TURBINE GENERATOR PKG ERECTION PART-XII, SPRING ERECTION AND RELEASE - ABC OF THERMAL POWER PLANT.

Earlier days up to 250 MW most of the foundation was rigid and casted along with the main column foundation. But now a days all the TG deck foundation are casted having Spring /viscous dampers in between. This type of foundation has some added advantage on turbine erection and size of turbine column. All the foundation above 500MW and above is having such type of foundation. In BHEL we use GERB spring as our standard spring supplier wherever I worked.

 The spring element in 500MW machines and further higher rating machines are used with visco dampers. The springs units are not supplied to site with required pre-tension values through these are supplied with some amount of pre-tension. The required pre-tension of the spring units are done at site before its installation in position. A special device for pre-compression of these springs units is also supplied by spring supplier.

The shuttering of RCC slab of TG deck is furnished before installation of these spring units. The top surface of individual column where these spring units are mounted should be within accuracy of +00 mm to -3.00 mm. If necessary these may be corrected by chipping before installations of the spring units. The level deviation among various columns is permitted +00 mm to -5.00 mm in total including individual column variation of +00 mm to -3.00 mm.

The bottom shuttering of pedestal must be cut over the column head for lowering the spring units.

After lowering the spring unit the cover steel plates are placed in position with shuttering supports.

An air gap of about 5.00 mm to 10.00 mm is left between cover plate and spring units for

settlement of deck during casting. The visco dampers are also filled up at site only with visco liquids

supplied by spring supplier. Each spring units are placed over the resistance pad to avoid movement

of the spring units during operation of the machine. Similarly the resistance pad is given on top of the steel shim to avoid the shifting of the shim during operation of the machine. Each spring unit is provided with 10.00 mm of steel shim for future adjustment.

The TG deck springs are released after installation of all Turbine Generator components including piping and the condenser has to be filled up to operating level including CW pump in operation for full load condition. The shims provided for additional compression of the spring units are also adjusted during this stage, the final alignment of various rotors and turbine casing are done after release of the spring unit. The Generator hydrogen cooler & LP heater if any inside the condenser are to be filled up in cooling water space for their operating condition before release of TG desk spring. The insulation of various casing / pipe lines including cladding if any are also to be installed otherwise the equivalent weight is to be incorporated before release of desk spring. All the pipe lines connected with the Turbine and Generator should be made available on permanent hangers and supports to avoid any additional load on the TG deck afterwards. The TG deck should also be made free all- around to avoid any obstruction in its movement.

During release of TG deck springs and final alignment of rotors the condenser spring is also to be kept in floating condition considering that condenser neck welding is already done. Similarly the condenser spring measurement should be with in + 1.00 mm otherwise the shims may be adjusted in condenser springs. No adjustment of TG deck springs or condenser springs are permitted after final alignment of the rotors. During any subsequent adjustment of TG deck spring the final alignment of all rotors are to be checked.

There are finer points of spring installation and releasing but we need not to discuss now. Basics of installation and releasing are given above. There are few important activity  needs to be performed which will be indicated very briefly.

- Condenser neck welding having spring loaded foundation.

- Assembly of breach nut.

-Turbine Insulation

- Turbine Integral piping and other piping. It is better to identify the scope of piping between IBR/Non IBR. This demarcation should be available with construction man. Any deviation from IBR norms will attract problems from statutory authority. Therefore system wise identification is needed. In general oil lines ,water lines ,air lines and Gas lines are not under IBR but some of the steam lines are under the scope of IBR. Interpretation of IBR authority varies from state to state therefore one should take state IBR authority in confidence.

For above works it is advised to follow the OEM’s practice in vogue. All the OEM ( original Equipment Manufacturer)  detailed it in there erection manual.

One should follow the approved FQP ( field Quality Plan)  for measurement and records of various reading in the log sheets of FQP . This will help in analysing any future problem.

PS:- I have a eight page technical document given by M/s GERB with supplied spring. Interested person to receive the document as reference may send request to my mail

dguha1952@gmail.com

Civil protocol for placement of VIS. Please note the number of reading.

 

TURBINE GENERATOR PKG ERECTION PART-XI, ERECTION SEQUENCE ,TIPS ETC.- ABC OF THERMAL POWER PLANT.

Part –XI

Sealing and anti seizing compound used in turbine as per BHEL ‘ s Turbine manual.

========================================================================
Joint plane of hpt ipt & valve casings, gland boxes & strainer housings, breech nut mating face.

- Metal to metal joint in high temperature zone

- Use − Birkosit ,− Stag B ,− Magnesite compound of bhel standard.

================================================================

Joint plane of LP outer casing (without rubber sealing chord).

-Metal to metal joint in low temperature zone

-Use  Holdite  and  Loctite 574

================================================================
Joint plane of bearing pedestals, mop casing, valve servomotor

Metal to metal joint in oil environment

- Hylomer ,  Golden Hermetite  and  Victor Shellac .

=================================================================

Threaded fastners including, breech nut threads, keys, packers,

Dowel pins u & i - seal rings in high temperature zone.

high temperature ( < 350°c) antisiezing . Use  molykote p37 and  oks 255  

================================================================= 

Threaded fastners, keys, packers, dowel pins in low temp. zone, coupling bolts seal  

segments, hp/ip casing palm packers, hp front & rear bearing pedestal packers (other  

than self lubricated lubrite packers . i.e  low temperature ( < 350°c) antisiezing  

use  Molykote d 21, Oks 511, Mgs 400

================================================================= 

Tips on different aspect of Main Turbine Erection. 

-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. 

The bearing parting plane bolts are to be tightened to required torque only no other  

method of tightening of these bolts may be used. 

-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.

-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. 

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. 

- Projections of these axes in the corresponding drgs. shall be as under :

X axis = view toward generator

Y axis = view upward generator

Z axis = view to the right

-The breech nut assembly used in between connection of main steam inlet line and HP

module. A special care is must while making the breech nut assembly first time at site

during erection stage. Follow the OEM instruction carefully.

ERECTION SEQUENCE (For 500 MW Fixed pedestal type Turbine with spring loaded

foundation) – BHEL MAKE TURBINE 

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 centre 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 ax14. Align LP inner outer

casing lower half and level it. Install LP casing parting plane platform .

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 packers.

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 packers. (In case IP module is sent

to site in disassembled condition.)

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

run out.

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. Turbine Supervisory Instrument 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 OEM instruction.

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 rotor.

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 up to 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 up to 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.

Continued to Part -XII

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TURBINE GENERATOR PKG ERECTION PART-X, DIFF.CHECKS BUMP ,SWING ,HORN DROP ,CATENARIES ETC.- ABC OF THERMAL POWER PLANT.

Part – X

After colour matching axial zero position is achieved and this will be reference point of

future axial measurement of HP,IP and LP casing. During Turbine supervisory  instrument calibration

rotor is given to instrument group at axial zero position .

 After completion of colour matching of the thrust bearing pads the casing alignment work

can be taken up. 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.

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.

ASSEMBLY OF BEARING AT SITE

The KWU/BHEL 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 b

earing 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.

Assembly Procedure is available in the erection manual of 500MW turbine.

CRITICAL CHECKS OF TURBINE ERECTION.

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.

ROLL CHECK

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

actual by moving the casing radial direction 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 roll

 

CATENARY AND ALIGNMENTS

The catenaries of the machine are 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 problems 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 catenaries 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 catenaries 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 along with proper catenaries of the machine.

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

catenaries are much more due to settlement of the foundation frame.

In each overhaul of the unit the catenaries 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

catenaries may be achieved. In extreme cases these pedestals may be even re grouted

during major overhauls of the unit to correct the catenaries of the machine.

HORN DROP TEST

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.

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.

SWING CHECK

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

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

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

 CONTINUED TO PART -XI

PS; I HAVE ASSEMBLY REPORT (PICTORIAL) PREPARED BY BHEL ENGINEER FOR FIRST
660 MW LP TURBINE IN PDF FORMAT. THOSE WHO WISH TO SEE MAY SEND REQUEST
ON MY EMAIL . THE SAME WILL BE SENT TO THEM FOR KNOWLEDGE PURPOSE.

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