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8/8/2019 Trng Report

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VOCATIONAL TRAINING REPORT VI SEMESTER

SSG- PANJAB UNIVERSITY REGIONAL CENTRE

DEPARTMENT OF MECHNAICAL

ENGINEERING

Submitted By:MANISH KUMAR

SG7911

MECHANICAL ENGINEERING


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INTRODUCTION

BHEL is the largest engineering and manufacturing enterprise in India in the energyrelated/infrastructure sector, today. BHEL was established more than 40 years ago, ushering inthe indigenous Heavy Electrical Equipment industry in India - a dream that has been more than

realized with a well-recognized track record of performance. The company has been earningprofits continuously since 1971-72 and paying dividends since 1976 -77.

BHEL manufactures over 180 products under 30 major product groups and caters to core sectorsof the Indian Economy viz., Power Generation & Transmission, Industry, Transportation,Telecommunication, Renewable Energy, etc. The wide network of BHEL's 14 manu facturingdivisions, four Power Sector regional centres, over 100 project sites, eight service centres and 18regional offices, enables the Company to promptly serve its customers and provide them withsuitable products, systems and services -- efficiently and at competitive

prices. The high level of quality & reliability of its productsis due to the emphasis on design, engineering and

manufacturing to international standards by acquiringand adapting some of the best technologies from leadingcompanies in the world, together with technologiesdeveloped in its own R&D centres

BHEL has

Installed equipment for over 90,000 MW of powergeneration -- for Utilities, Captive and Industrial users.

Supplied over 2,25,000 MVA transformer capacity and other e quipment operating inTransmission & Distribution network up to 400 kV (AC & DC).

Supplied over 25,000 Motors with Drive Control System to Power projects, Petrochemicals,Refineries, Steel, Aluminium, Fertilizer, Cement plants, etc.

Supplied Traction electrics and AC/DC locos to power over 12,000 kms Railway network.

Supplied over one million Valves to Power Plants and other Industries.

BHEL's operations are organised around three business sectors, namely Power, Industry -including Transmission, Transportation, Telecommunication & Renewable Energy - andOverseas Business. This enables BHEL to have a strong customer orientation, to be sensitiveto his needs and respond quickly to the changes in the market.


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BHEL has divided into many blocks:-

1). Block-1:-

In block one turbo generator, generator, exciter motors (A.C&D.C) areManufactured & assembled

2). Block-2:-

In block two large size fabricated assemblies\component for power

equipment are manufactured & assembled

3) Block-3:-

In block -3 steam turbine, hydro turbines, and gas turbines, turbines blade

areManufactured & assembled.

4) Block-4:-

In block -4winding for turbo generator, hydro generator, insulation of

A.C&D.C Motors insulating component for turbo generator, hydro

generator motors are manufactured & assembled

5) Block-5:-

In block -5 fabricated parts of steam turbine water box, hydro turbine

turbines parts are manufactured & assembled.

6) Block-6:-

In block -6 fabricated oil tanks hollow guide blades, rings, stator frames

rotor Spiders are manufactured &assembled

7) Block-7:-

All types of dies including stamping dies, stamping for generators motors

are manufactured & assembled

8) Block-8:-

In block -8 LP heaters, ejectors, steam coolers, oil coolers, ACG coolers,

oil tanks are manufactured & assembled


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STEAM TURBINE TECHNOLOGY

Since the turn of the century, steam turbine generators have earned an enviable

reputation for economy and reliability in converting heat energy to electrical energy

under the most exacting service conditions.BHARAT HEAVY ELECTRICAL LTD. (BHEL)

provides engineering expertise and extensive laboratory facilities to meet the challenges

imposed in the design, assembly, and reliable operation of turbines of all sizes.

Capabilities include:

Nondestructive evaluationMaterials degradation studies

Remaininglife assessment

Structural integrity analysis

Failure analysis

Materials evaluation and testing

Field hardness testing and replication

Vibration problem diagnosis

Telemetry testing

TURBINE ROTORS

Critical turbine components must be evaluated to assure safe operation duringtheir lifetime. Acccurate life assessment procedures, coupled with a knowledge ofspecific rotor material properties, prevent costly premature retirement of rotors.

A wide range of finite element programs is used at BHEL to perform structuralevaluations and remaining life assessment, including:

ANSYS: Structural analysis NASTRAN: Structural analysis STRAP/SAFER: EPRI rotor integrity and life analysis BIGIF: EPRI fracture mechnics ADINA/ADINA-T: Structural/thermal analysis ABAQUS: Nonlinear structural analysis NESSUS: Probabilistic structural analysis


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PROJECT REPORT

ER code calculates steady state temperature (F)

for a high pressure (HP) rotor (top).state stress contours (psi) for an HP rotor are

ned using the SAFER finite element code (bottom).

Low pressure (LP) steam turbine disc cracking caused by stress corrosion is experiencedworldwide in rotors used in both nuclear and fossil fuel power plants. Cracking occurs in LProtor discs in keyways, in the blade attachment areas of the rims, on bore surfaces, and on websurfaces. Under a cooperative industry research project, funded by a consortium of electricutilities, BHEL has developed the technology required to make remaining life predictions forshrunk-on low pressure turbine discs. Heat transfe r analysis and stress analysis determine

shrink-fit stresses, thermal stresses, and stress due to blade and disc mass. Disc integrity andremaining life assessment are conducted and recommendations are provided to help determinerun, replacement, or reinspection intervals.

Low pressure (LP) steam turbine disc cracking caused by stress corrosion is experiencedworldwide in rotors used in both nuclear and fossil fuel power plants. Cracking occurs in LProtor discs in keyways, in the blade attachment areas of the rims, on bore surfaces, and on websurfaces. Under a cooperative industry research project, funded by a consortium of electricutilities, BHEL has developed the technology required to make remaining life predictions forshrunk-on low pressure turbine discs. Heat transfe r analysis and stress analysis determineshrink-fit stresses, thermal stresses, and stress due to blade and disc mass. Disc integrity andremaining life assessment are conducted and recommendations are provided to help determine

run, replacement, or reinspection intervals.


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Axial view reveals crack locations in discs with axial-entry firtree type blade attachment grooves.

Diagram shows typical stress corrosion cracking locations on

steeple and rim area of low pressure steam turbine rotor.

Disc steady-state isotherms (F). Disc steady-state tangential stress contours (ksi).


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Finite element grid is used for disc keywey elastic-plastic analysis.

Stress corrosion crack propagates in radial directions from the keywey crown ofa shrunk-on disc.

Nondestructive Evaluation

BHEL offers numerous nondestructive evaluation techniques for inspection of turbine rotors,

disc steeples, and keyways, including periphery ultrasonic, dye penetrant, magnetic particle,and eddy current inspection services.

The Institute developed the turbine rotor examination/evaluation s ystem (TREES), anautomated rotor bore ultrasonic examination system for steam turbines that incorporatesfeatures such as focused search units and a volumetric cell structure to produce uniqueexamination capabilities and excellent flaw resolution. Focuse d beam search units provide areliable means of detecting and sizing flaws without using conventional signal amplitudetechniques. An automated data acquisition and processing computer system processes thedata.

The Institute can custom assemble the TREES package and provide boresonic inspection

services.

BHEL has extensive laboratory and field experience in developing and implementinginternationally recognized inspection and evaluation procedures. Under a utility consortiumprogram, an ultrasonic disc rim inspection system was developed that detects and sizes cracksin blade attachment areas without blade removal.

BHEL also conducts hardness measurements, replication, and microstructural assessments inthe field using portable equipment.


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The BHEL turbine rotor examination/evaluation system (TREES) possesses uniqueexamination capabilities and excellent flaw resolution achieved by computer-designedfocusing lenses attached to ultrasonic transducers. Six lens configurations are employed

to examine zones within the rotor with beam diameter sizes from 0.031 to 0.125 inch.

Steam turbine discs can be inspected for cracking in the rimarea without need for deblading by use of a new BHEL-developed ultrasonic inspection system.

Vibration Control and Rotor Balancing

Using advanced techniques for field measurement, signal processing, diagnostic analysis, andother predictive tools, BHEL can identify and solve rotor, blade, and structural dynamics

problems that put steam turbine generators out of commission. These techniques are used tosolve field problems, while providing confidence at the design stage that turbine trains willexhibit low vibration levels.

Laboratory analysis of vibrational problems with rotating machinery and pi ping Steam turbine-generator rotor balancing Custom design of instrumentation and components for special applications Component testing of valves, pumps, pressure vessels, and instruments

This on-site impact modal analysis equipment measures blade resonance and

mode shapes. Shown here is a high pressure turbine rotor from a 580 MW unitundergoing static blade resonance testing.


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A low power laser and BHEL-built optical target system continuouslymonitors changes in alignment between turbine and generator to defineand solve vibration problems caused by misalignment.

Failure Analysis and Prevention

BHEL uses a multidisciplinary approach to metallurgical failure analysis on a wide range ofsteam turbine and boiler components. Metallurgy, corrosion engineering, stress analysis,fracture mechanics, and nondestructive evaluation are combined to identify mech anisms androot causes of failure. Such analyses help predict and monitor remaining component life.

The Institute maintains a certified hot laboratory for handling materials contaminated byradiation.

Cracks in this turbine disc were initiated at the bore and propagated by stresscorrosion to critical size prior to catastrophic failure.


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Stress corrosion caused extensive transversebranched cracking in this high pressure turbine

casing bolt.

Scanning electron micrograph reveals intergranularstress corrosion cracking of a high pressure turbine

casing bolt.

Material Testing and Evaluation

Static strength, creep, fatigue, impact, fracture toughness, crack growth rate, macro - and micro-hardness, and other testing and evaluati on techniques are available in the Institute's extensivelaboratories.

Controlled test environments include temperature, humidity, vacuum, high pressure, and

immersion in chemically controlled gaseous or aqueous media. Specialized test capabilitiesinclude controlled multi-axial stress conditions, strain rates continuously variable from 1O -6 to10-4 s-l, coupled thermal and mechanical testing, programmed spectrum loading, and directuniaxial loading to 1,650C (3,000F).

Sophisticated computer-controlled servo-hydraulic test systems are available, and manyphysical and thermal-physical property measurements are made according to ISTM standards.Specialized test equipment can be designed and assembled to meet unique test re quirements.

High speed rotor balancing is done at actual operating speeds, where rotor vibrations are

excited by its residual unbalance. Early during the high speed balance procedure, the rotor is

run to overspeed. This important step eliminates residua l stresses and the effects of shrink

fitting, blade seating, and temporary static bows while the rotor is in the balance chamber and

before final balance corrections are made. These changes would otherwise occur in the rotor

during the mechanical test or on-site, possibly delaying the project schedule, increasing costs

and reducing profits. The overspeed run -up and subsequent at-speed balance results in a

balanced rotor that will run smoothly in operation .

OVER SPEED BALANCING TURBINE


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ADVANTAGES OF HIGH SPEED BALANCE

High speed balancing of flexible motors is more effective than low speedbalancing as low speed balancing does not reveal where unbalances exist at

operating speed.

Mechanical integrity of the rotor is verified throughout the entire speed range

prior to installation.

Sensitivity and balancing accuracy are increased due to the lower mass and

greater flexibility of high speed balance pedestals compared to the more rigid

supports typically used on low speed balance machines.

After high speed balance, the calculated rotor response can be verified. This isuseful when a mechanical test of the rotor in a casing is not practical, such as forspare rotors, re-built rotors and re-rated rotors.

High speed balance facility has two pairs of bearing pedestals that support rotorsweighing from 130 lbs. To 27,500 lbs.* both sets of bearing pedestalsaccommodate either tilt-pad or liner type bearings. Elliott maintains a wide rangeof standard size tilt-pad journal bearings. If our standard bearing does not fit your

specific application, we can desig and manufacture a suitable bearing. Below arethe specifications for each set of pedestals

DH4 Pedestal(Manufacturer: SchenckTrebel Corp.)

Maximum rotor weight: (approx) 2,750 lbs. Maximum speed: 27,000 RPM Maximum rotor component diameter: 96 inches Maximum rotor length: (approx) 303 inches

Journal Bearing Diameters: 2.0 to 5.0 in.


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"Moment Weighing" the blades:

A more accurate balance can be obtained by sorting the blades so thatblades of equal static moment are opposite each other. Static moment is

the product of the weight of the blade times the distance from the center of

rotation to the center of gravity of the blade. This static moment issometimes called "moment weight", and the machines to measure it are

called "moment weighing machines". If you started with a balanced hub, andthen assembled the blades so that the moment weight of one blade wasidentical to the moment weight of the blade 180 DEGREEaway, then the

rotor would be very close to a perfect balance. In actual practice, the rotorhub is rarely exactly balanced, and it is often impossible to find pairs ofblades with exactly the same static moment, so a more sophisticated

solution is necessary to achieve the best balance. In this case, specializedsoftware is used which selects the blade locations so that the unbalance of

the rotor disc is compensated for by an equal and opposite net unbalance inthe blades. The larger the quantity of blades available, the better chancethere will be that the solution calculated by the computer will achieve the

balancing tolerance for the assembled rotor.


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DH7 Pedestal (Manufacturer: SchenckTrebel Corp.) Maximum rotor weight: (approx) 27,500 lbs.* Maximum speed: 12,000 RPM Maximum rotorcomponent diameter: 96 inches Maximum rotor length: (approx) 303 inches Journal BearingDiameters: 5.0 to 11.0 in. * Rotors weighing slightly more than 27,500 lbs. might

also be accommodated in our facility, depending upon specific conditions. Our engineering stafwill review these conditions upon request.

STEAM TURBINES

Operation

Theexpansion of steam through numerous stagesin the turbine causes the turbine rotor to rotate.

Steam expands through impulse stage or reaction stage.

Impulse steam turbine stage consists as usual from stator which known as thenozzle and rotor or moving blades

Impulse turbine are characterized by that most or all enthalpy and hencepressure drop occurs in the nozzle.

The rotor blades can be recognized by their shape, which is symmetrical andhave entrance and exit angles around 20. They are short and have constantcross sections.

At BHEL-Hyderabad, compounded turbines are made as they are the most used by plants

Compounded steam turbine means multistage turbine. Compounding is needed when large enthalpy drop is available. Since optimum blade speed is related to the exit nozzle speed. It will be

higher as the enthalpy drop is higher. The blade speed is limited by the centrifugal force as well as needs ofbulky reduction gear Compounding can be achieved either by velocity compounded turbine or

pressure compounded turbine.

VELOCITY COMPOUNDED TURBINE

It is composed of one stage of nozzles, as the single stage turbine,followed by two rows of moving blades instead of one.

These two rows are separated by one row of fixed blades which has the functionof redirecting the steam leaving the first row of the moving blades to the second rowof moving blades.


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Pressure Compounded Impulse Turbine

Pressure compounding impulse turbine is a multistage impulse turbine whereexpansion in the fixed blades (nozzles) is achieved equally among the stages.

Accordingly the inlet steam velocity to each stage is essentially equal, due to equaldrop in enthalpy.

This equal enthalpy drop does not mean equal pressure drop

The Manufacture and Parts Casing:

The typical casing for turbine consists of a cast high-pressure steam chest, an

intermediate barrel section, and a separate exhaust casing. The barrel section isgenerally integral with the steam chest so that the vertical bolting joint is at one of thelatter stages where internal pressures are very much reduced. The steam end, exhaustcasing, nozzle ring, reversing blades and diaphragms are all split on the horizontalcenter line which allows for easy removal of the upper half of the turbine for internalinspection.

The diaphragms are machined on the outside diameter and assembled into groovesaccurately machined in the casing. Cap screws, secured by locking, fasten the nozzle r ingto the steam chest, while the diaphragm halves are locked in position by stops located atthe horizontal split in the casing.

Steam chest passages, nozzle block partitions and the valve opening sequence are allcarefully designed to ensure even and rapid heating of the casing after steam is firstadmitted to the turbine. The high -pressure end of the turbine is supported by the st eamend bearing housing which is flexibly mounted to allow for axial expansion caused bytemperature changes. The exhaust casing is centerline supported on pedestals thatmaintain perfect unit alignment while permitting lateral expansion. Covers on both th esteam end and exhaust end bearing housings and seal housings may be liftedindependently of the main casing to provide ready access to such items as the bearings,control components and seals.

Rotors

Rotors are precisely machined from solid alloy steel forgings. An integrally forged rotorprovides increased reliability particularly for high speed applications.The complete rotor assembly is dynamically balanced at operating speed andoverspeed tested in a vacuum bunker to ensure safety in operation. Hig h speedbalancing can also reduce residual stresses and the effects of blade seating. Elliottalso offers remote monitoring of the high speed balance testing, allowing customers towitness the testing from their offices or at any other location.


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BladesBlades are milled from stainless steel stockpurchased withinstrict specifications forproper strength, damping andcorrosionresistant properties. Disk profiles aredesigned to minimize centrifugal stresses,

thermal gradient and blade loading at thedisk rims. The blades have various shapesto achieve maximum performance and withstandany mechanical stresses.

Stationary Components

Nozzle rings and diaphragms are specifically designed and fabricated to handle the

pressure, temperature and volume of the steam, the size of the turbine and the requiredpressure drop across the stage. The nozzles used in the first stage nozzle ring are cut fromstainless steel. Steam passages are then precision milled into these nozzle blocks beforethey are welded together to form the nozzle ring.

The nozzles in the intermediate pressure stages are formed from profiled stainless steelnozzle sections and inner and outer bands. These are then welded to a circular centersection and to an outer ring then precision ma chined.

The low-pressure diaphragms in condensing turbines are made by casting the stainlessnozzle sections directly into high-strength cast iron. This design includes a moisturecatching provision around the circumference which collects released moisture and

removes it from the steam passage. Additional features such as windage shields andinter-stage drains are used as required by stage conditions to minimize erosion. Alldiaphragms are horizontally split for easy removal and alignment adjustment.

Labyrinth seals are utilized as end gland seals and also interstage seals. Stationarylabyrinth seals are standard for all multistage turbines and grooves are machined on therotating part to improve the sealing effect. The leakage steam from the outer glands isgenerally condensed by the gland condenser. Some leakage steam from the intermediatesection of the steam end gland seals can be withdrawn and utilized by re -injecting it intothe low-pressure stage or low- pressure steam line.Replaceable journal bearings are steel-backed and babbitt -lined with five-shoe tilting paddesign. Thrust bearings are double -acting and self-equalizing. Center pivots are typically

used to make assembly easier and provide maximum protection if reverse for high oiltemperature applications.


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Turbo Generators

The turbo-generator is common-shaft excitation AC synchronous generator with 3phases, 2 poles or with 3 phases, 4 poles.

BHEL-Hyderabad makes turbo generators that have the brushless excitation

mechanism which has been explained in the NTPC report. BHEL presently has manufactured Turbo-Generators of ratings upto 560 MW and is inthe process of going upto 660 MW. It has also the capability to take up the manufactureof ratings upto 1000 MW suitable for thermal power gener ation, gas based and combinedcycle power generation as-well-as for diverse industrial applications

The Manufacture of the Turbo Generator

Stator

The stator is assembled as six parts. It is made up of steel with 4.5% of silica. Silicadecreases hysteresis loss. The sheets are cut at 30 degree angles.

The sheets then are punched with man drill holes, support rod slots and slots for theconductors. This process is called notching and the cutting part as shearing.

The sheets are then varnished after blanking or smoothening of the surface. This is toincrease the insulation.

A bunch of these sheets are stacked together and compressed onto each other so thatair gaps are eliminated. These stacks are then assembled with a small air gapdifferentiating each stack. This ventilates the machine and keeps it cool.

After the assembly of the stator shell, the inside of the slots are varnished.

The sheets of the core are varnished with xylor, at a temperature of 30 -400 degreesCelsius. It is heated, coated then cooled.

After the core is assembled , the winding is placed in the stator. The winding typedepends upon the power required and the current required to be produced.

The Rotor

The rotor is carved out with the slots into a cylindrical shape from a large block of metalusing Lathe heavy machines.

The rotor consists of 2 ends


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The turbine coupling end

The exciter end

The turbine end has a coupling shaft which is circular in shape and has slots.The exciterend has an input lead and an output lead which are used to give the rotor DC input forthe excitation of the rotating field.

The ends of each rotor consist of bearings. These bearings are placed so as to support theshaft. The bearing consists of oil which is used to support a thin film over the surface. Thislubricates and decreases friction and losses. The bearing has top end and bottom end andis stationary. The top end is used to supply the oil.After the construction, the winding isfitted into the slots.The slots and windings are separated by HGL or hard glass laminationwhich insulates the core from the cable. The rotor is constructed so as to obtain brushless

excitation.The complete rotor along with the excitation mechanism is mounted on the shaftand is balanced for synchronous speed. For better balancing weight removal is done asthat is a better option to adding weight to the system.


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TYPES OF TURBOGENERATOR MANUFACTURED BY HEEP-HARDWAR

TARI : Turbo ge

erator with Air-coole

radially indirect cooling.

THW : Turbo generator with Hydrogen and Water cooling.

THRI : Turbo generator with Hydrogen radially indirect cooling.

THDF : Turbo generator with Hydrogen and Water direct cooling.

(a) AirCooledGenerators Upto 200 Mw Range (Type: Tari) Salient Design

Features

y Stator core and rotor winding direct air-cooled

y Indirect cooling ofstator winding

y Horizontallys lit casing design ofstator

y Verticallyside mounted coolers in a se arate housing

y Micalastic bar ty e insulation system

y Se arately assembled stator core and winding for

reducing the manufacturing cycle

y

Brushless/statice

citation system

(b) HydrogenCooled TurbogeneratorsOf 140-260 Mw Range (Type: Thri) Salient

Design Features

y Stator core and rotor winding directly hydrogen cooled

y Indirect cooling ofstator winding

y Rigid core bar mounting Micalastic insulation system

y End shield mounted bearings

y Top ripplesprings in stator slots

y Ring typeshaft seals

y Symmetrical ventilation.

(b)TARI 108/41 GAS TURBINE GENERATOR

FOR FARIDABAD CCPP


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CONCLUSION FOR THE PROJECT OF OSBT:

Best fit computer solutionIf you only have enough blades for a single stage, you should mark eachblade with a serial number and its measured moment. The software willcalculate the best blade to use in each position when the rotor is assembled.Theoretically it would be possible to simply program the computer to try allpossible combinations, and choose the one that results in the lowestunbalance. However, even with modern high speed computers, this wouldrequire hours of computation time for a rotor with more than 30 blades. Toshorten this time to a few seconds, Space Electronics has developed somevery sophisticated algorithms to determine the optimum blade position.Unfortunately, we cannot disclose these in the paper, since they represent

an investment of thousands of hours and our software represents part of theadvantage of using our blade balance machines.

Conclusions: Gas turbine rotors are among the most difficult items to

balance. Assembling the turbine blades in an optimum configuration allows

the operator to balance each stage, so that the flexible turbine rotor does

not bend when rotated at a high speed

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