Erection Steps-STG 57.5 MW

8/13/2019 Erection Steps-STG 57.5 MW

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PRESENTATION ON CONSTRUCTIONAL

FEATURES OF 57.02MW

STEAM TURBINEAT AES KELANITISSA

BY

G.SRIDHARDEPUTY MANAGER/BHEL

www.bhelpswr.co.in/Technical/Commissioning%20Status/.../STGCF.ppt


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STEAM TURBINE

Single shaft non-reheat type reaction Turbine

1ststage is an impulse stage

Steam enters the turbine from the valves throughthe inter-connecting piping to the HP stages

17 HP stages

After the doing work in the HP stages, the steam

makes its way to the IP stages The IP stages are housed in Guide Blade

Carriers(GBCs) 1, 2, 3 & 4


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GBC-1 consists of 13 stages




The last 4 stages are housed in the Exhaust Hood

and are called the LP stages.

A very important part of the rotor is the Balance

Piston Disc/Drum which balances a major part of

the thrust that is caused by impingement of steamon to the blades. The residual thrust is absorbed by

the Thrust Bearing.


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In between the 2 bearing pedestals and the casingsare the front and the rear glands. Gland steam for

sealing the motive steam from coming out of thecasing is supplied to these glands.

The exhaust hood is provided with 2 nos. ofexplosion/bursting diaphragms which will operate

when the exhaust hood pressure increases beyond acertain limit. The diaphragm is made of lead.

On either side of the Turbine are the Main SteamStop and Control Valves with servomotors. Steam

from the Boiler enters the valves through a nozzleprovided at the bottom of the valves. The valveshouse the strainer which prevents foreign particlesfrom entering the Turbine.


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From the valves, the steam is led to the Turbine

through the Inter-connecting piping/Steam transfer

piping.

Looking from the Turbine towards the Generator,

all that is in front, is front and that at the rear, the

rear. Similarly the left and the right. The valves are fixed at the rear end in the axial

direction and at one of the resting palms in the

transverse direction thus enabling expansion of the

valve towards the front and away from the Turbinelaterally.

The rear set of thrust pads are the active pads.


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The Rear Bearing pedestal houses the rear bearing

and the Turning/Barring Gear assembly. The

coupling portion of the Turbine rotor is assembledwith 1 stage of impulse blades on to which oil will

impinge when the Turning Gear valve is opened.

This will result in rotation of the rotor. For this the

rotor has to be lifted on jacking oil by 0.07 to0.10mm.

Unlike the front bearing housing, the rear bearing

housing does not slide. The rear bearing pedestal is also the house of the

Turbine-Generator coupling.


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The Steam Turbine is equipped with the

following auxiliaries:

a. Main Oil Tank

b. Auxiliary Oil Pump-tank mounted

c. Emergency Oil Pump-tank mounted

d. Duplex Oil Filtere. Oil Coolers

f. Oil Centrifuge

g. AC & DC Jacking Oil Pumpsh. CEPs, BFPs, Deaerator etc.


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Sequence of Steam Turbine Erection

1. Mark the longitudinal and transverse center lines

on the TG deck/verify the center lines markedby the civil agency.

2. The foundation shall be checked for dimensionalaccuracy by a measuring tape within a tolerance

of +2mm.3. Before the foundation is cast, check the location

of inserts, pockets etc. The foundation boltsleeves shall be checked for verticality and shall

not deviate by more than 3mm along the entireheight of the sleeve. The sleeves shall then belocked firmly to the reinforcement rods to arrestany movement during casting.


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Care shall be taken to cast the entire deck in onestretch spanning 24 to 36 hours.

The dimensional and verticality check shall berepeated after casting to check for any deviationsduring casting. After the minimum curing time ofthe deck has elapsed, its ready for erection. All

dimensional checks shall be carried out withrespect to the longitudinal axis of the Turbine andthe Condenser center line.

All areas where secondary grout is to be poured or

where primary packers are to be grouted shall beroughly chipped. This is important for adhesion

between the primary and the secondary grout.


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A bench mark for reference elevation of the TG center line

shall be transferred from the Boiler/any reference which

the civil agency has marked. The elevation of allcomponents of the Steam TurbineGenerator shall be set

w.r.t this bench mark.

Mark location of packers for placement of the Turbine

Front and Rear pedestals, Exhaust hood base plate, theGenerator sole plate and the Exciter sole plates.

Place, align, set elevation and level the packers and grout

with quick setting non-shrink cement. Cure the grout for as

long as the manufacturer of the cement recommends.

Packers shall be so placed to allow for provision of shims

for adjustment.


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48 hours after the packers have been grouted, they are

ready for loading of the equipment.

Place the Exhaust hood sole plates, the Turbine front andthe Rear Bearing pedestals. All the above shall be aligned

w.r.t the longitudinal and transverse axes of the Turbine.

The elevations of the parting planes of the bearing

pedestals shall be set w.r.t to the bench mark made earlier

and shall correspond to the machine center line.

Place the exhaust hood lower half on the sole plates.

Bolt the lower half of the Outer Casing with the Exhaust

hood lower half, while taking care to match the joint. The

joint shall be checked on either side with a dial gauge. The

outer casing bottom half rests on jack screws on the FBP.


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A piano wire is then stretched from a temporary structure

in front of the front bearing pedestal to a structure beyond

the rear bearing pedestal at the same elevation as that ofthe machine centerline and shall hence forth be regarded as

the longitudinal centerline of the machine.

The seal bore of the pedestals and the front & rear portion

of the casing shall be aligned w.r.t to the piano wire to anaccuracy of 0.10mm.

Place the top half of the outer casing and the exhaust hood

and bolt the two together. This assembly cannot be made

later as there is no space to tighten the bolts of the vertical

joint.

Remove the top half of the casing and place it on a level

surface at a convenient location.


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Level the rotor on the lifting beam and place therotor on bearings.

Clamp dial gauges to the rotor and achievecentering values of at the Turbine front and rearseal bore, at the front gland portion and the bellowlocation of the casing as has been recorded at

works. Insert exhaust hood radial keys.

Remove the rotor and place it back on the stands.

Insert eccentric pin assemblies of the BP Gland,Inner casing and GBCs.

Place the lower halves of BP Gland, Inner casingand all Guide Blade Carriers.


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Place the bottom halves of the BP Gland, Inner

Casing and all GBCs.

The rotor shall now be lifted with the axialcompensator(bellow) assembled and placed in

position.

Restricted entry to the area may be allowed and itmay be ensured that all personnel working on the

Turbine have emptied pockets.

Once the rotor is placed in position, the box-up

shall be completed with no interruptions at leastuntil the top halves of the BP Gland, Inner Casing

and all GBCs are placed.


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Place the top halves of the BP Gland, Inner Casingand all GBCs. Apply Steam Jointing Paste at the

parting plane. The usually recommended pastesare BIRKOSIT or STAG-B

Heat tighten the Inner casing parting plane bolts.

Tighten all other parting plane bolts as mentioned

in the bolt tightening protocol. It is important tofollow the sequence of tightening as given in thedrawing.

Remove all vertical dowel pins from the BP

Gland, Inner Casing and all GBCs. Tack weld those nuts which have not been heat

tightened.


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Place the outer casing top half and tighten the parting plane

bolts.

This completes box-up. Until this point, the entire weight of the front portion of the

casing had been transferred to the front bearing pedestal

vide jacking screws. Now, transfer the load of the casing

from the jack screws to the load bearing screw and pad

assembly in the FBP. Release the jack screw.

Recheck centering of the Turbine casing w.r.t after

transferring of load and in case of change, re-center the

casing to the original values.

Fill a sand-cement mixture into the foundation bolt sleeves,

carryout shuttering and grout the Front Bearing pedestal,

the Exhaust hood sole plate and the Rear Bearing Pedestal

with quick setting cement.


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48 hrs after grouting, tighten all foundation bolts of theTurbine FBP, EH and RBP to required values mentioned inthe drawing.

Align Generator rotor with the Turbine rotor.

A misalignment of +0.02mm radially and axially ispermissible.

Record free runouts of the Turbine and Generator rotors at

the journals and the coupling. Couple the Turbine and Generator rotors using the 4

auxiliary coupling bolts supplied and achieve runouts, thesame or with minor variation of free runout.

Ream and Hone the coupling bolt holes and machine thebolts so as to have a clearance of 0.02mm between the boltand the hole. Stretch the coupling bolts to the requiredvalue and record coupled runout again.


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While Reaming and Honning of the Turbine-Generator

coupling is in progress, Inter-connecting pipes between

valves and Turbine can be installed.

The Main Steam Inlet Insert is inserted through the outer

casing into an opening in the inner casing. The insert is

kept in position by ring nuts which are threaded on to the

outer casing.

Leakage of steam from the inner casing to the outer casing

is sealed by the U-sealing ring.

The inter-connecting pipes are supported by dampers and

supports extending from the valve block.

After welding and stress relieving of the inter-connecting

pipes is completed, the centering of the casing w.r.t the

rotor shall be checked.


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TURBOGENERATOR

The Turbogenerator supplied for this project is of

Air cooled type. 5 coolers have been supplied, ofwhich 1 shall be spare.

The Generator Stator rests on sole plates which are

welded at site to form an assembly.

The Generator rotor rests on 2 bearings, much like

the Turbine rotor.

The air gap of the Generator is adjusted by shims

provided underneath the bearing pedestals.

The air gap is set and the bearing pedestals are

dowelled.


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For alignment of the Generator rotor with the

Turbine rotor, the Turbine rotor is assumed to be

the reference rotor. The entire Turbogeneratorassembly is moved left/right and top/bottom to

achieve the desired alignment.

While carrying out the radial and axial alignment,

care shall be taken to fix the axial position of the

stator by measuring the axial clearances at various

locations.

The Generator rotor has 2 sets of fan blades, oneeach on the front and rear sides. These fan suck air

and discharge them into the stator for cooling of

the windings.


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The radial and axial clearances of the fan blades rings andthe end shields shall be maintained as per drawing.

After alignment of Turbine-Generator rotors, alignment ofExciter rotor with Generator rotor shall be done.

The Exciter rotor shall be axially aligned and swing checkcarried out. The swing check values for this Exciter shall

be


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The Zero position of the rotor is that position of rotorabout which, the float on either side of the thrust bearing isequal i.e; the rotor has been set at mid float. It is this

position of the rotor w.r.t which the Differential expansionprobe and the axial shift probe are set.

While Turbovisory works are on, thermal clearances onholding down bolts at various locations are to be made as

per drawings. On completion of Turbovisory works in the pedestals, the

bearing pedestals can be boxed-up.

The machine is now ready for Turning Gear operation.

Set rotor lift of 0.07 to 0.10mm by adjusting jacking oilpressure in each bearing and put the machine on TurningGear.

The machine is now set to receive steam.


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Erection Steps-STG 57.5 MW

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