ONTurbine & cooling system

LANCO-1200mw Thermal Power Plant, ANPARA(U.P.)

SUBMITTED TO: SUBMITTED BY: G.M.Mech . LANPL AVIJEET PRATAP ANPARA (UP) B.E.Mech.Engg.3”rd Year INSTITUTE OF ENGINEERING & TECHNOLOGY

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KHANDARI CAMPUS AGRA (UP).

OVERVIEW

Lanco is one of the fastest growing Integrated Infrastructure Enterprises of India, operating across a synergistic span of verticals comprising Power Generation, Power Trading, Non-Power Infrastructure, Construction, EPC, Property Development and Renewables (Solar and Wind).

LancoInfratechLtd's current market capitalisation is approximately Rs. 12,000 Crores (USD 2.59 billion), of which about 68 % equity stake is held by its promoters. Its gross revenue as on March 2009 was over Rs. 6,000 Crores (USD 1.3 billion). Lanco is fast emerging as one of the leading private sector power developers in India with 2087 MW under operation, 8468 MW under construction, and 1039 MW of projects under development. Out of the total portfolio of 11594 MW, the company has achieved financial closure for 4533 MW. Having over two and a half decades of experience in Construction and Civil Engineering, Lanco has created a niche for itself besides building powerful knowledge bank and systems which facilitate continuous adoption and implementation of best practices and technologies. Lanco has strategic global partnership with top-notch companies which include: OHL of Spain, Westports and Genting of Malaysia, Harbin, GE, Dongfang, Doosan etc. Today, Lanco is one of India's largest Power Traders in the private secter.

The year 2010 is being celebrated as Lanco's Silver Jubilee Year. It has been twenty five years since the founder chairman L Rajagopal, taking inspiration from his uncle LagadapatiAmarappa Naidu, began his career as an entrepreneur.

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Lanco has risen to its present level on the strength of their vision and inspiration and under the leadership of L MadhusudhanRao, the Chairman of Lanco Group.

FOUNDER CHAIRMAN

L RajagopalMember of Parliament

Founder Chairman -

LANCO Group of

Companiesemail

:rajagopal@lancogroup.

comwww.rajagopal.i

n

  L Rajagopal, a technocrat-turned industrialist, is the Founder Chairman of LANCO Group. In addition to his entrepreneurial spirit, Rajagopal has a strong sense of social responsibility. He established LANCO Foundation (formerely LIGHT), a Charitable Trust, in the year 2000 to reach out to the needy and has been involved in various philanthropic activities. After one-and-a-half decades of outstanding contribution to the industry, Rajagopal chose to enter public life in 2003. He is a Member of Parliament, India. His avowed mission is to make a difference in the life of the common man.

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ACKNOWLEDEGEMENT

This training report has taken shape only due to Mr. Aruan Kapoor G. M.Mech.LANPL for giving me the chance to do summer training in this giant industry and to have a good and wonderful experience.

With grate sense of gratitude, I also thanks him for his experienced judgement, endless interest and constant encouragement without which it would have not been possible for me to accomplish the project successfully.

I m also highly thankful to Mr. Vineet Tiwari,(LANPL) ; Mr. Vivek Pathak (EPC) , Mr. S.K.Mishra and Mr.Animesh for their co-operation and help.

Last but not the least, I am also thankful to all the employees of LANCO INFRATECH Ltd. for their friendly and helpful attitude in finally up questionnaires and responding to queries and providing required informations for the completion of this project report.

AVIJEET PRATAPMech.Engg. 3”rd YearINSTITUTE OF ENGINEERING & TECHNOLOGY KHANDARI CAMPUS AGRA (UP).

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TRANING REPORT

PROJECT SITE:The proposed plant will be located in village Anpara, in District Sonebhadra, Uttar Pradesh. The 255 acres of land includes 9 acres of forest land required for the plant has been leased to LancoAnpara Power Pvt. Ltd. by Forest Department. The colony for LancoAnpara Thermal Power Plant will be located in 20 acres land adjacent to Anpara- A&B township, at a distance of about 2 km from the plant site which has also been leased from UPRVUNL.

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Diagram of the overall conventional coal- fired power plant

Simplified coal-fired power plant

1. Cooling tower 11. High pressure steam turbine 20. Fan

2. Cooling water pump 12. Deaerator 21. Reheater3. transmission line (3-phase) 13. Feedwater heater 22. Combustion air intake 4. transformer (1-phase) of 3 14. Coalconveyor 23. Economiser5. Electrical generator (3-phase) 15. Coal hopper 24. Air preheater

6. Low pressure steam turbines 16. Coal pulverizer 25. Cold-side Electrostatic precipitator

7. Condensate and feedwater pumps 17. Steam drum 26. Fan

8. Double pass Surface condenser 18. Bottom ash

hopper 27. Flue gas desulfurization scrubber

9. Intermediate pressure steam turbine 19. Superheater 28. Flue gas stack

10. Steam control valve

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Generale layout:

Actual flow diagram of steam power plant

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Conventional coal-fired power plant

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A conventional coal-fired power plant produces electricity by the burning of coal and air in a steam generator, where it heats water to produce high pressure and high temperature steam. The steam flows through a series of steam turbines which spin an electrical generator to produce electricity. The exhaust steam from the turbines is cooled, condensed back into water, and returned to the steam generator to start the process over.

Conventional coal-fired power plants are highly complex and custom designed on a large scale for continuous operation 24 hours per day and 365 days per year. Such plants provide most of the electrical energy used in many countries.

Most plants built in the 1980s and early 1990s produce about 500 MW (500•106watt) of power, while many of the modern plants produce about 1000 MW. Also the efficiencies (ratio of electrical energy produced to energy released by the coal burned) of conventional coal-fired plants increased from under 35% to close to 45%.

The Rankine Cycle - the Heat of any Thermoelectric Power Plant

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Demineralised water plant: :

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The water from natural resources consists of number of minerals, sand, gravel and muddy particles.The function of this plant is to demineralise, purify and filter the coming natural water.This process is completed in following phases.

(i): Clarifier intake pond water is filtered by centrifugal action. Here muddy particles, sand & gravels are settled down to the centre and filtered water is at the top near the water channel.There are two clarifiers each having capacity of 80 million litres. It is cylindrical shaped having diameter of 54.9 m & 3.5 m standing water depth.

(ii): Aerators: In this water are physically filtered using different techniques.

(iii): Chemical plant: In this plantwater from aerators is being mixed with two types of acids and chemically treated in RO system to get completely demineralised water.There are two water tanks outside the chemical plant in which demineralised water is stored and pumped to boiler.

Coal Handing Plant::

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The different parts of coal as are seen as follows.

The coal follows the path as.....

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The raw coal is brought to the power plant by means of wagons. At Wagon Tippler

transferring it into Wagon Tipper Hoppers (W.T.H.) empties the coal from the wagon. W.T.H.

the coal is passed to vibrators from where it is transferred to conveyors.

Conveyor carries coal to crusher house where big pieces of coal are separated in a screen

and sent to crusher through conveyors from where the crushed pieces are transferred to

another conveyor. These are smaller particles of size ranging between 20 mm to 40 mm or

below. Then conveyor takes coal from where tipper transfers the coal to R.C.B. (Rock Coal

Bunker).

T

here are two suspension magnets present one over conveyors just before crusher house

and another over the conveyors just after the crusher house. These magnets remove any

metallic impurities moving on the conveyors along with the coal.

Coal handling plant also takes care of the storage purification and supply of the fuel oil

which is used for mitta lighting up boiler furnace and generation of constant temperature in

furnace during normal operation.

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Coalmeills::

Component:

Coalfigure (it is use to transfer the coal conveyer to roller.)

Roller

Grinding track

C layer(it is use to exit therejected coal.)

Asynchronous moter

Escraper (it use for rotation for grinding track.)

Cllasifire (it is use to transfer the coal to boiler by coal pipe)

Electric heater

Speed- 990 rpm

H.power - 172.5 A

Electrostatic precipitator (ESP) ::

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In the plant there are two ESP’S each of one is connected to boiler and each one have two outlets into the chimney. It is funnel shaped steel structures.

The particle-laden flue gas from the boiler flows through the ESP before it enters the environment. The ESP works as a cleaning device, using electrical forces to separate the dust particles from the flue gas. A typical ESP consists of an inlet diffuser known as an inlet evase, a rectangular collection chamber, and an outlet convergent duct known as an outlet evase. Perforated plates are placed inside the inlet and the outlet evase for the purpose of flow distribution. Inside the collection chamber there are a number of discharge electrodes (DEs) and collection electrodes (CEs). A set of discharge electrodes is suspended vertically between two collection electrodes in a typical wire-plate ESP channel. While the flue gas flows through the collection area, electrostatic precipitators accomplish particle separation through the use of an electric field in the following three steps. The electrical field does the following:

1. Imparts a positive or negative charge to the particles by means of discharge electrodes2. Attracts the charged particles to oppositely charged or grounded collection electrodes3. Removes the collected particles by vibrating or rapping the collection electrodes or

spraying them with liquid.

They are electrically run, in this plant they will consume 6-7MW electricity which will be supplied by board to LANCO thermal power plant.

Force Draught (FD) fans are used to collect primary ash & smoke from boiler to ESP.

ESP HOPPERSESP HOPPERS

Chimney::

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This chimney is twin flue and its design is given by L&T group. In the plant chimney is made of 275 m high concrete supporting structure. There are two steel flue cans (OD 6.8 m)inside the supporting structure for the ejection of smoke. These flue cans are being supported with the help of steel beams resting on inner platforms of supporting structure. Flue can is made of steel cans of 100mm thick laid over each other by the help of jack & cables.It is consist in 7 plate form.i.e1. 0 to 35 m2. 35 to 88.5 m3. 88.5 to 13.5 m4. 133.5 to 178.5 m5. 178.5 to 223.5 m6. 223.5 to 262 m7. 262 to 267 m

After that joint the minishel to 275 m.

These cans are well rebated & welded properly. They are thermally insulated by rock wool insulating material. Density of rock wool is 96 kg/cubic m.

BOTTAMOD : 34 m ,RCC wall thickness: .9 m

TOP OD: 20 m ,W.T. .25 m

The steam generator

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A conventional coal-fired steam generator is a rectangular furnace about 15 metres on a side and 40 metres tall. Its walls are made of insulated steel with a web of high pressure steel boiler tubes attached to the inner surface of the walls.

The deaerated boiler feedwater enters the economizer (see the adjacent diagram) where it is preheated by the hot combustion flue gases and then flows into the boiler steam drum at the top of the furnace. Water from that drum circulates through the boiler tubes in the furnace walls using the density difference between water in the steam drum and the steam-water mixture in the boiler tubes.

Pulverized coal is air-blown into the furnace from fuel nozzles at the four corners and it rapidly burns, forming a large fireball at the center. The thermal radiation of the fireball heats the water that circulates through the boiler tubes mounted on the furnace walls. As the water circulates, it absorbs heat and partially changes into steam at about 362 °C and at a pressure of 190 bar (19 MPa). In the boiler steam drum, the steam is separated from the circulating water. The steam then flows through superheat tubes that hang in the hottest part of the combustion flue gases path as it exits the furnace. Here the steam is superheated to about 540 °C before being routed into the high pressure steam turbine.

(Steam generetor or boiler)

FLOW DIAGRAM FOR STEAM GENERATOR-

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CHARACTERISTICS:

The general character of this boiler is sub –critical, natural circulation, drum type, single furnace, tangential firing, tin pot soft coal fired , solid tapping slag, single reheating, balanced draft, metal waterproof on the roof, 10 burneruse front and rare side, full- steel structure & pie-type arrangement.

Water tank type 2 boiler use here.

ATTEMPERATION:

Water spraying shall be used for steam control, burner wing shall be used for RH steam control, & the spray water is the auxiliary increase air properly when low loads.

OPERATION MODE:

Boiler will be operated in constant pressure or constant –sliding –constant pressure mode.

FEED WATER OPERATION SYSTEM:

There are 2 operating lines to feed water operating platform, own is the man feed line for boiler normal run, which is equipped with one motor gate valve, another is bypass feed water line boiler start-up, which is equipped with one stem control valve & two gate valves.

ECONOMISERS:

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Water from feed water system goes to economisers inlet header from 2 ends separately, the water flow from economiser coil down to up enter the 3 intermediate economiser header(dia. 273x45, 20G) & flow up through 3x56 hanger tubes(dia. 60x9, SA-40C) which is drum through connecting pipes. A circulation (dia. 133x16, 20G) is designed to connect economiser inlet header& first right down comer.

DRUM:Material= 13MnNiMo54The drum is equipped with two aeral colour level gauges, one electrical water level gauges for perch water filled. Four singe room balance vessels, 3 safety valves and there are much instruments for continuous blow down, emergency drain, back-up, chemical feeding, pressure gauge & seven metal temperature measuring points.

DRUM INTERNALS: Drum internals is single section vaporize system, the first stage distributor is turbo separator. The 2nd stage distributor is corrugate plates. They are arranged at two lines along C.L. of drum shell. Little separated water flow in water space through drain tube located on bottom of drum, on top of drum are equipped with equalizing hole plates. On bottom of drum a baffle are equipped to avoid directly contact b/w saturated water & feed water.

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.Super heatersystem:

SUPER HEATER STEAM FLOW:

The superheated system consists of six stages:1. Steam cooled roof2. Cooled wall3. Panel division super heater4. Platen super heater5. Final super heater6. Primary super heater.

Feedwater heating and deaeration::

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The feedwater used in the steam generator consists of recirculatedcondensate water and makeup water. Because the metallic materials it contacts are subject to corrosion at high temperatures and pressures, the makeup water is highly purified in a system of water softeners and ion exchange demineralizers. The makeup water in a 1200 MW plant amounts to about 180 litres per minute to offset the small losses from steam leaks in the system and blowdown from the steam drum (see steam generator diagram below).

The condensate and feedwater system begins with the water condensate being pumped out of the low pressure turbine exhaust steam condenser (commonly referred to as a surface condenser). The condensate water flow rate in a 1200 MW coal-fired power plant is about 55200 litres per minute.

The feedwater plus makeup water flows through feedwater heaters heated with steam extracted from the steam turbines. Typically, the total feedwater also flows through a deaerator[4][5] that removes dissolved air from the water, further purifying and reducing its corrosivity. In the deaerator of following the deaeration, the water may be dosed with hydrazine, a chemical that scavenges (removes) the remaining oxygen in the water to below 5 parts per billion (ppb). It is also dosed with pH control agents such as ammonia or morpholine to keep the residual acidity low and thus non-corrosive.

Diagram of a tray-type boiler feed water deaerator (with vertical, domed aeration section and horizontal water storage section.

Steam condensing and cooling towers

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HERE USE 2DOUBLE PASS SERFACE CONDENSER:

Main component:

DOUBLE PASS SERFACE CONDENSER:>PRDS(pressure reduce device system)>Expansion wall>tube support wall>DWS>7/8 LP duplex heater>CEP(condenser extraction pump or condenestate pump)>vaccume pump>Hot well>stiffner plate>stainless steel tubes

COOLING TOWER:>4cooling towers of 11 flumes>Exhuast fan

PUMP HOUSE:

>circulating water pump(CW) nos. (5)>Axuilary cooling water pump(ACW) nos (3)

SERFACE CONDENSER:

The exhaust steam from the low pressure turbines is condensed into water in a water-cooled surface condenser. The condensed water is commonly referred to as condensate. The surface condenser operates at an absolute pressure of about 35 to 40 mmHg (i.e., a vacuum of about 720 to 725 mmHg) which maximizes the overall power plant efficiency.

The surface condenser is usually a shell and tube heat exchanger. Cooling water circulates through the tubes in the condenser's shell and the low pressure exhaust steam is cooled and condensed by flowing over the stainless steel tubes as shown in the adjacent diagram. Typically the cooling water causes the steam to condense at a temperature of about 35 °C. A lower condensing temperature results in a higher vacuum (i.e., a lower absolute temperature) at the exhaust of the low pressure turbine and a higher overall plant efficiency. The limiting factor in providing a low condensing temperature is the temperature of the cooling water and that, in turn, is limited by the prevailing average climatic conditions at the power plant's location.

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(Diagram of a typical water-cooled surface condenser)

.

Rectangular, mechanically induced draft cooling towers (with water vapor plumes).

The condensate from the bottom of the surface condenser is pumped back to the deaerator to be reused as feedwater.

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The heat absorbed by the circulating cooling water in the condenser tubes must also be removed to maintain a constant cooling water supply temperature. This is done by pumping the warm water from the condenser through either natural draft, forced draft or induced draftcooling towers (as seen in the images to the right) that reduce the temperature of the water by about 11–17 °C and expel the low-temperature waste heat to the atmosphere. The circulation flow rate of the cooling water in a 1200 MW unit is about 34.08 m³/s at full load.[6]

Some older power plants use river water or lake water as cooling water. In these installations, the water is filtered to remove debris and aquatic life from the water before it passes through the condenser tubes.

The cooling water used to condense the steam in the condenser returns to its source without having been changed other than having been warmed. If the water returns to a local water body (rather than a circulating cooling tower), it is mixed with cool raw water to lower its temperature and prevent thermal shock to aquatic biota when discharged into that body of water.

In this plant induced draft cooling towers are constructed by GACTEL.There are four cooling towers of 11 flumes of each are being constructed.The capacity of each cooling tower tank is 6000 cubic metre. It is a complete RCC structure comprises of complex RCC trusses. Its foundation is 1.8 m deep & size is 160*15 sq m.Flumes are of frustum shaped RCC structure having 150 mm wall thickness.By the use of cooling towers in thermal power plants the consumption need of water reduces to its 10%.

Pump House:

The pump house has the following pumping units:

High head pump (4): they supply water to the condenser but are only used only when canal

is not sufficient to sustain the process. Their head is up to 32 m.

Low head pump (4): they constitute the main pumping unit, supplying water continuously

to the condenser. Their head is 10 to 12 m.

Screen wash pump (4): (only three are in working order). These supply the traveling water

stream and in emergency they may also supply the water to the plant.

Fire fighting pumps (2): these supply water for fire fighting and extinguishing arrangements

both in the plant as well as in the pump house.

Make up water pump (2): these supply the makeup water.

Cooling system::

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There are some cooling systems present in the whole operation::

1. STATOR WATER COOLING SYSTEM:(Cools the coils of the generator; it’s a open loop type cooling system)

System Details :

Stator coil cooling water system is an independent closed cooling water system.

Separate water tank is used for storing & maintaining high purity water for cooling of

stator coil. Two water sources are provided for maintaining the level & purity of

cooling water. One from DM water supply line to maintain the pH value and second

from condensate water discharge line. To avoid the condensation of moisture on stator

coil when the humidity of hydrogen is high and for maintaining temperature of stator

water higher than hydrogen electric resistance heater is equipped with this system.

System consists with 2 Nos. electric motor driven pumps, 2 Nos. cooler, 2 Nos.

filter and one mixed bed type ion exchanger for maintaining the water purity. Two

Nos. conductivity meters are set in the system. One is used for supervising the water

conductivity of inlet water of stator coil and other is used for supervising the water

conductivity out from the ion exchanger.

During normal system operation the stator water carries away heat from stator

windings & generator bushings and gives away this heat to CCC Water in stator water

cooler.

System Flow :

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2. PLATE HEAT EXCHANGER: (Cools the seal oil)

Details :

Since Generator is filled with H2 gasunder pressure during operation, it is essential to keep H2 from leaking out to atmosphere where it could cause an explosion. To achieve this, generator gland seals, which are supplied with oil from the seal oil system, are installed inboard of each of generator journal bearings.

The function of seal oil system is to:1) Prevent H2 from escaping from the generator.

2) Lubricate the seals. 3) Provides automatic take over of DC Seal oil pump, in case of failure of AC

Seal oil pump. 4) Cools & filters the oil before supplying to seals.5) Always maintains a constant differential pressure of 0.056 MPa between

the H2 & Seal oil (seal oil pressure more) for proper sealing. 6) Drains out effectively the oil flowing towards H2 side without allowing any

H2 to escape.

The seal oil system consists of following equipment:

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AC motor driven Seal oil pump(4 Nos.),DC motor driven ( Emergency) Seal oil pump (1No), Seal oil coolers, Seal oil filters, DP regulator, Back up pressure regulator , Drain Regulator (H2 side), Gauges and switches for monitoring and alarm Seal oil system must be placed in operation prior to admitting H2 in to the generator. Seal oil pressure must be maintained at the seals whenever H2 gas is inside generator & when shaft is turning.

System Working :

During normal operation, the air side AC Seal oil pump normally takes suction from the turbine lube oil pipe, discharge to seal oil filter& supplied to air side generator seals. The air side seal oil pressure is maintained at 0.056 MPa above generator H2 pressure by air side differential pressure regulator (DPR), mounted on the air side seal oil pump discharge header. The H2 side AC Seal oil pumps takes suction from the H2 side seal oil tank & discharge to seal oil cooler & filter. This oil is supplied to H2 side generator seals through H2 side Oil pressure balance valve(DPR) which maintains a DP of 1.5KPa (0.0015 MPa) between air side supply seal oil pressure & H2 side supply seal oil pressure. From gland seals, the airside seal oil drains are connected with turbine bearing oil return header & flows back to the main oil tank. The H2 side seal oil drain flows back to H2 side seal oil tank. If seal oil pressure is too high, the overflow valve (both H2 & air side) open & releases some of the pump discharge back to suction line to reduce seal oil discharge pressure.

There is also a D.C air side Seal oil pump which comes into service in case of tripping of main AC seal oil pump & maintains seal oil pressure. There are vapor extractor fans, provided for the generator vacuum oil tank to remove H2 from oil before it is sent back to turbine lube oil return header. The seal oil system should be in service before generator is placed on turning gear or before Generator is filled with H2 gas.

System Flow:

A. Air side

a) Normal operation loop

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3. LUBE OIL SYSTEM:

To reduce the wear and tear of the rotating elements.To maintain the temperature of the bearings.PURPOSE:

Lubrication of turbine. Cooling of bearings Sealing medium in Hydrogen cooling system Turbine barring gear operation. Working fluid in Governing system

COMPONENTS: Oil coolers Oil Filters Oil Injectors Centrifuge Vapour Extractors

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Steam turbine

A steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and converts it into rotary motion. Its modern manifestation was invented by Sir Charles Parsons in 1884.

nozzle movable bladeSteam thermal -------------- kinetic energy ---------------------- mechanical energy Energy……..expand…… impulsive force

They are the basic building block of a powerplant. A steam turbine is a mechanical device

that extracts thermal energy from pressurized steam, and converts it into rotary motion.

The thermal energy of steam delivers to the turbine is converted into the kineticenergy of

the steam flow. The jets of high velocity steam are then directed to a ring of blades that are

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free to revolve. These rings are fixed to the rim of revolving rotor. In a modern steam

turbine, there are several wheels of moving blades which keyed to the same shaft. Between

each row of moving blades, there is a ring of fixed blades, there stationary blades are fixed

to the turbine casing & they face in opposite direction to moving blades. The function of

fixed blade is to receive the steam jet coming out of moving blade ring & to divert it to the

next moving blade rings by changing its direction.

A rotor of a modern steam turbine, used in a power plant

It has almost completely replaced the reciprocating piston steam engine primarily because of its

greater thermal efficiency and higher power-to-weight ratio. Because the turbine generates rotary

motion, it is particularly suited to be used to drive an electrical generator – about 80% of all

electricity generation in the world is by use of steam turbines. The steam turbine is a form of heat

engine that derives much of its improvement in thermodynamic efficiency through the use of

multiple stages in the expansion of the steam, which results in a closer approach to the ideal

reversible process.

Steam Supply and Exhaust ConditionsThese types include condensing, noncondensing, reheat, extraction and induction.Noncondensing or backpressure turbines are most widely used for process steam applications. The exhaust pressure is controlled by a regulating valve to suit the needs of the process steam pressure. These are commonly found at refineries, district heating units, pulp and paper plants, and desalination facilities where large amounts of low pressure process steam are available.Condensing turbines are most commonly found in electrical power plants. These turbines exhaust steam in a partially condensed state, typically of a quality near 90%, at a pressure well below atmospheric to a condenser.Reheat turbines are also used almost exclusively in electrical power plants. In a reheat turbine, steam flow exits from a high pressure section of the turbine and is returned to the boiler where additional superheat is added. The steam then goes back into an intermediate pressure section of the turbine and continues its expansion.Extracting type turbines are common in all applications. In an extracting type turbine, steam is released from various stages of the turbine, and used for industrial process needs or sent to boiler feedwater heaters to improve overall cycle efficiency. Extraction flows may be controlled with a valve, or left uncontrolled.Induction turbines introduce low pressure steam at an intermediate stage to produce additional power.

Raising steam (Thermal Sources) Steam is mostly raised from fossil fuel sources, three of which are shown in the above diagram but any convenient source of heat can be used.

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Principle of Operation and DesignWorking Principles:High pressure steam is fed to the turbine and passes along the machine axis through multiple rows of alternately fixed and moving blades. From the steam inlet port of the turbine towards the exhaust point, the blades and the turbine cavity are progressively larger to allow for the expansion of the steam.The stationary blades act as nozzles in which the steam expands and emerges at an increased speed but lower pressure. (Bernoulli's conservation of energy principle - Kinetic energy increases as pressure energy falls). As the steam impacts on the moving blades it imparts some of its kinetic energy to the moving blades.

There are two basic steam turbine types, impulse turbines and reaction turbines, whose blades are designed control the speed, direction and pressure of the steam as is passes through the turbine.

Types

Impulse turbines:An impulse turbine has fixed nozzles that orient the steam flow into high speed jets. These jets contain significant kinetic energy, which the rotor blades, shaped like buckets, convert into shaft rotation as the steam jet changes direction. A pressure drop occurs across only the stationary blades, with a net increase in steam velocity across the stage.As the steam flows through the nozzle its pressure falls from inlet pressure to the exit pressure (atmospheric pressure, or more usually, the condenser vacuum). Due to this higher ratio of expansion of steam in the nozzle the steam leaves the nozzle with a very high velocity. The steam leaving the moving blades is a large portion of the maximum velocity of the steam when leaving the nozzle. The loss of energy due to this higher exit velocity is commonly called the "carry over velocity" or "leaving loss".

Reaction turbines:In the reaction turbine, the rotor blades themselves are arranged to form convergent nozzles. This type of turbine makes use of the reaction force produced as the steam accelerates through the nozzles formed by the rotor. Steam is directed onto the rotor by the fixed vanes of the stator. It leaves the stator as a jet that fills the entire circumference of the rotor. The steam then changes direction and increases its speed relative to the speed of the blades. A pressure drop occurs across both the stator and the rotor, with steam accelerating through the stator and decelerating through the rotor, with no net change in steam velocity across the stage but with a decrease in both pressure and temperature, reflecting the work performed in the driving of the rotor.

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Compounding of Turbines:In the thermal power stations where the generators run at 3000 r.p.m., single stage turbine

(one ring of stationary nozzle & one ring of rotating blades) is undesirable. To get the

reasonable blade tip speeds in turbines, the method known as ‘compounding’ is employed.

In this method number of rotor in series, keyed on same shaft, is used & the steam

pressure& jet velocities absorbed in steps as it flows over the moving blades.

The high pressure steam is controlled by two main steam stop valve and four control valves and intermediate pressure steam is controlled by two IP Stop valve and two control valve.All the 10 admission valves are driven by servomotors that adopt the HP Fire resistance oil as working medium. All six control valves and one main steam valve (MS-2) are controlled continuously by servo valves and microcomputer interface of DEH. All other valves one main steam stop valve and two IP stop valve are controlled by solenoid valve and DEH interface in two digit way.

Casing or Shaft Arrangements:These arrangements include single casing, tandem compound and cross compound turbines. Single casing units are the most basic style where a single casing and shaft are coupled to a generator. Tandem compound are used where two or more casings are directly coupled together to drive a single generator. A cross compound turbine arrangement features two or more shafts not in line driving two or more generators that often operate at different speeds. A cross compound turbine is typically used for many large applications.

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PRE WARMING OF THE HP CASING: Inspection before the warming

1. Ensure HP Turbine control valve is close. Steam parameter 0.4 to 0.8 MPa and steam temperature 200 – 250 OC and it should have minimum 50 OC of superheat.2. Ensure Turbine is on barring gear and vacuum in condenser should be around 19.6KPa.3. Metal Temperature at HP Turbine inner casing HP Control stage is below 150 OC.WARMING UP OPERATION:

Gradually open the reverse flow valve (RVF) and maintain the casing pressure 0.4 to 0.5 MPa. Let the steam flow through the drain valve and to IP Turbine through the gland between the HP and IP casing.

During warming up don’t allow the rate of rise of temperature of the casing more then 50 OC/hr by adjusting the RFV.

When the temperature of the upper half of the inner wall near the HP Control stage reaches the 150 OC throttle valve before RFV reduced to the 10% and maintain it.

Pre warming process of control valve: Open the main steam stop valve-2 in the pre warming position about 10%.Check

the rotational speed of the Turbine rotor, it may increase due to passing of the governing valve port.

Monitor the Temperature difference of the inner and outer port of the control valve if the temperature difference exceeds 80 OC, stop the pre warming. When the temperature comes below 70 OC start the pre warming by opening the HP stop valve-2 by 10 %.

Repeat the pre warming process till the inner and outer metal temperature of the valve casing temperature reaches 150 OC and more depending upon the pre-warming condition.

When pre warming completed stop the MSV-2 Valve. Close the stop valve body drain.

Main Steam, Reheat Steam, and Regenerative Systems

Main Steam and Reheat Steam System:

The main steam and reheat steam system uses a unit system.

The main steam from boiler super heater enters the HP main steam stop valve via two main

steam pipe lines, and then it is admitted into the HP casing through 4 HP main steam pipes.

After working inside the HP casing, the steam enters the boiler reheater via two HP exhaust

non-return valves and two cold reheating steam pipelines. The reheated steam temperature

will rise to 537 at a pressure up to 2.304MPa. Afterwards the steam will enter the IP ℃combined steam valve via two hot reheating steam pipelines and then into the IP casing

through 2 IP main steam pipelines. Leg bypass steam is led out from before the HP main Ⅰ

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stop valve and extracted to the cold pipe of reheater through 1st stage temperature

decrease and pressure reduction. The Leg bypass steam is led out from before the IP Ⅱcombined valve and extracted to the condenser after the 3rd stage temperature and

pressure reduction.

Regenerative System:

This unit has 8 stages of regenerative process with 3 HP heaters, 1 deaerator and 4 LP

heaters.

This deaerator adopts the sliding pressure operation mode. The design of engineering

system and selection of auxiliary equipment shall both cater to the requirement for sliding

pressure operation.

Refer to Table 2-1-1 for steam extraction parameters and flows at various stages under THA

conditions.

When the heaters are switched off or when initial steam parameters are reduced, the load

should be decreased for operation of limited flow, to ensure that the stress of blade is not

overrun. Under any working condition, the pressure after governing stage and the steam

extracting pressures at different stages shall not exceed the corresponding pressures as

under the maximum working condition.

Table 2-1-1 Summary sheet for regenerative and steam extracting parameters and flows under

THA condition

Steam Turbine Proper Auxiliary Systems:According to user requirements, this unit is configured with IP casing startup system

(including HP casing pre-warming, and IP casing starting system), and also deployed with

turbine pre-warming and sandwich heating systems for projects not adopting IP casing

startup mode, to cater to controlling of cold and warm HP/IP combined startup over

temperature and differential pressure of HP casing.

HP casing pre-warning system:

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The HP casing pre-warming system is available on the high-row pipeline before the high-

output non-return valve, to heat and pre-warm the HP/IP casing prior to cold startup and

ensure that the temperature after HP 1st stage before cold startup can reach 150 , the ℃temperature difference of upper half and lower half inner and outer walls is less than 50 , ℃the temperature variance with the inner and outer walls of the upper and lower left and

right flanges is lower than 50 , and temperature of the inner walls in the steam inlet area ℃and the steam outlet area for IP casing exceeds 50 , to reduce the thermal impact at ℃startup, to avoid the unsmooth expansion, and excessive differential pressure. This pre-

warming system is composed of HP steam pipeline and reverse flow valve.

Prior to turbine charge, the steam of auxiliary steam behind the HP bypass valve enters the

HP casing through reverse flow valve (RFV). Steam seal between the HP/IP casings, drain of

the HP main steam pipe and the drain of the HP casing are discharged, to preheat the HP

casing. Ensure that the cylinder internal pressure is at 0.4~0.5MPa through adjusting the

reverse flow valve and drain valve and fulfil the cylinder warm-up through heating as per

Instruction for Start-up and Operation.

During HP casing pre-warming, open 10% of the HP main steam valve to pre-warm the HP

main steam valve casing and the main steam pipe. The pre-warming steam pressure is

0.4~0.8MPa, the temperature is 200 ~250 , and a heat above 50 is maintained.℃ ℃ ℃

IP casing start up system:

A pneumatic valve (using 0.4~0.7MPa compressed air) is set on the pipeline leading to

condenser on the high-output piping before the high-output non-return valve to implement

IP casing start up. This valve will open during IP casing start up, to put through the HP casing

with condenser. Make sure that the blades of HP casing are not overheated for blast.

IP casing start up can reduce the loss of unit service lifetime during start up, and at the same

time can shorten the unit start up time and save the start up cost.

Cylinder sandwich heating systemA steam inlet for heating sandwich is set in the lower half of the HP/IP outer casing. The

steam from the steam inlet header for sandwich heating enters the left and right steam

inlets respectively through valve to heat the sandwich between HP inner casing and HP/IP

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outer casing, so that the differential pressure and temperature during start up can be timely

adjusted.

The HP casing sandwich heating system shall be engaged in accordance with HP/IP

differential pressure, temperature difference between outer wall of HP inner casing and the

inner wall of HP outer casing, and the temperature of HP casing. The HP casing sandwich

heating system can be disabled within the allowable range of differential pressure.

During normal operation, HP inlet steam is still surrounded by IP inlet steam, and the

temperature difference inside and outside is still nearly zero. The steam leaked out from

between the steam a seal of HP/IP casings enters into the HP casing from IP casing during

start up through IP casing, to warm up the cylinder; while during normal operation, the

steam leaks from HP casing to IP casing and works there. The steam in Block enters the ⅠBlock through 5mm-wide annular clearance along outside the insulation ring, and goes Ⅱinto #2 HP heater (JG2) together with extracted steam. The temperature and pressure in

Block are the parameters for HP steam exhaust, and the pressures in Block and Block Ⅱ Ⅰ Ⅱare equal to each other. Under the function of heat radiation from inner casing wall and

locating ring, temperature in Block is comparatively closer to that of the inner wall for Ⅰinner casing after HP Stage 3.

The above structure is adopted for HP part, so that different blocks outside and inside the

HP casing can maintain a rational distribution of temperature and pressure. Mechanical

stresses arising from heat stress and differential pressure shall all be limited to a

comparable lower level.

Emergency discharge system:

When unit is disengaged from load, redundant steam inside the HP casing and HP steam

admission pipe will possibly leak into IP and LP casings through shaft seal between HP/IP

casings, to overspeed the unit. Therefore the emergency discharge device is set between

the HP/IP gland seals. When unit is tripped, turn on the blow-down valve (BDV) quickly and

lead the most redundant steam into condenser, to avoid unit from overspeeding.

Steam Distribution:The control system of this unit has the function for valve management, and it can achieve

the sequence valve control and single valve control of the governing valves as well as the

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coordination of HP and IP valves, to adapt to different requirements for startup and

operation. The unit can perform undisturbed switchover of the two modes under operation.

These two control modes correspond to two different steam admission modes, of which the

sequence valve can achieve the nozzle governing operation of the unit, while the single

valve can realize the throttle governing operation. To reduce the thermal impact during

startup, the single valve mode, i.e. the throttle steam admission mode (full-admission mode)

can be used to avoid the overlarge stress on steam cylinder and rotor, to ensure a smooth

startup of unit. After the target load has been reached and the temperature pattern has

tended to stable, it can be switched to the sequence valve mode that is the nozzle steam

distribution mode, to guarantee a good economic efficiency.

Nozzle Steam Distribution (Partial Steam Admission): HP part has 4 governing valves,

correspondent to 4 group of nozzles. The number of 4 groups of nozzles for steam passages

is all 37 pieces. When valve levers of No. and No. governing valves are opened to Ⅰ Ⅱ39.2mm.No. governing valve turns on. When the stroke of No. governing valve lever Ⅲ Ⅲreaches 39.2mm, No. governing valve begins to open.ⅣThrottle Steam Distribution (Full Circular Steam Admission): The 4 governing valves in HP

part open as per same valve locations according to the instruction of the control system and

admit steam at the same time in correspondence to the 4 group of nozzles.

RH steam enters IP part through the casing lower half left and right sides via 2 IP combined

steam valves. As full circular steam admission is performed in the IP part, only throttle

governing mode is adopted by IP governing valves for operation. The main steam valve and

governing valve inside the IP combined valve share one valve seat, respectively controlled

by their independent servomotors. The caliber of governing valve is Φ510mm and the valve

plays governing function when flow is lower than 30%, to maintain the minimum necessary

pressure inside the reheater. When flow is higher than 30%, the governing valve keeps fully

open, and only HP governing valve is used for adjusting the load.

Valve Management:The guiding idea of valve management and steam distribution technology is that the turbine

can freely choose governing mode and realize throttle regulation and nozzle regulation

without encountering any disturbances during the entire operation. The throttle governing

mode is used so that the turbine can quickly start up and shut down without occurrence of

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excessive thermal stress for load variations (this will reduce the loss of unit service life).

Nozzle governing and variable pressure operation mode is used within the normal load

range to maximize the economic efficiency and operational flexibility of the unit.

There are “Single Valve-Sequence Valve” selection pushbuttons on the operation board and

the operators can choose the turbine’s control valves for distribution modes. The selection

of distribution modes shall be dependent on the startup and operation modes of the

turbine.

Startup process: No matter it is a IP casing startup or a HP/IP casing combined startup,

during turbine charge, speed rise, synchronization, and low-load, normally the throttling

mode by single valve is selected. Since this mode allows the steam stream to enter the IP

casing or HP governing stage from an entire circumference, the cylinder and rotor can be

heated up and expanded in a uniform manner, which can effectively reduce the thermal

stress during the startup process and decrease the mechanical stress on moving blade at

governing stage.

Normal load operation: If load changes frequently with a big variation rate, steam

distribution mode by single-valve throttling regulation should be chosen to minimize

temperature changes and thermal stress for the HP casing. However, if the unit runs in a

stable manner for a long period at a load that is less than the rated load, nozzle governing

mode is to be selected to achieve a higher thermal efficiency.

Shutdown process: In the case of a normal shutdown followed by planned overhaul, nozzle

governing mode is beneficial, as if the unit is shut down using this mode; the metal

temperature will be low, which can shorten the cooling down time. As for shutdowns of

peaking unit or other temporary shutdowns that only last several hours, throttle governing

mode shall be applied to maintain a higher metal temperature to facilitate a quick unit re-

start.

Steam Seal System:The main function of the turbine steam seal system is to use steam supplied by the system

to seal the steam of HP and IP casings from leaking out and to prevent air from entering the

LP casing through the shaft ends to break the condenser vacuum.

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Shaft-end steam seal:

This unit totally provided with five groups of steam seals for HP/IP and LP casings. High and

low “sharp-toothed” sealing strips are used for HP/IP casing front and rear gland seals in a

soft embedded ferrite structure, and copper sealing strips are adopted for LP steam seals in

a use of bare shaft sharp-toothed structure.

Steam seal between HP&IP turbine has two sections, to reduce the steam leakage from HP

casing. An emergency discharge device is set between the two sections and there are 12-

Φ30 through holes radial on the IP end steam seal to lead the leaked steam from HP casing

into before IP Stage 1 for continued work.

HP casing rear steam seal has four sections. Bleeding steam of the first section is directed

into the deaerator (CY); the leaked steam of the second section is used as interface for self-

sealing system (SSR); and bleeding steam of the third section is led into the seal steam

heater (CF).

IP casing rear steam seal has three sections. Bleeding steam of the first section is used as

interface for self-sealing system (SSR) and leaked steam of the second section is admitted

into the seal steam heater (CF).

LP casing front and rear steam seals have three sections, respectively. The supplied steam of

the first section is used as interface for self-sealing system (SSR) and bleeding steam of the

second section is introduce into the seal steam heater (CF).

Self-sealing steam seal system:

Self-sealing interfaces for HP, IP and LP steam seals are connected with pipes and gland

pressure control stations which are composed of HP steam supply governing valve, RH cold

stage steam supply and auxiliary steam source supply governing valve, and overflow

governing valve. During low load, proper steam source is selected based on the startup

status to feed steam to the HP, IP and LP steam seals. At high load, bleeding steam of HP/IP

steam seal is provided for steam supply of LP steam seal, and its steam flow is sufficient to

satisfy the LP sealing demand. Under such condition, the overflow governing valve of the

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control station is engaged, to maintain the pressure of self sealing system. The normal

system pressure is 0.13MPa.

Gland steam returning piping system:

HP, IP and LP last-stage steam seals are all connected with pipes and steam seal heater. This

system is composed of one steam seal heater and two shaft seal fans, used for extracting

the steam-air mixture from the last-stage shaft seal cavity chamber, to maintain a negative

micro-pressure of -6.3kPa (i.e. pressure 95.2kPa) of this chamber.

LP steam seal temperature control station:

A steam temperature control station is set on the LP seal steam supply pipeline, to maintain

steam supply temperature for LP shaft seal. The temperature control station is mainly

composed of water spray attemperator and temperature governing station, to automatically

maintain a temperature for steam supply at LP steam seal not higher than 150 .℃Steam Turbine Proper & Piping Drain System:When turbine is starting up, shutting down, running at low load or running with low

parameter, it is all likely that the condensate water will form in turbine proper, valves, main

steam piping, reheat steam pipeline, extraction steam piping, and seal steam supply and

extraction pipe, etc. Such condensate water must be drained in a timely manner, otherwise

it may cause water entry into turbine and give rise to water slug, leading to damage of

machine. Therefore it is necessary to arrange the drainpipe lines reasonably and drain the

water timely, to ensure a safe operation of the turbine.

Water drains for turbine proper, main stop valves, governing valves, HP main steam pipe, IP

main steam piping, heat regenerative extraction pipeline (before extraction non-return

valve) consist of the turbine proper and piping drain system.

Since pressures in the above mentioned drainpipes are different, they should be directed to

HP, IP and LP drain mother pipes to turn in a sequence from high pressure to low pressure

and finally sent to the drain flash box for convergence. The expanded steam will then enter

the condenser via steam pipe of the flash box whereas the condensed drain water will be

led into the hot well of condenser. This draining approach facilitates centralization, control,

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maintenance and overhaul of valves and can also avoid steam and water impacts inside the

hot well for steam-water separation.

The drainpipes of this system are connected with the drain mother pipes in turn in a

sequence from high pressure to low pressure, so that the drain water can flow smoothly

inside the system. Relevant requirements in the “Tentative Design Technical Regulations on

Prevention of large Shaft Bending Incidents for Water Entry into Steam Turbine” shall be

followed for designing the power station.

Pneumatic drain valves are used in the drain system, to achieve an automatic control

function via DEH control system. HP drain valve is closed at 10% load, IP drain valve is shut

at 20% load, and LP drain valve is turned off at 30% load.

Bypass System:Steam turbine bypass system is one of the important external systems of this unit. It has the

functions for improving unit start-up performance, reducing loss of turbine service life, and

rapidly tracking load, etc. A rational layout of bypass system can cater to the unit start up

through IP casing mode. This unit bypass system is the bypass system with 2-stage series

bypass plus the 3-stage pressure reducer and attemperator of 45% B-MCR capacity.

HP bypass steam is directed out from before the HP Main Stop Valve and extracted into

reheating cold Leg after 1st stage pressure and temperature reduction; while LP bypass

steam is led out from before IP combined steam valve and extracted into condenser after 2nd

stage and 3rd stage pressure and temperature reduction.

Vacuum System:The vacuum system in steam turbine is composed of condenser, condensation pump, and

air extractor. Its function is to maintain turbine operation under certain working

backpressure, and at the same time send the condensate water back to boiler for thermal

circulation. The method for gravity flow stage by stage is adopted for extracting the non-

condensed gases in LP heater, into condenser, and ultimately discharged by air extractor in

condenser into the atmosphere.

Mechanical vacuum pump system is used in this unit.

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It covers mechanical vacuum, condenser, and condensate water pump as well as the

pertaining valves and pipes.

The air in the vacuum system consists of two parts. One part is the limited quantity of air

contained in steam and content of this part air is up to unit deaerating effect. The other part

is the air in atmosphere leaked into the vacuum section of unit through untight areas. The

size of air suction volume depends upon the unit vacuum tightness. Therefore, when unit is

installed at power plant, tightness inspection shall be performed for all the welds and flange

joints of the vacuum system, to ensure that there is no leakage.

The tightness test is to be conducted once a month after the unit is put into operation. It is

required that the vacuum level should not drop at a speed exceeding 276Pa/min after

shutdown of air extractor.

Non-condensed gases in the steam seal system shall be extracted by shaft seal fan and

discharged into atmosphere, and they are not allowed to be admitted into the end part of

water jet air ejector, to avoid vacuum system from being affected.

All the valves shall be water sealed and flange connection for piping should be avoided as

much as possible, to guarantee a tightness of vacuum system.

Lube Oil System:The lube oil system plays the function for supplying unit bearings with lube oil and

emergency tripping device with pressure oil, and at the same time providing oil for turning

gear operation device and jacking device. Hydrogen sealing oil for generator is also

purveyed by this system.

The working medium adopted by the oil system is ISO: VG32 turbine oil and its quality must

comply with the requirements of GB7596-87 “machine oil quality standard for steam

turbine in operation used by power plants”.

This system adopts the traditional turbine rotor directly driven main oil pump-oil injector

system. Oil used for bearings is supplied by oil injector, whereas power oil for oil inject is

provided by main oil pump.

Main oil pump oil delivery is divided into two lines, one way leading to the security system

for emergency tripping device oil injection test, and the other opening to the oil injector.

One line of main oil pump oil admission inlets is used to supply pressure oil to security

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components. Two oil injectors are available, one for lube system oil supply and the other for

main oil pump inlet oil feed.

This unit oil system has adopted integrated oil tank and full suite oil piping technology. One

AC lube oil pump, one DC accidental oil pump, and one smoke exhaust fan are mounted on

the top of integrated oil tank, and two oil injectors and one set of spill valve are fitted inside

the tank. The integrated oil tank facilitates installation and operation of oil system in a

compact equipment structure, having improved the operational security and reliability.

Suite-type oil piping connection is adopted between bearing boxes and integrated oil tank. A

large-calibre pipeline can serve both as protection outer shell for internal pressure oil line,

and as oil return line from different bearing boxes to the integrated oil tank, thus to either

prevent high-pressure oil from leakage and to enhance fire-control security, or to enable a

compact oil piping layout and to save space.

Except #1 and #2 tilting-pad bearings in the steam turbine generator unit, all the rest

bearings are equipped with HP jacking device. Plunger pump is used as jacking oil pump and

oil is supplied to bearings through diverter and one-way throttling valve.

The system has two oil coolers of 100% capacity, (one in use and the other standby). Bearing

lube pressure ranges between 0.08MPa~0.12MPa, and lube pressure can be adjusted

through spill valve.

All bearing oil inlets are set with throttling pore plates. Return oil of bearings and security

system flows back into oil tank through oil mother pipe.

Pressure oil line in the oil system shall not have any partially raised places, to avoid

fluctuation of oil pressure and vibration of oil pipe arising from the storage air. In piping

arrangement, dead angles easy for air storage shall be avoided as much as possible or set

with air-bleed holes. Enable AC lube oil pump before starting the unit, to fill the pressure oil

pipe with oil slowly, so that the air is wholly driven away.

Hydrogen sealing oil for generator is provided by lube oil system after oil cooler.

Prior to start up, oil is supplied to bearings and hydrogen sealed pump via AC lube oil pump,

and part of this oil enters the oil line before main oil pump inlet, and flows out through oil

injector via main oil pump. Clean up the system and exhaust the air, to keep away from the

rise in oil temperature inside main oil pump during charge.

AC lube oil pump is used to provide lube to bearings during oil pumping circulation, start up,

shutdown, and turning gear operation prior to unit start up. When main oil pump outlet oil

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pressure has reached the requirement for lube oil pressure, the oil feeding switchover

between main oil pump and AC lube oil pump will complete. When the unit is confronted

with some failure during operation and lube oil pressure drops, the system can

automatically start up to maintain a necessary lube pressure.

DC lube oil pump is used to supply oil to lube oil system when lube pressure has dropped to

0.039MPa, to cater to a safe shutdown of the unit.

The Energy Conversion Processes :Electrical energy generation using steam turbines involves three energy conversions, extracting thermal energy from the fuel and using it to raise steam, converting the thermal energy of the steam into kinetic energy in the turbine and using a rotary generator to convert the turbine's mechanical energy into electrical energy.

Operation and Maintenance:When warming up a steam turbine for use, the main steam stop valves (after the boiler) have a bypass line to allow superheated steam to slowly bypass the valve and proceed to heat up the lines in the system along with the steam turbine. Also, a turning gear is engaged when there is no steam to the turbine to slowly rotate the turbine to ensure even heating to prevent uneven expansion. After first rotating the turbine by the turning gear, allowing time for the rotor to assume a straight plane (no bowing), then the turning gear is disengaged and steam is admitted to the turbine, first to the astern blades then to the ahead blades slowly rotating the turbine at 10 to 15 RPM to slowly warm the turbine.Problems with turbines are now rare and maintenance requirements are relatively small. Any imbalance of the rotor can lead to vibration, which in extreme cases can lead to a blade letting go and punching straight through the casing. It is, however, essential that the turbine be turned with dry steam - that is, superheated steam with a minimal liquid water content. If water gets into the steam and is blasted onto the blades (moisture carryover) rapid impingement and erosion of the blades can occur, possibly leading to imbalance and catastrophic failure.Also, water entering the

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blades will likely result in the destruction of the thrust bearing for the turbine shaft. To prevent this, along with controls and baffles in the boilers to ensure high quality steam, condensate drains are installed in the steam piping leading to the turbine.

Speed regulation:The control of a turbine with a governor is essential, as turbines need to be run up slowly, to prevent damage while some applications (such as the generation of alternating current electricity) require precise speed control.[11] Uncontrolled acceleration of the turbine rotor can lead to an overspeed trip, which causes the nozzle valves that control the flow of steam to the turbine to close. If this fails then the turbine may continue accelerating until it breaks apart, often spectacularly. Turbines are expensive to make, requiring precision manufacture and special quality materials. During normal operation in synchronization with the electricity net powerplants are governed with a five percentdroop speed control . This means the full load speed is 100% and the no load speed is 105%. This is required for the stable operation of the network without hunting and dropouts of powerplants. Normally the changes in speed are minor . Adjustments in power output are made by slowly raising the droop curve by increasing the spring pressure on a centrifugal governor. Generally this is a basic system requirement for all powerplants because the older and newer plants have to be compatible in response to the instantaneous changes in frequency without depending on outside communication.

Practical Machines : Steam turbines come in many configurations. Large machines are usually built with multiple stages to maximise the energy transfer from the steam.

To reduce axial forces on the turbine rotor bearings the steam may be fed into the turbine at the mid point along the shaft so that it flows in opposite directions towards each end of the shaft thus balancing the axial load.The output steam is fed through a cooling tower through which cooling water is passed to condense the steam back to water.

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Three stages steam turbines

Turbine power outputs of 600MW IN electricity generating plants in one unit.

The turbines used for electric power generation are most often directly coupled to their generators. As the generators must rotate at constant synchronous speeds according to the frequency of the electric power system, the most common speeds are 3000 r/min for 50 Hz systems, and 3600 r/min for 60 Hz systems. Here use 3000 r/min and 50 Hz.

Other application::

1: Marine propulsion

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The Turbinia - the first steam turbine-powered shipAnother use of steam turbines is in ships; their small size, low maintenance, light weight, and low vibration are compelling advantages. A steam turbine is only efficient when operating in the thousands of RPM, while the most effective propeller designs are for speeds less than 100 RPM. Therefore precise (thus expensive) reduction gears are generally used, although several ships, such as Turbinia and RMS Titanic, had direct drive from the steam turbine to the propeller shafts. The purchase cost is offset by much lower fuel and maintenance requirements and the small size of a turbine when compared to a reciprocating engine having an equivalent power. However, diesel engines are capable of higher efficiencies: steam turbine cycle efficiencies have yet to break 50%, yet diesel engines routinely exceed 50%, especially in marine applications.

1. Nuclear-powered ships and submarinesNuclear-powered ships and submarines use a nuclear reactor to create steam and either use a steam turbine directly for main propulsion, with generators providing auxiliary power, or else employ turbo-electric propulsion, where the steam drives a turbine-generator set with propulsion provided by electric motors. Nuclear power is often chosen where diesel power would be impractical (as in submarine applications) or the logistics of refuelling pose significant problems (for example, icebreakers). It has been estimated that the reactor fuel for the Royal Navy's Vanguard class submarine is sufficient to last 40 circumnavigations of the globe – potentially sufficient for the vessel's entire service life.

2. LocomotivesA steam turbine locomotive engine is a steam locomotive driven by a steam turbine.The main advantages of a steam turbine locomotive are better rotational balance and reduced hammer blow on the track. However, a disadvantage is less flexible power output power so that turbine locomotives were best suited for long-haul operations at a constant output power.

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The turbine auxiliary devices are chiefly condenser, HP &LP heater,

deaerator, feed water pump, CW pump and condensate pump.

The function of the condenseris to condensate the turbine exhausted

steam into condensing water, build up and maintain high vacuum in turbine

steam discharge port.

The function of HP and LP heateris to heat boiler feed water with

different pressure extraction steam in the intermediate stages of turbine,

which avoid partial thermal loss of steam inside the condenser, and the unit

efficiency is increased.

The function of deaeratoris to deaerate the water in boiler to eliminate

the dissolved gas to avoid oxygen corroding the boiler, turbine and pipes.

The function of feed water pumpis to supply the deaerated water

stored in the feed water tank of the deaerator to boiler.

The function of CW pump is to provide water for cooling the turbine

discharged steam to the condenser.

The function of the condensate pumpis to extract the condensate water

in the condenser, convey it into the deaerator, the condensate water after

being deaerated is used as boiler feed water.

Condition For Steam Turbine Automatic Trip

IF turbine speed exceeds limiting value

Vacuum is lower than the limiting value offered by manufacturer

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Lube oil pressure falls below limiting value

EH oil pressure falls below limiting value

Axial displacement of rotor exceeds limiting value

Shaft vibration of turbine exceeds limiting value.

Babbitt metal temperature of bearing pad and thrust bearing pad exceeds limiting

value.

Manual shutdown in main control room.

Tripping through DEH.

Generator cooling water flow low

Exhaust steam temperature of LP turbine is high

Hydrogen temperature of generator is high

Seal oil temperature of generator is high

Differential expansion exceeds limiting value

II. The Features of the Multi-stage Turbine

COMPARISION OF SINGLE STAGE AND MULTI STAGE TURBINE.

1. Merits:

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Compared to the single-stage turbine, the multi-stage turbine has the following

merits:

(1) As the stage is so many, the decrease of the enthalpy drop of each stage will

make each stage work within the range of the optimum speed ratio.

(2) The residual velocity of the front stage can be used by the next stage.

(3) The loss of the front stage of the multi-turbine will make the enthalpy of the back

stage hoist, and make the sum of the ideal enthalpy drop of each stage larger than the total

ideal enthalpy drop.

(4) The multi-stage turbine can be designed in the regenerative type and the reheat

type, to raise the circulating thermal efficiency.

(5) As the parameter is high, and the power is large, at the same time in raising the

economical efficiency, it also reduces the manufacturing and the operating expenses per KW

capacity.

2. Shortages:

Though the multi-stage turbine has the above merits, it also has some shortages,

which mainly are:

(1) The structure is complex; the parts are so many; the size of the turbine is large;

the weight is heavy; the total manufacturing cost is high.

(2) As the structure and the working features, the multi-stage turbine will produce

some additional losses, e.g. the damp loss of the final stages.

Energy Safety Note!

Never play around a transformer. If a ball or toy lands in or near a transformer,

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go and tell your parents to call the electric company. The electricity from a transformer could kill you. Never fly a kite around electrical lines. The kite string could link across the wires, completing a circuit. The electricity could be transferred back to you holding the string. Never let a balloon - especially a mylar foil balloon - escape into the sky. When the helium of the balloon escapes, the balloon can come down a long way aways. The wire or the mylar surface could stretch across high voltage electrical wires causing problems or even a fire. You should never touch wires inside or outside your house. You should only let an electrician who knows electricity safety work on the wires.

Thankyou