GENERATOR PKG ERECTION PART-II, LIFTING ARRANGEMENTS OF GENERATOR - ABC OF THERMAL POWER PLANT.

PART- II

Stator lifting by EOT Cranes:-

In earlier days up to 210 /250 MW class the stator is being lifted by two EOT cranes of similar capacity  with lifting beam. EOT cranes main hooks are fitted with the lifting beam and lifting beam main hook is being utilised for lifting stator by using special sling designed for the above purpose. Stator  is placed in the service bay within the approach of EOT crane and unloaded from Trailer / wagon as the transportation method available in the power house. Earlier days a railway line runs  across the service bay. Now a day’s all the stator is coming by high capacity hydraulic Trailer.  Stator is unloaded by hydraulic jacks on temporary supports in the service bay. Fix the trunion plates (04 nos) with the body of the stator after necessary cleaning and blue matching with stator body. This has to be fixed as per the norms because sling will be placed on it. Clean the terminal box and do the blue matching with surface plate. This are the preparatory work for stator lifting. Terminal Box can be placed before stator if there is no other possibilities push it from bottom. Stator is lifted by tandem operation with lifting beam from any of one the crane. This arrangements to be tested before put in actual use. Necessary adjustment to be carried at that time, to avoid any jerk during the operation.

Stator lifting by Portal crane or by strand jack method.:-

Once we are start erecting 500 MW /600 MW /660 MW /800 MW generators the weight of the stator

increases considerable therefore alternative lifting arrangements are thought of . Some of the

utilities  think about the lifting irrespective of loading TG  bay . Otherwise total TG bay need to designed taking stator weight as one of the factor.  Portal crane and strand jack method came as solution. It has been seen availability of Portal is a problem. In my service life we have noticed  that once we need to erect 09 numbers of stator in a year and we have only two portal cranes. Portal dismantling , transportation and re –erecting is 03 to 04 months cycle depends on location of both the sites . We cannot erect all the Generators required by management and to solve this problem stand jack method of stator lifting was adopted. This type of lifting was already popular for boiler drum lifting.

Placement of stator for this type of lifting is very important. The stator need to be placed outside A row column and between transformer bay and A row column. Centre line  of  Generator from TG to be brought and marked for stator placement . No axial movement is possible when stator is placed on foundation. Foundation for jack pads and lifting structures are needed for unloading  the generator  and placed on temporary supports. All other works to be done on generator is same. Stand jack system to be erected by EOT crane and Heavy lift Crawler crane from AB bay and Outside A row. Close co –ordination is required from all quarters as that area includes the area of CW pipelines  for Condenser. Clear approaches is required for heavy duty crane and Hydra cranes.

As the main column pitch distance is less than the stator length swivel arrangement is required in strand jack system. Strand jack system is totally hydraulic and operates slowly it may take  06 to 08 hrs from start to complete the lifting and placement  operation.

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GENERATOR PKG ERECTION PART-I, GENERAL FEATURES OF GENERATOR WITH PHOTOES - ABC OF THERMAL POWER PLANT.

PART -I

Generator with exciter is the ultimate  output of all the system put together. This is very important item to be installed with turbine system. Generator is the heaviest item to be installed in the power house in single lift. In earlier days generators ( up to 300 MW) class were installed by two EOT crane by using common hook  and tandem operation. But 500 MW onwards this practice was discarded because the structural design and cost required to be done is much higher than the conventional one. Therefore a method was involved to lift the generator which has no bearing with the structural load bearing capacity. Use of Portal crane and more popular is strand jack method gained popularity for lifting stator . We will discuss the same with photographs on later dates. A brief description of 500 MW generator  is given below for new comers.

The two-pole generator uses direct water cooling for the stator winding, phase connectors and bushings and direct hydrogen cooling for the rotor winding. The generator frame is pressure-resistant and gas tight and equipped with one stator end shield on each side. The hydrogen coolers are arranged vertically inside the turbine end stator end shield.

The generator consists of the following components:

• Stator

Stator frame ,End shields ,Stator core ,Stator winding and Hydrogen coolers.

• Rotor

Rotor shaft , Rotor winding, Rotor retaining rings and Field connections

• Bearings

Shaft seals

The following additional auxiliaries are required for Generator operation :

• Oil system , Gas system , Primary water system and  Excitation system.

Cooling System.

-The heat losses arising in the generator interior are dissipated to the secondary coolant (raw water,

condensate etc.) through hydrogen and primary water.

-The hydrogen is circulated in the generator interior in a closed circuit by one multi-stage axial-flow fan arranged  on the rotor at the turbine end. Hot gas is drawn by the fan from the air gap and delivered to the coolers, where it is re-cooled and then divided into three flow paths after each cooler.

-For direct cooling of the rotor winding, cold gas is directed to the rotor end windings at the turbine and exciter ends. The rotor winding is symmetrical relative to the generator centre line and pole axis. Each coil quarter is divided into two cooling zones.

For cooling of the stator core, cold gas is admitted to the individual frame compartments via separate cooling gas ducts. From these frame compartments the gas then flows into the air gap through slots in the core where it absorbs the heat from the core.

The treated water used for cooling of the stator winding phase connectors and bushings is designated as primary water in order to distinguish it from the secondary coolant (raw water, condensate, etc.). The primary water is circulated in a closed circuit and dissipates water is circulated in a closed circuit and dissipates the absorbed heat to the secondary cooling water in the primary water cooler. The pump is supplied with hot primary water from the primary water tank and delivers the water to the generator via the coolers. The cooled water flow is divided into two flow paths .

Stator Frame

 The stator frame consists of a cylindrical centre section and two end shields which are gas-tight and pressure-resistant. The stator end shields are joined and sealed to the stator frame with an O-ring and bolted flange connection. The stator frame accommodates the electricity active parts of the stator, i.e., the stator core and the stator windings.

The stator core is stacked from insulated electrical sheet-steel laminations and mounted in supporting rings over insulated dovetailed guide bars. Axial compression of the stator core is obtained by clamping fingers, pressure plates, and non-magnetic through-type clamping bolts, which are insulated from the core.

The rotor shaft is a single-piece solid forging manufactured from a vacuum casting. Slots for insertion of the field winding are milled into the rotor body. The longitudinal slots poles are obtained. The rotor poles are designed with transverse slots to reduce twice system frequency rotor vibrations caused by deflections in the direction of the pole and neutral axis.

The hydrogen cooler is a shell and tube type heat exchanger which cools the hydrogen gas in the generator. The heat removed from the hydrogen is dissipated through the cooling water. The cooling water flows through the tubes, while the hydrogen is passed around the finned tubes.

The sleeve bearings are provided with hydraulic shaft lift oil during start-up and turning gear operation. To eliminate shaft currents, all bearings are insulated from the stator and base plate, respectively. The temperature of the bearings is monitored with thermocouples embedded in the lower bearing sleeve so that the measuring points are located directly below the BABBITT. Measurement and any required recording of the temperatures are performed in conjunction with the turbine supervision. The bearings have provisions for fitting vibration pickups to monitor bearing vibrations.

Typical 500MW Generator Specification

KW 500,000 ; KVA 588,000 Hz 50 ; R.P.M 3000 ; P.F. 0.85 LAG

Stator  : Volts 21000 ;  Amps 16200 ;  Phase 3; Conn. Y Y ;  Spec. IEC-34

Rotor  :  Amps 4040 ; Volts 340  : Coolant Hydrogen & Water; Gas Pressure 3.5 Kg/cm2 (g)

         Typical 500MW Generator cross section

 Typical 500MW Generator outline drawing and 660 MW  generator. Difference of construction

will be outlined later.

courtesy  BHEL

Continued to PART -II

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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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