PROJECT

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

SUBMITTED BY:-

Anurag maheshwari
Dayalbagh educational institute
Agra

Preface

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 Acknowledgement
First of all, I am highly grateful to my institute for giving me this wonderful
opportunity to accomplish my training in this world-class company.

Since the list is endless, yet I would like to thank some key people who certainly
made my training successful.
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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 Manager-Production 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

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 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
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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
country’s plan for a mega ramp up in power generation capacity using super-critical
technology.

L&T POWER VISION 2015

L&T Power shall be India’s most preferred provider of equipment services and turnkey
solution for fossil fuel-based power plants and a leading contributing to the nation’s
power generation capacity.

L&T POWER MISSION

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 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:

Main steam pressure is 24.2 MPa and temperature is between 538° C to 600
°C. While re-heater temperature is between 566°C to 600°C.

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.

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 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

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.

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The blades are designed in such a way, that the steam will glide on and off 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
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 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.

Supercritical Turbine:
L&T MHI Turbine – LMTG

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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.

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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, 565ºC main steam
temperature and 593ºC reheat steam temperature.

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%.
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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

Thermal Cycle Efficiency

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

ηpower plant = η boiler x η TG cycle x η turbine x η generator

Typical values of these efficiencies for a modern thermal power plant employing reheat
and regenerative feed water heating are as follows:
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ηboiler = 85 to 88%

ηturbine = 60 to70%

ηgenerator = 98 to 98.6%

ηTG cycle = 44 to 48% (subcritical steam condition)

= 48 to 53% (supercritical steam condition)

ηpowerplant = 37.5 to 43%

• ηBoiler , ηTurbine , ηGenerator are fairly high and have almost peaked, only incremental
improvements is taking place.

• ηTG Cycle is lower because it is governed by thermodynamic laws and depend on MS

and RHS Temperature and Condenser Vacuum

MAIN COMPONENTS OF A STEAM TURBINE

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

 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.

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 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.

 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 off the supply of steam turbine under such situation.
They have only two positions either fully open or fully closed.
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 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

 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.
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  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 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 )
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 RABIGH (2 x 120 MW )

Upcoming project:-
 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:-

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 1. LP outer casing
2. LP inner casing
3. HP pedestal
4. Generator Frame
5. Main oil tank
6. Blades
7. Rotor ( only groove machining for holding blades)

Components of Assembly:-
1. HIP
2. LP1 & LP2
3. Valve assembly
4. Generator
5. Rotor
6. Blades
7. Pedestal

Steam flow in Turbine

BOILER
BOILER
MSV/GV
FEED
WATER VALVE

CONDENSER HP TURBINE

LP
REHEATER
TURBINE 19

Crossover RSV/ICV
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 stiff 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
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it by pipes in radial orientation. At LP cylinder exhaust the connection to condenser
however normally is rectangular. The 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 into-

1. 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 rotor’s critical speed, rotor can be classified into-

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

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 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 different heights so as to form a catenary
shape. These bearing heights at different 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.
 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 30-35C. 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.

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 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, differential expansion, electricity, vibration pick-up, etc.
 It covers the rotor coupling.
 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.

STOP VALVES

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Its purpose is to cut-off 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 below shows the general work system being
carried out at the fabrication department.

INPUTS PROCESSES OUTPUTS

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  Raw materials like  Cutting processes like  LP inner & outer
steel plates, steel CNC cutting, Manual casings
sections, and pipes. cutting, Oxyfuel  HP Pedestal
cutting & plasma  Thermal Shield
 Semi-finished parts cutting.  Main Oil Tank
like castings, rough  Plate bending, Plate  Top Seal Rings
machined rolling & Pipe  SSB, Bladed
components, HIP bending. diaphragm, HP Nozzle
outer casings  Weld Edge ring
preparations  HIP outer casing with
 Finished parts like  Fit up process welded steam inlet
SSB Diaphragm  Welding process sleeves
blades, Rateau blades  Heat treatment  Generator stator
 Shot Blasting frame
 Painting

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 oxy-acetylene mixture and then cutting using a high-pressure oxygen
jet.

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 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.

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

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 The cycle consists of heating the job at the rate of 80C and then further
heating the job at the rate of 55C till it reaches a temperature of around 625C.
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 Inspection Layout Inspection Production

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:

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  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

 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

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 X axis (Column) 15m
Y axis 4.5m
Z axis (Ram) 1.2m
W 1000mm
Power 91KW
Max speed 2500rpm

 VTL 101/ST5

Make – HNK, Korea

Max Dia. Of Table 6m
VC of table 0-40rpm
Swing dia 9.5m
Ht. of job 4.5m
Power 171KW
Spindle VC 1000rpm
Wt. of job 80MT

 VTL 201/ ST9

Make – HNK, Korea

Dia 3m
Spindle speed 80rpm
X -200/ +2225mm
Y (ram) 1800mm
W (cross rail) 2m
Wt of job 30T
Ht of job 3m
29
 Power 60/75KW
Swing dia 4m

 PM 202/ ST 13

Make – MHI, Japan

X 9m
Y 4.9m
Z 1m
W 2.2m
Ht of job 3.05m
Max speed 4000rpm
Distance b/w columns 4.3m
Power 45KW

 PM 201/ Gen 6

Make – MHI, Japan

X 5m

Y 4.2m

Z 1m
W 2.2m

Max speed 4000rpm

Ht of job 3.05m

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 Distance b/w columns 3.8m

Power 45KW

 HBM 202/ UDM2

X 5m
Y 2.1m
Z 1.3m
W 1.4m
Z+W 1.4m
Speed 400rpm
Power 30KW

 HBM 201/ UDM 1

X 4.6m
Y 3.5m
Z 0.9m
Max speed 100
Power 33KW

 VTL 301/ Gen 7

X 1000/1700mm
Z 1200mm
W 1000mm
Speed 120rpm
Table dia 2.5m
Power 33KW
Swing dia 3m
Wt 15T
Ht 2m

 FHB/HBM 203/UDM 5
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 X 6.4m
Y 2.67m
Z 1.1m
Speed 210rpm
Power 26KW

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

X 15m
Y 4.5m
Z 1.2m
W 1m
Speed 210rpm
Power 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:

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
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 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 different 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.

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

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 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 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.

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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
 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.

35
 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.

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
36
  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.
 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 (4-axis) Stationary
blades

Blade Profile Roughing (5-axis)

End cutting (3-axis)

Jig Groove and Weld Groove

37 Machining

Bend removal by hand pressure machine

 TURBINE ASSEMBLY

HIP ASSEMBLY FLOWCHART

Interference check of
HIP Casing HIP Outer Gland inner components
Hydro Test Casing Levelling Bore with respect to outer
components

Rotor Top halves Rotor Clearance Inner components

Travel installation Travel Adjustment installation

LP ASSEMBLY FLOWCHART

Outer Casing Lower Outer Casing LP Bore Adjustment

Installation Upper Installation

Steam Deflector Steam Chamber Inner casing L/H

Installation Installation installation &
centering

Special Stationary Gland Ring Rotor Installation

Blade Installation Installation

Installing upper Rotor Travel Bottom Clearance

components &
Adjustment
measuring top
clearance

38
 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 Faraday’s 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

4-pole machine => 1500 rpm

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

39
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. Cold-rolled 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.

40
 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.

 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 affect polymerizing curing, and thus
an overall unified insulation is provided.

41
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.

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.

42
 Generator
Assembly:

Rotor Forging Transport End Plating

Lathe

ROTOR

Rotor
Rotor Groove & Pilot Slot
Assembly
Winding Hole Machining Machining

Final Lathe HSBT

Machining

Final Assembly

STATOR

43
 Core
Stator Winding Core Loop Test
Assembly

Stator Frame Frame Hydro Test

Fabrication Machining

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
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

44
 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.
 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.

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Procedure for Balancing:-
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.

46