bme_unit2_lectures 11 & 12_steam turbine theory & construction_ppt

8/2/2019 BME_Unit2_Lectures 11 & 12_Steam Turbine Theory & Construction_PPT

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STEAM TURBINESSTEAM TURBINES


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What is Steam TurbineWhat is Steam Turbine

Steam turbine is a machineSteam turbine is a machinecapable of transformingcapable of transforming

thermal energy (from steam)thermal energy (from steam)to mechanical energy.to mechanical energy.OROR

Steam Turbine is a primeSteam Turbine is a primemover in which, heat energymover in which, heat energyis transformed intois transformed intomechanical energy.mechanical energy.


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Purpose of SteamPurpose of SteamTurbinesTurbines

Broadly speaking, Purpose of SteamBroadly speaking, Purpose of Steamturbines is divided into two broadturbines is divided into two broadcategories:categories:

Generating Electric PowerGenerating Electric PowerGeneral - Purpose units used forGeneral - Purpose units used fordriving pumps, compressors etc.driving pumps, compressors etc.

In both cases Steam Turbine will actIn both cases Steam Turbine will actas a prime mover.as a prime mover.


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Principle of WorkingPrinciple of Working

When Steam is passed through aWhen Steam is passed through anozzle, it expands (transformingnozzle, it expands (transformingpressure into velocity). This highpressure into velocity). This highvelocity (momentum) steam, whenvelocity (momentum) steam, whenimpinges on the blades, cause theimpinges on the blades, cause thewheel (rotor) to revolve.wheel (rotor) to revolve.


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Types of Steam TurbineTypes of Steam Turbine

Steam turbines are categorized by theSteam turbines are categorized by thefollowing three different ways:following three different ways:

From working principleFrom working principleImpulse TurbineImpulse TurbineReaction TurbineReaction Turbine

From number of steagesFrom number of steages

Single stage turbineSingle stage turbineMulti stage turbineMulti stage turbine


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Types of Steam TurbineTypes of Steam Turbine

From how steam is utilizedFrom how steam is utilizedCondensing turbineCondensing turbineBack pressure (non-condensing) turbineBack pressure (non-condensing) turbine

Extraction turbineExtraction turbineInduction turbineInduction turbine


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Impulse PrincipleImpulse Principle

If steam at high pressure is allowedIf steam at high pressure is allowedto expand through a stationaryto expand through a stationarynozzle, the result will be a drop innozzle, the result will be a drop insteam pressure and an increase insteam pressure and an increase insteam velocity. If the direction of thissteam velocity. If the direction of thishigh velocity steam changed byhigh velocity steam changed by

passing it through a properly shapedpassing it through a properly shapedturbine blade, will generate anturbine blade, will generate animpulse force. This impulse force willimpulse force. This impulse force will

cause the blade to move.cause the blade to move.


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Reaction PrincipleReaction Principle

When high pressure steam is allowedWhen high pressure steam is allowedto expand through a nozzle. It willto expand through a nozzle. It willproduce a reaction force in theproduce a reaction force in theopposite direction. Causing the bladeopposite direction. Causing the bladeto move.to move.


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http://en.wikipedia.org/wiki/Image:Turbines_impulse_v_reaction.png


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Single Stage TurbineSingle Stage Turbine

This type of turbine intakes and This type of turbine intakes andexpands the steam in a single row of expands the steam in a single row of nozzles and the kinetic (velocity)nozzles and the kinetic (velocity)energy of steam is converted into aenergy of steam is converted into amechanical one, by one or two rows of mechanical one, by one or two rows of buckets.buckets.

Single stage turbines are used mainlySingle stage turbines are used mainlyfor small output service, such asfor small output service, such asdriving a pump.driving a pump.


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Single Stage TurbineSingle Stage Turbine


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Multi-stage TurbineMulti-stage Turbine

A multistage turbine consists of a series of A multistage turbine consists of a series of stages arranged on a single shaft. It isstages arranged on a single shaft. It isdesigned so that each stage shares only adesigned so that each stage shares only a

part of the total pressure difference. Eachpart of the total pressure difference. Eachstage has a set of nozzle rows and bucketstage has a set of nozzle rows and bucketrows and is arranged in series to expand therows and is arranged in series to expand thesteam by turns.steam by turns.

These turbines are energy efficient and used These turbines are energy efficient and usedfor medium to large power service to drivefor medium to large power service to drive

large pumps, compressors and (electric)large pumps, compressors and (electric)


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Multi-stage TurbineMulti-stage Turbine


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Condensing TurbineCondensing Turbine

A condensing turbine intakes high-A condensing turbine intakes high-pressure steam and expands it fullypressure steam and expands it fullythrough the series of stages to vacuumthrough the series of stages to vacuum

and exhausts it to a condenser, whereand exhausts it to a condenser, whereit is condensed to water, instead of it is condensed to water, instead of being released to the atmosphere orbeing released to the atmosphere orlow pressure steam system.low pressure steam system.A condensing turbine require lessA condensing turbine require lesssteam than a back-pressure turbinesteam than a back-pressure turbinebecause the recovered energy from abecause the recovered energy from a

unit of steam can be maximized byunit of steam can be maximized by


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Condensing TurbineCondensing Turbine


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Back Pressure TurbineBack Pressure Turbine

A back pressure turbine (non-A back pressure turbine (non-condensing turbine) utilizes only a partcondensing turbine) utilizes only a partof high-pressure steam by expanding itof high-pressure steam by expanding itto an appropriate level of pressureto an appropriate level of pressure(low pressure or medium pressure(low pressure or medium pressuresteam). Remaining energy in thesteam). Remaining energy in the

exhaust steam will be utilized as aexhaust steam will be utilized as aheat source in the refinery.heat source in the refinery.


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Back Pressure TurbineBack Pressure Turbine


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Extraction / InductionExtraction / InductionTurbineTurbine

The Extraction Turbine, a part of the The Extraction Turbine, a part of theexpanding steam is extracted from theexpanding steam is extracted from theturbine casing at each connection andturbine casing at each connection and

supplied to the steam header of supplied to the steam header of intermediate pressure.intermediate pressure.

The Induction Turbine, intermediate The Induction Turbine, intermediatenozzles are provided to induce thenozzles are provided to induce theexcess steam from the steam headerexcess steam from the steam headerand expand it to the lower pressureand expand it to the lower pressurelevel.level.


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Extraction TurbineExtraction Turbine


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Parts of TurbineParts of Turbine

Exhaust HoodExhaust HoodGlands or SealsGlands or Seals

Rotor AssemblyRotor AssemblyBlades or bucketsBlades or bucketsDisksDisksShaftShaft

Other PartsOther PartsBearings (Radial & Thrust)Bearings (Radial & Thrust)

Turning Gear Turning Gear


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Purpose of GovernorPurpose of Governor

The purpose of Governor is to The purpose of Governor is tocontrol the speed of the turbinecontrol the speed of the turbine

according to the required load / setaccording to the required load / setpoint.point.Governor controls the speed of Governor controls the speed of

turbine by controlling the flow of turbine by controlling the flow of steam into the turbine.steam into the turbine.


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Types of GovernorTypes of Governor

There are several types of governors There are several types of governorsused in Steam Turbines.used in Steam Turbines.

Fly Ball GovernorFly Ball GovernorHydraulic GovernorHydraulic GovernorOil Relay GovernorOil Relay GovernorElectronic GovernorElectronic Governor


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Fly Ball GovernorFly Ball Governor

It consists of a fly ball and governorIt consists of a fly ball and governorspring. As the speed of turbinespring. As the speed of turbinechanges, the fly ball moveschanges, the fly ball movesoutward or inward because of outward or inward because of centrifugal force. This createscentrifugal force. This createstension in the spring that in turnstension in the spring that in turnsopens and closes the steamopens and closes the steamregulation valve.regulation valve.

This phenomena in shown in This phenomena in shown in

following figure.following figure.


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Hydraulic GovernorHydraulic Governor

It uses an oil pump in place of fly ball.It uses an oil pump in place of fly ball.An Oil pump is connected directly toAn Oil pump is connected directly tothe turbine shaft. As the turbine shaftthe turbine shaft. As the turbine shaft

speed changes, the discharge pressurespeed changes, the discharge pressureof the oil pump changes. Governorof the oil pump changes. Governorvalve is connected to a flexiblevalve is connected to a flexiblediaphragm. As the oil pressure ondiaphragm. As the oil pressure ondiaphragm changes, the Governordiaphragm changes, the Governorvalve opening changes as well.valve opening changes as well.

This governor is sensitive to This governor is sensitive to

temperature because of Oil.temperature because of Oil.


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Oil Relay GovernorOil Relay Governor

These governors combines the These governors combines thefeatures of both fly ball governor andfeatures of both fly ball governor andhydraulic governor. Oil pressurehydraulic governor. Oil pressure

operates the piston which is attachedoperates the piston which is attachedto the spring. The spring keeps theto the spring. The spring keeps thepiston in place until a change in oilpiston in place until a change in oilpressure acts on the piston. Fly ballpressure acts on the piston. Fly ballposition the pilot valve that controlsposition the pilot valve that controlsthe oil flowing through oil inlet and oilthe oil flowing through oil inlet and oiloutlet of the oil relay.outlet of the oil relay.

It is not sensitive to temperature asIt is not sensitive to temperature as


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Electronic GovernorElectronic Governor

In these Governors an ElectricIn these Governors an ElectricGenerator is attached to theGenerator is attached to the

turbine shaft to adjust the oil relay.turbine shaft to adjust the oil relay.Changes in the speed of shaftChanges in the speed of shaftchanges the output of the electricchanges the output of the electric

current. This change in the electriccurrent. This change in the electriccurrent adjust the pilot valve of thecurrent adjust the pilot valve of therelay.relay.


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Turbine ProtectionTurbine Protection

For the protection of turbine from overFor the protection of turbine from overspeeding, an over speed trip mechanism isspeeding, an over speed trip mechanism isprovided. This mechanism operateprovided. This mechanism operate

automatically if the speed exceeds theautomatically if the speed exceeds thedesigned limit.designed limit. The over speed trip pin assembly is The over speed trip pin assembly iscontained in the trip body mounted on thecontained in the trip body mounted on theturbine rotor shaft. When the turbine speedturbine rotor shaft. When the turbine speedexceeds the rated operated speed,exceeds the rated operated speed,centrifugal force exerted on the trip pincentrifugal force exerted on the trip pinincreases. As this force increases above theincreases. As this force increases above thetension in the s rin of tri in. The intension in the spring of trip pin. The pin


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Auxiliary SystemsAuxiliary Systems

Steam turbines are usually equippedSteam turbines are usually equippedwith following auxiliary systemswith following auxiliary systems

Lubrication systemLubrication systemSealing steam systemSealing steam system


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http://en.wikipedia.org/wiki/Image:Wirnik_turbiny_parowej_ORP_Wicher.jpg


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SteamNozzleStationar

y Blade

Movin

gBlade


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Lubrication SystemLubrication System

There are mainly two types of turbine There are mainly two types of turbinelubrication systemslubrication systems

Oil Ring Lubrication systemOil Ring Lubrication systemForced Lubrication SystemForced Lubrication System

First one is simple system thatFirst one is simple system thatemploys oil rings to deliver oil toemploys oil rings to deliver oil tothe turbine bearings.the turbine bearings.Second one employs a lubricationSecond one employs a lubricationpump to deliver oil to the turbinepump to deliver oil to the turbinebearings.bearings.


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BearingsBearings

Two types of bearings are mainly used Two types of bearings are mainly usedin the turbine,in the turbine,

Radial Bearing or Journal BearingRadial Bearing or Journal Bearing Thrust Bearing Thrust Bearing

Radial bearing is used to avoid radialRadial bearing is used to avoid radial

vibration (up & down vibration) of thevibration (up & down vibration) of theturbine shaft.turbine shaft.

Thrust bearing is used to avoid axial Thrust bearing is used to avoid axialmovement of the turbine shaft.movement of the turbine shaft.


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Start Up of TurbineStart Up of Turbine

Following are the main steps involvedFollowing are the main steps involvedin the start up of steam turbine,in the start up of steam turbine,

Lubrication system preparation & startLubrication system preparation & startupup

Turbine condensing system start up Turbine condensing system start up(optional)(optional)

Turbine sealing & vacuum system start Turbine sealing & vacuum system startup (optional)up (optional)Heating & pressurizing of steam linesHeating & pressurizing of steam linesand turbineand turbineProcess s stem re arationProcess s stem re aration

P i & P iP i & P i


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Preparation & PrecautionsPreparation & Precautions


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Monitoring ParametersMonitoring ParametersDuring OperationDuring Operation

Excessive Casing PressureExcessive Casing PressureCondensation of SteamCondensation of SteamQuality of SteamQuality of Steam

Bowing of ShaftBowing of ShaftHealthiness of the Instruments &Healthiness of the Instruments &FittingsFittingsVibrationsVibrationsContamination of the oil systemContamination of the oil systemSeals leakageSeals leakageCritical SpeedCritical Speed


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Shut Down of SteamShut Down of SteamTurbineTurbine

Following are the main steps involvedFollowing are the main steps involvedin the start up of steam turbine,in the start up of steam turbine,

Lowering of Speed to minimumLowering of Speed to minimumcontrollablecontrollableStop the turbine with shutdown pushStop the turbine with shutdown pushbuttonbutton

Isolation of the steam inlet and outletIsolation of the steam inlet and outletvalvesvalvesOpening of all drain pointsOpening of all drain pointsBarring of turbine for some timeBarring of turbine for some time

bme_unit2_lectures 11 & 12_steam turbine theory & construction_ppt

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