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    POWER PLANT

    REPAIR TECHNIQUESAT CENTRAL GAS

    TURBINEMAINTENANCE

    WORKSHOP

    FAISALABAD

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    CENTRAL GAS TURBINE MAINTENANCE

    WORKSHOP WAPDA FAISALABAD

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    CONTENTS

    1. INTRODUCTION OF WORKSHOP2. OBJECTIVES.3. ORGANIZATION CHART.

    4. FIELD OF SERVICES.5. SERVICES TO PRIVATE &

    GOVERNMENT ORGANIZATIONS.6. FLOW DIAGRAM OF REPAIR PARTS.

    7. INTRODUCTION OF REPAIR SHOPS.8. PARTS RECEIVED/DESPATCHED9. OVERALL VIEW OF REPAIRED PARTS10. SOME MAJOR WORKS DONE

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    After the commissioning of 200 MW GTPS

    Faisalabad in order to keep the Power Plant ready for

    operation necessity to have sufficient quantity of spare

    parts was un-avoidable. This was only possible byimporting new parts or by sending the used ones abroad

    for repair.

    All the turbine hot gas path components are made ofhigh temperature (Nickel & Cobalt) alloys.It was not

    possible to manufacture or repair of turbine parts in our

    country so necessity to repair used parts within our

    country was strongly felt.

    INTRODUCTION OF CENTRAL GASTURBINE MAINTENANCE WORKSHOP

    FAISALABAD

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    This idea was brought in the physical state by

    Late Shakoor Ahmad, working as Chief Engineer

    (Th) Faisalabad at that time. Which not only helped tointroduce repair of super alloys in Pakistan but on the

    other hand helped a lot in decreasing the import of new

    parts which resulted in saving precious foreign exchange

    & reducing the down time of Power Plant as well asavailability at the earliest.

    To establish a repair Workshop funds to import the

    equipment from abroad in foreign currency and to

    construct a building in pak currency were needed. For

    this purpose left over amount after the completion of 200

    MW GTPS Faisalabad was utilized local components of

    cost of project was provided by Wapda.

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    CONSULTANCY OF TECHNICAL WORKS.

    M/S FICHTNER Suttgart West Germany were appointed

    as consultants where as their local counter part was M/S

    MIDEAST Consultants Lahore.

    SUPPLY OF EQUIPMENT.

    Workshop equipment was supplied by M/S SIEMENSand Co Hamburg West Germany and their local counter

    part was M/S MIDEAST Lahore.

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    CIVIL WORK CONTRACT.

    M/S Syed Imdad Hussain Shah and Company were

    awarded the contract of civil works to complete thebuilding. Total cost of the project was Rs.20.2 million.

    The bifurcation of which is as under:-

    1. Local = Rs.11.10 Million

    2. Foreign = Rs. 9.10 MillionTotal:- Rs.20.20 Million

    After the arrival of equipment it was installed in the

    presence of Mr.W. Boll representative of M/S SIEMENS.Same gentleman later on trained the locally appointed

    staff. In this way the repair of turbine hot gas path

    components was initiated first time by Wapda itself. So

    the old Workshop started functioning during 1983.

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    MAIN HALL OF OLD WORKSHOP BUILDING

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    EXTENSION OF WORKSHOP FACILITIES

    With the passage of time Gas Turbines ranging from 90to 140 MW & Steam Turbines from 210 to 320 MW

    started operating in Wapda Generation System. So the

    necessity to have another Workshop to handle and

    repair large parts of above said Gas & Steam Turbines infuture was strongly felt.

    For this purpose M/S EU-BANK PRIECE UK wereappointed as consultants by Wapda who were

    responsible for the supply of equipment. M/S ICL were

    awarded to design and construct Workshop building.

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    Total cost of the extension project was 219.245 Million.

    Bifurcation of which is as under:-

    1. Cost of Civil Works = Rs. 59.400 Million

    2. Cost of Equipment = Rs.159.845 Million

    Total:- Rs.219.245 Million

    The installation of most of the equipment was done by

    Workshop staff, whereas installation of Heavy Duty

    Lathe Machine, Over Head Crane and Vacuum Furnace

    was completed by their respective representatives. This

    new Workshop started rendering services during 1994.

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    MAIN HALL OF NEW WORKSHOP BUILDING

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    OBJECTIVES

    TO PROVIDE INSPECTION AND REPAIR FACILITIES TOALL THERMAL POWER STATIONS OF WAPDA POWERGENERATION SYSTEM.

    PREVIOUSLY TURBINE DAMAGED PARTS WERE BEINGSENT TO FOREIGN COUNTRIES FOR WANT OFREPAIRS.

    THE FOREIGN REPAIR COST WAS ABOUT 40% OF THENEW PARTS PRICE AND ALSO IT REQUIRED LONGERDOWN TIME OF UNITS.

    TO IMPROVE THE TECHNICAL KNOW HOW OF LOCALWAPDA STAFF

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    Workshop is equipped to provide following services:-

    1. Repair of hot gas path components of GE Fiat,

    Mitsubishi, Westinghouse & KWU Gas Turbines. 2.

    Re-balding of Gas, Steam Turbine Axial and

    Compressor Rotors.3. Re-insulation of Generator Rotors.

    4. Re-winding of Electric Motors.

    5. Re-babiting & machining of all type Bearings.

    6. Dynamic balancing of Rotors ranging from 50 to

    60,000 Kgs.

    7. Non destructive testing of turbines parts.

    8. Moment weighing of GE F-9 turbine blades.

    9. NDT facilities at site to all customers.

    10. On Site Dynamic balancing Rotating Equipments.

    FIELD OF SERVICES

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    In addition to all Thermal Power Station of Wapda PowerGeneration System this Workshop is also extending the

    repair facilities to more than 100 organisations of Private

    and Government Sector, some important are as

    following:-1. Kot Addu Power Company Kot Addu.

    2. Karachi Electric Supply Corporation.

    3. Pakistan Aeronautical Complex Kamra.

    4. Sui Northern Gas Pipe Lines.

    5. Attock Oil Refinery.

    6. Pakistan Ordinance Factories Wah Cantt.

    7. Rousch Power Plant Abdul Hakeem.

    8. Pak Arab Fertilisers Multan.

    9. Pak-American Fertilizer Daud Khail.

    SERVICES TO PRIVATE &GOVERNMENT ORGANIZATIONS

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    10. Pakistan Petroleum Limited.

    11. Dawood Herculees Sheikhupura.

    12. Packages Limited, Lahore.

    13. Chenab Industries, Faisalabad.14. Kohinoor Power Company, Faisalabad.

    15. CPC Rafhan Maize Products, Faisalabad.

    16. Kohinoor Sugar Mill, Joaharabad.

    17. Army Welfare Sugar Mill, Badin.18. Shakargang Sugar Mill, Jhang.

    19. Baba Farid Sugar Mill, Okara

    20. Sheikhoo Sugar Mill, Kabirwala.

    21. Fauji Power Complex, Kabirwala.22. Saba Power Plant, Sheikhupura.

    23. Oil and Gas Development Limited.

    24. Engro Chemicals.

    25. Pakistan ordinance Factory Wah.

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    FLOW DIAGRAM OF REPAIR OF PARTS

    Preliminary Inspection

    Chemical Cleaning

    Dis-Assembling

    N.D.T

    Annealing

    Grinding Welding Grinding

    N.D.T

    Assembling

    Despatch Point

    Mech. Cleaning

    Inspect. Dept.

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    A. MACHINE SHOP.

    MACHINES AVAILABLE.

    1. CNC heavy duty horizontal lathe machine up to4 Meter swing dia.

    2. Vertical turning lathe machine ranging up to

    3.3 Meter swing dia.

    3. Vertical lathe machine up to 1.4 Meter swing dia.4. Horizontal boring & facing machine.

    5. Valve lapping machine for globe & gate valve.

    INTRODUCTION OF REPAIR SHOPS

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    7 Radial arm drilling machine.

    8. Precision lathe machine.

    9. Milling machine.

    10. Metal cutting handsaw.11. Valve grinding machine.

    12. Metal plate roller.

    13. Manual hydraulic mounting press.

    14. 80 tons overhead crane.15. Metal sheet cutter up to 12 mm S.S Sheets.

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    B. N.D.T SHOP.

    1. Magnetic Particle Inspection

    2. Universal AC hand yokes.

    3. Penetrant Flouricent Inspection under UVL

    4. Penetrant Inspection in day light

    5. Ultrasonic flaw detector.

    6. Radiography and X-ray equipment.

    7. Crack depth meter.

    8. Eddy current testing equipment

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    C. GRINDING SHOP.

    1. Burr grinding & re-sharpening machine.

    2. Electric discharge machine.3. Grinding and cutting discs and carbide burrs.

    4. Pneumatic and electrical grinders.

    5. Carbide burrs of different shapes and sizes.

    6. Portable electric / pneumatic grinders.

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    D. HEAT TREATMENT SHOP.

    1. Vacuum Heat Treatment Furnace.

    2. Induction Heating Equipment.

    3. Electric Heaters Heat Treatment Furnace

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    E. CLEANING SHOP.

    1. Vapour Blasting Machine.2. Sand Blasting Machine.

    3. Steam Jet Cleaner.

    4. Turco Cleaning Cycle, Turco 4181, 4338C.

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    F. ROTOR BALANCING SHOP.

    1. Heavy Duty Balancing Machine 60 Ton.

    2. End Driven & Belt Driven Balancing Machine from 50 To 3000 Kgs.

    3. Moment Weighing Machine For GE F-5 Blades.

    4. Universal Vibration Measuring Instrument.

    5. Portable Vibration Analyzer.

    6. Onsite Balancing Equipment.

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    G. WELDING SHOP.

    1. TIG Welding Equipment.

    2. Stationary Spot Welding Machine.3. Weld Heat Treatment Equipment.

    4. Electric Welding.

    5. Oxy-Acetylene Welding.

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    H- ELECTRICAL AND INSTRUMENT SHOPS.

    1. Maggers2. Relay Test Set.3. Inductance Measuring Equipment4. LRC Data Bridge.

    5. Digital Multi Meters.6. Motor Winding Equipment.7. Cable Testing Set

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    REWINDING OF GENERATOR ROTOR TPS KOTRI

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    REWINDING OF 6.6 KV MOTOR STATOR

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    MOTORS OF DIFFERENT POWER STATIONS UNDER REPAIR

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    1. Carbon.It is a foremost alloy element of steel and has for

    reaching influence in it. In addition to carbon

    every unalloyed steel contains silicon

    manganese, phosphorus and sulphur. As the

    carbon contents rises the mechanical strength

    and hardening propertiesof the steel improves

    but the elasticity, forging welding and cuttingproperties suffer.

    MATALURGY OF SUPER ALLOYS

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    2. Coblat.Melting point of this material is 1500 C. It improves theresistance to tempering and the hot tensile strength..

    3. Chromium.Melting point 1920 C. It increases the hardness and

    strength and only reduces the elasticity. It improves the

    resistance to heat and non acting properties. With higher

    chromium contents the steel becomes corrosionresistance and with carbon forms high wearresistancecarbide. The welding properties deteriorate inpure chromium steel and with increasing chromium

    contents.

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    4. Manganese.

    The melting point of this material is 1250 C. itimproves the strengthen property of steel but only

    slightly improves its elasticityit has favourableinfluence on welding properties.

    5. Molybdenum.The melting point of this metal is 2610 C. it improves

    the tensile strength and elasticity and heatresistanceand has favourable influence on thewelding properties..

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    6. Nickel.The melting point of this metal is 1453 C. it raises the

    strength of steel but drops the elasticity. It ensureshardnesswhen the steel contains chromium.

    7. Silicon.The melting of this metal is 1410 C. It is present in all

    steel since the iron ores used in their manufacturing

    contain varying amount of it. Silicon increasemechanical strength, the resistance to scaling.

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    8. Vanadium.The melting of this metal is 1730 C. A small addition improves the

    hot hardness. It is strong carbide former increases tensilestrength and yieldpoint.

    9. Tungsten.The melting of this metal is 3380 C. It improves the strength

    properties and also responsible for high heat resistancevalues.10. Zirconium.The melting of this metal is 1860 C. It increases the life of heat

    conducting steels.

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    Gas Tungsten Arc Welding (GTAW).

    This is a process in which joining of metals isproduced by heating them with an arc between a

    tungsten (non consumable) electrodes and the

    work. It is generally done by using single

    electrode. Shielding of the electrode and weld

    zone is done by a gas or as gas mixture. It is

    some times called TIG. Following of the main

    equipment required for TIG welding:-1. Power force.

    2. Welding holder & tungsten electrodes.

    3. Shielding by argon & control.

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    Principal of Operation.The heat from TIG welding is obtained by an arc

    between the tungsten electrode and work piece. High

    frequency equipment installed in the weldingmachine helps the arc to jump from tungsten to work

    piece when the holder is brought at certain distance

    from the work piece once arc is established the

    welding can be done as per job requirements. During

    welding inert gas shield is provided.

    Advantages.

    It is an excellent welding method due to excellent

    control of heat in put and gives high quality welding

    free of welding defects.

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    Limitations.

    1. Slower than consumable electrode arc

    welding process.

    2. Transfer of molten tungsten from the

    electrode to the weld causescontamination. The resulting tungsten

    inclusion is hard and brittle.

    3. Repair cost is much higher than

    ordinarily welding equipment.

    4. Use of argon or helium increases the

    repair cost.

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    GAS TUNGSTEN ARC WELDING

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    RE-BABBITING OF

    BEARINGS

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    COMPOSITION AND TEMPERATURES

    Major portion of R-11 is Tin which is about 87%ofwhole alloy. Remaining 13% are Cu, lead, Antimony &

    Bismith etc.

    Melting point of R-11 is about 384 C.

    Another metal which provides a bond material between

    base metal of Bearings and Babbitt material is pure tin.

    Fore re-babbiting of Bearing Oxy Acetylene Method

    methods is commonly used.

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    REPAIR PROCEDURE

    In order to re-Babbitt a Bearing following steps arenecessary:-

    i) Removal Of Used White Metal Of Bearings.

    Ii) Cleaning Of The Bearing Surface With Zincand Amonium Chlorides .

    Iii) Tinning Of Bearing Surface.Iv) Finally Re-babbiting With White Metal.

    During repair process close watch on thetemperature of Bearing surface is necessary toavoid the over heating of tin.

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    RE-METALLING OF JOURNAL BEARING

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    RE-METALLING OF JOURNAL BEARING

    I W k h t hit t l i d b

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    In Workshop extra white metal is removed bygrinding

    NDT is carried out to check the Bonding of whitemetal with the bearing shell .

    After machining ultrasonic testing is carried outto check the bonding of the white metal with theshell.

    Strict quality control is maintained by inspectiondepartment. Porosity, pin holes & lack ofbonding is not allowed. If a Bearing passsatisfactorily through all these process.

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    MACHINING OF JOURNAL BEARING

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    ULTRASONIC INSPECTION OF JOURNAL BEARINGS

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    JOURNAL BEARING AFTER FINAL MACHINING

    OVERALL VIEW OF PARTS REPAIRED

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    OVERALL VIEW OF PARTS REPAIREDFROM 1982 TO 06/2009

    S/N DESCRIPTION QTY.1 Turbine Moving Buckets. 12756

    2 Combustion Liners. 2993

    3 Transition Pieces. 2352

    4 Cross Fire Tubes. 2515

    5 Shrouds Blocks. 1915

    6 Bearings. 1606

    7 Compressor Blades. 15138 Retainer Plates. 1645

    9 Floating Seals. 1191

    10 Bearing Pads. 1072

    11 Swirl Tips 918

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    11 Swirl Tips. 918

    12 End Seals. 907

    13 Vane Segments. 682

    14 Scrapper Chain Links. 517

    15 Bull Horns. 664

    16 Light / Heavy Motors. 370

    17 Turbine Nozzle Support Rings 33918 Turbine Nozzle. 325

    19 Pressure Gauges. 300

    20 Turbine Diaphragms. 257

    21 Electronic Cards. 203

    22 Track Block. 181

    23 Labyrinth Seals. 134

    24 Turbine Rotors. 138

    26 Stuffing Box Seals. 83

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    6 S u g o Sea s 83

    27 Bushes. 64

    28 Contactors. 75

    29 Generator Rotors. 6330 Pumps. 62

    31 Slip Rings. 55

    32

    Steam Turbine Diaphragm Support

    Ring.

    49

    33 Heavy Duty Shafts. 44

    34 Hydrogen Seals. 60

    35 Impellers. 3436 Pressure Switches 28

    37 Gears. 21

    38 Diffusers. 21

    39 Control Valves. 19

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    40 Solenoid Valves. 18

    41 Multiple Disc Jaw Clutches. 15

    42 Shaft Sleeves. 28

    43 Combustor Wrapper. 13

    44 Turbine Nozzle Discs. 14

    45 Spring Seals. 13

    46 Shaft Sleeves. 14

    47 Wiper Seal. 2

    48 Casing. 4

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    SOME MAJOR WORKS DONE

    RE-BLADING OF 210 MW LP STEAM TURBINE ROTOR

    REPAIR OF 35 MW GENERATOR TOROR TPS QUETTA

    REBLADING OF 100MW GAS TURBINE COMPRESSOR

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    RE-BLADINGOF 210 MW

    L.P TURBINE ROTOR

    OF TPS GUDDU

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    CASE STUDY

    During major overhauling of 210 MW Steam Turbine PowerPlant at TPS Guddu, it was observed outer four stages(2+2) of LP Turbine Rotor have damaged and needreplacement with new ones.

    They sent the Rotor to Central Gas Turbine MaintenanceWorkshop Faisalabad.

    TECHNICAL DIMENSIONS OF ROTOR

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    TECHNICAL DIMENSIONS OF ROTOR

    STATION: THERMAL POWER STATION

    GUDDU RATING: 210 MW (UNIT NO.3)

    TYPE: LOW PRESSURE

    WEIGHT: 25000 KG.

    DIA METER: 3050 MM LENGTH: 7320 MM

    MANUFACTURED BY: LENIN GRAD METAL WORKS USSR

    SUPPLIED BY: M/S TECHNO PROME EXPORTS

    USSR JOBS: REPLACEMENT OF L.P ROTOR

    TURBINE BLADES OF STAGENOS.26, 27, 30 & 31 WITH NEWONES.

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    CUTTING OF DAMAGED BLADES WITH WELDING PROCESS

    PROCEDURE ADOPTED FOR RE-BLADING

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    OF LP ROTOR

    Cutting of damaged blades with welding process.

    Loading of Rotor on CNC Heavy Duty Lathe Machine.

    Machining of roots of blades.

    Removal of pin portions left in turbine discs.

    Fixing of blades in turbine wheels.

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    FIXING OF ROTOR ON CNC HEAVY DUTY LATHE MACHINE

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    MACHINING OF ROTORS OF BLADE STAGE NO.26 & 30

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    Drilling of holes in blades.

    Machining of 372 pins to be fixed in.

    Fixing of pins in blades.

    Fixing of lacing wire in blades.

    Machining of turbine blades.

    Sand blasting.

    Non Destructive Testing.

    Dynamic Balancing (final balancing results attached).

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    DRILLING OF HOLES IN BLADES STAGE NO.26, 27 30, & 31

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    MACHINING OF PINS TO BE FIXED IN BLADES

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    FIXING OF LACING WIRE IN BLADES

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    MACHINING OF TURBINE BLADE OF STAGE No.26 & 30

    TO PROVIDE HOSING FOR SEALS OF STATOR

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    SAND BLASTING OF ROTOR

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    NDT OF THE ROTOR

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    DYNAMIC BALANCING OF THE ROTOR

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    REPAIR OF 35 MW

    GENERATOR ROTORTPS QUETTA

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    DAMAGED WINDING IS BEING REMOVED

    PROCEDURE ADOPTED FOR REPAIR OF

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    GENERATOR ROTOR Run out was checked

    Ultrasonic inspection was carried out

    Special fixtures were fabricated to remove coupling

    Both cooling fans & Generator Rotor Retaining Rings(GRRR) were removed

    Special fixture was fabricated to hold the winding coilsduring their removal from Rotor slots.

    Wedges were removed from the Rotor body slots.

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    Winding links of three coils were de-brazed.

    Damaged turns of all winding coil were removed

    Damaged insulation was removed from each turn of coils

    Broken turns were brazed and checked by NDT

    New lining of Rotor slots was done with fibber glass.

    Nomax paper of proper size was cut and pasted

    All coils were inserted back into their respective slots

    Special jacks were fabricated to press each coil and werefitted on the slots in order to press the coil turns.

    Two special circular fixtures were fabricated to press thehanging portion of the windings

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    NDT of new Generator Rotor Retaining Rings (GRRR) wascarried out (report attached).

    The winding of the Rotor was heated up to 180oC by electriccurrent method and were pressed with special jack method.

    Both GRRR and coiling fans were fitted on the both side of the

    Generator Rotor.

    Insulation strength of the generator was checked and wasfound satisfactory.

    Dynamic balancing of the Rotor was performed.

    After the completion of repair work complete electrical testingwas carried out according to standard and it was found OK.

    After installation of rotor in machine some sort of vibrationwas observed which was rectified on site.

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    A FIELD WINDING COILS TURN ARE HELD ON FIXTURE AFTERPASTING NEW INSULATION PAPER

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    BRAZING OF DAMAGED ROTOR WINDING

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    CONNECTION LEAD IS UNDER REPAIR AFTER BRAZING

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    FIELD COIL INSULATION STRENGTH IS BEING CHECKED

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    DYNAMIC BALANCING OF GENERATOR ROTOR ONBALANCING MACHINE

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    100 MW GAS TURBINE

    AXIAL COMPRESSORTPS GUDDU

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    TECHNICAL DIMENSIONS OF ROTOR

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    STATION: THERMAL POWER STATIONGUDDU

    RATING: 100 MW (UNIT NO.4)

    TYPE: AXIAL COMPRESSOR ROTOR

    WEIGHT: 28600 KG.

    DIA METER: 1917 MM LENGTH: 5030 MM

    MANUFACTURED: GENERAL ELECTRIC

    JOBS: REPLACEMENT OF BLADES OF

    ALL SEVENTEEN STAGES WITH NEW ONES

    RE BLADING OF 100 MW GAS TURBINEAXIAL COMPRESSOR ROTOR

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    DEFECT

    One blade of 2nd stage was found broken from the rootand it has damaged all the blades of successive stages.

    Cleaning of compressor Rotor blades was carried outwith CTC and its inspection was carried out.

    Condition of all damaged blades revealed that all theseblades have damaged due to direct hitting and rubbingwith the broken blade.

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    PROCEDURE ADOPTED FORREBLADING OF COMPRESSOR

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    REBLADING OF COMPRESSOR

    Sand blasting of Rotor.

    NDT of the complete Rotor.

    Complete run out check was performed.

    Different reference marks were punched on the parts ofthe Rotor.

    Record of different dimensions & measurements was

    prepared for re-assembling of the Rotor.

    Hydraulic bolt tensioning system for unbolting of tiebolts was arranged through tenders.

    The compressor Rotor was held vertically in the under

    ground pit

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    ground pit.

    All seventeen-compressor Rotor discs were dismantled one

    by one by self made fixture.

    Damaged blades and spacers were removed from allcompressor discs.

    The compressor wheels were cleaned and NDT of all thedisc & tie rod bolts was performed.

    Balancing charts were prepared for the new moving blades.

    New blades of all the stages were fitted in these wheels.

    All compressor discs were re-assembled in vertical position

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    All tie rod bolts were tightened

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    The compressor rotor was brought in horizontal position.

    The complete assembly was loaded on the turbine lathmachine and run out check was performed.

    Stub shaft of the turbine was attached to the compressor

    with the help of coupling bolts.

    Dynamic balancing of the Rotor was carried out.

    Stub shaft was disassembled from the compressor

    The repair work was successfully completed with ourown Technical skill and saved foreign exchange ofmillions of Dollars.

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    THANKS