BHARAT HEAVY ELECTRICALS STEAM TURBINE

BHARAT HEAVY ELECTRICALSBHARAT HEAVY ELECTRICALS
LIMITEDLIMITED
BHOPAL
SUMMER INDUSTRIAL TRAINING
Department: STEAM TURBINE MANUFACTURING (STM)
Under The Guidance Of :
Shri. D.D. Pathak, AGM,STM
From: 13th june to 2nd July 2011
Submitted By:
ASHEESH TYAGI
Maulana Azad National Institute Of Technology (MANIT)
Bhopal
Mechanical Engineering
Scholar No: 081116084

STEAM 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.
History
The first device that may be classified as a reaction steam turbine was little more
than a toy, the classic Aeolipile, described in the 1st century by Hero of
Alexandria in Roman Egypt. A thousand years later, the first impact steam
turbine with practical applications was invented in 1551 by Taqi al-Din in Ottoman
Egypt, who described it as a prime mover for rotating a spit. Similar smoke
jacks were later described by John Wilkins in 1648 and Samuel Pepys in 1660.
Another steam turbine device was created by Italian Giovanni Branca in 1629.
The modern steam turbine was invented in 1884 by the Englishman Sir Charles
Parsons, whose first model was connected to a dynamo that generated 7.5 kW of
electricity. Parson's steam turbine, making cheap and plentiful electricity possible
and revolutionising marine transport and naval warfare, the world would never be
the same again.. His patent was licensed and the turbine scaled-up shortly after
by an American, George Westinghouse. A number of other variations of turbines
have been developed that work effectively with steam. The de Laval
turbine (invented by Gustaf de Laval) accelerated the steam to full speed before
running it against a turbine blade. This was good, because the turbine is simpler,
less expensive and does not need to be pressure-proof. It can operate with any
pressure of steam. It is also, however, considerably less efficient. The Parson's
turbine also turned out to be relatively easy to scale-up. Parsons had the

satisfaction of seeing his invention adopted for all major world power stations.
The size of his generators had increased from his first 7.5 kW set up to units of
50,000 kW capacity. He knew that the total output from turbo-generators
constructed by his firm C._A._Parsons_and_Company and by their licensees, for
land purposes alone, had exceeded thirty million horse-power.. Within Parson's
lifetime the generating capacity of a unit was scaled-up by about 10,000 times.
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, noncondensing, reheat, extraction and
induction.
Noncondensing 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.
Extracting type turbines are common in all applications. In an extracting type
turbine, steam is released from various stages of the turbine, and used for
industrial process needs or sent to boiler feedwater heaters to improve overall
cycle efficiency. Extraction flows may be controlled with a valve, or left
uncontrolled.
Induction turbines introduce low pressure steam at an intermediate stage to
produce additional power.
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.

Turbine Efficiency
Schematic diagram outlining the difference between an impulse and a
reaction turbine
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.
As the steam flows through the nozzle its pressure falls from steam chest
pressure to condenser pressure (or atmosphere pressure). Due to this relatively
higher ratio of expansion of steam in the nozzle the steam leaves the nozzle with
a very high velocity. The steam leaving the moving blades is a large portion of
the maximum velocity of the steam when leaving the nozzle. The loss of energy
due to this higher exit velocity is commonly called the "carry over velocity" or
"leaving loss".
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.

Steam Turbine:
DESCRIPTION:
Construction, STEAM FLOW
The Turbine is a tandem compound machine with separate HP,OP and LP
sections.The HP section being a single flow cylinder abd IP and LP sections
double flow cylinders.The Turbine Rotors and the generator rotors are connected
by rigid couplings.
The HP turbine is throttle controlled.The Initial steam is admitted ahead of the
blading via 2 main stop and control valve combinations.A swing check valve is
installed in the line leading from HP turbine exhaust to the reheater to prevent hot
steam from reheater flowing back into HP turbine.
The Steam coming from reheater is passed to the IP turbine via 2 reheat stop
and control valve combinations.Cross around pipes connect IP and LP
cylinders.Connections are provided at several points of the turbine for feedwater
extraction purposes.
HP TURBINE, BARREL TYPE CASING
The outer casing of the HP turbine is of the barrel type and has neither an axial
nor radial flange.This prevents mass concentration which would have caused
high thermal stresses.The Inner Casing is axially split and supported so as to be
free to move in response of thermal expansion.The Barrel Type casing permits
flexibility of operation in the form of short startup times and a high rate of change
of load even at initial steam conditions.

IP TURBINE
The IP turbine section is of singleconstruction with horizontal split casings.The
inner casing carries the stationary blading.The Reheated steam enters the inner
casing from top and bottom.The provision of an Inner Casing confines high
steam inlet conditions to the admission section of this casing.
LP TURBINE
The Casing of double-flow LP cylinder is of three shell design.The shells are
horizontally split and are of rigid welded construction.The innermost shell,which
carries the first rows of stationary blades ,is supported so as to allow thermal
expansion within the intermediate shell.Guide blade carriers,carrying the
stationary blade rows are also attached to the intermediate shell.
BEARINGS
The HP rotor is supported on two bearings,a journal bearing at its front end,and a
combined journal and thrust bearing immediately next to the coupling to the IP
rotor. The IP and LP rotors have a journal b earing each at rear end.The
combined journal and thrust bearing incorporates a journal and a thrust bearing
which takes up residual thrust from both directions.
The Bearing pedestals are anchored to the foundation by means of anchor bolts
and are fixed by position,
The HP and IP turbines rest with their lateral support horns on the bearing
pedestals at the turbine centerline level.
The Axial position of HP and IP casings is fixed at the support brackets on HP-IP
bearing pedestals.
The Following components forms the fixed points for the turbine:
1.The HP,IP and LP turbine bearing pedestals
2.The horn supports of the HP and IP turbine at HP-IP Pedestals

3.At the middle of longitudinal girder of the LP Turbine
4.The Thrust Bearing in the HP turbine rear bearing pedestals
CASING EXPANSION
Centring of LP outer casing is provided by guides which run in recesses in the
foundation cross beam. Axial movement of casings is unrestrained.
Hence,when there is temperature rise,the outer casing of the HP turbine expand
from their from their fixed points towards front pedestals.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.
Rotor Expansion
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 generatorby the expansion of the
shaft assembly ,originating from the thrust bearing.
DIFFERENTIAL EXPANSION
Differential expansion between rotors and casings results from the difference
between the expansion of rotor and casing originating from the HP-IP pedestal.
Differential expansion between rotor and casing of the IP turbine results from the
difference between the expansion of the shaft assembly, originating from thrust
bearing and casing expansion ,which originates from the fixed points on the LP
turbine longitudinal beams.

SHAFT SEAL and BLADE TIP SEALING
All shaft seals,which seal the steam in the casing against atmosphere,are axial-
flow type.They consists of a large number of thin seal strips which,in the HP and
Ip turbines are caulked alternately into grooves in the shafts and the surrounding
seal rings.
VALVES
The HP turbine is fitted with2 main stop and control valves.The main stop valves
are spring action single seated valves,the control valves,also of single seat
design ;the control valves;also of single-seat design,have diffusers to reduce
pressure losses.
The Ip turbine has 2 reheat stop and control valves.The reheat stop valves are
spring action single stop valves.The control valves;also spring loaded ,have
diffusers.
The reheat stop and control valves are supported free to move in response tto
thermal expansion on the foundation cover plate below the operating floor and in
front of the turbine generator unit.
TURBINE CONTROL SYSTEM
The Turbine has an electrohydraulic control system.An electric system measures
spped and output and controls them by controlling the control valve hydraulically
via an electrohydraulic converter.
The linear power frequency droopcharacteristic can be adjusted in fine steps
even when the turbine is running

TURBINE MONITORING SYSTEM
In addition to measuring and display instruments for pressure,temperatures,valve
lifts and speed ,the monitoring system also includes following parameters :
1.Rotor expansion measured at the rear bearing pedestal of LP turbine.
2.Axial Shift measured at the HP-IP pedestal
3.Bearing pedestal vibration
4.Shaft vibration measured at all turbine bearings.
OIL SUPPLY SYSTEM
A common oil supply system lubricates and cools the bearings.The main oil
pump is driven by the turbine shaft and draws oil from the main oil tank.Auxiliary
oil pumps maintain the oil supply on start-up and shutdown, during turning gear
operation and when the main oil supply is faulted.
A jack oil pump forces high pressure oil under the shaft journals to prevent
boundary lubrication during turning gear operation.The Lubricating and cooling oil
is passed through oil coolers before entering the bearings.

Working Of A STEAM TURBINE:
Introduction
A steam turbine is a mechanical device that converts thermal energy in
pressurised steam into useful mechanical work. The original steam engine which
largely powered the industrial revolution in the UK was based on reciprocating
pistons. This has now been almost totally replaced by the steam turbine
because the steam turbine has a higher thermodynamic efficiency and a lower
power-to-weight ratio and the steam turbine is ideal for the very large power
configurations used in power stations. The steam turbine derives much of its
better thermodynamic efficiency because of the use of multiple stages in the
expansion of the steam. This results in a closer approach to the ideal reversible
process.
Steam turbines are made in a variety of sizes ranging from small 0.75 kW units
used as mechanical drives for pumps, compressors and other shaft driven
equipment, to 1,500,000kW turbines used to generate electricity. Steam turbines
are widely used for marine applications for vessel propulsion systems. In recent
times gas turbines , as developed for aerospace applications, are being used
more and more in the field of power generation once dominated by steam
turbines.
Steam Turbine Principle
The steam energy is converted mechanical work by expansion through the
turbine. Th expansion takes place through a series of fixed blades (nozzles) and
moving blades each row of fixed blades and moving blades is called a stage.
The moving blades rotate on the central turbine rotor and the fixed blades are
concentrically arranged within the circular turbine casing which is substantially
designed to withstand the steam pressure.
On large output turbines the duty too large for one turbine and a number of
turbine casing/rotor units are combined to achieve the duty. These are generally

arranged on a common centre line (tandem mounted) but parallel systems can
be used called cross compound systems.
Impulse Blading
The impulse blading principle is that the steam is directed at the blades and the
impact of the steam on the blades drives them round. The day to day example of
this principle is the pelton wheel.ref Turbines.
In this type of turbine the whole of the stage pressure drop takes place in the
fixed blade (nozzle) and the steam jet acts on the moving blade by impinging on
the blades.
Blades of an impulse turbine
Velocity diagram impulse turbine stage
z represents the blade speed , V r represents the relative velocity, V wa & V wb-
represents the tangential component of the absolute steam in and steam out
velocities
The power developed per stage = Tangential force on blade x blade

Reaction Blading
The reaction blading principle depends on the blade diverting the steam flow and
gaining kinetic energy by the reaction. The Catherine wheel (firework) is an
example of this principle. FOr this turbine principle the steam pressure drop is
divide between the fixed and moving blades.
Velocity diagram reaction turbine stage
z represents the blade speed , V r represents the relative velocity, V wa & V wb-
represents the tangential component of the absolute steam in and steam out
velocities
The power developed per stage = Tangential force on blade x blade speed.
Power /stage= (V w a - V wb).z/1000 kW per kg/s of steam
The blade speed z is limited by the mechanical design and material constraints of
the blades.

Rankine Cycle
The Rankine cycle is a steam cycle for a steam plant operating under the best
theoretical conditions for most efficient operation. This is an ideal imaginary
cycle against which all other real steam working cycles can be compared.
The theoretic cycle can be considered with reference to the figure below. There
will no losses of energy by radiation, leakage of steam, or frictional losses in the
mechanical componets. The condenser cooling will condense the steam to water
with only sensible heat (saturated water). The feed pump will add no energy to
the water. The chimney gases would be at the same pressure as the
atmosphere.
Within the turbine the work done would be equal to the energy entering the
turbine as steam (h1) minus the energy leaving the turbine as steam after perfect
expansion (h2) this being isentropic (reversible adiabatic) i.e. (h1- h2). The
energy supplied by the steam by heat transfer from the combustion and flue
gases in the furnace to the water and steam in the boiler will be the difference in
the enthalpy of the steam leaving the boiler and the water entering the boiler =
(h1 - h3).
Basic Rankine Cycle

The ratio output work / Input by heat transfer is the thermal efficiency of the
Rankine cycle and is expressed as
Although the theoretical best efficiency for any cycle is the Carnot Cycle the
Rankine cycle provides a more practical ideal cycle for the comparision of steam
power cycles ( and similar cycles ). The efficiencies of working steam plant are
determined by use of the Rankine cycle by use of the relative efficiency or
efficiency ratio as below:
The various energy streams flowing in a simple steam turbine system as
indicated in the diagram below. It is clear that the working fluid is in a closed
circuit apart from the free surface of the hot well. Every time the working fluid
flows at a uniform rate around the circuit it experiences a series of processes
making up a thermodynamic cycle.
The complete plant is enclosed in an outer boundary and the working fluid
crosses inner boundaries (control surfaces).. The inner boundaries defines a flow
process.
The various identifiers represent the various energy flows per unit mass flowing
along the steady-flow streams and crossing the boundaries. This allows energy
equations to be developed for the individual units and the whole plant...
When the turbine system is operating under steady state conditions the law of
conservation of energy dictates that the energy per unit mass of working agent **
entering any system boundary must be equal to the rate of energy leaving the
system boundary.
**It is acceptable to consider rates per unit mass or unit time whichever is most
convenient

Steady Flow Energy Equations
Boiler
The energy streams entering and leaving the boiler unit are as follows:
F + A + h d = h 1 + G + hl b hence F + A = G + h 1 - h d + hl b
Turbine
h 1 = T + h 2 + hl t hence 0 = T - h 1 + h 2 + hl t
Condenser Unit
W i + h 2 = W o + h w + hl c hence W i = W o + h w - h 2 + hl c

Feed Water System
The energy streams entering and leaving the Feed Water System are as follows:
h w + d e + d f= h d + hl f hence d e + d f = - h w + h d + hl
The four equations on the right can be arranged to give the energy equation for
the whole turbine system enclosed by the outer boundary
That is ..per unit mass the of working agent (water) the energy of the fuel (F) is
equal to the sum of
- the mechanical energy available from the turbine less that used to drive the
pumps (T - (d e+ d f)
- the energy leaving the exhaust [G - A] using the air temperature as the
datum.
- the energy gained by the water circulating through the condenser [W o - W i]
- the energy gained by the atmosphere surrounding the plant Σ hl
The overall thermal efficiency of a steam turbine plant can be represented by the
ratio of the net mechanical energy available to the energy within the fuel
supplied. as indicated in the expressions below...
Turbine Vapour Cycle on T-h Diagram
Steam cycle on Temp - Enthalpy Diagram
This cycle shows the stages of operation in a turbine plant. The enthalpy
reduction in the turbine is represented by A -> B . The reversible process for an
ideal isentropic (reversible adiabetic) is represented by A->B'. This enthalpy loss
would be (h g1 - h 2 ) in the reversible case this would be (h g1 - h 2s ).
The heat loss by heat transfer in the condenser is shown as B->C and results in
a loss of enthalpy of (h 2- h f2) or in the idealised reversible process it is shown by
B'-> C with a loss of enthalpy of (h 2s- h f2).

The work done on the water in extracting it from the condenser and feeding it to
the boiler during adiabetic compression C-> D is (h d - h f2 ) = length M
The energy added to the working agent by heat transfer across the heat transfer
surfaces in the boiler is (h g1 - h d ) which is approx.( h g1 - h f2 )
The Rankine efficiency of the Rankine Cycle AB'CDEA is
The efficiency of the Real Cycle is

Following were Some of the machines used for the
manufacturing of the steam turbine parts
Craven Lathe machine
No .20/A/30
Speed : .5-51 rpm
Distance from the centre : 7620 mm
Maximum swing over 1676 mm
Head stock Face Plate diameter : 1524 mm
Face Plate gripping Capacity: 203-1270mm
Load :90 tons (stades)
Horizontal Boring Machine:
No. 20/A/2111
Spindle diameter: 127mm
Fending head:1524 mm
Width of table =1524 mm
Maximum dia of boring bar = 158.80 mm
Feeds=129- 38 mm
Morando Boring Machine
No: 20/A/2012
Speed :1.5- 200 rpm
Feed: .5-2000 mm/min
Centre Height: 770 mm
Distance between centres :6000 mm
On Swing Bed: 1520 mm
Max Weight on Centre= 30 Tons
Max Weight on face plate= 60 Tons
Richard Vertical Boring and Turning Machine
No : 20/A/11
Speed : .48- 13 rpm
Feed: .501 – 102.51 mm/min
Dia: 4877 mm
Max Turning Diameter: 4955 mm

BHARAT HEAVY ELECTRICALS STEAM TURBINE

Empfohlen

Empfohlen

Weitere ähnliche Inhalte

Was ist angesagt?

Was ist angesagt? (20)

Ähnlich wie BHARAT HEAVY ELECTRICALS STEAM TURBINE

Ähnlich wie BHARAT HEAVY ELECTRICALS STEAM TURBINE (20)

BHARAT HEAVY ELECTRICALS STEAM TURBINE