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The final step in the process of casting usually involves grinding, sanding, or machining the
component in order to achieve the desired dimensional accuracies, physical shape, and surface
finish.
Removing the remaining gate material, called a gate stub, is usually done using
a grinder or sander. These processes are used because their material removal rates are slow
enough to control the amount of material being removed. These steps are done prior to any
final machining.
After grinding, any surfaces that require tight dimensional control are machined. Many
castings are machined in CNC milling centers. The reason for this is that these processes have
better dimensional capability and repeatability than many casting processes. However, it is not
uncommon today for castings to be used without machining.
A few foundries provide other services before shipping cast products to their customers. It is
common to paint castings to prevent corrosion and improve visual appeal. Some foundries
assemble castings into complete machines or sub-assemblies. Other foundries weld multiple
castings or wrought metals together to form a finished product.[3]
More and more, finishing processes are being performed by robotic machines, which eliminate
the need for a human to physically grind or break parting lines, gating material, or feeders.
Machines can reduce risk of injury to workers and lower costs for consumables — while also
increasing productivity. They also limit the potential for human error and increase repeatability
in the quality of grinding
Fig. Flowchart of a typical Foundary process](https://image.slidesharecdn.com/jaideepnewbhelproject-180331092607/85/BHEL-PROJECT-REPORT-TRAINING-REPORT-20-320.jpg)
![25
Francis Inlet Scroll, Grand Coulee Dam Small Swiss-made Francis turbine
Francis turbines may be designed for a wide range of heads and flows. This, along with their
high efficiency, has made them the most widely used turbine in the world. Francis type units
cover a head range from 40 to 600 m (130 to 2,000 ft), and their connected generator output
power varies from just a few kilowatts up to 800 MW.[2]
Large Francis turbines are
individually designed for each site to operate with the given water supply and water head at
the highest possible efficiency, typically over 90%.
KAPLAN TURBINE
The Kaplan turbine is a propeller-type water turbine which has adjustable blades. It was
developed in 1913 by Austrian professor Viktor Kaplan, who combined automatically
adjusted propeller blades with automatically adjusted wicket gates to achieve efficiency over
a wide range of flow and water level.](https://image.slidesharecdn.com/jaideepnewbhelproject-180331092607/85/BHEL-PROJECT-REPORT-TRAINING-REPORT-25-320.jpg)
![27
STEAM TURBINE SECTION
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.
MANUFACTURING
The present-day manufacturing industry for steam turbines is dominated by Chinese power
equipment makers. Harbin Electric, Shanghai Electric, and Dongfang Electric, the top three
power equipment makers in China, collectively hold a majority stake in the worldwide
market share for steam turbines in 2009-10 according to Platts.[13]
Other manufacturers with
minor market share include Bhel, Siemens, Alstom, GE, Doosan Škoda Power, Mitsubishi
Heavy Industries, and Toshiba.[13]
The consulting firm Frost & Sullivan projects that
manufacturing of steam turbines will become more consolidated by 2020 as Chinese power
manufacturers win increasing business outside of China.
TYPES
Steam turbines are made in a variety of sizes ranging from small <0.75 kW (<1 hp) units
(rare) used as mechanical drives for pumps, compressors and other shaft driven equipment,
to 1 500 000 kW (1.5 GW; 2 000 000 hp) turbines used to generate electricity. There are
several classifications for modern steam turbines.
Blade and stage design
Schematic diagram outlining the difference between an impulse and a 50% reaction turbine](https://image.slidesharecdn.com/jaideepnewbhelproject-180331092607/85/BHEL-PROJECT-REPORT-TRAINING-REPORT-27-320.jpg)
![28
Turbine blades are of two basic types, blades and nozzles. Blades move entirely due to the
impact of steam on them and their profiles do not converge. This results in a steam velocity
drop and essentially no pressure drop as steam moves through the blades. A turbine
composed of blades alternating with fixed nozzles is called an impulse turbine, Curtis
turbine, Rateau turbine, or Brown-Curtis turbine. Nozzles appear similar to blades, but their
profiles converge near the exit. This results in a steam pressure drop and velocity increase as
steam moves through the nozzles. Nozzles move due to both the impact of steam on them
and the reaction due to the high-velocity steam at the exit. A turbine composed of moving
nozzles alternating with fixed nozzles is called a reaction turbine or Parsons turbine.Multiple
reaction stages divide the pressure drop between the steam inlet and exhaust into numerous
small drops, resulting in a pressure-compounded turbine. Impulse stages may be either
pressure-compounded, velocity-compounded, or pressure-velocity compounded. A pressure-
compounded impulse stage is a row of fixed nozzles followed by a row of moving blades,
with multiple stages for compounding. This is also known as a Rateau turbine, after its
inventor. A velocity-compounded impulse stage (invented by Curtis and also called a
"Curtis wheel") is a row of fixed nozzles followed by two or more rows of moving blades
alternating with rows of fixed blades. This divides the velocity drop across the stage into
several smaller drops.]
A series of velocity-compounded impulse stages is called a pressure-
velocity compounded turbine.
Blade Design Challenges
A major challenge facing turbine design is reducing the creep experienced by the blades.
Because of the high temperatures and high stresses of operation, steam turbine materials
become damaged through these mechanisms. As temperatures are increased in an effort to
improve turbine efficiency, creep becomes more significant. To limit creep, thermal coatings
and superalloys with solid-solution strengthening and grain boundary strengthening are used
in blade designs.
Refractory elements such as rhenium and ruthenium can be added to the alloy to improve
creep strength. The addition of these elements reduces the diffusion of the gamma prime
phase, thus preserving the fatigue resistance, strength, and creep resistance.
Steam supply and exhaust conditions
These types include condensing, non-condensing, reheat, extraction and induction.
Condensing turbines are most commonly found in electrical power plants. These turbines
receive steam from a boiler and exhaust it to a condenser. The exhausted steam is at a
pressure well below atmospheric, and is in a partially condensed state, typically of
a quality near 90%.
Reheat turbines are also used almost exclusively in electrical power plants. In a reheat
turbine, steam flow exits from a high-pressure section of the turbine and is returned to the
boiler where additional superheat is added. The steam then goes back into an intermediate
pressure section of the turbine and continues its expansion](https://image.slidesharecdn.com/jaideepnewbhelproject-180331092607/85/BHEL-PROJECT-REPORT-TRAINING-REPORT-28-320.jpg)
![32
Deviations from ideal
The ideal transformer model neglects the following basic linear aspects in real transformers.
Core losses, collectively called magnetizing current losses, consist of
Hysteresis losses due to nonlinear application of the voltage applied in the
transformer core, and
Eddy current losses due to joule heating in the core that are proportional to the square
of the transformer's applied voltage.
Whereas windings in the ideal model have no resistances and infinite inductances, the
windings in a real transformer have finite non-zero resistances and inductances associated
with:
Joule losses due to resistance in the primary and secondary windings
Leakage flux that escapes from the core and passes through one winding only resulting
in primary and secondary reactive impedance.
a
Leakage flux
The ideal transformer model assumes that all flux generated by the primary winding links all
the turns of every winding, including itself. In practice, some flux traverses paths that take it
outside the windings.[24]
Such flux is termed leakage flux, and results in leakage
inductance in series with the mutually coupled transformer windings.[10]
Leakage flux results
in energy being alternately stored in and discharged from the magnetic fields with each cycle
of the power supply. It is not directly a power loss, but results in inferior voltage regulation,
causing the secondary voltage not to be directly proportional to the primary voltage,
particularly under heavy load.[24]
Transformers are therefore normally designed to have very
low leakage inductance.
Equivalent circuit
Referring to the diagram, a practical transformer's physical behavior may be represented by
an equivalent circuit model, which can incorporate an ideal transformer.](https://image.slidesharecdn.com/jaideepnewbhelproject-180331092607/85/BHEL-PROJECT-REPORT-TRAINING-REPORT-32-320.jpg)
![35
Transformers for use at power or audio frequencies typically have cores made of high
permeability silicon steel. The steel has a permeability many times that of free space and the
core thus serves to greatly reduce the magnetizing current and confine the flux to a path which
closely couples the windings.Early transformer developers soon realized that cores
constructed from solid iron resulted in prohibitive eddy current losses, and their designs
mitigated this effect with cores consisting of bundles of insulated iron wires. Later designs
constructed the core by stacking layers of thin steel laminations, a principle that has remained
in use. Each lamination is insulated from its neighbors by a thin non-conducting layer of
insulation. The universal transformer
Solid cores
Powdered iron cores are used in circuits such as switch-mode power supplies that operate
above mains frequencies and up to a few tens of kilohertz. These materials combine high
magnetic permeability with high bulk electrical resistivity. For frequencies extending beyond
the VHF band, cores made from non-conductive magnetic ceramic materials
called ferrites are common.Some radio-frequency transformers also have movable cores
(sometimes called 'slugs') which allow adjustment of the coupling
coefficient (and bandwidth) of tuned radio-frequency circuits.
Air cores
A physical core is not an absolute requisite and a functioning transformer can be produced
simply by placing the windings near each other, an arrangement termed an 'air-core'
transformer. The air which comprises the magnetic circuit is essentially lossless, and so an
air-core transformer eliminates loss due to hysteresis in the core material.[10]
The leakage
inductance is inevitably high, resulting in very poor regulation, and so such designs are
unsuitable for use in power distribution.They have however very high bandwidth, and are
frequently employed in radio-frequency applications, for which a satisfactory coupling
coefficient is maintained by carefully overlapping the primary and secondary windings.
They're also used for resonant transformers such as Tesla coils where they can achieve
reasonably low loss in spite of the high leakage inductance.](https://image.slidesharecdn.com/jaideepnewbhelproject-180331092607/85/BHEL-PROJECT-REPORT-TRAINING-REPORT-35-320.jpg)
![36
Windings
The conducting material used for the windings depends upon the application, but in all cases
the individual turns must be electrically insulated from each other to ensure that the current
travels throughout every turn.[62]
For small power and signal transformers, in which currents
are low and the potential difference between adjacent turns is small, the coils are often wound
from enamelled magnet wire, such as Formvar wire. Larger power transformers operating at
high voltages may be wound with copper rectangular strip conductors insulated by oil-
impregnated paper and blocks of pressboard.
Cooling
Cutaway view of liquid-immersed construction transformer. The conservator (reservoir) at
top provides liquid-to-atmosphere isolation as coolant level and temperature changes. The
walls and fins provide required heat dissipation balance.
See also: Arrhenius equation
To place the cooling problem in perspective, the accepted rule of thumb is that the life
expectancy of insulation in all electrics, including all transformers, is halved for about every
7 °C to 10 °C increase in operating temperature, this life expectancy halving rule holding
more narrowly when the increase is between about 7 °C to 8 °C in the case of transformer
winding cellulose insulation.
Small dry-type and liquid-immersed transformers are often self-cooled by natural convection
and radiation heat dissipation. As power ratings increase, transformers are often cooled by
forced-air cooling, forced-oil cooling, water-cooling, or combinations of these.Large
transformers are filled with transformer oil that both cools and insulates the
windings. Transformer oil is a highly refined mineral oil that cools the windings and
insulation by circulating within the transformer tank. The mineral oil and paper insulation
system has been extensively studied and used for more than 100 years.
Insulation drying
Construction of oil-filled transformers requires that the insulation covering the windings be
thoroughly dried of residual moisture before the oil is introduced. Drying is carried out at the
factory, and may also be required as a field service. Drying may be done by circulating hot](https://image.slidesharecdn.com/jaideepnewbhelproject-180331092607/85/BHEL-PROJECT-REPORT-TRAINING-REPORT-36-320.jpg)
![37
air around the core, or by vapor-phase drying (VPD) where an evaporated solvent transfers
heat by condensation on the coil and core.
For small transformers, resistance heating by injection of current into the windings is used.
The heating can be controlled very well, and it is energy efficient. The method is called low-
frequency heating (LFH) since the current used is at a much lower frequency than that of the
power grid, which is normally 50 or 60 Hz. A lower frequency reduces the effect of
inductance, so the voltage required can be reduced. The LFH drying method is also used for
service of older transformers.
Bushings
Larger transformers are provided with high-voltage insulated bushings made of polymers or
porcelain. A large bushing can be a complex structure since it must provide careful control
of the electric field gradient without letting the transformer leak oil.[84]
Classification parameters
Transformers can be classified in many ways, such as the following:
Power capacity: From a fraction of a volt-ampere (VA) to over a thousand MVA.
Duty of a transformer: Continuous, short-time, intermittent, periodic, varying.
Frequency range: Power-frequency, audio-frequency, or radio-frequency.
Voltage class: From a few volts to hundreds of kilovolts.
Cooling type: Dry and liquid-immersed – self-cooled, forced air-cooled; liquid-
immersed – forced oil-cooled, water-cooled.
Types
Various specific electrical application designs require a variety of transformer types.
Although they all share the basic characteristic transformer principles, they are customize in
construction or electrical properties for certain installation requirements or circuit conditions.
Autotransformer: Transformer in which part of the winding is common to both primary
and secondary circuits, leading to increased efficiency, smaller size, and a higher degree of
voltage regulation.[89][90]
Capacitor voltage transformer: Transformer in which capacitor divider is used to
reduce high voltage before application to the primary winding.
Distribution transformer, power transformer: International standards make a
distinction in terms of distribution transformers being used to distribute energy from
transmission lines and networks for local consumption and power transformers being used to
transfer electric energy between the generator and distribution primary circuits.[89][91][q]
Phase angle regulating transformer: A specialised transformer used to control the flow
of real power on three-phase electricity transmission networks.
Scott-T transformer: Transformer used for phase transformation from three-phase
to two-phase and vice versa.](https://image.slidesharecdn.com/jaideepnewbhelproject-180331092607/85/BHEL-PROJECT-REPORT-TRAINING-REPORT-37-320.jpg)
![38
Polyphase transformer: Any transformer with more than one phase.
Grounding transformer: Transformer used for grounding three-phase circuits to create
a neutral in a three wire system, using a wye-delta transformer, or more commonly, a zigzag
grounding winding.
Leakage transformer: Transformer that has loosely coupled windings.
Resonant transformer: Transformer that uses resonance to generate a high secondary
voltage.
Audio transformer: Transformer used in audio equipment.
Output transformer: Transformer used to match the output of a valve amplifier to its
load.
Instrument transformer: Potential or current transformer used to accurately and safely
represent voltage, current or phase position of high voltage or high power circuits.
Pulse transformer: Specialized small-signal transformer used to transmit digital
signaling while providing electrical isolation, commonly used in Ethernet computer networks
as 10BASE-T, 100BASE-T and 1000BASE-T.
Applications
Transformer at the Limestone Generating Station in Manitoba, Canada
Transformers are used to increase (or step-up) voltage before transmitting electrical energy
over long distances through wires. Wires have resistance which loses energy through joule
heating at a rate corresponding to square of the current. By transforming power to a higher
voltage transformers enable economical transmission of power and distribution.
Consequently, transformers have shaped the electricity supply industry, permitting
generation to be located remotely from points of demand.[94]
All but a tiny fraction of the
world's electrical power has passed through a series of transformers by the time it reaches the
consumer.[44]](https://image.slidesharecdn.com/jaideepnewbhelproject-180331092607/85/BHEL-PROJECT-REPORT-TRAINING-REPORT-38-320.jpg)
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Similar to BHEL PROJECT REPORT ( TRAINING REPORT )
BHEL PROJECT REPORT ( TRAINING REPORT )
- 1. A TRAINING REPORTOF VOCATIONAL TRAINING AT Bharat Heavy Electricals Limited, Bhopal BHABHA ENGINEERING RESEARCH INSTITUTE, BHOPAL DEPARTMENT OF MECHANICAL ENGINEERING SUBMITTED BY: SUBMITTED TO:
- 2. 2 INDEX :- CONTENTS PAGENO. Declaration 3 Certificate 4 Acknowledgement 5 BHEL OVERVIEW 6-10 INTRODUCTION BUSSINESS SECTOR INDUSTRY SECTOR R&D HUMAN RESOURCEDEVELOPMENT BHEL BHOPAL PROFILE 11 - 13 PRODUCT TECHNICAL COLLABORATION MAJOR CUSTOMEROF BHEL FOUNDRY 14 - 20 WATER AND STEAMTURBINE 21 – 30 TRANSFORMER 31 -39 TRACTION MOTORS 40 - 41 CONCLUSION 42
- 3. 3 DECLARATION I hereby declarethat the work, which is being presented in this training report submitted to BHARAT HEAVY ELECTRICALS LIMITED, Bhopal as part of curriculum is an authentic record of my own work, carried within the premises of Bharat Heavy Electricals Limited, Bhopal. DATE:– 30/08/2017 PLACE:- BHOPAL
- 4. 4 CERTIFICATE This is tocertify that the vocational project training report which has been submitted to B.H.E.L BHOPAL as part of the curriculum by your name of Mechanical Engineering Department, BHABHA ENGINEERING RESEARCH INSTITUTE, BHOPAL is a record of authentic work carried out by his under my supervision and guidance to the best of our knowledge. PROJECT GUIDE: –
- 5. 5 ACKNOWLEDGEMENT I am extremelygrateful to Bharat Heavy Electricals Limited, Bhopal, for giving me the opportunity to carry out my vocational training at their facility. Special thanks to Mr……….. Dy. ………(P) C.I.M. DIVISION for his continuous support and guidance in being my mentor. And last but not the least, I would also like to extend my gratefulness to all the supervisors and technicians, right from the highest to the simplest, for their constant and enthusiasing support.
- 6. 6 BHELOVERVIEW INTRODUCTION Bharat Heavy ElectricalsLtd. (BHEL) is the largest engineering and manufacturing enterprise of its kind in India and is one of the leading international companies in the field of power equipment manufacture. The first plant of BHEL, set up at Bhopal in 1956, signaled the dawn of the Heavy Electrical Industry in India. In the sixties, three more major plants were set up at Haridwar, Hyderabad and Tiruchirapalli that form the core of the diversified product range, systems and services that BHEL offers today. BHEL’s range of services extends from project feasibility studies to after- sales- service, successfully meeting diverse needs through turnkey capability. The company has 14 manufacturing units, 4 power sector regions, 8 service centers and 15 regional offices, besides project sites spread all over India and abroad. BHEL has a well recognized track record of performance, making profits continuously since 1971-72 and paying dividends since 1976-77. BHEL manufactures over 180 products under 30 major product groups and caters to core sectors of the Indian economy viz., Power Generation and Transmission, Industry, Transportation, Renewable Energy etc. The quality and reliability of its products is due to the emphasis on design, engineering and manufacturing to international standards by acquiring and adapting some of the best technologies from leading companies in the world, together with technologies developed in its own R&D centers. The Company has been constantly adapting itself to face the challenges thrown-up by the business environment. BHEL has committed to support the Global Compact & the set of core values enshrined in its ten principles in the areas of human rights, labour standards and environment.
- 7. 7 BUSINESS SECTORS BHEL’s operationsare organised around three business sectors, namely Power, Industry including Transmission, Transportation & Renewable Energy, and International Operations. This enables BHEL to have a strong customer orientation and respond quickly to the changes in the market. POWER SECTOR Power is the focal area for BHEL and comprises thermal, nuclear, gas, diesel and hydro businesses. BHEL has taken India from a position of total dependence on overseas sources to complete self-reliance in power plant equipment. Today, BHEL sets account for nearly 65% of the total installed power generating capacity in the country. Significantly these sets contribute 73% of the total power generated in the country. BHEL has contracted for boilers and auxiliaries, turbo generator sets and associated controls, piping and station, corporate profile 1,000 MW Simhadri STPS set up by BHEL on turnkey basis in 45 months, control & instrumentation of up to 500 MW unit rating and has the technology and capability to produce thermal sets of higher unit ratings including 1000 MW. BHEL has access to technology for higher size gas turbines and can supply gas turbines of up to 279 MW unit size. It engineers and constructs custom built combined cycle power plants. Hydro sets of Francis, Pelton, Kaplan and Bulb types for different head - discharge combinations, with matching generators, are also designed and manufactured by BHEL . INDUSTRY SECTOR INDUSTRIES BHEL manufactures and supplies major capital equipment and systems like captive power plants, centrifugal compressors, drive turbines, industrial boilers and auxiliaries, waste heat recovery boilers, gas turbines, pumps, heat exchangers, electric machines, valves, heavy castings and forgings, electrostatic precipitators, ID/FD fans, seamless pipes etc. These serve a number of industries like metallurgical, mining, cement, paper, fertilizers, refineries and petro-chemicals, etc. in addition to power utilities. BHEL has also emerged as a major supplier of controls and instrumentation systems, especially distributed digital control systems for various power plants and industries.
- 8. 8 OIL & GAS BHELhas the capability to supply complete onshore drilling rigs, super deep drilling rigs, desert rigs, mobile rigs, workover rigs and sub sea well heads. It supplies equipment / sub- assemblies for onshore drilling rigs viz. drawworks, rotary-table, travelling block, swivel, mast & sub structure, mud systems and rig electrics. BHEL also supplies X’mas tree valves & well heads up to a rating of 10,000 psi for onshore / offshore service and Casing Support System, Mudline Suspension System & Block Valves for offshore applications. TRANSMISSION BHEL supplies a wide range of products and systems for transmission & distribution applications. The products manufactured by BHEL include power transformers, instrument transformers, dry type transformers, shunt reactors, capacitors, vacuum and SF6 switchgear, gas insulated switchgear, ceramic insulators, etc. BHEL has developed and commercialized the country’s first indigenous 36 kV Gas Insulated Substation (GIS) and has also bagged first order for its indigenously developed 145 kV GIS. For enhancing the power transfer capability and reducing transmission losses in 400 kV lines, BHEL has indigenously developed and executed fixed series compensation schemes and has developed thyristor controlled series compensation scheme, involving thyristor controlled reactors, popularly known as Flexible AC Transmission System (FACTS). BHEL has indigenously developed state of the art controlled shunt reactor for reactive power management of long transmission lines. With a strong engineering base, the company undertakes turnkey execution of substations upto 400 kV and has capability to execute 765 kV substations. High Voltage Direct Current (HVDC) systems have been supplied for economic transmission of bulk power over long distances. During the year, BHEL successfully bagged another order for installation of Balia-Bhiwadi HVDC link of 2500 MW capacity. TRANSPORTATION Most of the trains in the Indian Railways, whether electric or diesel powered, are equipped with BHEL’s traction propulsion systems and controls. The systems supplied are both with conventional DC drives and state of the art AC drives. India’s first underground metro at Kolkata runs on drives and controls supplied by BHEL. The company also manufactures complete rolling stock i.e. electric locomotives up to 5000 HP, diesel electric locomotives from 350 HP to 3100 HP for both mainline and shunting 12 MMEC ,MULLANA duty applications. Further, BHEL undertakes retrofitting and overhauling of rolling stock. In the area of Urban transportation, BHEL is geared up for turnkey execution of electric trolley bus
- 9. 9 systems, light railsystems and metro systems. BHEL is contributing to the supply of electric systems for EMUs for 1500V DC & 25 kV AC to Indian Railways. Almost all the EMUs in service are with electrics manufactured and supplied by BHEL. The company has also diversified into the area of track maintenance machines. BHEL is well poised to meet the emerging requirements of Indian Railways for higher horsepower locos for freight and passenger applications. RENEWABLE ENERGY BHEL has been manufacturing & supplying various Renewable Energy systems and products. It includes Solar Energy systems namely PV modules, PV power plants, solar lanterns, street lighting, solar pumps and solar water heating systems. The Wind power generation business based on higher rating WEGs is being explored. INTERNATIONAL OPERATIONS BHEL has over the years established its references in 68 countries of the world spanning across all the six-inhabited continents. These references encompass almost the entire range of BHEL products and services covering turnkey Power projects of Thermal, Hydro and Gas-based, Transmission Substation projects, Rehabilitation projects for Boilers, Power Stations etc., besides a wide variety of products, like Transformers, Reactors, Compressors, Valves and Oil field equipment, Electrostatic Precipitators, Photo Voltaic equipments, Insulators, Switchgears, Heat Exchangers, Castings & Forgings . Some of the major successes achieved by BHEL have been in Gas based power projects in Oman, Saudi Arabia, Iraq, Libya, Bangladesh, Malaysia, Sri Lanka, China, Kazakhstan; Thermal 13 MMEC ,MULLANA power projects in Cyprus, Malta, Egypt, Malaysia, Sudan, Indonesia, Thailand; Hydro power plants in New Zealand, Azerbaijan, Bhutan, Nepal, Taiwan, Malaysia, Afghanistan, Tajikistan and Substation Projects & equipment in various countries of Africa, Europe, South & South East Asia. The company is taking a number of strategic business initiatives to fuel further growth in overseas business. RESEARCH & DEVELOPMENT The Corporate R&D Division at Hyderabad leads BHEL’s research and development efforts, suitably supported by Engineering and R&D groups at the manufacturing divisions. BHEL’s technology policy promotes a judicious mix of indigenous efforts and selective collaboration in essential areas. The company continuously upgrades its technology and products to contemporary standards. BHEL is one of the few companies worldwide involved in the development of Integrated Gasification Combined Cycle (IGCC) technology which will usher it in clean coal technology. BHEL has set up Asia’s first 6.2 MW IGCC power plant with a indigenously designed pressurisedfluidised bed gasifier. Presently, development efforts are underway to set up a 125 MW IGCC power plant.
- 10. 10 HUMAN RESOURCE DEVELOPMENT Thegreatest strength of BHEL is its highly skilled and committed manpower. Every employee is given an equal opportunity to develop himself and improve his position. Continuous training & retraining, career planning, a positive work culture and participative style of management have engendered development of a committed and motivated work force ready to take up the challenge of making BHEL a competitive world-class organization. As a process of linking HRM to market forces / stakeholder driven policies, an e-enabled Performance Management System has been established for executives - a new benchmark in promoting performance-led growth. To encourage individuals for capability building and for continuous improvement through creativity & innovation in every sphere of activity, an e-network based Improvement Projects Rewards Scheme’ (IMPRESS) has been introduced company wide.
- 11. 11 BHEL BHOPAL PROFILE HeavyElectrical Plant , Bhopal is the mother plant of Bharat Heavy Electricals Limited, the largest engineering and manufacturing enterprise in India in the energy-related and infrastructure sector, today. It is located at about 7 kms. from Bhopal Railway station, about 5 kms.fromHabibganj Railway station and about 18 kms. From Raja Bhoj Airport. With technical assistance from Associated Electricals (India) Ltd., a UK based company, it came into existence on 29th of August, 1956. Pt. Jawaharlal Nehru, first Prime minister of India dedicated this plant to the nation on 6th of November, 1960. BHEL, Bhopal with state-of-the-art facilities, manufactures wide range of electrical equipments. It’s product range includes Hydro, Steam, Marine & Nuclear Turbines, Heat Exchangers, Hydro & Turbo Generators, Transformers, Switchgears,Control gears, Transportation Equipment, Capacitors, Bushings, Electrical Motors,Rectifiers, Oil Drilling Rig Equipments and Diesel Generating sets. BHEL, Bhopal certified to ISO: 9001, ISO 14001 and OHSAS 18001, ismoving towards excellence by adopting TQM as per EFQM / CII model of BusinessExcellence. Heat Exchanger Division is accredited with ASME ‘U’ Stamp. With theslogan of “ Kadamkadammilanahai, grahaksafal banana hai”, it is committed to thecustomers.BHEL Bhopal has its own Laboratories for material testing and instrumentcalibration which are accredited with ISO 17025 by NABL. The Hydro Laboratory,Ultra High Voltage laboratory and Centre for Electric Transportation are the onlylaboratories of its in this part oftheworld.BHEL Bhopal's strength is it's employees. The company continuouslyinvests in Human Resources and pays utmost attention to their needs. The plant'sTownship, well known for its greenery is spread over an area of around 20 sqkms.and provides all facilities to the residents like, parks, community halls, library,shopping centers, banks, post offices etc. Besides, free health services is extended toall the employees through 350 bedded (inclusive of 50 floating beds) KasturbaHospital and chain of dispensaries.
- 12. 12 PRODUCTS Thermal Power Plants ·Steam turbines, boilers and generators of up to 800 MW capacity for utility and combined- cycle applications ; Capacity to manufacture boilers and steam turbines with supercritical system cycle parameter and matching generator up to 1000 MW unit size. · Steam turbines, boilers and generators of CPP applications; capacity to manufacture condensing, extraction, back pressure, injection or any combination of these types of steam turbines. Nuclear Power Plants · Steam generator & Turbine generator up to 700 MW capacity Gas-Based Power Plants · Gas turbines of up to 280 MW (ISO) advance class rating. · Gas turbine-based co-generation and combined-cycle systems of industry and utility applications. There are other products given as follows Hydro Power Plants, DG Power Plants, Industrial Sets, Boiler, Boiler Auxiliaries, Piping System, Heat Exchangers and Pressure Vessels Pumps, Power Station Control Equipment, Switchgear, Bus Ducts, Transformers, Insulators, Industrial and Special Ceramics, Capacitors, Electrical Machines, Compressors, Control Gear, Silicon Rectifiers, Thyristor GTO/IGBT Equipment , Power Devices, Transportation Equipment Oil Field Equipment, Casting and Forgings, Seamless Steel Tubes, Distributed Power Generation and Small Hydro Plants.
- 13. 13 TECHNICAL COLLABORATIONS PRODUCT COLLABORATIONS #Thermal Sets, Hydro Sets, Motors & Control Gears. Prommashexport RUSSIA # Bypass & Pressure Reducing Systems Sulzer Brother Ltd. SWITZERLAND # Electronic Automation System for Steam Turbine & Generators Siemens AG. GERMANY # Francis Type Hydro Turbines General Electric CANADA # Moisture Separator Reheaters BalokeDuerr GERMANY # Christmas Trees & Conventional Well National Oil Well Head Assemblies, USA # Steam Turbines , Generators and Axial Condensers Siemens AG. GERMANY # Cam Shaft Controllers and Tractions Current Control Units Siemens AG. GERMANY MAJOR CUSTOMERS OF B.H.E.L Supplied to all major utilities in India :- NTPC PGCIL NJPC NHPC NLC NPCIL NEEPCO APTRANSCO APGENCO JPPCL ALL State Electricity Boards (SEBs) INDIAN RAILWAYS (IR)
- 14. 14 Foundry A foundry isa factory that produces metal castings. Metals are cast into shapes by melting them into a liquid, pouring the metal in a mold, and removing the mold material or casting after the metal has solidified as it cools. The most common metals processed are aluminium and cast iron. However, other metals, such as bronze, brass, steel, magnesium, and zinc, are also used to produce castings in foundries. In this process, parts of desired shapes and sizes can be formed. Process o Melting Furnace o Degassing o Mould making o Pouring o Shakeout o Degating o Heat treating o Surface cleaning o Finishing Process Casting (metalworking) In metalworking, casting involves pouring liquid metal into a mold, which contains a hollow cavity of the desired shape, and then allowing it to cool and solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process. Casting is most often used for making complex shapes that would be difficult or uneconomical to make by other methods
- 15. 15 Melting Fig.Melting metal ina crucible for casting Fig.A metal die casting robot in an industrial foundry Melting is performed in a furnace. Virgin material, external scrap, internal scrap, and alloying elements are used to charge the furnace. Virgin material refers to commercially pure forms of the primary metal used to form a particular alloy. Alloying elements are either pure forms of an alloying element, like electrolytic nickel, or alloys of limited composition, such as ferroalloys or master alloys. External scrap is material from other forming processes such as punching, forging, or machining. Internal scrap consists of gates, risers, defective castings, and other extraneous metal oddments produced within the facility. The process includes melting the charge, refining the melt, adjusting the melt chemistry and tapping into a transport vessel. Refining is done to remove deleterious gases and elements from the molten metal to avoid casting defects. Material is added during the melting process to bring the final chemistry within a specific range specified by industry and/or internal standards. Certain fluxes may be used to separate the metal from slag and/or dross and degassers are used to remove dissolved gas from metals that readily dissolve certain gasses. During the tap, final chemistry adjustments are made.
- 16. 16 Furnace Several specialised furnacesare used to heat the metal. Furnaces are refractory-lined vessels that contain the material to be melted and provide the energy to melt it. Modern furnace types include electric arc furnaces (EAF), induction furnaces, cupolas, reverberatory, and crucible furnaces. Furnace choice is dependent on the alloy system quantities produced. For ferrous materials EAFs, cupolas, and induction furnaces are commonly used. Reverberatory and crucible furnaces are common for producing aluminium, bronze, and brass castings. Furnace design is a complex process, and the design can be optimized based on multiple factors. Furnaces in foundries can be any size, ranging from small ones used to melt precious metals to furnaces weighing several tons, designed to melt hundreds of pounds of scrap at one time. They are designed according to the type of metals that are to be melted. Furnaces must also be designed based on the fuel being used to produce the desired temperature. For low temperature melting point alloys, such as zinc or tin, melting furnaces may reach around 500°C. Electricity, propane, or natural gas are usually used to achieve these temperatures. For high melting point alloys such as steel or nickel-based alloys, the furnace must be designed for temperatures over 1600° C. The fuel used to reach these high temperatures can be electricity (as employed in electric arc furnaces) or coke. . Degassing Degassing is a process that may be required to reduce the amount of hydrogen present in a batch of molten metal. Gases can form in metal castings in one of two ways: 1. by physical entrapment during the casting process or 2. by chemical reaction in the cast material. Hydrogen is a common contaminant for most cast metals. It forms as a result of material reactions or from water vapor or machine lubricants. If the hydrogen concentration in the melt is too high, the resulting casting will be porous; the hydrogen will exit the molten solution, leaving minuscule air pockets, as the metal cools and solidifies. Porosity often seriously deteriorates the mechanical properties of the metal. An efficient way of removing hydrogen from the melt is to bubble a dry, insoluble gas through the melt by purging or agitation. When the bubbles go up in the melt, they catch the dissolved hydrogen and bring it to the surface. Chlorine, nitrogen, helium and argon are often used to degas non-ferrous metals. Carbon monoxide is typically used for iron and steel. There are various types of equipment that can measure the presence of hydrogen. Alternatively, the presence of hydrogen can be measured by determining the density of a metal sample. In cases where porosity still remains present after the degassing process, porosity sealing can be accomplished through a process called metal impregnating.
- 17. 17 Mould Making Diagrams oftwo pattern types Fig. Draft on a pattern A diagram of an undercut in a mold In the casting process a pattern is made in the shape of the desired part. Simple designs can be made in a single piece or solid pattern. More complex designs are made in two parts, called split patterns. A split pattern has a top or upper section, called a cope, and a bottom or lower section called a drag. Both solid and split patterns can have cores inserted to complete the final part shape. Cores are used to create hollow areas in the mold that would otherwise be impossible to achieve. Where the cope and drag separates is called the parting line. The pattern is made out of wax, wood, plastic, or metal. The molds are constructed by several different processes dependent upon the type of foundry, metal to be poured, quantity of parts to be produced, size of the casting, and complexity of the casting. These mold processes include: Sand casting — Green or resin bonded sand mold. Lost-foam casting — Polystyrene pattern with a mixture of ceramic and sand mold. Investment casting — Wax or similar sacrificial pattern with a ceramic mold. Ceramic mold casting — Plaster mold. V-process casting — Vacuum with thermoformed plastic to form sand molds. No moisture, clay or resin required. Die casting — Metal mold. Billet (ingot) casting — Simple mold for producing ingots of metal, normally for use in other foundries.
- 18. 18 Pouring Fig.Bronze poured froma crucible into a mold, using the lost-wax casting process In a foundry, molten metal is poured into molds. Pouring can be accomplished with gravity, or it may be assisted with a vacuum or pressurized gas. Many modern foundries use robots or automatic pouring machines to pour molten metal. Traditionally, molds were poured by hand using ladles. Shakeout The solidified metal component is then removed from its mold. Where the mold is sand based, this can be done by shaking or tumbling. This frees the casting from the sand, which is still attached to the metal runners and gates — which are the channels through which the molten metal traveled to reach the component itself. Degating Degating is the removal of the heads, runners, gates, and risers from the casting. Runners, gates, and risers may be removed using cutting torches, bandsaws, or ceramic cutoff blades. For some metal types, and with some gating system designs, the sprue, runners, and gates can be removed by breaking them away from the casting with a sledge hammer or specially designed knockout machinery. Risers must usually be removed using a cutting method (see above) but some newer methods of riser removal use knockoff machinery with special designs incorporated into the riser neck geometry that allow the riser to break off at the right place. The gating system required to produce castings in a mold yields leftover metal — including heads, risers, and sprue (sometimes collectively called sprue) — that can exceed 50% of the metal required to pour a full mold. Since this metal must be remelted as salvage, the yield of a particular gating configuration becomes an important economic consideration when designing various gating schemes, to minimize the cost of excess sprue, and thus overall melting costs.
- 19. 19 Heat treating Heat treatingis a group of industrial and metalworking processes used to alter the physical, and sometimes chemical, properties of a material. The most common application is metallurgical. Heat treatments are also used in the manufacture of many other materials, such as glass. Heat treatment involves the use of heating or chilling, normally to extreme temperatures, to achieve a desired result such as hardening or softening of a material. Heat treatment techniques include annealing, case hardening, precipitation strengthening, tempering, and quenching. It is noteworthy that while the term "heat treatment" applies only to processes where the heating and cooling are done for the specific purpose of altering properties intentionally, heating and cooling often occur incidentally during other manufacturing processes such as hot forming or welding. Surface cleaning After degating and heat treating, sand or other molding media may remain adhered to the casting. To remove any mold remnants, the surface is cleaned using a blasting process. This means a granular media will be propelled against the surface of the casting to mechanically knock away the adhering sand. The media may be blown with compressed air, or may be hurled using a shot wheel. The cleaning media strikes the casting surface at high velocity to dislodge the mold remnants (for example, sand, slag) from the casting surface. Numerous materials may be used to clean cast surfaces, including steel, iron, other metal alloys, aluminium oxides, glass beads, walnut shells, baking powder, and many others. The blasting media is selected to develop the color and reflectance of the cast surface. Terms used to describe this process include cleaning, bead blasting, and sand blasting. Shot peening may be used to further work-harden and finish the surface. Finishing Fig.Modern foundry (circa 2000)
- 20. 20 The final stepin the process of casting usually involves grinding, sanding, or machining the component in order to achieve the desired dimensional accuracies, physical shape, and surface finish. Removing the remaining gate material, called a gate stub, is usually done using a grinder or sander. These processes are used because their material removal rates are slow enough to control the amount of material being removed. These steps are done prior to any final machining. After grinding, any surfaces that require tight dimensional control are machined. Many castings are machined in CNC milling centers. The reason for this is that these processes have better dimensional capability and repeatability than many casting processes. However, it is not uncommon today for castings to be used without machining. A few foundries provide other services before shipping cast products to their customers. It is common to paint castings to prevent corrosion and improve visual appeal. Some foundries assemble castings into complete machines or sub-assemblies. Other foundries weld multiple castings or wrought metals together to form a finished product.[3] More and more, finishing processes are being performed by robotic machines, which eliminate the need for a human to physically grind or break parting lines, gating material, or feeders. Machines can reduce risk of injury to workers and lower costs for consumables — while also increasing productivity. They also limit the potential for human error and increase repeatability in the quality of grinding Fig. Flowchart of a typical Foundary process
- 21. 21 WATER TURBINE SECTION Awater turbine is a rotary engine that takes energy from moving water.Water turbines were developed in the nineteenth century and were widely used for industrial power prior to electrical grids. Now they are mostly used for electric power generation. They harness a clean and renewable energy source. Water Turbine Manufacturing Block BHEL BHOPAL A leading engineering enterprise which supplies all types of equipment for hydro powergeneration. A leading turbine manufacturer offering a wide range of Hydro Turbine, Valves, Governors, Turbine and Station Auxiliary systems, Balance of plants for Hydro Power Station and related Services. Installed manufacturing capacity:2500 MW/annum.Two units manufacturing hydro turbines.In the market for more than three decades.Dedicated shop area of over 100000 sq. meters. Ultramodern model development and testing facilities.Sophisticated CAD/CAM facilities.ISO 9001 Certification.ASME "Q" stamp for fabrication facilities. WTM Block is Sub divided into 5 division 1. Bay -1 2. Bay- 2 3. Bay- ¾ 4. Assembly 5. .Gov. Assembly Product Manufacter in BhelBopal Pelton, Francis, Kaplan, Propeller, Bulb, Tubular Turbines from 2 MW to 300 MW,Butterfly and Spherical type shutoff Valves, Pressure Relief Valves, DischargeRegulators, Associated auxiliaries and station equipment. Matching HydroGenerators for the above turbines. Reversible Pump Turbines, Generators, Motors with associated Control, ExcitationEquipment, Auxiliaries and Station Equipments. Digital (Micro processor based), Compact /Analog, Electro Hydraulic Governors forPower Stations. Oil pressure system of 20 to 100 bar for the above. Standardized Micro Hydro sets of Tubular and Bulb type with output ranging from100 kw to 2 MW sets along with matching generator, compact Governor for smallHydro-sets, speed increasing gear unit Excitation Equipment, Associated Auxiliariesand Station Equipment. Renovation, uprating and modernization of Hydro equipment, execution of EPC/ turnkey contracts including civil works. THEORY OF OPERATION
- 22. 22 Flowing water isdirected on to the blades of a turbine runner, creating a force on the blades. Since the runner is spinning, the force acts through a distance (force acting through a distance is the definition of work). In this way, energy is transferred from the water flow to the turbine. Water turbines are divided into two groups; reaction turbines and impulse turbines. Reaction turbines Reaction turbines are acted on by water, which changes pressure as it moves through the turbine and gives up its energy. They must be encased to contain the water pressure (or suction), or they must be fully submerged in the water flow. Impulse turbines Impulse turbines change the velocity of a water jet. The jet pushes the turbine's curved blades which reverse the flow. The resulting change in momentum (impulse) causes a force on the turbine blades. Since the turbine is spinning, the force acts through a distance (work) and the diverted water flow is left with diminished energy. TYPES OF TURBINES Reaction turbines: Francis Kaplan, Propeller, Bulb, Tube, Straflo Tyson Water wheel Impulse turbines: Pelton Turgo Michell-Banki (also known as the Crossflow or Ossberger turbine) DESIGN AND APPLICATION Turbine selection is based mostly on the available water head, and less so on the available flow rate. In general, impulse turbines are used for high head sites, and reaction turbines are used for low head sites. Kaplan turbines are well-adapted to wide ranges of flow or head conditions, since their peak efficiency can be achieved over a wide range of flow conditions. .Typical range of heads
- 23. 23 Kaplan 2< H < 40 (H = head in meters) Francis 10 < H < 350 Pelton 50 < H < 1300 Turgo 50 < H < 250 A VISIT TO THE WORKSHOP Following work was going on during our visit Construction of FRANCIS TURBINE Maintenance of ROTOR of KAPLAN TURBINE And production of various other parts of turbine such as guide vanes, lever, top run, bottom run, butterfly valve etc. FRANCIS TURBINE The Francis turbine is a type of water turbine that was developed by James B. Francis in Lowell, Massachusetts It is an inward-flow reaction turbine that combines radial and axial flow concepts. Francis turbines are the most common water turbine in use today. They operate in a water head from 40 to 600 m (130 to 2,000 ft) and are primarily used for electrical power production. The electric generators which most often use this type of turbine have a power output which generally ranges just a few kilowatts up to 800 MW, though mini- hydro installations may be lower. Penstock (input pipes) diameters are between 3 and 33 feet (0.91 and 10.06 metres). The speed range of the turbine is from 75 to 1000 rpm. Wicket gates around the outside of the turbine's rotating runner control the rate of water flow through the turbine for different power production rates. Francis turbines are almost always mounted with the shaft vertical to isolate water from the generator. This also facilitates installation and maintenance.
- 24. 24 COMPONENTS A Francis turbineconsists of the following main parts: Spiral casing: The spiral casing around the runner of the turbine is known as the volute casing or scroll case. Throughout its length, it has numerous openings at regular intervals to allow the working fluid to impinge on the blades of the runner. These openings convert the pressure energy of the fluid into momentum energy just before the fluid impinges on the blades. This maintains a constant flow rate despite the fact that numerous openings have been provided for the fluid to enter the blades, as the cross-sectional area of this casing decreases uniformly along the circumference. Guide or stay vanes: The primary function of the guide or stay vanes is to convert the pressure energy of the fluid into the momentum energy. It also serves to direct the flow at design angles to the runner blades. Runner blades: Runner blades are the heart of any turbine. These are the centers where the fluid strikes and the tangential force of the impact causes the shaft of the turbine to rotate, producing torque. Close attention in design of blade angles at inlet and outlet is necessary, as these are major parameters affecting power production. Draft tube: The draft tube is a conduit which connects the runner exit to the tail race where the water is discharged from the turbine. Its primary function is to reduce the velocity of discharged water to minimize the loss of kinetic energy at the outlet. This permits the turbine to be set above the tail water without appreciable drop of available head. THEORY OF OPERATION The Francis turbine is a type of reaction turbine, a category of turbine in which the working fluid comes to the turbine under immense pressure and the energy is extracted by the turbine blades from the working fluid. A part of the energy is given up by the fluid because of pressure changes occurring in the blades of the turbine, quantified by the expression of Degree of reaction, while the remaining part of the energy is extracted by the volute casing of the turbine. At the exit, water acts on the spinning cup-shaped runner features, leaving at low velocity and low swirl with very little kinetic or potential energy left. The turbine's exit tube is shaped to help decelerate the water flow and recover the pressure. APPLICATION
- 25. 25 Francis Inlet Scroll,Grand Coulee Dam Small Swiss-made Francis turbine Francis turbines may be designed for a wide range of heads and flows. This, along with their high efficiency, has made them the most widely used turbine in the world. Francis type units cover a head range from 40 to 600 m (130 to 2,000 ft), and their connected generator output power varies from just a few kilowatts up to 800 MW.[2] Large Francis turbines are individually designed for each site to operate with the given water supply and water head at the highest possible efficiency, typically over 90%. KAPLAN TURBINE The Kaplan turbine is a propeller-type water turbine which has adjustable blades. It was developed in 1913 by Austrian professor Viktor Kaplan, who combined automatically adjusted propeller blades with automatically adjusted wicket gates to achieve efficiency over a wide range of flow and water level.
- 26. 26 DEVELOPMENT Viktor Kaplan livingin Brno, Czech Republic, obtained his first patent for an adjustable blade propeller turbine in 1912. But the development of a commercially successful machine would take another decade. Kaplan struggled with cavitation problems, and in 1922 abandoned his research for health reasons. THEORY OF APPLICATION The Kaplan turbine is an outward flow reaction turbine, which means that the working fluid changes pressure as it moves through the turbine and gives up its energy. Power is recovered from both the hydrostatic head and from the kinetic energy of the flowing water. The design combines features of radial and axial turbines.The inlet is a scroll-shaped tube that wraps around the turbine's wicket gate. Water is directed tangentially through the wicket gate and spirals on to a propeller shaped runner, causing it to spin. The outlet is a specially shaped draft tube that helps decelerate the water and recover kinetic energy.The turbine does not need to be at the lowest point of water flow as long as the draft tube remains full of water. A higher turbine location, however, increases the suction that is imparted on the turbine blades by the draft tube. The resulting pressure drop may lead to cavitation. APPLICATION Kaplan turbines are widely used throughout the world for electrical power production. They cover the lowest head hydro sites and are especially suited for high flow conditions.Inexpensive micro turbines on the Kaplan turbine model are manufactured for individual power production designed for 3 m of head which can work with as little as 0.3 m of head at a highly reduced performance provided sufficient water flow.Large Kaplan turbines are individually designed for each site to operate at the highest possible efficiency, typically over 90%. They are very expensive to design, manufacture and install, but operate for decades.
- 27. 27 STEAM TURBINE SECTION Asteam 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. MANUFACTURING The present-day manufacturing industry for steam turbines is dominated by Chinese power equipment makers. Harbin Electric, Shanghai Electric, and Dongfang Electric, the top three power equipment makers in China, collectively hold a majority stake in the worldwide market share for steam turbines in 2009-10 according to Platts.[13] Other manufacturers with minor market share include Bhel, Siemens, Alstom, GE, Doosan Škoda Power, Mitsubishi Heavy Industries, and Toshiba.[13] The consulting firm Frost & Sullivan projects that manufacturing of steam turbines will become more consolidated by 2020 as Chinese power manufacturers win increasing business outside of China. TYPES Steam turbines are made in a variety of sizes ranging from small <0.75 kW (<1 hp) units (rare) used as mechanical drives for pumps, compressors and other shaft driven equipment, to 1 500 000 kW (1.5 GW; 2 000 000 hp) turbines used to generate electricity. There are several classifications for modern steam turbines. Blade and stage design Schematic diagram outlining the difference between an impulse and a 50% reaction turbine
- 28. 28 Turbine blades areof two basic types, blades and nozzles. Blades move entirely due to the impact of steam on them and their profiles do not converge. This results in a steam velocity drop and essentially no pressure drop as steam moves through the blades. A turbine composed of blades alternating with fixed nozzles is called an impulse turbine, Curtis turbine, Rateau turbine, or Brown-Curtis turbine. Nozzles appear similar to blades, but their profiles converge near the exit. This results in a steam pressure drop and velocity increase as steam moves through the nozzles. Nozzles move due to both the impact of steam on them and the reaction due to the high-velocity steam at the exit. A turbine composed of moving nozzles alternating with fixed nozzles is called a reaction turbine or Parsons turbine.Multiple reaction stages divide the pressure drop between the steam inlet and exhaust into numerous small drops, resulting in a pressure-compounded turbine. Impulse stages may be either pressure-compounded, velocity-compounded, or pressure-velocity compounded. A pressure- compounded impulse stage is a row of fixed nozzles followed by a row of moving blades, with multiple stages for compounding. This is also known as a Rateau turbine, after its inventor. A velocity-compounded impulse stage (invented by Curtis and also called a "Curtis wheel") is a row of fixed nozzles followed by two or more rows of moving blades alternating with rows of fixed blades. This divides the velocity drop across the stage into several smaller drops.] A series of velocity-compounded impulse stages is called a pressure- velocity compounded turbine. Blade Design Challenges A major challenge facing turbine design is reducing the creep experienced by the blades. Because of the high temperatures and high stresses of operation, steam turbine materials become damaged through these mechanisms. As temperatures are increased in an effort to improve turbine efficiency, creep becomes more significant. To limit creep, thermal coatings and superalloys with solid-solution strengthening and grain boundary strengthening are used in blade designs. Refractory elements such as rhenium and ruthenium can be added to the alloy to improve creep strength. The addition of these elements reduces the diffusion of the gamma prime phase, thus preserving the fatigue resistance, strength, and creep resistance. Steam supply and exhaust conditions These types include condensing, non-condensing, reheat, extraction and induction. Condensing turbines are most commonly found in electrical power plants. These turbines receive steam from a boiler and exhaust it to a condenser. The exhausted steam is at a pressure well below atmospheric, and is in a partially condensed state, typically of a quality near 90%. Reheat turbines are also used almost exclusively in electrical power plants. In a reheat turbine, steam flow exits from a high-pressure section of the turbine and is returned to the boiler where additional superheat is added. The steam then goes back into an intermediate pressure section of the turbine and continues its expansion
- 29. 29 Casing or shaftarrangements These arrangements include single casing, tandem compound and cross compound turbines. Single casing units are the most basic style where a single casing and shaft are coupled to a generator. Tandem compound are used where two or more casings are directly coupled together to drive a single generator. A cross compound turbine arrangement features two or more shafts not in line driving two or more generators that often operate at different speeds. A cross compound turbine is typically used for many large applications. A typical 1930s- 1960s naval installation is illustrated below; this shows high- and low-pressure turbines driving a common reduction gear, with a geared cruising turbine on one high-pressure turbine. Starboard steam turbine machinery arrangement of Japanese Furutaka- and Aoba-class cruisers Two-flow rotors A two-flow turbine rotor. The steam enters in the middle of the shaft, and exits at each end, balancing the axial force. The moving steam imparts both a tangential and axial thrust on the turbine shaft, but the axial thrust in a simple turbine is unopposed. To maintain the correct rotor position and balancing, this force must be counteracted by an opposing force. Thrust bearings can be used for the shaft bearings, the rotor can use dummy pistons, it can be double flow- the steam enters in the middle of the shaft and exits at both ends, or a combination of any of these. In a double flow rotor, the blades in each half face opposite ways, so that the axial forces negate each other but the tangential forces act together. This design of rotor is also
- 30. 30 called two-flow, double-axial-flow,or double-exhaust. This arrangement is common in low-pressure casings of a compound turbine. PRINCIPLE OF DESIGN AND OPERATION An ideal steam turbine is considered to be an isentropic process, or constant entropy process, in which the entropy of the steam entering the turbine is equal to the entropy of the steam leaving the turbine. No steam turbine is truly isentropic, however, with typical isentropic efficiencies ranging from 20–90% based on the application of the turbine. The interior of a turbine comprises several sets of blades or buckets. 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. 31 TRANSFORMER- A transformer isan electrical device that transfers electrical energy between two or more circuits through electromagneticinduction. Electromagnetic induction produces an electromotiveforce within a conductor which is exposed to time varying magnetic fields. Transformers are used to increase or decrease the alternating voltages in electric power applications. Basic principles Ideal transformer For simplification or approximation purposes, it is very common to analyze the transformer as an ideal transformer model as presented in the two images. An ideal transformer is a theoretical, linear transformer that is lossless and perfectly coupled; that is, there are no energy losses and flux is completely confined within the magnetic core. Perfect coupling implies infinitely high core magnetic permeability and winding inductances and zero net magneto motive force Ideal transformer connected with source VP on primary and load impedance ZL on secondary, where 0 < ZL < ∞. A varying current in the transformer's primary winding creates a varying magnetic flux in the core and a varying magnetic field impinging on the secondary winding. This varying magnetic field at the secondary induces a varying electromotiveforce (EMF) or voltage in the secondary winding. The primary and secondary windings are wrapped around a core of infinitely high magnetic permeability so that all of the magnetic flux passes through both the primary and secondary windings. With a voltagesource connected to the primary winding and load impedance connected to the secondary winding, the transformer currents flow in the indicated directions. Real transformer
- 32. 32 Deviations from ideal Theideal transformer model neglects the following basic linear aspects in real transformers. Core losses, collectively called magnetizing current losses, consist of Hysteresis losses due to nonlinear application of the voltage applied in the transformer core, and Eddy current losses due to joule heating in the core that are proportional to the square of the transformer's applied voltage. Whereas windings in the ideal model have no resistances and infinite inductances, the windings in a real transformer have finite non-zero resistances and inductances associated with: Joule losses due to resistance in the primary and secondary windings Leakage flux that escapes from the core and passes through one winding only resulting in primary and secondary reactive impedance. a Leakage flux The ideal transformer model assumes that all flux generated by the primary winding links all the turns of every winding, including itself. In practice, some flux traverses paths that take it outside the windings.[24] Such flux is termed leakage flux, and results in leakage inductance in series with the mutually coupled transformer windings.[10] Leakage flux results in energy being alternately stored in and discharged from the magnetic fields with each cycle of the power supply. It is not directly a power loss, but results in inferior voltage regulation, causing the secondary voltage not to be directly proportional to the primary voltage, particularly under heavy load.[24] Transformers are therefore normally designed to have very low leakage inductance. Equivalent circuit Referring to the diagram, a practical transformer's physical behavior may be represented by an equivalent circuit model, which can incorporate an ideal transformer.
- 33. 33 Winding joule lossesand leakage reactances are represented by the following series loop impedances of the model: Primary winding: RP, XP Secondary winding: RS, XS. In normal course of circuit equivalence transformation, RS and XS are in practice usually referred to the primary side by multiplying these impedances by the turns ratio squared, (NP/NS) 2 = a2 . Real transformer equivalent circuit Core loss and reactance is represented by the following shunt leg impedances of the model: Core or iron losses: RC Magnetizing reactance: XM. RC and XM are collectively termed the magnetizing branch of the model. Basic transformer parameters and construction Effect of frequency Transformer universal EMF equation If the flux in the core is purely sinusoidal, the relationship for either winding between its rms voltage Erms of the winding, and the supply frequency f, number of turns N, core cross-sectional area a in m2 and peak magnetic flux density Bpeak in Wb/m2 or T (tesla) is given by the universal EMF equation. If the flux does not contain even harmonics the following equation can be used for half-cycle average voltage Eavg of any waveshape: By Faraday's Law of induction shown in eq. (1) and (2), transformer EMFs vary according to the derivative of flux with respect to time. The ideal transformer's core behaves linearly with time for any non-zero frequency. Flux in a real transformer's core behaves non-linearly in relation to magnetization current as the instantaneous flux increases beyond a finite linear
- 34. 34 range resulting inmagnetic saturation associated with increasingly large magnetizing current, which eventually leads to transformer overheating. Energy losses Real transformer energy losses are dominated by winding resistance joule and core losses. Transformers' efficiency tends to improve with increasing transformer capacity. The efficiency of typical distribution transformers is between about 98 and 99 percent. Winding joule losses Current flowing through a winding's conductor causes joule heating. As frequency increases, skin effect and proximity effect causes the winding's resistance and, hence, losses to increase. Eddy current losses Ferromagnetic materials are also good conductors and a core made from such a material also constitutes a single short-circuited turn throughout its entire length. Eddy currents therefore circulate within the core in a plane normal to the flux, and are responsible for resistive heating of the core material. The eddy current loss is a complex function of the square of supply frequency and inverse square of the material thickness. Eddy current losses can be reduced by making the core of a stack of plates electrically insulated from each other, rather than a solid block; all transformers operating at low frequencies use laminated or similar cores. Stray losses Leakage inductance is by itself largely lossless, since energy supplied to its magnetic fields is returned to the supply with the next half-cycle. However, any leakage flux that intercepts nearby conductive materials such as the transformer's support structure will give rise to eddy currents and be converted to heat. There are also radiative losses due to the oscillating magnetic field but these are usually small. Mechanical vibration and audible noise transmission In addition to magnetostriction, the alternating magnetic field causes fluctuating forces between the primary and secondary windings. This energy incites vibration transmission in interconnected metalwork, thus amplifying audible transformer hum. Construction Core Laminated steel cores
- 35. 35 Transformers for useat power or audio frequencies typically have cores made of high permeability silicon steel. The steel has a permeability many times that of free space and the core thus serves to greatly reduce the magnetizing current and confine the flux to a path which closely couples the windings.Early transformer developers soon realized that cores constructed from solid iron resulted in prohibitive eddy current losses, and their designs mitigated this effect with cores consisting of bundles of insulated iron wires. Later designs constructed the core by stacking layers of thin steel laminations, a principle that has remained in use. Each lamination is insulated from its neighbors by a thin non-conducting layer of insulation. The universal transformer Solid cores Powdered iron cores are used in circuits such as switch-mode power supplies that operate above mains frequencies and up to a few tens of kilohertz. These materials combine high magnetic permeability with high bulk electrical resistivity. For frequencies extending beyond the VHF band, cores made from non-conductive magnetic ceramic materials called ferrites are common.Some radio-frequency transformers also have movable cores (sometimes called 'slugs') which allow adjustment of the coupling coefficient (and bandwidth) of tuned radio-frequency circuits. Air cores A physical core is not an absolute requisite and a functioning transformer can be produced simply by placing the windings near each other, an arrangement termed an 'air-core' transformer. The air which comprises the magnetic circuit is essentially lossless, and so an air-core transformer eliminates loss due to hysteresis in the core material.[10] The leakage inductance is inevitably high, resulting in very poor regulation, and so such designs are unsuitable for use in power distribution.They have however very high bandwidth, and are frequently employed in radio-frequency applications, for which a satisfactory coupling coefficient is maintained by carefully overlapping the primary and secondary windings. They're also used for resonant transformers such as Tesla coils where they can achieve reasonably low loss in spite of the high leakage inductance.
- 36. 36 Windings The conducting materialused for the windings depends upon the application, but in all cases the individual turns must be electrically insulated from each other to ensure that the current travels throughout every turn.[62] For small power and signal transformers, in which currents are low and the potential difference between adjacent turns is small, the coils are often wound from enamelled magnet wire, such as Formvar wire. Larger power transformers operating at high voltages may be wound with copper rectangular strip conductors insulated by oil- impregnated paper and blocks of pressboard. Cooling Cutaway view of liquid-immersed construction transformer. The conservator (reservoir) at top provides liquid-to-atmosphere isolation as coolant level and temperature changes. The walls and fins provide required heat dissipation balance. See also: Arrhenius equation To place the cooling problem in perspective, the accepted rule of thumb is that the life expectancy of insulation in all electrics, including all transformers, is halved for about every 7 °C to 10 °C increase in operating temperature, this life expectancy halving rule holding more narrowly when the increase is between about 7 °C to 8 °C in the case of transformer winding cellulose insulation. Small dry-type and liquid-immersed transformers are often self-cooled by natural convection and radiation heat dissipation. As power ratings increase, transformers are often cooled by forced-air cooling, forced-oil cooling, water-cooling, or combinations of these.Large transformers are filled with transformer oil that both cools and insulates the windings. Transformer oil is a highly refined mineral oil that cools the windings and insulation by circulating within the transformer tank. The mineral oil and paper insulation system has been extensively studied and used for more than 100 years. Insulation drying Construction of oil-filled transformers requires that the insulation covering the windings be thoroughly dried of residual moisture before the oil is introduced. Drying is carried out at the factory, and may also be required as a field service. Drying may be done by circulating hot
- 37. 37 air around thecore, or by vapor-phase drying (VPD) where an evaporated solvent transfers heat by condensation on the coil and core. For small transformers, resistance heating by injection of current into the windings is used. The heating can be controlled very well, and it is energy efficient. The method is called low- frequency heating (LFH) since the current used is at a much lower frequency than that of the power grid, which is normally 50 or 60 Hz. A lower frequency reduces the effect of inductance, so the voltage required can be reduced. The LFH drying method is also used for service of older transformers. Bushings Larger transformers are provided with high-voltage insulated bushings made of polymers or porcelain. A large bushing can be a complex structure since it must provide careful control of the electric field gradient without letting the transformer leak oil.[84] Classification parameters Transformers can be classified in many ways, such as the following: Power capacity: From a fraction of a volt-ampere (VA) to over a thousand MVA. Duty of a transformer: Continuous, short-time, intermittent, periodic, varying. Frequency range: Power-frequency, audio-frequency, or radio-frequency. Voltage class: From a few volts to hundreds of kilovolts. Cooling type: Dry and liquid-immersed – self-cooled, forced air-cooled; liquid- immersed – forced oil-cooled, water-cooled. Types Various specific electrical application designs require a variety of transformer types. Although they all share the basic characteristic transformer principles, they are customize in construction or electrical properties for certain installation requirements or circuit conditions. Autotransformer: Transformer in which part of the winding is common to both primary and secondary circuits, leading to increased efficiency, smaller size, and a higher degree of voltage regulation.[89][90] Capacitor voltage transformer: Transformer in which capacitor divider is used to reduce high voltage before application to the primary winding. Distribution transformer, power transformer: International standards make a distinction in terms of distribution transformers being used to distribute energy from transmission lines and networks for local consumption and power transformers being used to transfer electric energy between the generator and distribution primary circuits.[89][91][q] Phase angle regulating transformer: A specialised transformer used to control the flow of real power on three-phase electricity transmission networks. Scott-T transformer: Transformer used for phase transformation from three-phase to two-phase and vice versa.
- 38. 38 Polyphase transformer:Any transformer with more than one phase. Grounding transformer: Transformer used for grounding three-phase circuits to create a neutral in a three wire system, using a wye-delta transformer, or more commonly, a zigzag grounding winding. Leakage transformer: Transformer that has loosely coupled windings. Resonant transformer: Transformer that uses resonance to generate a high secondary voltage. Audio transformer: Transformer used in audio equipment. Output transformer: Transformer used to match the output of a valve amplifier to its load. Instrument transformer: Potential or current transformer used to accurately and safely represent voltage, current or phase position of high voltage or high power circuits. Pulse transformer: Specialized small-signal transformer used to transmit digital signaling while providing electrical isolation, commonly used in Ethernet computer networks as 10BASE-T, 100BASE-T and 1000BASE-T. Applications Transformer at the Limestone Generating Station in Manitoba, Canada Transformers are used to increase (or step-up) voltage before transmitting electrical energy over long distances through wires. Wires have resistance which loses energy through joule heating at a rate corresponding to square of the current. By transforming power to a higher voltage transformers enable economical transmission of power and distribution. Consequently, transformers have shaped the electricity supply industry, permitting generation to be located remotely from points of demand.[94] All but a tiny fraction of the world's electrical power has passed through a series of transformers by the time it reaches the consumer.[44]
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- 40. 40 Traction motor A tractionmotor is an electric motor used for propulsion of a vehicle, such as an electric locomotive or electric roadway vehicle.Traction motors are used in electrically powered rail vehicles such as electric multiple units and other electric vehicles such as electric milk floats, elevators, conveyors, and trolleybuses, as well as vehicles with electrical transmission systems such as diesel-electric, electric hybrid vehicles, and battery electric vehicles. Motor types and control Direct-current motors with series field windings were the oldest type of traction motors. These provided a speed-torque characteristic useful for propulsion, providing high torque at lower speeds for acceleration of the vehicle, and declining torque as speed increased. By arranging the field winding with multiple taps, the speed characteristic could be varied, allowing relatively smooth operator control of acceleration. A further measure of control was provided by using pairs of motors on a vehicle; for slow operation or heavy loads, two motors could be run in series off the direct current supply. Where higher speed was desired, the motors could be operated in parallel, making a higher voltage available at each and so allowing higher speeds. Parts of a rail system might use different voltages, with higher voltages in long runs between stations and lower voltage near stations where slower operation would be useful. A variant of the DC system was the AC operated series motor, which is essentially the same device but operated on alternating current. Since both the armature and field current reverse at the same time, the behavior of the motor is similar to that when energized with direct current. To achieve better operating conditions, AC railways were often supplied with current at a lower frequency than the commercial supply used for general lighting and power; special traction current power stations were used, or rotary converters used to convert 50 or 60 Hz commercial power to the 16 2/3 Hz frequency used for AC traction motors. The AC system allowed efficient distribution of power down the length of a rail line, and also permitted speed control with switchgear on the vehicle. AC induction motors and synchronous motors are simple and low maintenance, but are awkward to apply for traction motors because of their fixed speed characteristic. An AC induction motor only generates useful amounts of power over a narrow speed range determined by its construction and the frequency of the AC power supply. The advent of power semiconductors has made it possible to fit a variable frequency drive on a locomotive; this allows a wide range of speeds, AC power transmission, and rugged induction motors without wearing parts like brushes and commutators.
- 41. 41 Transportation applications Road vehicles Traditionallyroad vehicles (cars, buses and trucks) have used diesel and petrol engines with a mechanical or hydraulic transmission system. In the latter part of the 20th century, vehicles with electrical transmission systems (powered from internal combustion engines, batteries or fuel cells) began to be developed—one advantage of using electric motors is that specific types can regenerate energy (i.e. act as a regenerative brake)—providing braking as well as increasing overall efficiency. Railways Swiss Rhaetian Railway Ge 6/6 I Krokodil locomotive, with a single large traction motor above each bogie, with drive by coupling rods.Traditionally, these were series-wound brushed DC motors, usually running on approximately 600 volts. The availability of high- powered semiconductors (such as thyristors and the IGBT) has now made practical the use of much simpler, higher-reliability AC induction motors known as asynchronous traction motors. Synchronous AC motors are also occasionally used, as in the French TGV.
- 42. 42 CONCLUSION VOCATIONAL TRANINIG ATBHEL BHOPAL PROVIDED ME PRACTICAL KNOWLEDGE OF WORKING OF INDUSTRY AND HELPED ME TO ENHANCE MY THEOROTICAL KNOWLEDGE WITH PRACTICAL APPLICATIONS IN INDUSTRY. THIS TRAINING HAS BEEN ONE OF THE MOST INTERESTING AND PRODUCTIVE EXPIRENCE IN MY LIFE. WE GAIN HERE INSIGHT INDUSTRIAL WORKING AND PRACTICE . I AM SURE THAT THE INDUSTRIAL TRAINING HAS ACHIEVED ITS PRIMARY OBJECTIVE AND RESULTS TO BUILD A CONFIDENT CARRER.