1. ASSEMBLY OF BEARING AT SITE

1.1. GENERAL DESCRIPTION

The KWU design machine are supplied with four bearings out of which three are

the journal bearing and one is combined thrust and journal bearing on H.P.

rear end of the shaft. All the turbine bearing are self aligning type and they

adjust themselves as per the catenary of the machine.

The function of a journal bearing is to support the turbine shaft , but the

thrust bearing support the shaft as well as work as a fix point for the turbine

shaft. The contact arrangements between bearing and bearing supports are of

two types i.e. sphere to sphere in HP front and HP rear bearing and torus to

cylindrical in other bearings.

The bearings are supplied to site after ensuring their contact at works. During

erection all the bearing are supplied to site in aligned and assemble condition in

their individual pedestal from the works. After alignment of the bearing in

their pedestal the seat of the bearing are doweled before dispatch to site.

In case of Thrust and Journal bearing the seat of the bearing neither doweled

from the works nor it is recommended to be doweled at site. The bearings

need preparation before placement of module in position at site. This can be

done even before the placement of pedestal in position for grouting.

1.2. ASSEMBLY PROCEDURE

1.2.1. After opening the pedestal remove and clean the bearing including its spherical/ cylindrical seat.

1.2.2. Remove oil guard ring and its duct and keep them in proper place for their storage at site.

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1.2.3. Handle bearing carefully to avoid any damage to the babbit and its torus/spherical piece. During storage at site avoid direct loading of bearing on its torus. A thick rubber seat may be used during handling of bearing at site on its torus.

1.2.4. Ensure 0.03 feeler tightness on bearing parting plane. In case of any variation the matter may be referred to designers.

1.2.5. Measure bore dia of the bearing and journal dia at site and ensure the oil clearances. If any discrepancy is observed , designer may be referred.

1.2.6. Ensure torus/spherical contact with their seats at site. While checking the contact the seat may be bolted with their pedestal. In case variation contact from their specified diagrams are noticed then following may be carried out at site:-

In case of torus to cylindrical seats the line contact are recommended by designers. If these lines are not straight and are in angle then the bearing may be rejected straight way and sent to works for rectification. These line contact may be in a width of about 20 mm throughout on its seat leaving with area on both sides. The contact may be wide in Center and then gradually reducing on sides. In case there is no contact is achieved in the center and only sides are having contact then a feeler gap may be recorded in bottom. In case if the bottom is tight to a feeler of 0.03 mm the bearing may be accepted at site without doing any rectification.

In a reverse case the contact are achieved in center only though the 0.03 feeler is not going in the side. The bearing may be still accepted at site. In case if the feeler is going in the bottom or in sides by 0.03 mm. the bearing are not accepted at site and can be sent back for the rectification to the works. Similarly if the contact are intermittent on its seat but in a straight line and no feeler is going the bearing may be accepted. In case of very wide contact also the bearing may be sent back for the rectification. While checking these contact very light color may be put on torus of the bearing. Before sending back the bearing to the works the matter may be referred to designers and their concurrence is to be obtained. No scrapping/lapping is recommended in these bearing for improvement of the contact.

In case of spherical to spherical bearing the contacts are called in the center like a moon shape. In these bearings even full contact may be accepted. But in case if there are contact on sides and a feeler gap is noticed on center then the bearing may not be accepted.

In such cases if the gap is upto 0.03 mm then the matching/lapping may be carried out at site. But in case of higher gap the matter may be referred to designers. In case of reverse case if the feeler gap of 0.03 is noticed on both sides of the bearing the bearing may not accepted at site and matter may be referred to designers.

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1.2.7. Before checking the contact between torus and its seat ensure that the seat is feeler tight to 0.03 mm without tightening of any bolts with the pedestal. If necessary this may be corrected with consultation of designers. Similarly ensure contact between torus\ spherical piece with bearing and in case of variation the matter be referred to designers and no correction is to be carried out at site without the approval of manufacturing unit.

1.2.8. Before checking the contact between torus/spherical piece with bearing and in case of variation the matter may be referred to designers and no correction is to be carried out at site without their recommendations.

1.2.9. The sizes of all the shims may be punched in bearing body and spherical/torus piece of the bearing. The number of shims are to be limited to 3-4 numbers only even after complete alignment of machine. A protocol for number of shims may be prepared.

1.2.10. Torus/spherical should not have any radial movement over its bearing. This can be seen after opening the torus from the bearing.

1.2.11. Check jacking oil lines of the bearing and clean them thoroughly. Ensure jacking oil lines fittings also for their male female threads etc otherwise this may create the oil leakage through these lines during operation of the machine. The jacking oil pocket in the bearing may be checked if necessary they may be corrected at site as per the drawings.

1.2.12. When ever JOP is not available, use always thick oil during rotation of shaft over bearing.The type of oil may be used as servo cylinder 1000 grade of IOC.

1.2.13. After installation of bearing in position the oil clearances may be checked after few rotation of the shaft. But the final oil clearances are to be checked after final coupling of the shaft. In case of variation in side oil clearances no cutting of babbitt metal is permitted at site. Any variation in clearances may be counter checked by measuring journal / bearing bore dia. Bearing bore dia is to be measured by assembling and tightening of top & bottom halves of bearing.

1.2.14. In case of skew side oil clearances, the investigation may be carried out, if necessary consult manufacturing unit.

1.2.15. Ensure good contact between journal and babbitt metal of the bearing in the center. Any minor high spot may be removed from the babbitt metal while checking with blue color. Ensure full contact of shaft over the jacking oil pocket also.

1.2.16. Always cover rotor journal with the upper half bearing to avoid entry of any sand particles etc. in the bearing . During pouring of oil the upper bearing may be removed and replaced back after the pouring of oil.

1.2.17. After completing the reaming/honing and final tightening of coupling bolts the work of bearing side pad, yoke keys and oil guard fitting may be taken up.

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1.2.18. Before starting the side pad and top keys ensure that the bearing is perfectly level on parting plane. Ensure that the gap for the side pads are parallel otherwise these are to be made by cutting/scrapping.

1.2.19. After fitting of the bearing cap if the gap for the radial top keys are in taper a proper correction is to be made here. The bearing cap may also be repositioned to achieve the parallelity of the key way. The cap may be re-doweled after repositioning it but no taper are to be left on these area. If repositioning of cap is not helping then the cutting may be carried out in bearing cap.

1.2.20. The gap for the top packer of bearing may also be checked. In case of any taper the same is to be corrected by cutting on bearing cap. Sometime the size of this packer comes to very low i.e. even below 5.00 mm. This may be corrected by matching the cap and size for this packer may be kept around 6.00 mm.

1.2.21. On all these bearing cap key a proper fitting and clearances are to be maintained during assembly. These key of proper material are to be only used and no welding deposits are permitted here. The new key may be made at site by EN-24 material if correct key are not available at site.

1.2.22. Use of local made shims in bearing may be avoided and shims supplied from the works with proper cutting of holes are to be used. Ensure drawing requirement of maximum adjustment at site by + 0.3mm in shim size from manufactured condition.

1.2.23. A proper care should be given during fitting of bearing oil guard ring otherwise it causes the oil leakage during operation of the machine through pedestals. Parting plane joint of oil guard ring and duct should be feeler tight and no elongation of holes on these area may be permitted.

1.2.24. The bearing parting plane bolt are to be tightened to required torque only no other method of tightening of these bolts may be used.

1.2.25. Adjustment of shims between spherical/torus and bearing body is limited to +0.30 mm in up and down and left, right direction. this margin may be left for emergency work during overhauling of the machine any adjustment during erection and normal overhauling may be done by adjusting shims between spherical/cylindrical seat and pedestal base only. For left and right adjustment the complete pedestal of HP front and HP rear may be moved with the help of their radial keys.

The above discussed points were common for Journal bearing and combined thrust and journal bearing. Now some specific points are detailed here for the assembly of combined Thrust and Journal bearing:

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Remove all the thrust pads before placement of bearing in

position and store them in a proper place.

Pressure proper fitting of babbitt metal liner in the bearing body

including necessary pinch in the fitting of its liner.

During alignment of rotor along the bearing with respect to the

shaft by moving spherical seat of the bearing radially and

axially.

No elongation of holes are to be carried out in spherical sat of

the bearing for the purpose of its alignment.

Before deciding axial position of the bearing the axial position of the

rotor is to be determined. If necessary the H.P. rear pedestal as a

whole may be shifted axially to ensure correct position of the

thrust bearing.

Align the thrust bearing in such a way that the thrust pad gap

achieved are prallel and no difference are noticed in front and rear

pad thicknesses.

Movement in the thrust pad should be ensured and a difference in

thickness of packers including shims should be with in + 0.10 mm

may be permitted on front and rear pad sizes in exceptional cases.

After ensuring the perfect alignment of the bearing the axial keys

are fitted after assembly of upper half bearing. These axial keys

are to be fitted in perfect parallel slots without any clearances.

The keys are to be fitted in such a way that there is no movement

to the bearing during fitting of these axial keys. Necessary dial

gauges are to be installed on bearing during fitting of these keys.

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After completion of axial key works of the bearing the thrust pads

may be fitted in the bearing with a clearance of about 0.10/0.15

mm.

Before fitting of pads in the bearing ensure that there dimension

are made parallel to suit the front and rear slot size of the bearing

(size between thrust collar and bearing body).

Ater fitting of pads in the bearing ensure their free movement

over the bearing.

Install lower half bearing in position along with their pads and put

very small quantity of oil on journal then rotate the rotor and put

blue color on the thrust collar of the rotor on both front and rear

side.

Install upper half bearing along with all pads and fix their axial keys.

Rotate the rotor and move + direction axially with the help of

wooden planks. Remove both halves of the bearing and see the

blue contact on thrust pads. If necessary some cutting may be

carried out on the pads to achieve the color contact. This

exercise may be repeated few times to achieve the blue contact

Ensure a float of 0.30 + 0.10mm during color matching of the

thrust pads. If necessary the minor adjustment of shims may be

carried out in the bearing pads.

Before installation of thrust bearing along with thrust pads in

position the both halves may be bolted out side and their pads

may be checked for color contact over a surface plate also in

front and rear both sides. This will reduce the time cycle while

carrying out the color contact of the bearing with the rotor.

During overhauling of the unit the bearing contact are to be

rechecked and need correction. In case of torus to cylindrical

type of bearing if the contact are not satisfactory then the

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bearing and its seat may be remachined at works. In spherical

to spherical bearing the variation in contact if noticed can

be corrected by matching/lapping at site. Sometimes the

heavy pitting marks are also noticed on same of the bearing and

these need correction by machining it.

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BUMP TEST

The axial clearance check is determined after radial clearance measurement has been completed.

In this case the shaft is shifted in the “+” and “-” directions from its operating position and the dimensions with the shaft in limit position are measured using a depth gauge.

Note: Enter the measured values ( actual dimensions ) on the record sheet and compare them with the specified dimensions.

If the deviations from the specified dimensions is greater then the permitted tolerances, the manufacturer must be consulted.

Note : Based on the readings of bump check, axial position of the shaft wrt casing is not to be altered.

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2. ROLL CHECK

2.1. GENERAL DESCRIPTION

In KWU machine the minimum radial clearances HP, IP and LP casing are

measured by actually by moving the casing radially at site while rotor is rotated

by hand. This is a very accurate and fast method of measuring the minimum

radial clearance of any of the casing.

The major variation in these reading may cause vibration in the machine

and obstruction in barring gear operation etc. Such facilities are not available

in many other designs of machine and causes longer duration in erection and

overhauling of the units.

After completing the alignment of rotors the casing alignments are carried out by

roll check method but equal importance should also be given to the centering of

HP and IP casing.

The centering of casing may not be fully sacrificed in comparison of rolling

test readings and a compromise between these two readings should be made.

The rolling test should be carried out in cold machine only.

2.2. PROCEDUREROLL CHECK OF HP AND IP CASING

2.2.1. Alignment and coupling of HP-IP and LP rotors are to be completed before starting the rolling test of the casing in normal case but this can be done without coupling of LP rotor also.

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2.2.2. Centering of the casing on HP front, HP rear IP front and IP rear spigot are also to be completed before starting of the rolling test. These readings can be compared as per the factory protocol also. Fix temporary radial and axial keys of the casing before rolling test of casing. During dialing on spigot a proper care should be taken that the dials are properly mounted over the fixture and the fixture fabricated at site is strong enough to give the correct readings. The point dial indicator may be used here for the better results of the dial readings.

2.2.3. All the four jacking screw of HP and IP casing are to installed along with dial gauges for monitoring of up and down, and left and right movement of the casing.

2.2.4. One number hydraulic jack on each corner of the casing along with a spanner on each corner for jacking screw are also to be made available.

2.2.5. During erection of machine the turbine rotor are generally rotated by hand with the help of periphery holes on coupling. Two pipes of about 1250 mm long along with a pin to suit the dia of periphery may be used for rotating the rotor shaft. The initial jerk to the rotor is given by the help of crane and it is further rotated by these pipes through periphery holes of the coupling. During overhauling generally the jacking oil system is available and the rotation of rotors are achieved with the hand barring of the machine.

2.2.6. Before starting the rolling check it should be ensured that the rotor shaft is absolutely free on manual rotation/hand barring as the case may be. During manual rotation two persons are to be employed for this work and during hand barring only one person is enough.

2.2.7. Always use thick oil for rotation of rotor over bearing in absence of jacking oil system. The type oil may be servo cylinder 1000 grade (IOC) oil.

2.2.8. During the rolling test the temporary casing packers are to be fitted with about 1.00 mm shims.

2.2.9. During the rolling test of any one of the casing the same is lifted first on all four corners in a step of 0.05 mm with the help of hydraulic jack and jacking screw. The rotor is also rotated manually side by side with the lifting of casing. The rotation of rotor and lifting of casing continued till it becomes little bit tight on the seals of the casing

After this the casing is lowered by about 0.05mm and rotor is

rotated again if it is completely free. In case the rotor is still tight on

its manual rotation the casing is further lowered by 0.05 mm on

all four corners. After ensuring the freeness of rotor it is again

rotated and casing is lifted simultaneously on front end till the

rotor rotation becomes tight on seals portion of the casing.

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As soon as the shaft becomes tight the lifting of casing and

rotation of shaft is stopped and dial readings on front end are

recorded. The average lift on front end of the casing is the bottom

clearance on front end of the casing.

After this the casing on front end is lowered by 0.05 mm and

freeness of rotor is ensured. In case it is still tight the casing is

further lowered by 0.05 mm. On front end and the freeness of

rotor is achieved. Now the rear end of the casing are lifted similar

to front end and bottom clearance of rear end are recorded . After

recording the bottom clearance of front and rear end of

individual casing the casing is lowered with the help of hydraulic

jacks and jacking screws to its original zero-zero position.

Repeat similar operation of rotating the rotor and lowering the

casing on front and rear end for deciding the top clearance in front

and rear end of the casing. Before starting the rolling test in

downward direction of the casing remove about 1.00 mm shims

from each packer of the casing, but kept the casing on

hydraulic jacks and jacking screws on its original position. The

casing is again brought back to its original position by

installation of the shims back to the packers of the casing after

recording the top clearances of the casing.

After recording the up and down rolling test values the radial

keys of the casing are removed and again rolling test for left

and right direction are done similar to up and down. During this

process the radial dial on the casing are also installed. After

this check the casing is brought back to its zero position in radial

direction also.

After completing the rolling test readings of one of the HP/IP

casing in up/downand left/right direction the clearances are

readjusted as required at site in radial direction by moving the

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casing with the help of temporary radial key or shims on the casing

packers. The casing is then locked on four corners and final

dial readings of spigot are recorded on front and rear end.

Immediately after this the final radial key of the casing are fixed

and the locked of the casing are released for fitting of the final

casing packers. The final spigot dial reading are repeated and

confirmed with the earlier readings.

2.2.10. After doing the full rolling test and fixing of a final radial keys and packers of one of the casing the rolling test of another casing is done including the fitting of final keys and packers.

2.2.11. Necessary offset in the radial clear-ance is also kept before fitting of final packers of the casing toward the lift of the shaft during operation of the unit.

2.2.12. No inlet and outlet pipes are to be welded with the casing till completion of rolling test and installation of final keys and packer of the casing.

2.2.13. Radial clearance of the casing are to be ensured with reference to the factory supplied protocol also.

2.2.14. After fitting of final keys and packers of the casing the final spigot dial values of HP front, HP rear, IP front and IP rear casing are to be recorded for future reference in the protocol.

2.2.15. The horn drop readings are also to be checked after the fitting of final packer of the casing.

2.2.16. In case of IP casing the roll test readings are to be taken with the IP front end rear shaft scales. The spigot dial readings are also to be taken over the spigot of shaft seales.

2.2.17. During rolling test of the HP and IP casing if the rotor is rotated over the jacking oil then the adjustment of readings are to adjusted for the lift of the rotor also.

2.2.18. Four numbers 1.00 mm undersize packers for HP & IP casing may be made during erection and supplied to customers as T&P items for further roll test during overhauling of the unit. If any taper is left on final packers of the casing then these four packers may be made to similar taper also.

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2.3. ROLLING TEST OF L.P. INNER CASING

2.3.1. The rolling test of L.P. inner casing is done similar to the HP or IP casing but both side joints of L.P. inlet bellows are kept free or bellow itself are not positioned at all, till completion of rolling test. But during overhauling the rolling test is done with already welded bellows.

2.3.2. Rolling test of L.P. inner casing is done after the neck welding of condenser andstiffener pipes inside the condenser. This include the welding of stiffener pipes of L.P. casing and gusset plates also.

2.3.3. After rolling test of the casing the final radial keys of the Gusset block and casing packers on all four corners are installed.

2.3.4. Necessary offset in the radial clearances of the casing is also kept before fitting of final L.,P. inner casing packers.

2.3.5. Radial clearances of the casing are to be ensured to the design values. In case of any variation the matter may be referred to the designers.

2.3.6. If the rotor is rotated on jacking oil then the rolling test readings are to be adjuted for the lift of the rotor also.

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3. CATENARY AND ALIGNMENTS

3.1. General Description

The catenary of the machine is very important for a turbine and Generator

assembly to achieve proper alignment of various rotors and loading on their

bearing. Any deviation may lead to various operational problem in the

machine like high shaft vibration, high bearing vibration, high babbitt metal

temperature of the bearing etc. To avoid these problems it is necessary to

maintain the catenary of the machine during erection and subsequent

realignment/overhaul of the unit. Many times it is observed that though the

alignment of rotors are within limit but the catenary as a whole get deviated

from the prescribed design value of the machine. In order to avoid such

derivation a need is felt to devise a procedure which shall ensure rotors

alignment alongwith proper catenary of the machine.

During first few years of the operation of the unit the possibility to the

disturbance of the catenary are much more due to settlement of the foundation

frame.

In each overhaul of the unit the catenary of the machine is to be corrected.

The L.P. front and L.P. rear pedestal are directly grouted here without any

separate base plate. As such any correction on lifting or lowering. These

pedestals are not very convenient so if necessary the rotor may be lifted or

lowered with respect to pedestal seal bore and required catenary may be

achieved. In extreme cases these pedestals may be even regrouted during

major overhauls of the unit to correct the catenary of the machine.

3.2. Procedure

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3.2.1. Install a bench mark plate near L.P. rear pedestal as height of the machine center line with the consultation of civil Engrs at site. A plate of 200 m.m x 300 m.m size with 20 m.m thickness machined/ground on top side may be welded over a I Beam or a channel in level condition. This plate is to be installed very carefully as this will be a future reference for setting up the all elevation of the machine.

3.2.2. Record half bore error of all the four pedestals and confirm the readings with the factory records also. The half bore error may be checked in both upper half and lower half of the pedestal and same may be punched on both halves in left and right side for all future references of the machine.

3.2.3. During alignment of pedestal at the time of grouting with conbextra cement set the height of the pedestals as per required catenary of the machine considering +value for the half bore error of the pedestals. While setting the height of the pedestals it should be kept in mind that the height for the center of the pedestal bore are to be kept as per the catenary of the machine not the parting plane of the pedestal.

3.2.4. For better results four water level jar connected to each other with a polythene pipe may be installed on each pedestal. The D.M., water may be used here and leakage through polythene tubes should be avoided fully while making the connections. These jars may be fabricated at site by about 125 mm. dia pipe with a plate welded in bottom and then machined for better seating on pedestal base. The height of the jar may be kept as about 175 mm. A depth micrometer installed and clamped over a magnetic base is also required for measurement of the water level in the jar. The micrometer point is to be made very sharp by grinding it. Here the magnetic base of the 0-10mm dial gauge may be used.

3.2.5. .During measurement of water level in the jar the micrometer is to be kept approximately in center of the jar. The micrometer along with the magnetic base to be transferred from one pedestal to another pedestal very carefully so there is no disturbance to the height of the micrometer. All the necessary care are to be taken during this measurement i.e. there should not be any air bubble in the polythene pipe and the polythene pipe should be kept as stationary.

3.2.6. While finalizing the catenary of the machine these measurements are to be repeated 3-4 times in a day at different intervals to avoid any possibility of the error.

3.2.7. The height of the L.P. rear pedestal is the reference point for setting the height of all other pedestal and L.P. base plates. The L.P. rear pedestal height is to be first made with the benchmark plate as per the center line of the machine with the help of water level jar.

3.2.8. The benchmark plate is to be preserved for all future references.

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3.2.9. The catenary is to be counter checked after grouting all the pedestals as well as after final alignment of the rotors. The final value of the catenary may be worked out as center of the shaft on each pedestal bore after taking the final seal bore readings. The final catenary should match with the design value of the catenary otherwise a necessary correction may be carried out.

3.2.10. After ensuring the required catenary of the machine the coupling alignments are to be made as parallel coupling.

3.2.11. The value of the catenary given over the drawing are theoretical value calculated by the designers but due to the human error in site measurements some time the correct coupling alignment are not achieved then an alternate method for checking of catenary may also be used i.e. optical measurement method or a method by which direct journal heights are taken on each bearing in place of pedestal height.

3.2.12. For measurements of direct journal height a special fixture is to be fabricated and necessary information about it can be separately given by PS-TS if such necessity arises.

4. HORN DROP TEST

4.1. General description

By horn drop test the loading of the casing on each corner is determined. The

horn drop test is repeated at various stages in individual casing i.e. first

without connection of any pipe lines the horn drop readings are recorded then it

is compared after welding of inlet, outlet and extraction pipe lines etc. The horn

drop readings are very important in HP & IP casing. First the proper horn drop

readings are made without connection of any pipe lines and then the reading

are taken after welding of all pipe lines on HP & IP casing. As such the

influence of these major pipe lines are notices on each corner of HP/IP

casing by comparing the horn drop test readings. The horn drop test will

indicate the quality of work during assembly/welding of pipe lines with the HP &

IP casing.

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This is a very important check and may cause serious problem in operation of

the machine like high vibration in the machine failure of barring gear in hot/cold

machine, obstruction during expansion of machine etc. In horn drop test a drop

is measured on an individual corner of the casing with the help of a dial

indicator by removing the support of individual corner and then it is compared

with the opposite corner. As such this gives an indication of indifferent loading

of the casing. In Russian design machine the value of direct dynoxmetre

loadings are recorded in place of this horn drop test.

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4.1.1. Procedure

4.1.2. After placement of HP and IP casing on four temporary packers ensure that the each corner of the casing is loaded on temporary packer and if necessary the shims may be given on packer for loading of the casing. The load of shaft is also taken on transport device during this stage.

4.1.3. After transferring the load of the rotor on bearing and ensuring the casing centering with respect to shaft the horn drop check may be carried out.

4.1.4. Before taking the horn drop reading ensure that the enough clearance is available on front & rear portion of the shaft with their seals in the casing inside. After completing the centering of the casing the some may be lifted by 0. 20 mm on all four corners by providing shims. This will help in avoiding the touching of seals with the rotor during the horn drop test readings.

4.1.5. No adjustment on packer of the HP front and HP rear pedestals are to be carried out after taking the horn drop test of the casing In case if any adjustment is carried out on these pedestal packers then horn drop test are to be repeated again.

4.1.6. No piping may be connected to HP & IP casing till initial horn drop readings are over. The piping work should not be postponed for want of horn drop the only thing the last joint with HP/IP casing may be left free till completion of horn drop check.

4.1.7. While recording the horn drop readings the casing must be absolutely free and even the radial and axial key of front and rear portion of the casing are either to be removed fully or these are to be made completely free by removing their shims etc. Actually during this stage of erection only temporary axial and radial keys are fitted in the casing and even they carry some shims also. Before making the casings free on axial and radial key portion the dial gauges are to be installed to monitor the movement of the casing on radial and axial direction. Immediately after the completion of the horn drop test these keys/shims may be installed back and centering of casing may be rechecked before further works.

4.1.8. In HP casing the initial horn drop test may be done even after fitting of breach nut assembly and HP exhaust elbow of both sides.

4.1.9. In IP casing the initial horn drop test may also be done after fitting of IP inlet pipe lower half assembly but this pipe of upper half casing should not be fitted till completion of the horn drop test.

4.1.10. All the four Jacking screw and hydraulic jack on each corner of the casing are to be installed for the horn drop test readings. A dial indicator is also to be installed on each corner of the casing for measuring the drop of the casing.

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4.1.11. After initial centering of the casing the each corner packer may be fitted with a shim of about 1 mm. for further adjustment during the horn drop test.

4.1.12. During the horn drop test the individual packer of the casing is removed and the load of that corner is supported over the jacking screw of the casing. Now gradually the jacking screw is also relieved with the help of hydraulic jack on that corner and drop reading is recorded. This is repeated for each corner of the casing. In case of variation in left and right side reading the drop is adjusted by + adjustment of shims from left to right side or vise-versa. No subtraction / addition in shim sizes from outside is done here and only the shims are adjusted from left to right or vise versa till equal loading are achieved in left/right side of individual casing. The sizes of these casing packers are recorded after completion of horn drop to avoid any confusion at a later date while fitting the final packers.

4.1.13. While recording the horn drop readings the drop on each individual corner may be controlled with the help of Jacking screw so that during this test the casing is not touching with the shaft in gland portion of the seals at all and enough clearance is left there to avoid damage to the seals inside the casing.

4.1.14. During the initial horn drop the best reading within 0.05/0.06 may be achieved by fine adjustment of the packer shims. The comparison in horn drop value should always be made in left and right side only of an individual casing.

4.1.15. In case of HP casing the drop on rear end is so high that unless the casing is locked on diagonally opposite end the horn drop check is not possible. Therefore while recording drop on HP rear end the front end of the casing diagonally opposite to it should be locked with casing clamp. The pedestal is also required to be locked on all four side with its sole plate with the help of the clamps. In case of IP casing no locking of any corner of the casing is necessary during the horn drop test.

4.1.16. The final packers on HP & Ip casing are installed only after completing the rolling test of these casing., The horn drop reading for an individual casing may be recorded after the fixing of final packers also. If necessary a fine adjustment may be carried out at this stage to achieve correct value of the horn drop reading.

4.1.17. After completing the welding of all pipe lines with the casing , the horn drop readings are repeated again for comparison with the earlier readings. These readings are taken along with its radial and axial keys of the casing.

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4.1.18. During this stage exactly this can not be defined that how much variation is permitted on these values of horn drop readings., But this variation will indicate the influence of the piping load on the HP/IP casing caused due to welding/connection of various pipe lines with the casing. The variation in horn drop readings are permitted as long as sufficient positive loading is there on each corner of the casing. But if any corner of the casing is fully unloaded/heavily loaded then there is no choice left and pipe lines are to be corrected by dismantling it and making again a free joint with the casing.

4.1.19. During variation of horn drop reading no correction is to be made on casing packers by adjustment of shims etc. The variation at this stage is caused due to the piping pull/push only so if any correction is required then the same may be carried out in piping joints and support etc. And any adjustment in piping supports can be carried out only after disconnecting the pipe line with the casing. Even some time it is necessary to cut the individual or more piping joint for correction of horn drop readings.

4.1.20. The variation in horn drop reading of left and right side of a casing may be permitted upto a difference of 50%.

4.1.21. The horn drop readings are not taken for L.P. inner outer casing due to its fabricated structure and the parting plane of the casing are leveled on four corner with the help of water level jar arrangements.

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5. SWING CHECK

5.1. GENERAL DESCRIPTION

The swing check is the measurement of radial throw caused due to

coupling face geometric form of the two rotor coupled together. This is

measured on opposite end of the coupling and at the free end of the rotor. The

higher swing check value may cause higher shaft vibration, higher bearing

shell temperature etc. The value of swing check depends on axial runout of

coupling faces, the diameter of the coupling and the length of the rotor. During

the machining of rotors in the works some tolerances are permitted by

Designer's on the coupling faces of the rotor resulting to some swing check

values. The maximum swing check values permitted caused due to the

above tolerance for different diameter and length of the rotor can be

worked out from the enclosed graph. However it is recommended to keep the

minimum swing check values for better results during operation of the machine.

In a multi rotor Turbine-Generator system it is essential to measure the swing

check value in both extreme end and where the weight of the rotors are light.

For example 200/210 M.W. KWU machine with Russian Generator and

static excitation system the swing check values are measured on HP rotor front

end only. In 500 M.W. machine the swing check values are measured in H.P.

front end and on exciter rear end. After having general experience of number of

200 MW & 500 MW units, a necessity is felt to measure swing check value on IP

rotor front end also for better results during operation of the units. This can be

done initially during erection with temporary coupling bolts on LP-IP coupling

before reaming/honing of coupling. Any variation in swing check values may be

corrected without any hesitation during erection of machine. Any compromise

at erection stage may cause serious problem during operation of the unit and

any correction becomes much more tedious a later stage. The correction may

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be carried out either by interchanging the coupling position or by correcting

the coupling faces by scrapping/cutting in consultation of Designers.

5.2. PROCEDURE

5.2.1. Before placement of Module/Rotor in position the coupling faces of all the rotors are to be measured for concavity/convexity of their coupling faces. This can be checked with the help of a thin rectangular light weight straight edge. No convexity is permitted on these coupling faces however a concavity of about 0.03/0.04 mm is permitted. In case of any variation the matter may be referred to manufacturing units.

5.2.2. After placement of individual Module/Rotor the coupling faces are to be measured for axial runout before taking up alignment of various rotors. The HP rotor rear coupling face can be measured after placing it on both of its bearing. The IP rotor faces are to be measured after placing IP rear end on bearing and front end on lifting tackle. Similarly L.P. rotor, may be placed on bearing on its rear end and front end supported on lifting tackle. Any variation on axial runout on coupling faces for more then the 0.02 mm. may be referred to Designer's before taking up further works.

5.2.3. After completing final alignment of various rotor they are to be coupled with temporary bolts, considering their axial runout/geometric form of the coupling faces.

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5.2.4. During coupling with temporary bolts the higher plane of one of the rotor face is to be coupled with lower plane of another coupling face of the rotor.

5.2.5. During coupling on temporary bolts the uniform tightening on all the four temporary bolts are to be ensured otherwise it will disturb the swing check value of the rotor.

5.2.6. First IP-LP coupling is to be made with temporary bolts and swing check on IP rotor front end is recorded. After this only HP-IP rotor is to be coupled with temporary bolts and the swing check value on HP front rotor is recorded.

5.2.7. During swing check of IP rotor its front end is to be supported on lifting tackle without making any connection between HP-IP rotor.

5.2.8. While recording swing check of HP rotor the front end of the rotor is to be supported on lifting tackle.

5.2.9. During swing check the lifting tackle are to be fitted properly. The tie rod of lifting tackle should be ensured for correct fitting of its spherical bearing and Molykote should be applied on these spherical bearing for their free movement. These spherical bearing should not obstruct the movement of shaft radially during checking of its swing check value.

5.2.10. After taking the load of the rotor on lifting tackle ensure that the rotor is not disturb radially due to fitting of lifting tackle.

5.2.11. During checking of swing check measure radial movement of rotor on parting plane and rotate the rotor either on jacking oil with hand barring or with the help of E.O.T crane with thick oil on bearings. Avoid jerk during rotation of rotor while recording the swing check values.

5.2.12. After ensuring the swing check values as per the graph with on temporary coupling bolts, the HP-IP and LP-IP coupling may be cleared for reaming / honing of the coupling holes. Any variation need correction of the coupling before reaming/honing of the holes.

5.2.13. The final swing check value of HP front rotor is to be recorded after fitting/ elongation of all the coupling bolts of HP-IP & LP-IP rotors. Any variation in readings may be referred to the Designer's. For improvement of the swing check values, the indifferent tightening and non-sequential

5.2.14. During checking of swing check readings, the initial few rotations are to be given to the rotor to avoid initial sag and then only the readings are to be recorded.

5.2.15. Similar method is to be adopted while checking the swing check value of the exciter except the rotor is hanged on the suitable size of sling in place of the lifting tackle.

5.2.16. While recording the swing check initially with temporary bolts for HP & IP rotor, the fitting of eight number temporary bolts are preferred in place of four bolts on the coupling.

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COUPLINGS & ALIGNMENTS OF ROTORS

5.3. GENERAL DESCRIPTION

The coupling on turbine shaft are generally rigid coupling but in case of L.P.

rotor sometime the coupling head are shrunk fit and remachined. The basic

function of any coupling is to connect two or more shaft together to form a

shaft assembly. The number of shaft mainly depend upon the rating of the

machine.

A very high accuracy is required during manufacturing of these rotor shaft

at works. The axial runout on the coupling face may not exceed 0.02 mm.

and an additional check is also made at works/site to ensure that the geometry

of the entire coupling surface does not deviate by more then the 0.02 mm.

except the concavity on the coupling face which is permitted upto 0.03/0.04

mm.

The radial and axial alignment of the various shafts are to be completed

before their coupling and alignments are to be done in such a way that the

entire shaft assembly follow the continuous deflection curve given over the

drgs. for a particular machine. The coupling checks determines both the radial

and axial position of the two adjacent coupling flanges relative to one another.

The radial measurement are performed on the circumference of the

couplings and the axial measurement are performed on outer most diameter

of the coupling. During coupling of the two shafts it should be ensured that the

no stresses are exerted as a results of the coupling each other shaft.

After completion of the alignment and coupling of the shaft the casings are

aligned radially and axially. Here equal importance is given to the radial & axial

alignment of stationary parts to avoid any rubbing during operation of the

machine due to expansion of stationary and rotary parts.

During the alignment of two coupling both are to be turned in same direction

and by the same amount when the measurement are taken to avoid the

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influence of the axial & radial runout present in the shaft caused due to the

machining.

5.4. PROCEDURE

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5.4.1. Before placement of module/rotor in position check and record the coupling hole and journal dia of the shaft.

5.4.2. Check coupling faces for the concavity/convexity with the help of a thin rectangular straight edge before placement of module/rotor in position.

5.4.3. Check spigot and recess of the coupling and ensure their fitting before placement in position.

5.4.4. Place the module/rotor in position and check the radial runout of journal and axial runout of the coupling faces independently of each shaft. During checking of radial and axial runout of the shaft place H.P. rotor on both of its bearing and IP/LP rotor one end on its bearing and another end on the lifting tackle. The radial and axial face runout on the shaft should be within 0.02 mm accuracy. Any variation may not be permitted here and matter may be referred to the designer's.

5.4.5. The HP,IP & LP rotor are aligned together and then their couplings are made. After fully completion of HP/IP & IP/LP coupling with tightening of their final bolts the complete shaft is cleared for Generator rotor alignment.

5.4.6. During initial alignment of HP/IP & IP/LP rotor the radial checks are generally done with the help of depth micrometer and axial gap are measured with the slip gauges. After completion of the radial alignment the rotor are inserted in their spigot even with some minor variation in their axial gap values.

5.4.7. During final alignment only the axial gap values are checked at 90o on four places by rotating both the rotor together and average of these four reading are taken. The radial alignment reading along with axial gaps are necessary wherever the effective spigot are not existing in two couplings i.e. in case of LP - Gen coupling the radial dial reading are also taken.

5.4.8. Avoid rotation of two shaft in their spigot. If necessary these may be rotated after taking out from their spigot.

5.4.9. During alignment of shafts the adjustment of shims in bearing torus may be fully avoided. The margin of + 0.30 mm. in height & left/right direction may be kept for emergency works only. Any adjustment during erection and normal overhauling may be done by adjusting shims between spherical/cylindrical seat and pedestal base only. For left and right adjustment the complete H.P. front and HP rear pedestal may be moved with the help of their radial keys.

5.4.10. The final packers of the pedestal and base plates are fitted before the grouting of the pedestal itself and here no adjustment is necessary during erection of the machine. But during overhauling of the machine the adjustment may be carried out in these packers for correction of catenary of the machine.

5.4.11. During alignment of rotor make HP/IP and IP/LP coupling gap parallel. After completion of final alignment no adjustment of packers and keys etc are permitted on pedestals and bearing the final alignment of HP/IP & IP/LP rotors should be checked after fitting of all the final keys and packers of the pedestals.

Page No. 26 of 32

5.4.12. After alignment couple the HP-IP & IP-LP rotors on temporary bolts. Record coupled runout of the rotor and ensure that the coupled runout is not more then 0.03 mm. in any where in the journal as well as in coupling area. Before coupling of rotor on temporary bolts record their spigot clearances by actually moving the rotor radially.

5.4.13. During erection IP-LP swing check on IP front and HP-IP swing check on HP front are to be recorded on temporary bolts. These reading are to be ensured within the design limit.

5.4.14. Before alignment/coupling position the two shaft adjustment to each other depending upon the higher and lower point of the shaft with respect to their axial face measurement values.

5.4.15. The HP-IP & IP-IP coupling may be cleared for reaming/honing after ensuring the runout and swing check values of the rotors. In case of variation the cause of the error may be identified and corrected before further work of reaming and honing of the coupling.

5.4.16. During coupling of rotors two taper pins may be used for proper alignment of coupling holes so that there is minimum enlargement of holes are done at site during reaming/honing. Unnecessary enlargement of holes may be fully avoided during reaming/honing at site as this may cause serious problem at a later date during overhauling of the unit.

5.4.17. As for as possible ream/hone all the coupling bolts holes to same size. In exceptional cases only the variation in hole sizes are permitted. Each hole during honing should be checked for bananas shape with the help of a parallel ground straight pin of 0.02/0.03 undersize. No banana shape is permitted in any of the hole. The hole should be made to 0.005 mm accuracy.

5.4.18. All the coupling bolts are to be machined and ground by 0.02/0.03 mm undersize then the hole dia. These bolts are to be fitted with thumb pressure only and no additional force is recommended while fitting these bolts.

5.4.19. A very thin layer of molykote may be applied on all the coupling bolts during their fitting. The molykote should not be applied on seating face of the coupling bolts. This may cause in breaking of their locking pin during elongation of coupling bolts.

5.4.20. All the coupling bolts are to be balanced before finally fitting/tightening in position. These are to be balanced within an accuracy of 5 gms each along with their nuts. In case all these bolts are of equal size then their weight must be equal. In exceptional cases the 180o opposite bolts may be made of equal weight.

5.4.21. During tightening of coupling at any stage first tighten four bolts on 90o location. Always tighten bolts in proper sequence with 180o opposite bolts. These bolts are to be elongated to the value given over drgs.

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5.4.22. During tightening of coupling the radial runout on journal and coupling may be checked at various stages during tightening of bolts. The final coupled runout should not be more then 0.03 mm. on coupling and journal of the shaft.

5.4.23. After final tightening of LP-IP and HP-IP coupling the swing check value on HP front rotor is to be rechecked. In case of variation in value a proper correction is to be made with consultation of designer's. The indifferent or unsequential tightening for achieving the swing check value or coupled runout value may be fully avoided. this may cause unnecessary stresses on the coupling.

5.4.24. After completing the coupling work the casing radial and axial alignment may be done.

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Welding of steam inlet and exhaust pipe lines with HP and IP casing

In 210 MW machine the HP Turbine is supplied with two inlet and two exhaust

flanges for connection of the pipe line.but in case of 500/250 MW HP Turbine the

casing is supplied with four inlet flanges also. As such in 200 MW machines,

only two ESV control valves are used in the system. Whereas in 500/250 MW

machines , It may be either two ESV oontrol valves or four ESV control valves to

cope with the design of the casing.

Similarly in 210 MW machines, the I.P. casing is supplied with two inlet flanges

and eight number exhaust branches or either two exhaust branches only along

with two inlet flanges. These eight number exhaust branches are distributed four

on each side of the casing and each four branches are joined together with one

common pipe while connected to L.P. casing. The 500 MW I.P. casing is similar

to the 210 MW I.P. casing but some time these are supplied with four numbers

of I.V. control valves also. The inlet lines from each two control valves are joined

together and make one connection with the I.P. casing in bottom. As such in

210 MW machines, only two I.V. control valves are used but in case of 500 MW

machines, there can be either two I.V. control valves or four I.V. control valves.

After completion of the rolling test the installation of final keys and packers of the

H.P. and I.P. casing, the same can be cleared for welding of inlet and outlet

pipelines. The main steam inlet line from main steam strainer to the control

valves and then from control valves to the H.P. casing need much more care

during erection / welding of the pipelines. Similarly the Hot Reheat lines

between two Hot Reheat strainer to the control valves and from control valves to

the I.P. casing also need equal care during erection / welding of these pipelines.

These pipelines are directly affecting the performance of the turbine during

operation of the machine and a necessity is felt to fully involve the turbine

Erection Engineer in erection / welding of the pipelines at site along with the

Piping Engineers. The piping connection between I.P. casing to L.P. casing i.e.

cross around piping also need proper care but due to its construction with

Page No. 29 of 32

number of bellows in the system. Present method of erection / welding much of

the problems are not faced during operation of the machine. However if proper

care is not taken here then that may cause the unnecessary loading on the

various bellows of the piping and reduction in their life. In case, if proper care is

not taken during erection / welding of MS inlet, CRH & HRH connections with HP

& IP casing, a load will be transfer from the pipe line to the casing. Which may

cause vibration in the machine, obstruction in expansion of the machine,

obstruction of barring gaer operation in hot / cold machine, higher babbit metal

temperature and failure of brg. babbit etc. during operation of the machine.

Page No. 30 of 32

6. PROCEDURE

6.1. The following points are to be taken care while welding MS, CRH, HRH pipelines with HP & IP casing and control valves / strainers.

6.1.1. The HP & IP casings are to be cleared in all respects after fitting of final packers and axial / radial keys of the casing.

6.1.2. The ESV & IV valves are to be cleared after fitting of their servomotors and then levelling including the correct elevation etc.

6.1.3. The equivalent insulation weight is to be given on each control valve befor connection of any pipeline with the valve. The change in hanger value of the control valve is to be adjusted back by lifting the valve with the help of hangers. The control valve hanger reading should remain same as before and after installation of equivalent insulation weight on the valve. After this all the three hangers of each valve are to be locked to avoid any movement of the valve in upward direction, in case the equivalent insulation weight is removed or any of the servomotor is removed. Before starting of any welding with the control valve the valves are to be locked for their movement.

6.1.4. Erection and welding of MS line upto MS strainer and HRH strainer are to be completed first including either their insulation or equivalent weight is to be given for their insulation weight in the lines. These lines should be in perfect floating condition on their hangers before taking up the further work of MS & HRH lines upto the ESV & IV control valves.

6.1.5. Install MS & HRH lines between strainer and control valves and weld all the inbetween joins of the pipelines except the end joints with the valves and strainers. These lines are to be erected in such a way that both the end joints remain free and parallel with the strainer and control valve after taking their load on hangers. The freeness of joints are to be ensured after giving the equivalent insulation weight of the lines.

6.1.6. Weld MS & HRH lines with the strainers and again ensure the freeness / paralalllity of MS & HRH lines with the ESV and IV control valves. Any minor variation may be readjusted on hangers to obtain the freeness of the joints with the control valve.

6.1.7. Install the MS and HRH lines between control valves and HP /IP casing . Now all the in between joints may be keeping the end joints free with the valve and the casing. The erection of these lines are to be done in such a way that freeness and parallelity of end joints are achieved after fully floating the pipe lines on their hangers. The equivalent insulation weights are also to be added during erection of these pipe lines before welding the end joints.

Page No. 31 of 32

6.1.8. After ensuring the freeness and parallelity of the end joints between ESV control valve and HP casing , the same may be welded together. But the stress relieving of all the in -between joints of the lines are to be completed before taking up work of the above last two end joints . Similar proceedure may be followed for the lines between I V valves and IP casing also.

6.1.9. Weld left and right MS and HRH joints togethers with the HP and IP casing to avoid any left and right loading on the casing . during welding the left and right movements of casing may be monitored by installing the radial dial gauge on the casing.

6.1.10. The CRH lines are to be erected on their permanent hangers and the joint with the HP casing are to be made free /parallel after floating the pipe lines. The left and right side casing joints are to be welded together , similar to MS lines but before weling of these line the in- between joints are to be completed first . The equvalent insulation weight is also to be given on these line while checking the freeness of end joints with the HP casing.

6.1.11. The horn drop readings are to be recorded for both HP and IP casing after copletion of the job including insulation of pipe lines and control valve etc.

6.2. SPECIAL CARE

6.2.1. If possible keep the insulation weight and servomotors on ESV and I V control valves during erection /welding of these MS & HRH lines from strainers to the valve and casing . If the above condition are fulfilled then there no need of any locking of the valves during the welding of any pipe lines.

6.2.2. The control valves hanger readings are to be measured with the inside micrometer in various stages and changes are to be monitored properly . The readings are to be measured in the following stages :-

After complete leveling of ESV and IV control valves with their

servomotors

After putting the equivalent insulation weight on the control

valves.

After readjustements of control valve height equivalent to

insulation weight.

After connection of MS &HRH lines with the strainers .

Page No. 32 of 32

After connection of MS & HRH lines with the HP & IP casing .

After complete insulation of control valve and pipings.

6.2.3. Ensure proper clraning of MS and HRH lines between controls valve and casing as these lines are not covered in steam blowing operation . Proper care is to be taken during erection of these lines to avoid entry of foreign material.

6.2.4. The steam blowing of the MS and HRH pipe line are to be carried out after fully completing the erection /welding of lines from control valve to the HP and IP casing .

6.2.5. All the four corners of the casing may be locked with the casing clamp during welding of piping joints to avoid movement of casing radially.

6.2.6. The load of the upper half HRH pipe upto the flange supplied by turbine supplier is taken by the IP casing and by the piping hangers. This may be taken care while erecting the HRH lines.

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