Turbine system.ppt

7/22/2019 Turbine system.ppt

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25 October 2013 PMI Revision 00 1

STEAM

TURBINE


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Presentation Outline

Theory of Turbine

Turbine casing

Rotor & Blades

Sealing system & barring gear

ESVs, IVs and CVs

Coupling and Bearing


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Steam Turbine

A steam turbine is a mechanical device that extracts

thermal energy from pressurized steam, and converts it into

useful mechanical work.
http://en.wikipedia.org/wiki/Thermal_energyhttp://en.wikipedia.org/wiki/Steamhttp://en.wikipedia.org/wiki/Steamhttp://en.wikipedia.org/wiki/Thermal_energy


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Classification

Impulse turbine

Reaction turbine

Based on Compounding:

Pressure compounded

Velocity compounded


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Impulse Turbines An impulse turbine uses the impact force of the steam jet

on the blades to turn the shaft. Steam expands as it passes

through the nozzles, where its pressure drops and its

velocity increases. As the steam flows through the moving

blades, its pressure remains the same, but its velocity

decreases. The steam does not expand as it flows throughthe moving blades.


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Impulse Turbine


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Velocity compounded impulse

turbine


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Pressure compounded


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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.


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Reaction turbine


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RANKINE CYCLE


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GENERATOREXCITER

1 2 34 5 6

ESV1

CV1

CRH

IPSV1IPCV 1

CONDEN

FROM RH

LPBYPASS

TO LP HEATERS

HPT 1X17IPT2X12

LPT2X6

TURBINE LAYOUT


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TURBINE COMPONENTS CASING

ROTOR

BLADES

SEALING SYSTEM

STOP & CONTROL VALVES

COUPLINGS & BEARINGS

BARRING GEAR


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Turbine CasingsHP Turbine Casing outer casing: a barrel-type without axial or radial

flange. Barrel-type casing suitable for quick startup and

loading. The inner casing--- cylindrical , axially split. The inner casing is attached in the horizontal and

vertical planes in the barrel casing so that it canfreely expand radially in all directions and axially

from a fixed point (HP-inlet side).


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HP Turbine Casing


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IP Turbine Casing

The casing of the IP turbine is split horizontallyand is ofdouble-shell construction.

Both are axially split and A double flow innercasing is supported in the outer casing and

carries the guide blades. Provides opposed double flow in the two blade

sections and compensates axial thrust.

Steam after reheating enters the inner casingfrom Top & Bottom.


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LP Turbine Casing

The LP turbine casing consists of a double flow unit

and has a triple shell welded casing. The shells are axially split and of rigid welded

construction. The inner shell taking the first rows of guide

blades, is attached kinematically in the middle

shell. Independent of the outer shell, the middle shell, is

supported at four points on longitudinal beams. Steam admitted to the LP turbine from the IP

turbine flows into the inner casing from both

sides.


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LP Turbine Casing


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Anchor Point of TurbinePurpose: Taking care of thermal expansions and

contractions of the machine during thermal cycling.

The fixed points of the turbine are as follows:

The bearing housing between the IP and LP turbines.

The rear bearing housing of the IP turbine. The longitudinal beam of the I.P turbine.

The thrust bearing in rear bearing casing of H.Pturbine.


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RotorsHP Rotor:

The HP rotor is machined from a single Cr-Mo-V steel

forging with integral discs.

In all the moving wheels, balancing holes are machined to

reduce the pressure difference across them, which resultsin reduction of axial thrust.

First stage has integral shrouds while other rows have

shroudings, rivetted to the blades are periphery.


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IP Rotor

The IP rotor has seven discs integrally forged with rotorwhile last four discs are shrunk fit.

The shaft is made of high creep resisting Cr-Mo-V steelforging while the shrunk fit disc are machined from high

strength nickel steel forgings. Except the last two wheels, all other wheels have

shrouding riveted at the tip of the blades. To adjust thefrequency of the moving blades, lashing wires havebeen provided in some stages.


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LP Rotor

The LP rotor consists of shrunk fit discs a shaft.

The shaft is a forging of Cr-Mo-V steel while the discs are of high

strength nickel steel forgings.

Blades are secured to the respective discs by riveted fork root

fastening. In all the stages lashing wires are providing to adjust the frequency

of blades. In the last two rows satellite strips are provided at the

leading edges of the blades to protect them against wet steam

erosion.


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BLADES

most costly element of turbine

blades fixed in stationary part are called guide

blades/nozzles and those fitted in moving part are

called rotating/working blades.

blades have three main parts

Aerofoil: working partRoot

Shrouds shroud are used to prevent steam leakage & to guide

steam to next set of moving blades.


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BLADES Three types of root arrangements are commonly used. They are (1)

T-roots: for small blades; (2) Fir Tree or serrated roots - for longer

blades; (3) Fork and Pin root: for longer blades shrunk on disc type

rotors.

Integral shroud for are used for shorter blades and shrunk fitting

for larger blades. Lacing wires are also used to dampen the vibration and to match

frequencies in the longer blades.

Since in the reaction type machine the pressure drop also occurs

across the moving blades it is necessary to provide effective

sealing at the blade tips.


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http://en.wikipedia.org/wiki/Image:Dampfturbine_Laeufer01.jpg


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SEALING GLANDS

Steam is supplied to the sealing chamber at 1.03 to 1.05Kg/sq.cm abs and at temperature 130 deg.C To 150deg.C from the header.

Air steam mixture from the last sealing chamber is

sucked out with the help of a special steam ejector togland steam cooler.

Provision has been made to supply live steam at thefront sealing of H.P. and I.P. rotor to control thedifferential expansion, when rotor goes under

contraction during a trip or sharp load reduction.


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Labyrinth seal


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BEARINGS:

General bearing---6no.s

Thrust bearing ---1no.

Bearings are usually forced lubricated and have

provision for admission of jacking oil


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Front Bearing Pedestal

The Front Bearing Pedestal is located at the turbine sideend of the turbine generator unit.

Its function is to support the turbine casing and bear theturbine rotor.

It houses the following components

a. Journal bearing

b. Hydraulic turning gear

c. Main oil pump with hydraulic speed transducer

d. Electric speed transducer

e. Over speed trip

f. Shaft vibration pick-upg. Bearing pedestal vibration pick-up


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The bearing pedestal is aligned to the foundation by means

of hexagon head screws that are screwed in to it at severalpoints.

The space beneath the bearing pedestal is filled with non

shrinking grout.

The bearing pedestal is anchored at to the foundation by

means of anchor bolts. The anchor bolt holes are filled with gravel,it gives a

vibration damping effect.


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Bearing Pedestal(HP Rear)

The Bearing pedestal(2) is located between the HP and IP

turbine.

Its function is to support the turbine casing and bear the HP

IP rotor.

It houses the following components1. Combine Journal and Thrust bearing

2. Shaft vibration pick-up

3. Bearing pedestal vibration pick-up

4. Thrust Bearing trip(electrical)


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Combined Journal and Thrust Brg.

The magnitude and direction of axial thrust of the turbine dependson the load condition

The Journal bearing is elliptical sleeve bearing.

The bearing liners are provided with a machined babbit face.

Located at each end of bearing shell, babbitted thrust bad forms 2

annular surfaces. These collars and thrust pads permit equal loading of thrust

bearing.

Thrust pads are of tilting type.

Metal temperature of the journal bearing and thrust pads is

monitored by the thermocouples.


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JOURNAL BEARING


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25 October 2013 PMI Revision 00 42JOURNAL BEARING


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IP Rear Bearing PedestalArrangement:The bearing pedestal is located between the HP and IP turbines.

Its function is to support the turbine casing and bear the HP and IP turbine

rotors. The bearing pedestal houses the following turbine components:

Journal bearing

Shaft vibration pick-up Bearing pedestal vibration pick-up

Hand barring arrangement

Differential expansion measurement device


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Journal Bearing

The function of the journal brg.is to support the turbine rotor.

The journal brg. Consists of the upper & lowershells,bearing cap,Spherical block, spherical support andkey.

The brg shell are provided with a babbit face.

Brg is pivot mounted on the spherical support to prevent

the bending movement on the rotor. A cap which fits in to the corresponding groove in the brg

shell prevents vertical movement of the brg shell.

The brg shells are fixed laterally by key.

Each key is held in position in the brg pedestal by 2 lateral

collar.


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The Temperature of the brg bodies is monitored by

thermocouple. Upper and lower shell can be removed without the removal

of Rotor.

To do this shaft is lifted slightly by means of jacking devicebut within the clearance of shaft seal.

The lower bearing shell can be turned upward to the topposition and removed.


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LP TURBINERear Bearing Pedestal: The bearing pedestal is situated between the LP

turbine and generator. Its function is to bear the LP rotor.

The bearing pedestal contains the following turbine components:

Journal bearingShaft vibration pick-up

Bearing pedestal vibration pick-up


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BARRING GEARThe primary function of barring gear is rotate

the turbo generator rotors slowly and continuously

During startup and shutdown periods when changes

in rotor temperature occurs

> Shaft system is rotated by double row blade wheel which is

driven by oil provided by AOPA manual barring gear is also provided with hydraulic gear

Barring speed 210/240 rpm


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ESV & CV2 main stop valves and 2 control valves located symmetrically

The main steam is admitted through the main steam inlet passing first the

main stop valves and then the control valves. From the control valves the

steam passes to the turbine casing.

Turbine is equipped with emergency stop valve to cut of

steam supply with control valves regulating steam supply

Emergency stop valve are actuated by servo motor

controlled by protection system

Control valves are actuated by governing system

through servo motors to regulate steam supply


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CouplingsShaft is made in small parts due to forging limitation

and other technological and economic reason,socoupling is required between any two rotors

Here using rigid coupling

Due to high torque flexible coupling cant be usedCoupling between

HP&IPIP&LPLP&generator

GEN&exciterMOP&HP


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THNAK YOU

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Turbine system.ppt