my thermal project

8/14/2019 My Thermal Project

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INTRODUCTIONA Thermal Power Stationis a power plant in which the prime mover is steam

driven. Water is heated, turns into steam and spins a steam turbine which drives

an electrical generator. After it passes through the turbine, the steam is condensed

in a condenser; this is known as a Rankine cycle. The greatest variation in the

design of thermal power stations is due to the different fuel sources. Some prefer

to use the term energy centerbecause such facilities convert forms of heat energy

into electrical energy. However, power plant is the most common term in the

United States, whilepower stationprevails in many Commonwealth countries and

especially in the United Kingdom.

Almost all coal, nuclear, geothermal, solar thermal electric, and waste incineration

plants, as well as many natural gas power plants are thermal. Natural gas is

frequently combusted in gas turbines as well as boilers. The waste heat from a gas

turbine can be used to raise steam, in a combined cycle plant that improves overall

efficiency.


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Coal is conveyed (14) from an external stack and ground to a very fine

powder by large metal spheres in the pulverised fuel mill (16). There it is mixed

with preheated air (24) driven by the forced draught fan (20). The hot air-fuel

mixture is forced at high pressure into the boiler where it rapidly ignites. Water ofa high purity flows vertically up the tube-lined walls of the boiler, where it turns

into steam, and is passed to the boiler drum, where steam is separated from any

remaining water. The steam passes through a manifold in the roof of the drum into

the pendant superheater (19) where its temperature and pressure increase rapidly

to around 200 bar and 570C, sufficient to make the tube walls glow a dull red. The

steam is piped to the high pressure turbine (11), the first of a three-stage turbine

process.

A steam governor valve (10) allows for both manual control of the turbine andautomatic set-point following. The steam is exhausted from the high pressure

turbine, and reduced in both pressure and temperature, is returned to the boiler

reheater (21).

The reheated steam is then passed to the intermediate pressure turbine (9), and

from there passed directly to the low pressure turbine set (6). The exiting steam,

now a little above its boiling point, is brought into thermal contact with cold water

(pumped in from the cooling tower) in the condensor (8), where it condenses

rapidly back into water, creating near vacuum-like conditions inside the condensorchest. The condensed water is then passed by a feed pump (7) through a deaerator

(12), and pre-warmed, first in a feed heater (13) powered by steam drawn from the

high pressure set, and then in the economiser (23), before being returned to the

boiler drum. The cooling water from the condensor is sprayed inside a cooling

tower (1), creating a highly visible plume of water vapor, before being pumped

back to the condensor (8) in cooling water cycle.

The three turbine sets are sometimes coupled on the same shaft as the three-

phase electrical generator (5) which generates an intermediate level voltage(typically 20-25 kV). This is stepped up by the unit transformer (4) to a voltage

more suitable for transmission (typically 250-500 kV) and is sent out onto the

three-phase transmission system (3).

Exhaust gas from the boiler is drawn by the induced draft fan (26) through an

electrostatic precipitator (25) and is then vented through the chimney stack (27).


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BRIEF HISTORY OF THE PL NT

A PENOROMIC VEIW OF G.N.D.T.P.

The foundation stone of this prestigious Thermal Plant comprising four units of

110 MW capacities each was laid on 19th,Nov.,1969 the quincentenary year of the

birth of the Great Guru Nanak Dev Ji from whom it gets its present name. the

project was completed in two phases at a total cost of about Rs. 115 crores. The

first unit was commissioned in September 1975, March 1978 and in January 1979

respectively. The commissioning of these units not only bridged the gap between

supply and demand of power in the State but also solved the chronic problem of

the low voltage prevailing in the Malwa region.

Each unit of GNDTP Bathinda, when operated at full capacity is capable of

generating 26.4 lac units of electricity a day. The coal consumption is about 1500 to

1600 MT per day per unit depending upon the quality of coal. The to all daily coal

requirement is about 600 M.T. when all the four units are in operation. The coal is

being received from jhrkhand/ chhattisgarh which are more than 1500 KMs away

from this power station. The project is providing direct employment to about 3000

persons (approximate).

The performance of this power plant has been improving year after year and in

spite of ageing of the units it is being maintained at an appreciably higher level.


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G.N.D.T.P. has won laurels at National levels by winning a number of awards.

Further due to reduction in fuel consumption , the plant has been

continuously winning national awards each year since 1992 when the Govt. of Indiafirst introduced these awards.

It is a matter of pride that all the four units have successfully completed

silver jubilee (25 years) of its operation. At the same time all the units have

outlived their designed life. Various equipment of boilers, turbines and other areas

have largely dereiorated restricting the load on the units to about 95 MWagain

installed capacity of 110 MW. Hence residual life assessment study of the units

have been got carried out through M/s CPRL, Banglore.

Accordingly, Extensive renovation & modernization based on RLA study of all the

four units have been planned to be executed in a phased manner to restore rate

capacity of the plant, increase efficiency, reduce auxiliary consumption and extend

useful life of the plant by another 15-20 years. Each unit of G.N.D.T.P. Bathinda

when operated at full capacity os capable of generating 26.5 lack unit of electricity

a day. The coal consumption is about 1500 to 1600 MT per day per unit depending

upon the quality of coal. The total daily coal requirement is about 6500 M. two

rakes of 58 wagons each when all the four units are in operation. The coal is being

received from Jharkhand / Chattisgarh which are more than 1500 km away fromthis power station. The project is providing direct employment to about 3000

persons.

The performance of this power plant has been improving year after and in spite of

ageing of the units or is being maintained at an appreciably higher level. GNDTP

has won laurels at National level by winning a number of awards.

Under guidance of PAU Ludhiana, various plants have been grown in ash

dyke area to avoid blowing of ash by wind. These shall also help to press ash into acompact layer. A bulldozer has also been pressed into service for this purpose.


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CONTRIBUTION OF THE PL NTGuru Nanak Dev Thermal Plant, Bathinda, in addition to indirect

contribution in various facts of state economy, is also responsible for:-

Narrowing the gap between power demand and power availability of the

state.

Providing employment potentials to thousands of workers.

Covering the backward surrounding area into fully developed Industrial

Township.

Providing additional relief to agricultural pumping sets to meet the

irrigation needs for enhancing the agriculture production.

Reliability and improvement in continuity of supply and system voltage.

Achieving cent percent rural electrification of the state.


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Landmark chieved GNDTP won an award of Rs.3.16 crores from Govt. of India for better

performance in 1983-84.

It achieved a rare distinction of scoring hart rick by wining meritorious

productivity award of Govt. of India, Ministry of Energy for year 1987,

1988 and 1989 due to its better performance.

It again won meritorious productivity award during the year 1992-93

& 1993-94 and has become entitled for the year 1996-97 for better

performance. It also won award for reduction in fuel oil consumption under Govt. of

India incentive scheme year from 1992-97 (award money for 1992,

1993 & 1994 already released for 1995, 1996 & 1997 under the

consideration of Govt. of India)

G.N.D.T.P. has achieved a generation of 2724240 LUs (at a PLf of

70.7%) &registering a oil consumption as low as 1.76 ml/Kwh during

the year 1993-94 has broken all previous records of performance since

the inception of plant.


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PL NT S LIENT FE TURESPROJECT AREA:-

Power plant 238 acres

Ash disposal 845

Lake 180

Residential colony 285

Marshalling yard 256Total area 1804

TOTAL COST:- Rs. 115 crores

STATION CAPACITY:- four units of 110MW. Each

BOILER:-

Manufacturers B.H.E.L.

Maximum continuous rating (M.C.R.) 375 T/hr.

Superheater outlet pressure 139 kg/cm

Reheater outlet pressure 33.8 kg/cm

Final superheater/reheater temperature 540C

Feed water temperature 240C

Efficiency 86%

Coal consumption per day per unit 1400tones (Approximate)

STEAM TURBINE:-


Rated output 110 MW.

Rated speed 3000 r.p.m.


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Number of cylinders three

Rated pressure 130 kg/cm

Rated temperature 535C

Condenser vacuum 0.9 kg/cm

GENERATOR:-


Rated output

(Unit- 1 & 2) 125000KVA

(Unit -3 & 4) 137000KVA

Generator voltage 11000 volts

Rated phase current

(unit1 & 2) 6560 Amps.

(unit3 & 4) 7220 Amps.

Generator cooling hydrogen

BOILER FEED PUMPS:-

Number per unit two of 100% duty each

Type centrifugal

Rated discharge 445 T/hr.

Discharge head 1960 MWC.

Speed 4500 r.p.m.

CIRCULATING WATER PUMPS:-

Numbers for two units five of 50% duty each

Type mixed flow

Rated discharge 8600 T/hr.

Discharge head 24 MWC.


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COOLING TOWERS:-

Numbers four

Water cooled 18000 T/hr.

Cooling range 10C

Height 120/122 metres

COAL PULVERISING MILLS:-

Numbers three per unit

Type drum-ball

Rated output 27 T/hr.

Coal bunkers 16 per unit

RATING OF 6.6 KV AUXILLIARY MOTORS:-

Coal mill 630 KW

Vapour fan 320 KW

C.W. Fan 800/746 KW

Coal crusher 520 KW

Primary air fan 320 KW

Forced draught fan 320 KW

Boiler feed pump 3500 KW

Induced draught fan 900/1000 KW

Condensate pump 175 KW


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BASICS OF THERMAL PLANT

Thermodynamics is the main subject of Thermal Engineering. It deals

with the behavior of gases and vapors, when they are subjected to varying

temperatures and pressure. In a thermal power plant, heat energy of the steam

is converted to mechanical energy of the turbine, which is further converted to

electrical energy with the help of a generator. The simple circuit of thermal

plant can be drawn as below:-

Some of the definitions dealing with the thermodynamics are as below:-

GAS:- A gas is the name given to the state of any substance of which the

evaporation from the liquid state is complete. For example Hydrogen, Oxygen and

air etc.

VAPOUR:-A vapor may be defined as a partially evaporated liquid and consists of

the pure gas state along with particles of liquid in suspension. It does not behave in


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the same way as the gas, as the substance is further liable to the evaporation. The

laws of gases do not apply to vapors. When a vapor becomes completely

evaporated, it is said to be dry and any further heating of a dry vapor is termed as

super heating. Once a vapor is superheated it is approx. behaves as a gas.

HEATING OF A GAS:- A gas may be heated while either its volume is kept

constant or its pressure is kept constant, when the volume is kept constant, the

temperature, pressure will increase as the heat is supplied to a gas. But there will be

no work done by the gas as there is no change in volume. But when the gas is heated

at constant pressure then the volume increases and some work is done by the gas in

expanding.

Work = pressure xchange in volume

INTERNAL ENERGY OF GAS:-The internal energy of a gas is the heat energy

stored in the gas. It is quantity of heat. If the quantity of steam is applied to a gas,

the temperature of gas may increase or its volume may increase thus doing external

work or it may do both, the result will depend upon certain set of conditions under

which heat is supplied to gas. If this heating is accompanied by a rise of

temperature, the gas will increase its internal energy. This means that some of the

heat supplied has been stored in gas in the form of heat energy. Thus producing the

rise of temperature the gas will have increased its internal energy. This means that

some of the heat supplied has been stored in the form of heat energy, remaining is

given out by gas as the form of external work as gas increased its volume. The

increase in heat energy stored in the gas due to rise of temperature is called the

increase of internal energy.


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LAW OF CONSERVATION OF ENERGY:-

Total heat supplied to a gas must be equal to the increase of internal

energy plus any external work done by the gas in expanding.

H = total heat supplied to gas

E = increase in internal energy

W = external work done by gas

Then H = W + E

ISOTHERMAL EXPANSION:- Heat can be supplied to a gas keeping its

temperature constant. In this case the gas will expand doing external work equal to

the amount of heat supplied. This type of expansion is called Isothermal Expansion.

ADIABATIC EXPANSION:-When a gas expands, doing external work in such a

manner that no heat is supplied or rejected during the expansion. Such an expansion

is called adiabatic expansion.

ENTHALPY :-The total heat of substance is known as its enthalpy.

BASIC TYPE OF STEAM POWER PLANT :- The conversion of heat energy of

organic or nuclear fuel into mechanical energy with the aid of steam is carried out in

steam power plant. A diagrammatic view of the simplest steam power plant is

shown on next page :-


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METHODS OF INCREASING EFFICIENCY:-

Raising the initial steam pressure:-By increasing the initial pressure at turbine

inlet, the enthalpy drop (H1H2) can be increased. Thereby increase in thermal

efficiency of Rankine cycle. However it must be mentioned that an increase in the

initial steam pressure results in increase in the wetness of the steam at the end of

expansion. The drops of liquid of steam can appearing in the steam at the last stage

of the turbine cause erosion of blades and reduce overall efficiency of turbine.

In order to avoid this increase in steam wetness above the tolerated value, an

increased temperature of the superheated steam as well as reheating may be

employed.

Reheating:-

Reheating consists of subjecting steam to repeated super heating, after it

has expanded in the first cylinder of the turbine, at originally constant pressure in

the reheaters to original temperature, then the steam is directed into the second

cylinder of the turbine T2, where the steam expands and goes to the condenser.

Reheating increases dryness fraction of steam. It also results in the thermal

efficiency of the cycle.


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Raising the temperature of superheating:- By raising the temperature of

superheated steam at constant pressure, the heat drop (H1-H2) increases. As a result

efficiency increases. Increasing the temperature of superheated steam also increases

the dryness factor. In modern steam power plants the temperature of superheating is

limited. By the heat resistant properties of the metal used.

Increasing the vacuum at condenser or reducing pressure at final:-A reduction

in the final pressure increases the heat drop (H1-H2) which results in the increase in

the thermal efficiency of the cycle.

Regenerative feed heat cycle:- In this system, the steam is fed from the turbine at

certain points during its expansion and is utilized for preheating the feed water

supplied to the boiler. At certain sections of turbine a small quantity of wet steam is

drawn from the turbine. This steam is circulated around the feed water pipe leading

from the hot well to boiler. The relatively cold water causes this steam to

condensate. The heat thus lost by the steam being is transferred to the feed water;

the condensed steam then drains into the hot well.

The net effect of this process is to supply the boiler with hotter water while a

small amount of work is lost by the turbine. There is a slight increase in efficiency

due to this process, but there efficiency depends upon following factors:-

Steam pressure

Degree of superheat in steam

Reheat/nonreheat

Vacuum in condenser

Regenerative/ non regenerative cycle


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WORKING OF THERMAL PLANT

Coal received from collieries in the rail wagon is mechanically unloaded by

Wagon Tippler and carried by belt Conveyor System Boiler Raw Coal Bunkers after

crushing in the coal crusher. The crushed coal when not required for Raw Coal

Bunker is carried to the coal storage area through belt conveyor. The raw coal feeder

regulates the quantity of coal from coal bunker to the coal mill, where the coal is

pulverized to a fine powder. The pulverized coal is then sucked by the vapour fan

and finally stored in pulverized coal bunkers. The pulverized coal is then pushed toboiler furnace with the help of hot air steam supplied by primary air fan. The coal

being in pulverized state gets burnt immediately in the boiler furnace, which is

comprised of water tube wall all around through which water circulates. The water

gets converted into steam by heat released by the combustion of fuel in the furnace.

The air required for the combustion if coal is supplied by forced draught fan. This

air is however heated by the outgoing flue gases in the air heaters before entering

the furnace.

The products of combustion in the furnace are the flue gases and the ash.

About 20% of the ash falls in the bottom ash hopper of the boiler and is periodically

removed mechanically. The remaining ash carried by the flue gases, is separated in

the electrostatic precipitators and further disposed off in the ash damping area. The

cleaner flue gases are let off to atmosphere through the chimney by induced draught

fan.

The chemically treated water running through the water walls of boiler

furnace gets evaporated at high temperature into steam by absorption of furnace

heat. The steam is further heated in the super heater. The dry steam at high

temperature is then led to the turbine comprising of three cylinders. The thermal


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energy of this steam is utilized in turbine for rotating its shaft at high speed. The

steam discharged from high pressure (H.P.) turbine is returned to boiler reheater for

heating it once again before passing it into the medium pressure (M.P.) turbine. The

steam is then let to the coupled to turbine shaft is the rotor of the generator, which

produces electricity. The power from the generator is pumped into power grid

system through the generator transformer by stepping up the voltage.

The steam after doing the useful work in turbine is condensed to water in the

condenser for recycling in the boiler. The water is pumped to deaerator from the

condenser by the condensate extraction pumps after being heated in the low pressure

heater (L.P.H)from the deaerator, a hot water storage tank. The boiler feed pump

discharge feed water to boiler at the economizer by the hot flue gases leaving the

boiler, before entering the boiler drum to which the water walls and super heater of

boiler are connected.

The condenser is having a large number of brass tubes through which the cold

water is circulated continuously for condensing the steam passing out sides the

surface of the brass tubes, which has discharged down by circulating it through the

cooling tower shell. The natural draught of cold air is created in the cooling tower,

cools the water fall in the sump and is then recirculated by circulating water pumps

to the condenser.


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COAL HANDLING PLANT

(CHP)The G.N.D.T.P. units are primarily coal-fired units and the coal consumption

at maximum continuous rating (M.C.R.) per unit is about 58 T/Hr. the coal used at

G.N.D.T.P. is of bituminous and sub-bituminous type and this is received from

some collieries of M.P. and Bihar. The designed composition of coal is as below:-

Type Bituminous Coal

Net calorific value 4300 kcal/kg

Moisture content in coal 10%

Ash content 30%

Volatile matter in combustibles 24%

Grind ability index 50 Hard Groove

The coal handling plant at G.N.D.T.P. has been supplied and erected by M/s

Elecon Engineering Company Limited, Vallabh Vidya Nagar, Gugarat. Coal is

transported from the coal mines to the plant site by Railways. Generally, the raw

coal comes by railway wagons of either eight wheels weighing about 75 to 80 tones

each or four wheels weighing about 35 to 40 tones each. The loaded wagon rake is

brought by railways main line loco and left on one of the loaded wagon tracks in the

power station marshalling yard. The main line loco escapes through the engine

track. The station marshalling yard is provided with 8 tracks. The arrangement ofthe tracks in the marshalling yard is as follows:-

DESTINATION NO. OF TRACKS

Loaded wagons receiving tracks Four

Empty wagon standing tracks Three


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Engine escape tracks One.

The marshalling yard has a shunting neck at the west side. There is a sick

line also. The yard is connected to the mainline (to Hindumal Kot) and also to

wagon tippler tracks. There are five numbers of shunting locos for pushing the

wagons to the tippler and taking the empty wagons back. Three of the locos are of

Telco made and two are of Suri and Nayer make each fitted with 150 H.P. (2 X 75

H.P.) diesel engines.

UNLOADING OF COAL:-

In order to unload coal from the wagons, two Rotaside Tipplers of Elecon

make are provided. Each is capable of unloading 12 open type of wagons per hour.

Normally one tippler will be in operation while the other will be standby. The

loaded wagons are brought to the tippler side by the loco shunters. Then with the

help of inhaul beetle one wagon is brought on the tippler table. The wagon is then

tilted upside down and emptied in the hopper down below. The emptied wagon

comes back to the tippler table and the outhaul beetle handles the empty wagons on

the discharge side of the tippler. The tippler is equipped with the integral

weighbridge machine. This machine consists of a set of weighing levers centrally

disposed relative to tippler. The rail platform rests on the weighing girders and free

from rest of the tippler when the wagon is being weighed. After weighing the loaded

wagons is tipped and returned empty to the weighing girders and again weighed.

Thus the difference of the gross weight and the tare weight gives the weight of the

wagon contents. The tipplers are run by motors of 80 H.P. each through gears only.


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WAGON TIPPLER

The tippler is designed to work on the following cycle of operation:-

Tipping 90 seconds

Pause 5-12 seconds

Return 90 secondS

Weighing 30 seconds

Total 215-222 seconds

Allowing 85 seconds for wagon changing it will be seen that 12 eight-wheel wagons

or 24 four-wheel wagons per hours can be tipped. However since the coal carrying

capacity is 500 tones per hour load of 12 wagons comes to 8 to 9 per hour.

DUST TRAPPING SYSTEM:-

The tippler is also provided with the dust trapping systems by which the dust

nuisance will be minimized. As the tippler rotates, a normally closed hopper valve


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opens automatically and the discharged material passes through it into the hopper

with its dust-setting chamber, there is an air valve of large area, which opens,

simultaneously with the hopper valve. The object of this air valve is to blow back

through the hopper valve into the tipping chamber, which must occur if, the settling

chamber were closed, it being remembered that a large wagon contains some 240

cubic feet of material and that this volume of dust air would be forced back at each

tip if the hopper chamber were a closed bottle. The air valve and the hopper valve

are shut immediately on reversal of the tippler and are kept shut at all times except

during the actual discharge. The hopper valve is operated by a motor of 10 H.P., 415

Volts and the air valve is operated by electro-hydraulic thruster. Inlet valve consists

of large number of plates sliding under the wagon tippler grating. Coal in the wagon

tippler hopper forms the heap and as such obstructs the movement of sliding valve

and damaging the plates. The inlet and outlet valves have therefore been bypassed.

The unloaded material falls into the wagon tippler hopper (common to both

tipplers) having a capacity of 210 tones. The hopper has been provided with a

grating of 300mm X 300mm size at the top so as to large size boulders getting into

the coal stream. There is also a provision of unloading the wagons manually into the

MANUALLY UNLOADED HOPPER of 110 tones capacity. Manually unloading

will be restored to while unloading coal from sick wagons or closed wagons.

CONVEYING SYSTEM:-

The coal received in the tippler hopper is fed to either or both the conveyors

no. 2A and 2B through water discharging mouthpieces integral with the

electromagnetic vibrating feeder 1A and 2B and flap gates. Either or both conveyors

2A and 2B running underground will also be fed from manual unloading

hopper through mouthpieces integral with rack and pinion operated gates,

electromagnetic vibrating feeders 3A and 3B and flap gates.


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CIRCUIT FOR COAL HANDLING PLANT :-

Coal will also be fed either of the conveyors 2A or 2B from either of

conveyors 9A or 9B running completely underground, which in turn receive coal

from reclaim hopper from coal storage area through mouthpieces integral with the

rack and pinion gates, electromagnetic feeders 8A and 8B and flap gates.

The conveyors 2A and 2B will feed coal to either or both the conveyors 4A

and 4B at the underground transfer point through flap gate. The inclined conveyors


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4A and 4B, which are partially underground will feed coal via magnetic pulleys to

either or both crusher A and B through electromagnet vibrating feeder 10A and 10B,

the iron particles separated by magnetic pulleys 4A and 4B are collected on the

crusher house ground floor through a long chute provided in the crusher house.

The crushed coal is fed to either of the forward inclined conveyors 5A and 5B

or to either of the stock though inclined conveyors 7A or 7B, through flap gates. The

belt propelled tripper to deliver coal to the desired bunker. The bunker opening

through which the tripper feeds the coal is equipped with a sealing belt in order to

the dust nuisance.

The conveyors 7A and 7B deliver coal to stockpile through TELESCOPIC

CHUTE. One-conveyor 5A and 5B automatic belt weighers are provided for

weighing the coal transported to bunkers. To meet the daily requirement of the coal,

only one stream of the conveyors and one crusher of 500 tones per hour capacity

will be normally opening and other set will be standby. The detailed diagram and

the drives etc. are attached.

BELT CONVEYORS:-

Belt conveyors in the coal handling system are occupying an outstanding

position. In addition to their primary use, as a mean of transporting coal from

unloading stations and/or from coal yard to raw coal bunkers they also perform

numerous other functions such as weighing, stocking and removing of tramp iron

particles/pieces. The belting is of rubber and canvass type having suitable number of

skim-coated piles. The details of belts of various conveyors are given at next page.

S.No. Convey

or

Approx.Length(m

m)

Width(mm)

No. ofPiles

Thickness

(mm)

H.P. ofdriving

motor


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1. 2A,2B 81500 1050/10

67

7 19 40

2. 4A,4B 183150 1050/10

67

7 19 20

3. 5A,5B 182400 1050/10

67

6 19 20

4. 6A,6B 105400 900/914 5 17 40

5. 7A,7B 222500 900/914 5 13 60

6. 9A,9B 115000 900/914 5 13 40

The belting is of Dunlop/Goodyear/Hilton make. The capacity of each belt is

500-tones/hr. the belt speed is approx. 2.5 m/sec. The belts run on idlers spaced at

convenient distances. At the end there are end pulleys and on one end are driven by

electric motors. There are three rollers on each carrying idler and one roller on each

return idler. At the coal transfer points impact, idlers have been provided. To align

the belt, self-aligning, carrying and return idlers have been provided at about 15

meters from each terminal or bend pulley and approx. 24 meters thereafter. Grease

nipples have been provided with all the idlers. The idlers near the suspension

magnet are of non-magnetic material.

Automatic gravity operated tensioning arrangement has been provided for all

conveyors, which takes up stretch in each belt while starting under load giving a

constant slack side tension. The tensioning arrangement comprises of take up pulley,

bend pulley, weight box. Suitable sliding gear and counter weights.

For cleaning upper and internal surfaces of the belt, for increasing the belt

conveyor components life, two belt cleaners with each conveyor have been

provided, one for cleaning upper part of the belt called external belt cleaner and


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other for cleaning the internal surface of the belt called internal belt cleaner. All the

conveyors have been accommodated on frame works comprising of gantries,

trestles, belt covering and walkways etc. outdoor portions of all the conveyors have

been provided with belt covering of galvanized corrugated sheets and rolled sheets

sections. Grating walkways of about 120mm width with suitable handrails have

been provided for all the conveyors for operation and maintenance purposes. Pull

wire switches are mounted on the walkway side of each conveyor at about 30m

intervals. These switches are connected by a pull wire, which is easily accessible

from any position and runs along the entire length of the conveyor. In case of

emergency, operation pulls the chain and stops the system.

The run of the conveyor belt is monitored by Belt Way Switches, which cut

off the main circuit in the event of an eccentric run of the belt.

Zero speed switches are also named as the Belt Sequence Switches have been

provided on the return roller of the belt for the correct operation of the conveyor

belt. The rotation of the roller is transmitted by a shaft to the actual monitoring

element with a micro switch. The zero speed switch provides the following

functions:

The switch operates in conjunction with a time delay to determine whether a

conveyor belt reaches its normal speed within a specified period. The subsequent

drive can be switched only after the monitor belt had reached its normal speed. The

switch cuts of the drive, if it has not run up to the normal speed within a certain

time.

The switch trips the motor contractor in case of excessive fall of

speed/breaking of belt.


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MAGNETIC PULLEYS:-

On belt conveyor no. 4A and 4B, there have been provided high intensity

electromagnetic pulleys for separating out tramp iron particles/pieces from the main

stream of coal conveying. D.C. supply for the magnet is taken on 415 volt, 3 phase,

50 cycles A.C. supply system.

In addition to above high intensity suspension type electromagnets have also

been provided on belt conveyors 4A and 4B for separating out tramp iron

pieces/particles.

RECLAIMING:-

If the receipt of coal on any day more than the requirement of the boilers, the

balanced material will be stocked via conveyor 7Aand 7B and through telescopic

chute fitted at the end of the conveyor. At the end of the chute one tele level switch

is provided, which automatically lifts the telescopic chute to a predetermined height

every time. The tele level switch is actuated by the coal pile. When the telescopic

chute reaches maximum height during operation, which will be cut off by limit,

switch and stop the conveying system. When the pile under the telescopic chute is

cleared, the telescopic chute can be independently lower manually by push buttons.

There are five bulldozers to spread and compact the coal pile. Bulldozers of

Bharat Earth Movers Limited Make are fitted with 250 H.P. diesel engines. Each

bulldozer is able to spread the crushed coal at the rate of 250 tones/hr. over a load

distance of 60m the coal can be stacked to a height of 6m the stockpile stores coal

for about 45 days for four units with an annual load factor of 0.66.

Whenever coal is to be reclaimed the bulldozers are employed to push the

coal in the reclaim hopper having a capacity of 110 tones. The coal from the reclaim

hopper is fed either 9A or 9B belt conveyor through vibratory feeders 8A and 8B.


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CRUSHER HOUSE:-

The crusher house accommodates the discharge ends of the conveyor 4A, 4B

receiving ends of conveyor 5A, 5B and conveyor 7A and 7B, two crushers, vibrating

feeders and necessary chute work. There are two crushers each driven by 700H.P.

electric motor, 3 phase, 50 cycles and 6.6 kV supply. The maximum size of the

crushed coal is 10mm. The capacity of each crusher is 500 tones/hr. one crusher

works at a time and the other is standby. From the crusher the coal can be fed either

to the conveyors 5A, 5B or 7A, 7B by adjusting the flap provided for this purpose.

There is built in arrangement of bypassing the crusher by which the coal can be fed

directly to the conveyors bypassing crushe.

COAL MILLING:-

Since G.N.D.T.P. units are primarily coal-fired units so each boiler is

provided with three 50% capacity identical closed milling circuits to pulverize the

raw coal, which is received from the coal conveying system after coal crusher

before it is fired in the furnace. The necessity of pulverizing the coal is to ensure the

maximum possible combustion in the furnace. The milling units have been supplied

by B.H.E.L.


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COAL MILL

The raw coal of maximum size 10-20mm is pulverized in the milling

circuit and the output from the mill is coal of fitness 20-24% remainder

with sieve R-90. Milling circuit mainly consists of the following main

constituents:-

1. Raw coal bunker

2. Raw coal chain feeder

3. Drum mill

4. Classifier


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5. Cyclone separator

6. Vapour fan

7. Pulverized coal bunker

8. Worm conveyor

The detail of each part is given below:-

RAW COAL BUNKER:-

Each of three raw coal bunkers is fabricated from the sheet metal and is well

stiffened all around. The storage capacity of each raw coal bunker is about 500

tones. There are four outlet gates with each bunker. The gates are electrically

operated from site. In case of failure of the electric motors the gate can be hand

operated from site. At a time only one gate opening is suffices but should be

changed so that there is no pilling within the bunker.

RAW COAL CHAIN FEEDER:-

The raw coal chain feeder transports coal from raw coal bunker to the inlet

chute leading to the pulverized/coal mills. There is a double link chain of high

tensile strength steel, which moves on wheels and sweeps the raw coal falling over

the top of the raw coal chute of the mill. The height of the coal bed in the chain

feeder can be adjusted manually by means of lever operated damper. The maximum

and minimum


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heights of the coal bed are 200mm and 120mm respectively. The signaling

equipment indicates the absence of coal flow in the feeder, which is annunciated in

the unit control board (U.C.B.). The main shaft on the driving end is connected to

the driving unit, consisting of variator, a gear box and a motor all mounted as asingle unit. The chain wheel on the driving end shaft is provided with a shear pin,

which will shear off and disconnect the driving mechanism if there is any overload

on the feeder. The speed of the chain feeder is regulated automatically/remotely by

actuating the control spindle of the variator through a servomotor. A pump for

circulating the oil in the gear box of variator is an integral part of variator driven by

a separator motor. Some of the technical data about the raw coal chain feeder is

given here:-

1. Output of the chain feeder 10-45 tonnes/hr.

2. Speed variations 0.0503-0.151m/sec.

3. Main motor 7.5kW, 415V, 50Hz.


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4. Oil pump motor 0.05kW, 220V

5. Operating motor of each gate 3HP, 415V and 50Hz.

DRUM MILL:-

Each mill consists of single compartment drum, bearings driving motor, coal

inlet and discharge piping, ball change and lubricating equipment for mill bearings.

Mill drum is fabricated from thick steel plates and is supported on to the anti-friction

bearings. The mill is driven by an electric motor of capacity 630kW, 990 rpm,

6.6kV through a reduction gear, which reduces the speed to 17.5 rpm. The ball

charge for the mill consists of the three different sizes of forged steel balls detailed

as below. The capacity of each mill is 27 T/hr. in case of unit 1 & 2 and 28 T/hr.

1. 40mm diameter 22500 kg

2. 50mm diameter 20000kg

3. 60mm diameter 10000kg

4. Total Ball Charge 52500kg


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During operation only 60mm diameter balls are added is approx. 500 kg per

week and the guiding factor is the amperage of the coal mill, normally it should be

66-ampere approx. at full load and when it falls below the above value ball charging

of the mill is carried out. Lubricating system consists of the oil tank, gear pump, oil

cooler and base frame to mount all these equipments. Gear pump is driven by an

electric motor of rating 1 H.P., 415 V, 1440 rpm. Suction side of the gear pump is

connected to the tube oil tank and the delivery side is connected to inlet of the oil

cooler and after cooling oil goes to the bearings. The oil from the bearings is cooled

to the required temperature in the cooler by the means of plant bearing cooler water.

CLASSIFIER:-

The classifier is fabricated from the steel plates. It is an equipment that

separates fine pulverized coal from the coarser pieces. The pulverized coal along

with the carrying as well as drying medium (flue gas) strikes the impact plate in the

classifier and the coarser pieces get separated due to the change in the direction of

flow and go back to mill. The stream then passes to the outlet branch of the

classifier through an adjustable telescopic tube. At the outlet adjustable vanes are

provided to change the size of coal when required.

CYCLONE SEPARATOR:-

The centrifugal type cyclone separator consists of two cyclones made up of

welded sheets. It is equipment in the milling plant, which serves for separating the

pulverized coal from the vapours i.e. carrying medium. The pulverized coal gets

stored in the pulverized coal bunkers and vapours go to suction of vapour fan. At the

bottom of the cyclone separator a rotary valve (Turnikete) is provided to transport

coal from cyclone separator to P.C. bunker on the worm conveyor as the case may

be.


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VAPOUR FAN:-

Pulverized coal bunker is welded from thick steel sheets and has a capacity of

4 hours coal consumption at maximum continuous rating of the boiler. The whole

bunker is insulated externally. The carbon-dioxide blanketing system has been

provided in the P.C. bunker to prevent fire hazards inside the bunker. The while

storage bunker is divide into four parts namely A, B C & D. Further four coal

feeders are taken out from each bunker leading to each corner of the furnace.

CRUSHING OF COAL:-

When coal reaches the plant, normal size of coal is about 500mm. After

unloading the coal from the rake is fed to primary crusher, which reduces the size to

120mm. Then coal is fed to secondary crusher which reduces the size to 25mm and

this coal goes to bunker with the help of conveyor belt from where coal finally goes

to coal mill where coal is transferred in form of pulverized coal. The coal is heated

with the help of hot primary air. We maintain the temperature of about 70 C in coal

mill. This temperature is maintained with the help of cold air and a hot air damper.

USE OF OIL:-

Before the coal reaches the furnace, we preheat the furnace in order to remove

the moisture and raise the temperature of furnace, so that coal can catch fire easily

without any delay. This preheating of furnace is done with the help of oil. With

burning of oil, we maintain the temperature of furnace at 350C. we cut the oil

supply after 350C because oil is very costly. Source of oil for G.N.D.T.P., Bathinda

is Mathura Oil Refinery. Other use of oil is in bearing system for cooling. There are

large number of bearings for plant. For example bearing system of turbine. These

bearings get heated upto high temperature, which is dangerous. So we cool the

bearing by circulating water in bearing.


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COAL FEEDING AND COAL MILL:-

From the coal handling plant, coal comes in two belts namely 5A and 5B and

then by belts 6A and 6B coal comes in bunkers. Bunker capacity is 300 tonnes.

Number of outlets of bunker is three. First gate is opened for one hour and second

and then third. If open the one gate for long time, then coal will stop going to mill.

That is why we open the gate turn by turn.

RAW COAL CHAIN FEEDER:-

Raw coal chain feeder is just below raw coal bunker. It is a sliding chain

which feed the coal to mill. We can change the quantity of coal which is fed to mill

in two ways.

By changing the speed of chain

By changing the depth of coal in chain

Speed of chain can be changed by adding a gear system to motor. We connect

the gear system with motor with a pin called shear pin. The prevent the overloading

of motor because when the coal quantity of coal on chain is greater than its capacity

then the pin will break and prevent the pin from overloading. Speed of Raw Coal

chain is 2 to 6/sec.

COAL MILL:-

These are mainly of two types:-

i) Ball Mills

ii) Bowl Mills

Ball Mills:- In Ball Mills there are steel balls which are revolving in horizontal

cylindrical drum. These balls are free from any shaft and balls are touching with

each other and with internal body of drum. These types of mills are at Bathinda

Thermal Plant. On the other hand, bowl mills part of the mill contain drive system

i.e. it contains 6.6 kV electric motor and gear system which translates the revolution


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about horizontal axis to revolve about vertical axis. The revolving vertical axis

contains a bowl about the driving system. This bowl is fixed with driving and

revolving with shaft. There are also three rollers which are suspended at some

inclination, so that there is a gap of few mm between roller surface. These rollers are

free to rotate about the axis.


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TURBINE

Turbine is a prime mover for the Generator in the power plant. In steam

turbine, the potential energy of steam is transformed into kinetic energy and later in

its turn is transformed into the mechanical energy of the rotation of the turbine shaft.

The common types of turbines are:- IMPULSE TURBINE:-In this type of turbine, steam expands in thenozzles and its pressure does not alter as it moves over the blades.

REACTION TURBINE:- In this type of turbine, the steam expandscontinuously as it passes over the blades and thus there is a gradual fall in

pressure during expansion.

IMPULSE TURBINE REACTION TURBINE

Different types of steam turbines are used in Thermal Power Plant but the

ones which are used at G.N.D.T.P. are categorized as follows:-


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Sr. No. Type of Turbine Turbines at G.N.D.T.P.

1. Horizontal/Vertical Horizontal

2. Single/Multi-cylinder Multi-cylinder (3-cylinder)

3. Impulse/Reaction Impulse

4. Condensing/Non-condensing Condensing

5. Reheat/Non-reheat Reheat

6. Regenerative/Non- Regenerative With bypass (ST-1)

7. With bypass/Without bypass Without bypass (ST-2)

MAIN TECHNICAL DATA

a) The basic parameters:

Rated output measured at Terminal of the generator. 110.000KW

Economical output. 95.000KW

Rated speed. 3.000RPM

Rated temp. of stearn just before the stop valve. 535C

Max Temp. of steam before the stop valve. 545C

Rated pressure of steam before the MP casing. 31.63C

Max. pressure of steam before the MP casing 35C

Rated temp. of steam before the MP casing. 535C

Max. temp. of steam before the MP casing. 545C


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b) System of turbine:

4 Governing valves +2 interceptor valves HP cylinder- 2 Row Curtis wheel +8

moving wheels.

Wt. Of HP rotor approx. 5,500 Kg.

MP cylinder - 12 Moving wheels.

Wt. Of MP rotor. Approx. 11,000 Kg.

LP cylinder - 4 Moving wheels of double flow design.

Wt. Of MP rotor approx. 24,000 Kg.

Direction of the turbine rotation - To the right, when looking at the turbine from the

front bearing pedestal.

TURBINE ASSEMBLY WITH LOWER CASING

TURBINE ACCESSORIES AND AUXILIARIES:

The following are turbine accessories and auxiliaries:

1. Surface condensers.

2. Steam jet air ejector

3. LP and HP heaters.


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4. Chimney steam condenser.

5. Gland stearn condenser.

6. Oil purifier of centrifuge.

7. Clean oil pumps with clean oil tank.

8. Dirty oil pumps with dirty oil tank.

9. Auxiliary oil pump with aux. Oil tank.

10. Starting oil pumps.

11. Emergency oil pumps (AC and DC).

12. Jacking oil pumping.

13. Bearing or turning gear.

1. SURFACE CONDENSERS

Two no. surface condensers are used for condensing the steam which has

worked in the turbine. The coolant for condensing the steam is circulating water,

which is inside the condenser brass tubes, and steam is outside.

TECHNICAL DATA OF EACH CONDENSER:

Cooling area 3330 m2

No. of brass tubes 6000

Circulating water required for each condenser

7500T/Hr.

Circulating water required for both condenser2x7500T/Hr. 15000T/Hr.

Allowable difference between inlet & outlet C.W. water 10C Temp.


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Vacuum in the condenser 0.90 Kg/cm2

2. STEAM JET AIR EJECTORS

Starting ejector or hogger is used for quick evacuation of the turbo set during

starting whereas main steam jet air ejector (Duplex Type) is used to maintain the

vacuum in the condenser. Steam Jet Air Ejector works on the principle of venture

with steam working media to eject air from the condenser.

3. STEAM HEATERS

In regenerative system there is a stream of 5 LP heater, one desecrator and 2

HP heaters. All LP and HP heaters are of surface type i.e. condensate of feed water

is inside the heaters tubes and steam extractions are outside the heater tubes in the

heater shells. LP heaters are of single flow type whereas HP heaters are of double

flow type i.e. feed water is flowing twice through the HP heaters in order to extract

total HP latent heat and super heat of steam going into HP heaters, desecrator is a

contact type heater in which steam and condensate come in direct contact with each

other.

Details of Steam Extraction:

Steam into HP heater NO. 2 is from cold reheat line.

Steam into HP heater NO.1 is from MP turbine, LPH- 4 LPH- 5 is from MP casing

at differently steam pressures and temperatures.

4. CHIMNEY STEAM AND GLAND STEAM CONDENSERS

There are the additional two heater stages provided in the regeneration system

of the turbine for heating the condensate flowing through it. Steam leak offs from

the turbine a gland is used for heating the condensate in these heaters.

5. STARTING OIL PUMPS AND ARRING GEAR S.O.P supply necessary

turbine oil during starting of the turbine and up to turbine speed of 2930 RPM till


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the main oil pump mounted on the turbine rotor at the HP extension.takes manually

in order to provide lub. Oil for turbo set.

Emergency pumps (AC & DC) are meant to start on auto when turbine trips

and lub. Oil pressure falls in order to provide lubrication of turbine and generator

bearings.

6. JACKING OIL PUMP AND ARRING GEAR

Jacking oil pump is used in order to lift the turbine rotor before it is put on

barring gear jacking oil pump takes suction from the turbine lub. Oil system and

provide a thin film of oil for lifting the rotor. Barring gear motor used to rotate the

turbine rotor at 62 RPM after engaging the rotor with the gear during starting and

stopping of the turbine.

7. CIRCULATING WATER PUMPS

Two nos. circulating water pumps provide for each unit circulate water

@17200 tonnes per hour in a closer cycle comprising of turbine condenser and

cooling tower. An additional circulating water pump provide, serves as a stand by

for two units. The water requirement for bearingcooling of all plant auxiliaries is

also catered by these pumps.

SECTION - 1

FUNCTION AND TYPES OF STEAM TURBINE

FUNCTION OF STEAM TURBINE

Steam turbine is a from of heat engine in which the available heat energy in

from of steam is converted into kinetic energy, to rotate the turbine rotor, byexpansion of steam in a suitable shaped nozzle, the pressure on the blades causing

rotary motion is


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purely dynamical and is due solely to the change of momentum of the steam jet

during its passage through these blades.

TYPES OF STEAM TURBINE:-

The steam turbines are broadly classified into three groups depending on the

conditions of operations of the steam on the rotor blades.

1) Impulse Type

This is again subdivided into:-

a) Simple Impulse

b) Compound Impulse

(Pressure, Velocity and Pressure & Velocity compounded)

c) Combined Impulse

2) Reaction Type

This is again grouped into:-

a) Axial Flow

b) Radial flow

c) Mixed flow

3) Impulse reaction Type


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IMPULSE TURBINES:-

In an impulse turbine the potential energy in the steam due to pressure and

superheat is converted into kinetic energy in the form of weight and velocity by

expanding it in suitably shaped nozzles. The whole of the expansion takes place in

the fixed nozzles. The steam pressure at the inlet and outlet edges of the rotor blades

are equal as there is no expansion in the rotor bicycles. The steam impinges on the

wheel I blades causing the wheels to rotate. The expansion is carried out in stages

referred to as Pressure, Stages the commonest type of impulse turbine is the

Delaval turbine.

REACTION TURBINE

In the type of turbines the steam expands in both the stationary and moving

blades. So, the steam pressure, at inlet to the moving blades is greater than the exit

pressure. The term reactions is strictly not correct as no turbine practice works on

pure reaction principle. The action on the balding is both impulse an reaction.

The steam turbine installed is a 3 cylinder,(HP r1v1p and LP r

condensing, reheat cycle type with 8 non~regulated extractions for regenerative

heating pf the boiler feed water. The cross section through a typical 110 MV1 steam

turbine.

The high-pressure turbine is made of two h Gri20ntally split concentric

casings. The inner casing is placed inside the, outer casing so as to permit the

expansion of the casing at all directions. The main steam from the boiler is admitted

into the HP turbine through t-{O quick clashing~) t09 valves.(HPQCV)and four nos

of Governing va1VBs. These v81ves are operated hydraulically and they operate on

increase / decrease of secondary oil pressure. In the HP turbine, steam expands in a

two row Curtis stage called the impulse stage and further in 8 stages of fixed and


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moving blades Labyrinth type seals are provided for the HP turbine at both front

and II rear ends and CRH steam or 11 at PRDS steam is used for sealing glands.

The medium pressure part of the turbine is a horizontally divided casing. The

guide wheels are partly mounted in the casing in carriers and directly in the casing.

The steam after HP turbine enters the reheater, gets heated to 540C and returns to

the MP, turbine through MPOCSV and interceptor valves steam entering the MP

part flow through 12 fixed and moving blades and taken to the low pressure turbine

through the two corrosive pipes.

The MPQCSV and IVs are also operated Hydraulically.

MEDIUM PRESSURE TURBINE:-

The low pressure turbine is split horizontally into three parts and all the parts are

connected by vertical flanges. The extreme parts of the L.P. turbine are connected

rigidly with surface condensers mounted on sturdy spring supports. The steam

entering the L.P. casing flows in both directions through 4 stages and finally

exhausted into the condenser. The middle part of the L.P. casing houses tube nests

of first and second low pressure heaters for heating the condensate.


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The flanges of H.P., M.P. casings are designed to be heated by steam during

the starting up to turbine generator. By heating of the flanges, the differences intemperature between the cylindrical portion of the casing, flanges and the

connecting bolts are reduced hence limiting the additional stresses on the bottles.The very important criteria for starting and rate of loading the machine is the

difference between the temperature of

the steam admitted in and that of the internals of the turbine. For the purpose of

measuring the temperature of the casing and the steam transfer piping there

monopoles are provided at appropriate points.

SECTION - 3

CONDENSATE AND BOILER FEED SYSTEM

The steam after doing the useful work in the turbine is exhausted into the

condensers where it is condensed by the cooling water (circulating water) flowing

through a network of tubes. After condensation, the condensate is collected in the

hot wells of the condensers. From the hot wells, the condensate is handled by the

condensate extraction pumps and is taken back to the closed loop system.

Condensate pump delivers the condensate into the deaerator through the main

ejectors, chimney steam condenser, gland steam condenser and low-pressure

heaters. There are three number of condensate extraction pumps of vertical turbine

type installed for the above purpose. The pump capacity of 160 T/hr and develops

215 MWC head. Under normal conditions of operation of the unit (including full

load condition) two pumps are required to be kept in service while the third is a

standby.


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The condensate tapped off from the condensate extraction pumps discharge

header is utilized for the following services:-

1. Sealing of valves in the vacuum system. Condensate booster pump stuffing

box sealing.

2. L.P. gland sealing de-super heaters.

3. de-super heaters in the chimney steam condenser.

4. Cooler in the TG-exhaust.

5. Dilution of phosphate and hydrazine solutions.

The make up to the closed cycle is added at the condenser hot well by means

of the make up water pumps. There are 5 numbers D.M. transfer pumps installed

which take their suction from a D.M. water storage tank.

The condensate entering the desecrator under goes desecration process in

which all the dissolved gases in the condensate are removed to a greater extent andthe

desecrated water is collected in the feed water tank which is an integral part of the

deaerator. The feed water tank is installed at a sufficiently higher elevation to

provide a positive suction to the boiler feed pumps.

The flow path of feed water is schematically shown in fig. The boiler feed

pumps (locted in the ground floor of the turbine hall) take their suction from the

feed water tank and deliver the feed water into the boiler drum through high

pressure heater, feed control station and economizer.

Two Nos. of boiler feed pump each of capacity- 445 /hr (8180 1 pm)

developing 178 atm. head is installed. Out of two pumps, one pump is required to be

kept in service while the other one is a standby.

The feed control station consists of three branches of feed lines- a low load

line meant for up to 20% MCR and other two lines meant for 100% MCR


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conditions. (Out of the two 100% MCR lines, one will be service while other is a

standby).

The feed water for the de-super heaters of the SH and RH is tapped off before

the feed control station. Provisions are made to use the condensate booster pump for

initial filling of the boiler drum.

PROTECTIONS AND INTERLOCKS

The main turbine trip relay (TTX) energizes the turbine and trips the turbine

under the following conditions:-

1. Under frequency protection.

2. Generator shut-down energization.

3. Remote trip (P.B).

4. Generator distance relay actuation.

5. Generator negative sequence.

6. Generator transformer ground.

7. Generator loss of excitation.

8. Boiler master trip.

9. L.P.G. heater no.1 level high.(left or right: 775mm).

10.L.P. heater no. 2 level high (left or right: 775mm).

11.Axial shift thrust bearing high: (0.65mm).

12.Hydro mechanical protection axial shift very high: (0.85mm).

13.Primary governing oil pressure high: (3.05atm.).

14.Bearing oil pressure very low: (0.8atm.).

15.Main oil pump discharge very low: (7 atm.).

16.Exhaust pressure very high: (0.5 atm.).

EXPLANATION OF TURBINE SYSTEM :-


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First of all the steam is generated in the steam generator i.e. boiler. From

second pass of the boiler the steam is generated at 530C and at a pressure of 110

kg/cm2

enters the high pressure turbine. The steam works i.e. expands along the

rows of blades and the prime mover i.e. turbine starts moving. After working in the

high pressure turbine the steam again enters the second pass of the boiler for reheat.

All the turbines are coupled to a single rotor. The high pressure turbine is of reaction

turbine, horizontal type multicylinder. In reaction turbine the steam expands

continuously as it passes over the rows of blades and thus there is gradual fall in

pressure during expansion.

The steam from high pressure turbine enters the second pass of boiler for

reheat at 30kg/cm2 at 360C. After reheating the steam again enters the medium

pressure turbine at 28 kg/cm2. The temperature of the steam entering the medium

pressure turbine is 530C. After working the steam leaves the medium pressure

turbine is of impulse type. In impulse turbines steam expands in the nozzles and its

pressure does not alter as it moves over the blades. So the pressure of the steam

entering the MP and leaving MP remains 28kg/cm2. With in the casing of the MP.

Number of tappings namely 4,5,6,7 are made for low pressure heaters. Tapping

number six is the dummy tapping.

Tapping number 5 from the MP turbine goes to the LP turbine goes to theheater NO. 2. The condensate of all the three LPHs goes to the deaerator. Tapping

no.7 from MP turbine goes to high pressure heater no.2, HPH no.1 gets connestion

from the cold reheat from the high pressure turbine. The condensate of the high

pressure heaters goes to the economizer. The outlet temperature of condensate fromHPH is 240C. From the


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deaerator after deaerator the condensate through boiler feed pump goes to HPHs

from where this enters to economizer.

From the MP turbine the steam enters the LP turbine. After working, the

steam enters the condenser, four LPHs are also placed within the casing of the LP

turbine. The condensate from these heaters through a single pipe enters the ejector,

fromwhere the condensate enters the chimney steam condenser and then to the gland

steam condenser through which the condensate enters the HPHs and then goes to

economizer. The steam leaves the LP turbine at -0.90 kg/cm2 i.e. it works under

vacuum.

The work of the ejector is to create vacuum. The condensate from the ejector

enters the main steam to the condenser. After condensation the condensate entersthe

condensate enters the well of the condenser which is at 45C. One tapping from the

well goes to the ejector. a level of the water is maintained in the well. The

condensate from the gland steam condenser and chimney steam condenser enters the

water well.

With in the medium pressure turbine a dummy tapping is there. The steam

enters this turbine at 530C from two sides. The pressure of steam is 28 kg/cm2.

The cold reheat from the HP turbine enters the second pass of the boiler. The

turbine speed is controlled by electro-hydraulic governing device, from where

governing is done.

CONSTRUCTION OF TURBINE :-

The turbine is a tandem compound machine with HP, IP and LP parts. The

HP part is single flow cylinder and IP and LP parts are double flow cylinders. The

individual turbine rotors and the governor rotors are connected by rigid couplings.

In designing the supports for the turbine on the foundation, attention is given

to the expansion and contraction of the machine during thermal cycling. Excessive


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stresses would be caused in the components if the thermal expansion or contraction

were restricted in any way. The method of attachments were restricted in any way.

The method of attachments of the machine components and their coupling together

are also decisive factors in determining the magnitude of the relative axial expansion

between the rotor system and turbine casing.

CASING EXPANSION :-The front and rear bearing housing of the HP turbine canslide on their base plates in an axial direction. Any lateral movement perpendicular

to the

machine axis is prevented by fitted keys. The bearing housings are connected to the

HP and IP turbine casing by guides which ensures that the turbine casing maintain

the central position while at the same time allowing axial movement. Thus the origin

of the cumulative expansion of the casing is at the front bearing housing of the IP

turbine.

ROTOR EXPANSION :-

The thrust bearing is in corporated in the rear bearing housing of the HP

turbine. Since this bearing housing is free to slide on the base plate. The shafting

system moves with it. Seen from this point both the rotors and casing of the HP

turbine expand towards the front bearing housing of the HP turbine. The rotor and

casing of the IP turbine expand towards the generator in a similar manner.

DIFFERENTIAL EXPANSION :-

Differential expansion between the rotor and casing results from the

difference between the casing expansion. Originally from the bearing housing

behind the IP turbine.

CONSTRUCTION OF TURBINE(HP) :-


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Casing :- Barrel type without axial joint. An axially split guide blade carrier is

arranged in the barrel type casing suitable for quick start up and loads.

Blading :-The HP turbine blading consists of several stages. All the stages are

reaction stages with 50%.

FOR IP TURBINE :-

Casing :- The casing of IP turbine is split horizontally and is of double shell

construction.

Casing :- The LP turbine casing consists of a double flow unit and has a triple shell

welded casing. The turbine has a hydraulic speed governor MAX46BY00l and

electro-hydraulic turbine controller. The hydraulic speed governor adjusts main

control values MAA10 + 20AA002 and MAB10 + 20AA00l by way of hydraulic

convertor.


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BOILER

It is single drum, balanced draught, natural circulation, reheat type, verticalcombustion chamber boiler producing steam @375 tons/hr at 139 Kg/Cm2pressure.

The combustion chamber consists of seamless steel tube on all its sides throughwhich water circulates and is converted into steam with the combustion of fuel. The

temperature inside the furnace where fuel is burnt is of the order of 15000C. Theentire boiler structure is of 42 meter height.

Power plant boilers termed as steam generating unit is a major equipment of anythermal Station. The type of boiler installed at G.N.D.T.P. Bathinda is as follows:-

WATER TUBE BOILER IN THERMAL POWER PLANT

SR.NO. GENERAL TYPE OF BOILER TYPE OF BOILER AT

G.N.D.T.P.

1 Outdoor/indoor boiler Outdoor boiler

2 Water tube/fire tube boiler Water tube Boiler


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The water contained in the boiler drums flows through the down corners andthrough rises back to the drum. The heat energy supplied in the furnace is absorbed

by the water walls and water in the circuit is heated up. Then steam due to naturalcirculation moves up & mixture of water vapour and water is separated by steamseparator and then steam is led to super heater for further heating.

STATION CAPACITY OF BOILER

Type of boiler water tubes

Type of joint seam less

Diameter of boiler 1.5m

Thickness of shell 30cm

Working pressure 166N/cm2


Maximum continuous rating 375T/hr.

Super heater outlet pressure 139kg/cm2

Re heater outlet pressure 33.8 kg/cm2

Final water temperature 540oC

Feed water temperature 240oC

Efficiency 88%

Coal consumption per day per unit 1400tons(approximate)

Reheated steam quantity 324T/Hr.

3 Forced draught/balanced draught Balanced draught

boiler

4 Direct coal fired/indirect coal fired Indirect coal fired

5 Dry bottom/wet bottom boiler Dry bottom boiler6 Single drum boiler/multi drum boile Single drum boiler

7 Natural circulation/forced circulatio Natural circulation


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STEAM GENERATION

The steam generating boiler has to produce steam at the high purity, pressure and

temperature required for the steam turbine that drives the electrical generator. Thegenerator includes the economizer, the steam drum, the chemical dosing equipment,

and thefurnace with its steam generating tubes and the superheater coils. Necessarysafety valves are located at suitable points to avoid excessive boiler pressure. The air

and flue gas path equipment include: forced draft (FD) fan, air preheater (APH),

boiler furnace, induced draft (ID) fan, fly ash collectors (electrostatic precipitator or

baghouse)and theflue gas stack.

For units over about 200 MW capacity, redundancy of key components is providedby installing duplicates of the FD fan, APH, fly ash collectors and ID fan with

isolating dampers. On some units of about 60 MW, two boilers per unit may insteadbe provided.
http://en.wikipedia.org/wiki/Furnacehttp://en.wikipedia.org/wiki/Flue_gashttp://en.wikipedia.org/wiki/Centrifugal_fanhttp://en.wikipedia.org/wiki/Air_preheaterhttp://en.wikipedia.org/wiki/Electrostatic_precipitatorhttp://en.wikipedia.org/wiki/Dust_collector#Fabric_filtershttp://en.wikipedia.org/wiki/Dust_collector#Fabric_filtershttp://en.wikipedia.org/wiki/Flue_gas_stackhttp://en.wikipedia.org/wiki/Megawatthttp://en.wikipedia.org/wiki/Megawatthttp://en.wikipedia.org/wiki/Flue_gas_stackhttp://en.wikipedia.org/wiki/Dust_collector#Fabric_filtershttp://en.wikipedia.org/wiki/Electrostatic_precipitatorhttp://en.wikipedia.org/wiki/Air_preheaterhttp://en.wikipedia.org/wiki/Centrifugal_fanhttp://en.wikipedia.org/wiki/Flue_gashttp://en.wikipedia.org/wiki/Furnace


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BOILER FURNANCE

Once water inside theboiler orsteam generator,the process of adding the

latent heat of vaporization or enthalpy is underway. The boiler transfers energy tothe water by the chemical reaction of burning some type of fuel.

The water enters the boiler through a section in the convection pass called the

economizer. From the economizer it passes to the steam drum. Once the waterenters the steam drum it goes down the downcomers to the lower inlet waterwall

headers. From the inlet headers the water rises through the waterwalls and iseventually turned into steam due to the heat being generated by the burners located

on the front and rear waterwalls (typically). As the water is turned into steam/vapor

in the waterwalls, the steam/vapor once again enters the steam drum. The

steam/vapor is passed through a series of steam and water separators and then dryersinside the steam drum.Thesteam separators and dryers remove the water droplets

from the steam and the cycle through the waterwalls is repeated. This process isknown asnatural circulation.

The boiler furnace auxiliary equipment includescoal feed nozzles and igniter guns,

soot blowers, water lancing and observation ports (in the furnace walls) forobservation of the furnace interior. Furnace explosions due to any accumulation of

combustible gases after a trip-out are avoided by flushing out such gases from thecombustion zone before igniting the coal.

The steam drum (as well as the superheater coils and headers) have air vents anddrains needed for initial startup. The steam drum has internal devices that removes

moisture from the wet steam entering the drum from the steam generating tubes. Thedry steam then flows into the superheater coils.

Geothermal plants need no boiler since they use naturally occurring steam sources.Heat exchangers may be used where the geothermal steam is very corrosive or

contains excessive suspended solids. Nuclear plants also boil water to raise steam,either directly passing the working steam through the reactor or else using anintermediate heat exchanger.
http://en.wikipedia.org/wiki/Boilerhttp://en.wikipedia.org/wiki/Steam_generatorhttp://en.wikipedia.org/wiki/Latent_heat_of_vaporizationhttp://en.wikipedia.org/wiki/Enthalpyhttp://en.wikipedia.org/wiki/Economizerhttp://en.wikipedia.org/wiki/Steam_drumhttp://en.wikipedia.org/wiki/Steam_separatorhttp://en.wikipedia.org/wiki/Natural_circulationhttp://en.wikipedia.org/wiki/Coalhttp://en.wikipedia.org/wiki/Explosionhttp://en.wikipedia.org/wiki/Explosionhttp://en.wikipedia.org/wiki/Coalhttp://en.wikipedia.org/wiki/Natural_circulationhttp://en.wikipedia.org/wiki/Steam_separatorhttp://en.wikipedia.org/wiki/Steam_drumhttp://en.wikipedia.org/wiki/Economizerhttp://en.wikipedia.org/wiki/Enthalpyhttp://en.wikipedia.org/wiki/Latent_heat_of_vaporizationhttp://en.wikipedia.org/wiki/Steam_generatorhttp://en.wikipedia.org/wiki/Boiler


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CONDENCERThe surface condenser is a shell and tube heat exchanger in which cooling

water is circulated through the tubes. The exhaust steam from the low pressure

turbine enters the shell where it is cooled and converted to condensate (water) byflowing over the tubes as shown in the adjacent diagram. Such condensers usesteam

ejectors orrotary motor-drivenexhausters for continuous removal of air and gasesfrom the steam side to maintainvacuum.

For best efficiency, the temperature in the condenser must be kept as low aspractical in order to achieve the lowest possible pressure in the condensing steam.

Since the condenser temperature can almost always be kept significantly below 100oC where the vapor pressure of water is much less than atmospheric pressure, the

condenser generally works under vacuum.Thus leaks of non-condensible air into

the closed loop must be prevented. Plants operating in hot climates may have toreduce output if their source of condenser cooling water becomes warmer;

unfortunately this usually coincides with periods of high electrical demand for air

conditioning.

The condenser generally uses either circulating cooling water from acooling towerto reject waste heat to the atmosphere, or once-through water from a river, lake orocean
http://en.wikipedia.org/wiki/Shell_and_tube_heat_exchangerhttp://en.wikipedia.org/wiki/Injectorhttp://en.wikipedia.org/wiki/Injectorhttp://en.wikipedia.org/wiki/Rotaryhttp://en.wikipedia.org/w/index.php?title=Exhausters&action=edit&redlink=1http://en.wikipedia.org/wiki/Vacuumhttp://en.wikipedia.org/wiki/Vapor_pressurehttp://en.wikipedia.org/wiki/Vacuumhttp://en.wikipedia.org/wiki/Air_conditioninghttp://en.wikipedia.org/wiki/Air_conditioninghttp://en.wikipedia.org/wiki/Cooling_towerhttp://en.wikipedia.org/wiki/Cooling_towerhttp://en.wikipedia.org/wiki/Air_conditioninghttp://en.wikipedia.org/wiki/Air_conditioninghttp://en.wikipedia.org/wiki/Air_conditioninghttp://en.wikipedia.org/wiki/Vacuumhttp://en.wikipedia.org/wiki/Vapor_pressurehttp://en.wikipedia.org/wiki/Vacuumhttp://en.wikipedia.org/w/index.php?title=Exhausters&action=edit&redlink=1http://en.wikipedia.org/wiki/Rotaryhttp://en.wikipedia.org/wiki/Injectorhttp://en.wikipedia.org/wiki/Injectorhttp://en.wikipedia.org/wiki/Injectorhttp://en.wikipedia.org/wiki/Shell_and_tube_heat_exchanger


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DEAERATORA steam generating boiler requires that the boiler feed water should be devoid

of air and other dissolved gases, particularly corrosive ones, in order to avoidcorrosion of the metal.

Generally, power stations use adeaerator to provide for the removal of air and otherdissolved gases from the boiler feedwater. A deaerator typically includes a vertical,

domed deaeration section mounted on top of a horizontal cylindrical vessel whichserves as the deaerated boiler feedwater storage tank.

There are many different designs for a deaerator and the designs will varyfrom one manufacturer to another. The adjacent diagram depicts a typical

conventional trayed deaerator. If operated properly, most deaerator manufacturers

will guarantee that oxygen in the deaerated water will not exceed 7 ppb by weight(0.005 cm/L).
http://en.wikipedia.org/wiki/Corrosionhttp://en.wikipedia.org/wiki/Deaeratorhttp://en.wikipedia.org/wiki/Deaeratorhttp://en.wikipedia.org/wiki/Corrosion


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COOLING TOWERS

COOLING TOWERS:-

Type Natural draughtNumbers four

Water cooled 18000 T/hr.

Cooling range 10C

Height 120/122 metres

Cooling towers are structures for cooling water or other working medium to

near-ambient temperature. With respect to the heat transfer mechanismemployed the main types are:

Wet cooling towers operate on the principle of evaporation, (see swamp

cooler)


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Dry cooling towers operate by heat transmission through a surface that

divides the working fluid from ambient air.

In a wet cooling tower the warm water can be cooled to a temperature lower than

ambient, if the ambient air is relatively dry. (see dew point)

With respect to drawing air through the tower are three types of cooling towers:

Natural draft, which utilizes a tall chimney,

Fan assisted natural draft, and

Mechanical draft (or forced draft) which uses power driven fan motors to

force or draw air through the tower.

If ambient conditions are right plumes (fog) can be seen rising out of a wet cooling

tower. Cooling towers can cause growth of legionella bacteria, and should

therefore be regularly checked Diameter of the cooling tower in Bathinda ThermalPower Plant is about 88 feet and 40 stories high.


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BOILER FEED PUMP

As the heart is to human body, so is the boiler feed pump to the steam

power plant. It is used for recycling feed water into the boiler at a high pressure for

reconversion into steam. Two nos. 100% duty, barrel design, horizontal, centrifugal

multistage feed pumps with hydraulic coupling are provided for each unit. This is

the largest auxiliary of the power plant driven by 3500 KW electric motor.

The capacity of each boiler at GURU NANAK DEV THERMAL PLANT is 375tones/hr. The pump which supplies feed water to the boiler is named as boiler feed

pump. this is the largest auxiliary in the unit with 100% capacity which takes

suction of feed water from feed water tank and supplies to the boiler drum after

preheating the same in HP-1, HP-2 and economizer. The delivery capacity of each

boiler feed pump is 445 tones/hr. to meet better requirements corresponding to

the various loads, to control steam temperature, boiler make up water etc. The

detailed particulars checking of protections and inter locks, starting permission etc.

are as below:-

Particulars of BFP and its main motor:-

a) BOILER FEED PUMP:- The 110 MW turboset is provided with two boiler feed

pumps, each of 100% of total quantity. It is of barrel design and is of

horizontal arrangement, driven by an electric motor through a hydraulic

coupling.

Type 200 KHI

No. of stages 6


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Delivery capacity 445 t/hr.

Feed water temperature 158C

Speed 4500 rpm

Pressure at suction 8.30 kg/cm

Stuffing box mechanical seal

Lubrication of pump by oil under pressure

And motor bearing supplied by hydraulic coupling

Consumption of cooling water 230 L/min.

POSITION OF BOILER FEED PUMP


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DESCRIPTION:-

1) PUMP CASING:

T steel pump casing is of the double volute type split on the

horizontal central line. The top and the bottom half casings are located to each

other by dowel pins and secured by studs and nuts, sealed at the axial split being

affected by an asbestos fibre joint.

The pump casing is machined internally to accept the casing rings and deep stuffing

boxes are also formed at each end of the casing to accommodate the water jackets

and the mechanical seals, Thus preventing water leakage along the pump shaft.

2) ROTATING ASSEMBLY:

The dynamically balanced rotating assembly consists of

the shaft, impeller, nuts, keys, seal sleeves, thrust collar, rotating parts of the

mechanical seal and pump coupling.

The double entry impellers are keyed to the shaft and is rotated axially by an

impeller nut on each side of the impeller hub. The impeller is heated with a wear

ring on each shovel, the rings being retained by the grub screws. The seal sleeves

keyed to the shaft and are located and secured by grub screws. Leakage between

the shaft and sleeve is prevented by an O ring fitted in a groove machined in the

bore of the sleeve.

3) JOURNAL & THRUST BEARING:

The rotating assembly is supported at each end of the shaft

by a white metal lined journal bearing and the residual axial thrust is taken up by a

tilting pad double thrust bearing mounted at the non-drive end of the pump.


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The journal bearing shells are of mild steel and are split on a horizontal plane

through the shaft axis, the halves of each bearing shell being provided with lugs

which locate in recesses in the bearing housing which prevent the bearing shell

from turning along the shaft.

4) MECHANICAL SEALS:

The drive and the non-drive end stuffing boxes are fitted

with mechanical seals mounted on seal sleeves and located with a seal cooling

jackets to prevent feed water escaping along the shaft. Tapped holes are provided

on each seal plate and cooling jacket for clarified cooling water inlet and outlet

connections.

5) MOTOR /PUMP COUPLLING:

The drive from the motor to the pump shaft is transmitted

through a diaphragm type spacer flexible coupling.


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CONCLUSION OF TRAINING

Spending my six weeks of training in Guru Nanak Dev Thermal Plant,

Bathinda, I concluded that this is a very excellent industry of its own type. They

have achieved milestones in the field of power generation. They guide well to

every person in the industry i.e. trainees or any worker. I had an opportunity to

work in various sections namely coal handling plant, Boiler section, Turbine section,

De-mineralized water plant, Ash handling plant etc. while attending variousequipments and machines. I had got an endeverous knowledge about the handling

of coal, various processes involved like unloading, belting, crushing and firing of

coal. The other machines related to my field that I got familiar with boiler, turbine,

compressors, condenser etc. I found that there existed a big gap between the

working in an institute workshop and that in the industry. Above all the knowledge

about the production of electricity from steam helped me a lot to discover and sort

out my problems in my mind related to the steam turbine, their manufacture, their

capacity, their angle of blades and their manufacturing. The training that I had

undergone in this industry will definitely help me to apply theoretical knowledge to

the practical situation with confidence.

my thermal project

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