2003 Mtps Project Report

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INDUSTRIAL TRAININGREPORTMEJIA THERMAL POWER STATION


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VOCATIONAL TRAINING PROJECT REPORT ON THERMAL POWER PLANT, MEJIA, UNDER DVC

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REPORT ON

INDUSTRIAL

TRAINING AT

D.V.C (M.T.P.S.)

SUBMITTED BY :-1.Avik Chatterjee.

2.Falguni Kumar Ghanty.

3.NirmallyaAddy.

4.Prasanta Karmakar.

5.Sunil Kumar Giri.


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PREFACE

This is a project report on the basic overview of a THERMAL POWER PLANT and all other systems that

are required to carry out the process of power generation. This project was a part of our curriculum of

four years B.Tech degree course. This was a training program for 4 weeks at Mejia Thermal Power

Station under Damodar Valley Corporation; carried out by 5 students of Asansol Engineering College,

named as

1. Avik Chatterjee.

2. Falguni Kumar Ghanty.

3. Nirmallya Addy.

4. Prasanta Karmakar.

5. Sunil Kumar Giri.belonging to The Department of Applied Electronics & Instrumentation Engineering ,at the end of 4

th

semester.

We have carried out this training under well experienced and highly qualified engineers of

MTPS, DVC of various departments viz. Mechanical, Electrical, Chemical and Control &

Instrumentation depts. This report covers an overview of a thermal power station, detailed

specifications of MTPS,DVC, mechanical overview, electrical overview, various cycles and processes

(viz. Steam Generation, Turbo Generation and Balance of Plant) of power generation and details of

control and instrumentation required in thermal power plant. We have taken the opportunity to

explore the Control & Instrumentation Department, its use, necessity in power plant and maintenance

of various instruments used for monitoring and controlling the numerous processes of powergeneration. We have tried our best to cover all the instruments and their brief detailing in this project

report. We have also included our field experiences of MTPS and maintenance section of C&I(Control

& Instrumentation) of MTPS and Logic Panels provided by BHEL (known as FSSS) and

DCS/Microprocessor based system provided by SIEMENS and also Logic and Microprocessor based

system by MAX-DNA. We have also covered a section on SMART TRANSMITERS and ANALYTICAL

INSTRUMENTATION.

All the above mentioned topics will be presented in the preceding pages of this report. The main aim

to carryout this training was to familiarize ourselves with the real industrial scenario, so that we can

relate what we study in our textbooks and their practical applications. This project report will also

help us in our future in many ways when we face the industrial world.


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ACKNOWLEDGEMENT

We,

1.Avik Chatterjee.

2.Falguni Kumar Ghanty.

3.Nirmallya Addy.

4.Prasanta Karmakar.

5.Sunil Kumar Giri.

have carried out this dissertation training report based on the vocational training done by us in

the highly appraised, one of the most technically advanced and one of the largest thermalpower station in West Bengal the Mejia Thermal Power Station ,under DVC .

We would like to express our heartfelt gratitude to the authority of ASANSOL ENGINEERING

COLLEGE & MEJIA THERMAL POWER STATION for providing us the rare opportunity to

undertake training in the power plant.

We would also want to thanks the highly supporting and experienced engineers without whom

we could not have know the plant better.

We would personally like to thanks to

1. Mr. K.K Dey, Personal Manager (A), DVC, MTPS.

2. Mr. N.C Bhowmick, Dy Chief Engineer (C&I),DVC, MTPS.

3. Mr. Yogesh Milan (Asst. Engineer,C&I,DVC,MTPS)

4. Mr. Prabhat Kumar (Asst. Engineer,C&I,DVC,MTPS)

5. Mr. Snehanshu Sarkar(Asst. Engineer,C&I,DVC,MTPS)

6. Mr. Manoj Tiwari(Asst. Engineer,C&I,DVC,MTPS)

We would also like to thanks the maintenance department of C&I (unit iii) to make us

understand the instruments better and the staff of MTPS to help us learn


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-:ABOUT mtps:-

Mejia Thermal Power Station

Mejia Thermal Power Station is located at 35 km from Durgapur city in West Bengal. The

power plant is one of the coal based power plants ofDVC. Commissioned on 1996, MTPS is the

largest thermal power plant, in terms of generating capacity in the state of West Bengal as well

as among other DVC power plants.

Power Plant

Mejia Thermal Power Station has an installed capacity of 2340 MW. The plant has 8 units under

operation.Special features of MTPS include its 16.2 km long spiral welded MS water

pipeline for transporting water from the right bank of Damodar river and 220 mtrs

high RCC multi flue stack which helps in preventing air pollution. Its affluent water

utilization plant has a dual purpose of water conservation and minimization of liquid

affluent discharge. The plant also employs 3 ring granulator type crushers for its

coal handling system reducing the mill rejection from the tube mill. The individual

units has the generating capacity as follows:

Gen.Unit

Name ofManufacturers

Originalcapacity

(MW)

Presentcapacity

(MW)

Year ofcommissioning

Special Features

Boiler TG

1 BHEL BHEL 210 210 March , 1996 DIPC Boilers with zeroreject tube mills.2 BHEL BHEL 210 210 March, 1998

3 BHEL BHEL 210 210 September, 1999

4 BHEL BHEL 210 210 February, 2005

5 BHEL BHEL 250 250 February, 2008

6 BHEL BHEL 250 250

7 BHEL BHEL 500 2010

8 BHEL BHEL 500 2010

Units 1 through 6 are collectively named MTPS- A, while the extension work of 2500 MW

Units 7 & 8 are called MTPS-B. All the units have BHEL make boilers, turbines and generators

installed in them.


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-:BASIC NEEDS AND OVERVIEW OF A THERMAL POWER PLANT:-

The idea that STEAM has potential energy and can be converted into kinetic energy was given by famous

scientist, Sir. James Watt. This idea became the governing principal of many mechanical processes and

finally led to the success of Thermal Power Energy. The need of establishing a Thermal Power Plant

came to engineers by the realization of the fact that Hydel Power could be utilized only for certainperiod of time in a year. This section will give the basic requirements for Thermal Power Plant.

SITE REQUIREMENT: - The basic requirements of thermal power plant is determined by the

type,size and other specifications of the plant. It is required to know the immediate capacity of the

power plant after construction and the extension of capacity in the future, to determine the area

required for construction of the plant. The basic things that are taken into consideration are

1>Station Building Coal Store Cooling Towers Switch yard compound Surrounding

areas and approaching.

GEOLOGY: - The geology of the site should be cost effective and the subsoil must be able to

withstand huge load of foundation.

WATER REQUIREMENT: - Water is required in power plant for two basic needs, first is for steamgeneration and second is for cooling purpose. Thermal Power Plant requires huge volume of

water, nearly of about 3 to 4 Tons/hr/MW only for steam generation. So site of plant must also

have reliable and huge water sources located near to it.

COAL: - Coal is the prime requirement of any thermal power plant, it is the main source of fuel as it

is most economic and residue of coal after combustion is also used by many industries like cement

industries, so the plant must have reliable sources of coal and regular supply in huge amount like

20,000 Tons per week.

TRANSPORT: - It is one of the another vital factor of the plant as huge burden lies on

transportation in daily basis because of huge need of coal, furnace oil, hydrochloric acid and other

chemical products along with mechanical products.

DISPOSAL OF EFFLUENTS: - Due to heavy rate of coal combustion residual volume is also high. The

main residual product is ash. The plant must have facilities like ash pond to dispose them safely

without harming the environment.

TRANSMISSION: - The plant area must have route available for transmission over head cables to

the nearest grid lines or load points which will be capable of accepting the generated power

output of the power station.

CLIMATIC CONDITION: - The tropical climate is best for erection of thermal power plant, because

areas having high humidity and fluctuating temperature lead to dew point and condensation which

as a result damages the electrical machines and corrodes the insulation and over head cables.

PROXIMITY OF AIRFIELDS: - The airfields must be studied properly to avoid mishaps as the

chimney height ranges from 500 to 600 fts and boiler housing is of 200 fts in general.

PERSONNEL REQUIREMENTS: - To run a plant smoothly requirement of skilled and unskilled

personnel is very important. So recruitment of workers and skilled personnel should be madecarefully and in adequate amount.

AMENITIES: - Some considerations like availability of hospital, educational institutes and other

facilities must be taken into account.


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-:MEJIA THERMAL POWER STATION AT A GLANCE:-

Mejia Thermal Power Station also known as MTPS is located in the outskirts of Raniganj in Bankura

District. It is one of the 5 Thermal Power Stations of Damodar Valley Corporation in the state of West

Bengal. The total power plant campus area is surrounded by boundary walls and is basically divided intotwo major parts, first the Power Plant area itself and the second is the Colony area for the residence and

other facilities for MTPSs employees.

TECHNICAL SPECIFICATION OF THE POWER PLANT ALONG WITH SPECIALITIES

INSTALLED CAPACITY: -

1) Total number of Units : - 4*210 MW with Brush Type Generators .

2) 250 MW with Brush less Type Generators :- 2*500 MW Generators

3) Total Energy Generation : - 2340 MW

4) Source of Water : - Damodar River

5) Sources of Coal : - B.C.C.L and E.C.L, also imported from Indonesia6) Required Water Consumption : -

7) Approximate coal requirement : - 73,00,000Tons/annum at 75% PLF(Plant Load Factor)

8) Ash Deposited per annum : - 1.30 million Tons/annum

SPECIALITIES OF MEJIA THERMAL POWER PLANT

1) The plant is designed and engineered by both Bharat Heavy Electricals Ltd (BHEL) and Damodar

Valley Corporation.

2) Pipelines of 17km long and 1473mm in diameter spiral welded MS pipes laid to transport river

water from upstream of Durgapur barrage by pump sets of 500KV pump motor set.

3) Rail cum Road Bridge across Damodar River near Raniganj Station.

4) 2KM Merry Go Round Railway System.

5) 20mtr high RCC multiple flue stack.

6) Direct ignition of pulverized coal introduced for reduction in consumption of fuel oil.

7) Ball and Tube type Mills for more mill rejects and less maintenance cost.

8) Boiler of 200ft height and four corner firing system for better combustion.

9) All major and hazardous systems like Steam Generation and Turbo Generation section are

incorporated with FSSS (Furnace Safety Supervisory System) for better safety.

10) Other logic systems like EAST and ATRS are also incorporated.

11) Water treatment Plants along with two artificial water reservoirs and Two Demineralization

Plants loaded with PLC system.

12) Chimney height upto 600fts for less pollution.13) The plant is loaded with latest technology sensor, transducers and transmitters for more

accurate analyzing of various processes.

14) All the units are loaded with intelligent smart microprocessor based systems known to be

DCS systems provided by KELTRON, SIEMENS and MAX-DNA for process control.

15) Station Service Transformers of 6.6KV step-down type are also available for better

distribution of power inside the plant for various requirements.


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-: UNIT OVERVIEW OF MTPS:-

THE BASIC SCHEMATIC OF THERMAL POWER PLANT COMPRISING OF ALL SYSTEMS IS GIVEN BELOW

THE ABOVE DIAGRAM IS SELF EXPLAINATORY.DETAILED EXPLANATION OF EACH

SYSTEM IS GIVEN BELOW.


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FURNACE AND BOILER: - Boiler is the main section where the steam is

produced by coal combustion. Boiler consists of boiler drum, water walls,

wind box, heaters. The boiler has 13 elevations named as AA-A-AB-B-BC-

C-CD-D-DE-E-EF-F-FF. Coal is inserted into the boiler from A-B-C-D-E-F

elevations. BC is used for insertion of Heavy Oil and Light Oil after

atomization with steam and air respectively. DF is used for insertion of oil

i.e. only heavy oil. Both the elevations have Oil Gun mounted for insertion

of oil in proper ratio into the boiler. Liquid fuel (viz. Heavy Oil and Light

Oil) is used for initial light up process. Other elevations are used to insert

secondary air from wind box. The furnace is divided into two sections

named as first pass and second pass separated by Goose Neck. The

combustion takes place in the first pass and the heating of steam through

super heaters takes place in the second pass.

BOILER DRUM: - Boiler Drum is the part of boiler where thedematerialized water is stored and is inserted into the boiler. It is also houses the steam that is

formed in the boiler. Water stored in the drum comes down to the top of the boiler and forms a

Water Ring which is then inserted into the boiler through the water walls. Water Walls are

basically tubes along the walls of the furnace, it is here where the water is converted into steam

at 1300C and then the produced steam is taken back to the boiler drum. The drum has a

propeller that rotates at high speed and makes the steam and water separated due to

centrifugal force. The pressure of boiler drum is 150kg/sq.cm and must be always maintained.

Water in the drum comes from feed control station via economizer.

SCHEMATIC OF BOILER DRUMCourtesy SIEMENS DCS SYSTEM and C&I Dept, MTPS, DVC

SUPERHEATERS/HEATERS: - One most important point is to be always kept in mind that all

the heaters that are used in thermal power plant are mechanical type heaters, i.e. heat

exchange phenomena heats one medium by exchanging heat from another hotter medium.

Super heaters are actually suspended pipes in the second pass section of the boiler, the flue gas


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having very high temperature heats the steam that comes from the drum before they hit the

turbines. The steam from drum is carried by these pipes and flue gas heats them to raise their

temperature upto 540C. There are three super heaters named as Primary Super heater,

Platinum Super heater and Final Super heater. The steam is cascaded through the above heaters

where the pressure is kept constant and the temperature is raised up to 540C. The main

concept behind making the steam super heated is to make the steam absolutely moisture free

before they hit the turbines because moisture content of steam will damage the blades of

turbine by corrosion.

TURBINE SECTION: - The turbine section consists of three parts named as High Pressure

Turbine (HPT), Intermediate Pressure Turbine (IPT) and Low Pressure Turbine (LPT). The

super heated steam from the super heaters enters the HPT and hits the blades at

150kg/sq.cm and 540C and rotates the shaft. The exhaust steam of HPT is taken to high

pressure heater and the other part enters the IPT through a reheating section called re-

heater for enabling the steam to regain its previous state. The exhaust steam of IPT isused for several purposes, one part is taken to deareator, another to high pressure

heaters and the left out part is taken to LPT. The exhaust of LPT is taken to condenser.

TURBO GENERATOR: - The turbines are attached through a single shaft which is finally

coupled with the generators rotor. The details of the generator are explained later in the Turbo

Generation section.

Unit# 2 MTPS - turbines and generator


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CONDENSER: - The exhaust steam of LPT is fed to the condenser where the steam is converted

into water by the principal of condensation. The condenser has two extraction pumps known as

Condensate Extraction Pumps (CEP-A & CEP-B); these pumps create a negative pressure i.e.

vacuum in the condenser for better suction of the condensate. The outlet of the CEP is

connected to Low Pressure Heaters (LPHS); where the temperature of the condensed water is

raised to little higher temperature for better efficiency of the overall unit/plant.

DEAREATOR: - The condensed water from the condenser is taken to deareator where the

water is made free from oxygen mainly i.e. free from air. The deareator is a direct heat

exchanger because the steam from IPT is sprayed to the condensed water from the bottom and

the water is sprayed from the top part of the deareator. This results in de-oxyfication i.e.

removal of oxygen from the water.

BOILER FEED PUMPS/BFPs: - The outlet of the deareator is connected to boiler feed pumps,there are three BFP in a row out of which two are in running condition and one is at standby.

These pumps have the highest pressure through out the plant i.e. 160kg/sq.cm and consume the

highest power of 3MW/pump. It is so because the BFP pumps the deareated water back to theboiler drum which has a pressure of 150kg/sq.cm, and in order to pump the water to the drum it

needs higher pressure than the drum. The BFP assembly consists of 3 main parts, booster pump

to raise the pressure of water from deareator from 7kg/sq.cm to 17-20kg/sq.cm; asynchronous

motor and hydro-coupling of shaft of motor and pump for speed control and longevity and

finally the main pump that raises the pressure from 17-20kg/sq.cm to 160kg/sq.cm. The inlet

and outlet of the main pump is connected in a feedback system that practically equalizes the

pressure of inlet and outlet and as a result the huge jerk that may damage the BFP due to huge

pressure difference at inlet and outlet isavoided.

BOILER FEED PUMP


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HIGH PRESSURE HEATERS/HPHS: - The high pressure heaters are also mechanical heatersthat receive their heating medium from exhaust of HPT & IPT. The BFP outlet is connected to

HPHS, there are two HPH named as HPH-5 and HPH-6. HPH-5 receives steam from IPT and HPH-

6 receives steam from HPT. The BFP outlet is connected to HPH-5 and HPH-6 is connected toHPH-5. Steam of HPT & IPT heats the water up to 200C and the pressure is also increased up to

175kg/sq.cm, which is then passed through economizer. This is done to increase the efficiency

of the boiler. These heaters are sometimes bypassed during the process if required by the

operator with the help of three way cock/valve of pneumatic type.

HPH 5 & 6

ECONOMIZER: - Economizer is another heat exchanger type heater. Here the water from HPHscomes to get more heated up for better steam production and high enthalpy resulting in greater

efficiency of the boiler and unit as well. The economizer receives the heat for heating the water

from the flue gas. The flue gas which has very high temperature comes from the air pre-heaters(explained later) to the economizer and heats up the water mechanically which finally reaches

the boiler drum.


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FLUE GAS PATH:

AIR-PREHEATER: - The flue gas produced as a result of combustion of fossil fuel in the furnace is taken

to the air-preheater. The air-preheater is used to heat up the atmospheric air to make hot air used for

combustion and transport of coal dust from mill to furnace; which is called secondary air. This heater

has a unique process of heating, it has a shaft attached to a rotating wheel type structure (like turbine

but arrangement of blades are different). Atmospheric air sucked by FD fans passes through one side of

the rotating shaft and the hot flue gas passes through another side. This way heat of the flue gas gets

transferred to the atmospheric air and it gets heated. There are two air-preheaters named as AH-A and

AH-B. These heaters can be found beside the boiler in the burner floor.

ELECTRO STATIC PRECIPITATOR/ESP/EP: - The flue gas after passing through the air-preheaters

comes down to lower temperature that is feasible for releasing into the atmosphere, but one vital job

remains still left out, i.e. to remove the carbon content of the gas so that it does not harm the

atmosphere. This job is done by ESP, the flue gas after air-preheater comes to the ESP unit. ESP actually

works on the principal of CORONA DISCHARGE EFFECT; the ESP unit houses two electrode plates

called emitting plate and collecting plate. The emitting plate is supplied with a very high DC negative

potential (in order of**), this results into ionizing of air molecules surrounding the emitting plate which

is called corona effect. The collecting plate is grounded and a positive potential develops on it, as a

result when the flue gas pass through between them the carbon particles are attracted to the collecting

plates. The collecting plates are attached to hopper where the ashes get deposited by hammering action

on the collecting plate. For a 210MW unit 24 such hoppers are present in each ESP; these hoppers have

mechanical transport system for proper disposal of ash. For better corona effect the emitting plate is

made corrugated because this way more air molecules get ionized as corona discharge points are more

in number in corrugated plate.

ESP


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DRAFT FANS: - THERE ARE BASSICALLY 4 TYPES OF FANS IN A THERMAL POWER UNIT

INDUCED DRAFT FAN/ ID FAN

FORCED DRAFT FAN/ FD FAN

PRIMARY AIR FAN/ PA FAN

SCANNER AIR FAN/ SC FAN/ SA FAN

INDUCED DRAFT FAN/ ID FAN: - This fan is used to create negative pressure in the furnace, i.e.

furnace pressure is lower than the atmospheric pressure, as a result of which the fire ball inside the

furnace cannot come out of the furnace. ID fan also drives the flue gas through out its path and above

processes and finally ejects it out of the chimney. It sucks air from inside the furnace and ejects it to the

atmosphere. Mechanically ID fan consists of one 3-phase asynchronous type motor, a hydro coupling

unit for coupling rotor shaft of the motor and the rotor shaft of the fan, scoop unit, a pair of journal

bearings and lubrication oil system. It is the only fan which have hydro coupling because this gives more

accurate control to its speed for maintaining the negative pressure more precisely since controlling of

negative pressure is the most vital factor in any thermal power unit. The lube-oil system has two motors

out of which one remains standby; for maintaining perfect pressure of lubrication through out the ID fanassembly. The second motor automatically starts up when the oil pressure drops below a certain level;

this motor increases the oil pressure in the system. The lubrication oil is cooled by mechanical heat

exchangers; this system is mounted in the lube-oil system itself. Water cools down the oil flowing in the

tubes inside the coolers. There are three ID Fans in each unit of thermal power plant, named as ID-A, ID-

B, ID-C.

FORCED DRAFT FAN/ FD FAN: - Unlike the ID fan, the FD fan is meant for creating positive pressure inthe furnace and also supplies air for PA fan and secondary air for combustion. The FD fans take air from

atmosphere and expel it to the plant (i.e. in the furnace, wind box etc). The outlet of the FD fan divides

into 5 ways; 2 goes to the air-preheater, and remaining 3 goes to the PA fan supplying cold air.

Mechanically FD fans consist of one 3-phase asynchronous type motor, a pair of journal bearings andlube-oil system. Unlike ID fan these fans have direct coupling of rotor shaft of the motor and rotor shaft

of the fan. The lube-oil system is designed same as ID fans. There are 2 FD fans in a single unit.

***NOTE: - THE SYNCHRONIZATION OF ID-FAN AND FD-FAN IS VERY IMPORTANT AS THESE

TWO FANS COMBINELY BALANCE THE PLANT. WHEN WORKING TOGETHER IT IS CALLED

BALACED DRAFT.

PRIMARY AIR FAN/ PA FAN: - Primary air fan is used for mixing of cold air of FD fan outlet and hot airof air-preheater outlet. The main function of this is to transport the pulverized coal from the mill to the

furnace via classifier. Mixing of hot and cold air is necessary because it is needed to maintain the

temperature of the pulverized coal from 80C-90C for better transport of coal and better combustion in

the furnace. Mechanically the construction of PA fan is same as FD fans along with the lube-oil system.

There are 3 PA fans in a single mill of ball and tube type.

SCANNER AIR FAN/ SC FAN/ SA FAN: - The scanner air fans are relatively smaller in size andconsume low power as compared to the above mentioned fans. These are simple motor operated fans


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that suck air from atmosphere and utilize it to cool the flame scanners (explained in C&I section later)

inside the furnace.

-:COAL HANDLING PLANT (CHP) AND MILL:-

COAL HANDLING PLANT: - The coal handling plant comprises of track hopper, crusher house,conveyer belt system and bunker. For running of each unit at a minimum of 75% PLF requires

20,000Tons of coal per day. The huge demand coal is mitigated by B.C.C.L and E.C.L collieries, extra

demand of coal is sometimes fulfilled by imported coal from Indonesia. The main transportation

system is railways and trucks. The coal is directly unloaded in the track hopper, which have bottom

discharging system. Coal of size up to 20mm diameter is passed on to crusher house and the rest is

manually crushed up to 20mm diameter size. In the crusher house the coals are further crushed

down to 5mm diameter by mechanical procedure. These crushed coals are passed through strainers

to the conveyor belt system for dropping them into the bunker above the feeder through STACKERS

and RECLAIMERS. After this process the coal in the CHP is handed over to the MILL.

UNLOADING OF COAL FROM BOBR TYPE WAGON


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TRACK HOPPER (STAGE-1)

MILL (PULVERIZER): - The MILL consists of FEEDER, MILL for pulverization of coal (BALL & TUBETYPE MILL) and CLASSIFIER. The stacked coal in the bunker is dropped to the feeder automatically;

the feeder is housed with a conveyor belt system with motors and pulleys. The feeder actually

governs the amount of coal to be transferred to the ball & tube mill for pulverizing. The flow of coal is

maintained by the speed/rpm of the conveyor belt of the feeder. The coal from the bunker drops tothe feeders conveyor belt at a constant rate determined by the bunker level, in this condition higher

the rpm of the conveyor belt greater will be the rate of volume of the coal transferred to the mill. In

the same way if the rpm is lower than lesser will be the volume of coal transferred to the mill.

Thus the coal from the feeder is transported to the mill where the pulverization takes place. Here

the ball & tube method is utilized for pulverizing of coal to 20micron diameter size. This type of

mill consists of arrangement of iron alloy balls inside a tube like structure that is rotated by its

auxiliaries. The coal is fed to the tube at its two ends where it is crushed to the above mentioned

size, these pulverized coal is taken back from the mill to the classifier. In case of ball and tube

type mills, there are 3 mill units; out of which 2 must be running and 1 for standby while the unit

is running on load.

The classifier consists of strainers; the primary air brings the coal from the mill to the classifier

where the pulverized coal is passed through strainers. The strainers allow 80 %(approx) of the

coal to pass from 200 mesh and rest is fed back to the mill for further pulverization. Here the

primary air is utilized to maintain the temperature of the coal up to 80C-90C for better

combustion. The classifier has 4 outlets and each ball and tube type mills have 6 such classifier (2

for each mill unit). The coal from each outlets of a classifier goes to each of the 4 corners of the


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furnace; therefore coal from each outlets of all the 6 classifier goes to all the 24 elevations (A-B-

C-D-E-F of each corner) of furnace in all. All transport of coal from mill to the furnace is done by

the primary air produced by PA fans.

BALL AND TUBE TYPE MILL

IRON BALLS USED INSIDE MILL


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***NOTE: - BALL AND TUBE TYPE MILL IS STILL IN USE BECAUSE OF LOW MAINTAINANCE COST

AND HIGHER MILL REJECTS.

SELF EXPLANATORY SCHEMATIC OF SINGLE MILL UNIT OF BALL AND TUBE TYPE

Courtesy SIEMENS DCS SYSTEM and C&I Dept, MTPS,DVC


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-: STEAM GENERATION PROCESS (SG):-

SCHEMATIC DIAGRAM OF STEAM GENERATION

WATER PATH: -Water comes from the water reservoir to the demineralization plant (DM Plant)

for removal of all minerals present in normal water for making it non-conductive and increasing

the efficiency of the overall system. After DM plant water goes to the boiler drum via condenser

and the feed control station.

STEAM GENERATION PROCESS: - Water from the boiler drum comes down to the top of the

boiler and forms a ring head and finally goes to the boiler through the water walls. The

boiler/furnace is lit up by four corner firing technique; this produces a ball of fire and reaches

a temperature of 1200C. This as a result converts the water in the water walls into steam at

high pressure. This steam is sent back to the boiler drum where it is separated from the water

with the help of high speed propeller. The steam is taken to the super heaters via water pipes

where it is converted to superheated steam for total moisture removal. After superheaters the

steam divides into two ducts called Main Steam Left (L) and Main Steam Right(R) and finally

reaches the turbines.


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-: TURBO GENERATION SECTION (TG):-

SCHEMATIC DIAGRAM OF TURBINE GENERATION

TURBINES are form of engine and hence it requires suitable fluid for working, a source of high grade

energy and a sink of low grade energy, the fluid when flows through the turbine the energy content of it

is continuously extracted and converted into its useful mechanical work. The turbines used in thermal

power plants are of STEAM GAS type which uses the heat energy of the steam for its working. Turbine

Cycle is the most vital part of the overall process; this is where the mechanical energy of the steam is

converted to electrical energy via turbine assembly. The turbine assembly comprises of three turbines

named as High Pressure Turbine (HPT), Intermediate Pressure Turbine (IPT) and the Low Pressure

turbine (LPT).

The steam that is generated in the SG section comes to the HPT through main steam lines via control

valves. The steam when strikes the HPT have 540C at 150kg/sq.cm pressure. This high pressure


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superheated steam rotates the turbine, the speed of the turbines is controlled by the controlling the

amount of steam through control valves. Generally only 3%-4% steam is enough to rotate the turbine at

3000rpm at no load. The HPT is a single head chamber type of turbine.

One part of the exhaust steam from HPT is taken to reheaters through cold reheat line (CRH line) which

are again of mechanical type; for restoring the superheated properties of the steam for further use. Thereheated steam is brought back to the IPT via HRH (hot reheat steam) line. And the other part of the

exhaust steam is taken to the HP heaters (i.e. to HPH-6).

The reheated steams mechanical energy is utilized by the IPT which is a double head chamber type

turbine, where steam enters from the top-mid section of the turbine and leaves the turbine from the

front and back section. The exhaust of IPT is divided into 3 parts, one goes for the HP heaters (HPH-5),

another goes to the deareator and the last part goes to the LPT.

The exhaust steam of the LPT Is divided into 4 parts, 3 of them goes for the Low Pressure Heaters (LPH-

1, LPH-2, LPH-3) for heating the condensate, and the last part goes to the condenser for the steam

condensation process and regeneration of water. The condensation is done to minimize the production

of DM water to make the process cost effective. The steam is converted to water and extracted by CEP

from the condenser and transported to Gland Sealing Coolers (GSC) via Ejectors (EJE). The GSC cools the

sealing of the ducts; the condensate is taken to the LPH from the GSC for heating at lower pressure to

increase the enthalpy of the water for better efficiency. Water after LPH reaches the deareator where

the oxygen is removed from it and is taken to the BFPs, the BFPs increases the pressure of the water up

to 160kg/sq.cm and sends it the high pressure heaters (HPH-5 & HPH-6). HPH increases the temperature

of the water once more and transfers it to the Economizer, in economizer the temperature of water is

again increased by the flue gas and is finally is transported to the steam generation process via the Feed

Control Station.

***NOTE: - At full load condition 100% steam is required to rotate the turbine at 3000rpm, because to

produce power at 50Hz frequency the rpm required is 3000.

-:MECHANICAL CONSTRUCTION OF TURBINE ASSEMBLY:-


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The 200/210 MW turbine installed in MTPS is of condensing-tandom-compound, three cylinder,

horizontal, disc and diaphragm, reheat type with nozzle governing and regenerative system of feed

water heating and is directly coupled with the A.C generator.

TURBINE CASING: - The turbine assembly comprises of three types of casing.

1) High Pressure Casing

2) Intermediate Pressure Casing

3) Low Pressure Casing

OTHER TURBINE COMPONENTS: -

ROTOR: - The rotor is basically the main rotating part of the turbine which is also called the shaft

and is attached with the rotor of the A.C generator via coupling.

Rotor is basically divided into 3 categories and they are as follows: -

1) HIGH PRESSURE ROTOR: - This is basically made of single Cr-Mo-V steel forged with

internal disc attached to T-shoot fastening designed specially for stabilizing the HPT

and preventing the axial shift.

2) INTERMEDIATE PRESSURE ROTOR: - This is made from high creep resisting Cr-Mo-V

steel forging and the shrunk fit disc are machined from nickel-steel forging. This

basically adjusts the frequency of the blades.

3) LOW PRESSURE ROTOR: - This is made from the above mention alloy used in IP Rotors;

blades are secured to the respective disc by riveted fork root fastening. Wires are

provided in all stages of this to adjust the frequency of the blades.

BLADES: - Blades are single most costly element fitted in the turbine. Blades fitted in the

stationary part are called guide blades and those fitted in the rotor are called moving or working

blades. Blades are of basically three types, they are as follows: -1) Cylindrical ( constant profile) blade

2) Tapered cylindrical blade

3) Twisted and varying profile blade.

SEALING GLANDS: - To eliminate the possibility of steam leakage to the atmosphere from the

inlet and the exhaust end of the cylinder, labyrinth glands of the radial clearance type are

provided which provide a trouble free frictionless sealing.

EMERGENCY STOP VALVES AND CONTROL VALVES: - Turbine is equipped with emergency stop

valves to cut off steam supply and with control valve regulate steam supply. Emergency stop

valves are provided in main stream line and control valves are provided in the hot reheat line.

COUPLING: - Since the rotor is made in small parts due to forging limitations and other

technological and economic reasons, the couplings are required between any two rotors. The

coupling permits angular misalignment, transmits axial thrust and ensures axial location.


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BEARING: -Journal bearing are manufactured in two halves and usually consist of bearing body

faced with anti friction tin based habiting to decrease coefficient of friction. Bearings are usually

force lubricated and have provision for admission of jacking oil.

Thrust bearing is normally Mitchell type and is usually combined with a journal

bearing, housed in spherically machined steel shell. The bearing between HP and IP rotor is ofthis type. The rest is of journal type.

BARRING GEAR: - The barring gear is mounted on the L.P rear bearing cover to mesh with spur gear

L.P rotor rear coupling. The primary function of the barring gear is to rotate the rotor of the turbo

generator slowly and continuously during the start-up and shut sown process when the temperature

of the rotor changes.

At the time of shut down the cooling of the inner parts of the turbo-generator continues for

many hours. If the rotor is allowed to stand still during cooling process then it will suffer from

shagging due to the temperature difference between the upper and lower portion of the

turbine. It is therefore kept in barring gear for maintaining constant temperature through out

the turbine.

The same phenomena is observed during the start up of the turbine, because when the steam is

supplied to the sealings to create vacuum, the stand still rotor will suffer from un-uniform

heating and hence suffer from shagging. It is therefore kept in barring gear to avoid such

damage and it prevents the breaking away of the turbine blades with sudden flow of steam into

the turbine assembly.

TURBINE LUBRICATION OIL SYSTEM: - The LUB-OIL system of turbine comprises of following

category.

1) MAIN OIL PUMP: - It is mounted on the front bearing pedestal and coupled through

gear coupling to the rotor. When the turbine is running at its normal speed of 3000rpmthen the oil to the governing system (at 20kg/sq.cm) and to the lubrication system (at

1kg/sq.cm) is supplied by this pump.

2) STARTING OIL PUMP: - It is a multi staged centrifugal oil pump driven by A.C powered

electric motor. It provides the oil requirement for starting up and stopping of the

turbine. It provides oil to the governing system and to the lubrication system until the

turbine is running at speed lower than 2800rpm.

3) STANDBY OIL PUMP: - This is a centrifugal pump driven by A.C motor. It runs for initial

10 minutes at the starting to remove air from the governing system and fill up oil to it.

4) EMERGENCY OIL PUMP: - This is a centrifugal pump driven by D.C motor. This pump is

foreseen as a backup oil pump to A.C oil pumps. This pump automatically cuts in when

the A.C power fails in the power station.

5) JACKING OIL PUMP: - This pump enables the complete rotor assembly to be raised up or

to be floated in the bearing assembly during the start-up and shut down process of the

process. Thus this prevents the damage to the bearings when the shaft is too low for

hydrodynamic lubrication to take place. JOP sucks and delivers oil to the journal

bearings at 120kg/sq.cm for lifting of the rotor.

6) OIL COOLERS: - The oil of governing and lubrication system is cooled in the oil coolers by

the circulating water. There are five such coolers,4 are for continuous operation and 1

for standby.


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MAIN OIL TANK COOLER

OIL CENTRIFUGE SYSTEM


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-: OTHER IMPORTANT CYCLES:-

***NOTE: - THE MENTIONED CYCLES CAN BE EXPLAINED BY THE SELF-EXPLANATORY DIAGRAMS GIVEN

BELOW

CONDENSATE CYCLE: - THE SCHEMATIC GIVEN BELOW DESCRIBES THE CONDESATE PATHPRODUCED IN THE CONDENSER, IT IS SELF-EXPLANATORY

Courtesy SIEMENS OS220EA, C&I, MTPS, DVC


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FEEDWATER CYCLE: - THE SCHEMATIC GIVEN BELOW DESCRIBES THE RECYCLING PATH OF DM

WATER THAT IS FED BACK TO BOILER DRUM THROUGH FCS

Courtesy SIEMENS OS220EA, C&I, MTPS, DVC


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-: GENERATOR:-

SPECIFICATIONS OF MAIN GENERATOR

GENERATOR: -The transformation of mechanical energy into electrical energy is carried out by

generator. The A.C generator or alternator is based on the principal of electromagnetic induction

and generally consists of a stationary part called stator and a rotating part called rotor. The stator

houses the armature windings and the rotor houses the field windings. A D.C voltage is applied to

the field winding in the rotor through slip rings, when the rotor is rotated, the lines of magnetic flux

is cut through the stator windings. This as a result produces an induced e.m.f (electromotive force)

in the stator winding which is tapped out as output. The magnitude of this output is determined by

the following equation.

E = 4.44/O FN volts

Where E = e.m.f induced

O = Strength of magnetic field in Weber

F = Frequency in cycles per second or in hertzN = Number of turns in the winding of the stator

Again F = Pn/120

Where P = Number of poles

n = revolutions per second of the rotor


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From the above expression it is clear that for the same frequency number of poles increases with

decrease in speed and vice versa. Therefore low speed hydro turbine drives generators have 14to 20

poles where as for high speed steam turbine driven generators have 2 poles.

GENERATOR COMPONENTS: -

ROTOR: -Rotor is the most difficult part to construct; it revolves at a speed of 3000rpm. The massive

non-uniform shaft subjected to a multiplicity of differential stresses must operate in oil lubricated

sleeve bearings supported by a structure mounted on foundations all of which poses complex

dynamic behavior peculiar to them. It is also an electromagnet and to give it the necessary magnetic

strength the windings must carry a fairly high current. The rotor is a cast steel ingot and it is further

forged and machined. Very often a hole bored through the center of the rotor axially from one end

to the other for inspection. Slots are then machined for windings and ventilation.

ROTOR WINDING: - Silver bearing copper is used for the winding with mica as insulation between

conductors. A mechanically strong insulator such as micanite is used for lining the slots. For cooling

purpose slots and holes are provided for circulation of cooling gas. The wedges the windings when

the centrifugal force developed due to high speed rotation tries to lift the windings. The two ends ofthe winding are connected to slip rings made of forged steel and mounted on insulated sleeves.

STATOR: - The major part of the stator frame is the stator core, it comprises of inner and outer

frame. The stator core is built up of a large number of punchings or section of thin steel plates.

The use of cold rolled grain-oriented steel can contribute to reduction of stator core.

STATOR WINDINGS: - Each stator conductor must be capable of carrying the rated current without

overheating. The insulation must be sufficient to prevent leakage current flowing between the

phases to earth. Windings for the stator are made up from copper strips wound with insulated tapes

which is impregnated with varnish, dried under vacuum and hot pressed to form a solid insulation

bar. In 210MW generators the windings are made up of copper tubes through which water iscirculated for cooling purpose.

GENERATOR COOLING AND SEALING SYSTEM: -

1) HYDROGEN COOLING SYSTEM: - Hydrogen is used as cooling medium in large capacity

generators in view of its high heat carrying capacity and low density. But in view of its

explosive mixture with oxygen, proper arrangement for filling, purging and maintaining its

purity inside the generator have to be made. Also in order to prevent escape of hydrogen

from the generator casing, shaft sealing system is used to provide oil sealing. The system is

capable of performing the following functions.

a) Filling in and purging of hydrogen safely

b) Maintaining the gas pressure inside the machine at the desired value all the time.c) Provide indication of pressure, temperature and purity of hydrogen.

d) Indication of liquid level inside the generator.

2) GENERATOR SEALING SYSTEM: - Seals are employed to prevent leakage of hydrogen from the

stator at the point of rotor exit. A continuous film between the rotor collar and the seal liner is

maintained by means of oil at the pressure which is about above the casing hydrogen gas

pressure. The thrust pad is held against the collar of rotor by means of thrust oil pressure,


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which is regulated in relation to the hydrogen pressure and provides the positive maintenance

of the oil film thickness. The shaft sealing system contains the following components.

a) A.C oil pump.

b) D.C oil pump.

c) Oil injector.

d) Differential Pressure Regulator

e) Damper tank.

EXCITATION SYSTEM: - The electric power generators require direct current excitation magnets for

its field system. The excitation field system must be reliable, stable in operation and must respond

quickly to excitation current requirements. The excitation system of a generator comprises of

a) The main exciter

b) The pilot and auxiliary exciters

c) The voltage control system

TRANSFORMERS: - It is a static device which transfers electric powers from one circuit to the other

without any change in frequency, but with a change in voltage and corresponding current levels

also. Here the transformers used are to transfer electric power from 15.75KV to 220KV or 400KVthat are provided to the national grid. The step-up generator transformers are of

ONAN/ANOF/AFOF cooling type.

220 KV TRANSFORMER


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-: CONTROL AND INSTRUMENTATION (C&I):-

INTRODUCTION: -Control and Instrumentation in any industry can be compared to the nerve

system of the human being. The way the nerve system controlling the operation of various limbs

of human being, C&I in the same way is controlling and operating the various motors, pumps,

dampers, valves etc. In a Thermal Power Station chemical energy of coal is converted to electricalenergy, this happens in three stages which are boiler, turbine and generator. The actions

happening in them are controlled, transmitted and monitored by C & I department. In this art of

state era a remarkable revolution has taken place in the field of instrumentation. Digital Control

System (DCS) has replaced the conventional instrumentation system. The main purpose of C & I is

to guide the operating personnel, to operate the plant efficiently, to test the performance of the

plant, to record the history, to generate audio-visual alarm and tripping signal if required.

PROCESS PARAMETERS IN C&I: -There are mainly four types of parameters to be measured,

controlled and monitored. These are as follows.

a) FLOW: - Flow means flow of any fluid like water, oil, flue gas, steam etc.

b) TEMPERATURE: - Temperature of boiler, turbine shaft, flue gas, coal, steam etc.c) PRESSURE: - Pressure of boiler and boiler drum, steam, lube-oil, water etc.

d) LEVEL: - Level of boiler drum, hydrogen, water, lube-oil tank etc.

CLASS OF INSTRUMENTS: - Instruments are basically divided into two classes called Primary

Instrument and Secondary Instrument. Primary Instruments mainly comprises of Sensors, Gauges,

Transmitters etc and Secondary Instruments comprises of Indicator, Recorder and Data

Acquisition System (DAS) etc. Depending on the importance of the parameter to be measured,

these instruments are mounted (i) on Spotmainly Local Gauge( Pressure & Temperature), Rota

meter Type Flow Meter etc, (ii) on Local Panel or Instrument Rackmainly local panel gauge, local

indicator, transmitter/transducer etc and (iii) on Panel at Unit Control Roommainly Secondary

Instruments i.e. recorder, indicator and DAS etc.

PRESSURE MEASUREMENT: - Pressure and vacuum are the most important process parameters

of the thermal power plant. Still drum pressure, steam pressure at turbine end, deareator

pressure, furnace pressure, lube-oil pressure, furnace oil pressure, feed water pressure,

condenser vacuum are the most important process parameters. The instruments commonly

used are

Bourdon Tube Pressure Gauge: - Curved or Twisted tube whose transfer section differs

from a circular form. The tube is closed at one end and if bend or distorted has the

property of changing in shape with internal pressure variation which causes the cross

section to become more circular and the shape to be straighten resulting in motion of

the closed end of the tube. This motion makes a pointer to travel on a scale thusshowing the pressure applied. These types of gauges are basically used in the following.

a) Boiler and Boiler Drum

b) Steam Lines

c) Water Lines

d) Flue Gas Path

e) Oil Lubrication System and Oil Lines


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C-TYPE BOURDON GAUGE

SPIRAL TYPE BOURDON GAUGE


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Diaphragm Bellow Pressure Gauge: - Diaphragm is a flexible disc usually with concentric

corrugate. This converts pressure to deflection. Commonly used metals to make

diaphragm are Phosphor-Bronze, Beryllium-Copper and Stainless Steel etc.

Bellowis a thin walled metal tube with deeply convoluted side walls which permits axial

expansion and contraction. Materials used are Brass, Phosphor-Bronze, Monel, Stainless

steel, Beryllium-Copper, Inconel etc. These are used where high force measurementrequired. These are basically use in Analog Transmitters and Limit Switches.

U-Tube Manometer: - Both tend opened up U-Tube partially filled with mercury is used

for this purpose. At one end atmospheric pressure is applied and the other end is

applied with the applied pressure. For the differential height gives the pressure.

Strain Gauge: - Any form of container when pressurized is strained, it is a resultingwhich is sensed by bonded wire type strain gauge fitted onto the surface. The O/P of

strain gauge is calibrated in terms of pressure.

Pressure Switch: -Pressure switches are also applied as limit Switch; these are basically

constructed with a bellow, spring and a micro-switch arrangement. When pressure is

applied to the bellow connected at the bottom of the pressure switch, it pulls the spring

just fixed above it. As a result of the restoring torque of the spring it contracts or relaxes


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opposing the direction of force applied by the bellow to it. The spring is connected to a

micro-switch; the spring makes the contact to NO or NC contact depending on the type

of connection and generates an alarm or trip signal as required after crossing the

maximum restoring torque value.

Transmitters: - There are two types of transmitters called as Analog Transmitters and

Digital/Smart Transmitters.

Smart TransmittersICP are integrated circuit piezo-electric sensors with built in

microelectronics (amplifier and signal conditioner) which operate over a simple two

wire cable is called smart sensor. When microprocessors and miniature electronics are

used with transmitter for storing important parameters like range, scale, calibration, self

diagnostic troubleshooting etc. with a remote with a capability for sending data to and

receiving data for a measuring unit located at field. It has following advantages as Drift

Free, Calibration remote and easy and can be directly connected to modern DCS system.

TEMPERATURE MEASUREMENT: - Like pressure temperature is also a most important process

parameter of a thermal power plant. Temperature is measured at various parts of the process.

Temperature measurement is done of steam, Drum, SH & RH metal, T/G lube oil& bearing

Babbitt, Generator Gas, HPT exhaust etc. The instruments used for temperature measurement

are basically of Expansion type, Radiation type or electrical type. The instruments used are: -

Expansion Thermometers: - For measurement of temperature at parts of process which

is of comparatively less importance or high accuracy is not required. At these places

expansion type thermometers are used, usually Mercury filled, Mercury vapour fill bulb-

capillary type and bimetallic temperature gauges are used for the temperature

indication required for guidance of operating personnel.These are used in steam lines,

bearing, water lines, heaters etc.

Thermocouple: - It converts thermal energy to electrical voltage when a temperature

gradient exists between two end junctions of a pair of dissimilar metal wires. Open

circuit developed voltage is a function of Seebeck co-efficient of the two metals and the

difference in temperature. Usually K-type thermocouple is used in a power plant. K-type

thermocouple is a combination of CHROMEL (+ve) and ALUMEL (-ve). This can be used in

clean oxidizing atmosphere upto 1260C, so most commonly used in thermal power

plants. This could not be used at oxygen starved atmosphere as temperature mv

characteristics will no longer follow standard curve.

Some disadvantages of thermocouple: -

1) Accuracy less than RTD

2) Resolution cannot be lowered than 10mv/degC3) Drift characteristics curve drifts at higher temperature

4) Leads only composite leads can be used

5) Construction high precession silvering soldering with borux flux required.

Some Advantages of thermocouple: -

1) Response time low as the wires can be made very thin so response time can be of

the order of msec. Grounded elements are faster than ungrounded. For metal


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temperature measurements surface cement type thermocouple are used for fast

response.

2) High shock absorber as the construction is heavy duty.

3) Small in size

4) Probes can be made flexible.

5) Cost effective.

THERMOCOUPLE WIRE CONFIGURATION

THERMOCOUPLE

RTD ( Resistance Temperature Detector) : -RTD works on the principal that metals

resistance increases with increase in their temperature. They are used for measurement

of temperature within the range of upto 400C.

Advantage: -

1) Higher accuracy

2) Can be used over wide range from -200C 500C

Mainly used Platinum and Copper type metals are used with Platinum being moreadvantageous because of noble character, commercially availability in pure form and

high melting point. Pt100 is mostly used in power plants for Air, Water, Water Windings

etc temperature measurements.

Cu53 are used in power plants for turbine bearings and generator winding temperature

measurement.


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Disadvantage: -

1) Not suitable for high temperature and vibrational site

2) Circuits to be made low voltage driven otherwise self-heating take place.

Thermistors: - Non-metallic semi conductors with negative temperature coefficient of

resistance are used for this purpose. These are more sensitive and smaller in size usedupto 100C, used for HT drive bearing temperature measurement. These are mainly

made up of mixtures of metallic oxides, e.g. manganese, nickel, copper etc.

Radiation Thermometer: - Radiation energy emitted by a body increases with

temperature and thus this property is used for measurement of temperature by the

formulae W = OeT^4 ( W Radiant energy, O stephens constant, e emissivity of the

surface and T absolute temperature).

Advantage: - 1) High range of temperature measurement

2) Direct Contact not require and long lasting.

Disadvantages: -High cost, regular maintenance and calibration not uniform.

This is used for furnace temperature measurement.


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Flame Scanner: - This instrument is to measure the intensity of the flame inside the

furnace. The construction consists of a convex lens, a fiber optic cable attached at the

focal point of the lens and a photo diode circuit at the end of the fiber optic. The light of

the flame is focused on the focal point of the lens by the lens, the fiber optic takes the

light and the light travels through the fiber cable due to total internal reflection to the

diode, as a result a voltage is forward biased by the diode and output is observed. The

voltage at the output changes as the intensity of the light changes, a signal conditioning

unit is attached to it which transmits the voltage signal to the control room as current

signal of 4-20mA.

FLOW MEASUREMENT: - Flow can be measured by flow rate and flow volume.

Classification: -1) Pressure differential flow meter: -

Venturi Tubes: - Available in two forms. Nozzle entrance type consists of a cylindrical

entrance section followed by a nozzle entrance throat followed by a conical divergent

section, pressure taps are taken at face and throat of nozzle section.

Conical entrance type consists of cylindrical entrance section followed by a conical

convergent section leading into a cylindrical throat which in turn is followed by a conical

divergent section. Pressure taps are taken at a distance of half pipe diameter from the

start of the converging cone and in the center of the cone.

Orifice: -It consists of a thin metal plate with a center hole, upstream sides has a sharp

edge of the hole. The pressure taps must be one at upstream and one at downstream. Itmust be used where head loss is not considered.

Nozzle: - Restriction part of the nozzle consists of a convergent portion of rounded

profile and a cylindrical throat. Corner pressure taps should only be used. Nozzle should

be used where head loss is not very important.


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Differential Pressure Transmitter: - This type of transmitter consists of a diaphragm

type capacitive capacitance. Pressure is as applied at two terminals of the transmitter

i.e. at the high and low terminal. The plates constrict or relax according to the pressure

of both the terminal and hence the capacitance is changed due to change in area of the

plates. This is connected to a bridge circuit, the impedance of circuit changes with the

change in capacitance and an output is observed which is calibrated according to the

pressure difference of high and low terminals.

Mechanical Type Flow Meter: -

1) Turbine Type Flow Meter.

2) Target Flow Meter3) Open Channel Flow Meter

4) Mass flow Meter

5) Ultrasonic Flow Meter


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LEVEL MEASUREMENT: -

Direct Measurement: - Gauge glasses are fitted by the side of the tank directly to have

the level measurement locally.

Indirect Measurement: -

1) HYDRASTEP.

2) CAPACITIVE SYSTEM

3) DIFFERENTIAL PRESSURE SYSTEM

4) ULTRASONIC SYSTEM

5) FLOAT SYSTEM

Depth gauges measure the depth of liquids and powder in tanks. They use a variety of principles and

produceoutputs in electrical and pneumatic forms. The type to use depends on the substance in the

tank. Here are a few.

The ultrasonic system reflects sound waves from the surface and determines the depth from the timetaken to receive the reflected sound. The electronic version uses a variety of electrical affects including

conduction of the fluid and capacitance. The pneumatic version bubbles air through the liquid and the

pressure of the air is related to the depth. A simple pressure gauge attached to a tank is also indicates

the depth since depth is proportional to pressure.

ANALYTICAL INSTRUMENTS: - The analytical instruments that are used in power plant can be

broadly classified as stack monitoring instruments, gas analyzer and steam and water analyzer.

Few analytical instruments are as follows.

1) OXYGEN ANALYGERS

2) HYDROGEN PURITY METER

3) OPACITY MONITOR METER4) SOx AND NOx ANALYZER

5) SWAS ( Steam and Water Analytical System)

6) pH MEASUREMENT INSTRUMENT

7) CONDUCTIVITY MEASUREMENT

8) SILICA ANALYZER

9) SODIUM ANALYZER

10) HYDRAZIN ANALYZER


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PID CONTROLLERS: - The combination of Proportional, Integral and derivative is called PID

controller which is required to control difficult processes.

When the error changes rapidly the controller can anticipate what action is needed for more

correction and so that the error reduces. The corrective action is called derivative action. The

combination of P & I and the rate of change of error are used to reduce offset caused by any

disturbance over a period of time.

I/P (Electro Pneumatic Converter) : - An I/P converter converts the electrical signal to

pneumatic signal by flapper nozzle device and force balance device. It has a supply line of

instrument air and a signal input, the 4-20mA signal transmitted by the control unit is received

by the I/P converter and it supplies the air pressure at its output required according to the

supplied signal. The range of I/P converter output is 0.2 1 kg/sq.cm of air.

POSITIONER: - The positioner is a high gain proportional controller and the primary function is

to ensure that the control valve position is always directly proportional to the controller output

pressure 0.2 1kg/sq.cm regardless of gland fiction, actuator hysteresis, off balance of forces on

the valve plug etc. The pressure range of the positioned is 0 5kg/sq.cm

DAMPER: - The damper is a power cylinder device; it is used to control the vents of the fluid

lines. It consists of a power cylinder, piston, positioned, I/P converter, CAM and feedback unit.

The o/p of the positioner has two outlets, one enters the top of the cylinder and the other at the

bottom. When air pressure is applied at the top; the piston moves down and closes the vent

mechanically connected to it. When air pressure is applied at the bottom; the piston moves

upward and thus opens the vent. The feedback is transmitted to the control room via the CAM

and feedback unit.

CONTROL VALVES: - Control valves are the most important process control device; it comprises

of I/P converted, positoner, diaphragm and a spring arrangement to introduce restoring torque.There two types of control valve namely air to open and air to close. When air pressure is

applied to the diaphragm it moves towards the direction of the air pressure and the spring

arrangement gives the necessary restoring torque to the diaphragm to maintain balance. A

feedback system is also attached to this valve for sending the feedback to the control unit.

SOLENOID VALVE: - Solenoid valve are used to allow the flow of air either in full flow or in no

flow. It consist of a solenoid that is actuated by a 110V A.C signal, this as a result excites the coil

and open up the valve system. The feedback system comprises of two contacts, one for full open

and other for full close. These are used in purge air ducts.


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-: FURNACE SAFEGUARD SUPERVISORY SYSTEM :-

The furnace safeguard supervisory system (FSSS) is designed to assure the execution of a safe, orderly

operating sequence in the startup and shut down of fuel firing equipment and to prevent errors of

omission and commission in following such a safe operating procedure, the system provides protection,

should there be a malfunction of fuel firing equipments and associated air system. The safety features ofthe system are designed for protection in most common emergency situation.

BASIC FUNCTIONS OF FSSS:-

a) Prevent any fuel firing unless a satisfactory furnace purge sequence has been completed.

b) Prevent startup of individual fuel firing equipment until permissives are satisfied.

c) Monitor and control the proper components during startup and shut down in sequence.

d) Make continued operation of fuel firing equipment until safety interlocks remains satisfied.

e) Provide component status feedback to the operator.

f) Provide flame supervision when fuel firing equipment is in service and initiates fuel trip

upon certain adverse operating condition.

g) Provide master fuel trip when adverse condition exits.

BOILER TRIP CONDITION:-

a) Both I.D fans off.

b) Both FD fans off.

c) Total air flow (secondary+primary)2s delay).

k) Loss of unit critical supply.(24V DC)

l) Loss of 100 V AC(2s Delay) and loss of fire ball.

m) Generator class A trip.

n) Flame failure trip.

o) Both emergency push button pressed.

PURGE PERMISSIVES:-

a) No boiler trip condition persist

b) All HAGs closed

c) All PA fan offd) All feeder off

e) All HONV closed

f) All LONV closed

g) HOTV closed

h) LOTV closed

i) All scanner sensing no flame

j) Auxiliary air damper modulating


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k) Air flow greater than 30% and less than 40% MCR

CORNER TRIP LOGIC: - (HO)

a) Oil guns not engaged

b) Lo selected

c) Ho and isolation valve not open

d) Local maintenance switch

e) Steam atomizing man isolation valve not open

f) Corner start time/scavenge time expired

MILL PERMISIVES: -

a) Mill release available

b) PA fan on greater than 20sec

c) PA general s/o damper open

d) Ignition permit available

e) Coal elevation start permit available

f) Pulverizer/ feeder start permit available

g) Pulverizer outlet temperature not low( > 65 degC)h) Mill both discharge valve open

i) Pulverizer breaker in service

FEEDER PERMISSIVES: -

a) Coal on belt

b) Feeder in remote

c) Pulverizer/feeder start permit

d) Ignition permit

e) Coal elevation start permit

f) Mill outlet temperature not high and not low


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-:APPENDIX:-

ALL THE IMPORTANT CYCLES ARE EXPLAINED BELOW BY SELF EXPLANATORY DIAGRAMS.


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-:BIBLIOGRAPHY:-

1) SIEMENS OS220EA

2) ELECTRICAL AND ELECTRONIC MEASUREMENTATION, A.K SAWHNEY3) POWER PLANT MANAGEMENT SYSTEM

2003 Mtps Project Report

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