PRESENTATION ON “500 MW KWU TURBINE”

1. PRESENTATION ON “500 MW KWU TURBINE” BY AMIT KUMAR, EE (M), KTPS, DVC

2. BASIC PRINCIPLES OF STEAM TURBINE • A steam turbine works on the principle of conversion of High pressure & temperature steam into high Kinetic energy , thereby giving torque to a moving rotor. • For above energy conversion there is requirement of converging /Converging- Diverging Sections • DROP IN PRESSURE OF STEAM THROUGH SOME PASSAGE RESULTING IN • INCREASE IN VELOCITY • CHANGE IN DIRECTION OF MOTION WHICH GIVES RISE TO A CHANGE OF MOMENTUM OR FORCE • THIS IS DRIVING FORCE OF THE ROTOR

3. WORKING PRINCIPLE OF STEAM TURBINE • Steam at high pressure & temperature is made to pass through a row of fixed blade mounted on stationary body in Casing. • There will be drop in pressure of the steam across the fixed blade resulting in very high steam velocity at the exit of fixed blade • The high velocity steam then impinges on another row of rotating blades mounted on the rotor shaft • The impingement of high velocity steam generates driving force on these rotating blades which rotate the rotor. • A set of fixed blades blades and rotating blades mounted on rotor is called stage of turbine. Depending on steam condition and power output, number of stages in steam turbine is decided ROTATING BLADE ROW FIXED BLADE ROW DRIVING FORCE STATIONARY BODY/CASING ROTOR

4. TYPES OF TURBINE • IMPULSE TURBINE = In a stage of Impulse turbine the pressure/Enthalpy drop takes place only in Fixed blades and not in the moving blades • REACTION TURBINE = In a stage of Reaction Turbine the Pressure/enthalpy drop takes place in both the fixed and moving blades.

5. 500 MW KWU TURBINE FEATURES TYPE: TANDEM COMPOUND-REACTION-SINGLE REHEAT – CONDENSING TYPE TURBINE WITH THROTTLE GOVERNING.

6. Constructional features 500 MW ST HP Turbine IP Turbine TG LP Turbine ESV & CV Exciter CAP LP BV IV & CV CRH-NRV

7. 500 MW RATED STEAM PARAMETERS

8. TURBINE CYCLE & EXTRACTION

9. Inner Casing Outer Casing-Barrel type Shaft Seal- Front Shaft Seal-Rear Inlet Exhaust HP TURBINE

10. HP TURBINE • SINGLE STEAM FLOW OF TWO SHELL (CASING) DESIGN • BARREL TYPE OUTER CASING- HP elements utilize a unique barrel design. • IT HAS NEITHER AN AXIAL OR RADIAL FLANGE. • PERFECT SYMMETRIC DESIGN OF THE OUTER CASING AND UNIFORM WALL THICKNESS AT ALL SECTIONS • UNIFORMLY CONTROLS THERMAL EXPANSION, PERMITTING RAPID LOAD CHANGES. • THE INNER CASING IS AXIALLY SPLIT & IS ALMOST CYLINDRICAL IN SHAPE- • CIRCULAR CROSS-SECTION OF THE INNER CASING REDUCES STRESS RISERS TO MINIMIZE JOINT MAINTENANCE ISSUES. • THE TURBINE HAS 2 MAIN STOP VALVES (ESV) AND 2 CONTROL VALVES (CV) LOCATED SYMMETRICALLY TO THE RIGHT AND LEFT OF THE CASING. THE VALVES ARE ARRANGED IN PAIRS WITH ONE STOP VALVE AND ONE CONTROL VALVE IN A COMMON BODY.

11. Intermediate Pressure Turbine Extraction Inlet Outer Casing Exhaust Rotor Inner Casing

12. IP TURBINE •  THE IP TURBINE IS OF DOUBLE FLOW CONSTRUCTION WITH TWO NOS HORIZONTALLY SPLIT CASINGS ( INNER & OUTER CASING). • THE HOT REHEATED (HRH) STEAM ENTERS THE INNER CASING AT THE MID SECTION FROM TOP AND BOTTOM AND EXPANDS IN OPPOSITE SIDE IN TWO BLADE SECTIONS AND COMPENSATE AXIAL THRUST. • THE INNER CASING CARRIES THE STATIONARY BLADING. • CASING IS MADE OF CREEP RESISTING CHROMIUM-MOLYBDENUM- VANADUIUM (Cr-Mo-V) STEEL CASTING. • THE SHAFT IS MADE OF HIGH CREEP RESISTANCE Cr-Mo-V STEEL FORGING.

13. HP/IP TURBINE BLADINGS • HP TURBINE BLADING CONSISTS OF 17 REACTION STAGES WITH 50 % REACTION. • IP TURBINE BLADING CONSISTS OF 12 REACTION STAGES PER FLOW WITH 50 % REACTION. • THE STATIONARY AND MOVING BLADES OF ALL STAGES ARE PROVIDED WITH INVERTED T-ROOTS IN BOTH HP & IP TURBINE. • ALL THESE BLADES ARE PROVIDED WITH INTEGRAL SHROUDS WHICH AFTER INSTALLATION FORM A CONTINUOUS SHROUD. • THE MOVING AND STATIONARY BLADES ARE INSERTED INTO THE CORRESPONDING GROOVES IN THE SHAFT AND INNER CASING. THE INSERTION SLOT IN THE SHAFT IS CLOSED BY A LOCKING BLADE WHICH IS FIXED BY GRUB SCREWS. • SEALING STRIPS ARE CAULKED INTO THE INNER CASING AND THE SHAFT TO REDUCE LEAKAGES LOSSES AT THE BLADE TIPS. • HP TURBINE BLADES: • From 1st. to 8th. stages are provided with ‘3Ds“ blades. • 9th. to 13th. stages with ‘TX’ blades • 14th. to 17 th. stages with ‘F’ blades • IP TURBINE BLADES: • IP initial stages are provided with ‘3Ds“ blades. • Intermediate stages with ‘TX’ blades • Rear stages with ‘F’ blades

14. TYPICAL CYLINDRICAL BLADE SUCTION SIDE SHROUD INLET EDGE EXIT EDGE WORKING PROFILE PRESSURE SIDE RHOMBOID BLADES ARE HAVING THREE MAIN PARTS : 1. AEROFOIL : IT IS THE WORKING PART OF THE BLADE WHERE STEAM EXPANSION TAKES PLACE. 2. ROOT : TI IS THE PORTION OF THE BLADE WHICH IS HELD WITH ROTOR OR CASING 3. SHROUDS : TO HOLD END PORTIONS OF BLADES. ROOT NECK TANG

15. 500 MW KWU TURBINE BLADES

16. LP Turbine ATMOSPHERIC RELIEF DIAPHRAGM LP INNER OUTER CASING EXHAUST DIFFUSER GUIDE BLADE CARRIERS LP INNER INNER CASING ROTOR LP FRONT WALL LP LONGITUDINAL GIRDER

17. LP TURBINE DESIGN FEATURES • DOUBLE FLOW • TRIPLE SHELL • * INNER INNER CASING • * INNER OUTER CASING • * OUTER CASING • SINGLE ADMISSION FROM TOP HALF • MONOBLOC ROTOR • INNER CASINGS CASTING • OUTER CASING FABRICATED STEAM TURBINE ENGINEERING HARIDWAR

18. LP TURBINE • LP TURBINE CASING CONSISTS OF DOUBLE FLOW UNIT AND HAS A TRIPLE SHELL WELDED CASING. • THE OUTER CASING CONSISTS OF FRONT AND REAR WALLS, TWO LATERAL LONGITUDINAL SUPPORT BEAMS AND THE UPPER DOME AND CONNECTED TO CONDENSER BY WELDING. • THE INNER-INNER & INNER-OUTER CASING CARRIES THE TURBINE GUIDE BLADES AND DIFFUSER. • STEAM ADMITTED TO THE LP TURBINE INNER CASING FROM IP TURBINE FROM BOTH LEFT AND RIGHT SIDE HORIZONTALLY. • EXPANSION JOINTS ARE INSTALLED IN THE STEAM PIPING TO PREVENT ANY UNDESIRABLE DEFORMATION OF THE CASINGS DUE TO THERMAL EXPANSION OF THE STEAM PIPING.

19. LP BLADING NO. STAGES :2 x 6 TYPE OF BLADING : ADVANCE CLASS * INITIAL STAGES - TX PROFILE * MIDDLE STAGES - TWISTED PROFILE * LAST 3 STAGES - ADVANCE CLASS WITH BANANA TYPE GUIDE BLADE IN LAST STAGE GUIDE BLADE CARRIER WITH BANANA BLADING

20. LP TURBINE BLADING • LP TURBINE BLADING CONSISTS OF 6 REACTION STAGES PER FLOW WITH 50 % REACTION. • FIRST THREE STAGES ARE PROVIDED WITH INVERTED T-ROOTS. ALL THESE BLADES ARE PROVIDED WITH INTEGRAL SHROUDS WHICH AFTER INSTALLATION FORM A CONTINUOUS SHROUD. FIRST THREE GUIDE BLADES ARE MOUNTED ON INNER-INNER CASING. • LAST THREE STAGES OF LP TURBINE ARE ALSO REACTION STAGES. EACH STAGE IS MADE OF GUIDE AND MOVING BLADES. • THE LAST STATIONARY BLADES ARE MADE BY WELDING INNER RING, BLADES AND OUTER RING TOGETHER TO FORM GUIDE BLADE CARRIERS IN TWO HALVES AND ARE BOLTED TO INNER-OUTER CASING. • THE STATIONARY BLADES OF 4TH AND 5TH STAGES ARE MADE OF CAST STEELS AND 6TH STAGE STATIONARY BLADE ARE MADE FROM STEEL SHEETS TO FORM HOLLOW BLADED. SUCTION SLIT ARE PROVIDED IN 6TH STAGE BLADES. THROUGH THESE SLITS WATER PARTICLE ON THE SURFACE OF THESE LAST STAGE GUIDE BLADES ARE DRAWN AWAY TO THE CONDENSER. • THE 4TH STAGE MOVING BLADE IS OF TAPERED TWISTED BLADES HAVING INTEGRAL SHROUDS WITH T-ROOT. THE LAST TWO STAGE MOVING BLADES ARE OF TWISTED DROP FORGED BANANA TYPE CONSTRUCTION HAVING CURVED FIR-TREE ROOTS WHICH ARE INSERTED IN AXIAL GROOVES IN THE TURBINE SHAFT AND SECURED BY MEANS OF CLAMPING PIECES. LAST TWO STAGE MOVING BLADES DOES NOT HAVING ANY SHROUDS.

21. LP TURBINE BLADE NOMENCLATURE LP INNER OUTER CASING LP INNER INNER CASING 3L 3R 2R 2L 1R 1L TURBINE REAR (L) TURBINE FRONT (R) LP ROTOR LP SHROUDED BLADES LP FREE STANDING BLADES DOUBLE FLOW TURBINE

22. TURBINE SHAFT SEALS • THE FUNCTION OF THESE SHAFT SEALS IS TO SEAL THE INTERIOR OF THE CASING FROM ATMOSPHERE AT THE END OF THE SHAFT ON THE ADMISSION AND EXHAUST SIDES. • THE SEALING BETWEEN THE ROTATING AND STATIONARY PARTS OF THE TURBINE IS ACHIEVED BY MEANS OF SEAL STRIPS CAULKED INTO SEAL RINGS OF THE CASING AND INTO THE ROTOR • HP TURBINE FRONT SHAFT SEAL IS OF LABYRINTH TYPE WHILE REAR SHAFT SEAL IS SEE THROUGH TYPE. • IP TURBINE FRONT SHAFT SEAL IS OF LABYRINTH TYPE DUE TO LOW RELATIVE EXPANSION WHILE REAR SHAFT SEAL IS SEE THROUGH TYPE DUE TO GREATER RELATIVE EXPANSION. • LP TURBINE FRONT & REAR SHAFT SEAL IS OF SEE THROUGH TYPE DUE TO GREATER RELATIVE EXPANSION ON BOTH SIDES.

23. LABYRINTH SEAL A labyrinth seal is a type of mechanical seal that provides a tortuous path to help prevent leakage. SEAL STRIPS ARE CAULKED ALTERNATIVEY INTO THE SHAFT AND INTO THE SPRING SUPPORTED SEGMENTED RINGS IN THE CASING FORMING A LABYRINTH. THE PRESSURE GRADIENT ACROSS THE SEALS IS REDUCED BY CONVERSION OF PRESSURE ENERGY INTO VELOCITY ENERGY WHICH IS THEN DISSIPATED AS TURBULENCE AS STEAM PASSES THROUGH NUMEROUS COMPARTMENTS ACCORDING TO THE LABYRINTH PRINCIPLE.

24. SEE THROUGH SEALS In see through seals, the seal strips are located opposite to each other, caulked into the shaft and into seal rings centered in the outer Casing.

25. GLAND SEALING SYSTEM OF 500 MW KWU TURBINE • Since the Turbine shaft has to rotate freely, there has to have some gap between the shaft and the turbine casing, from where either Steam will try to escape out or Atmospheric air will try to sneak in. • The steam turbine inlet pressure is in Hundreds of Bar but when the steam exit , the pressure drops to either well below atmospheric pressure (LP Turbine) or at relatively lower pressure (HP & IP turbine). •  During turbine start up the gland seal steam has to be given at both the ends, so that condenser can be isolated from the atmosphere and Vacuum pulling can be started. • As the turbine starts taking load , steam at inlet side in HP & IP Turbine is higher & will try to come outside due to difference of pressure across the gland seals, at that point self sealing will be achieved. • In LP turbine, the sealing steam has to be maintained always because it is under vacuum at its exhaust sides.

26. TURBINE SEAL STEAM SYSTEM

27. FIXED POINTS OF 500 MW KWU TURBINE • TURBINE FIXED POINTS DESIGN OF SUPPORTS FOR THE TURBINE ON THE FOUNDATION HAS TO ALLOW FOR THE EXPANSION OF THE TURBINE DURING THERMAL CYCLING. • THE FOLLOWING COMPONENTS ARE THE FIXED POINTS FOR THE TURBINE : • THE HP, IP, LP TURBINE BEARING PEDESTALS • THE FRONT HORN SUPPORT OF HP AND IP TURBINE CASING. • THE LONGITUDINAL BEAMS OF THE LP TURBINE. • ROTOR AT THRUST BEARING IN BEARING PEDESTAL NO. 2

28. CASING EXPANSION • The bearing pedestals are anchored to the foundation by means of anchor bolts and are fixed in position. • The HP and IP turbines rest with their lateral support horns on the bearing pedestals at the turbine centre line level. The HP and IP casings are connected with the bearing pedestals by casing guides which establish the centreline alignment of the turbine casings. The axial position of HP and IP casings is fixed at the HP-IP pedestal. Thermal expansion of the casings originates from the fixed points. • The LP Turbine outer casing is held in place axially, at turbine end of longitudinal girder by means of fitted keys. Free lateral expansion is allowed. Centring of LP outer casing is provided by guides which run in recesses in the foundation cross beam. Axial movement of the casings is unrestrained. • when there is a temperature rise, the outer casings of the HP turbine expand from their fixed points towards Front pedestal. Casing of IP Turbine expand from its fixed point towards the generator. LP Casing expands from its fixed point at front end, towards the generator.

29. ROTOR EXPANSION • FIXED POINT OF ROTOR IS AT THRUST BEARING IN BEARING PEDESTAL NO. 2. • The thrust bearing is housed in the rear bearing pedestal of the HP turbine. The HP turbine rotor expands from the thrust bearing towards the front bearing pedestal of the HP turbine and the IP turbine rotor from the thrust bearing towards the generator. • The LP turbine rotor is displaced towards the generator by the expansion of the shaft assembly, originating from the thrust bearing.

30. DIFFERENTIAL EXPENSION DIFFERENTIAL EXPANSION OF A TURBINE = ROTOR EXPANSION – CASING EXPANSION The largest differential expansions of the HP and IP turbines occurs at the ends farthest from the thrust bearing. Differential expansion between the rotor and casing of the LP turbine results from the difference between the expansion of the shaft assembly, originating from the thrust bearing and the casing expansion, which originates from the fixed points on the LP turbine longitudinal beams.

31. AXIAL SHIFT • Axial shift on the Rotors comes due to two components • Direct Pressure Thrust: It is the axial thrust due the diff of the pressure X Area component across the moving stage blading and Discs. • Velocity Component: It is due to diff. of the velocity X Mass component across the moving stage blading. Total summation of all the above components leads to the Axial Thrust. • Axial Thrust is +ve if it is towards generator. • Axial Thrust is -ve if it is towards HPT front. • Sealing fins are also important component of balancing axial thrust. The Residual thrust is taken care by the Thrust pads. • Tripping Limits of Axial shift • Alarm +/- 0.5 mm. • Tripping +/- 1 mm.

32. TURBINE BEARING VIBRATION & BABBIT METAL TEMPERATURES

33. HPT FRONT BEARING PEDESTAL • Its function is to support the turbine casing and bear the turbine rotor. It houses the following components and instruments. • Journal bearing (10) • Hydraulic turning gear (7) • Main oil pump (2) • Hydraulic speed transducer (3) • Electric speed transducer (4) • Over speed trip (6) • Shaft vibration pickup (9) • Bearing pedestal vibration pick-up (8)

34. 500 MW Turbine Lube Oil system: MOT Room

35. LUBE OIL SYSTEM • LUBE OIL SUPPLY TO BEARINGS FOR LUBRICATION AND COOLING OF TURBINE, GENERATOR AND EXCITER BEARINGS • LUBE OIL ACTS AS A MOTIVE FORCE FOR HYDRAULIC BARRING GEAR DURING START UP AND SHUT DOWN

36. OIL SUPPLY SYSTEM

37. MOT OIL SUPPLY SCHEME

38. MOT OIL SUPPLY DATA

39. TURBINE BARRING GEAR SYSTEM • BARRING GEAR • HYDRAULIC OPERATED (LUB OIL) TURBINE MOUNTED ON THE SHAFT LOCATED IN THE FRONT BEARING PEDESTAL. • HAND BARRING GEAR ALSO PROVIDED IN BEARING PEDESTAL NO.3 TO ROTATE THE SHAFT BY HAND DURING EMERGENCY WHEN HYDRAULIC OPERATED BARRING GEAR IS NOT AVAILABLE. • PRIMARY FUNCTION OF THE BARRING GEAR IS TO ROTATE THE TURBO- GENERATOR ROTOR SLOWLY AND CONTINUOUSLY AT 75-80 RPM DURING START UP AND SHUT DOWN WHEN CHANGES IN ROTOR TEMPERATURE OCCUR. • WHEN TURBINE IS SHUT DOWN, COOLING OF ROTOR ELEMENTS IS REQUIRED AT SLOW SPEED TO AVOID DISTORTION OF ROTOR. BARRING GEAR IS USED TO KEEP THE ROTOR REVOLVING UNTIL THE TEMPERATURE CHANGES HAS STOPPED AND ROTOR HAS BECOME COOL (Max TEMPERATURE 120 deg centigrade). • DURING STARTING TURBO-GENERATOR ROTOR IS SLOWLY ROTATED TO HAVE A UNIFORM HEATING OF ROTOR.

40. CONTROL FLUID ROOM

41. TURBINE CONTROL FLUID SYSTEM • THROTTLE GOVERNING SYSTEM • SEPARATE OIL (FRF) IS USED AS CONTROL OIL. • TWO NOS. OF 4 STAGE CONTROL FLUID PUMP SUPPLIES OIL AT 8 BAR & 32 BAR FROM DISCHARGE LINES CONNECTED AFTER 1ST STAGE & 4TH STAGE. • HP CONTROL FLUID SYSTEM (32BAR) - DIRECT SUPPLY TO CONTROL VALVE SERVOMOTORS OF HP/IP TURBINE. • LP CONTROL FLUID SYSTEM (8 BAR) - SUPPLY TO HYDRAULIC CONTROL EQUIPMENT RACK, PROTECTIVE EQUIPMENT FOR TURBINE AND SERVOMOTORS OF NRV, ESV & IV.

42. HP-LP BYPASS SYSTEM • HP BYASS SYSTEM: It bypasses Main steam before HPT to the CRH line. • LP-BYPASS SYSTEM: It bypasses Steam from HRH line before IPT to the condenser thus bypassing both IPT & LPT. • To ensure operation of steam generator by maintaining a minimum circulation of steam flow, when turbine is not in service. It creates an alternate path bypassing the three turbine cylinders for the steam flow. • HP ‐LP Bypass system has the following advantages: • QUICK START UP OF THE UNIT • REHEATER PROTECTION DURING START – UP • PARALLEL OPERATION OF STEAM GENERATOR &TURBINE • HOUSE LOAD OPERATION • LIMITED SAFETY VALVE LIFTING DURING TRIP OUTS • DM WATER SAVING

43. MAIN TURBINE TESTS & TERMINOLOGIES • HORN DROP TEST: the loading of the casing on each corner is determined. It is taken on HP and IP Outer Casing. • BEARING FLOAT: It is the total axial movement of the Rotors between the working and the Non working Pads of the Thrust Bearing. • BUMP CHECK: It is Maximum total axial gap of the steam path of the turbine Cylinders . Normally carried out for HP& IP Cylinders. It is measured by moving the entire rotors from the zero position on either side.( Zero position is Rotor collar in the 50% float Position of the thrust Bearing in KWU Machines). • SWING CHECK is a measurement which shows the mating accuracy of the coupling faces of the two rotors coupled together. • ROLL CHECK (Centering)- It is the measurement of the Radial clearances between the Casing blades with the Rotor. • CATENARY: When rotors are resting in free condition on their bearings, there will be individual sags in them due to its dead weight and dimensions. Due to above the mating coupling faces of the rotors shall be at an angle. In this condition it is very difficult to couple the rotors. To align the coupling faces, the rotors are given vertical adjustment through bearing or pedestal adjustment so that they become parallel and coupling becomes easier. One rotor normally LP rotor is kept as MASTER. • MPI- MAGNETIC PARTICLE INSPECTION TEST- TO DETECT SURFACE CRACKS OF BLADES. • NFT- NATURAL FREQUENCY TEST- DETECTION OF CRACK & ITS LOCATION.

44. LOSSES IN STEAM TURBINES • Profile Loss: Due to development of boundary layers on blade surfaces. It is influenced by the factors like Reynolds number, surface roughness, exit Mach number and trailing edge thickness Mach number and trailing edge thickness. • Secondary Loss: Due to development of boundary layers on the casing and hub walls. The influence factors are similar to those for the profile loss. • Tip Leakage Loss: Due to clearance between rotor blades and casing wall as well as between stator blades and rotating hub. The extent of tip leakage depends on whether the turbine is impulse or reaction. Due to pressure drop across the moving blades of reaction turbine, they are more prone to tip leakages. • Disc Windage Loss: Due to fluid friction on the turbine disc surfaces as they rotate in a steam atmosphere. The result is a reduction in shaft power and an increase in kinetic energy and heat energy of steam. • Lacing Wire Loss: Due to flow blockage created by the presence o f lacing wires in long blade of LP stages. • Wetness Loss: Due to moisture entrained in the low pressure steam at the exit of LP turbine. The loss manifests in: firstly, a reduction in turbine efficiency due to energy absorption by the water droplets, and secondly, erosion of rotor blade leading edges in last stages. • Annulus Loss: Due to significant amount of diffusion between adjacent stages or where wall cavities occur between the fixed and moving blades. The extent of loss is greatly reduced at high annulus area ratios. if the extent of loss is greatly reduced at high annulus area ratios if the expansion of steam is controlled by a flared casing wall. • Leaving Loss: Due to kinetic energy of steam leaving the last stage of LP turbine. In practice, the steam slows down a bit after leaving the last blade, due to frictional losses. • Partial Admission Loss: Due to partial filling of steam, the flow between the blades is considerably accelerated causing a loss in power.

45. New 500 OR 525 MW Steam Turbines • New variant of 500 MW steam turbine introduced by BHEL – Reheat steam temperature raised from 537°C to 565°C – Flow paths of HP, IP and LP turbines redesigned – Advanced class blade profiles • Reduction of heat rate by 10 kcal/kWhr • Thermal performance 0.6% better than conventional cycle • New cycle adopted for NTPC Dadri, Simhadri, Ennore, Aravali, etc.