seminar report for Electronics & Instrumentation deapartment

1. A
TRANING REPORT
ON
PROGRAMMABLE LOGIC CONTROLLERS
At
GAIL (INDIA) LIMITED, NASIRABAD
BY
RITU SHARMA
SESSION 2015-2016
DEPARTMENT OF ELECTRONICS INSTRUMENTATION
AND CONTROL ENGINEERING
GOVT. ENGINEERING COLLEGE, AJMER
(Run under the Society Act)
Barliya Chouraha, NH- 8, Ajmer
www.ecajmer.ac.in, Telefax: 0145-2671800, 2671801

2. CERTIFICATE

3. ABSTRACT
As electronics play a vital role in the Industrial growth. Instrumentation is also
backbone of any Process system. Now days technology is finding wide use in industries as it
avoids the need of extra man work like in automation.
Engineering is not only a theoretical study, but it is implementation of all we study for
creating something new and making things more easy and useful practical study. In the
college circulation we usually get the theoretical knowledge of industries, and a little bit of
implementation knowledge that how is it work? But how can we prove our theoretical
knowledge to increase the productivity or efficiency of the industry.
To overcome such problem we the student of Engineering Colleges are supposed to
go on the Practical Training of 45 days in our summer vacations as the time is predefined to
be familiar with industrial environment. I have taken my Practical Training at “GAIL INDIA
LIMITED NASIRABAD”.
Last I can say that it was a great experience to work under such experienced
Engineers and Staff members. I gained a lot of knowledge and truly felt the industrial
environment during my training. Really without this practical training, only theoretical
engineering nothing.

4. ACKNOWLEDGEMENT
With deep sense of gratitude, I would like to thank GAIL (INDIA) LTD for allowing
me to attend vocational training at its LPG pumping station, Nasirabad. I express sincere
thanks to Mr. S.K. Tiku, Chief Manager, Nasirabad GAIL for providing the valuable support
during the entire training period.
I am very thankful to Mr. Rohit Sharma, Sr. Manager & Mr. S.K. Jain, Sr. Manager
for enriching my knowledge by his valuable suggestions, ideas & technical skills. He
provided me full support from technical side in my training period which will be beneficial to
me in my next semester or in future my career also. My special thanks to all entire team of
GAIL (INDIA) LIMITED Nasirabad GAIL for making my training successful.
I would also like to thank to Mr. J.K. Deegwal (Head of Department, Electronic
Instrumentation & Control engineering), Mr. H.S. Mewara (Associate Professor), Mr.
C.P. Jain (Assistant Professor) and faculty members of the department, who often helped
and gave me valuable guidance to prepare my report.
Last but not the least, I would like to thank my colleagues who helped me a lot in
gathering different information, collecting data and guiding me from time to time in making
this project despite of their busy schedules, they gave me different ideas in making this project
unique.
RITU SHARMA
(12EEAEI047 )

5. CONTENTS
CHAPTER NO. TITLE PAGE NO.
CERTIFICATE i
ABSTRACT ii
ACKNOWLEDGEMENT iii
CONTENTS iv
FIGURE INDEX vi
TABLE INDEX viii
CHAPTER 1 GAIL(INDIA) LTD 1
1.1 INTRODUCTION 1
1.2 O & M BASE NASIRABAD PROCESS 1
1.2.1 SALIENT FEATURES OF IPS 2
1.2.2 ACTIVITIES INVOLVED AT IPS
NASIRABAD
2
1.2.3 CHARACTERISTICS OF GAIL LPG 3
CHAPTER 2 FIRE AND SAFETY 4
2.1 DEFINATION OF FIRE 4
2.2 TYPES OF FIRE 4
2.3 FIRE TRIANGLE 5
2.4 FIRE TETRAHEDRON 5
2.5 SAFETY MEASURES 6
CHAPTER 3 PRESSURE TRANSMITTER 8
3.1 INTRODUCTION 8
3.2 PRESSURE SWITCHES CALIBRATION 9
3.3 DEAD WEIGHT TESTER 9
CHAPTER 4 VALVES 11
4.1 TYPES OF VALVE 11
4.2 GLOBE VALVE 12
4.4 SOLENOID VALVE 13

6. 4.5 BALL VALVE 14
CHAPTER 5 TEMPERATURE SENSORS 15
5.1 INTRODUCTION 15
5.2 THERMOCOUPLE 15
5.2.1 THERMOCOUPLE OPERATION 16
5.3 RTD 17
5.3.1 CONSTRUCTION 18
5.3.2 WIRING CONFIGURATIONS 18
5.3.2.1 TWO WIRE CONFIGURATION 18
5.3.2.2 THREE WIRE CONFIGURATION 19
5.3.2.3 FOUR WIRE CONFIGURATION 19
5.3.3 ADVANTAGES & LIMITATIONS 20
CHAPTER 6 PIPING & INSTRUMENTATION DIAGRAMS 21
6.1 P&ID DIAGRAMS 21
CHAPTER 7 PROGRAMMABLE LOGIC COTROLLERS 24
7.1 INTRODUCTION 24
7.2 WHAT DO THE INDIVIDUAL WORDS MEAN 24
7.3 HISTORY OF PLCS 25
7.4 PLC OVERVIEW 26
7.4.1 THE POWER SUPPLY AND RACK 26
7.4.2 THE CENTRAL PROCESSING UNIT (CPU) 27
7.4.3 THE INPUT/OUTPUT (I/O) SECTION 27
7.5 PROGRAM SCAN 28
7.6 PLC HARDWARE 29
7.7 PLC ARCHITECTURE AT GAIL(INDIA) LTD 29
CONCLUSION 30
BIBLIOGRAPHY 31

7. FIGURE INDEX
FIGURE NO. FIGURE TITLE PAGE
NO.
Figure 1.1 JLPL Schematic 3
Figure 2.1 Fire Triangle 5
Figure 2.2 Fire Tetrahedron 5
Figure 2.3 Safety Helmet & Goggles 6
Figure 3.1 Pressure Transmitter 8
Figure 3.2 Dead Weight Testers 9
Figure 4.1 Globe Valve 11
Figure 4.2 Butterfly Valve 12
Figure 4.3 Solenoid Valve 13
Figure 4.4 Ball Valve 14
Figure 5.1 Thermocouples 15
Figure 5.2 Circuit diagram of Thermocouples 16
Figure 5.3 Resistance Temperature Detectors 17
Figure 5.4 Construction 18
Figure 5.5 Two Wire Configuration 18
Figure 5.6 Three Wire Configuration 19
Figure 5.7 Four Wire Configuration 19
Figure 6.1 PID Symbols 22
Figure 6.2 P&ID signals representation 23
Figure 7.1 Relays replaced by PLCs 25

8. FIGURE NO. FIGURE TITLE PAGE
NO.
Figure 7.2 PLC Overview 26
Figure 7.3 PLC Program Scan 28
Figure 7.4 PLC Hardware 29

9. TABLE INDEX
TABLE NO. TITLE OF TABLE PAGE
NO.
Table 2.1 Types of Fire 4
Table 2.2 Types of Fire Extinguishers 7
Table 7.1 Input & Output Sections of PLC 27

10. Chapter– 1
GAIL (INDIA) LTD
1.1 INTRODUCTION:
GAIL (India) Limited is the largest state-owned natural gas processing and distribution
company in India. It has following business segments: Natural Gas, Liquid
Hydrocarbon, Liquefied petroleum gas Transmission, Petrochemical, City Gas Distribution,
Exploration and Production, GAILTEL and Electricity Generation. GAIL has been conferred
with the MAHARATNA Status on 1 Feb 2013, by the Government of India. Net financial
turnover for the year 2014-2015 was Rupees 56569 Crores and profit is Rupees 5620 Crores.
Originally this 1800 Km long pipeline was built at a cost of Rs 1700 Crores and it laid the
foundation for development of market for natural Gas in India.
Liquefied petroleum gas (LPG) is the most widely used domestic and commercial fuel in
India. Around 90 per cent of the LPG is consumed in India as fuel by the household sector,
while the balance is sold to industrial and commercial customers. GAIL has seven LPG Plants,
two at Vijaipur and one at Vaghodia, and one each in Lakwa (Assam), Auraiya (UP), Gandhar
(Gujarat) and Usar (Maharashtra). LPG is sold in bulk to LPG retailing companies such IOCL,
BPCL, HPCL and other liquid hydrocarbon products are sold to industries.
GAIL is rated among the top 30 Indian companies in terms of profits and revenue.
1.2 GAIL(INDIA) LTD, O & M BASE, NASIRABAD PROCESS:
GAIL (India) Limited Nasirabad is Intermediate Pumping Station (IPS) of JLPL (Jamnagar to
Loni Pipeline) a TUV certified company. The main function of this station is: Transportation
& Supply of LPG through JLPL as per Transport Supply Agreement. This station provides
Supply of LPG to the customers (IOCL, BPCL and HPCL) at Nasirabad IPS.Various
functions of Nasirabad IPS are Reception of LPG from GAIL, Abu road. Metering and
supply of LPG to local customers at Ajmer. Pumping of LPG to Nasirabad downstream
customers. GAIL’s Jamnagar-Loni LPG Pipeline System having the capacity to receive,
transport and deliver LPG under controlled conditions to its Customers.

11. Pipeline has been laid with the prime objective of transporting in a totally safe &
uninterrupted manner LPG from Jamnagar & Kandla dispatch terminal to three OIL
companies located at Ajmer, Jaipur, Gurgaon, Piyala, Madanpur-Khadar and Loni. The
pipeline has two dispatch terminals, one at Jamnagar [These are Essar Oil Ltd (EOL) &
Reliance Industries Limited (RIL)] and other at Kandla (IOCL). The length of Abu road to
Ajmer pipeline is 263 km approximately.
The objectives of Gail Nasirabad are to boost up the pressure that drops in the pipeline
and for efficient transportation of LPG to its customers in Ajmer, i.e. IOCL, HPCL, BPCL.
The JLPL pipeline is very long (1250 km) so there are chances of pressure drop in between.
To prevent this drop there are various SVs and IPS present for raising the pressure (boosting)
and transporting the LPG efficiently. IPS are provided at following places SAMAKHIALI,
ABU ROAD, NASIRABAD and MANSARAMPURA.
1.2.1 Salient Features of IPS Nasirabad:
The upstream of Nasirabad IPS from TOT-1, an 8” spur line of length 11 km goes to RT-
Ajmer (IOCL) to deliver LPG to IOCL. From IPS Nasirabad an 8” spur line of length 0 1 km
goes to HPCL and from IPS Nasirabad, an 8” spur line of length 2.2 km goes to BPCL.
Throughput of 2.2 MMTPA LPG received from Abu Road at pressure 16– 25 Kg/cm2 is
pumped by Booster Pumps of Nasirabad IPS at 40- 85 Kg/cm2 through 12” pipeline up to
IPS - Mansarampura located at 866 Km.
1.2.2 Activities Involved At IPS Nasirabad:
There are various activities been done at the IPS Nasirabad. Mainly the activities performed
are to pump LPG into P/L by three methods which are variable speed, drive electric motor-
mainline pumps, LPG flow measurement for the leak detection purpose, monitoring of
pipeline, intermediate pigging station & SV stations in their jurisdiction.
There are some actions performed on the LPG itself like filtering of LPG with the help of
basket filters, pig launching & receiving through the pipeline in order to clean the path of
LPG transportation. Whenever there is GRID power failure in the process operation, Diesel-
Engine-generator (DEG) is also undertaken here. Diesel transfer from road tanker to terminal
storage and operation of the fire water pumps in case of emergency.

12. 1.2.3 Characteristics of GAIL LPG:
LPG is processed from natural gas at the Kandla, Jamnagar ports. It has a high vapour
pressure after being refined. It vaporizes at atmospheric temperature and pressure. Its
homogeneous composition results in more efficient combustion. The air fuel ratio need not be
changed with every batch. No Impurities like sulphur, carbon dioxide, traces of oxides of
nitrogen are present in it hence lower corrosion. It has nil moisture content and has a higher
calorific value than refinery's LPG and hence gives more value for money. Chemical formula
of LPG is mix of mainly C4H10 & C3H10.Vapour density of the LPG (wrt air=1) is 1.8.It is an
odourless and colourless gas with its compressed liquid as its physical state.
Figure 1.1- JLPL Schematic

13. Chapter 2
FIRE AND SAFETY
2.1 DEFINITION OF FIRE:
Fire is the rapid oxidation of a material in the exothermic chemical process of combustion,
releasing heat, light, and various reaction products.
2.2 TYPES OF FIRES:
Class A: Class A fires are fires in ordinary
combustibles such as wood, paper, cloth, trash, and
plastics.
Class B: Class B fires are fires in flammable liquids such
as gasoline, petroleum oil and paint. Class B fires also
include flammable gases such as propane and butane.
Class C: Class C fires are fires involving energized
electrical equipment such as motors, transformers, and
appliances. Remove the power and the Class C fire becomes
one of the other classes of fire.
Class D: Class D fires are fires in combustible metals such
as potassium, sodium, aluminum, and magnesium.
Table 2.1: Types of Fire

14. 2.3 FIRE TRIANGLE:
The fire triangle or combustion triangle is a simple model for understanding the necessary
ingredients for most fires. The triangle illustrates the three elements a fire needs to ignite:
heat, fuel, and an oxidizing agent (usually oxygen).The three elements are the basic
requirement for the fire to occur.
Figure 2.1- Fire Triangle
2.4 FIRE TETRAHEDRON:
The fire tetrahedron represents the addition of a component, the chemical chain reaction, to
the three already present in the fire triangle. Once a fire has started, the resulting exothermic
chain reaction sustains the fire and allows it to continue until or unless at least one of the
elements of the fire is blocked.
Figure 2.2-Fire Tetrahedron

15. 2.5 SAFETY MEASURES:
Various types of safety measures and devices are being used to control the fire hazard. Some
of them are fire extinguishers, safety goggles, helmet, safety gloves and many more. We
should always wear a helmet during excavation, backfilling and other site works. We always
have proper kit before working, check your safety tools and you should proper knowledge of
using safety kit and always have a first aid box with you while going in the field.
Figure 2.3 Safety Helmet and Goggles
Fire can be extinguished if any one of the three components necessary for an outbreak
of fire to occur is removed. Three basic methods are employed:
1. COOLING: - Removal of HEAT.
2. STARVING: - Removal of FUEL.
3. SMOTHERING: Removal or limitation of OXYGEN.
A fire extinguisher, or extinguisher, is an active fire protection device used to extinguish
or control small fires, often in emergency situations. E.g. foam extinguisher, CO2
extinguisher, and Dry chemical powder extinguisher. A near miss is an unplanned event that
did not result in injury, illness, or damage – but had the potential to do so.
ACCIDENT: An accident or a mishap is an unforeseen and unplanned event or circumstance
that causes injury. CAUSES: Unsafe act, unsafe condition, and Natural calamity.

16. 2.6 TYPES OF FIRE EXTINGUISHERS:
Water and Foam: Water and Foam fire extinguishers
extinguish the fire by taking away the heat element of
the fire triangle. Foam agents also separate
the oxygen element from the other elements. Water
extinguishers are for Class A fires only - they should not
be used on Class B or C fires. The discharge stream
could spread the flammable liquid in a Class B fire or
could create a shock hazard on a Class C fire.
Carbon Dioxide: Carbon Dioxide fire extinguishers
extinguish fire by taking away the oxygen element of the
fire triangle and also by removing the heat with a very cold
discharge. Carbon dioxide can be used on Class B & C
fires. They are usually ineffective on Class A fires.
Dry Chemical: Dry Chemical fire extinguishers
extinguish the fire primarily by interrupting the chemical
reaction of the fire triangle. Today's most widely used type
of fire extinguisher is the multipurpose dry chemical that is
effective on Class A, B, and C fires. This agent also works
by creating a barrier between the oxygen element and
the fuel element on Class A fires. Ordinary dry chemical is
for Class B & C fires only. It is important to use the correct
extinguisher for the type of fuel! Using the incorrect agent
can allow the fire to re-ignite after apparently being
extinguished successfully.
Table 2.2: Types of Fire Extinguishers

17. Chapter –3
PRESSURE TRANSMITTER
3.1 INTRODUCTION:
A pressure transmitter measures pressure, typically of gases or liquids. Pressure is an
expression of the force required to stop a fluid from expanding, and is usually stated in terms
of force per unit area. A pressure sensor usually acts as a transducer; it generates a signal as
a function of the pressure imposed. For the purposes of this article, such a signal is electrical.
Figure 3.1- Pressure Transmitter
Pressure sensors are used for control and monitoring in thousands of everyday applications.
Pressure sensors can also be used to indirectly measure other variables such as fluid/gas flow,
speed, Water level and altitude. Pressure sensors can alternatively be called pressure
transducers.
3.2 PRESSURE SWITCHES CALIBRATION:
Pressure switches are devices that are configured to sense a change in pressure and respond in
a specified manner. The pressure switch is utilized in many different environments, including
manufacturing machinery and facilities, utility plants, and public buildings. In some designs,
the pressure switch monitors and automatically responds to conditions, while other examples
of the pressure switch require manual intervention.

18. 3.2.1 CALIBRATION:
Pressure gauges are either direct- or indirect-reading. Hydrostatic and elastic gauges measure
pressure is directly influenced by force exerted on the surface by incident particle flux, and
are called direct reading gauges. Thermal and ionization gauges read pressure indirectly by
measuring a gas property those changes in a predictable manner with gas density. Indirect
measurements are susceptible to more errors than direct measurements.
3.3 DEAD WEIGHT TESTER:
Dead Weight Testers are used as primary standards in Industry, laboratories and academia
worldwide for precise Measurement of pressure. All pressure measuring instruments whether
pressure gauges, Transmitters, transfer standards, switches, recorders, Pressure data loggers,
digital calibrators etc are ultimately calibrated using dead weight testers. Till date no other
Equipment has been able to beat dead weight testers long Time stability, accuracy &
repeatability.
Figure 3.2 Dead Weight Testers
In rare cases like hydro testing, dead weight testers are used to directly measure
system pressures because the Measurement precision required is very high. Dead Weight
Tester uses the piston gauge pressure balance System consisting of finely lapped piston
cylinder assembly of Known area mounted along the vertical axis. Pressure forces the piston

19. upwards and that force is balanced using accurately Calibrated masses. Convenient value of
piston area and Masses allow user friendly measurement of pressure.
Operating Principle:
Fluid Pressure generated by a screw pump acts on the bottom of a vertically free
floating piston. The force produced pushes the loaded free piston vertically upwards. The
piston floats freely in its cylinder and the pressure in the circuit will be determined by the
weights loaded on the piston divided by the effective area of the piston with corrections for
value of acceleration due to gravity, air buoyancy, and surface tension and datum level
difference.

20. Chapter –4
VALVES
4.1 TYPES OF VALVE:
Although many different types of valves are used to control the flow of fluids, the basic valve
types can be divided into two general groups: stop valves and check valves. Besides the basic
types of valves, many special valves, which cannot really be classified as either stop valves or
check valves, are found in the engineering spaces. Many of these valves serve to control the
pressure of fluids and are known as pressure-control valves. The following sections deal first
with the basic types of stop valves and check valves, then with some of the more complicated
special valves.
4.2 GLOBE VALVES:
Globe is globular appearing bodies. Globe valve inlet and outlet openings are arranged in
several ways to suit varying Requirements of flow. The above figure shows the common
types of globe valve bodies: straight flow, angle-flow, and cross flow.
Figure 4.1 Globe Valve
Globe valves are used extensively throughout the engineering plant and other parts of
the ship in a variety of systems.

21. 4.3. BUTTERFLY VAVLE:
Quick-acting, provides positive shut-off, and can be used for throttling. The butterfly valve
has a body, a resilient seat, a butterfly disk, a stem, packing, a notched positioning plate, and
a handle. The resilient seat is under compression when it is mounted in the valve body, thus
making a seal around the periphery of the disk and both upper and lower points where the
stem passes through the seat. Packing is provided to form a positive seal around the stem for
added protection in case the seal formed by the seat should become damaged. To close or
open a butterfly valve, turn the handle only one quarter turn to rotate the disk 90°. Some
larger butterfly valves may have a hand wheel that operates through a gearing arrangement to
operate the valve.
Figure 4.2 Butterfly Valve
This method is used especially where space limitation prevents use of a long handle.
Butterfly valves are relatively easy to maintain. The resilient seat is held in place by
mechanical means, and neither bonding nor cementing is necessary, because the seat is
replaceable, the valve seat does not require lapping, grinding, or machine work.

22. 4.4 SOLENOID VALVE:
A solenoid valve is an electromechanical valve for use with liquid or gas. The valve is
controlled by an electric current through a solenoid: in the case of a two-port valve the flow is
switched on or off; in the case of a three-port valve, the outflow is switched between the two
outlet ports. Multiple solenoid valves can be placed together on a manifold. Solenoid valves
are the most frequently used control elements in fluidics. Their tasks are to shut off, release,
dose, distribute or mix fluids. They are found in many application areas. Solenoids offer fast
and safe switching, high reliability, long service life, good medium compatibility of the
materials used, low control power and compact design.
Figure 4.3 Solenoid Valve
A solenoid valve has two main parts: the solenoid and the valve. The solenoid
converts electrical energy into mechanical energy which, in turn, opens or closes the valve
mechanically. Solenoid valves may use metal seals or rubber seals, and may also have
electrical interfaces to allow for easy control. A spring may be used to hold the valve opened
or closed while the valve is not activated.

23. 4.5. BALL VALVES:
Ball valves, as the name implies, are stop valves that use a ball to stop or start the flow of
fluid. The ball performs the same function as the disk in the globe valve. When the valve
handle is operated to open the valve, the ball rotates to a point where the hole through the ball
is in line with the valve body inlet and outlet. When the valve is shut, which requires only a
90-degree rotation of the hand wheel for most valves, the ball is rotated so typical seawater
ball valve.
Figure 4.4 Ball Valve
The hole is perpendicular to the flow openings of the valve body, and flow is stopped.
Most ball valves are of the quick-acting type (requiring only a 90-degree turn to operate the
valve either completely open or closed), but many are planetary gear operated. This type of
gearing allows the use of a relatively small hand wheel and operating force to operate a fairly
large valve. The gearing does, however, increase the operating time for the valve. Some ball
valves contain a swing check located within the ball to give the valve a check valve feature.
Ball valves are normally found in the following systems aboard ship: seawater, sanitary, trim
and drain, air, hydraulic, and oil transfer.

24. Chapter – 5
TEMPERATURE SENSORS
5.1 INTRODUCTION:
Temperature is one of the most important variables to monitor in a Generation, Transmission,
or Distribution system. Peak demands typically occur at ambient temperature extremes so
monitoring local substation temperature can provide data to help predict demand. Electrical
and electronic equipment can malfunction at extreme temperatures. A devise which sense the
temperature called temperature sensors. A device in an automatic temperature-control system
that converts the temperature into some other quantity such as mechanical movement,
pressure, or electric voltage; this signal is processed in a controller, and is applied to an
actuator which controls the heat of the system.
5.2 THERMOCOUPLE:
A thermocouple is a device consisting of two different conductors (usually metal alloys) that
produce a voltage proportional to a temperature difference between either ends of the pair of
conductors. Thermocouples are a widely used type of temperature sensor for measurement
and control and can also be used to convert a heat gradient into electricity. They are
inexpensive, interchangeable, are supplied with standard connectors, and can measure a wide
range of temperatures.
Figure 5.1 Thermocouples
Thermocouples are self-powered and require no external form of excitation. The main
limitation with thermocouples is accuracy and system errors of less than one
degree Celsius (C) can be difficult to achieve.

25. Any junction of dissimilar metals will produce an electric potential related to temperature.
Thermocouples for practical measurement of temperature are junctions of
specific alloys which have a predictable and repeatable relationship between temperature and
voltage. Different alloys are used for different temperature ranges. Properties such as
resistance to corrosion may also be important when choosing a type of thermocouple. Where
the measurement point is far from the measuring instrument, the intermediate connection can
be made by extension wires which are less costly than the materials used to make the sensor.
5.2.1 THERMOCOUPLE OPERATION:
Thermocouples will cause an electric current to flow in the attached circuit when
subjected to changes in temperature. The amount of current that will be produced is
dependent on the temperature difference between the measurement and reference junction;
the characteristics of the two metals used; and the characteristics of the attached circuit
heating the measuring of the thermocouple produces a voltage which is greater than the
voltage across the reference junction.
Figure 5.2 Circuit diagram of Thermocouple
The difference between the two voltages is proportional to the difference temperature and
can be measured on the voltmeter (in millivolts). For ease of operator use, some voltmeters
are set up to read out directly in temperature through use of electronic circuitry.

26. 5.3 RESISTANCE TEMPERATURE DETECTORS (RTDs):
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). They are slowly
replacing the use of thermocouples in many industrial applications below 600 °C, due to
higher accuracy and repeatability. 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 See beck 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 are usually made using platinum, because of its linear
resistance-temperature relationship and its chemical inertness. The platinum detecting wire
needs to be kept free of contamination to remain stable
Figure 5.3 Resistance Temperature Detectors
Commercial platinum grades are produced which exhibit a temperature coefficient of
resistance 0.00385/°C (0.385%/°C) (European Fundamental Interval) The sensor is usually
made to have a resistance of 100 Ω at 0 °C. Measurement of resistance requires a
small current to be passed through the device under test. This can cause resistive heating,
causing significant loss of accuracy if manufacturers' limits are not respected, or the design
does not properly consider the heat path. Mechanical strain on the resistance thermometer can
also cause inaccuracy. Lead wire resistance can also be a factor; adopting three- and four-

27. wire, instead of two-wire, connections can eliminate connection lead resistance effects from
measurements. Three-wire connection is sufficient for most purposes and almost universal
industrial practice. Four-wire connections are used for the most precise applications.
5.3.1 CONSTRUCTION:
These elements nearly always require insulated leads attached. At temperatures below about
250 °C PVC, silicon rubber or PTFE insulators are used. Above this, glass fiber or ceramic
are used.
Figure 5.4 Construction
The measuring point, and usually most of the leads, requires a housing or protective
sleeve, often made of a metal alloy which is chemically inert to the process being monitored.
Selecting and designing protection sheaths can require more care than the actual sensor, as
the sheath must withstand chemical or physical attack and provide convenient attachment
points.
5.3.2 WIRING CONFIGURATIONS:
5.3.2.1. TWO WIRE CONFIGURATION:
Figure 5.5 Two Wire Configuration

28. The simplest resistance thermometer configuration uses two wires. It is only used when high
accuracy is not required, as the resistance of the connecting wires is added to that of the
sensor, leading to errors of measurement. This configuration allows use of 100 meters of
cable. This applies equally to balanced bridge and fixed bridge system.
5.3.2.2. THREE WIRE CONFIGURATION:
Figure 5.6 Three Wire Configuration
In order to minimize the effects of the lead resistances, a three-wire configuration can be
used. Using this method the two leads to the sensor are on adjoining arms. There is a lead
resistance in each arm of the bridge so that the resistance is cancelled out, so long as the two
lead resistances are accurately the same. This configuration allows up to 600 meters of cable.
5.3.2.3. FOUR WIRE CONFIGURATION:
Figure 5.7 Four Wire Configuration
The four-wire resistance thermometer configuration increases the accuracy and reliability of
the resistance being measured: the resistance error due to lead wire resistance is zero.

29. In the diagram above a standard two-terminal RTD is used with another pair of wires to form
an additional loop that cancels out the lead resistance. The above Wheatstone bridge method
uses a little more copper wire and is not a perfect solution. Below is a better
configuration, four-wire Kelvin connection. It provides full cancellation of spurious effects;
cable resistance of up to 15 Ω can be handled.
5.3.3. ADVANTAGES & LIMITATIONS:
A) Advantages of platinum resistance thermometers:
1) High accuracy
2) Low drift
3) Wide operating range
4) Suitable for precision applications.
B) Limitations
1) RTDs in industrial applications are rarely used above 660 °C. At temperatures above
660 °C it becomes increasingly difficult to prevent the platinum from becoming contaminated
by impurities from the metal sheath of the thermometer. This is why laboratory standard
thermometers replace the metal sheath with a glass construction. At very low temperatures,
say below -270 °C (or 3 K), due to the fact that there are very few phonons; the resistance of
an RTD is mainly determined by impurities and boundary scattering and thus basically
independent of temperature. As a result, the sensitivity of the RTD is essentially zero and
therefore not useful.
2) Compared to thermistors, platinum RTDs are less sensitive to small temperature changes
and have a slower response time. However, thermistors have a smaller temperature range and
stability.

30. Chapter –6
PIPING AND INSTRUMENTATION DIAGRAMS
6.1 P & I DIAGRAMS:
P&ID shows all of piping including the physical sequence of branches, reducers, valves,
equipment, instrumentation and control interlocks. The P&ID are used to operate the process
system. A P&ID should include:
1) Instrumentation and designations.
2) Mechanical equipment with names and numbers.
3) All valves and their identifications.
4) Process piping, sizes and identification.
5) Miscellaneous - vents, drains, special fittings, sampling lines, reducers, increasers and
swaggers.
6) Permanent start-up and flush lines.
7) Flow directions.
8) Interconnections references.
9) Control inputs and outputs, interlocks.
10) Interfaces for class changes.
11) Seismic category.
12) Annunciation inputs.
13) Computer control system input.
14) Identification of components and subsystems delivered by others.
15) Intended physical sequence of the equipment. This figure depicts a very small and
simplified.

31. PID chart is used to read and understand the connections of the instrument. Purpose of
PID to indicate the instruments or control devices attached to the process and to indicate the
control system architecture associated with the process. Standard symbols and notations
representing instruments or control devices are placed to the pipings and vessels. Standard
symbols and notations are available from ISA-5.1(1984) standard. The P&ID will use
symbols and circles to represent each instrument and how they are inter-connected in the
process. Tag “numbers” are letters and numbers placed within or near the instrument to
identify the type and function of the device. The presence or absence of a line determines the
location of the physical device. For example no line means the instrument is installed in the
field near the process. Instrument line symbols:
Figure 6.1: P&ID Symbols

32. Figure 6.2: P&ID signals representation

33. Chapter-7
PROGRAMMABLE LOGIC CONTROLLERS
7.1 INTRODUCTION:
A PROGRAMMABLE LOGIC CONTROLLER (PLC) is an industrial computer control
system that continuously monitors the state of input devices and makes decisions based upon
a custom program to control the state of output devices.
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.
7.2 WHAT DO THE INDIVIDUAL WORDS MEAN:
It may make more sense to look at the words in reverse order.
CONTROLLER –This is the keyword. A PLC monitors various
conditions, and based on these conditions, it determines an
outcome. In other words it has the ability to ‘control’ the
outcome based on the status of different inputs such as sensors,
switches, and numeric values from analog signals, etc.
LOGIC – How the PLC determines an outcome is based on the
logical rules it has been taught. A simple example: it is night
time, AND the door is open, then turn on the light.
PROGRAMMABLE – The PLC is tight the rules to how it
should use the input conditions to create an outcome though its
programming software. Being programmable makes it
versatile, so if needs or conditions change, the PLC can be
reprogrammed to meet these changes.

34. 7.3 HISTORY OF PLCS:
Although PLCs evolved concurrently by different organizations, it is recognized as first being
introduced by Bedford Associates in 1968. It was the product of choice to meet GM’s
Hydramatic Division’s specifications as a replacement for traditional relay- based machine
control systems. The MODICON, as it was called, being an electronic device, also reduced
wiring and troubleshooting time. Because it was programmable, the PLC also allows quicker
changes to the equipment’s control behavior.
Figure 7.1 : Relays replaced by PLCs
The first Programmable Logic Controllers were designed and developed by MODICON as a
relay re-placer for GM and Landis.
 These controllers eliminated the need for rewiring and adding additional hardware for
each new configuration of logic.
 The new system drastically increased the functionality of the controls while reducing
the cabinet space that housed the logic.
 The first PLC, model 084, was invented by Dick Morley in 1969
 The first commercial successful PLC, the 184, was introduced in 1973 and was
designed by Michael Greenberg.

35. 7.4 PLC OVERVIEW:
PLCs come in many shapes and sizes. They can be so small as to fit in your shirt pocket
while more involved controls systems require large PLC racks. The components that make a
PLC work can be divided into three core areas.
 The power supply and rack
 The central processing unit (CPU)
 The input/output(I/O) section
Figure 7.2 : PLC Overview
7.4.1 THE POWER SUPPLY AND RACK:
The rack is the component that holds everything together. Depending on the needs of the
control system it can be ordered in different sizes to hold more modules. Like a human spine
the rack has a backplane at the rear which allows the cards to communicate with the CPU.
The power supply plugs into the rack as well and supplies a regulated DC power to other
modules that plug into the rack. The most popular power supplies work with 120 VAC or 24
VDC sources.

36. 7.4.2 THE CENTRAL PROCESSING UNIT (CPU):
The brain of the whole PLC is the CPU module. This module typically lives in the slot
beside the power supply. The CPU consists of a microprocessor, memory chip and other
integrated circuits to control logic, monitoring and communications. The CPU has different
operating modes. In programming mode it accepts the downloaded logic from a PC. The
CPU is then placed in run mode so that it can execute the program and operate the process.
Since a PLC is a dedicated controller it will only process this one program over and over
again. One cycle through the program is called a scan time.
7.4.3 THE INPUT/OUTPUT (I/O) SECTION:
INPUTS OUTPUTS
 Switches and
Pushbuttons
 Sensing Device
 Limit
Switches
 Photoelectric
Sensors
 Proximity
Sensors
 Valves
 Motor Starters
 Solenoids
 Actuators
 Condition Sensors
 Encoders
• Pressure Switches
• Level Switches
• Temperature Switches
• Vacuum Switches
• Float Switches
 Horns and Alarms
 Stack lights
 Control Relays
 Counter/Totalizer
 Pumps
 Printers
 Fans
Table 7.1 : Input & Output Sections of PLC

37. 7.5 PROGRAM SCAN:
It is helpful when programming a PLC to understand how the Ladder Logic Program is
‘scanned’. Once the PLC is in RUN mode, the CPU executes in the order shown in the flow
diagram.
 Status of the inputs devices are read and stored in data registers.
 Housekeeping of any peripheral devices.
 ‘Scan’ the user’s ladder logic left to right, sequencing through the ‘rungs’.
 Compute the results and write updates to the outputs.
 Do diagnostics and if all is well, repeat the scan.
Figure 7.3: PLC Program scan

38. 7.6 PLC HARDWARE:
Figure 7.4: PLC Hardware
7.7 PLC AT O&M BASE, NASIRABAD:
Figure 7.5 : Honeywell IPC 620-35 Programmable Controller
FEATURES:
 Wide Range of Functionality
 Local, Parallel, Serial I/O
 Functional Capabilities to Meet Any Application
DESCRIPTION:
The 620 Logic Controller (LC) has evolved to meet every challenge — from simple relay
replacement to high-speed, math intensive processing.

39. CONCLUSION
The Practical training has proved to be knowledge booster for me and I have acquired a good
practical knowledge of the field which can’t be gained by reading books. As instrumentation
is used everywhere so it is good for me. The training has proved me with a good knowledge
of instruments at IPS and its operational understanding. It was a very exciting adventurous
and exhaustive training which has raised my practical skills to a great extent. I have gained a
wonderful experience and practical knowledge in this training period. Although the time
period provided was very short for allotted task. Yet I wanted to do many things in detail.
After doing this training I got sufficient confidence for doing such type works for industrial
applications.
I am also thankful to those who had been helpful during my training period.

40. BIBLIOGRAPHY
[1] “Introduction of Gail”, www.gailonline.com
[2] “Process of Gail India Limited”, www.gailonline.com
[3] Pressure Transmitter, User Guide, GAIL, Nasirabad road, Ajmer. Model 9001-2008, 19
July 07, DOC No. IL 03-01-01. Page No. 3.1-3.13.
[4] Valves, User Guide, GAIL, Nasirabad road, Ajmer. Model 9001-2008, 7 December 08,
DOC No. IL 03-01-01. Page No. 4.7-4.12.
[5] Temperature measuring instruments- A. K. Sawhney – “A course in Electrical and
Electronic Measurement”
[6] P&I Diagrams – Process Control: Principles and Applications.
[7] PLC – Tata Honeywell PLC User Guide, GAIL, Nasirabad road, Ajmer. Model IPC 620-
35 Processor. Page No. 6.8-6.17.