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A
Summer Training Report
on
Steam Turbine Manufacturing
at
“Bharat Heavy Electricals Limited(Bhopal)”
Submitted in partial fulfilment of the requirements for the
degree of
Bachelor of Technology in Mechanical Engineering
Submitted By
Abhishek
DEPARTMENT OF MECHANICAL ENGINEERING
NOIDA INSTITUTE OF ENGINEERING AND
TECHNOLOGY
Greater Noida, Uttar Pradesh
APJ Abdul Kalam Technical University
December 2017
i
ACKNOWLEDGENT
I would like to express my gratitude for the people who were part of my training report,
directly or indirectly people who gave unending support to complete my training and
report.
I would like thanks Dr. …………….. (HOD, M.E.) for providing this opportunity. A
special gratitude to my guide Mr. ………….. (Deputy Manager-STM) and whose
contribution in guidance, stimulating suggestions and encouragement, helped me to
complete my vocational training in the BHEL, Bhopal.
I would like to thanks to all those people who directly or indirectly helped and guided
us to complete my training and this project including the following instructor, technical
staff and supervisor of various section.
Abhishek
Roll No.
4th year/7th sem
ii
ABBREVIATIONS
BHEL Bharat Heavy Electricals limited
IP Intermidiate Pressure
LP Low Pressure
HP High Pressure
STM Steam Turbine Manufacturing
MSV Main Stop Valve
ESV Emergency Stop Valve
CV Control Valve
GOVT Government
PSU Public Sector Under Taking
FY Financial Year
MW Mega Watt
GW Giga Watt
AC Alternating Current
ASME Americam Society Of Mechanical Engineers
ISO International Organisation For Standardization
KG Kilogram
CM Centimeter
TQM Total Quality Management
iii
ABSTRACT
In the era of Mechanical Engineering, Turbine, A Prime Mover ( Which uses the Raw
Energy of a substance and converts it to Mechanical Energy) is a well known machine
most useful in the field of Power Generation. This Mechanical energy is used in running
an Electric Generator which is directly coupled to the shaft of turbine. From this
Electric Generator, we get electric Power which can be transmitted over long distances
by means of transmission lines and transmission towers.
In my Industrial Training in B.H.E.L., Bhopal I go through all sections in Turbine
Manufacturing. First management team told me about the history of industry, Area,
Capacity, Machines installed & Facilities in the Industry. After that they told about the
Steam Turbine its types , parts like Blades, Casing, Rotor etc. Then they told full
explanation of constructional features and procedure along with equipment used.
Before telling about the machines used in Manufacturing of Blade, they told about the
safety precautions, Step by Step arrangement of machines in the block with a well
defined proper format. They also told the material of blade for a particular desire, types
of Blades, Operations performed on Blades.
During my training I was guided to manufacturing processes of different parts of steam
turbine, heat exchangers and condensers. Turbine are categorised into three parts i.e.
high pressure turbine, intermediate pressure turbine and low pressure turbine.
Turbines are manufactured by lining up the various process like forging, casting,
machining etc. which is followed by manufacturing. All these process are done in flow
manner in order raise the work efficiency and minimise the efforts and time.
iv
TABLE OF CONTENTS
Contents Page No.
Acknowledgement…………………………………………………….. i
Abbreviations………………………………………………………….. ii
Abstract…………………………………………………………………. iii
Table of Contents………………………………………………………. iv
List of Figures…………………………………………………………... vi
List of Tables…………………………………………………………… vii
Chapter 1
1.1 BHEL – An Overview .............................................................................................1
1.2 Its Operation............................................................................................................1
1.3 Manufacturing Unit In India ....................................................................................2
1.4 Products Of BHEL…………………………………………………………………3
Chapter 2
2.1 BHEL-Bhopal ..........................................................................................................5
2.2 Awards And Recognition.........................................................................................5
2.3 Products Of BHEL Bhopal……………………………………………………….. 6
2.4 Details of Sets Supplied…………………………………………………………....7
Chapter 3
3.1 Steam Turbine……………………………………………………………………. 8
3.1.1 HP Turbine........................................................................................................9
3.1.2 IP Turbine..........................................................................................................9
3.1.3 LP Turbine.......................................................................................................10
3.2 Specifications of Steam Turbine…………………………………............…….....11
Chapter 4
4.1 Steam Turbine Components……………………...………………………………12
4.1.2 Shell.................................................................................................................13
4.1.3 Rotor................................................................................................................13
4.1.4 Governor Pedestal ...........................................................................................13
v
4.1.5 Steam Turbine Rotor.......................................................................................13
4.1.6 Turbine Casing................................................................................................13
4.1.7 Turbine Flanges……………………………………………………………...14
4.2 Steam Turbine Blades............................................................................................15
4.2.1 Fixed Blade .....................................................................................................16
4.2.2 Moving Blade………....……………………………………………………..16
4.3 Impulse Turbines ...................................................................................................17
4.4 Reaction Turbines ..................................................................................................18
4.5 Blading Stages: ......................................................................................................19
Chapter 5
5.1 Valves ....................................................................................................................20
5.1.1 Main Stop Valves............................................................................................20
5.1.2 Control Valves.................................................................................................20
5.2 Turbine Governing System....................................................................................21
5.2.1 Mechanical Governor......................................................................................21
5.3 Principle Of Operation And Design.......................................................................22
Chapter 6
6.1 Turbine Efficiency .................................................................................................23
6.1.1 Impulse Turbine Efficiency.............................................................................23
6.1.2 Reaction Turbine.............................................................................................25
7.1 Operation And Maintenance..................................................................................28
7.2 Speed Regulation ...................................................................................................29
8. Conclusion…………………………………………………………………………30
References…………………………………………………………………………...31
vi
LIST OF FIGURES
Fig No. Title Page No.
Fig 1.1 BHEL Logo…………………………………….. 1
Fig 2.1 BHEL Bhopal…………………………………… 5
Fig 2.2 Products of BHEL Bhopal……………………….. 6
Fig 3.1 Steam Flow Diagram……………………………… 8
Fig 3.2 HP Turbine Rotor…………………………………. 9
Fig 3.3 Intermediate Pressure Turbine…………………….. 10
Fig 3.4 LP Turbine Rotor…………………………………. 10
Fig 4.1 Steam Turbine Foundation or Frame………………. 12
Fig 4.2 Turbine Upper Casing……………………………… 13
Fig 4.3 Turbine Lower Casing……………………………… 14
Fig 4.4 Turbine Flanges……………………………………. 15
Fig 4.5 Turbine Blades…………………………………….. 15
Fig 4.6 Fixed Blades………………………………………. 16
Fig 4.7 Moving Blades…………………………………….. 16
Fig 4.8 Combination of Blades……………………………. 17
Fig 4.9 Comparison Between Impulse and Reaction Turbine 18
Fig 4.10 Multi stage blading………………………………… 19
Fig 5.1 Mechanical Governor…………………………….. 21
Fig 6.1 Velocity Triangle………………………………….. 23
Fig 6.2 Convergent Divergent Nozzel……………………… 25
Fig 6.3 Graph Depicting Efficiency of Impulse Turbine…... 25
Fig 6.4 Velocity Diagram………………………………….. 26
Fig 6.5 Comparing Efficiencies of Impulse and Reaction
turbines………………………………………….
27
Fig 7.1 A Modern Steam Turbine Generator Installation… 28
Fig 7.2 Diagram Of A Steam Turbine Generator System… 29
vii
LIST OF TABLES
Table No. Title Page No.
Table 2.1 Table 2.1 Details of Turbine Sets Supplied 7
Table 3.1 Table 3.1 Specification of 236 MW Steam Turbine 11
1
CHAPTER-1
1.1 BHEL – AN OVERVIEW
Bharat Heavy Electrical Limited (BHEL) owned by the Government of India, is a
power plant equipment manufacturer and operates as engineering and manufacturing
company based in New Delhi, India. Established in 1964, BHEL is India’s largest
engineering and manufacturing company of its kind. The company has been earning
profit continuously since 1971-72 and paying dividends uninterruptedly since 1976-77.
It has been granted the prestigious Maharatna (big gem) status in 2013 by Govt of
India for its outstanding performance. The elite list of Maharatna contains another 6
behemoth PSU companies of India.
BHEL was established in 1964 Heavy Electricals (India) Limited was merged with
BHEL in 1974. In 1982, it entered into power equipment, to reduce its dependence on
the power sector. It developed the capability to produce a variety of electrical, electronic
and mechanical equipments for all sectors, including transmission, transportation, oil
and gas and other allied industries. In 1991, it was converted into a public limited
company. By the end of 1996, the company had handed over 100 Electric Locomotives
to Indian Railway and installed 250 Hydro-sets across India.
1.2 ITS OPERATION :-
BHEL is engaged in the design, engineering, manufacturing, construction, testing,
commissioning and servicing of a wide range of products, systems and services for the
core sectors of the economy, viz. power, transmission, industry, transportation,
renewable energy, oil & gas and defence.
Fig 1.1 BHEL Logo
2
It has a network of 17 manufacturing units, 2 repair units, 4 regional offices, 8 service
centres, 8 overseas offices, 15 regional centres, 7 joint ventures, and infrastructure
allowing it to execute more than 150 projects at sites across India and abroad. The
company has established the capability to deliver 20,000 MW p.a. of power equipment
to address the growing demand for power generation equipment.
BHEL has retained its market leadership position during 2015-16 with 74% market
share in the Power Sector. An improved focus on project execution enabled BHEL
record its highest ever commissioning/synchronization of 15059 MW of power plants
in domestic and international markets in 2015-16, marking a 59% increase over 2014-
15. With the all-time high commissioning of 15000 MW in a single year FY2015-16,
BHEL has exceeded 170 GW installed base of power generating equipments.
It also has been exporting its power and industry segment products and services for
over 40 years. BHEL's global references are spread across over 76 countries across all
the six continents of the world. The cumulative overseas installed capacity of BHEL
manufactured power plants exceeds 9,000 MW across 21 countries
including Malaysia, Oman, Iraq, UAE, Bhutan, Egypt and New Zealand. Their
physical exports range from turnkey projects to after sales services.
1.3 MANUFACTURING UNIT IN INDIA
 Centralised Stamping Unit & Fabrication Plant (CSU & FP), Jagdishpur
 Insulator Plant (IP), Jagdishpur
 Electronics Division (EDN), Bangalore
 Industrial Systems Group (ISG), Bangalore
 Electro-Porcelains Division (EPD), Bangalore
 Heavy Electrical Plant (HEP), Bhopal
 Industrial Valves Plant (IVP), Goindwal
 Heavy Electrical Equipment Plant (HEEP), Ranipur (Haridwar)
 Central Foundry Forge Plant (CFFP), Ranipur (Haridwar)
 Heavy Power Equipment Plant (HPEP), Hyderabad
 Transformer Plant (TP), Jhansi
 Boiler Auxiliaries Plant (BAP), Ranipet
 Component Fabrication Plant (CFP), Rudrapur
3
 High Pressure Boiler Plant (HPBP), Tiruchirappalli
 Seamless Steel Tube Plant (SSTP), Tiruchirappalli
 Power Plant Piping Unit (PPPU), Thirumayam
 Heavy Plates & Vessels Plant (HPVP), Visakhapatnam
1.4 PRODUCTS OF BHEL
1. Thermal power Plants
2. Nuclear power Plants
3. Gas based power Plants
4. Hydro power Plants
5. DG power Plants
6. Boilers (steam generator)
7. Boiler Auxiliaries
8. Gas generator
9. Hydro generator
10. Steam turbine
11. Gas turbine
12. Hydro turbine
13. Transformer
14. Switchgear
15. Oil field equipment
16. Boiler drum
17. Piping System
18. Soot Blowers
19. Valves
20. Seamless Steel Tubes
21. Condenser s and Heat exchangers
22. Pumps
23. Desalination and Water treatment plants
24. Automation and Control systems
25. Power electronics
4
26. Transmission system control
27. Semiconductor devices
28. Solar photo voltaic
29. Software system solutions
30. Bus ducts
31. Insulators
32. Control panels
33. Capacitors
34. Bushings
35. Electrical machines
36. DC, AC heavy duty Motors
37. Compressors
38. Control gears
39. Traction motors
40. Research and development products
5
CHAPTER-2
2.1 BHEL-BHOPAL
Vision:
A Global Engineering Enterprise providing Solutions for better tomorrow
Mission:
Providing sustainable business solutions in the fields of Energy, Industry &
Infrastructure
Values:
Governance, Respect, Excellence, Loyalty, Integrity, Commitment, Innovation, Team
Work
BHEL, Bhopal certified to ISO: 9001, ISO 14001 and OHSAS 18001, is moving
towards superiority by acquiring TQM as per EFQM/CII model of Business Excellence.
Heat Exchanger Division is accredited with ASME “U” Stamp. With the slogan of
“Kadam Kadam milana hai, grahak safal banana hai”, it is committed to the customers.
BHEL Bhopal has its own Laboratories for material testing and instrument calibration
which are accredited with ISO 17025 by NABL. The hydro Laboratory and Centre for
Electric Transportation are the only laboratories of it are in this part of world.
Fig 2.1 BHEL Bhopal
2.2 AWARDS AND RECOGNITION
National e-Governance Award: Bharat Heavy Electricals Limited (BHEL), has been
conferred upon the prestigious National e-Governance Gold Award of Government of
India for 2012-13, in the category – “Innovative use of ICT by PSUs for Customer
6
Benefits”, for the project “Integrated system for Online Generation of Electrical
Specifications for Transformers” , developed by Informatics Centre (IFX) department,
BHEL, Bhopal.
CSI National Award (2013) : BHEL Bhopal has won the prestigious CSI National
Award for Excellence in IT 2013 in the category of Business Collaboration solutions:
Banking & Finance.
Award for Excellence in e-Governance initiatives in MP: IT department of BHEL,
Bhopal has been declared as Winner for Excellence Award in e-Governance initiatives
in Madhya Pradesh for 2012-13, in the category – “The best application following best-
practices of software development”, for the project “Online Recruitment system”,
developed by Informatics Centre (IFX) department, BHEL, Bhopal.
National e-Governance Gold Award 2014-15: Bharat Heavy Electricals Limited
(BHEL) Bhopal has been conferred with the prestigious National e-Governance Gold
award by Government of India during the 18th National Conference on e-Governance
held at Gandhinagar, Gujarat. The award was given for the ‘SAMPARK’ project,
developed by Information Services and Technology department (ITS), BHEL Bhopal.
2.3 PRODUCTS OF BHEL BHOPAL
Power Utilisation
AC Motors & Alternators
Transportation
Transportation Equipment
Power Generation
Hydro Turbines
Hydro Generators
Heat Exchangers
Excitation Control Equipment
Steam Turbines
Miscellaneous
Oil Rigs Fabrication
Power Transmission
Transformer Switchgear
On-Load Tap Changer
Large Current Rectifiers
Control & Relay Panels
Renovation & Maintenance
Thermal Power Stations
Fig 2.2 Products of BHEL Bhopal
7
2.4 DETAILS OF SETS SUPPLIED
Table 2.1 Details of Turbine Sets Supplied
Rating
(MW)
Type No. of Sets Supplied First Set
Commissioned
30 Single cylinder / impulse 6 1969
120 Three cylinder / impulse /
reheat
18 1974
210 Three cylinder / reaction /
reheat
11 1988
236 Two cylinder / impulse /
reheat
10 1983
15000
SHP
Marine Turbine / impulse /
non reheat
20 1974
Industrial
Turbine
Condensing / Back pressure 4 1998
8
CHAPTER-3
3.1 STEAM TURBINE
A steam turbine is a device that extracts thermal energy from pressurized steam and
uses it to do mechanical work on a rotating output shaft. Its modern manifestation was
invented by Sir Charles Parsons in 1884.
Because the turbine generates rotary motion, it is particularly suited to be used to drive
an electrical generator – about 90% of all electricity generation in the United States
(1996) is by use of steam turbines. The steam turbine is a form of heat engine that
derives much of its improvement in thermodynamic efficiency from the use of multiple
stages in the expansion of the steam, which results in a closer approach to the ideal
reversible expansion process.
Steam turbines are used for the generation of electricity in thermal power plants, such
as plants using coal, fuel oil or nuclear fuel. They were once used to directly drive
mechanical devices such as ships' propellers (for example the Turbinia, the first
turbine-powered steam launch) but most such applications now use reduction gears or
an intermediate electrical step, where the turbine is used to generate electricity, which
then powers an electric motor connected to the mechanical load. Turbo electric ship
machinery was particularly popular in the period immediately before and during World
War II, primarily due to a lack of sufficient gear-cutting facilities in US and UK
shipyards.
Fig 3.1 Steam Flow Diagram
9
There are three sections to a steam turbine viz. high pressure, intermediate pressure and
low pressure turbine. All three are mounted on the same shaft which rotates at about
3600 rpm in a generator to make electricity.
 HP Turbine
 IP Turbine
 LP Turbine
3.1.1 HP Turbine
• Single flow
• Double shell casing
1. Inner casing vertically split
2. Outer casing barrel type & axially divided
3. Single exhaust in L/H
• Mono block rotor
• Casing mounted valves
• Internal bypass cooling
• Transported as single unit
Fig 3.2 HP Turbine Rotor
3.1.2 IP Turbine
• Double flow
• Double casing design with horizontal split
• Inlet from Lower half
10
• Single Exhaust from upper half
• Extraction connections from lower half
• Admission blade ring
Fig 3.3 Intermediate Pressure Turbine
3.1.3 LP Turbine
• Double flow
• Double shell casing
• Single admission from top half
• Outer Casing & condenser rigidly connected
• Push rod arrangement to minimize axial clearances
• Mono block rotor
• Inner / Outer casing fabricated
Fig 3.4 LP Turbine Rotor
11
3.2 SPECIFICATIONS OF STEAM TURBINE
Table 3.1 Specification of 236 MW Steam Turbine
S.No Description Parameter
1 Rated capacity 236 mw
2 Pressure at stop valve 40 kg/cm2
3 Temperature at stop valve 250 c
4 Max. Steam flow at s.v 1332.2 tonnes /hr
5 Reheat/non reheat Reheat
6 Type of governing Throttle control
7 Turbine speed 3000 rpm
8 Exhaust pressure 63.5 mm hg abs
9 Number of cylinders H.P-1,double flow LP-1
10 Number of stages HP-5, LP-5 + 5
11 Height of last stage blade 945 mm
12 Last stage mean dia 2641 mm
13 Special feature Steam at stop valve is wet - bled steam
and live steam reheating
14 Weight of turbine 450 tonnes
15 Length of turbine 15 meters
16 Type of turbine Impulse
17 Collaborator GEC U.K
12
CHAPTER-4
4.1 STEAM TURBINE COMPONENTS
 Steam turbine foundation or frame
 Rotor
 Governor Pedestal
 Turbine Casing
1. Upper Casing
2. Lower Casing
 Turbine Casing Flanges
 Steam Turbine Blades
1. Fixed Blades or Diaphragm
2. Moving Blades
 Valves
1. Main Stop Valve
2. Control Valve
 Turbine Governing System
Fig 4.1 Steam Turbine Foundation or Frame
13
4.1.1 FRAME (BASE) - supports the stator, rotor and governor pedestal.
4.1.2 SHELL – Consists cylinder, casing, nozzle, steam chest & bearing.
4.1.3 ROTOR – consists of low, intermediate, high pressure stage blades and possible
stub shaft(s) for governor pedestal components, thrust bearing, journal bearings, turning
gear & main lube oil system.
4.1.4 GOVERNOR PEDESTAL – consists of the EHC oil system, turbine speed
governor, and protective devices.
4.1.5 STEAM TURBINE ROTOR – Multistage steam turbines are manufactured with
solid forged rotor construction. Rotors are precisely machined from solid alloy steel
forging. An integrally forged rotor provides increased reliability particularly for high
speed applications.
The complete rotor assembly is dynamically balanced at operating speed and over speed
tested in a vacuum bunker to ensure safety in operation. High speed balancing can also
reduce residual stresses and the effects of blade seating.
4.1.6 TURBINE CASING – The casing of turbine cylinders are of simple construction
to minimize any distortion due to temperature changes. They are constructed in two
halves (top and bottom) along a horizontal joint so that the cylinder is easily opened for
inspection and maintenance. With the top cylinder casing removed the rotor can also
be easily withdrawn without interfering with the alignment of the bearings.
Fig 4.2 Turbine Upper Casing
14
Most turbines constructed today either have a double or partial double casing on the
high pressure (HP) or intermediate pressure (IP) cylinders. This arrangement subjects
the outer casing joint flanges, bolts and outer casing glands to lower steam condition.
This also makes it possible for reverse flow within the cylinder and greatly reduces
fabrication thickness as pressure within the cylinder is distributed across two casings
instead of one. This reduced the wall thickness also enables the cylinder to respond
more rapidly to changes in steam temperature due to the thermal mass.
Fig 4.3 Turbine Lower Casing
The high pressure end of the turbine is supported by the steam end bearing housing
which is flexibly mounted to allow for axial expansion caused by temperature changes.
The exhaust casing is centreline supported on pedestals that maintain perfect unit
alignment while permitting lateral expansion. Covers on both the steam end and exhaust
end bearing housings and seal housings may be lifted independently of the main casing
to provide ready access to such items as the bearings, control components and seals.
4.1.7 TURBINE CASING FLANGES- One method of joining the top and bottom
halves of the cylinder casing is by using flanges with machined holes. Bolts or studs
are insertion into these machined holes to hold the top and bottom halves together. To
15
prevent leakage from the joint between the top flange and the bottom flange the are
accurately machined.
Fig 4.4 Turbine Flanges
Another method of joining top and bottom cylinder flanges is by clamps bolted radially
around the outer of cylinder. The outer faces of flanges are made of wedge shaped so
that the tighter the clamps are pulled the greater the pressure on the joint faces.
4.2 STEAM TURBINE BLADES
The energy conversion takes place through the turbine blades. A turbine consists of
alternate rows of blades. This blades convert the chemical or thermal energy of working
fluid into kinetic energy and then from kinetic energy to mechanical energy as rotation
of the shaft.
Fig 4.5 Turbine Blades
16
There are two types of blade, fixed and moving blade. Moving blade is also two types.
One is impulse blade and another reaction blade.
4.2.1 FIXED BLADE- A fixed blade assembly is very important for turbine blading.
It is also known as diaphragm. The shape of the blade is the key to the energy
conversion process. Since the fixed blades have a conversing nozzle shape, it is also
called nozzles. When steam is passed over the fixed blades, they increase the velocity
of steam as an operation of nozzles. Here blades are converted the thermal energy of
steam into kinetic energy by causing the steam to speed up and gain velocity.
Fig 4.6 Fixed Blades
4.2.2 MOVING BLADE- Moving blade can be shaped in either of two ways: reaction
shaped or impulse shaped. The shape of the blade determines how the energy is actually
converted. Either type of moving blades or a combination of both can be attached to the
shaft of the rotor on dices, called wheels as shown in the figure 4.7.
Fig 4.7 Moving Blades
17
Along the outer rim of the blades is a metal band, called shrouding which ties the blades
together. The moving blades convert the kinetic energy in the moving speed into the
mechanical energy as rotor rotation.
Fig 4.8 Combination of Blades
4.3 IMPULSE TURBINES
These turbines change the direction of flow of a high velocity fluid or gas jet. The
resulting impulse spins the turbine and leaves the fluid flow with diminished kinetic
energy. There is no pressure change of the fluid or gas in the turbine rotor blades as in
the case of a steam or gas turbine, all the pressure drop takes place in the stationary
blades.
Before reaching the turbine, the fluid's pressure head is changed to velocity head by
accelerating the fluid with a nozzle. Impulse turbines do not require a pressure casement
around the rotor since the fluid jet is created by the nozzle prior to reaching the blading
on the rotor. Newton's second law describes the transfer of energy for impulse turbines.
18
4.4 REACTION TURBINES
These turbines develop torque by reacting to the gas or fluid's pressure or mass. The
pressure of the gas or fluid changes as it passes through the turbine rotor blades. A
pressure casement is needed to contain the working fluid as it acts on the turbine stages
or the turbine must be fully immersed in the fluid flow. The casing contains and directs
the working fluid and, for water turbines, maintains the suction imparted by the draft
tube. Francis turbines and most steam turbines use this concept. For compressible
working fluids, multiple turbine stages are usually used to harness the expanding gas
efficiently. Newton's third law describes the transfer of energy for reaction turbines.
Fig 4.9 Comparison Between Impulse and Reaction Turbine
4.5 BLADING STAGES:
Two successive fixed and moving blades are collectively known as blading stage. The
effects of pressure and velocity of working fluids depend upon the stage conditions. In
Ashuganj power station, the turbines which are used have 23 stages at HP turbine and
21 stages at IP & LP turbine. Now the effects of pressure and velocity on various
blading stages are described in below:
19
For impulse blading velocity increases and pressure decreases across each row as the
steam passes through the fixed blading. Again when steam passes through the impulse
type moving blade, its velocity decreases, but its pressure remains constant as shown in
the figure.
For reaction blading velocity increases and the pressure decreases across each row as
the steam passes through the fixed blading. When steam passes through the reaction
type moving blade, its pressure and velocity both decreases as shown.
Fig 4.10 Multi stage blading
20
CHAPTER-5
5.1 VALVES
Steam from the boiler is routed to the turbine through a steam line that contains the
main stop valves and the control valves.
5.1.1 MAIN STOP VALVES- It is such a valve through which steam passes to
the turbine blades. By controlling this valve steam flow can be controlled. Each main
stop valve consists of a valve disk, a valve stem and a hydraulic actuator.
The hydraulic actuator contains a piston and a compression spring. Since the valve disk
and stems are connected to the piston, movement of the piston causes movement of the
valve disc. During normal turbine operation, hydraulic oil is directed into or out of the
hydraulic actuator. Directing oil into the actuator opens the valve and compresses the
spring.
As long as the amount of oil in actuator is held constant, the valve will remain in the
same position. Bleeding oil from the actuator allows the spring to push on the piston,
closing the valve. Tripping the turbine causes hydraulic oil to be bled quickly from
beneath the piston, allowing the spring to quickly shut the valve. Steam pressure also
helps to close the valve by forcing the disc back toward the seat. When the valve is
closed as shown in figure (2), the flow of steam toward the HP turbine is shut off.
5.1.2 CONTROL VALVES- When the main stop valves are fully opened, the
flow of steam into the HP turbine is usually regulated by four or more control valves.
The control valves regulate the turbine speed or its power output. Steam from the main
stop valve flows to the control valves through a steam line. The steam is sent to different
sections of the turbines nozzle block through the four steam lines below the control
valves. Each control valve feeds only one section of the nozzle block.
The control valves are operated by hydraulic actuators. The control valves regulate
steam flow into the turbine by opening and closing in sequence. As each valve is
opened, more steam is admitted to the turbine. During normal operation, the control
valves are automatically positioned to compensate for changes in load. For example, if
load increases, the control valves are opened more which increase the flow of steam
21
into the turbine. If load decreases, the control valves are closed more which decrease
the flow of steam into the turbine. At full condition, all the control valves are completely
opened as shown in the figure.
5.2 TURBINE GOVERNING SYSTEM
5.2.1 MECHANICAL GOVERNOR
The purpose of a mechanical governor is to maintain the speed of the turbine at a desired
value when the generator is disconnected from the power supply.
MAIN PARTS OF MECHANICAL GOVERNOR
 Flyweights
 Bracket
 Spring
MECHANISM
When the turbine shaft rotates, the governor flyweights respond to the centrifugal forces
created by the rotations. As turbine speed increases, the centrifugal force increases,
causing the flyweights to move outward, overcoming the tension of the spring
The force of the spring tends to pull the flyweights toward the center of the governor.
When turbine speed decreases, the centrifugal force also decreases, allowing the spring
to pull the flyweights inward.
Fig 5.1 Mechanical Governor
22
GOVERNING SYSTEM AT HIGH SPEED- When the speed of the turbine
increases, the flyweights move outward, which causes the pilot valve stem to move
upward. The movement of the stem and disc unblocks the port of the control oil line
and allows oil to flow from the actuator, through the pilot valve, to the drain. The
resulting decrease in pressure beneath the piston allows the actuator spring to expand,
forcing the piston towards. This action decreases the opening of the control valve. Less
steam is admitted to the turbine and turbine speed decreases.
GOVERNING SYSTEM AT LOW SPEED- When turbine speed decreases, the
flyweights move inward and the connecting rod moves downward. As the rod moves
downward, the pilot valve also moves downward. Then the pilot valve blocks the drain
line and opens the lube oil supply line. As a result, oil from the supply oil line flows
through the pilot valve and then into the control oil line to the actuator. Now the
pressure of the lube oil causes the piston to move upward. Thus the opening of the
control valves increase and mare steam is admitted to the turbine. Hence the turbine
speed increases gradually until it reaches at desire speed.
5.3 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 orbuckets. 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.
23
CHAPTER-6
6.1 TURBINE EFFICIENCY
To maximize turbine efficiency the steam is expanded, doing work, in a number of
stages. These stages are characterized by how the energy is extracted from them and
are known as either impulse or reaction turbines. Most steam turbines use a mixture of
the reaction and impulse designs: each stage behaves as either one or the other, but the
overall turbine uses both. Typically, higher pressure sections are reaction type and
lower pressure stages are impulse type.
6.1.1 IMPULSE TURBINE EFFICIENCY
An impulse turbine has fixed nozzles that orient the steam flow into high speed jets.
These jets contain significant kinetic energy, which is converted into shaft rotation by
the bucket-like shaped rotor blades, 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. As the steam flows through the nozzle its pressure falls from inlet pressure to
the exit pressure (atmospheric pressure, or more usually, the condenser vacuum). Due
to this high ratio of expansion of steam, the steam leaves the nozzle with a very high
Fig 6.1 Velocity Triangle
24
velocity. The steam leaving the moving blades has a large portion of the maximum
velocity of the steam when leaving the nozzle. The loss of energy due to this higher exit
velocity is commonly called the carry over velocity or leaving loss.
The law of moment of momentum states that the sum of the moments of external forces
acting on a fluid, which is temporarily occupying the control volume is equal to the net
time change of angular momentum flux through the control volume.
The swirling fluid enters the control volume at radius with tangential
velocity and leaves at radius with tangential velocity .
A velocity triangle paves the way for a better understanding of the relationship between
the various velocities. In the adjacent figure we have
and are the absolute velocities at the inlet and outlet respectively.
and are the flow velocities at the inlet and outlet respectively.
and are the swirl velocities at the inlet and outlet respectively.
and are the relative velocities at the inlet and outlet respectively.
and are the velocities of the blade at the inlet and outlet respectively.
is the guide vane angle and is the blade angle.
Then by the law of moment of momentum, the torque on the fluid is given by:
For an impulse steam turbine: . Therefore, the tangential force on the
blades is . The work done per unit time or power
developed: .
When ω is the angular velocity of the turbine, then the blade speed is . The
power developed is then
.
BLADE EFFICIENCY- Blade efficiency ( ) can be defined as the ratio of the work
done on the blades to kinetic energy supplied to the fluid, and is given by
25
STAGE EFFICIENCY
Fig 6.2 Convergent Divergent Nozzel
Fig 6.3 Graph Depicting Efficiency of Impulse Turbine
A stage of an impulse turbine consists of a nozzle set and a moving wheel. The stage
efficiency defines a relationship between enthalpy drop in the nozzle and work done in
the stage.
6.1.2 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.
26
BLADE EFFICIENCY
Energy input to the blades in a stage:
is equal to the kinetic energy supplied to the fixed blades (f) + the kinetic
energy supplied to the moving blades (m).
Or, = enthalpy drop over the fixed blades, + enthalpy drop over the moving
blades, .
The effect of expansion of steam over the moving blades is to increase the relative
velocity at the exit. Therefore, the relative velocity at the exit is always greater than
the relative velocity at the inlet .
In terms of velocities, the enthalpy drop over the moving blades is given by:
(it contributes to a change in static pressure)
The enthalpy drop in the fixed blades, with the assumption that the velocity of steam
entering the fixed blades is equal to the velocity of steam leaving the previously moving
blades is given by:
Fig 6.4 Velocity Diagram
27
CONDITION OF MAXIMUM BLADE EFFICIENCY
Fig 6.5 Comparing Efficiencies of Impulse and Reaction turbines
28
CHAPTER-7
7.1 OPERATION AND MAINTENANCE
Fig 7.1 A Modern Steam Turbine Generator Installation
Because of the high pressures used in the steam circuits and the materials used, steam
turbines and their casings have high thermal inertia. When warming up a steam turbine
for use, the main steam stop valves (after the boiler) have a bypass line to allow
superheated steam to slowly bypass the valve and proceed to heat up the lines in the
system along with the steam turbine. Also, a turning gear is engaged when there is no
steam to slowly rotate the turbine to ensure even heating to prevent uneven expansion.
After first rotating the turbine by the turning gear, allowing time for the rotor to assume
a straight plane (no bowing), then the turning gear is disengaged and steam is admitted
to the turbine, first to the astern blades then to the ahead blades slowly rotating the
turbine at 10–15 RPM (0.17–0.25 Hz) to slowly warm the turbine. The warm up
procedure for large steam turbines may exceed ten hours.
During normal operation, rotor imbalance can lead to vibration, which, because of the
high rotation velocities, could lead to a blade breaking away from the rotor and through
the casing. To reduce this risk, considerable efforts are spent to balance the turbine.
Also, turbines are run with high quality steam: either superheated (dry) steam, or
saturated steam with a high dryness fraction. This prevents the rapid impingement and
erosion of the blades which occurs when condensed water is blasted onto the blades
(moisture carry over). Also, liquid water entering the blades may damage the thrust
bearings for the turbine shaft. To prevent this, along with controls and baffles in the
boilers to ensure high quality steam, condensate drains are installed in the steam piping
leading to the turbine.
29
Fig 7.2 Diagram Of A Steam Turbine Generator System
Maintenance requirements of modern steam turbines are simple and incur low costs
(typically around $0.005 per kWh); their operational life often exceeds 50 years.
7.2 SPEED REGULATION
The control of a turbine with a governor is essential, as turbines need to be run up
slowly to prevent damage and some applications (such as the generation of alternating
current electricity) require precise speed control. Uncontrolled acceleration of the
turbine rotor can lead to an overspeed trip, which causes the nozzle valves that control
the flow of steam to the turbine to close. If this fails then the turbine may continue
accelerating until it breaks apart, often catastrophically. Turbines are expensive to
make, requiring precision manufacture and special quality materials.
During normal operation in synchronization with the electricity network, power plants
are governed with a five percent droop speed control. This means the full load speed is
100% and the no-load speed is 105%. This is required for the stable operation of the
network without hunting and drop-outs of power plants. Normally the changes in speed
are minor. Adjustments in power output are made by slowly raising the droop curve by
increasing the spring pressure on a centrifugal governor. Generally this is a basic
system requirement for all power plants because the older and newer plants have to be
compatible in response to the instantaneous changes in frequency without depending
on outside communication.
30
8. CONCLUSION
Gone through one month training under the guidance of capable engineers and workers
of BHEL Bhopal in “ Steam Turbine Manufacturing” headed by Senior Engineer of
department Mr. Jitendra Singh.
The training was specified under the Turbine Manufacturing Department. Working
under the department I came to know about the basic grinding, scaling and machining
processes which was shown on heavy to medium machines. Duty lathes were planted
in the same line where the specified work was undertaken.
The training brought to my knowledge the various machining and fabrication processes
went not only in the manufacturing of blades but other parts of the turbine.
31
REFRENCES
1. https://www.bhelbpl.co.in/bplweb_new/
2. http://www.bhel.com/product_services/mainproduct.php
3. https://en.wikipedia.org/wiki/Steam_turbine
4. https://www.bhelbpl.co.in/bplweb_new/products/thermal/products.htm
5. https://www.bhelbpl.co.in/bplweb_new/products/thermal/reference.htm

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Training report on Steam Turbine Manufacturing at BHEL Bhopal

  • 1. A Summer Training Report on Steam Turbine Manufacturing at “Bharat Heavy Electricals Limited(Bhopal)” Submitted in partial fulfilment of the requirements for the degree of Bachelor of Technology in Mechanical Engineering Submitted By Abhishek DEPARTMENT OF MECHANICAL ENGINEERING NOIDA INSTITUTE OF ENGINEERING AND TECHNOLOGY Greater Noida, Uttar Pradesh APJ Abdul Kalam Technical University December 2017
  • 2. i ACKNOWLEDGENT I would like to express my gratitude for the people who were part of my training report, directly or indirectly people who gave unending support to complete my training and report. I would like thanks Dr. …………….. (HOD, M.E.) for providing this opportunity. A special gratitude to my guide Mr. ………….. (Deputy Manager-STM) and whose contribution in guidance, stimulating suggestions and encouragement, helped me to complete my vocational training in the BHEL, Bhopal. I would like to thanks to all those people who directly or indirectly helped and guided us to complete my training and this project including the following instructor, technical staff and supervisor of various section. Abhishek Roll No. 4th year/7th sem
  • 3. ii ABBREVIATIONS BHEL Bharat Heavy Electricals limited IP Intermidiate Pressure LP Low Pressure HP High Pressure STM Steam Turbine Manufacturing MSV Main Stop Valve ESV Emergency Stop Valve CV Control Valve GOVT Government PSU Public Sector Under Taking FY Financial Year MW Mega Watt GW Giga Watt AC Alternating Current ASME Americam Society Of Mechanical Engineers ISO International Organisation For Standardization KG Kilogram CM Centimeter TQM Total Quality Management
  • 4. iii ABSTRACT In the era of Mechanical Engineering, Turbine, A Prime Mover ( Which uses the Raw Energy of a substance and converts it to Mechanical Energy) is a well known machine most useful in the field of Power Generation. This Mechanical energy is used in running an Electric Generator which is directly coupled to the shaft of turbine. From this Electric Generator, we get electric Power which can be transmitted over long distances by means of transmission lines and transmission towers. In my Industrial Training in B.H.E.L., Bhopal I go through all sections in Turbine Manufacturing. First management team told me about the history of industry, Area, Capacity, Machines installed & Facilities in the Industry. After that they told about the Steam Turbine its types , parts like Blades, Casing, Rotor etc. Then they told full explanation of constructional features and procedure along with equipment used. Before telling about the machines used in Manufacturing of Blade, they told about the safety precautions, Step by Step arrangement of machines in the block with a well defined proper format. They also told the material of blade for a particular desire, types of Blades, Operations performed on Blades. During my training I was guided to manufacturing processes of different parts of steam turbine, heat exchangers and condensers. Turbine are categorised into three parts i.e. high pressure turbine, intermediate pressure turbine and low pressure turbine. Turbines are manufactured by lining up the various process like forging, casting, machining etc. which is followed by manufacturing. All these process are done in flow manner in order raise the work efficiency and minimise the efforts and time.
  • 5. iv TABLE OF CONTENTS Contents Page No. Acknowledgement…………………………………………………….. i Abbreviations………………………………………………………….. ii Abstract…………………………………………………………………. iii Table of Contents………………………………………………………. iv List of Figures…………………………………………………………... vi List of Tables…………………………………………………………… vii Chapter 1 1.1 BHEL – An Overview .............................................................................................1 1.2 Its Operation............................................................................................................1 1.3 Manufacturing Unit In India ....................................................................................2 1.4 Products Of BHEL…………………………………………………………………3 Chapter 2 2.1 BHEL-Bhopal ..........................................................................................................5 2.2 Awards And Recognition.........................................................................................5 2.3 Products Of BHEL Bhopal……………………………………………………….. 6 2.4 Details of Sets Supplied…………………………………………………………....7 Chapter 3 3.1 Steam Turbine……………………………………………………………………. 8 3.1.1 HP Turbine........................................................................................................9 3.1.2 IP Turbine..........................................................................................................9 3.1.3 LP Turbine.......................................................................................................10 3.2 Specifications of Steam Turbine…………………………………............…….....11 Chapter 4 4.1 Steam Turbine Components……………………...………………………………12 4.1.2 Shell.................................................................................................................13 4.1.3 Rotor................................................................................................................13 4.1.4 Governor Pedestal ...........................................................................................13
  • 6. v 4.1.5 Steam Turbine Rotor.......................................................................................13 4.1.6 Turbine Casing................................................................................................13 4.1.7 Turbine Flanges……………………………………………………………...14 4.2 Steam Turbine Blades............................................................................................15 4.2.1 Fixed Blade .....................................................................................................16 4.2.2 Moving Blade………....……………………………………………………..16 4.3 Impulse Turbines ...................................................................................................17 4.4 Reaction Turbines ..................................................................................................18 4.5 Blading Stages: ......................................................................................................19 Chapter 5 5.1 Valves ....................................................................................................................20 5.1.1 Main Stop Valves............................................................................................20 5.1.2 Control Valves.................................................................................................20 5.2 Turbine Governing System....................................................................................21 5.2.1 Mechanical Governor......................................................................................21 5.3 Principle Of Operation And Design.......................................................................22 Chapter 6 6.1 Turbine Efficiency .................................................................................................23 6.1.1 Impulse Turbine Efficiency.............................................................................23 6.1.2 Reaction Turbine.............................................................................................25 7.1 Operation And Maintenance..................................................................................28 7.2 Speed Regulation ...................................................................................................29 8. Conclusion…………………………………………………………………………30 References…………………………………………………………………………...31
  • 7. vi LIST OF FIGURES Fig No. Title Page No. Fig 1.1 BHEL Logo…………………………………….. 1 Fig 2.1 BHEL Bhopal…………………………………… 5 Fig 2.2 Products of BHEL Bhopal……………………….. 6 Fig 3.1 Steam Flow Diagram……………………………… 8 Fig 3.2 HP Turbine Rotor…………………………………. 9 Fig 3.3 Intermediate Pressure Turbine…………………….. 10 Fig 3.4 LP Turbine Rotor…………………………………. 10 Fig 4.1 Steam Turbine Foundation or Frame………………. 12 Fig 4.2 Turbine Upper Casing……………………………… 13 Fig 4.3 Turbine Lower Casing……………………………… 14 Fig 4.4 Turbine Flanges……………………………………. 15 Fig 4.5 Turbine Blades…………………………………….. 15 Fig 4.6 Fixed Blades………………………………………. 16 Fig 4.7 Moving Blades…………………………………….. 16 Fig 4.8 Combination of Blades……………………………. 17 Fig 4.9 Comparison Between Impulse and Reaction Turbine 18 Fig 4.10 Multi stage blading………………………………… 19 Fig 5.1 Mechanical Governor…………………………….. 21 Fig 6.1 Velocity Triangle………………………………….. 23 Fig 6.2 Convergent Divergent Nozzel……………………… 25 Fig 6.3 Graph Depicting Efficiency of Impulse Turbine…... 25 Fig 6.4 Velocity Diagram………………………………….. 26 Fig 6.5 Comparing Efficiencies of Impulse and Reaction turbines…………………………………………. 27 Fig 7.1 A Modern Steam Turbine Generator Installation… 28 Fig 7.2 Diagram Of A Steam Turbine Generator System… 29
  • 8. vii LIST OF TABLES Table No. Title Page No. Table 2.1 Table 2.1 Details of Turbine Sets Supplied 7 Table 3.1 Table 3.1 Specification of 236 MW Steam Turbine 11
  • 9. 1 CHAPTER-1 1.1 BHEL – AN OVERVIEW Bharat Heavy Electrical Limited (BHEL) owned by the Government of India, is a power plant equipment manufacturer and operates as engineering and manufacturing company based in New Delhi, India. Established in 1964, BHEL is India’s largest engineering and manufacturing company of its kind. The company has been earning profit continuously since 1971-72 and paying dividends uninterruptedly since 1976-77. It has been granted the prestigious Maharatna (big gem) status in 2013 by Govt of India for its outstanding performance. The elite list of Maharatna contains another 6 behemoth PSU companies of India. BHEL was established in 1964 Heavy Electricals (India) Limited was merged with BHEL in 1974. In 1982, it entered into power equipment, to reduce its dependence on the power sector. It developed the capability to produce a variety of electrical, electronic and mechanical equipments for all sectors, including transmission, transportation, oil and gas and other allied industries. In 1991, it was converted into a public limited company. By the end of 1996, the company had handed over 100 Electric Locomotives to Indian Railway and installed 250 Hydro-sets across India. 1.2 ITS OPERATION :- BHEL is engaged in the design, engineering, manufacturing, construction, testing, commissioning and servicing of a wide range of products, systems and services for the core sectors of the economy, viz. power, transmission, industry, transportation, renewable energy, oil & gas and defence. Fig 1.1 BHEL Logo
  • 10. 2 It has a network of 17 manufacturing units, 2 repair units, 4 regional offices, 8 service centres, 8 overseas offices, 15 regional centres, 7 joint ventures, and infrastructure allowing it to execute more than 150 projects at sites across India and abroad. The company has established the capability to deliver 20,000 MW p.a. of power equipment to address the growing demand for power generation equipment. BHEL has retained its market leadership position during 2015-16 with 74% market share in the Power Sector. An improved focus on project execution enabled BHEL record its highest ever commissioning/synchronization of 15059 MW of power plants in domestic and international markets in 2015-16, marking a 59% increase over 2014- 15. With the all-time high commissioning of 15000 MW in a single year FY2015-16, BHEL has exceeded 170 GW installed base of power generating equipments. It also has been exporting its power and industry segment products and services for over 40 years. BHEL's global references are spread across over 76 countries across all the six continents of the world. The cumulative overseas installed capacity of BHEL manufactured power plants exceeds 9,000 MW across 21 countries including Malaysia, Oman, Iraq, UAE, Bhutan, Egypt and New Zealand. Their physical exports range from turnkey projects to after sales services. 1.3 MANUFACTURING UNIT IN INDIA  Centralised Stamping Unit & Fabrication Plant (CSU & FP), Jagdishpur  Insulator Plant (IP), Jagdishpur  Electronics Division (EDN), Bangalore  Industrial Systems Group (ISG), Bangalore  Electro-Porcelains Division (EPD), Bangalore  Heavy Electrical Plant (HEP), Bhopal  Industrial Valves Plant (IVP), Goindwal  Heavy Electrical Equipment Plant (HEEP), Ranipur (Haridwar)  Central Foundry Forge Plant (CFFP), Ranipur (Haridwar)  Heavy Power Equipment Plant (HPEP), Hyderabad  Transformer Plant (TP), Jhansi  Boiler Auxiliaries Plant (BAP), Ranipet  Component Fabrication Plant (CFP), Rudrapur
  • 11. 3  High Pressure Boiler Plant (HPBP), Tiruchirappalli  Seamless Steel Tube Plant (SSTP), Tiruchirappalli  Power Plant Piping Unit (PPPU), Thirumayam  Heavy Plates & Vessels Plant (HPVP), Visakhapatnam 1.4 PRODUCTS OF BHEL 1. Thermal power Plants 2. Nuclear power Plants 3. Gas based power Plants 4. Hydro power Plants 5. DG power Plants 6. Boilers (steam generator) 7. Boiler Auxiliaries 8. Gas generator 9. Hydro generator 10. Steam turbine 11. Gas turbine 12. Hydro turbine 13. Transformer 14. Switchgear 15. Oil field equipment 16. Boiler drum 17. Piping System 18. Soot Blowers 19. Valves 20. Seamless Steel Tubes 21. Condenser s and Heat exchangers 22. Pumps 23. Desalination and Water treatment plants 24. Automation and Control systems 25. Power electronics
  • 12. 4 26. Transmission system control 27. Semiconductor devices 28. Solar photo voltaic 29. Software system solutions 30. Bus ducts 31. Insulators 32. Control panels 33. Capacitors 34. Bushings 35. Electrical machines 36. DC, AC heavy duty Motors 37. Compressors 38. Control gears 39. Traction motors 40. Research and development products
  • 13. 5 CHAPTER-2 2.1 BHEL-BHOPAL Vision: A Global Engineering Enterprise providing Solutions for better tomorrow Mission: Providing sustainable business solutions in the fields of Energy, Industry & Infrastructure Values: Governance, Respect, Excellence, Loyalty, Integrity, Commitment, Innovation, Team Work BHEL, Bhopal certified to ISO: 9001, ISO 14001 and OHSAS 18001, is moving towards superiority by acquiring TQM as per EFQM/CII model of Business Excellence. Heat Exchanger Division is accredited with ASME “U” Stamp. With the slogan of “Kadam Kadam milana hai, grahak safal banana hai”, it is committed to the customers. BHEL Bhopal has its own Laboratories for material testing and instrument calibration which are accredited with ISO 17025 by NABL. The hydro Laboratory and Centre for Electric Transportation are the only laboratories of it are in this part of world. Fig 2.1 BHEL Bhopal 2.2 AWARDS AND RECOGNITION National e-Governance Award: Bharat Heavy Electricals Limited (BHEL), has been conferred upon the prestigious National e-Governance Gold Award of Government of India for 2012-13, in the category – “Innovative use of ICT by PSUs for Customer
  • 14. 6 Benefits”, for the project “Integrated system for Online Generation of Electrical Specifications for Transformers” , developed by Informatics Centre (IFX) department, BHEL, Bhopal. CSI National Award (2013) : BHEL Bhopal has won the prestigious CSI National Award for Excellence in IT 2013 in the category of Business Collaboration solutions: Banking & Finance. Award for Excellence in e-Governance initiatives in MP: IT department of BHEL, Bhopal has been declared as Winner for Excellence Award in e-Governance initiatives in Madhya Pradesh for 2012-13, in the category – “The best application following best- practices of software development”, for the project “Online Recruitment system”, developed by Informatics Centre (IFX) department, BHEL, Bhopal. National e-Governance Gold Award 2014-15: Bharat Heavy Electricals Limited (BHEL) Bhopal has been conferred with the prestigious National e-Governance Gold award by Government of India during the 18th National Conference on e-Governance held at Gandhinagar, Gujarat. The award was given for the ‘SAMPARK’ project, developed by Information Services and Technology department (ITS), BHEL Bhopal. 2.3 PRODUCTS OF BHEL BHOPAL Power Utilisation AC Motors & Alternators Transportation Transportation Equipment Power Generation Hydro Turbines Hydro Generators Heat Exchangers Excitation Control Equipment Steam Turbines Miscellaneous Oil Rigs Fabrication Power Transmission Transformer Switchgear On-Load Tap Changer Large Current Rectifiers Control & Relay Panels Renovation & Maintenance Thermal Power Stations Fig 2.2 Products of BHEL Bhopal
  • 15. 7 2.4 DETAILS OF SETS SUPPLIED Table 2.1 Details of Turbine Sets Supplied Rating (MW) Type No. of Sets Supplied First Set Commissioned 30 Single cylinder / impulse 6 1969 120 Three cylinder / impulse / reheat 18 1974 210 Three cylinder / reaction / reheat 11 1988 236 Two cylinder / impulse / reheat 10 1983 15000 SHP Marine Turbine / impulse / non reheat 20 1974 Industrial Turbine Condensing / Back pressure 4 1998
  • 16. 8 CHAPTER-3 3.1 STEAM TURBINE A steam turbine is a device that extracts thermal energy from pressurized steam and uses it to do mechanical work on a rotating output shaft. Its modern manifestation was invented by Sir Charles Parsons in 1884. Because the turbine generates rotary motion, it is particularly suited to be used to drive an electrical generator – about 90% of all electricity generation in the United States (1996) is by use of steam turbines. The steam turbine is a form of heat engine that derives much of its improvement in thermodynamic efficiency from the use of multiple stages in the expansion of the steam, which results in a closer approach to the ideal reversible expansion process. Steam turbines are used for the generation of electricity in thermal power plants, such as plants using coal, fuel oil or nuclear fuel. They were once used to directly drive mechanical devices such as ships' propellers (for example the Turbinia, the first turbine-powered steam launch) but most such applications now use reduction gears or an intermediate electrical step, where the turbine is used to generate electricity, which then powers an electric motor connected to the mechanical load. Turbo electric ship machinery was particularly popular in the period immediately before and during World War II, primarily due to a lack of sufficient gear-cutting facilities in US and UK shipyards. Fig 3.1 Steam Flow Diagram
  • 17. 9 There are three sections to a steam turbine viz. high pressure, intermediate pressure and low pressure turbine. All three are mounted on the same shaft which rotates at about 3600 rpm in a generator to make electricity.  HP Turbine  IP Turbine  LP Turbine 3.1.1 HP Turbine • Single flow • Double shell casing 1. Inner casing vertically split 2. Outer casing barrel type & axially divided 3. Single exhaust in L/H • Mono block rotor • Casing mounted valves • Internal bypass cooling • Transported as single unit Fig 3.2 HP Turbine Rotor 3.1.2 IP Turbine • Double flow • Double casing design with horizontal split • Inlet from Lower half
  • 18. 10 • Single Exhaust from upper half • Extraction connections from lower half • Admission blade ring Fig 3.3 Intermediate Pressure Turbine 3.1.3 LP Turbine • Double flow • Double shell casing • Single admission from top half • Outer Casing & condenser rigidly connected • Push rod arrangement to minimize axial clearances • Mono block rotor • Inner / Outer casing fabricated Fig 3.4 LP Turbine Rotor
  • 19. 11 3.2 SPECIFICATIONS OF STEAM TURBINE Table 3.1 Specification of 236 MW Steam Turbine S.No Description Parameter 1 Rated capacity 236 mw 2 Pressure at stop valve 40 kg/cm2 3 Temperature at stop valve 250 c 4 Max. Steam flow at s.v 1332.2 tonnes /hr 5 Reheat/non reheat Reheat 6 Type of governing Throttle control 7 Turbine speed 3000 rpm 8 Exhaust pressure 63.5 mm hg abs 9 Number of cylinders H.P-1,double flow LP-1 10 Number of stages HP-5, LP-5 + 5 11 Height of last stage blade 945 mm 12 Last stage mean dia 2641 mm 13 Special feature Steam at stop valve is wet - bled steam and live steam reheating 14 Weight of turbine 450 tonnes 15 Length of turbine 15 meters 16 Type of turbine Impulse 17 Collaborator GEC U.K
  • 20. 12 CHAPTER-4 4.1 STEAM TURBINE COMPONENTS  Steam turbine foundation or frame  Rotor  Governor Pedestal  Turbine Casing 1. Upper Casing 2. Lower Casing  Turbine Casing Flanges  Steam Turbine Blades 1. Fixed Blades or Diaphragm 2. Moving Blades  Valves 1. Main Stop Valve 2. Control Valve  Turbine Governing System Fig 4.1 Steam Turbine Foundation or Frame
  • 21. 13 4.1.1 FRAME (BASE) - supports the stator, rotor and governor pedestal. 4.1.2 SHELL – Consists cylinder, casing, nozzle, steam chest & bearing. 4.1.3 ROTOR – consists of low, intermediate, high pressure stage blades and possible stub shaft(s) for governor pedestal components, thrust bearing, journal bearings, turning gear & main lube oil system. 4.1.4 GOVERNOR PEDESTAL – consists of the EHC oil system, turbine speed governor, and protective devices. 4.1.5 STEAM TURBINE ROTOR – Multistage steam turbines are manufactured with solid forged rotor construction. Rotors are precisely machined from solid alloy steel forging. An integrally forged rotor provides increased reliability particularly for high speed applications. The complete rotor assembly is dynamically balanced at operating speed and over speed tested in a vacuum bunker to ensure safety in operation. High speed balancing can also reduce residual stresses and the effects of blade seating. 4.1.6 TURBINE CASING – The casing of turbine cylinders are of simple construction to minimize any distortion due to temperature changes. They are constructed in two halves (top and bottom) along a horizontal joint so that the cylinder is easily opened for inspection and maintenance. With the top cylinder casing removed the rotor can also be easily withdrawn without interfering with the alignment of the bearings. Fig 4.2 Turbine Upper Casing
  • 22. 14 Most turbines constructed today either have a double or partial double casing on the high pressure (HP) or intermediate pressure (IP) cylinders. This arrangement subjects the outer casing joint flanges, bolts and outer casing glands to lower steam condition. This also makes it possible for reverse flow within the cylinder and greatly reduces fabrication thickness as pressure within the cylinder is distributed across two casings instead of one. This reduced the wall thickness also enables the cylinder to respond more rapidly to changes in steam temperature due to the thermal mass. Fig 4.3 Turbine Lower Casing The high pressure end of the turbine is supported by the steam end bearing housing which is flexibly mounted to allow for axial expansion caused by temperature changes. The exhaust casing is centreline supported on pedestals that maintain perfect unit alignment while permitting lateral expansion. Covers on both the steam end and exhaust end bearing housings and seal housings may be lifted independently of the main casing to provide ready access to such items as the bearings, control components and seals. 4.1.7 TURBINE CASING FLANGES- One method of joining the top and bottom halves of the cylinder casing is by using flanges with machined holes. Bolts or studs are insertion into these machined holes to hold the top and bottom halves together. To
  • 23. 15 prevent leakage from the joint between the top flange and the bottom flange the are accurately machined. Fig 4.4 Turbine Flanges Another method of joining top and bottom cylinder flanges is by clamps bolted radially around the outer of cylinder. The outer faces of flanges are made of wedge shaped so that the tighter the clamps are pulled the greater the pressure on the joint faces. 4.2 STEAM TURBINE BLADES The energy conversion takes place through the turbine blades. A turbine consists of alternate rows of blades. This blades convert the chemical or thermal energy of working fluid into kinetic energy and then from kinetic energy to mechanical energy as rotation of the shaft. Fig 4.5 Turbine Blades
  • 24. 16 There are two types of blade, fixed and moving blade. Moving blade is also two types. One is impulse blade and another reaction blade. 4.2.1 FIXED BLADE- A fixed blade assembly is very important for turbine blading. It is also known as diaphragm. The shape of the blade is the key to the energy conversion process. Since the fixed blades have a conversing nozzle shape, it is also called nozzles. When steam is passed over the fixed blades, they increase the velocity of steam as an operation of nozzles. Here blades are converted the thermal energy of steam into kinetic energy by causing the steam to speed up and gain velocity. Fig 4.6 Fixed Blades 4.2.2 MOVING BLADE- Moving blade can be shaped in either of two ways: reaction shaped or impulse shaped. The shape of the blade determines how the energy is actually converted. Either type of moving blades or a combination of both can be attached to the shaft of the rotor on dices, called wheels as shown in the figure 4.7. Fig 4.7 Moving Blades
  • 25. 17 Along the outer rim of the blades is a metal band, called shrouding which ties the blades together. The moving blades convert the kinetic energy in the moving speed into the mechanical energy as rotor rotation. Fig 4.8 Combination of Blades 4.3 IMPULSE TURBINES These turbines change the direction of flow of a high velocity fluid or gas jet. The resulting impulse spins the turbine and leaves the fluid flow with diminished kinetic energy. There is no pressure change of the fluid or gas in the turbine rotor blades as in the case of a steam or gas turbine, all the pressure drop takes place in the stationary blades. Before reaching the turbine, the fluid's pressure head is changed to velocity head by accelerating the fluid with a nozzle. Impulse turbines do not require a pressure casement around the rotor since the fluid jet is created by the nozzle prior to reaching the blading on the rotor. Newton's second law describes the transfer of energy for impulse turbines.
  • 26. 18 4.4 REACTION TURBINES These turbines develop torque by reacting to the gas or fluid's pressure or mass. The pressure of the gas or fluid changes as it passes through the turbine rotor blades. A pressure casement is needed to contain the working fluid as it acts on the turbine stages or the turbine must be fully immersed in the fluid flow. The casing contains and directs the working fluid and, for water turbines, maintains the suction imparted by the draft tube. Francis turbines and most steam turbines use this concept. For compressible working fluids, multiple turbine stages are usually used to harness the expanding gas efficiently. Newton's third law describes the transfer of energy for reaction turbines. Fig 4.9 Comparison Between Impulse and Reaction Turbine 4.5 BLADING STAGES: Two successive fixed and moving blades are collectively known as blading stage. The effects of pressure and velocity of working fluids depend upon the stage conditions. In Ashuganj power station, the turbines which are used have 23 stages at HP turbine and 21 stages at IP & LP turbine. Now the effects of pressure and velocity on various blading stages are described in below:
  • 27. 19 For impulse blading velocity increases and pressure decreases across each row as the steam passes through the fixed blading. Again when steam passes through the impulse type moving blade, its velocity decreases, but its pressure remains constant as shown in the figure. For reaction blading velocity increases and the pressure decreases across each row as the steam passes through the fixed blading. When steam passes through the reaction type moving blade, its pressure and velocity both decreases as shown. Fig 4.10 Multi stage blading
  • 28. 20 CHAPTER-5 5.1 VALVES Steam from the boiler is routed to the turbine through a steam line that contains the main stop valves and the control valves. 5.1.1 MAIN STOP VALVES- It is such a valve through which steam passes to the turbine blades. By controlling this valve steam flow can be controlled. Each main stop valve consists of a valve disk, a valve stem and a hydraulic actuator. The hydraulic actuator contains a piston and a compression spring. Since the valve disk and stems are connected to the piston, movement of the piston causes movement of the valve disc. During normal turbine operation, hydraulic oil is directed into or out of the hydraulic actuator. Directing oil into the actuator opens the valve and compresses the spring. As long as the amount of oil in actuator is held constant, the valve will remain in the same position. Bleeding oil from the actuator allows the spring to push on the piston, closing the valve. Tripping the turbine causes hydraulic oil to be bled quickly from beneath the piston, allowing the spring to quickly shut the valve. Steam pressure also helps to close the valve by forcing the disc back toward the seat. When the valve is closed as shown in figure (2), the flow of steam toward the HP turbine is shut off. 5.1.2 CONTROL VALVES- When the main stop valves are fully opened, the flow of steam into the HP turbine is usually regulated by four or more control valves. The control valves regulate the turbine speed or its power output. Steam from the main stop valve flows to the control valves through a steam line. The steam is sent to different sections of the turbines nozzle block through the four steam lines below the control valves. Each control valve feeds only one section of the nozzle block. The control valves are operated by hydraulic actuators. The control valves regulate steam flow into the turbine by opening and closing in sequence. As each valve is opened, more steam is admitted to the turbine. During normal operation, the control valves are automatically positioned to compensate for changes in load. For example, if load increases, the control valves are opened more which increase the flow of steam
  • 29. 21 into the turbine. If load decreases, the control valves are closed more which decrease the flow of steam into the turbine. At full condition, all the control valves are completely opened as shown in the figure. 5.2 TURBINE GOVERNING SYSTEM 5.2.1 MECHANICAL GOVERNOR The purpose of a mechanical governor is to maintain the speed of the turbine at a desired value when the generator is disconnected from the power supply. MAIN PARTS OF MECHANICAL GOVERNOR  Flyweights  Bracket  Spring MECHANISM When the turbine shaft rotates, the governor flyweights respond to the centrifugal forces created by the rotations. As turbine speed increases, the centrifugal force increases, causing the flyweights to move outward, overcoming the tension of the spring The force of the spring tends to pull the flyweights toward the center of the governor. When turbine speed decreases, the centrifugal force also decreases, allowing the spring to pull the flyweights inward. Fig 5.1 Mechanical Governor
  • 30. 22 GOVERNING SYSTEM AT HIGH SPEED- When the speed of the turbine increases, the flyweights move outward, which causes the pilot valve stem to move upward. The movement of the stem and disc unblocks the port of the control oil line and allows oil to flow from the actuator, through the pilot valve, to the drain. The resulting decrease in pressure beneath the piston allows the actuator spring to expand, forcing the piston towards. This action decreases the opening of the control valve. Less steam is admitted to the turbine and turbine speed decreases. GOVERNING SYSTEM AT LOW SPEED- When turbine speed decreases, the flyweights move inward and the connecting rod moves downward. As the rod moves downward, the pilot valve also moves downward. Then the pilot valve blocks the drain line and opens the lube oil supply line. As a result, oil from the supply oil line flows through the pilot valve and then into the control oil line to the actuator. Now the pressure of the lube oil causes the piston to move upward. Thus the opening of the control valves increase and mare steam is admitted to the turbine. Hence the turbine speed increases gradually until it reaches at desire speed. 5.3 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 orbuckets. 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.
  • 31. 23 CHAPTER-6 6.1 TURBINE EFFICIENCY To maximize turbine efficiency the steam is expanded, doing work, in a number of stages. These stages are characterized by how the energy is extracted from them and are known as either impulse or reaction turbines. Most steam turbines use a mixture of the reaction and impulse designs: each stage behaves as either one or the other, but the overall turbine uses both. Typically, higher pressure sections are reaction type and lower pressure stages are impulse type. 6.1.1 IMPULSE TURBINE EFFICIENCY An impulse turbine has fixed nozzles that orient the steam flow into high speed jets. These jets contain significant kinetic energy, which is converted into shaft rotation by the bucket-like shaped rotor blades, 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. As the steam flows through the nozzle its pressure falls from inlet pressure to the exit pressure (atmospheric pressure, or more usually, the condenser vacuum). Due to this high ratio of expansion of steam, the steam leaves the nozzle with a very high Fig 6.1 Velocity Triangle
  • 32. 24 velocity. The steam leaving the moving blades has a large portion of the maximum velocity of the steam when leaving the nozzle. The loss of energy due to this higher exit velocity is commonly called the carry over velocity or leaving loss. The law of moment of momentum states that the sum of the moments of external forces acting on a fluid, which is temporarily occupying the control volume is equal to the net time change of angular momentum flux through the control volume. The swirling fluid enters the control volume at radius with tangential velocity and leaves at radius with tangential velocity . A velocity triangle paves the way for a better understanding of the relationship between the various velocities. In the adjacent figure we have and are the absolute velocities at the inlet and outlet respectively. and are the flow velocities at the inlet and outlet respectively. and are the swirl velocities at the inlet and outlet respectively. and are the relative velocities at the inlet and outlet respectively. and are the velocities of the blade at the inlet and outlet respectively. is the guide vane angle and is the blade angle. Then by the law of moment of momentum, the torque on the fluid is given by: For an impulse steam turbine: . Therefore, the tangential force on the blades is . The work done per unit time or power developed: . When ω is the angular velocity of the turbine, then the blade speed is . The power developed is then . BLADE EFFICIENCY- Blade efficiency ( ) can be defined as the ratio of the work done on the blades to kinetic energy supplied to the fluid, and is given by
  • 33. 25 STAGE EFFICIENCY Fig 6.2 Convergent Divergent Nozzel Fig 6.3 Graph Depicting Efficiency of Impulse Turbine A stage of an impulse turbine consists of a nozzle set and a moving wheel. The stage efficiency defines a relationship between enthalpy drop in the nozzle and work done in the stage. 6.1.2 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.
  • 34. 26 BLADE EFFICIENCY Energy input to the blades in a stage: is equal to the kinetic energy supplied to the fixed blades (f) + the kinetic energy supplied to the moving blades (m). Or, = enthalpy drop over the fixed blades, + enthalpy drop over the moving blades, . The effect of expansion of steam over the moving blades is to increase the relative velocity at the exit. Therefore, the relative velocity at the exit is always greater than the relative velocity at the inlet . In terms of velocities, the enthalpy drop over the moving blades is given by: (it contributes to a change in static pressure) The enthalpy drop in the fixed blades, with the assumption that the velocity of steam entering the fixed blades is equal to the velocity of steam leaving the previously moving blades is given by: Fig 6.4 Velocity Diagram
  • 35. 27 CONDITION OF MAXIMUM BLADE EFFICIENCY Fig 6.5 Comparing Efficiencies of Impulse and Reaction turbines
  • 36. 28 CHAPTER-7 7.1 OPERATION AND MAINTENANCE Fig 7.1 A Modern Steam Turbine Generator Installation Because of the high pressures used in the steam circuits and the materials used, steam turbines and their casings have high thermal inertia. When warming up a steam turbine for use, the main steam stop valves (after the boiler) have a bypass line to allow superheated steam to slowly bypass the valve and proceed to heat up the lines in the system along with the steam turbine. Also, a turning gear is engaged when there is no steam to slowly rotate the turbine to ensure even heating to prevent uneven expansion. After first rotating the turbine by the turning gear, allowing time for the rotor to assume a straight plane (no bowing), then the turning gear is disengaged and steam is admitted to the turbine, first to the astern blades then to the ahead blades slowly rotating the turbine at 10–15 RPM (0.17–0.25 Hz) to slowly warm the turbine. The warm up procedure for large steam turbines may exceed ten hours. During normal operation, rotor imbalance can lead to vibration, which, because of the high rotation velocities, could lead to a blade breaking away from the rotor and through the casing. To reduce this risk, considerable efforts are spent to balance the turbine. Also, turbines are run with high quality steam: either superheated (dry) steam, or saturated steam with a high dryness fraction. This prevents the rapid impingement and erosion of the blades which occurs when condensed water is blasted onto the blades (moisture carry over). Also, liquid water entering the blades may damage the thrust bearings for the turbine shaft. To prevent this, along with controls and baffles in the boilers to ensure high quality steam, condensate drains are installed in the steam piping leading to the turbine.
  • 37. 29 Fig 7.2 Diagram Of A Steam Turbine Generator System Maintenance requirements of modern steam turbines are simple and incur low costs (typically around $0.005 per kWh); their operational life often exceeds 50 years. 7.2 SPEED REGULATION The control of a turbine with a governor is essential, as turbines need to be run up slowly to prevent damage and some applications (such as the generation of alternating current electricity) require precise speed control. Uncontrolled acceleration of the turbine rotor can lead to an overspeed trip, which causes the nozzle valves that control the flow of steam to the turbine to close. If this fails then the turbine may continue accelerating until it breaks apart, often catastrophically. Turbines are expensive to make, requiring precision manufacture and special quality materials. During normal operation in synchronization with the electricity network, power plants are governed with a five percent droop speed control. This means the full load speed is 100% and the no-load speed is 105%. This is required for the stable operation of the network without hunting and drop-outs of power plants. Normally the changes in speed are minor. Adjustments in power output are made by slowly raising the droop curve by increasing the spring pressure on a centrifugal governor. Generally this is a basic system requirement for all power plants because the older and newer plants have to be compatible in response to the instantaneous changes in frequency without depending on outside communication.
  • 38. 30 8. CONCLUSION Gone through one month training under the guidance of capable engineers and workers of BHEL Bhopal in “ Steam Turbine Manufacturing” headed by Senior Engineer of department Mr. Jitendra Singh. The training was specified under the Turbine Manufacturing Department. Working under the department I came to know about the basic grinding, scaling and machining processes which was shown on heavy to medium machines. Duty lathes were planted in the same line where the specified work was undertaken. The training brought to my knowledge the various machining and fabrication processes went not only in the manufacturing of blades but other parts of the turbine.
  • 39. 31 REFRENCES 1. https://www.bhelbpl.co.in/bplweb_new/ 2. http://www.bhel.com/product_services/mainproduct.php 3. https://en.wikipedia.org/wiki/Steam_turbine 4. https://www.bhelbpl.co.in/bplweb_new/products/thermal/products.htm 5. https://www.bhelbpl.co.in/bplweb_new/products/thermal/reference.htm