BHEL - Haridwar

VOCATIONAL TRAINING

REPORT

Balancing of turbine shaft by OSBT

(2008-2012)

Bachelor of Technology (Mechanical engg.)

S.C.R.I.E.T. MEERUT

Project Guide: Submitted by:

Mr. S. Haldar Devendar Kumar

(DGM)

Turbine

A steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and converts it into rotary motion. Its modern manifestation was invented by Sir Charles Parsons in 1884. It has almost completely replaced the reciprocating piston steam engine (invented by Thomas Newcomen and greatly improved by James Watt) primarily because of its greater thermal efficiency and higher power-to-weight ratio. Because the turbine generates rotary motion, it is particularly suited to be used to drive an electrical generator – about 80% of all electricity generation in the world is by use of steam turbines. The steam turbine is a form of heat engine that derives much of its improvement in thermodynamic efficiency through the use of multiple stages in the expansion of the steam, which results in a closer approach to the ideal reversible process.

Parsons turbine from the Polish destroyer ORP Wicher II

Types

Steam turbines are made in a variety of sizes ranging from small 1 hp (0.75 kW) units (rare) used as mechanical drives for pumps, compressors and other shaft driven equipment, to 2,000,000 hp (1,500,000 kW) turbines used to generate electricity. There are several classifications for modern steam turbines.

Steam Supply and Exhaust Conditions

These types include condensing, non-condensing, reheat, extraction and induction.

Non-condensing or backpressure turbines are most widely used for process steam applications. The exhaust pressure is controlled by a regulating valve to suit the needs of the process steam pressure. These are commonly found at refineries, district heating units, pulp and paper plants, and desalination facilities where large amounts of low pressure process steam are available.

Condensing turbines are most commonly found in electrical power plants. These turbines exhaust steam in a partially condensed state, typically of a quality near 90%, at a pressure well below atmospheric to a condenser.

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.

Casing or Shaft Arrangements

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.

Principle of Operation and Design

An ideal steam turbine is considered to be an isentropic process, or constant entropy process, in which the entropy of the steam entering the turbine is equal to the entropy of the steam leaving the turbine. No steam turbine is truly “isentropic”, however, with typical isentropic efficiencies ranging from 20%-90% based on the application of the turbine. The interior of a turbine comprises several sets of blades, or “buckets” as they are more commonly referred to. 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.

Turbine Efficiency

To maximize turbine efficiency, the steam is expanded, generating work, in a number of stages. These stages are characterized by how the energy is extracted from them and are known as impulse or reaction turbines. Most modern steam turbines are a combination of the reaction and impulse design. Typically, higher pressure sections are impulse type and lower pressure stages are reaction type.

Impulse Turbines

An impulse turbine has fixed nozzles that orient the steam flow into high speed jets. These jets contain significant kinetic energy, which the rotor blades, shaped like buckets, convert into shaft rotation as the steam jet changes direction. A pressure drop occurs across only the stationary blades, with a net increase in steam velocity across the stage.

Reaction Turbines

In the reaction turbine, the rotor blades themselves are arranged to form convergent nozzles. This type of turbine makes use of the reaction force produced as the steam accelerates through the nozzles formed by the rotor. Steam is directed onto the rotor by the fixed vanes of the stator. It leaves the stator as a jet that fills the entire circumference of the rotor. The steam then changes direction and increases its speed relative to the speed of the blades. A pressure drop occurs across both the stator and the rotor, with steam accelerating through the stator and decelerating through the rotor, with no net change in steam velocity across the stage but with a decrease in both pressure and temperature, reflecting the work performed in the driving of the rotor.

GAS TURBINE

A gas turbine, also called a combustion turbine, is a rotary engine that extracts energy from a flow of combustion gas. It has an upstream compressor coupled to a downstream turbine, and a combustion chamber in-between. (Gas turbine may also refer to just the turbine element.)

Energy is added to the gas stream in the combustor, where air is mixed with fuel and ignited. Combustion increases the temperature, velocity and volume of the gas flow. This is directed through a nozzle over the turbine's blades, spinning the turbine and powering the compressor.

Energy is extracted in the form of shaft power, compressed air and thrust, in any combination, and used to power aircraft, trains, ships, generators, and even tanks.

Theory of operation

Gas turbines are described thermodynamically by the Brayton cycle, in which air is compressed isentropically, combustion occurs at constant pressure, and expansion over the turbine occurs isentropically back to the starting pressure.

In practice, friction and turbulence cause:

1. Non-isentropic compression: for a given overall pressure ratio, the compressor delivery temperature is higher than ideal.

2. Non-isentropic expansion: although the turbine temperature drop necessary to drive the compressor is unaffected, the associated pressure ratio is greater, which decreases the expansion available to provide useful work.

3. Pressure losses in the air intake, combustor and exhaust: reduces the expansion available to provide useful work.

As with all cyclic heat engines, higher combustion temperature means greater efficiency. The limiting factor is the ability of the steel, nickel, ceramic, or other materials that make up the engine to withstand heat and pressure. Considerable engineering goes into keeping the turbine parts cool. Most turbines also try to recover exhaust heat, which otherwise is wasted energy. Recuperators are heat exchangers that pass exhaust heat to the compressed air, prior to combustion. Combined cycle designs pass waste heat to steam turbine systems. And combined heat and power (co-generation) uses waste heat for hot water production.

Mechanically, gas turbines can be considerably less complex than internal combustion piston engines. Simple turbines might have one moving part: the shaft/compressor/turbine/alternative-rotor assembly (see image above), not counting the fuel system.

More sophisticated turbines (such as those found in modern jet engines) may have multiple shafts (spools), hundreds of turbine blades, movable stator blades, and a vast system of complex piping, combustors and heat exchangers.

As a general rule, the smaller the engine the higher the rotation rate of the shaft(s) needs to be to maintain top speed. Turbine blade top speed determines the maximum pressure that can be gained; this produces the maximum power possible independent of the size of the engine. Jet engines operate around 10,000 rpm and micro turbines around 100,000 rpm.

Types of gas turbines

Aeroderivatives and jet engines

Diagram of a gas turbine jet engine

Airbreathing jet engines are gas turbines optimized to produce thrust from the exhaust gases, or from ducted fans connected to the gas turbines. Jet engines that produce thrust primarily from the direct impulse of exhaust gases are often called turbojets, whereas those that generate most of their thrust from the action of a ducted fan are often called turbofans or (rarely) fan-jets.

Gas turbines are also used in many liquid propellant rockets, the gas turbines are used to power a turbopump to permit the use of lightweight, low pressure tanks, which saves considerable dry mass.

Diagram of a high-pressure turbine blade

Amateur gas turbines

Increasing numbers of gas turbines are being used or even constructed by amateurs.

In its most straightforward form, these are commercial turbines acquired through military surplus or scrapyard sales, then operated for display as part of the hobby of engine collecting. In its most extreme form, amateurs have even rebuilt engines beyond professional repair and then used them to compete for the Land Speed Record.

The simplest form of self-constructed gas turbine employs an automotive turbocharger as the core component. A combustion chamber is fabricated and plumbed between the compressor and turbine sections. More sophisticated turbojets are also built, where their thrust and light weight are sufficient to power large model aircraft. The Schreckling design constructs the entire engine

from raw materials, including the fabrication of a centrifugal compressor wheel from plywood, epoxy and wrapped carbon fibre strands.

Like many technology based hobbies, they tend to give rise to manufacturing businesses over time. Several small companies now manufacture small turbines and parts for the amateur. Most turbojet-powered model aircraft are now using these commercial and semi-commercial microturbines, rather than a Schreckling-like home-build.

Auxiliary power units

Auxiliary power units (APUs) are small gas turbines designed for auxiliary power of larger machines, such as those inside an aircraft. They supply compressed air for aircraft ventilation (with an appropriate compressor design), start-up power for larger jet engines, and electrical and hydraulic power.

Industrial gas turbines for electrical generation

GE H series power generation gas turbine. This 480-megawatt unit has a rated thermal efficiency of 60% in combined cycle configurations.

Industrial gas turbines differ from aeroderivative in that the frames, bearings, and blading is of heavier construction. Industrial gas turbines range in size from truck-mounted mobile plants to enormous, complex systems. They can be particularly efficient—up to 60%—when waste heat from the gas turbine is recovered by a heat recovery steam generator to power a conventional steam turbine in a combined cycle configuration. They can also be run in a cogeneration configuration: the exhaust is used for space or water heating, or drives an absorption chiller for cooling or refrigeration. A cogeneration configuration can be over 90% efficient. The power turbines in the largest industrial gas turbines operate at 3,000 or 3,600 rpm to match the AC power grid frequency and to avoid the need for a reduction gearbox. Such engines require a dedicated enclosure, both to protect the engine from the elements and the operators from the noise.

Radial gas turbines

Main article: Radial turbine

In 1963, Jan Mowill initiated the development at Kongsberg Våpenfabrikk in Norway. Various successors have made good progress in the refinement of this mechanism. Owing to a

configuration that keeps heat away from certain bearings the durability of the machine is improved while the radial turbine is well matched in speed requirement.

Advances in technology

Gas turbine technology has steadily advanced since its inception and continues to evolve; research is active in producing ever smaller gas turbines. Computer design, specifically CFD and finite element analysis along with material advances, has allowed higher compression ratios and temperatures, more efficient combustion and better cooling of engine parts. On the emissions side, the challenge in technology is increasing turbine inlet temperature while reducing peak flame temperature to achieve lower NOx emissions to cope with the latest regulations. Additionally, compliant foil bearings were commercially introduced to gas turbines in the 1990s. They can withstand over a hundred thousand start/stop cycles and eliminated the need for an oil system.

Advantages and disadvantages of gas turbine engines

Advantages of gas turbine engines

Very high power-to-weight ratio, compared to reciprocating engines; Smaller than most reciprocating engines of the same power rating.

Moves in one direction only, with far less vibration than a reciprocating engine.

Fewer moving parts than reciprocating engines.

Low operating pressures.

High operation speeds.

Low lubricating oil cost and consumption.

Disadvantages of gas turbine engines

Cost is much greater than for a similar-sized reciprocating engine since the materials must be stronger and more heat resistant. Machining operations are also more complex;

Usually less efficient than reciprocating engines, especially at idle.

Delayed response to changes in power settings.

These disadvantages explain why road vehicles, which are smaller, cheaper and follow a less regular pattern of use than tanks, helicopters, large boats and so on, do not use gas turbine engines, regardless of the size and power advantages imminently available.

SPECIFICATIONS OF MACHINES AVAILABLE IN BLOCK-III:

Vertical Boring Machine :

Max diameter of work piece accommodated :10000mm to 12500mm Max height of work piece :5000mm Diameter of table :8750mm Max travel of vertical tool head RAM slides :3200mm Max travel of vertical tool heads from centre of

Table :5250mm Max weight of work piece :200 T

For N<=6rpm;100T for any speed Diameter of boring spindle of combined head :160mm Travel of boring spindle :1250mm Taper hole of boring spindle :100metric

Centre Lathe :(Biggest of all BHEL)

Max diameter over bed :3200mm Max diameter over saddle :250mm Length between centers :16m Max weight of work piece :100 T Spindle bore :96mm

CNC Lathe :

Manufacturer: Safop, Italy Swing over carriage :3500mm Centre distance :9000mm Weight capacity :120 T Spindle power :196KW External chucking range :250-2000mm Hydrostat steady range :200-1250mm Max spindle rpm :200 CNC system :SINUMERIK 840D

CNC Indicating stand :

Manufacturer : Heinrich Georg, Germany

Turning diameter :5.3m Turning length :15m Weight capacity :160 T

CNC Vertical Borer :

Manufacturer : M/S Pietro Carnaghi, Italy

Machine model :AP 80TM-6500 Table diameter :6500mm Max turning diameter :8000mm Min boring diameter :660mm Max height for turning and milling :7000mm Table Speed :0.2-50 rpm Table load capacity :200 T Milling spindle speed :3.4-3000 rpm at 40KW Spindle taper :BT 50 CNC system :SINUMERIK 840D

CNC Facing Lathe : KH-200-CNC

Swing over bed :2300mm Swing over carriage :1800mm Max distance between faced plate and carriage :2000mm Max weight of job held in chuck :6000kg Face plate diameter :1800mm Spindle speed :1.4-400rpm Main spindle drive :95.5KW

Step boring Machine :

Max boring diameter :2500mm

Min boring diameter :625mm Table :4000mmx4000mm Max weight of job :100 T Headstock travel :4000mm

Double Column Vertical Borer :

Table diameter :4000mm Max travese of cross rail :4250mm Max weight of work piece :4200mm Max weight of job :50 T

CNC Skoda Horizontal Borer :

Spindle diameter :200mm Taper spindle :BT 50 RAM size :450x450mm RAM length :1600mm Spindle length :2000mm Headstock :5000mm Table :4000x3500mm CNC system :SIMENS 850mm Job : I.P. Outer

Horizontal Borer : LSTG 8006

Spindle diameter :250mm Height of machining bed :600mm Max boring depth with spindle :2000mm Max extension of RAM :1600mm Width of bed guide ways :2500mm Actual length of headstock with vertical lift :2150mm Actual length of column horizontal feed :15000mm Lowest position of spindle axis upon bed guideways:1475mm Machine weight with electrical equipments :140 T Height of machine :10.3m

CNC Lathe : 1-120

Manufacturer : Ravensburg

Main spindle bore :150mm Distance between centers :12m Turning diameter over bed cover :1400mm Turning diameter over carriage :1100mm Workpiece weight unsupported :4000kg

Workpiece weight between centers :20 T

Centre Lathe : 1-23

Manufacturer : K3TC, USSR

Max diameter over bed :1250mm Max diameter over saddle :900mm Length between centers :6300mm Max weight of work piece :25 T Spindle bore :80mm Machine wattage :55KW

Horizontal Boring Machine : 1-28

Diameter of spindle :150mm Working surface of table :2250x1250mm Max travel of table :1200mm Max vertical travel of headstock :2000mm

Horizontal Boring Machine :

Boring spindle taper :BT50 Boring spindle diameter :160mm Headstock vertical travel :3000mm Longitudinal RAM travel :700mm Longitudinal spindle travel :1000mm Column cross travel :10m Rotary table travel :3000mm Table load :40 T

Horizontal Boring Machine : 1-11

Boring spindle internal taper material :200 Boring spindle diameter :320mm Max spindle travel :2500mm Vertical head travel :6000mm Transverse column travel :6000mm Max longitudinal column travel :800mm Machine wattage :90KW

Double Column Rotary Table Vertical Borer :

Max diameter of work piece accommodated :10m/12.5m Max height of work piece accommodated :5m Diameter of table :8.75m Max travel of vertical tool head RAM slides :3.2m Max travel of vertical tool head from centre of table :5.25m Max weight of work piece :200T for N<=8rpm

;100T for any speed Diameter of boring spindle of combined head :160mm Travel of boring spindle :1250mm Taper hole of boring spindle :100 metric

Horizontal borer : 1-2

Spindle diameter :220mm Working surface :8100 x 5000mm Max vertical travel :3mm Max transverse travel of column :6m Max longitudinal travel of column :6m Max longitudinal travel of spindle :1.8m

CNC Lathe : 2-360

Manufacturer : Hoesch

Max load :320 T Max length between centers :18m Swing over bed :3.2m

Horizontal Borer : 2-198

Spindle diameter :220mm Max vertical travel :3m Max transverse travel of column :6m Max longitudinal travel of column :6m Max longitudinal travel of spindle :1.8m Working surface :1800x500mm

Creep Feed Grinding Machine :

Diameter of job :2m Job height :2.4m

Table rpm :10rpm(max) Table diameter :2050mm Swing diameter :2500mm CNC control :SIEMENS-3GG

Broaching Machine :

Broaching capacity :32 T Broaching stroke :10.3m Broaching slide width 1500mm Broaching specific cutting stroke :1.25m/min Broaching specific return stroke :60m/min Max diameter of disc :2300mm Max move of table :600mm Helix angle/skew angle setting :+45/-45 Cone angle :0-20

CNC Lathe :

Manufacturer : Innse Berardi, Italy Swing over carriage :1500mm Swing over bed :2000mm Capacity :30 T Cost :16 crore CNC system :SINUMERIK 840D

Over Speed Balancing of Turbines :

Main features :

Type of pedestials :DH 90/DH 12 Rotor weight :Min 4 MT, Max 320 MT Rotor diameter :Max 6900mm Rotor journal diameter :Min 250mm,Max 950mm Bearing centre distance :Min 3000mm,Max 15700mm Balancing speed :180-3600rpm Min vibration limit :1 micron Max vacuum :1 torr

Tunnel Features :

Tunnel length :19000mm

Tunnel diameter :6900mm Max thickness of tunnel :2500mm Steel plate thickness :32mm Cost of balancing equipment(FE) :444 lakhs Total cost of balancing tunnel :770 lakhs

Main Features of Drive :

Drive motors (2 no.) :950V DC, 500rpm,3.5 MW each Total drive power :7 MW(2x3.5)

MG set of Drive :

Synchronous motors :11 KV,9MW,50Hz,500rpm DC Generator (2 no.) :950V,500rpm,3.8MW each

HOW IT WORKS

STEAM FLOW THROUGH STEAM TURBINE

Modernization of Facilities:

CNC Lathe for LP Rotor from SAFOP, ITALY CNC Horizontal Boring machine for machining of casing from PAMA, ITALY CNC Indicating Stand for LP Rotor Blade machining from GEORG, GERMANY CNC Fir Tree Root Milling machine CNC Gantry Milling machine

Major Facilities for New Turbine Shop:

CNC V Borer-Table diameter-7500mm CNC V Borer-Table diameter-4000mm CNC H Borer Spindle Diameter-200mm,160mm CNC Lathe capacity-120 T,80T CNC Fir Tree Root Milling machine CNC Gantry Milling machine

Highlights:

Imported Substitutions : Hybrid burner for gas turbine E ring for gas turbine Deep hole drilling in HP outer casing supplied by Machine Shop, CFFP

Process Improvement : Slitting of casing, thrust rings, GT rings on Band Saw milling machine, thus

saving the time on critical machines such as Ram Borers Using KOMET drilling systems, the productivity in joint plane drilling of

casing and LP Rotors has increased Seeing the congestion on KOOP milling machine, a new work center

machine called RAMBHOR machine(No. 2473

Tool Brands:

Widia Sandwick Seco Isear Addisson Guhring Indian tools Mitutoyo

Tool Instruments:

Die ring spanner Hack saw frame Burr cutter Solid tap (carbide) Hand tap

Grinding Cutters:

Combination cutter-140x40mm Fillet cutter-160x32mm Hand mill cutter End mill cutter Internal profile cutter Shell end mill cutter-63x80mm Ball nose Slab mill

500 MW Steam Turbine:

HP Turbine: Module :H30-100-2 Steam Pressure :170Kg/sq.cm Steam temperature :537 deg.cel Reheating temperature :537 deg.cel Weight :86400 Kg Length of Rotor :4.61m Height :2.15m

LP Turbine: Module :N30-2x10sq.m Weight :3.5 T Length of Rotor :8.7m Width :10.7m Height :4.6m

IP Turbine: Length :4.425m Width :5m Height :4.8m Steam pressure :41Kg/sq.cm Steam temperature :537 deg.cel

Gas Turbine V 94.2:

ISO 159MW Weight :200 T Length :10m Breadth :2.5m Temperature of hot gas in turbine :1060 deg.cel Type of burner :Hybrid Burner

Milling Cutters:

1) Side end face milling cutter2) Interlocking side and face milling cutter3) Shell end mill cutter4) Metal slitting saw5) Single angle milling cutter

6) Double unequal angle milling cutter7) Double equal angle milling cutter8) Keyway milling cutter9) Milling cutter for chain wheels10) Single corner rounding milling cutter11) Convex milling cutter12) Concave milling cutter13) T slot milling cutter with plane parallel shank14) T slot milling cutter with Morse taper shank having tapered end15) Cylindrical milling cutter16) Slot milling cutter with parallel shank17) End mill with parallel shank18) Ball nosed end mill with parallel shank19) Flat end tapered die sinking cutter with plane parallel shank20) Ball nosed taper die sinking cutter with plane parallel shank21) Slot milling cutter with morse tapered shank having tanged end22) End mill with morse tapered shank having tanged end23) Ball nosed end mill with morse tapered shank having tanged end24) Flat end tapered die sinking cutter with morse tapered shank having tapped end25) Ball nosed tapered die sinking cutter with morse tapered shank having tapped end26) Slot milling cutter with morse tapered shank having tapped end27) End mill morse tapered shank having tapped end28) Ball nosed mill morse tapered shank having tapped end29) Roughing end mill with parallel shank finishing type 30) Roughing end mill with parallel shank roughing type 31) Slot milling cutter with 7/24 taper shank 32) End mill with 7/24 taper shank33) Ball nosed end mill with 7/24 taper shank34) Woodruff key slot milling cutter with parallel shank 35) Screwed shank slot drill

Major Components of Steam Turbine:

LP Rotor LP Inner Casing Upper Half LP Inner Casing Lower Half LP Outer Casing Upper Half LP Outer Casing Lower Half IP Rotor IP Inner Casing Upper Half IP Inner Casing Lower Half

IP Outer Casing Upper Half IP Outer Casing Lower Half HP Rotor HP Inner Casing Upper Half HP Inner Casing Lower Half HP Outer Casing Upper Half HP Outer Casing Lower Half Diffuser GBC (Guide Blade Carrier) IVCV (Intercept Valve Control Valve) ESVCV (Emergency Stop Valve Control Valve)

Auxiliary Parts of Steam Turbine:

1) Valve Seal2) U-Ring3) Piston Rod4) Base Plate5) Sealing Ring6) Liner7) Guide Ring8) Valve Cover9) Guide Blades :

Fixed Blades Moving Blades

10) Support11) Bearing12) Bearing Shell13) Angle Ring14) Sleeve15) Pin Taper (25x140)16) Journal Bearing Shell17) Casing18) Guide bush19) Piston (500MW)20) Valve Cone21) Yoke22) Mandrel 23) Support Ring24) Thrust Ring25) Adjusting Ring

26) Shaft Sealing Cover

Auxiliary Parts of Gas Turbine:

1) Spacer Ring2) Oil Guard Ring V 94.23) Oil Projecting Ring4) Plate5) Coupling Bolt6) Inlet Shell

Types of Blades:

T2 blades T4 blades TX blades 3DS blades F- blades GT-Compress blades Brazed blades Russian design blades Z-Shroud blades Compressor blades (Sermental coated) LP Moving blade 500MW

New Blade Shop:

First Generation Blades : T2 Profile Blades

Cylindrical Profile Blades (1970)

Second Generation Blades : T4 Profile Blades

Cylindrical Profile Blades ( late 1980)

1% Gain in Stage Efficiency over T2 Profile Blades

TX Profile Blades Cylindrical Profile Blades ( late 1990)

Gains :

Reduces Profile Losses

0.2% Gain in Stage Efficiency over T4 Profile Blades

Applications :

Middle Stage Of H.P. and I.P Turbine

Initial Stage of L.P. Turbine

3DS Blades :

Gains : Reduces Secondary Flow Losses 0.5 – 1.0% Gain in Stage Efficiency over TX Profile Blades

Application :

Initial Stage of H.P. and I.P Turbine

F- Blades

Gains :

Reduces Indirect Flow Losses 0.5 – 1.0% Gain in Stage Efficiency over TX Profile Blades

Applications :

Rear Stage of H.P. and I.P Turbine

Middle Stage of L.P. Turbine

Sequential operation for machining of TX blades:

Operation Machine

1) Blanking2) Rhomboid machining

Band sawCNC rhomboid machine cell

3) Removal of tech allowance/parting off band saw4) Root machining CNC high speed root machining5) Profile and expansion angle(internal and

external)CNC heavy/light duty machine or CNC profile and fillet machining center

6) Shroud copying CNC heavy/light duty machine7) Taper grinding CNC creep feed grinding machine8) Grinding and polishing Polishing machine9) Final fitting of blades -10) Vibro finishing of blades Vibro finishing equipment11) Final inspection -

Sequential operation for machining of 3DS and F blades:

Operation Machine

1) Blanking Band saw

2) Preparation of technological ends for work piece holding

CNC machining center

3) Complete blade machining(with normal shroud/Z shroud)

CNC 5 axis machining centre

4) Inspection 3D CMM5) milling off technological ends at root and shroud

radius machiningCNC machining centre

6) Fitting -7) vibro finishing for surface finishing

improvementVibro finishing equipment

8) Inspection -

Number of advance design blades:

Blades 250MW 500MW TX Profile blade 10390 6820F and 3DS blade 3100 2852Free standing blade 224 252

Over Speed Balancing of Turbines :

Main features :

Type of pedestals :DH 90/DH 12 Rotor weight :Min 4 MT, Max 320 MT Rotor diameter :Max 6900mm Rotor journal diameter :Min 250mm,Max 950mm Bearing centre distance :Min 3000mm,Max 15700mm Balancing speed :180-3600rpm Min vibration limit :1 micron Max vacuum :1 torr

Tunnel Features :

Tunnel length :19000mm Tunnel diameter :6900mm Max thickness of tunnel :2500mm Steel plate thickness :32mm Cost of balancing equipment(FE) :444 lakhs Total cost of balancing tunnel :770 lakhs

Main Features of Drive :

Drive motors (2 no.) :950V DC, 500rpm,3.5 MW each Total drive power :7 MW(2x3.5)

MG set of Drive :

Synchronous motors :11 KV,9MW,50Hz,500rpm DC Generator (2 no.) :950V,500rpm,3.8MW each

Rigid Rotors : Rigid rotors are those rotors when it can be corrected in any two (arbitrary selected) planes and after these correction, its unbalance does not significantly exceed the balancing tolerance (relative to the shaft axis) to any speed upto maximum service speed when running under conditions approximately close of the final supporting system.

Flexible Rotors: The rotor is not specifically define due to static deflection.

Provision for correction plane: The exact number of axial location along the rotor that are needed depends some extent on the particular balancing procedure. If the operating speed of the rotor exceeds the nth critical speed at least (n+2) corrected planes (transverse to the rotor axis) are likely to be needed along the rotor.

GENERAL: ISO says balancing is a procedure by which the mass distribution of a rotor is checked and if necessary, adjusted in order to ensure that the vibrations on the supporting bearing at a frequency corresponding to the operations are within specified limits. This is done to avoid damage to bearings, housing and foundations and to minimize the fatigue stresses on the rotor. In the existing facility it is carried out on hard bearing balancing machine type DH90/DH12 on completely assembled, rotors installed in technological bearing on rotor journals or using a stub shaft, if necessary technological bearing are also of antifriction (sleeve type) and incorporate of many features of original bearing. Bearing is carried out by consecutive compensation below and above critical speed and its rated speed to bring down the vibrations within the specified limits.

Brief Layout The rotors are assembled on the bogle pedestal and it is then driven into the overspeed and the balancing tunnel which can be evacuated to a high degree of vaccum upto 2 torr. Vibration are picked up through electro-magnetic pick up mounted on the pedestal and the readings are displayed on the instrument installed in the control room. The intelligence about the various parameters e.g. vibrations bearing temperature, tunnel temperature etc. are carried out to the instrument mounted in the control room trough cable passing through special vaccum penetration system located in the rear wall of the tunnels. The rotors is driven through a drive system consisting of 2 D.C. motors of 3.5 MW each connected in tendem a 1/4.5/8.9 step gear box and a intermediate shaft. The drive system is coupled to the rotor through a universal joint cardon shaft. The speed of the motor can be regulated from about 2 rpm to 500 rpm and of or rotor from 10 rpm to 4450 rpm.The power to the motor is fed through an MG set consisting of a 9 MW synchronous motor and 2 D.C. generators of 4 MW each.There are two lubrication system, atmospheric oil system providing oil to MG set and drive system and the vaccum oil system providing oil to the rotor bearing house in balancing pedestal

in the tunnel and oil in water cooled.

Balancing ProcedureAssembly of Rotor: The distance of the boggle pedestal is adjusted as the supporting journals to the journal center line distance of the rotor. The continuity of the RTD’s of bearing should be checked by a Q.C. before these are mounted on the pedestal. The rotor is then placed in the balancing machine pedestal with the help of special lifting tackle and the assembly is done as per drawing. The oil gaps between the rotor journal and the side/top of the bearing shall be as per drawing. The side gap of the bearing, alignments of pedestal and fitting of oil catcher should be checked before placing the upper half of the bearing bodies care must be taken to ensure that the dowel pin of the top cover of both the bearing is set in the right position. The required no. of correct balancing weights (approx.30% of the total periphery of each groove) should be fixed by assembly with section in the grooves provided in the rotor for balancing to avoid any mismatching of these weights at a later stage, rotor will then be handed over by incharge assembly section to O.S.B.T. incharge. The balancing pedestal along with the rotor will be driven into the balancing tunnel by means of a hydraulic electric boggle mechanism. The balancing pedestals are placed in a suitable position near the rear wall of the tunnel and the boggle is driven out. The rotor shall be aligned with a main drive by tightening the special pre-adjusted wedges provided on sides of each pedestal. Rotor is mounted to the drive using a cardon shaft of suitable torque value. To ease the coupling of the rotor to the cardon shaft, the intermediate shaft can be moved forward or reverse upto maximum distance of 20 mm from its mean position. Pedestal are secured to the machine bases in the tunnel in horizontal as well as vertical direction by means of a bolts provide for this purpose.

Preparation for Balancing After securing of the pedestal and connection of the rotor with the drive system the lubricating oil pipes, jacking oil pipes and drain oil pipes should be connected. Lubricating oil should be started to the pedestal bearings and flushing main be carried out for couple of hours. During flushing the rotor may be jacked a few times and the rotor lifts at both the pedestal are to be checked by means of a dial gauge. The rotor then can be run at a about 150 rpm for a few minutes (without any vaccum) and observed visually. It should be checked that there is no abnormal sound and no leakage of oil etc. after these close the rear wall and ensured that no loose things. The lights of the tunnel and the power supply to tunnel hoist and jib crane. The tunnel evacuation now started by vaccum pump sets first for the pedestal oil system and there after the main tunnel vaccum pump sets and then for the intermediate shafts. After attaining vaccum in the tunnel the rotor can be run upto a suitable speed below first critical speed at which vibrations do not become excessive (normally a vibration velocity of 10-12 mm/sec) may not be exceeded during the process of entire balancing.Critical speed range where ever it is appearing should be crossed over quickly. Reading of correction weights are to be noted down and rotor may be stopped. After stopping the rotor the correction planes shown in correction planes in low rpm(400-500 rpm) in a b-c mode are put

directly in two side correction planes at required angle as indicated by measuring instruments, either in polar form or in co-ordinate form. After correction of unbalance for the first critical speed, it should be impossible the rotor speed beyond the first critical speed without subjected to rotor to any excessive level of vibration at the first critical speed. Rotor should now be run at second balancing speed. Unbalance correction should be done using a ‘couple weight’ a pair of weight one in each plane of rotor and with an angular displacement of 1800. This process is to be continued till we get a low value of vibration at 3000 rpm. After achieving sufficiently low vibrations at the rated speed the rotor can now be over-speeded. Before the over-speeding run, the rotor should be checked that no part in the rotor show any sign of looseness, there is no excessive leakage of oil and temperature is within limits.Now rotor over-speed (3360/3600rpm max 3750) and retained there for two minutes or as specified. After over-speeding the rotor is stopped and thoroughly checked for any part of the rotor having become loose specially the locking blades. After achieving the vibration within the specified limits a couple of runs will be carried out to improve the balance quality. After the balancing is over the position of the weights placed in different correction planes will be noted with reference to the clocked punched on the rotor/rotor coupling hole. Rotor should be disconnected from the drive system and the lubricating pipes, jacking oil pipes etc. will be disconnected from pedestal. Evaluation of Unbalance: All rotors in OSBT are balanced at the rated speed and the evaluation of unbalance is by means of vibration measurement at rated speed. Following information are taken-

a. Vibration level at operating speed.b. Position of correction weights with respect to the clocked punched on the rotor shaft.c. Rpm and duration of over-speed test.