Turbine sysjerrbsteamturbinepptsmoltem.ppt

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STEAM
TURBINE

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Presentation Outline
•Theory of Turbine
•Turbine casing
•Rotor & Blades
•Sealing system & barring gear
•ESV’s, IV’s and CV’s
•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.

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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 through
the 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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GENERATOR
EXCI
TER
1 2 3
45 6
ESV
1
CV1
CRH
IPSV1IPCV 1
CONDEN
FROM RH
LPBYPASS
TO LP HEATERS
HPT 1X17
IPT
2X12
LPT
2X6
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 Casings
HP 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 can
freely 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 horizontally
and is of double-shell construction.
Both are axially split and A double flow inner
casing 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 casing
from 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 Turbine
Purpose: 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.P
turbine.

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Rotors
HP 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 results
in 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 rotor
while last four discs are shrunk fit.
•The shaft is made of high creep resisting Cr-Mo-V steel
forging 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 the
frequency of the moving blades, lashing wires have
been 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 part
Root
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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SEALING GLANDS
•Steam is supplied to the sealing chamber at 1.03 to 1.05
Kg/sq.cm abs and at temperature 130 deg.C To 150
deg.C from the header.
•Air steam mixture from the last sealing chamber is
sucked out with the help of a special steam ejector to
gland steam cooler.
•Provision has been made to supply live steam at the
front sealing of H.P. and I.P. rotor to control the
differential 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 side
end of the turbine generator unit.
•Its function is to support the turbine casing and bear the
turbine 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-up
g.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 several
points.
•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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Front Bearing Pedestal

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Front Bearing Pedestal

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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 components
1.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 depends
on 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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JOURNAL BEARING

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IP Rear Bearing Pedestal
Arrangement: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 & lower
shells,bearing cap,Spherical block, spherical support and
key.
•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 device
but within the clearance of shaft seal.
•The lower bearing shell can be turned upward to the top
position and removed.

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LP TURBINE
Rear 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 bearing
Shaft vibration pick-up
Bearing pedestal vibration pick-up

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BARRING GEAR
The 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 AOP
A manual barring gear is also provided with hydraulic gear
Barring speed 210/240 rpm

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ESV & CV
2 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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Couplings
Shaft is made in small parts due to forging limitation
and other technological and economic reason,so
coupling is required between any two rotors
Here using rigid coupling
Due to high torque flexible coupling can’t be used
Coupling between

HP&IP
IP&LP
LP&generator
GEN&exciter
MOP&HP

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