30 September 2023

Steam Turbine Erection Sequence | Turbine erection procedure | Part#4

Rate this post

Steam Turbine Erection Sequence



(For 500 MW Fixed pedestal type Turbine with spring loaded foundation)

  1. Cleaning and checking of Turbine and Generator foundations as per the transverse and longitudinal axis including their elevation.
  2. Prepare and install LP base plates, HP front pedestal, HP rear pedestal, LP front pedestal, LP rear pedestal along with their anchor bolts and anchor plates.
  3. Provisionally align and level all the pedestal and LP base  plates as per the transverse and longitudinal axis  including their elevation.
  4. Matching of anchor plates of  pedestal and LP base plates to ensure their perfect seating.
  5. Finally align and level HP front, HP rear, LP front and LP rear pedestals along with LP base plates  as per the transverse and longitudinal axis  including their  elevation and catenary as per the design.
  6. Prepare and install steel bars for LP casing centralising  keys in foundation slab as per the required center  line .
  7. Weld locating ring of LP front pedestal and steel bars of LP front and LP rear centralising keys.
  8. Prepare shuttering and grouting of the pedestals and LP base plates including anchor plates of HP rear pedestal.
  9. Prepare, install, align/ level both the LP girder along with their carrier plates.
  10. Prepare , install and assemble LP front and rear end walls with the LP girders.
  11. Level / align LP outer casing  lower half as per the transverse and longitudinal axis of the machine.
  12. Install permanent packers of LP outer casing including their radial and axial keys.
  13. Prepare and install LP inner outer casing along with gusset plates in position
  14. Align LP inner outer casing lower half and level it. Install LP casing parting plane platform .
  15. Prepare and install LP front and LP rear lower half shaft seals housing and align it provisionally.
  16. Prepare and install LP rotor along with their bellows in position.
  17. Align LP rotor radially and axially in position and record free run out of rotor.
  18. Record/ Ensure radial and axial clearances of the LP casing including rotor float including fitting of final axial keys of the LP inner casing .
  19. Box up LP inner inner casing and heat tighten the parting plane bolts.
  20. Box up LP inner outer casing .
  21. Prepare and place HP module in position on temporary
  22. Transfer the load of HP rotor on bearings from the transport device and align it radially and axially.
  23. Check free run out of HP rotor on journal and coupling face including its float.
  24. Prepare and place IP module in position on temporary (In case IP module is sent to site in disassembled condition, refer Instruction T1-08-0606G.
  25. Loading of IP rear end of the shaft on bearing and removal of transport device.
  26. Provisionally align HP , IP and LP  rotor .
  27. Couple HP / IP rotor on temporary Bolts and align rotor / casing radially and axially.
  28. Record/ Ensure IP rotor float by shifting HP casing axially.
  29. Conduct Horn drop test of HP casing without any radial and axial keys and pipe lines.
  30. Conduct Horn drop test of IP casing without IP inlet upper half pipe lines.
  31. Assembly of breech nut of HP casing and Main Steam Stop & Control valve assembly.
  32. Erection of Reheat Stop & Control valve assembly.
  33. Weld IP inlet upper half pipe and record Horn drop values without radial-axial keys.
  34. Alignment of HP/IP/LP rotors and their coupling on temporary bolts including its couple runout.
  35. Swing check of HP rotor on its front end with temporary alternate bolt tightened on HP/IP coupling.
  36. MOP alignment and its doweling.
  37. Reaming/honing of HP/IP and LP/IP coupling including fitting of final coupling bolts.
  38. Fixing of axial position of shaft and assembly of thrust bearing including its colour matching.
  39. Roll check of HP/IP casing and fixing of  radial and axial keys of the casing (Casing final packers need not to be put at this stage).
  40. Assembly of bearings and checking of all clearances including fittings of side pads of bearing, yoke keys etc.
  41. Turbovisory works in all the pedestal i.e. assembly and calibration of thrust bearing axial shift, LP rotor expansions pick up, Hall generator and thermocouples of bearing .
  42. Preparations of the bearing for oil flushing.
  43. Oil flushing of the machine and normalizing the bearing after oil flushing.
  44. Preparation and floating of TG deck as per Instruction No. T1-08-0909G.
  45. Decoupling of HP / IP, LP/IP, LP/Gen., Gen./Exciter coupling and rechecking of alignment/catenary after floating of TG deck spring.
  46. Final tightening of HP/IP, IP/LP , LP/Generator and Generator / Exciter coupling after correcting the alignment including their couple run out and swing check of rotor on HP Front and exciter
  47. Checking /Correction of LP shaft seal clearance after floating of TG deck with CW pump in operation and water in the hot well of condenser upto operating level.
  48. Roll check of HP, IP casing in up and down direction only with TG deck in floating condition and CW pump in operation including water in hot well upto normal level.
  49. Assembly of final packers of the HP, IP casing after completing the roll check in up and down direction.
  50. Recording of final Horn drop of HP and IP casing after completing the welding of HP inlet, HP exhaust , IP inlet and Cross around piping.
  51. Preparation and boxing up of LP casing after competing the full Roll check of LP casing and fitting of final casing packers and radial keys.
  52. Barring gear.





1.1.       Customer to provide, center line and elevation point.

1.2.       Check  positioning of all the inserts and fixed points  with  respect to center line in transverse and  longitudinal direction as per BHEL Hardwar drawings.

1.3.       Check elevation of all points.

1.4.       Check verticality of all the pipe sleeves with the help of plumb.

1.5.       Ensure  proper  locking of all the insert and  fixed  points  before grouting.

1.6.       Ensure leveling on the fixed points of LP girder and LP rear pedestal.

1.7.       Preserve  machined surfaces of all the fixed points  against  any damages due to Improper handling.

1.8.       Ensure  proper flatness of the bottom seating plate of all  the inserts.

1.9.       Ensure  proper stiffeners in all the vertical and  horizontal embedment  provided  for various purposes like  hangers  and supports etc.

1.10.   Ensure proper cleaning of the area before casting.

1.11.   Remove all unwanted material.

NOTE: In case of spring loaded TG deck refer Installation Instruction   prior to positioning of inserts etc.


2.1.       Casting of foundation\TG  deck should be carried out  immediately  after inspection of the foundation\TG deck  i.e.  within  3-4 days  after  final  inspection to avoid any   disturbance  to  the  inserts and fixed point.

2.2.       Ensure  no disturbance to the insert etc. during pouring  of concrete while vibrators are used.

2.3.       About  15-20  mm  extra concrete may  be  left  on  top on all the pedestals and LP base plate area for  chipping/cleaning purpose at a later date.

2.4.       Close all the pipe sleeve from top to avoid entry of concrete inside. Alternately the pipe sleeve should be filled with sand.


3.1.       Clean complete foundation and remove all shuttering etc.

3.2.       Ensure there is no loose concrete layer in the region  where the pedestal and base plates are to be laid.  No repair should be  done  in this region without consulting the turbine erection engineer.

3.3.       Cover  all  the  opening  before  checking  any  dimensional  measurement to avoid any accident.

3.4.       Establish a suitable longitudinal axis considering the fixed point of the LP rear pedestal and various pipe sleeves / inserts.

3.5.       Establish  a transverse axis as 90 degree with the  help  of  the odolite.

3.6.       Measure  pitching/elevation  of all the  inserts  and  fixed  points.

3.7.       Measure elevation of all foundation on different pedestal and  LP base plate area.

3.8.       Check  level  of LP rear pedestal  fixed  points  and  if   required  correction  may  be carried out.


4.1.       Foundation  are  to be cleaned and loose concrete are  to  be chipped off.

4.2.       Maintain  elevation of foundation  to ensure correct thickness of non-shrink grout.

4.3.       A reference point for elevation in respect of machine center line (equivalent to LP rear pedestal) is to be maintained at  a proper place.  This point is  to   be preserved with proper protection.  For making  reference point  a one side ground plate of about 200 x300 x20 mm  may  be  used.  This may be welded on a I-beam  near  Generator.   The  ground position of the plate is to be kept on top  side and  all  elevation are to be transferred from  this  point    with  the  help  of water level jar.   A  correct  elevation  reading is to be punched on this plate. This reference point is to be used only during the turbine erection period.

4.4.       Clean  and deburr piping sleeves of the foundation on  ID/OD    of the pipe.

4.5.       Ensure all corners of the foundation remains perfect  during  chipping of extra concrete  of foundation.


5.1.       Open and clean the pedestal.

5.2.       Ensure there is no paint/oil on bottom face of the pedestal   sole plate.

5.3.       Ensure  there is no paint on inside surface or the  pedestal  and if required sand blasting may be carried out at site.

5.4.       Ensure correct fitting/clearance of locating rings of LP rear pedestal.

5.5.       The half bore  error of pedestals  is punched by manufacturing unit however in case it is not there, measure and punch half bore error of pedestal in  left/right    side of the pedestal.  If the error is nil then this may  be   punched as zero-zero.

5.6.       Ensure that the pedestal parting plane is feeler tight after tightening all the parting plane bolts.  If required, colour   matching  may be carried out but scraping/cutting is to  be  done on upper half cover only.

5.7.       Check  proper colour contact of spherical/cylindrical supports  of  the bearing  with  the pedestal.

5.8.       Check  contact  between  spherical Torus piece  of  bearing   and spherical/cylindrical  seat. In case of any  variation  in contact  no scraping/cutting to be carried out at site  and    this  may  be  referred to manufacturing unit. Also refer T1-08-0808G. Check centering of individual bearing w.r.t. pedestal  seal bores by fixing pianowire on individual pedestal.

5.9.       Ensure  cleanliness of all pedestal oil lines.  Close  opening of  oil  lines  of  pedestal to avoid any foreign material entering in these pipe lines during erection at site.

5.10.   Weld  MOP  suction  and  discharge pipe lines  in  HP  front pedestal as per the drawing before placement.

5.11.   Assemble  protection sheet in the foundation bolt  holes  of  pedestals.

5.12.   Assemble  anchor bolts along with anchor plate of the pedestals.   Ensure  that there is good contact available  to  the backing   plate   with  the  foundation.   If   required   colour matching/grinding may be carried out to achieve the contact.

5.13.   Assemble protection sheet in the anchor bolt hole from  bottom side of HP rear pedestal foundation to avoid entry of grout metal.

5.14.   Ensure level of both anchor plate of H.P. rear pedestal with  70-90 mm gap for  filling of grouting concrete.

5.15.   Adjust  height  of  the Anchor  Bolts  as  specified  in  the drawing.


6.1.       Clean all the four base plates.

6.2.       Mark/punch center line on the base plate as per drawing.

6.3.       Ensure proper cleaning of base plate on bottom side.

6.4.       Put identification marks on each base plate to avoid any mistake in positioning of the same.

6.5.       Do  colour matching of all the eight nos. carrier  plate  on both  the faces.

6.6.       Match LP base plate with the individual  carrier plate.

6.7.       Place  all the four base plates in position along with  their leveling screws and foundation bolts.

6.8.       Provisionally align and level all the four base plates.

6.9.       Assemble protection sheet in the foundation bolt holes.


7.1.       Provisionally align and level all the four pedestals including  LP  base plates with reference to  the  earlier  marked longitudinal and transverse axis.  The elevation reference is  to  be  taken  from the already positioned plate  for  this  purpose.

7.2.       Align and level LP rear pedestal and set  the elevation as per  machine center line.

7.3.       Use piano wire arrangement with micrometer for centering  of pedestal  bore  and  use  water level  jar  for  setting  of elevation.   Use measuring tape to maintain pitching of  the bearing  from one pedestal to another. Pedestals are to be set in level condition  on both longitudinal and transverse direction.  Align and level HP front, HP rear and LP front pedestals.  Elevation of  the pedestals  are to be set as per catenary of  the  machine considering the half bore error of the pedestal if any.

7.4.       Align and level, LP base plates. Elevation of LP  base plate is to be kept higher than the rear pair of LP base plate in line with catenary of  rotor.

7.5.       After alignment of LP rear  pedestal  weld the locating rings as mentioned in the drawing.

7.6.       During  welding  of locating ring, ensure that there  is  no movement  in  the pedestal in any of  the  direction.


8.1.       Fill  3  to  8 mm washed Pea-gravel in all  the  anchor  bolts sleeves.  These gravel are necessary to give damping  effect  to the anchor bolts during operation of the machine.

8.2.       Seal anchor bolts holes after filling of gravel to avoid any entry of grout metal.  Medical tape may be used for  sealing of these anchor bolt holes.

8.3.       Clean foundation with compressed air.

8.4.       Make shuttering of all the pedestal and LP base plates.  Use thick  polythene sheet inside the shuttering to give  better finish and avoid moisture absorption by shuttering.

8.5.       Shuttering  should  be made with maximum care to  avoid  any leakage  of grout concrete.  All sides of the shuttering  are to be sealed either with some sealing compound or with thick mixture of grout material to avoid leakage of grout material.

8.6.       Foundation  are  to  be kept wet for about  6  hrs.  before grouting.

8.7.       Non shrinkage cement duly approved by BHEL is to be used  for  grouting  of  the pedestals and  base plate.

8.8.       Use fresh stock of the grouting material only and check the strength of the material before use.

8.9.       During grouting, the mixture  has to be poured from one end only and it has to flow to opposite end to avoid any blockage of  air pocket.

8.10.   Water  curing is to be carried out for about 10  days  duration.

8.11.   All  anchor   bolts  are to be stretched minimum after  21  days  of grouting.

8.12.   HP,  IP & LP module placement work can be taken up after  24 hours of grouting of the pedestal and base plates.

8.13.   For individual pedestal and base plate, grout mixture should be poured in one lot only.


9.1.       Ensure matching of all the four palms of the module where it is resting on the pedestals.

9.2.       Ensure matching and parallelity of front and rear key  block of the HP casing.

9.3.       Assemble all four jacking screw of HPC and ensure their free movement.

9.4.       Clean  journals and coupling of the HP rotor.

9.5.       Record journal dia, coupling hole sizes and spigot dia of HP rotor.

9.6.       Lift module in level condition and place  it in position by keeping  it 3 to 5 mm  toward front pedestal side.

9.7.       During placement  of module use  temporary packers  similar to permanent and additionally support it  by four jacking screws.

9.8.       Ensure  load  on  all four packers with  the  help  of  some additional shims if required.

9.9.       Install  temporary  radial and axial keys  of  the  casing.

9.10.   Prepare HP rotor for alignment (Ref. section 20 before placing the IP module.


10.1.   Ensure matching of all the four palms of the module where it is resting on the pedestals.

10.2.   Ensure matching and parallelity of front and rear key  block of IP casing.

10.3.   Assemble  all  four jacking screws of IP casing  and  ensure their  free  movement.   If these jacking  screw  holes  are provided  with  the bolts from factory then same are  to  be removed before placement of module.

10.4.   Clean IP rotor on both sides including coupling and journal.

10.5.   Record spigot /recess, journal dia, and coupling hole sizes.

10.6.   Lift  the  module in level condition and place the module  in position by moving about 7 to 8 mm towards generator  end.   Use  temporary packers  for  placement  of module in position and additionally support the module  with jacking screws.

10.7.   Ensure  load  on  all four packers with  the  help  of  some additional shims if required.

10.8.   Provisionally  align the casing on front and  rear  pedestal bore.  Install temporary radial and axial keys of the casing with some shims.

10.9.   Prepare IP rotor for alignment (Ref. section 20).

NOTE: In case IP module is sent to site in disassembled condition, refer  Instruction T1-08-0606G.


This assembly can be divided in following sub assemblies:

11.1.   Assembly of girder and end walls.

11.2.   Assembly of LP inner  inner and LP inner outer casing  lower half.

11.3.   Assembly / welding of LP outer casing.

Before  starting  assembly of LP casing  in  position,  following works are also to be completed :

– Positioning and welding of LP casing centering pin of  front and rear side.

– Positioning of key block of LP casing axial keys.

– Positioning of all internal of condenser.


Two  nos. centering pins are to be located below LP front and  LP rear  pedestal.  Necessary pipe along with two sq. end plates  are already provided in the foundation to take the radial load of the LP casing:

12.1.   Plumb  the  center line from LP front and LP  rear  pedestal bore on both side over the square plate of the foundation.

12.2.   Establish accurate position of the pin and put a punch  mark at  a  required height and mark a circle and  a  controlling circle over all the four sq. Plates.

12.3.   Dia  of  the circle must be equal to pin  dia.   A  template equivalent  to pin dia has to be made for this purpose  with about  20 mm thick plate and a welded pipe for using as  an handle.  The template dia must be very accurate and same may be made on machine.

12.4.   Make  precise  hole  with  gas  cutting/grinding  to   match template  on  all  four embedded  plate.   Ensure  that  the template  is fitted with minimum clearance and  hole  center are perfect as per marking.

12.5.   Drill  hole of about 10 mm dia on one of square plate of  LP front  and on one plate of LP rear for air venting to  avoid cracks during welding.

12.6.   Insert  both the pins and carry out the welding as per  laid down  procedure.  Before welding set correct axial  position of the pins.

12.7.   Insert  key  block on both the pins and weld  their  locking ring also.  Ensure proper clearances in key block before welding of its locking ring.

12.8.   Preheating  of  200 degree Celsius or more to  be  achieved before  any  welding.  Dye penetrate test on  root  run  and after final welding is to be carried out.


13.1.   Colour  match  side  matching flange  of  girder   with  the surface plate.

13.2.   Colour  match seating flange of girder where it  rests  over the LP base plate.

13.3.   Match and ensure parallality of axial key ways of girder.

13.4.   Colour match side flanges of end wall.

13.5.   Match and ensure parallality of key block of end wall.

13.6.   Place  left and right girder with carrier plate, spacer  and lubrite packer on LP base plate.

13.7.   Provisionally  align and level the girders.  Set  height  of the  girder  equivalent to machine center  line  maintaining catenary of the machine with the help of water level jar arrangement.

13.8.   Assemble  locking  plate of the front and rear end  wall  to facilitate its assembly with the girders.

13.9.   Assemble front and rear end wall with the girders and ensure perfect parting plane level during tightening.

13.10.Align,  level LP outer casing and ensure contact of  packers by colour matching/machining of spacer height.

13.11.Install LP casing radial and axial keys.

13.12.Assemble  inner  outer casing axial key blocks on  left  and right side of girder and dowel them.

13.13.Lock with tack welding all the vertical joint bolts.

13.14.Put  a seal weld run between girder and end wall  joint  all around except on top face.

13.15.Weld  girder  and end wall parting plane  joint  with  argon welding.  Before welding make a V groove with the help of  a chisel and allow the projection of material on surface.   Do not make the groove by grinding.

13.16.Do  colour matching with a surface plate on all four  corner where argon welding have been carried out.


The  LP  inner inner casing lower half is received from  factory  in assembled condition with LP inner outer casing lower half.

14.1.   Clean the casing and check all the threaded holes.

14.2.   Do  colour matching on all four corners of the casing  where it rest over the girder.

14.3.   Colour match all eight carrier plates of inner casing on both side.

14.4.   Assemble  all  carrier  plates on girder and  do  the  colour matching with individual carrier plate.

14.5.   Prepare Gusset plate of front and rear side with  temporary  radial keys   for fitting in LP inner casing.

14.6.   Level  and lift LP inner outer casing and  assemble/weld both  the  gusset plates with the help  of  some  temporary support.

14.7.   Lower the casing in position over the carrier plates  fitted with spacer and lubrite packer.

14.8.   Provisionally align the casing radially and axially.

14.9.   Support the gusset plate with the help of screw jack (about 10-15  tons) on front and rear side by taking support  from condenser stiffeners. Screw jack is to be unscrewed after box-up.

14.10.Adjust the height of the LP inner outer casing as per center line of the machine and then level it with the help of water level jar arrangement.

14.11.Ensure  that  all the eight packers have  good  contact.  Loading of each packer is to be ensured.

14.12.Lower the casing by about 2 mm on all the eight packers with the  help  of shims for placement of LP rotor to  avoid  any fauling during placement of rotor.

14.13.Fit  and weld all gusset plate stiffener pipes  except  pipe between  LP inner outer casing and condenser.  Do  not  make any  weld  connection  between condenser and  any  of  these stiffeners till neck welding of the condenser is over.


15.1.   Measure journal dia, spigot dia and coupling hole sizes.

15.2.   Ensure  centering  of temporary bearing support  in  the  LP front pedestal for placement of LP rotor.

15.3.   Place LP rear bearing in position.

15.4.   Prepare shaft seal compensator along with gaskets (Gasket  to be installed in fully ring shape only ) and position them on LP rotor with the help of supplied supports of compensator.

15.5.   Lift  LP rotor with the supplied lifting beam  in  perfectly level  condition and place it in position.  During  lowering of  rotor  ensure  radial clearance with the  help  of  long feeler gauges in the LP casing.


The  welding  of  LP  outer cover is to  be  carried  out  before  placement of LP Rotor in position to avoid damage to the rotor.

16.1.   Colour  match  and  remove all high spots  of  the  matching flange of the LP outer casing.

16.2.   Ensure good contact between parted diffuser of LP front  and LP rear cover.

16.3.   Colour  match  and remove all the high spots of  the  parted diffuser/vertical  face  to  ensure good  contact  with  the compensator at a later stage.

16.4.   Colour match and remove all burrs  and high spots from parting plane of LP outer casing.

16.5.   Side flange of LP front and rear cover are to be ensured  in right  angle  to achieve good contact  with  their  matching flanges.

16.6.   Place LP front LP rear cover along with parted diffuser and ensure  feeler  tight joint after  tightening  the  parting plane  bolts.   The joint must be feeler  tight  just  after normal  tightening  of bolts.  Do not over  tighten  parting plane  bolts.

16.7.   Ensure matching of parted diffuser  face  on both side of LP casing.  If necessary colour matching may be carried out to achieve a feeler tight joint.

16.8.   Drill/ream  all the parting plane holes as per drawings  and install all dowel pins.

16.9.   After  fixing  of  LP  front  and  rear  cover  measure  the dimension  for positioning of both the center flanges.   The dimension are to be recorded in such a way that there is  no clearance  after  fitting of center flanges in  position  on both  side  with the LP front and rear  cover.   The  center flanges are supplied in extra length on both sides from  the factory and final length are to be maintained at site only.

16.10.Drill/ream dowel pin holes in center flanges and install all dowel pins in position.  Ensure drilling and reaming of  all dowel pin holes to equal depth.

16.11.Fit both the center pieces of the cover in position.

16.12.Achieve the fitting clearances for welding as per laid  down procedure.

16.13.Weld/lock  LP upper half flange with respect to  lower  half   casing  with  the  help  of  metal  cleats  to  minimise  the   distortion  during  welding of LP cover.  The cleats  may  be welded at an interval of about one meter distance.

16.14.Carry out the welding as per the following welding procedure.

17. Welding procedure

17.1.   Tack weld the crowned seam joint. permanently welding approx. 100 mm at the generator end of the joint.

17.2.   Opposite tack welded radial joint 2, permanently  weld approx. 100 mm of the crowned seam joint, pos. 1, staggering the two weld ends to ensure a perfect transition when the crowned seam joint is finish welded.

17.3.   Tack weld the crowned seam joint at regular intervals with a tack  of 5T and pitch of 25T.

17.4.    When welding radial  joint 2, shell plates 1 & 2, tacked together, rest on but are not tacked to the retaining strip in the region of joint  1, so that any shrinkage occurring during welding of seam 2 is not obstructed.

17.5.   The tacking & welding  sequence applies for all shells courses.

17.6.   Weld radial seam at TE according to welding sequence plan.

17.7.   Align, adjust and tack weld radial seam at GE.

17.8.   Weld radial seam at GE according to welding sequence plan.

17.9.   Weld crowned seam joint.

17.10.Align shell courses on joint strips and tack weld,

17.11.Weld on joint strips from center & ends of shell plate.

17.12.Insert pins in top half casing, release top half casing and lift to insert and tack filler piece between joint strips.

17.13.Unbolt top half casing and lift in order to weld and finish – machine filler pieces in the region of the joint surface.

17.14.Check welds according to specifications.


LP rotor is to be aligned on  pedestal  seal bore and LP inner outer casing is to be centralised in such a way that  enough  clearances  are  available  to  LP  rotor,   during alignment.   Now this alignment activity of all the  three  rotor can be divided as below :

18.1.   Preparation of HP rotor for alignment.

18.2.   Preparation of IP rotor for alignment.

18.3.   Preparation of LP rotor for alignment.

18.4.   Alignment of LP-IP & HP rotors.

18.5.   Reaming, honing of the coupling holes.

18.6.   Balancing of coupling bolts weight.


19.1.   Align  HP  rotor with reference to front and  rear  pedestal seal  bore  reading.  If required move  complete  HP  module along with the rotor.

19.2.   Fix  temporary  radial and axial key of the casing  on  both front  and  rear side of the casing. Remove  HP  front upper half transportation  device.

19.3.   Lift  module by 0.20 mm on front side by putting  additional shims in front packers.

19.4.   Insert HP front bearing in position.

19.5.   Reduce 0.20 mm shims gradually and ensure about 0.10 mm load  on the rotor.  If required further lower the front side of the  module to achieve the loading on bearing by about  0.10 mm.

19.6.   Remove  HP front lower half transport device  gradually  and ensure  no  movement  between  HP  casing  and  rotor.    If necessary adjust shims of HP casing front packers.

19.7.   During  loading of bearing always ensure that the  rotor  is not  fouling  inside the casing with the shaft  seals. This may be ensured by checking with feeler  gauge also.

19.8.   Check  axial  position of HP rotor in front  side  on  left; right and top position from the rotor reference point to the HPC as given in the shop protocol.

19.9.   Insert  and  load the bearing in HP rear  end  in  similar way  as  carried out in case of HP front end  and  record axial position of rotor as per shop protocol.

19.10.Lock  axially  HP  rotor with  some  fixture  along with  the arrangement  of jacking screw for movement of  rotor.   This fixture may be mounted on rear  pedestal.  Before locking of rotor  ensure axial position of the shaft.

19.11.Center HP shaft with reference to HP casing front and rear spigot.  If necessary,  move  the  casing readily  to  achieve  the  centering.   A  fixture  can   be fabricated  at site for mounting the dial gauge on both  the end of the rotor to check the centering of the shaft.

19.12.Use  thick  oil during rotation of  shaft  on  the bearing.

19.13.Protect  bearing  from  any of the dust  particles.   It  is recommended  to place upper half of bearing in  position  to avoid dust and any other damage to the shaft journal.

19.14.Realign  the rotor shaft with respect to pedestal seal  bore and  if necessary adjust the shims below  spherical support  of the bearing.

19.15.Care should be taken  during  alignment that  radial  and  axial clearances between rotor and casings does not get bridged.

19.16.Check HP rotor radial run out on journal and coupling.

19.17.Check  axial run out on thrust collar and both the coupling  faces of HP rotor.

19.18.Check axial float of the rotor. Compare values with shop protocol values. (Ref. T1-08-0802G). Deviations to be reported to Manufacturing Unit.


The  IP  module  is also to be prepared in line with  the  HP module.  However   as IP rotor  is provided  with  one  side bearing  and  opposite  side is coupled with  the  HP  rotor without  a  bearing,  extra care is  necessary  during alignment of rotor in IP casing.  The additional point which are  to  be taken care are explained below :

20.1.   Place  IP rotor rear end on bearing similar to the HP  rotor and remove transportation  device.

20.2.   Provisionally align HP/IP rotors and couple on temporary bolts by moving both the modules.  During coupling of the rotors, the transportation device of IP front end is also to be taken out.

20.3.   Check  axial position of rotor w.r.t. IP casing and adjust  as per shop protocol.

20.4.   Check  centering of IP rotor front and rear end w.r.t. IP casing (similar  to the  HP rotor centering check).

20.5.   Check  float of the IP rotor.  Compare values with the shop protocol values. (Ref. T1-08-0802G).  During checking of float ensure HP casing  is not fouling with HP rotor.  If required HP casing may be moved axially for this purpose.

20.6.   Check facial runout on IP rear coupling face and radial runout on journals and couplings.


21.1.   Provisionally  align  LP rotor in pedestal  seal  bore placing the front end of shaft on auxiliary  bearing and rear end on bearing.

21.2.   Align  LP inner outer casing radially with the help of  long feeler  gauges  and  install temporary radial  keys  in  the gusset plate.

21.3.   Record  all  the radial and axial clearances of  the  LP casing without coupling  the LP-IP rotor.  Variation if any  in radial or  axial  clearances are to be corrected/approved  at  this stage.

21.4.   Remove  shims  from the front end of auxiliary bearing  and keep rotor on lifting tackle.

21.5.   Record  radial run out of LP rotor coupling and journal and axial run out of the coupling faces of the both end.

21.6.   Record  float of the LP rotor by moving the LP  inner  outer casing lower half.

21.7.   After ensuring the radial and axial run out of the LP  rotor the LP inner outer casing can be boxed up.  Parting plane bolts of LP inner-inner casing are to be heat tightened.


22.1.   Ensure  radial and axial runout of all the three rotors  are individually in order.  If necessary individual rotor module can be taken out for correction of coupling face runout. Any variation on radial runout of rotor is to be referred to the factory.

22.2.   Match  coupling  faces of two rotor as per  the  axial  face reading  of the rotor.  Ensure that the higher point of  the rotor  coupling face and lower point of another  rotor  coupling face are matched together. This is to be compared with shop protocol also.

22.3.   Preliminary align radially and axially all the three rotors and  shift them in spigot along with the casing to avoid fouling of rotor inside the casing.

22.4.   During  alignment  achieve left and right  movement  of  the rotor with the help of shims in spherical / torus piece of the bearing.  The  up and  down movement of the rotor is to be achieved  with  the   help  of  shims  in the cylindrical/spherical support  of  the bearing .  The adjustment  of shims in the bearing should  be within the permissible limits only.

22.5.   Ensure  during alignment that the catenary  of the  shaft  is maintained.

22.6.   Check/record spigot clearance of HP-IP and LP-IP rotors by actually moving them in spigot.

22.7.   Install four nos.  supplied bolts along with one/two pins  in HP-IP  and LP-IP coupling.  Hand tighten the coupling  bolts by keeping a gap of  > 1.00 mm in coupling faces for alignment.

22.8.   Rotate  the  rotor system and record the coupling gap  at  90  Deg. interval  on left, right and top position.  Ensure that  the coupling, bolts and  pins remain free while recording the gap of  the coupling for the alignment purposes.

22.9.   Check swing check value of the HP rotor with alternate bolts in position.  The above value must be within the  prescribed limit  only  otherwise a correction must be carried  out  at site in consultation with designer.

22.10.Ensure  free  movement of rotor on their  bearing.   Do  not rotate the    rotor if it is tight during its rotation.

22.11.Ensue that the coupling holes are  properly aligned to avoid unnecessary enlargement of holes.

22.12.Ensure  HP-IP-LP rotor radial run out after tightening with alternate clearance bolts. Release the couplings for reaming / honing of couplings.

22.13.    In  case  of  spring  loaded  TG decks,  refer  alignment  procedure    T1-08-0909G


23.1.   Ensure  that  there  is no disturbance  on  coupling  during reaming/honing operation.

23.2.   First  ream/hone  two  opposite holes of  the  coupling  and install two pins/bolts  with sliding fit and then take up all other holes.

23.3.   Enlarge coupling holes to the minimum possible diameter  and try to make all the holes to same dia.

23.4.   Ensure that the finished holes are straight and there is  no banana  shape.  This can be ensured by checking hole with  a straight  ground finish pin having 0.02/0.03  mm  clearance.

23.5.   The length of the pin should be equal to the bolt length. In case,  few holes have gone considerably over size  during reaming/honing at site/works, do not enlarge all the  holes.  As a special case in such  cases these few holes may be left as  oversize.

23.6.   Ensure  that the holes during reaming/honing  are  perfectly finished  as ground bore and size obtained should be  within 0.005 mm. Ensure all the coupling bolts are fitted within 0.02/0.03 mm clearance with sliding fit and bolts are to be ground within  an accuracy of 0.005 mm.

23.7.   Coupling bolts are not to be hammered in the holes and these are to be fitted with thumb pressure only.

23.8.   Do  not decouple the coupling in any case  without  ensuring the fitting of all the coupling bolts.


After fitting the coupling bolts in all the holes these  are to be balanced within 5 gms accuracy and an accurate balance which can take a load of about 20 kg.  may be used.   During balancing of coupling bolts following points are to be taken care.

24.1.   Final  balancing  of  the  coupling bolts  are  to  be  done  along with the coupling nut of individual bolt.

24.2.   If  all the coupling bolt hole sizes are  same  before/after reaming  and honing then all the bolts can be kept of  equal weight.

24.3.   If necessary adjust the weight of the bolts by machining the metal from the bolt head.

24.4.   When  the holes of the coupling are of different sizes  then it  must be seen that whether excess enlargement  have  been done at site or works.  In such cases if excess cutting have been  done at site in a particular hole then  coupling  bolt with  excess  weight are to be used.  The amount  of  excess weight must be equivalent to the excess enlargement of  hole at  site.   If a particular hole of excess dia.  is  noticed from factory then it is assured that the particular rotor is balanced  with  excess  dia hole and  there is  no  need  of providing excess weight bolt at site.


After completion of reaming/honing and preliminary tightening of  the coupling bolts, the colour matching of the thrust  bearing pad have to be carried out with respect to the thrust collar of  the HP Rotor.  During colour matching a good contact  on all  the pads of front and rear side are to be ensured  with respect to rotor collar by moving the rotor in +/- direction during its hand rotation.  Following points are to be  taken care during colour matching.

25.1.   Thrust bearing must be axially locked with the help of axial keys  during the colour matching of the pads. Axial keys to be fitted while finalizing the alignment of thrust bearing with rotor collar without pads.

25.2.   Few  drops  of oil is to be put on journal  portion  of  the thrust  bearing during rotation of rotor to ensure that  the oil is not entering in pad portion of the bearing.

25.3.   Colour is to be applied on the thrust collar of the rotor.

25.4.   If necessary move the spherical support  of the bearing pedestal to ensure the equal thickness of the pads before fittment of axial keys of the bearing.

25.5.   During  moving  of  the  spherical support  in  front  or  rear direction ensure that there is no left – right  movement  to the support  otherwise  that may  cause  misalignment  of  the bearing.

25.6.   After  colour  matching  of the thrust pad  the  axial  zero position of the rotor is achieved and this can be taken  for all other future reference for setting of axial position  of HP,  IP  & LP casing.

25.7.   HP,  IP  and  LP lower casing are to be  set  axially  after fixing the axial position of the rotor and their final axial keys can be installed at this stage.


After  completion of colour matching of the  thrust  bearing pads the  casing alignment work can be taken up.   The  following points  are  to be taken care while aligning HP, IP  and  LP casing.

26.1.   The  roll  check have to be carried out in HP, IP  and  LP casing  to ensure the correct radial clearances of the  casing.

26.2.    TG deck springs are to be kept in floating condition while recording the roll check of LP casing. However  the roll check of HP/IP casing may be carried out before floating of TG deck for fitting of their radial keys  but up and   down roll check  of HP/IP casings are to be done with TG deck in floating condition  as per the procedure TS/ST/ 01/0008/00/96.

26.3.   Ensure  that there is no obstruction in the movement  of  LP inner  casing  due to welding of any of  extraction  piping. The  one of the joint of extraction piping may be left  free till completion of roll check  of the casing.

26.4.   The welding of steam inlet pipes between LP inner casing and LP  girders are to be taken up after completion  of  roll check of the casing.

26.5.   HP, IP and LP casing are to be fitted with final packers and axial key immediately after the roll check. During fitting of casing axial keys and palm packers  ensure proper contact on lubrite coating  of the keys/packers  to avoid any damage  of these coating during operation of the machine,

26.6.   After  completion of fitting of final keys and packers  only the casing are to be cleared for further works of welding of various pipe lines.

26.7.   The  gland steam, balancing leak of lines, steam  inlet  and exhaust pipes are to be welded with HP casing after  fitting of final axial keys and packers of the casing.

26.8.   Center HP rotor w.r.t. casing front and rear spigots.  Compare the readings with shop protocol and record the readings.

26.9.   Offset center line of the HP, IP & LP casing w.r.t. respective rotor center line as per recommended logsheet.

26.10.Check/record  LP diffusers centering readings after roll check of the casing.

26.11.Before roll check of LP casing all  the  stiffener  pipe welding work must be completed. Refer T1-08-0909G.


27. FINAL Tightening  of COUPLINGS

In case of spring loaded foundation after completing all other  works  the HP / IP , IP/LP , LP/GEN , GEN/EXCITER   couplings are to be reopened  and realigned  after completing the reaming /honing .  The rotors  alignment  are to be checked with TG deck  in floating condition   as per the laid down procedure. After checking of alignment /catenary  the final couplings  are to be tightened including their coupled run out  and swing check of rotors on HP front and Exciter end of the shaft.


The  boxing up of LP inner inner and LP inner  outer  casing can be taken up before starting the alignment of HP-IP &  LP rotor  for  coupling work.  The following points are  to  be taken care before/during boxing up of these two casings.

28.1.   Ensure matching of all the parting plane holes, fitting of  cap nuts and accessibility of spanner .

28.2.   Ensure  feeler tightness of the parting plane joint of  both the casing.

28.3.   Check/record  all  the radial and axial  clearances  of  the casing.

28.4.   Ensure proper cleanliness of the LP inner inner and LP inner outer casing.

28.5.   Ensure adequate clearance between LP inner inner casing  and LP  inner  outer  casing to  avoid  any  obstruction  during expansion  of the LP inner casing inside the LP inner  outer casing during operation of machines.


During the boxing up of the LP outer casing following points are to be taken care.

29.1.   Roll check  of LP inner casing including the  fitting  of key, packers etc. must be finished.

29.2.   All  the works must be finished inside the LP casing  before boxing  up  of LP casing including LP extraction  pipe  line works.

29.3.   Ensure  matching  of  all parting  plane  holes  and  feeler tightness of the joint before boxing up of the casing.

29.4.   Ensure  feeler tightness of bursting diaphragm flange  joint before boxing up of the casing.

29.5.   Ensure proper assembly of parting plane rubber cord.


After completing the welding of HP inlet, HP exhaust, IP inlet, IP exhaust  and other piping of HP/IP casing the final horn drop readings are recorded as per the laid down procedure mentioned in the manual for horn drop check.  However  the IP casing horn drop is also to be recorded with IP inlet upper half pipe  welded with casing alone.

Leave a Reply

Your email address will not be published. Required fields are marked *