Vocational Training Report Turbine Blade Shop-Block 3 Bharat Heavy Electricals Limited Ranipur,Haridwar (Uttrakhan

1. Vocational Training Report
Turbine Blade Shop-Block 3
Bharat Heavy Electricals Limited
Ranipur,Haridwar (Uttrakhand)
Submitted By: Submitted To:
Yuganter Rawat Mr.Hitendra Bankoti
B-Tech 3rd
year
Amrapali Institute of technology and science,Haldwani
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3. ACKNOWLEDGEMENT
“An engineer with only theoretical knowledge is not a complete
engineer. Practical knowledge is very important to develop and apply
engineering skills”. It gives me a great pleasure to have an
opportunity to acknowledge and to express gratitude to those who
were associated with me during my training at BHEL.
I am very great-full to Mr. R.M. Meena for providing me with an
opportunity to undergo training under his able guidance.
Furthermore, special thanks to Mr. Pradeep Pandey for his help and
support in haridwar. Last, but not the least, I would also like to
acknowledge the immense pleasure, brought about by my friends
Adhar,Ashis,Rohit as they pursued their training along with me. We
shared some unforgettable moments together.
I express my sincere thanks and gratitude to BHEL authorities for
allowing me to undergo the training in this prestigious organization. I
will always remain indebted to them for their constant interest and
excellent guidance in my training work, moreover for providing me
with an opportunity to work and gain experience.
THANK YOU
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4. B.H.E.L- An Overview
BHEL or the Bharat Heavy Engineering Limited is one of the largest
engineering and manufacturing organizations in the country and the
BHEL, Haridwar is their gift to Uttaranchal. With two large
manufacturing plants, BHEL in Haridwar is among the leading
industrial organizations in the state. It has established a Heavy
Electrical Equipment Plant or HEEP and a Central Foundry Forge
Plant or CFFP in Haridwar.
The Heavy Electrical Equipment Plant in Haridwar designs and
manufactures turbo generators, AC and DC motors, gas turbines and
huge steams. The Central Foundry Forge Plant in Haridwar deals with
steel castings and manufacturing of steel forgings.
The BHEL plants in Haridwar have earned the ISO - 9001 and 9002
certificates for its high quality and maintenance. These two units have
also earned the ISO - 14001 certificates. Situate in Ranipur near
Haridwar, the Bharat Heavy Engineering Limited employs over 8,000
people.
BHEL is an integrated power plant equipment manufacturer and one
of the largest engineering and manufacturing companies in India in
terms of turnover. BHEL was established in 1964, ushering in the
indigenous Heavy Electrical Equipment industry in India - a dream
that has been more than realized with a well-recognized track record
of performance. The company has been earning profits continuously
since 1971-72 and paying dividends since 1976-77 .BHEL is
engaged in the design, engineering, manufacture, construction,
testing, commissioning and servicing of a wide range of products and
services for the core sectors of the economy, viz. Power,
Transmission, Industry, Transportation, Renewable Energy, Oil & Gas
and Defence.BHEL has 15 manufacturing divisions, two repair units,
four regional offices, eight service centres, eight overseas offices and
15 regional centres and currently operate at more than 150 project
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5. sites across India and abroad. BHEL places strong emphasis on
innovation and creative development of new technologies. Our
research and development (R&D) efforts are aimed not only at
improving the performance and efficiency of our existing products,
but also at using state-of-the-art technologies and processes to
develop new products. This enables us to have a strong customer
orientation, to be sensitive to their needs and respond quickly to the
changes in the market.
The high level of quality & reliability of our products is due to
adherence to international standards by acquiring and adapting some
of the best technologies from leading companies in the world
including General Electric Company,Alstom SA, Siemens AG and
Mitsubishi Heavy Industries Ltd., together with technologies
developed in our own R&D centres. Most of our manufacturing units
and other entities have been accredited to Quality Management
Systems (ISO 9001:2008), Environmental Management Systems
(ISO 14001:2004) and Occupational Health & Safety Management
Systems (OHSAS 18001:2007).
BHEL has a share of around 59% in India's total installed generating
capacity contributing 69% (approx.) to the total power generated from
utility sets (excluding non-conventional capacity) as of March 31,
2012. We have been exporting our power and industry segment
products and services for approximately 40 years. We have exported
our products and services to more than 70 countries. We had
cumulatively installed capacity of over 8,500 MW outside of India in
21 countries, including Malaysia, Iraq, the UAE, Egypt and New
Zealand. Our physical exports range from turnkey projects to after
sales services.
BHEL work with a vision of becoming a world-class engineering
enterprise, committed to enhancing stakeholder value.
Our greatest strength is our highly skilled and committed workforce of
over 49,000 employees. Every employee is given an equal
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6. opportunity to develop himself and grow in his career. Continuous
training and retraining, career planning, a positive work culture and
participative style of management - all these have engendered
development of a committed and motivated workforce setting new
benchmarks in terms of productivity, quality and responsiveness.
STEAM TURBINE
A
steam turbine is a mechanical device that extracts thermal energy
from pressurized steam, and converts it into rotary motion. Its modern
manifestation was invented by Sir Charles Parsons in 1884. It has
almost completely replaced the reciprocating piston steam engine
(invented by Thomas Newcomen and greatly improved by James
Watt) primarily because of its greater thermal efficiency and higher
power-to-weight ratio. Because the turbine generates rotary motion, it
is particularly suited to be used to drive an electrical generator – about
80% of all electricity generation in the world is by use of steam
turbines. The steam turbine is a form of heat engine that derives much
of its improvement in thermodynamic efficiency through the use of
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7. multiple stages in the expansion of the steam, which results in a closer
approach to the ideal reversible process.
Types
These arrangements include single casing, tandem compound and cross
compound turbines. Single casing units are the most basic style where a single
casing and shaft are coupled to a generator. Tandem compound are used where
two or more casings are directly coupled together to drive a single generator. A
cross compound Steam turbines are made in a variety of sizes ranging from
small 1 hp (0.75 kW) units (rare) used as mechanical drives for pumps,
compressors and other shaft driven equipment, to 2,000,000 hp (1,500,000 kW)
turbines used to generate electricity. There are several classifications for modern
steam turbines.
Steam Supply and Exhaust Conditions
These types include condensing, non-condensing, reheat, extraction and
induction.
Non-condensing or backpressure turbines are most widely used for process
steam applications. The exhaust pressure is controlled by a regulating valve to
suit the needs of the process steam pressure. These are commonly found at
refineries, district heating units, pulp and paper plants, and desalination
facilities where large amounts of low pressure process steam are available.
Condensing turbines are most commonly found in electrical power plants. These
turbines exhaust steam in a partially condensed state, typically of a quality near
90%, at a pressure well below atmospheric to a condenser.
Reheat turbines are also used almost exclusively in electrical power plants. In a
reheat turbine, steam flow exits from a high pressure section of the turbine and
is returned to the boiler where additional superheat is added. The steam then
goes back into an intermediate pressure section of the turbine and continues its
expansion.
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8. Casing or Shaft Arrangements
Turbine arrangement features two or more shafts not in line driving two or more
generators that often operate at different speeds. A cross compound turbine is
typically used for many large applications.
Principle of Operation and Design
An ideal steam turbine is considered to be an isentropic process, or constant
entropy process, in which the entropy of the steam entering the turbine is equal
to the entropy of the steam leaving the turbine. No steam turbine is truly
“isentropic”, however, with typical isentropic efficiencies ranging from 20%-
90% based on the application of the turbine. The interior of a turbine comprises
several sets of blades, or “buckets” as they are more commonly referred to. One
set of stationary blades is connected to the casing and one set of rotating blades
is connected to the shaft. The sets intermesh with certain minimum clearances,
with the size and configuration of sets varying to efficiently exploit the
expansion of steam at each stage.
Turbine Efficiency
To maximize turbine efficiency, the steam is expanded, generating work, in a
number of stages. These stages are characterized by how the energy is extracted
from them and are known as impulse or reaction turbines. Most modern steam
turbines are a combination of the reaction and impulse design. Typically, higher
pressure sections are impulse type and lower pressure stages are reaction type.
Impulse Turbines
An impulse turbine has fixed nozzles that orient the steam flow into high speed
jets. These jets contain significant kinetic energy, which the rotor blades, shaped
like buckets, convert into shaft rotation as the steam jet changes direction. A
pressure drop occurs across only the stationary blades, with a net increase in
steam velocity across the stage.
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9. Reaction Turbines
In the reaction turbine, the rotor blades themselves are arranged to form
convergent nozzles. This type of turbine makes use of the reaction force
produced as the steam accelerates through the nozzles formed by the rotor.
Steam is directed onto the rotor by the fixed vanes of the stator. It leaves the
stator as a jet that fills the entire circumference of the rotor. The steam then
changes direction and increases its speed relative to the speed of the blades. A
pressure drop occurs across both the stator and the rotor, with steam
accelerating through the stator and decelerating through the rotor, with no net
change in steam velocity across the stage but with a decrease in both pressure
and temperature, reflecting the work performed in the driving of the rotor.
SPECIFICATIONS OF MACHINES AVAILABLE IN BLOCK-III:
Vertical Boring Machine :
 Max diameter of work piece accommodated :10000mm to
12500mm
 Max height of work piece :5000mm
 Diameter of table :8750mm
 Max travel of vertical tool head RAM slides :3200mm
 Max travel of vertical tool heads from centre of
Table :5250mm
 Max weight of work piece :200 T
For N<=6rpm;100T for any speed
 Diameter of boring spindle of combined head :160mm
 Travel of boring spindle :1250mm
 Taper hole of boring spindle :100metric
Centre Lathe :(Biggest of all BHEL)
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10.  Max diameter over bed :3200mm
 Max diameter over saddle :250mm
 Length between centers :16m
 Max weight of work piece :100 T
 Spindle bore :96mm
CNC Lathe :
Manufacturer: Safop, Italy
 Swing over carriage :3500mm
 Centre distance :9000mm
 Weight capacity :120 T
 Spindle power :196KW
 External chucking range :250-2000mm
 Hydrostat steady range :200-1250mm
 Max spindle rpm :200
 CNC system :SINUMERIK
840D
CNC Indicating stand :
Manufacturer : Heinrich Georg, Germany
 Turning diameter :5.3m
 Turning length :15m
Weight capacity :160 T
CNC Vertical Borer :
Manufacturer : M/S Pietro Carnaghi, Italy
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11.  Machine model :AP 80TM-
6500
 Table diameter :6500mm
 Max turning diameter :8000mm
 Min boring diameter :660mm
 Max height for turning and milling :7000mm
 Table Speed :0.2-50 rpm
 Table load capacity :200 T
 Milling spindle speed :3.4-3000 rpm
 Spindle taper :BT 50
 CNC system :SINUMERIK 840D
CNC Facing Lathe : KH-200-CNC
 Swing over bed :2300mm
 Swing over carriage :1800mm
 Max distance between faced plate and carriage :2000mm
 Max weight of job held in chuck :6000kg
 Face plate diameter :1800mm
 Spindle speed :1.4-400rpm
 Main spindle drive :95.5KW
Step boring Machine :
 Max boring diameter :2500mm
 Min boring diameter :625mm
 Table :4000mmx4000mm
 Max weight of job :100 T
Headstock travel :4000mm
Double Column Vertical Borer :
 Table diameter :4000mm
 Max travese of cross rail :4250mm
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12.  Max weight of work piece :4200mm
 Max weight of job :50 T
CNC Skoda Horizontal Borer :
 Spindle diameter :200mm
 Taper spindle :BT 50
 RAM size :450x450mm
 RAM length :1600mm
 Spindle length :2000mm
 Headstock :5000mm
 Table :4000x3500mm
 CNC system :SIMENS 850mm
 Job : I.P. Outer
Horizontal Borer : LSTG 8006
 Spindle diameter :250mm
 Height of machining bed :600mm
 Max boring depth with spindle :2000mm
 Max extension of RAM :1600mm
 Width of bed guide ways :2500mm
 Actual length of headstock with vertical lift :2150mm
 Actual length of column horizontal feed :15000mm
 Lowest position of spindle axis upon bed guideways :1475mm
 Machine weight with electrical equipments :140 T
 Height of machine :10.3m
CNC Lathe : 1-120
Manufacturer : Ravensburg
 Main spindle bore :150mm
 Distance between centers :12m
 Turning diameter over bed cover :1400mm
 Turning diameter over carriage :1100mm
 Workpiece weight unsupported :4000kg
 Workpiece weight between centers :20 T
Centre Lathe : 1-23
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13. Manufacturer : K3TC, USSR
 Max diameter over bed :1250mm
 Max diameter over saddle :900mm
 Length between centers :6300mm
 Max weight of work piece :25 T
 Spindle bore :80mm
 Machine wattage :55KW
Horizontal Boring Machine : 1-28
 Diameter of spindle :150mm
 Working surface of table :2250x1250mm
 Max travel of table :1200mm
 Max vertical travel of headstock :2000mm
Horizontal Boring Machine :
 Boring spindle taper :BT50
 Boring spindle diameter :160mm
 Headstock vertical travel :3000mm
 Longitudinal RAM travel :700mm
 Longitudinal spindle travel :1000mm
 Column cross travel :10m
 Rotary table travel :3000mm
 Table load :40 T
Horizontal Boring Machine : 1-11
 Boring spindle internal taper material :200
 Boring spindle diameter :320mm
 Max spindle travel :2500mm
 Vertical head travel :6000mm
 Transverse column travel :6000mm
 Max longitudinal column travel :800mm
 Machine wattage :90KW
Double Column Rotary Table Vertical Borer :
 Max diameter of work piece accommodated :10m
 Max height of work piece accommodated :5m
 Diameter of table :8.75m
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14.  Max travel of vertical tool head RAM slides :3.2m
 Max travel of vertical tool head from centre of table :5.25m
 Max weight of work piece :200T for N<=8rpm;100T for any speed
 Diameter of boring spindle of combined head :160mm
 Travel of boring spindle :1250mm
 Taper hole of boring spindle :100mm
Horizontal borer : 1-2
 Spindle diameter :220mm
 Working surface :8100 x 5000mm
 Max vertical travel :3mm
 Max transverse travel of column :6m
 Max longitudinal travel of column :6m
 Max longitudinal travel of spindle :1.8m
CNC Lathe : 2-360
Manufacturer : Hoesch
 Max load :320 T
 Max length between centers :18m
 Swing over bed :3.2m
Horizontal Borer : 2-198
 Spindle diameter :220mm
 Max vertical travel :3m
 Max transverse travel of column :6m
 Max longitudinal travel of column :6m
 Max longitudinal travel of spindle :1.8m
 Working surface :1800x500mm
Creep Feed Grinding Machine :
 Diameter of job :2m
 Job height :2.4m
 Table rpm :10rpm(max)
 Table diameter :2050mm
 Swing diameter :2500mm
 CNC control :SIEMENS-3GG
Broaching Machine :
 Broaching capacity :32 T
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15.  Broaching stroke :10.3m
 Broaching slide width 1500mm
 Broaching specific cutting stroke :1.25m/min
 Broaching specific return stroke :60m/min
 Max diameter of disc :2300mm
 Max move of table :600mm
 Helix angle/skew angle setting :+45/-45
 Cone angle :0-20
CNC Lathe :
Manufacturer : Innse Berardi, Italy
 Swing over carriage :1500mm
 Swing over bed :2000mm
 Capacity :30 T
 Cost :16 crore
 CNC system :SINUMERIK 840D
Over Speed Balancing of Turbines :
Main features :
 Type of pedestials :DH 90/DH 12
 Rotor weight :Min 4 MT, Max 320 MT
 Rotor diameter :Max 6900mm
 Rotor journal diameter :Min 250mm,Max 950mm
 Bearing centre distance :Min 3000mm,Max 15700mm
 Balancing speed :180-3600rpm
 Min vibration limit :1 micron
 Max vacuum :1 torr
Tunnel Features :
 Tunnel length :19000mm
 Tunnel diameter :6900mm
 Max thickness of tunnel :2500mm
 Steel plate thickness :32mm
 Cost of balancing equipment(FE) :444 lakhs
 Total cost of balancing tunnel :770 lakhs
Main Features of Drive :
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16.  Drive motors (2 no.) :950V DC, 500rpm,3.5
MW each
 Total drive power :7 MW(2x3.5)
MG set of Drive :
 Synchronous motors :11 KV,9MW,50Hz,500rpm
 DC Generator (2 no.) :950V,500rpm,3.8MW each
3d coordinate measuring machine in new blade shop:
Model refrence: 22129 LIETZ Germany
Plan no 3-068
Measuring range:
X axis 2200mm
Y axis 1200mm
Z axis 900 mm
Volumetric error: (max) 1.5 micron
Resolution: 0.05 micron
Max weight of job: 2250 kg
Accuracy: 1.5+L/350 micron
Application: dimensional and profile
management of turbine moving and guide blades
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17. HOW IT WORKS
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18. 18

19. LProtor with moving blades various blade profiles
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20. STEAM FLOW THROUGH STEAM TURBINE
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25. Modernization of Facilities:
 CNC Lathe for LPRotor from SAFOP,ITALY
 CNC Horizontal Boring machine for machining of casing from PAMA,
ITALY
 CNC Indicating Stand for LP Rotor Blade machining from GEORG,
GERMANY
 CNC Fir Tree Root Milling machine
 CNC Gantry Milling machine
Major Facilities for New Turbine Shop:
 CNC VBorer-Table diameter-7500mm
 CNC VBorer-Table diameter-4000mm
 CNC H Borer Spindle Diameter-200mm,160mm
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26.  CNC Lathe capacity-120 T,80T
 CNC Fir Tree Root Milling machine
 CNC Gantry Milling machine
Highlights:
 Imported Substitutions :
 Hybrid burner for gas turbine
 E ring for gas turbine
 Deep hole drilling in HP outer casing supplied by Machine
Shop, CFFP
 Process Improvement :
 Slitting of casing, thrust rings, GT rings on Band Saw
milling machine, thus saving the time on critical machines
such as Ram Borers
 Using KOMET drilling systems, the productivity in joint
plane drilling of casing and LPRotors has increased
 Seeing the congestion on KOOP milling machine, a new
work center machine called RAMBHOR machine(No.
2473
Tool Brands:
 Widia
 Sandwick
 Seco
 Isear
 Addisson
26

27.  Guhring
 Indian tools
 Mitutoyo
Tool Instruments:
 Die ring spanner
 Hack saw frame
 Burr cutter
 Solid tap (carbide)
 Hand tap
Grinding Cutters:
 Combination cutter-140x40mm
 Fillet cutter-160x32mm
 Hand mill cutter
 End mill cutter
 Internal profile cutter
 Shell end mill cutter-63x80mm
 Ball nose
 Slab mill
500 MW Steam Turbine:
 HP Turbine:
 Module :H30-100-2
 Steam Pressure :170Kg/sq.cm
 Steam temperature :537 deg.cel
 Reheating temperature :537 deg.cel
 Weight :86400 Kg
 Length of Rotor :4.61m
 Height :2.15m
 LP Turbine:
 Module :N30-2x10sq.m
 Weight :3.5 T
 Length of Rotor :8.7m
 Width :10.7m
 Height :4.6m
 IP Turbine:
 Length :4.425m
 Width :5m
 Height :4.8m
 Steam pressure :41Kg/sq.cm
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28.  Steam temperature :537 deg.cel
Milling Cutters:
1) Side end face milling cutter
2) Interlocking side and face milling cutter
3) Shell end mill cutter
4) Metal slitting saw
5) Single angle milling cutter
6) Double unequal angle milling cutter
7) Double equal angle milling cutter
8) Keyway milling cutter
9) Milling cutter for chain wheels
10) Single corner rounding milling cutter
11) Convex milling cutter
12) Concave milling cutter
13) T slot milling cutter with plane parallel shank
14) T slot milling cutter with Morse taper shank having tapered end
15) Cylindrical milling cutter
16) Slot milling cutter with parallel shank
17) End mill with parallel shank
18) Ball nosed end mill with parallel shank
19) Flat end tapered die sinking cutter with plane parallel shank
20) Ball nosed taper die sinking cutter with plane parallel shank
21) Slot milling cutter with morse tapered shank having tanged end
22) End mill with morse tapered shank having tanged end
23) Ball nosed end mill with morse tapered shank having tanged end
24) Flat end tapered die sinking cutter with morse tapered shank having tapped
end
25) Ball nosed tapered die sinking cutter with morse tapered shank having
tapped end
26) Slot milling cutter with morse tapered shank having tapped end
27) End mill morse tapered shank having tapped end
28) Ball nosed mill morse tapered shank having tapped end
29) Roughing end mill with parallel shank finishing type
30) Roughing end mill with parallel shank roughing type
31) Slot milling cutter with 7/24 taper shank
32) End mill with 7/24 taper shank
33) Ball nosed end mill with 7/24 taper shank
34) Woodruff key slot milling cutter with parallel shank
35) Screwed shank slot drill
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29. Major Components of Steam Turbine:
 LP Rotor
 LP Inner Casing Upper Half
 LP Inner Casing Lower Half
 LP Outer Casing Upper Half
 LP Outer Casing Lower Half
 IP Rotor
 IP Inner Casing Upper Half
 IP Inner Casing Lower Half
 IP Outer Casing Upper Half
 IP Outer Casing Lower Half
 HP Rotor
 HP Inner Casing Upper Half
 HP Inner Casing Lower Half
 HP Outer Casing Upper Half
 HP Outer Casing Lower Half
 Diffuser
 GBC (Guide Blade Carrier)
 IVCV (Intercept Valve Control Valve)
 ESVCV (Emergency Stop Valve Control Valve)
Auxiliary Parts of Steam Turbine:
1) Valve Seal
2) U-Ring
3) Piston Rod
4) Base Plate
5) Sealing Ring
6) Liner
7) Guide Ring
8) Valve Cover
9) Guide Blades :
 Fixed Blades
 Moving Blades
10) Support
11) Bearing
12) Bearing Shell
13) Angle Ring
14) Sleeve
15) Pin Taper (25x140)
16) Journal Bearing Shell
17) Casing
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30. 18) Guide bush
19) Piston (500MW)
20) Valve Cone
21) Yoke
22) Mandrel
23) Support Ring
24) Thrust Ring
25) Adjusting Ring
26) Shaft Sealing Cover
Types of Blades:
 T2 blades
 T4 blades
 TX blades
 3DS blades
 F- blades
 GT-Compress blades
 Brazed blades
 Russian design blades
 Z-Shroud blades
 Compressor blades (Sermental coated)
LP Moving blade 500MW
New Blade Shop:
 First Generation Blades :
 T2 Profile Blades
 Cylindrical Profile Blades (1970)
 Second Generation Blades :
 T4 Profile Blades
 Cylindrical Profile Blades ( late 1980)
 1% Gain in Stage Efficiency over T2 Profile Blades
 TX Profile Blades
 Cylindrical Profile Blades ( late 1990)
Gains :
 Reduces Profile Losses
 0.2% Gain in Stage Efficiency over T4 Profile Blades
Applications :
 Middle Stage Of H.P. and I.P Turbine
 Initial Stage of L.P. Turbine
30

31.  3DS Blades :
Gains :
 Reduces Secondary Flow Losses
 0.5 – 1.0% Gain in Stage Efficiency over TX Profile Blades
Application :
 Initial Stage of H.P. and I.P Turbine
 F- Blades
Gains :
 Reduces Indirect Flow Losses
 0.5 – 1.0% Gain in Stage Efficiency over TX Profile Blades
Applications :
 Rear Stage of H.P. and I.P Turbine
 Middle Stage of L.P. Turbine
Sequential operation for machining of TX blades:
Operation Machine
1) Blanking
2) Rhomboid machining
Band saw
CNC rhomboid machine
cell
3) Removal of tech allowance/parting off band saw
4) Root machining CNC high speed root machining
5) Profile and expansion angle(internal and
external)
CNC heavy/light duty machine or
CNC profile and fillet machining
center
6) Shroud copying CNC heavy/light duty machine
7) Taper grinding CNC creep feed grinding
machine
8) Grinding and polishing Polishing machine
9) Final fitting of blades -
10)Vibro finishing of blades Vibro finishing equipment
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32. 11)Final inspection -
Sequential operation for machining of 3DS and F blades:
Operation Machine
1) Blanking Band saw
2) Preparation of technological ends for work
piece holding
CNC machining center
3) Complete blade machining(with normal
shroud/Z shroud)
CNC 5 axis machining centre
4) Inspection 3D CMM
5) milling off technological ends at root and
shroud radius machining
CNC machining centre
6) Fitting -
7) vibro finishing for surface finishing
improvement
Vibro finishing equipment
8) Inspection -
Number of advance design blades:
Blades 250MW 500MW
TX Profile blade 10390 6820
F and 3DS blade 3100 2852
Free standing blade 224 252
NON- DESTRUCTIVE TESTING (Liquid penetration ,magnetic
flaw&radiography)
Failure of the turbine blades was one of the challenges addressed with the help of BHEL by modifications
of LP stage-5 blade, shroud modifications etc., and based on its success, the same technique was used
for other plants to sort out inherent problems. Grid-induced Outages Grid disturbance induced outages
were overcome by house load schemes and in one-month viz., May 1998, as many as 150 house load
operations took place and units operated withstanding these transients. Healthiness of the control
system and other equipment to withstand external grid transients was remarkable. The sharp corner in
the root section of the blade causes the blade to crack. Failure of the turbine blades was one of the
32

33. challenges addressed with the help of BHEL by modifications of HP stage-5 blade, shroud modifications
etc., and based on its success, the same technique was used for other plants to sort out inherent
problems. The material used was 12Cr-Mo martensitic steel,which is a very high temperature resistant
material. The microstructure was observed was tempered martensitic structure. These turbine blades
were collected from Madras Atomic Power Station (MAPS) for analysis. These blades were found to be
failed. These blades were used for the present investigation of defects using ultrasonic phased array and
X-ray radiography techniques. Turbine blades are known to fail due to tempered martensite
embrittlement, fatigue, fretting, high temperature creep age hardening, firtree design, high residual
stresses etc.
Chemical compositions of the turbine blade:
Element Weight %
Sulphur 0.019 to 0.03
Phosphorus 0.019 to 0.028
Carbon 0.20 to 0.24
Chromium 12.8 + 1.2
Manganese 0.45 to 0.54
Silicone 0.30 to 0.43
Nickel 0.40 to 0.52
Vanadium 0.05
Molybdenum 0.1 to 0.13
Iron Balance
TURBINE MATERIALS
In the case of turbine, the advancement in steam conditions mainly
affects its high pressure (HP) and intermediate pressure (IP)
sections.As a result, the associated rotations as well as stationary parts
of these sections experience more severe service conditions than that
of conventional sets. Since they operate well within the creep range,
their design is based primarily on the long-term creep strength ofthe
material, but the stress levels during steady and non-steady operating
conditions, particularly during 593°C contemplate the use of 12Cr
steel rotor with steam cooling to bring the rotor temperature down
33

34. to 566°C, where its creep strength is adequate to meet the design
pressure. However, presently several super 12Cr steels with much
superior creep resistance are available and they should also be
considered before a final decision is taken. Above 593°C steam
temperature, X12CrMoWVNbN 10 11 and austenitic stainless steel
must be considered. Amongst the austenitic steels, A286 and
X8CrNiMoBNb 16 16 offer better creep strength for an HP rotor of
advanced sets operating at 649°C. One of the rotor-related problems is
the maximum size that can be produced from the 12Cr and austenitic
steels. Due to severe segregation in conventional ingots, the size of
the austenitic steel rotors used in earlier supercritical units was limited
to small size, as a result of which, it became necessary to divide the
HP turbine into two stages. It is estimated that a large advanced plant
would require a one-piece super-alloy HP rotor forging
weighing 11,300 kg with a barrel diameter of 890mm. Similarly, a
double-flow reheat rotor made of 12Cr steel is expected to be about
1150mm in diameter and 31,750 kg in weight, which would
require to start with an ingot size of 63,500 kg . Significant progress
has been made, in recent years, in increasing the size as well as the
quality of the forging by employing modern steel making techniques
such as low sulfur silicon deoxidation (low S), vacuum oxygen
decarburization (VOD), vacuum carbon deoxidation (VCD), central
zone refining (CZR), electro slag hot topping (ESHT) and electro
slag remelting (ESR). By employing these techniques, either
individually or in combination, production experience with low-alloy
ferritic [39], 12Cr as well as austenitic steels [4, 40] demonstrate that
the rotors of the candidates materials can be made to the required size
and quality without experiencing much
problems.
Blading
Conventional 12CrMoV steel blades are adequate to meet the steam
temperature at 566°C. But a wide variety of high-temperature blade
materials with proven service performance in large gas turbines are
available, and they should be considered for more advanced steam
conditions. These include super 12Cr steels, austenitic steels, Nimonic
80A, 90, 105, 115, In718 and precision casting alloys such as Udimet
500 and IN 738LC.
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35. LP Rotor
The principal requirements of material for lowpressure (LP) rotor are
high yield strength to withstand the high stress imposed on it by long
blades and high fracture toughness to minimize subcritical flaw
growth so as to avoid the possibility of fast fracture. 3.5NiCrMoV
steel is widely used for LP rotor throughout the power industry. To
avoid temper embrittlement, the maximum operating temperature of
the LP rotor made of this steel is generally limited to about 350°C [9].
The inlet steam temperature to LP turbine of the supercritical
units, on the other hand, is dictated by the exhaust steam from the
second IP section. The IP-LP crossover temperature from advanced
supercritical units at steam temperatures of 593°C and above
would be 400-455°C [9]. To maintain the inlet steam temperature of
LP turbine at its present maximum allowable limit, it would be
necessary to cool the steam either through cooling of the rotor
or by adding an additional stage of expansion to the IP turbine. The
latter approach would be a difficult design task, as it requires usage of
long blades at high temperature, whereas the former approach has to
sacrifice a part of the thermal efficiency. Another approach to the
problem would be to render LP rotor material more resistant to temper
embrittlement [41]. Efforts are, therefore, being made to improve the
fracture toughness of the IP rotor steel by improved steel making
technology and closer control of chemical composition. The
interaction between Mn, Si, P and Sn was shown to have promoted
the degree of temper embrittlement. Resistance to temper
embrittlement of 3.5NiCrMoV rotor steel with low Mn and low Si
contents was found to have greatly improved as compared to
conventional steel [9]. By utilising the modern steel making
technologies, it is now possible to decrease both Mn and Si contents
to levels of- 0.002%.
35

36. ELECTRICALMAINTAINENCEMECHANICALMAINTAINENCE
STORES
TOOL-CRIB
TROLLEYTRACK
STORES
CNCMAINTAINENCE
TBMBLANKINGMACHINE
RAILWAY TROLLEY TRACK
HEAVYMACHINESHOPBAY-1
HEAVYMACHINESHOPBAY-2
TURNINGANDMILLINGSECTIONBAY-3
TBMBAY-4
36

37. TROLLEY TRACK
ASSEMBLYHEAVYBAY-1MACHINESHOP
G-TASSEMBLYASSEMBLYAREABAY-2BLADEASSEMBLYHEAVYMACHINESHOP
RAILWAY TROLLEY TRACK
GOVERNINGANDMEDIUMMACHINESHOP
TBMLPBLADESECTIONBAY-4
GOVERNINGASSEMBLYTESTING(HYDRO/STEAM)
TOOL-ROOMBAY-4
LIGHTMACHINESHOPBAY-3
LAYOUT OF BLOCK-3 WAYFROM BLOCK-2
37
E
S
W
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