turbine system

7/31/2019 Turbine System

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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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A steam turbine is a mechanical device thatextracts 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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Impulse turbine

Reaction turbine

Pressure compounded

Velocity compounded


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An impulse turbine uses the impact force of thesteam jet on the blades to turn the shaft. Steamexpands as it passes through the nozzles, whereits pressure drops and its velocity increases. As

the steam flows through the moving blades, itspressure remains the same, but its velocitydecreases. The steam does not expand as it flowsthrough the moving blades.


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In the reaction turbine, the rotor blades themselves arearranged to form convergent nozzles. This type ofturbine makes use of the reaction force produced as thesteam accelerates through the nozzles formed by therotor.


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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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CASING

ROTOR

BLADES

SEALING SYSTEM STOP & CONTROL VALVES

COUPLINGS & BEARINGS

BARRING GEAR


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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 barrelcasing so that it can freely expand radiallyin all directions and axially from a fixedpoint (HP-inlet side).


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The casing of the IP turbine is splithorizontally and is of double-shellconstruction.

Both are axially split and A double flowinner casing is supported in the outercasing and carries the guide blades.

Provides opposed double flow in the two

blade sections and compensates axialthrust.

Steam after reheating enters the innercasing from Top & Bottom.


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The LP turbine casing consists of a double

flow unit and has a triple shell weldedcasing.

The shells are axially split and of rigidwelded construction.

The inner shell taking the first rows ofguide blades, is attached kinematically inthe middle shell.

Independent of the outer shell, the middle

shell, is supported at four points onlongitudinal beams. Steam admitted to the LP turbine from the

IP turbine flows into the inner casing from

both sides.


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Purpose: Taking care of thermal expansions

and contractions of the machine duringthermal cycling.

The fixed points of the turbine are as follows:

The bearing housing between the IP and LPturbines.

The rear bearing housing of the IP turbine.

The longitudinal beam of the I.P turbine.

The thrust bearing in rear bearing casing ofH.P turbine.


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HP Rotor:

The HP rotor is machined from a single Cr-Mo-Vsteel forging with integral discs.

In all the moving wheels, balancing holes aremachined to reduce the pressure differenceacross them, which results in reduction of axialthrust.

First stage has integral shrouds while other rows

have shroudings, rivetted to the blades areperiphery.


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The IP rotor has seven discs integrally forgedwith 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 aremachined from high strength nickel steelforgings.

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 somestages.


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The LP rotor consists of shrunk fit discs a shaft.

The shaft is a forging of Cr-Mo-V steel while the discsare of high strength nickel steel forgings.

Blades are secured to the respective discs by rivetedfork root fastening.

In all the stages lashing wires are providing to adjustthe frequency of blades. In the last two rows satellite

strips are provided at the leading edges of the blades toprotect them against wet steam erosion.


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most costly element of turbine

blades fixed in stationary part are called guideblades/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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Three types of root arrangements are commonly used.They are (1) T-roots: for small blades; (2) Fir Tree orserrated 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 andshrunk fitting for larger blades.

Lacing wires are also used to dampen the vibration andto match frequencies in the longer blades.

Since in the reaction type machine the pressure drop

also occurs across the moving blades it is necessary toprovide effective sealing at the blade tips.


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


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Steam is supplied to the sealing chamber at1.03 to 1.05 Kg/sq.cm abs and at temperature130 deg.C To 150 deg.C from the header.

Air steam mixture from the last sealing chamberis sucked out with the help of a special steamejector to gland steam cooler.

Provision has been made to supply live steam

at the front sealing of H.P. and I.P. rotor tocontrol the differential expansion, when rotorgoes under contraction during a trip or sharpload reduction.


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General bearing---6no.s Thrust bearing ---1no.Bearings are usually forced lubricated and have

provision for admission of jacking oil


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The Front Bearing Pedestal is located at theturbine side end of the turbine generator unit.

Its function is to support the turbine casing andbear 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 foundationby means of hexagon head screws that arescrewed in to it at several points.

The space beneath the bearing pedestal is filledwith non shrinking grout.

The bearing pedestal is anchored at to thefoundation by means of anchor bolts.

The anchor bolt holes are filled with gravel,itgives a vibration damping effect.


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Front Bearing Pedestal


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Front Bearing Pedestal


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The Bearing pedestal(2) is located between theHP 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-up4. Thrust Bearing trip(electrical)


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The magnitude and direction of axial thrust of theturbine 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 thrustpads is monitored by the thermocouples.


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JOURNAL BEARING


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JOURNAL BEARING


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Arrangement:The bearing pedestal is located between the HP and IP

turbines. Its function is to support the turbine casing and bear theHP and IP turbine rotors. The bearing pedestal houses thefollowing turbine components:

Journal bearing Shaft vibration pick-up Bearing pedestal vibration pick-up Hand barring arrangement Differential expansion measurement device


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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, sphericalsupport 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 groovein the brg shell prevents vertical movement ofthe brg shell.

The brg shells are fixed laterally by key.

Each key is held in position in the brg pedestalby 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 shaftseal.

The lower bearing shell can be turned upward tothe top position and removed.


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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-upBearing pedestal vibration pick-up


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The primary function of barring gear is rotate

the turbo generator rotors slowly and continuouslyDuring startup and shutdown periods when changesin 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 gearBarring speed 210/240 rpm


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2 main stop valves and 2 control valves located symmetrically

The main steam is admitted through the main steam inlet passing firstthe main stop valves and then the control valves. From the controlvalves the steam passes to the turbine casing.

Turbine is equipped with emergency stop valve to cut ofsteam supply with control valves regulating steam supply Emergency stop valve are actuated by servo motorcontrolled by protection system

Control valves are actuated by governing systemthrough servo motors to regulate steam supply


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Shaft is made in small parts due to forging limitationand other technological and economic reason,socoupling is required between any two rotors

Here using rigid couplingDue to high torque flexible coupling cant be usedCoupling between

HP&IP

IP&LPLP&generatorGEN&exciterMOP&HP


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turbine system

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