technology. Where as the driven system and the Power source have taken

relatively less advancement. Few examples of control system are shown below

1. Programmable Logic Controllers (PLC)

2. AC/DC drives

3. Proportional controllers

4. CNC systems

5. UPS/SPS systems

DETAILS OF AUTOMATION SYSTEM IN VSP

LEVELS OF AUTOMATION IN LMMM:

Programmable Logic Controllers (PLCs) provided at level-1 finally control the

process equipment directly, each in its own area for sequencing and interlocking

functions. The system envisaged is interfaced with the main and auxiliary drive

analogue/digital control system so as to perform as one integrated unit.

The control at level-2 is basically decentralized and distributed in concept so as to

offer a higher degree of operational flexibility. A number of microcomputer subsystems

provided at this level, operate and control functions for the equipment distributed in

various areas of the mill.

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A Production data Computer is provided at Level-3 for data logging, tracking of

Material, Storage of production Programs, data acquisition etc…

For operator's communication with the system dialogue terminals (VDU and keyboard

units) have been envisaged in control pulpits of the shop. Printers for hard copy print out

of rolling schedule, shift reports, etc. are provided for. Some production zones are

equipped with Man Machine interface (MMI or Human Machine Interface – HMI).

The control system envisaged is basically automatic with provision of manual control

locally for the equipment to take care of local disturbance during operation and also the

maintenance needs.

Following process and drive control functions will generally be performed by the

control system:

LEVEL-1:

* Starting/interlocking and sequence control of drives.

* Collection and printing of mill faults and display of mill faults

LEVEL-2

* Storage of current production programs.

* Generation of set point values and automatic control of main and auxiliary drives.

* Position control of drives.

* Data communication functions

LEVEL-3:

* Acquisition and compilation of production data

* Generation, storage and distribution of production programs

* Generation of production reports

* Organization of set point values

* Automatic on-line material tracking up to dispatch

* Output to VDUs

* Communication with Level-2 and plant level information exchange.

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OVERVIEW OF LMMM

BLOOM CHARGING AND DISCHARGING EQUIPMENT

Blooms from the continuous casting department will be received

with the help of 16-ton magnet crane for charging on to the charging grids of

LMMM. Three charging grids of capacity 150 tons each are available for receiving

the blooms. Defective blooms can be sorted out and rejected on to two take off grids

provided along the charging roller table. The charging grids are at +800mm. Blooms

from the charging grid are fed on to the charging platform. Blooms so elevated are

weighed piece by piece and tilted if necessary with the help of hook type tilter before

feeding into the reheating furnaces. Blooms fed to the furnaces with the help of

furnace approach roller table are electrically stopped at the proper position in front of

the furnace and pushed simultaneously in to rows into the furnace with the help of

hydraulic pushers. Blooms are heated to a temperature of 1100 to 1200deg.cel and

discharged by a discharging device on to the furnace delivery roller table on by one.

There are four furnace discharging machines. It will be possible to supply fully heated

blooms once in every 26.5 seconds to the mill, however, normal time being 36

seconds. The blooms are then carried on the mill approach roller table through a

hydraulic de-scalar before feeding to the first stand of the breakdown group.

The bloom charging grids are rope transfer type designed to

handle 250mm x 320mm blooms 5.5 to 6.6 mts long. The charging and discharging

equipment, the furnace and the mill are designed for the following bloom tolerances:

Thickness tolerances: 250mm +/- 3%

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Width tolerances: 320 mm +/- 3%

Diagonal differences: +/- 3.5 %

Deviations from straightness: Max. Permissible height of arc chord

Shall be 15 mm per meter measure Length, with

the total maximum of 80mm

Length tolerance: +/- 80 mm

The charging roller table and the furnace approach roller table are designed

with a speed of 1.2mts per second and the solid forged steel rollers are individually

drives. Bloom elevator (with one standby) is of chain type and has a cycle time of 21

seconds.

The in-line weigh scale has a weighing accuracy of +/- 0.1% of the net weight.

Hydraulic descaler is designed with a descaling pressure of 186 Kgs. At the end of

furnace delivery roller table an emergency hot bloom reject grid and pusher is

provided to remove defective blooms from the furnace. The defective blooms

collected by the mill crane can be taken back to the bloom storage yard with the help

of a transfer car. The bloom charging equipment are so designed that in case of

emergency the furnace can be emptied from the charging side by reversing the

walking beams of the furnace and discharging hot blooms on to the furnace approach

roller table. The furnace approach roller table, weigh scale, bloom elevator, the

charging roller table and reject grid are designed to handle the hot blooms emptied

from the furnace.

Mill equipment

Breakdown group: Breakdown group (billet mill part) has seven continuous

stands, with two horizontal stands 850 mm X 1200 mm followed by 5 alternate vertical

and horizontal stands, of which 3 are of 730 mm X 1000 mm and two are of 630 mm X

1000 mm. The total motor power for the breakdown group is 6,100Kw. The speed of

rolling is 1.3 to 1.6 mtr/sec.

An in-line four-crank shear, installed behind the breakdown group is designed to crop

both ends and to cut fixed billet lengths between 5 and 12.0 mts or to perform optimum

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yield dividing. Billets fed to the bar mill are only cropped at the front and back ends,

while the billets for sale and for wire rod mill are cut to lengths 5 to 12 mts and 10.4 mts

respectively. When cutting fixed lengths, rest ends up to 1.5 mts are guided into the

scrap bucket and rest ends above 1.5 mts are transported over the closed recoil roller table

sections to a location where they are diverted into a short length disposal cradle.

Detection of rest end billet of above 1.5mts is performed automatically.

Billets rolled for sale and for wire rod mill are stamped in-line by a stamping machine

(with one standby) installed before the billet cooling bed in order to avoid cast mix-up.

If optimum yield cutting is performed, as in case of billets for wire rod mill, the total

finished length will be detected before the first length out is made. A quick computer

calculation decides the length before cutting in order to get three equal pieces and one

minimum crop cut at each end. Depending on the production programmed, blooms will

be rolled in sequence into billets for wire rod mill or sale and for the bar mill. The

standard rolling patterns for the bar mill (BM) and the billet cooling bed (CB) are:

a) All blooms to BM

b) All blooms to CB

c) One bloom to CB one bloom to BM (1:1)

d) Two blooms to CB two blooms to BM (2:2)

e) Three blooms to CB two blooms to BM (3:2)

f) Five blooms to CB two blooms to BM (5:2)

In addition to above, the following rolling patterns are also possible:

g) Two blooms to CB one bloom to BM (2:1)

h) Three blooms to CB one bloom to BM (3:1)

i) Five blooms to CB one bloom to BM (5:1)

Billet cooling bed and billet shear: The major facilities provided are the shifting

drum type transfer to shift cut-to-length billets on the move followed by two 12mts wide

turn over type billet cooling beds. Transfer of billets to the cooling beds is by feeder

screws which, after one full revolution, push the billet moving on the cooling bed roller

table sidewise to a break plate where it comes to rest after a short braking distance.

While the next billet is being delivered the billet resting on the brake plate is

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simultaneously transferred through the feeder screw via short chute to the cooling bed

rake system. To ensure discharging of the billets coming in one by one a lead is

produced immediately at the back of the four crank shears to produce the defined gap

between the billets.

The cooling beds are designed as turnover type beds and consist of stationary and

moving rakes with notched surface. They are designed for 2-row covering with 5 to 6

mts and for single covering with 7 to 12m long billets.

During the turnover operation, the moving rakes turn the billets over 90deg in each

stroke, thus moving them on one pitch on the stationary rakes. Each cooling bed is

designed for a capacity of 200tons per hour to cool to approx. 400deg.cel with natural

convection. From the loading grid provided at the end of the cooling bed, billets will be

removed in batches by 16-ton capacity magnet cranes and stored in the intermediate billet

storage area.

Billets produced will have the following tolerance:

Billet size : 125 X 125 mm

Side length : +/- 2 mm

Edge round : 4 mm max

Straightness : 0.0025 X billet length

Length tolerance for 5-12 mts : +/- 25 mm

Fixed length : +/- 100mm

Billets rolled for bar mill are fed in full length to the two-strand roller hearth furnace

before feeding to the bar mill. A switch is arranged in front of the furnace to guide the

full length billets for bar mill, to either of the two strands.

Billets normally arrive at a surface temperature of about 1100deg.cel. at the roller

hearth furnace. In case of two-strand rolling, billets will be heated and soaked to the

discharging temperature of 1150deg.cel. At single strand rolling the billets will be heated

and soaked to a discharging temperature of 1130deg.cel. The temperature of the billets

when entering the first stand of the bar mill will be normally about 1100deg.cel. The

main drive and other connected equipment of the bar mill are, however, designed to roll

billets received at the first stand at a minimum temperature of 1050deg.cel.

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The productivity of the furnace is 200 tones per hour both in case of single as well

as double-strand rolling. The furnace is also designed for oscillating billets inside the

roller hearth during stoppages.

Roughing group: The continuous multi-line bar mill comprises an eight-stand

roughing train, two five-stand intermediate trains and two four-stand finishing trains.

This mill arrangement permits to roll smaller size sections such as round, flats and angles

in two strands. In case of single-strand rolling it is also possible to prepare the complete

second intermediate and finishing mill for a new product size in a parallel rolling process.

The roughing group has one horizontal stand 610 X 1220mm, Three horizontal

stands 585 X 1220 mm and four horizontal stands 460 X 1060 mm. The total motor

power for the roughing group is 6000kw. The roughing group of stands have combined

gear box and pinion stands with casings of fabricated steel. Roll changing is by roll

changing rigs. Stands 5H to 8H can be retracted from pass line when not required for

rolling programmer.

Intermediate group: Intermediate group is arranged in multi-line arrangement.

Each line has five stands with four horizontal stands of 380 X 850 mm and one vertical

stand of 360 X 600 mm,. The motor power for each line is 4.300kw, i.e., a total of

8.600kw for the intermediate group. The advantages of the multi-line arrangement are

fully utilized for rounds 28 mm size, 25 mm squares and 40 mm channels. For all other

sizes the arrangement works like semi-multi line. The intermediate stands have

combined gear box and pinion stands with casing of fabricated steel. The roll changing is

done by complete stand changing with the help of quick stand-changing arrangement.

Finishing group: The two finishing groups are arranged to roll in single strand

only. Each finishing group has four alternate vertical and horizontal stand of 335 X 600

mm. The motor power for each line is 3,400kw i.e., a total of 6,800 kw for the two

finishing groups.

The finishing groups have combined gear box and pinion stands with casing of

fabricated steel. The roll changing is done by complete stand changing with the help of

quick stand-changing arrangement.

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The total number of stands including those in the break-down group is 33. The

mill arrangement therefore, has the flexibility to adopt 24 to 29 passes as required by the

production programme. The roll neck bearings for all the stands are of anti-friction type.

The maximum finishing speed is 20 mts per second on 14 mm dia plain rounds.

Mill shear: Shears for cropping and emergency cutting are arranged ahead of the

first roughing stands and up-stream of the intermediate mill. Snap shears are arranged for

emergency cuts ahead of the finishing mills. A pinch roll unit is located adjacent to the

pendulum shear between the furnace and the first roughing stand. This pinch roll set will

be used in case feeding problems are faced on the first-stand of the roughing group. It

can also be used in case of mill troubles and after emergency cutting to feed the billet

remainder to the pendulum shear for size reduction into scrap pieces. In addition to

cutting multiple lengths as required by the rotary shear after the finishing stands, test-

piece can also be cut on this shear, which will be directed to the laboratory by a belt

conveyor. This rotary shear will be located after the water cooling stretch installed for

the TEMPCORE process. Space has been provided for locating one surface and one

dimension measuring unit between the last stand of the finishing group and the water

cooling stretch, in future.

Water cooling stretch: One cooling stretch is provided in each of the run-in

roller tables to the cooling beds immediately before the rotary shears. These cooling

stretches are such that reinforcing bars from 10mm to 25mm dia can be rapidly cooled

down from rolling temperature to a minimum temperature as per process know-how of

TEMPCORE to improve mechanical properties. Plain rounds from 12 mm to 40mm dia

also can be cooled to reduce secondary scaling. These cooling stretches are shiftable and

can be retracted from the pass line when other products are rolled.

Cooling bed: One double-sided rake type cooling bed is provided with 130 m X

11 m equivalent to an area of 1430 sq.m on each side. The double-sided cooling bed is

provided with row of axial fans. A switch is provided ahead of cooling beds permitting

both the cooling beds to be fed simultaneously when rolling in two-strands and the two

cooling beds in alternating order under single-strand rolling conditions. The run-in trough

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in front of each side of cooling bed within the switch area and inside the cooling bed area

serves to separate and slow down the successively arriving product lengths. A 2-slide

mechanism is provided for this deceleration of rolled stock from rolling speed. Each side

of cooling bed is provided with primary notch spacing of 130 mm and secondary notch

spacing of 65/65 mm. The bars entering the cooling beds at rolling temperature will be

discharged at temperatures of about 80deeg.cel. And below for section and about

135deg.cel.and below for rounds. The first part of the cooling area comprises a

straightening plate grid which in the high temperature area provides additional support to

the material and thereby exerts the material straightening effect by ensuring slow and

uniform cooling. On the cold side of the rake type cooling area an aligning device is

provided which consists of continuously operating driven and idling rollers provided with

rake notch profile and brake shoes which are moved under the action of a pull-rod

system.

The bars are transferred to the discharge roller table downstream of the

cooling beds. This transfer facility comprises two independently operating chain type

transfers. Chain transfer 1 receives the bars coming from the rake portion one by one and

collects them into groups of 2 to 8 bars max. Conforming to the straightening strand

number, with spacing corresponding to those of the strands in the straightener and hands

over to chain transfer 2. Then chain transfer 2 transports the bar groups to the cooling bed

discharge roller table.

Cold shear: Each of the 2-finishing lines has a 500 ton cold shear with 1300 mm

blade width. The shear blades are changed with the help of quick changing facilities with

cassettes. Rounds upto 20 mm dia as well as squares and flats will be cut with plain

knives, and rounds above 20mm as well as angles, channels and T-bars will be cut by

means of profiled knives. Desired finished lengths between 5 mts and 12 mts and/or

maximum 24 mts will be set by means of 2-electrically traversible gauge carriages which

are attached to a girder-type gauge.

Tail ends less than 3 mts length which cannot be transported by the roller table

will either be cut into scrap pieces by the cold shear or in case they should lie between the

bar layers, be manually removed and discharged into a cradle near the cold shear. All

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tail- ends longer than 3 mts up to the relevant finished length will be directed to a

separate short separation device.

Strapping Machine is used for applying Straps over the rod bundles. Seven no. of

Strapping machines are there in LMMM. Strapping machines 1,2&3 come under control pulpit

9.Machines 4,5 & 6 come under control pulpit 10.Machine 7 is stand by.

Programmable logic controller (PLC)

A. Introduction

Generally speaking, process control system is made up of a group of electronic devices

and equipment that provide stability, accuracy and eliminate harmful transition statuses in

production processes. As a result of fast progress in technology, many complex

operational tasks have been solved by connecting programmable logic controllers and

possibly a central computer. Beside connections with instruments like operating panels,

motors, sensors, switches, valves and such, possibilities for communication among

instruments are so great that they allow high level of exploitation and process

coordination, as well as greater flexibility in realizing a process control system. In

automated system, PLC controller is usually the central part of a process control system.

With execution of a program stored in program memory, PLC continuously monitors

status of the system through signals from input devices. Based on the logic implemented

in the program, PLC determines which actions need to be executed with output

instruments. To run more complex processes it is possible to connect more PLC

controllers to a central computer.

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, control of amusement rides, or control of lighting fixtures. PLCs

are used in many different 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 non-volatile memory. A PLC is an example of a real time

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system since output results must be produced in response to input conditions within a

bounded time, otherwise unintended operation will result.

PLCs were evolved mainly as a replacement to relay logic. In addition to normal

sequential logic, complicated arithmetic calculations are also possible with the latest

architecture.

All PLCs are built around a Central Processing Unit (CPU) having a Processor or a

Micro controller. The processor is of a general purpose like Intel 8085 upto Pentium

versions. Some PLCs use special type of Micro controllers which are specific to the

make and model.

The main difference between a normal desktop Personal Computer (PC) and a PLC is,

PLCs are dedicated to a particular application. Once it is built for a specific purpose, it

cannot be used for any other job unless some changes are done.

The disadvantages of relay logic where no modifications are possible with power are

totally ruled out in a PLC based system. Any changes can be adopted online while the

process is going on and changes occur without any Process interruption.

All PLC systems are user friendly, micro level diagnostic features are available. Once

the user understands the syntax and the application, possibilities of error prone operations

are minimum.

DETAILS OF PARTS IN A PLC SYSTEM

A PLC System consists of the following parts

1. Mother board / base board / Module connectors

These are responsible for parallel communication between all the modules and

the CPU. Some systems support multiple boards where communication bus

will be extended using a parallel cable. All other modules will sit on this to

share the common bus.

2. CPU power supply

This module provides necessary power supplies required for CPU operation.

Basic power supplies are 5 / 3.6V, +/-12V, +/-15V, 24V

3. Interrogation Power supply

This power supply is required for actuating the field devices (relays,

contactors etc…) and acquiring the signal from field sensing instruments

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(Metal detectors, proximity switches etc…). The voltage level varies

depending upon the application. Typical voltages used are, 24V, 48V. 60V,

220VAC etc…

4. Arithmetic Logic Unit (ALU) – Processor

Main processor unit where all logical, arithmetical etc… operations take

place.

5. Memory module

Some PLCs have inbuilt memory inside the Processor itself. If it is required to

expand the capacity of the memory, additional Memory modules are required.

The capacity is limited only depending upon the Processor used.

6. Digital Input / Output modules

Digital Input modules are used to sense the field signals. These convert

interrogation supply to TTL level (5V/3.6V).

Digital Output modules are used to actuate the field devices. These convert

TTL level to interrogation supply.

The total number of I/O handling capacity of a PLC is dependent on the type

of PLC used.

7. Analog Input / Output modules

Analog input modules convert a voltage signal ( 0 to +/-10V) or a current

signal (0 or 4 to 20ma) to digital form and store in a register.

Analog output modules convert digital word to either analog voltage or

current signal

8. Communication modules

These are responsible for communication with Programming Unit (also called

PG unit) to upload/download program, diagnosis purpose etc…

9. Application specific modules

Apart from digital and analog modules, some application needs for a special

modules like, Arithmetic processor, Ethernet module, Counter module etc…

The usage depends on the application.

10. Software for communication / modification / analysis of the system

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Any PLC requires a way to communicate with the PG unit. This is done

through a software provided by the PLC manufacturer and a cable which

connects between PLC and the PG unit.

ARCHITECTURE OF A PLC

The Central Process Unit consists of following functional parts

1. Arithmetic Logic Unit

2. Decoding circuit

3. Timing circuit

4. Registers

5. Interrupt handling

6. Memory management

7. Communication

8. Interfacing units

The input system consists of Digital, Analog and counter units. Output system is

constituted with Digital and Analog output modules. The memory (external) will be

shared with CPU for its internal usage and two way communication exists. In some PLC

systems, there will be hand shaking signals which confirm the healthiness of each

module. In such PLCs, there will be two way communication system exists between ALU

and I/Os. The power supply feeds to I/Os and as well as CPU and related modules at bus

level.

CLASSIFICATION OF PLC SYSTEMS

There are basically three types of PLC systems.

1. Sequential

2. Modular

3. Real time

Sequential PLC systems are those where only one CPU exists with I/O modules. No

special module exists. All operations are carried out by the main CPU only.

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In modular PLC system, special modules are used to carry some critical functions.

They function on their own data and only communicate to main PLC for healthiness and

other purpose. Arithmetic processors, motion controllers are some examples of such

modules. In such PLC systems, various time critical tasks are handled independently by

these special modules reducing the burden on the main Processor.

In Real Time based PLC systems, the total job is divided into several sub tasks.

All tasks are operated on a time division basis, so that, to the user, it looks like all are

being operated simultaneously. Just like a multi tasking operating system (Windows XP

and others), the execution of each task will be faster. Multiple CPU modules and

multiple interrupts are also possible with such systems.

BASICS OF PLC CONFIGURATION

To build a PLC system, one should know about the requirement of Hardware and

Software

In Hardware, following points are to be taken care

1. Number of I/Os

This is the main requirement to build a PLC system. Along with the number

of I/Os (digital and analog), knowledge on operation of the equipment is also

important

2. Memory requirement

There is no proper thumb rule to calculate the memory required for a

particular application. Approximation to be done with past experience.

3. Processor type

This depends upon the criticality of the application. Knowledge about

interrupt handling, DMA handling is required to select the Processor type for

a particular application.

4. Power supply

It is very important to decide the interrogation supply required for any

application. Care should be taken for selecting the load current in designing

the power supply rating.

Coming to software requirement, following point are to be considered

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1. Modes of addressing

Different PLCs provide different way of addressing to Digital/analog I/Os and

also for other special I/Os. Knowledge about the addressing modes provided

by the PLC manufacturer is required

2. Application software

This is the one which is used for developing the application program to run

the job successfully. Different PLC manufacturers provide different software

packages to interact with PLC and to develop application software offline.

Most of the softwares are MS-Windows and DOS based.

3. Diagnostic features

All latest PLC systems provided micro level diagnostic features. User can

know the faults at discrete bit level.

4. Configuration of the system

Many PLC suppliers provide configuration of the PLC through software. This

is useful in modifying and system if required in future when application

demands

ADDRESSING MODES USED IN DIFFERENT PLCs

There are three types of addressing modes available

1. Mother boards

There are two types of Mother boards.

1. Passive

2. Active

Passive mother boards shall have only parallel bus extension. CPU

communicates with all modules through this bus. Each slot shall have unique

bus to identify the module in that particular card.

Active mother boards will have addressing features. The address decoding

part is available in such mother boards

2. Module addressing

Dip switches are provided at each card. These switches are to be set

accordingly to use in any location.

3. Software addressing

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This is the advanced feature the latest PLC system is offering. All addressing

will be automatic and option is available for changing if required. The

moment any module is attached to the system, address will be assigned and

user has to use that part for accessing the module

DETAILS OF PROGRAMMING IN A PLC

Two types of jobs are involved with any PLC system. Offline activities include

preparation of application program and hardware configuration. All communication

configurations are also done offline. In this case, the PLC shall not be in RUN mode. Few

PLC system provide flash ram/ Eeprom etc.. to store the configuration as a back up

permanently which can be overwritten in future. Such operations are also done offline.

Online operations include, forcing of memory bits including I/Os. Other user memory

part like registers can also be altered during online. Minor changes of application

program can be made.

DETAILS OF OPERATION IN A PLC

Basically, there are two modes for any PLC system, Run and stop. In Run mode, PLC

will execute the logic, read the inputs and produce outputs. PLC will take certain amount

of time to read inputs, execute the logic and produce the outputs. This time is called cycle

time of PLC. The execution in a flow diagram can be seen as, Start input scan Logic

scan Output scan User application Communication System scan Timer

operation Stop

DETAILS OF PROGRAMMING LANGUAGES USED IN PLCs

Different software languages are available to program a PLC. Few of these include

Ladder diagram

Statement list

Control system flow

Function block diagram

Few PLC systems allow to program using higher level languages like Visual C,

Visual Basic, C, Pascal etc… Few PLCs can be programmed using Assembler program also.

24

COMMUNICATION SYSTEMS IN PLCs

Different types of communication systems are adopted by different PLC

manufacturers. Following are the list of few such systems.

Siemens:

1. Profibus

2. MPI – Multi point interface

3. OPI – Operator interface

4. Ethernet

GE-Fanuc:

1. RS-232

2. Ethernet

3. Genius Bus

Allen Bradely:

1. Device net

2. Control net

3. Ethernet

DIFFERENT TYPES OF PLCs USED IN VSP

Following are few different type of PLCs which are being used in VSP.

1. Siemens – S7-200, S7-300

2. Allen Bradely – SLC, Control logix, Flex logix

3. GE-Fanuc – Versa max, 90-30

4. Telemecanique – Series TSX

5. AEG – Quantum, CP80-A800

6. Honey well – Series 620

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MAN MACHINE INTERFACE

Earlier days, all commands from operator desk (Control Pulpit) are wired to

automation systems (PLCs and other equipments) through push buttons, data key boards

and other physically mounted devices. That made to increase the wiring more and

cumbersome to maintain. The present automation system involves Man Machine

Interface (MMI) or Human Machine Interface (HMI) or Man Machine Communication

(MMC) systems. The total wiring got reduced and the communication between operator

and the automation system is through Ethernet(OFC or UTP), or proprietary

communication bus.

The latest MMI systems are built on Server and client based architecture. MMI few

systems which are being used in VSP are shown below

1. RS View For Allen Bradely systems

2. Win CC For Siemens systems

3. Complicity for GE-Fanuc systems

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DETAILS OF GE-FANUC PLC

The basic parts in the PLC are

- Base plate

- Power supplies

- CPU’

- Digital I/O Modules

BASE PLATES:

The base plates are the foundation of PLC system because most other components

mount on them. As a basic minimum , every system has at least one base plate which

usually contains the CPU (in which case ,it is referred to as “the CPU base plate”).Many

systems require more modules than can be mounted on one base plate ,so there are also

Expansion and Remote base plate that connect together.

27

The different categories of base plate are:

CPU

Expansion

Remote

Each of these is available in two sizes, 5-slot and 10-slot, named according to the number

of modules they can hold.

DIGITAL I/O MODULES:

24 VDC Positive/Negative Logic, 32 Point Input IC693MDL655:

The 24 volt DC Positive/Negative Logic Input module for the Series 90-30

Programmable Logic Controller provides 32 discrete input points. The inputs are

arranged in four isolated groups of eight (A1 - A8, B1 - B8, C1 - C8, and D1 - D8).The

inputs are positive or negative logic inputs and will operate at levels up to 30V.Backplane

isolation between the field side and logic side is provided by up to-couplers on the

module. Isolation is also provided between the four groups of inputs on the module,

however each group of eight inputs is referenced to the same user common connection.

There are no special faults or alarm diagnostics reported. LED indicators (labeled A1-

A8, B1 - B8, C1 - C8, D1 - D8) at the top of the module provide the ON/OFF status of

each input point. This module is configured as a 32-point input type and uses 32 bits of

discrete %I input data. Current into an input point results in a logic 1 in the input status

table. Power to operate field devices can be supplied by the user, or from the isolated +24

VDC supply available at the module’s I/O connectors. This module can be installed in

any I/O slot of a 5 or 10-slot base plate in a Series 90-30 PLC system. Connections to the

input circuits are made from the user’s input devices to two male (pin-type) 24-pin

connectors (Fujitsu FCN-365P024-AU) mounted on the front of the module.

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Circuit diagram of input module:

29

POWER SUPPLY MODULES:

Every base plate whether a CPU ,Expansion ,Remote base plate and whether a 5 –

slot or a 10 – slot size , must have its own power supply. The power supply always mount

in a base plate’s left most slot. There are several power supply modules available to meet variety of requirements.

SPECIFICATIONS OF GE-FANUC PLC:

PARAMETERS

RANGE

Rated Voltage

24 volts DC, Positive or Negative Logic

Input Voltage Range

0 to 30 volts DC

Inputs per Module

32 (four groups of eight inputs each)

Isolation

1500 volts between field side and logic side

250 volts between groups

Input Current

7.0 mA (typical ON current @ 24 VDC)

On-state Voltage

11.5 to 30 volts DC

Off-state Voltage

0 to 5 volts DC

On-state Current

3.2 mA (minimum)

Off-state Current

1.1 mA (maximum)

30

On response Time

2 ms maximum

Off response Time

2 ms maximum

Internal Power Consumption

195 mA (maximum) from +5V bus on

backplane ; (29 mA +0.5 mA/point ON +4.7

mA/LED ON)

224 mA (typical) from isolated +24V bus on

backplane or from user input supply @ 24

VDC

and all 32 inputs ON)

Figure12, Block diagram of PLC programming

Two types of jobs are involved with any PLC system. Offline activities include

preparation of application program and hardware configuration. All communication

configurations are also done offline. In this case, the PLC shall not be in RUN mode. Few

PLC system provide flash ram/ EPROM etc. to store the configuration as a back up

permanently which can be overwritten in future. Such operations are also done offline.

ONLINE OFF LINE

LOGIC

FORCING

USER MEMORY

HARDWARE

FLASH STORAGE

COMMUNICATION SETUP

SETUP

31

Online operations include, forcing of memory bits including I/Os. Other user memory

part like registers can also be altered during online. Minor changes of application

program can be made.

DETAILS OF OPERATION IN A PLC

Basically, there are two modes for any PLC system, Run and stop. In Run mode, PLC

will execute the logic, read the inputs and produce outputs. PLC will take certain amount

of time to read inputs, execute the logic and produce the outputs. This time is called cycle

time of PLC.

The execution steps to interface PLC with PC:

STEP-1:

Selection of VERSAPRO software

VERSAPRO is programming software developed with GE-Fanuc PLC.

STEP-2:

Create a new folder

HARDWARE CONFIGURATION:

Hardware configuration consists of configuring power supply, CPU ,Input-output

modules with required specifications.

STEP-3:

3.1 Go to VIEW → HARDWARE CONFIGURATION.

3.2 Go to EDIT → MODULE OPERATION → REPLACE MODULE

The above step is used to configure CPU and Power supply as required

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I/O MODULES

3.3 Go to EDIT→ MODULE OPERATION → ADD MODULE

This step is used for including I/O modules if required.

COMMUNICATION SET-UP :

STEP–4:

4.1 Go to TOOLS → COMMUNICATION SET UP

4.2 Specify the device model and port type

If the communication is through ETHERNET then IP Address is also required.

STEP-5:

Draw the ladder diagram by selecting the components required and name the

components

STEP-6:

Now connect PLC

Go to PLC → CONNECT

STEP-7:

RUN the program and STOP by enabling outputs.

STEP-8:

STORE the program to PLC.

If any errors, information window will appear indicating the errors.

NOTE:

Verify whether the logic equals or not.

STEP-9:

5

6

7

8

9

1

0

4

3

1

2

Power CPU

supply

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Force the inputs depending upon the logic

9.1 Select the component → OVERRIDE and TOGGLE the input.

STEP-10:

Load the program from PLC while PLC is in running mode.

Information window will appear showing the load status.

HOW PLC CONTROLLER WORKS:

Basis of a PLC function is continual scanning of a program. Under scanning we mean

running through all conditions within a guaranteed period. Scanning process has three

basic steps:

Step1.

Testing input status.

First, a PLC checks each of the inputs with intention to see which one of them has status

ON or OFF. In other words, it checks whether a sensor or a switch etc. connected with an

input is activated or not. Information that processor thus obtains through this step is

stored in memory in order to be used in the following step.

Step2.

Program execution.

Here a PLC executes a program, instruction by instruction. Based on a program and

based on the status of that input as obtained in the preceding step, an appropriate action is

taken. This reaction can be defined as activation of a certain output, or results can be put

off and stored in memory to be retrieved later in the following step.

Step3.

Checkup and correction of output status

Finally, a PLC checks up output status and adjusts it as needed. Change is performed

based on the input status that had been read during the first step, and based on the results

of program execution in step two. Following the execution of step 3 PLC returns to the

beginning of this cycle and continually repeats these steps. Scanning time is defined by

the time needed to perform these three steps, and sometimes it is an important program

feature.

34

35

DETAILS OF PROGRAMMING LANGUAGES USED IN PLCs

Different software languages are available to program a PLC. Few of these include

1. Ladder diagram

2. Statement list

3. Control system flow

4. Function block diagram

Few PLC systems allow to program using higher level languages like Visual C, Visual

Basic, C, Pascal etc Few PLCs can be programmed using Assembler program also.

36

CONCLUSIONS

In VSP, LMMM produces Rounds, Rebars, channels, angles etc…. For this

process various electronic equipment are required which include machines. To

control these machines PLCs are used which are a part of automation process. PLC

accepts inputs from switches and sensors, evaluates these in accordance with a stored

program, and generates outputs to control machines and processes.

There are many makes of PLCs available for industrial usage. Among them

GE - PLCs are widely used.

In this project we studied how to control the machines used in wire rod mill

using GE – Fanuc PLCs (90 – 30 model). In this PLC, for the purpose of

communication between programmable controllers ,distributed i/o stations, HMI

devices and numerous other field devices we use Genius bus. There are many types

of . These GE – Fanuc PLCs have very useful expansion facilities like

comprehensive communication, networking possibilities and user friendly handling.

It has essential features like modularity, multi computing, engineering and diagnostis.

These are playing a vital role. They are very reliable in their performance like

accuracy, speed and adaptability.

These PLCs can be expanded with latest versions i.e., state of art technology

to improve memory capability, I/O handling capability and versatility.

HMI communication is done through Cimplicity networking for various

automation units like servers, clients, display boards etc… Standard Ethernet network is used for communication as it is an open system.