PROJECT

CUM
INTERNSHIP REPORT
L&t-mhi
Turbine generators pvt. Ltd.

SUBMITTED BY:Anurag maheshwari

Dayalbagh educational institute
Agra

Preface

Acknowledgement
First of all, I am highly grateful to my institute for giving me this
wonderful opportunity to accomplish my training in this worldclass company.
Since the list is endless, yet I would like to thank some key
people who certainly made my training successful.
2

I would like to thank Ms. Poorvi Mehta for giving me the chance
to fulfil my internship in this privileged company.
I would like to thank Mr. Aloke Sarkar( General ManagerProduction shop) for giving me valuable guidance throughout the
training.
I would like to thank Mr. Rajneesh Bajaj, Mr. Sanjay Narang, Mr.
Devdutt, Mr. kaushik Das, Mr. Chetan Patil, Mr. Bharat Pawar, Mr.
Sanjay Verma, Mr. Abhilash Dubey, Mr. Rajeev Vishwakarma, Mr.
N.K. Dey for their valuable guidance during induction program.

CONTENT

L&T MHI TURBINE & GENERATOR

COMPANY PROFILE:
Larsen & Toubro Limited (L&T) is a technology, engineering, construction and
manufacturing company. It is one of the largest and most respected companies in India's
private sector. L&T was founded in Bombay (Mumbai) in 1938 by two Danish engineers,
Henning Holck-Larsen and Soren Kristian Toubro. Both of them were strongly
committed to developing India's engineering capabilities to meet the demands of
industry.

More than seven decades of a strong, customer-focused approach and the

continuous quest for world-class quality have enabled it to attain and sustain leadership
in all its major lines of business. Considered to be the "bellwether of India's engineering
sector", L&T was recognized as the Company of the Year in 2010.L&T has an
international presence, with a global spread of offices. A thrust on international business
has seen overseas earnings grow significantly. It continues to grow its global footprint,
with offices and manufacturing facilities in multiple countries.

L&T comprises engineering and construction projects, heavy engineering,

Construction, electrical and electronics, information technology, machinery and
industrial products and, L&T power.
L&T has set up an organization focused on opportunities in coal-based, gas-based
and nuclear power projects. L&T has formed two joint ventures with Mitsubishi Heavy
Industries, Japan to manufacture super critical boilers and steam turbine generators.
Larsen & Toubro Limited (L&T) and Mitsubishi Heavy Industries Limited
(MHI) have inked a Joint Venture Agreement for setting up a manufacturing facility to
supply Environment friendly super-critical Steam Turbine & Generator facility
in Hazira .This follows a Technology Licensing and Technical Assistance Agreement for
manufacture of super-critical Turbine & Generator, signed between L&T MHI, and
Mitsubishi Electric Corporation (Mitsubishi Electric).
The product, an integral component of energy efficient coal based power plants, is
expected to meet the demand / supply gap for power plant equipment as envisaged in the
countrys plan for a mega ramp up in power generation capacity using super-critical
technology.

L&T POWER VISION 2015

L&T Power shall be Indias most preferred provider of equipment services and turnkey
solution for fossil fuel-based power plants and a leading contributing to the nations
power generation capacity.

L&T POWER MISSION

L&T Power shall provide products based on efficient and environment-friendly
technology, consistently surpassing customer expectations of quality and on-time
delivery.
L&T Power shall follow fair, transparent and ethical practices in its interactions with all
stake holders and achieve performance excellence by innovation and continuous
improvement in people, product and services.
L&T Power shall foster a culture of care, trust, challenge and empowerment among its
employees.

LMTG MISSION

To emerge as a Market leader in the field of Design, Manufacturing

and Supply of Steam Turbines & Generators, through Continual
Improvement, Employee Involvement, Safety and Respect for
Environment.

Product at LMTG Supercritical

Turbines:
6

Main steam pressure is 24.2 MPa and temperature is between

538 C to 600 C. While re-heater temperature is between 566C
to 600C.
Company designs and manufactures tandem compounded steam
turbine with following arrangement:
Unit size ranges from 500MW to 1000 MW capacity.
The combined HP/IP turbine is applied to 500MW, 600MW and
800MW while separate HP/IP is provided for 1000MW ratings.
500MW has one LP turbine while 600MW has one or two LP
turbines depending on temperature.
800MW and 1000MW have two sets of LP turbines.

Introduction to Steam Turbine

7

Steam Turbine is a rotating machine which converts heat energy of

steam to mechanical energy.
When a steam is allowed to expand through a narrow orifice, it
assumes kinetic energy at the expense of its enthalpy. This kinetic
energy of steam is changed to mechanical (rotational) energy through
the impact or reaction of the steam against the blades.

The
blades are designed in such a way, that the steam will glide on and of
the blade without the tendency to strike it.
As the steam moves over the blades, its direction is continuously
changing and centrifugal pressure exerted as a result is normal to the
blade surface at all points. The total motive force acting on the blade
is thus the resultant of all the centrifugal forces and the change in
momentum. This causes the rotational motion of the blades.

Working Principle
Steam Turbine is one of the principle equipment of a Thermal
Power Plant along with boiler, condenser and heaters which work
together on closed liquid vapour cycle. Steam Turbine is
regarded as a prime mover which rotates the generator for
producing electricity.

The driving force for rotation in turbine is generated by

superheated steam supplied from Boiler. The potential
energy of steam available in the form of pressure,
temperature & heat is converted into kinetic energy in the
row of fixed blades arranged circumferentially to form nozzles.
The high velocity steam generated at the expense of pressure
drop in nozzles passes through another row of blades mounted
on shaft. While passing through this row, the steam reverses its
path which gives rise to change in momentum. This change
develops driving force according to second law of Newton which
states that whenever there is change in momentum an
impressed force is generated which is proportional directly to
rate of change of momentum. Since these blades are mounted on
shaft which is free to rotate, the developed force starts rotating
the shaft.
9

Supercritical Turbine:
L&T MHI Turbine LMTG

Supercritical technology has evolved over the past 30 years. Advancements in metallurgy
and design concepts have made supercritical technology units extremely reliable and
highly efficient. Modern supercritical technology is largely available in Japan and Europe
for Boilers & Turbines ranging up to 1000 MW.
The term "supercritical" refers to main steam operating conditions, being above the
critical pressure of water (221.5 bar). The significance of the critical point is the
difference in density between steam and water. Above the critical pressure there is no
distinction between steam and water, i.e. above 221.5 bar, water is a fluid.
If the steam pressure is greater than 275 bar, then conditions are Ultra Supercritical.
10

Supercritical steam cycle with one reheat:

a b: Condensate cycle up to Deaerator
b c: Boiler feed pump discharge
c d: Feed water heating
d e: Main steam generation
e f: Expansion in turbine
f g: Reheat steam generation
g h: Expansion in turbine
In supercritical cycle, equipment is designed to operate above the critical pressure of
water. Supercritical boilers are once-through where in the feed water enters the
economiser and flows through one path and main steam exits the circuit. Typically
current supercritical units operate at 242 bar main steam pressure, 565C main steam
temperature and 593C reheat steam temperature.

11

Advantages of Modern Supercritical

Technology:
Higher Efficiency:
Supercritical steam conditions improve the turbine cycle heat rate significantly over
subcritical steam conditions. The extent of improvement depends on the main steam and
reheats steam temperature for the given supercritical pressure. A typical supercritical
cycle will improve station heat rate by more than 5%. This results in fuel savings to the
extent of 5%.

Emissions:
Improved heat rate results in 5% lesser fuel consumption and thus 5% reduction in CO2
emission per MWH energy output.

Operational Flexibility:
Supercritical technology units also offer flexibility of plant operation such as:
Shorter start-up times
Faster load change flexibility and better temperature control
Better efficiency even at part load due to variable pressure operation
High reliability and availability of power plant

12

Thermal Cycle Efficiency

The efficiency of a thermal power plant can be expressed as the product of efficiencies of
its subsystem.

power plant = boiler x TG cycle x turbine x generator

Typical values of these efficiencies for a modern thermal power plant employing reheat
and regenerative feed water heating are as follows:

boiler

= 85 to 88%

turbine

= 60 to70%

generator

= 98 to 98.6%

TG cycle

= 44 to 48% (subcritical steam condition)

= 48 to 53% (supercritical steam condition)

powerplant

= 37.5 to 43%

Boiler , Turbine , Generator are fairly high and have almost peaked, only
incremental improvements is taking place.
TG Cycle is lower because it is governed by thermodynamic laws
and depend on MS and RHS Temperature and Condenser Vacuum

13

MAIN COMPONENTS OF A STEAM TURBINE

Blades
Turbine Casing
Rotor
Gland Seals
Couplings
Bearings
Bearing Pedestals
Stop & Control Valves
Governing System
Lubrication System
Drain System
Control & Instrumentation
Turning Gear

14

 Turbine Blades: Blades are the key component of turbine as

conversion of energy to develop driving force takes place therein. The
blades which form nozzles and are fixed are called stationary or guide
blades. The blades mounted on rotor are called moving blades.

Turbine Casing: The guide blades of various stages are held in

the stationary body called casing. It also acts as a cover for
steam passage with connections for steam admission, exhaust
and other flows.

Rotor: It holds the moving blades of various stages in the

grooves machined in it.

Gland Seals: Since turbine casing and rotor are respectively

stationary and rotating parts, there is bound to be clearance
between the two at the ends. The steam tries to escape through
these clearances causing working atmosphere non conducive in
power station for working personnel. To minimize this leakage,
gland seals are provided at the two ends of turbine.

Couplings: They connect the rotor s together and transmit the

torque finally to generator for turning.

15

 Bearings: For supporting the rotors at the two ends to enable

them rotate freely bearings are provided. These bearings are
journal bearings supplied with forced lubrication. Ball bearings are
not suitable as they are not capable to take high loads.
Bearing Pedestal: They support the bearings and house the
lube oil piping and drain oil pipe work. They also enclose various
instrumentation which monitors healthiness of turbine during
operation.

Stop & Control Valves: Turbine does not run at full load at all
the times. Its output is regulated by the electric grid it is
connected. For producing power, matching to varying load
demand, the supply of steam quantity is regulated by control
valves. For taking care of emergency situations stop valves are
also provided which cut of the supply of steam turbine under
such situation. They have only two positions either fully open or
fully closed.

Governing System: An elaborate governing system is provided

for turbine to control the opening of control valves to supply
amount of steam according to varying load demand. The system
senses the load variation in the form of speed change, convert it
to hydraulic signal, amplify it and operate the actuators/
servomotors coupled to control valves. Apart from load changes,
the system also acts during emergency situations to safe guard
the turbine. The system comprises of mix of electronic, electrical
& hydraulic devices
16

 Lubrication System: The TG journal bearings are provided with

forced lubrication so as to form hydraulic film between journal &
bearing surface to support the rotor. During the course of running
the lube oil gets heated up due to friction and need to be cooled,
filtered, purified and pumped back to bearings. A closed
lubrication system consisting of a reservoir, pumps, filter cooler
and purifier forms the essential part of turbine.
Drain System: During non-steady state operating conditions,
the mismatch between turbine component metal temperatures
and steam causes condensation which gets collected in piping &
casings. This condensate is withdrawn by drain system otherwise
it would flash back during load changes and deform casing rotor
and blading.

Control & Instrumentation:

During operation a host of

parameters e.g. steam pressure, temperatures, lube oil pressure

temperature, metal temperatures, expansions, rotor speed &
eccentricity etc. are continuously monitored, supervised through
various instruments and supervisory devices. On the basis of
these control & instruments, safe, reliable and uninterrupted
operation of turbine within defined design limits is ensured.

Turning Gear: A turning gear is provided to rotate the turbine

rotor slowly prior to start-up and after the turbine is shutdown to
allow unified warm-up and cooling, maintain eccentricity and to
prevent the thermal distortion of the rotor. It can be electric
17

motor driven unit and in others oil driven driving unit/hydraulic

motor.

Super Critical Turbine Projects at L&T MHI Turbine

Generator Pvt. Ltd., Hazira
Some of the completed and on-going projects at LMTG.
RAJPURA, Thermal Power Project, Punjab (2 660 MW)
MAHAGENCO, Koradi, Maharashtra (3 660 MW)
JAYPEE Super Thermal Power Project, M.P. (2 700 MW)
APPDCL , Andhra Pradesh (2 x 800 MW )
RABIGH (2 x 120 MW )

Upcoming project:18

 RRVUNL, Rajasthan (2 x 660 MW )

Steam parameters
Main Steam Pressure 242 Bar
Main Steam Temp 565 0C
Reheat Temp 593 0C

Manufacturing and Assembly at

Hazira:The complete turbine manufacturing is done in the following shops:

Fabrication Shop
Machining Shop
Assembly Shop
Blade Shop
Stator coil shop
Ancillary shop
HSBT Facility

Components manufactured in LMTG:1. LP outer casing

19

2.
3.
4.
5.
6.
7.

LP inner casing
HP pedestal
Generator Frame
Main oil tank
Blades
Rotor ( only groove machining for holding blades)

Components of Assembly:1.
2.
3.
4.
5.
6.
7.

G
/H
M
F
W
A
O
C
E
D
S
L
P
IN
B
T
R
U
p
ir
v
s
o
e
V

HIP
LP1 & LP2
Valve assembly
Generator
Rotor
Blades
Pedestal

Steam flow in Turbine

O IL
B
E
BT
F
WA
IL R R V
O
D
R
E
MA
/G
S
E
V
L
ND
O
C
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E
HP
ER
RB
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IN
RB
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P
L
E
IN
HE
E
R
T
A
ro s
C
v e
o
r
RS
/I C
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i eN
p
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B
R
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IP IV A
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V
L

20

DETAILS OF COMPONENTS OF STEAM TURBINE

Turbine Casing
A turbine cylinder is essentially a pressure vessel with its weight
supported at each and on the horizontal central line. It is designed to
with stand hoop stresses in the transverse plane and to be very stif in
the longitudinal direction in order to maintain accurate clearance
between the stationary and rotating parts of the turbine. Due to the
need for internal access casings are split along horizontal centre line
allowing the rotor to be inserted as a complete assembly flanges and
bolting are required to withstand the pressure forces at the joint.
Massive flanges set up thermal stresses and distortion which are
minimized by suitable casing construction. Stress complexities are also
set up by the steam entry, exist, regenerative extraction passages and
gland housings at ends.
HP & IP casings are of cast construction while LP is made by
fabrication of carbon steel plates as it is not exposed to high pressure
& temperature steam. Steam entry, exit, flanges & bolts and other
features are as far as possible symmetrically arranged to have thermal
symmetry and avoid distortion. Steam is admitted in casing and
exhausted from it by pipes in radial orientation. At LP cylinder exhaust
the connection to condenser however normally is rectangular. The
21

steam in casings is therefore required to turn through a right angle to

enter the axial flow blade and exhaust from it and at same time
redistribute itself around circumference. The inlet and exhaust areas
are therefore given sufficient space to allow an orderly flow without
undue pressure loss or flow separation.
Being under pressure, casing design integrity is checked after
manufacture with hydraulic pressure testing to 150% of highest
working pressure wherever possible constructionally.
Forms of Casing:A. Classification According to Direction of Flow
a) Single Flow Casing
b) Double Flow Casing
c) Reversed Flow Casing
B. Classification According to Number of Shells
a) Single Shell Casing
b) Double Shell Casing

Turbine Rotor
Among the steam turbine assemblies, rotor is the most critical one.
They are the vital element involved in conversion of kinetic energy of
steam into mechanical energy of rotation. They run at high speed
depending upon grid frequency (50Hz, 60Hz) and subjected to severe
duty thermally also. They have four major portions: Axially flows path
area - where group of stages are arranged, Gland seal area, bearing
area, coupling ends. Rotors are classified in three broad categories:
A typical rotor consists of four areas: axially flows path area, gland seal
area, bearing area & coupling ends. Based on flow path area, rotor is
classified into1. Disc type rotor There is no axial thrust on moving blades. This
kind of rotor is used in Impulse turbines.
2. Drum type rotor Axial thrust exists on the moving blades. This
kind of rotor is used in Reaction turbines.
Based on rotors critical speed, rotor can be classified into-

22

1. Flexible rotor Rotors having critical speed < Operating speed.

2. Rigid rotor Rotors having critical speed > Operating speed.
Critical speed is that speed of the rotor at which the natural frequency
of the rotor matches with the rotational frequency at the operating
speed. The critical speed of the rotor is a function of diameter of rotor
and distance between the bearings. Critical speed should be at least
10% greater than operating speed.

If the bend shafts are coupled together, coupled ends will

experience Bending moment resulting in excessive vibrations. So to
minimize this bending moment, each shaft is arranged that coupled
faces become parallel. To achieve this condition during initial erection,
bearings are set at diferent heights so as to form a catenary shape.
These bearing heights at diferent locations are determined by HSBT
(High Speed Balancing Test).

Bearing and Bearing Pedestal

The Bearing performs the following functions: It retains the rotor in correct radial position with respect to the
cylinder.

23

 It provides low friction support and withstand dynamic load of

rotating shaft.
It takes away the heat generated due to friction.

Each turbine rotor has two journal bearings for both ends, and one
shaft system has one thrust bearing. They are all of forced lubricated
type, i.e., the load is carried by hydro dynamically generated film of
lube oil. The bearing surface is made of Babbit metal which is an alloy
having low coefficient of friction and an excellent conductor of heat.

For cooling & lubrication, oil is supplied at about 1 to 1.5 bar

pressure through oil pump. Temperature of oil is maintained at 3035C. All the bearings have thermocouples for detecting the metal and
oil drain temperatures. The turbine is incorporated with grounding
device to prevent the shaft voltage trouble.

Bearing Pedestal performs the following functions:

It supports the rotor via journal bearing & maintaining gland

clearances & also inter-stage clearances.

It houses the lubricating & jacking oil supply piping & bearing
oil drain pipe work.

Encloses various instrumentation connections. E.g. bearing

temperature, speed measurement, diferential expansion,
electricity, vibration pick-up, etc.

It covers the rotor coupling.

24

 Oil guard rings provided at the two ends of pedestals prevents

the leakage of oil & vapors.

TURNING GEAR
A Turning Gear is engaged at start-up and shutdown to slowly rotate
the turbine (10-15 RPM). It prevents the uneven expansion which may
distort the turbine rotor and casings. Either it is an Electric motor
driven or an oil driven/ hydraulic motor driven unit.

STEAM CHEST
It is housing for emergency stop valves & governing valves. Steam is
admitted to HP cylinder via the HP piping to these valves. Similarly, it
is there between hot reheat pipes & IP cylinder. It is manufactured
from alloy steel castings to withstand pressure stresses, thermal
stresses & fatigue. IP chest (low pressure) is thinner but larger than HP
chests.

STEAM STRAINER
It is provided in order to avoid foreign solid particles being carried into
turbine with incoming steam. It has 2-5 mm diameter holes. These are
housed in chests provided in main/reheat pipes or in some cases,
these are housed within the stop valve itself.

25

STOP VALVES
Its purpose is to cut-of steam supply during shut down & emergency
trip. It is either fully open or fully closed. These are normally provided
with a pilot valve.

GOVERNOR VALVE
It regulates steam flow to turbine according to load when machine is
synchronized to the grid.

LOOP PIPES
It connects the steam chest to the turbine. The pipes enter the
cylinder in upper half & lower preferably in radial direction.

CROSS OVER PIPES

Steam from IP cylinder is taken to LP cylinder through large size cross
over pipes.

FABRICATION SHOP
This shop is primarily for fabrication of outer casings of the LP
turbine, HP Pedestal & Generator stator frame. Various types of
welding processes like GMAW, GTAW, and SMAW & FCAW. The table

26

below shows the general work system being carried out at the
fabrication department.

INPUTS

Raw materials

PROCESSES

Cutting

like steel plates,

processes like CNC

steel sections, and

cutting, Manual

pipes.

cutting, Oxyfuel
cutting & plasma
cutting.

Semi-finished
parts like castings,

HP Pedestal

Thermal Shield

Main Oil Tank

Weld Edge

like SSB

Fit up process

Welding

Diaphragm

Nozzle ring

welded steam

process

Heat treatment

Shot Blasting

Painting
27

HIP outer
casing with
inlet sleeves

blades, Rateau
blades

SSB, Bladed
diaphragm, HP

preparations
Finished parts

Top Seal Rings

bending.

components, HIP

LP inner & outer

casings

Plate rolling & Pipe

rough machined
outer casings

Plate bending,

OUTPUTS

Generator
stator frame

Some of the other facilities in the fabrication department are as

follows: 1. CNC Cutting
CNC gas cutting cuts C-steel plates up to 250 mm. CNC Plasma
cutting cuts SS Plates up to 38 mm. The machine is pre-loaded
with various profiles like circle, rectangle, etc. it can also be
manually fed shape using USB port present in the main console.
Gas cutting mainly involves pre-heating the material using oxyacetylene mixture and then cutting using a high-pressure oxygen
jet.

2. Bending / Rolling machine

Fully hydraulic machine with the main rotor running all the other
motors and hydraulic components. Upper roll can be moved
vertically up and down to adjust the thickness. Bottom two rolls
can be moved horizontally.

28

3. Hydraulic Press Machine (200T)

There is a main hydraulic motor present along with the oil sump
to control all the operations. Various dies are present which can
be easily fixed to the press as per the requirements. 2 cranes of 1
ton capacity are present on either side of the press in case load
needs to be jot into position.

4. Shot Blasting Booth

It basically consists of impinging steel balls & grit onto the given
job with a large force by using air pressure. It is a fully manually
operated machine. 4 feeders are present which supply the balls
to the machine. The balls after being used are collected using a
feeder belt and reused.
It is used to remove loose particles like dust from the surface of
the job and also used to increase the roughness of the job which
prevents its rusting. Painting needs to be done within 2 hours of
the blasting operation. It is done using pipes fitted with nozzles
and the direction can be easily controlled. Dust collector is
present behind the machine to collect the dirt and scales.

5.

Gas Fired Bogie Hearth Batch type Furnace

It is basically a gas-fired furnace that uses PNG to light up the
furnace. It is used for the purpose of stress relieving/ annealing. It

29

is divided into 8 zones which can be individually controlled by the

controller.

The cycle consists of heating the job at the rate of 80C and then
further heating the job at the rate of 55C till it reaches a temperature
of around 625C. Further it is held at this temperature for about 3.5
hrs. After this it is cooled at the same rates as it is heated. 4
thermostats are present in the furnace to continuously monitor the
temperature. A chimney is provided at the rear to exhaust the
combustion products. 2 blowers are present at the rear to pump in air
for combustion.

Processing in Fabrication shop

Cutting

Inspect
ion

Layout

Inspect
ion

30

Product
ion

Machine Shop
MACHINING WORKS AT LMTG
This shop is the back-bone of whole production. Some of the machine
specifications comprising this shop are as follows:-

Machine Specifications:
Gantry Plano Miller GPM /ST26

Make Schiess
X axis (Columns)

25m

Y axis (Vertical head)

10.85m

Z axis (ram)

0.3m

W axis (Cross rail)

3m

Distance b/w columns

8.5m

Max height of job

5m

Max length

24m

Power

100KW

Torque

9000Nm

31

 HBM 101 /Gen 8

Make Skoda, Czech
Rotary table -150T

X axis (Column)

19m

Y axis (Head stock)

6m

Z axis (ram)

1.3m

Power

100KW

Max speed

2500rpm

VPM/HBM 104/ST6
Make- PAMA, Italy
Rotary table 100T
X axis (Column)
Y axis
Z axis (Ram)
W
Power
Max speed

15m
4.5m
1.2m
1000mm
91KW
2500rpm

VTL 101/ST5
Make HNK, Korea
Max Dia. Of Table
VC of table
Swing dia
Ht. of job
Power

6m
0-40rpm
9.5m
4.5m
171KW
32

Spindle VC
Wt. of job

1000rpm
80MT

VTL 201/ ST9

Make HNK, Korea
Dia
Spindle speed
X
Y (ram)
W (cross rail)
Wt of job
Ht of job
Power
Swing dia

3m
80rpm
-200/ +2225mm
1800mm
2m
30T
3m
60/75KW
4m

PM 202/ ST 13
Make MHI, Japan
X
Y
Z
W
Ht of job
Max speed
Distance b/w columns
Power

9m
4.9m
1m
2.2m
3.05m
4000rpm
4.3m
45KW

PM 201/ Gen 6
Make MHI, Japan
33

5m

4.2m

1m

2.2m

Max speed

4000rpm

Ht of job

3.05m

Distance b/w columns

3.8m

Power

45KW

HBM 202/ UDM2

X
Y
Z
W
Z+W
Speed
Power

5m
2.1m
1.3m
1.4m
1.4m
400rpm
30KW

HBM 201/ UDM 1

X
Y
Z
Max speed
Power

4.6m
3.5m
0.9m
100
33KW

VTL 301/ Gen 7

X
Z
W
Speed
Table dia
Power
Swing dia
Wt
Ht

1000/1700mm
1200mm
1000mm
120rpm
2.5m
33KW
3m
15T
2m
34

 FHB/HBM 203/UDM 5
X
Y
Z
Speed
Power

6.4m
2.67m
1.1m
210rpm
26KW

HBM 103/ST15
Make- Pama , Italy
Rotary table -100T

X
Y
Z
W
Speed
Power

15m
4.5m
1.2m
1m
210rpm
91kW

BLADE SHOP
Turbine Blades
Blades are the key component of a steam turbine as they convert the
potential energy of steam available in the form of pressure,
temperature & heat into rotational kinetic energy. Blades fitted in
stationary casing are called guide blades/stationary blades and those
fitted in the rotor are called moving blades. A group of guide & moving
blade is called a stage of turbine. Blades have three main parts:
35

1. Aerofoil / Profile Section

2. Blade Root
3. Shroud
Aerofoil section:It is the working part of blade where conversion of energy takes place
to generate driving force. According to the shape of aerofoil, blades
are classified into various forms as
1. Cylindrical blades
2. Twisted profile blades
3. Twisted Profile Blade with Reducing Section:
4. 3-Dimensional Blades

BLADE ROOT
Blades are attached to casing or rotor in diferent ways depending
upon the shear area required to resist against the steam bending and
centrifugal force. The common types of arrangement used are as
follows.
36

1. Hook root
2. T- root
3. Fir- tree root
4. Finger /fork root
5. Axial fir tree root

BLADE SHROUD
In order to minimize the steam leakage through the clearance between
moving blade & casing and guide blade & rotor, a cover called shroud
is provided at the tip of blades. The presence of shroud compels the
steam to pass through the working part of blades thereby reducing the
37

tip leakage losses and hence improve stage efficiency. It can be either
riveted by tenon to main blade or it can be integrally machined with
the blade. At present trend is towards integral shroud as it leads to
robust design against vibration besides reducing tip leakages. Long
blades of LP last stages in some designs are without shroud. Such
blades without shroud and individually standing in axial fir tree roots
are called free standing blades.

Turbine blades are subjected to high temperatures, centrifugal &

bending stresses. So, the materials for turbine blades should meet the
following requirements:

Adequate tensile strength for steady centrifugal & bending

stresses

Better creep strength for HP/IP blades exposed to high

temperatures

More

ductility

to

accommodate

stress

peaks

and

concentration

Higher impact strength since contact with foreign objects is

sudden
38

Higher fatigue strength to counter vibration excitation

Ability to resist corrosion & scaling in fast flowing wet steam

Better damping against vibratory stresses

To meet above requirements, the conventional 12% Cr steels with

addition of Molybdenum and Vanadium are used to improve creep
strength & proof strength. Addition of Niobium increases 0.2% rupture
strength & creep properties for short term only.
Since blades are subjected to wet steam in last stages of the LP
turbine, the blades are alloyed with Titanium because of the following
reasons:
1. Ti has low density (60% of steels), so for same volume longer
length of blades can be used for comparable stresses in root.
2. Ti is corrosion and erosion resistant.
3. Yield strength is 50% better than 12% Cr steels.
4. Fatigue strength is much higher than 12% Cr steels.
In the low-pressure end blades, the careful considerations are made for
prevention of erosion & vibrations as well as better performance.

Enough distance between the stationary blade and

rotational blade is secured so that the moisture drips are formed
into fine mist.
Enough length of stellite strip is inserted into leading edge of
last rotating row.
There are narrow slits in the flow guide at the top of the last
rotating blades, through which the drip or moisture from the last
stationary blades are sucked to condenser.
The leading edge of the blades is surface hardened.
All the blades are carefully designed for vibratory strength.
Especially for the long blades, the perfect tuning of the
lowest natural frequencies is necessary.

39

There are several types of machine blade manufacturing.

CNC 3- Axis Machine
o TAL
o BFW
CNC 4-Axis Machine
o MAZAK NEXUS
CNC 5-Axis Machine
o LEICHTI Machine
o Makino machine
Twin Head Polishing Machines
o Sumitop wheel
o Buffing wheel
Belt Type Polishing Machines
Pencil Grinders

3-Axis Machines are having X, Y & Z axis, where straight

profile blades without shroud can be easily machined with simple
program.

40

4-axis machine has a C-axis through which root machining

can be done.

5-Axis Machines are having X, Y, Z, Rotary table & Head

tilting or Table tilting, where twisted profile blades with shroud and
negative profiles are required. The program should be made with
continuous 5 axis.

Blade Manufacturing Flowchart:

Bar/ Blank cutting &
Centre Drilling
Root Machining (4axis)

Stationary
blades

Blade Profile Roughing (5axis)

End cutting (3-axis)
Jig Groove and Weld Groove
Machining
Bend removal by hand pressure
machine
Total length maintaining (3
axis)
Finishing &
Polishing
41

Magnetic particle
inspection
Pin hole
Inspection
Preservati
Dispat

Stationary
blades

TURBINE ASSEMBLY

HIP ASSEMBLY FLOWCHART

HIP
Casing
Hydro

Rotor
Travel

HIP Outer
Casing
Levelling

Top
halves

Interference
check of inner
components with
respect to outer
components

Gland
Bore
setting

Clearance
Adjustme
nt

Rotor
Travel

installati

Inner
components
installation

LP ASSEMBLY FLOWCHART
Outer Casing
Lower Installation

Outer Casing
Upper
Installation

LP Bore
Adjustment

Steam Deflector
Installation

Steam
Chamber
Installation

Inner casing L/H

installation &
centering
Rotor Installation

Special Stationary
Blade Installation

Gland Ring
Installation
42

Rotor Travel

Installing upper
components &
measuring top
clearance

Bottom Clearance
Adjustment

GENERATORS
Generator is a machine which converts mechanical energy into
electrical energy. An a.c generator is a magnetic field system and an
armature assembly either of which may rotate relative to each other. The
field system will always be the rotating member and is called the Rotor
while the armature assembly, comprising armature winding and magnetic
iron core, will be stationary and is called Stator.
The basic principle of the electrical generator is based upon the
Faradays Law of Electromagnetic Induction, which states, When the
number of magnetic lines of force associated with a conductor changes, an
induced voltage is setup in the conductor. The voltage induced is
proportional to the rate of change of the magnetic lines associated with the
conductor.

The general frequency equation is,

f = (PxN) / 120 Hz
P= No. of poles of generator
N= Speed in RPM
For 50 Hz system,
2-pole machine => 3000 rpm
43

4-pole machine => 1500 rpm

The main parts of a generator are Stator, Rotor & Exciter, the details of
which are given below:

STATOR

Stator Frame
The stator frame and bearing brackets attached to both ends of the
stator frame are constructed from rolled steel plate, and are welded
into the required shapes. To ensure that the frame has required
strength to be used as a pressure vessel, all parts of it are designed
with a sufficient strength to enable it to withstand the higher of either
twice the maximum operating gas pressure. Severe Hydrostatic Testing
is used to ensure this strength.

Stator Core
It consists of electrical steel sheets laminated within the frame. Coldrolled silicon steel strips are used as the electrical steel sheet material.
These are punched out in sector shape and coated on both sides with
an insulating varnish which is baked on. This is done to prevent losses
caused by eddy currents in the core laminations.

44

 Flexible Mounting
The magnetic force which develops between the rotor poles and the
stator core induces a double-frequency vibration in the stator core.
In two pole machines, since this vibration is of a high level, to prevent
it from being transmitted to the frame and foundation, the stator core
is supported from the frame by a flexible mounting. It is necessary for
the flexible mounting to have not only radial mobility but also to have
a circumferential rigidity large enough to support the weight of the
core and to withstand the short-circuit torque. To satisfy these
requirements, the flexible mounting is constructed with a number of
leaf springs, with one end bolted to the bore ring and the other bolted
to the outer frame.

45

 Stator Winding
The stator coils are constructed as double-layer half coils and, after
insertion in slots in Stator core, are end connected to form a complete
winding.
The conductors of each coil consist of a glass sheathed rectangular
copper bars. A combination of hollow and solid strands consisting of
four or six rows is used to achieve high cooling and low eddy current
loss in the stator coil. Solid and hollow strands and a header are
brazed at both ends of the stator coils where a water chamber is
formed, and the coils are electrically connected by means of a series
connector.
The cooling water flows in and out of the stator coils through Teflon
hoses with superior insulating capabilities. Dialastic Epoxy is used as
the insulation for the stator coils. After several continuous windings of
mica tape, surface protecting tape is wound on the coils. After this
tape winding is completed, coils are placed in vacuum to remove
moisture, solvents and bubbles, and they are pressure impregnated in
low viscosity thermosetting resin. This results in the impregnating resin
seeping into every part of the coil. After impregnation, the coils are
pressed and heated to afect polymerizing curing, and thus an overall
unified insulation is provided.

ROTOR
The design and construction of rotor is difficult as its weight is considerably
high and rotates at fairly high speed (3000 or 3600rpm). In order to
accommodate the field windings to carry field current, a large number of
deep slots are machined in the rotor. The length between the two bearings
is limited to eight times the diameter of the rotor. The approximate weight
of the rotor of 120MW is about 30-40tons.
46

In order to achieve the efficient cooling of rotor it is necessary to allow

ample passage in the rotor, through which cooling fluid can be circulated
freely.
The rotor shaft is a solid Ni-Mo-V or Ni-Cr-Mo-V steel forging. The rotor of a
turbine generator rotates at high speed, making its mechanical structure of
extreme importance. Special care is thus required with regard to materials,
mechanical design and machining.

The rotor conductors for water-cooled generators use cold drawn silver
bearing copper. Two U channels are combined to form one turn, and the
rectangular space enclosed forms the path of the hydrogen gas for cooling
the conductor. Radial ventilating ducts provided at the end part of the coil
and the center of the straight section of the coil serve as coolant inlets and
outlets.

47

Generator
Assembly:

Rotor
Forging

Transport

End Plating

Lath
e

ROTOR
Rotor
Assembly

Groove &
Pilot Hole
Machining

Rotor
Winding

HSBT

Final Lathe
Machining

Final
Assembly

48

Paintin
g

Slot
Machining

STATOR

Stator
Winding

Stator Frame
Fabrication

Core Loop
Test

Frame
Machining

Core

Assembl
y

Hydro
Test

GENERATOR TESTING:

Generator is tested for checking the Voltage, Amperage and Power factor as
demanded by the customer.
The Rotor is tested dynamically at the HSBT facility.
The various tests for the Stator are:
i.

Open Circuit test

ii.

Short Circuit test

iii.

Portier-Reaction test
49

iv.

Partial Discharge test

v.

Insulation Resistance test

vi.

High Voltage test

vii.

Leakage test

viii.

Rotor Run-out test

ix.

Short Circuit Ratio Test

x.

Elcid Test

xi.

Bump Test

HIGH SPEED BALANCING FACILITY

HSBT facility is used for balancing the rotor in accordance to its weight
just to check that rotor geometrical axis and rotational axis are the
same or not.
50

 If the geometrical axis and rotational axis are not same then rotor
would rotate eccentrically disturbing other couplings and rotor and can
cause accident if not balanced at right time.
In this facility, rotor is rotated at about 3000 rpm in airproof (vacuum)
environment to avoid air friction as this can cause massive accident.
This facility is brought here with the help of GERMAN company.

Procedure for Balancing:51

1. Initially, centering of rotor is done after inserting it into the

vacuum chamber by means of dial gauges (4 dial gauges at 4
segments of rotor).
2. After this centering, rotor is rotated by about 30. If there is any
misalignment then pedestal is rotated for proper centering of
rotor.
3. After this, rotor is rotated at about 600rpm for operating the
jacking oil system.
4. Softwares for checking alignment are CAB920 for slow speeds
and CABFLEX for high speeds.
5. If any unbalancing is found in rotor then weight plugs can be
added or removed to balance it.

52