A Project Report

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A Project Report
On
IMPACT OF
SCALING ON TURBINE BLADES
A Dissertation submitted in partial fulfillment of the academic requirements for the award
of the degree of
BACHELOR OF TECHNOLOGY
IN
MECHANICAL ENGINEERING
By
B. GOPINATH HT No. 10U81A0302
V. VENKATESWARA RAO HT No. 10U81A0340
K. NIKHIL HT No. 10U81A0315
M. NAVEEN HT No. 10U81A0317
V. RAJESH HT No. 10U81A0338
Under the Esteemed guidance of
P.RAMAMOHAN REDDY
Head of the department
DEPARTMENT OF MECHANICAL ENGINEERING
SARADA INSTITUTE OF TECHNOLOGY & SCIENCE
Raghunadhapalem, Khammam District - 507002
JUNE- 2013
SARADA INSTITUTE OF TECHNOLOGY & SCIENCE

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Raghunadhapalem, Khammam District - 507002
DEPARTMENT OF MECHANICAL ENGINEERING
CERTIFICATE
This is to certify that the Dissertation entitled " IMPACT OF
SCALING ON TURBINE BLADES" is a Bonafide work done by
V.VENKATESWARA RAO in partial fulfillment of the academic requirements for
the award of the degree of Bachelor of Technology in Mechanical Engineering ,
submitted to the Department of Mechanical Engineering, SARADA INSTITUTE
OF TECHNOLOGY & SCIENCE during the period 2010-2014.(17-06-2013 to
30-06-2013)
Internal Guide HOD
Department of Mechanical
T.VEERA SWAMY
DIVISIONAL ENGINEER
Turbine Maintenance , KTPS-VI Stage

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ACKNOWLEDGMENT
With great pleasure we want to take this opportunity to express our heartfelt gratitude to
all the people who helped in making this project work a grand success.
We are grateful to Mr. T. VEERA SWAMY for his valuable suggestions and
guidance given by him during the execution of this project work.
First of all we would like to thank Mr. P.RAMAMOHAN REDDY, Head of the
Department of Mechanical Engineering, for being moral support throughout the period of
our study in SARADA Institution.
We are highly indebted to Principal Mr. Dr. NARASIMHA RAO for giving us
the permission to carry out this project.
We hereby express my sincere thanks and regards to. Er.T.VEERASWAMY
Divisional Engineer/ Turbine Maintanance Division, KTPS-VI Stage, Paloncha.
We take this opportunity to express my earnest thanks to
Er.R.PrabhakarRao.Sr.Chemist, KTPS- VI stage for his valuable guidance, constant
encouragement, cooperation and endorsement at every stage of this project work.
Our special thanks to Mr.A.SRAVAN, KTPS-VI Stage, for constant support and efforts
throughout the course of my project, to make it successful.
B. GOPINATH HT No. 10U81A0302
V. VENKATESWARA RAO HT No. 10U81A0340
K. NIKHIL HT No. 10U81A0315
M. NAVEEN HT No. 10U81A0317
V. RAJESH HT No. 10U81A0338

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ABSTRACT
Thermal power station is a power plant in which prime
mover is driven by steam. By combustion of fuel water is heated and
turns in to steam. Steam spins the turbine then power is produced
when turbine shaft is connected to the electrical generator.
A steam turbine is a mechanical device that converts
thermal energy of steam to electrical energy. The turbine is
effected by various losses which effect the performance of
turbine. Scale formation on turbine blade surface is one of them.
The aim of Our project is to avoid scaling on turbine blades
and to increase water recycle period. For this we have to remove
hardness of water by using various chemical processes.
Hardness is caused due to suspended particles of both organic
and inorganic matters. The deposits like silica, magnesium,
sodium on turbine blade surface will influence the flow of steam
pressure. Temperature , axial shift and efficiency of turbine.
By removing the hardness of water through chemical process we
can eliminate the scaling over the turbine blade surface hence the
above effects can be reduced, in turn improve the performance of
turbine and results in increase in power generation.

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CONTENTS
1. Steam Turbine Theory - 01-29
2. Demineralization Process - 30-39
3. Turbine Deposits & its Effects - 40-69
4. Removal of deposits - 70-77

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CHAPTER-1
STEAM TURBINE THEORY
HISTORY:
First St. turbine was produced by Hero, a Greek Philosopher, in 120 B.C. In 1829, an
Italian named Branc anticipated the boiler- steam turbine First practical steam turbine was
introduced by Charles Parsons in 1884 In 1889, Guastav De Laval produced the first practical
impulse turbine Steam turbine was made as principle prime mover in the year1920 (14 kg/cm2,
276 o
c, 5 to 30 Mw).
DEVELOPMENT OF STEAM TURBINE:

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STEAM TURBINES IN APGENCO: AN OVERVIEW
BASIC PRINCIPLES OF STEAM TURBINE:
 CONVERSION OF HEAT ENERGY INTO KINETIC ENERGY
Hitachi Hitachi 30 NELLORE TPP 30
GE GE 62.5 Ramagundum TPP 62.5
LMW BHEL 210 Dr N.T.P.S 6X210
KWU BHEL 210 1260
KWU BHEL 210
KWU BHEL 500 DrN.T.P.S-iv1*500MW) 500
JAPAN JAPAN 60
KothagudemTPP.
A-Station (4 x 60 MW)
SKODA BHEL 110/(120) B-Station ( 2*110 MW) 1680
C-Station ( 2*110 MW)
KWU BHEL 250 V th Stage (2 * 500MW)
KWU BHEL 500 VI th Stage (1 * 500MW)
KWU BHEL 210
Rayalaseema TPP.
Stage -I (2 * 210 MW)
420
KWU BHEL 210
Rayalaseema TPP.
Stage -1 (2 * 210 MW)
420
KWU BHEL 210
Rayalaseema TPP.
Stage -2 (2 * 210 MW)
420
KWU BHEL 210
Rayalaseema TPP.
Stage -3 (1 * 210 MW)
210
KWU BHEL 500
kakatiya TPP.
Stage -I 1x *500MW)
500

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 DEPENDS UPON THE DYNAMIC ACTION OF THE STEAM
 DROP IN PRESSURE OF STEAM THROUGH SOME PASSAGE RESULTING
 TO INCREASE IN VELOCITY
 CHANGE IN DIRECTION OF MOTION GIVES RISE TO A CHANGE OF
MOMENTUM OR FORCE
 THIS IS DRIVING FORCE OF THE PRIMEMOVER
TYPES OF STEAM TURBINES:
 Impulse & Reaction
 Industrial & Utility
 Single stage & Multi stage
 Single cylinder & Multi cylinder
 Reheat & Non-reheat
 Back pressure & Condensing
 Controlled & Uncontrolled Extractions of Steam
 Geared & Direct drive
 Barrel & Split Outer Casings
APPLICATIONS:
• CAPTIVE POWER PLANT
• COGENERATION
• COMPRESSOR DRIVES
• BOILER FEED PUMP DRIVES
• COMBINED CYCLE
• POWER UTILITIES (Non reheat)
• POWER UTILITIES (Reheat)

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IMPULSE TURBINE:
• Maximum steam velocity( Impulse) is created at the inlet of moving blade
• Which means high Kinetic Energy
• This energy is utilized for rotation of moving blade
• Steam Velocity can be maximized by having maximum pressure drop in the Nozzles.
• Hence in 100% Impulse steam Turbine, whole pressure drop will be in stationary blades
or nozzles
• To sustain high velocity impulse stage should be very robust in construction.

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VELOCITY COMPOUNDED IMPULSE TURBINE:
PRESSURE COMPOUNDED IMPULSE TURBINE:

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REACTION TURBINE:
 Reaction is created due to action of change of direction of steam through bucket.
 This thrust or reaction causes the driving force
 This requires whole pressure drop in moving blade
 100% Impulse or Reaction stage is purely a theoretical assumption not practically
feasible
PRACTICAL SCENARIO:
FOLLOWING COMBINATIONS FEASIBLE
1. NOZZLE CONTROL MACHINE WITH FIRST IMPULSE STAGE AS CURTIS
WHEEL, REGULATING STAGE & SUBSEQUENT STAGES WITH VARYING
DEGREE OF REACTION
2. THROTTLE CONTROL MACHINE WITH ALL STAGES HAVING VARYING
DEGEE OF REACTION AROUND 50%

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MODE OF STEAM ADMISSION:
• NOZZLE CONTROL MACHINE
• THROTTLE CONTROL MACHINE
• SLIDING PRESSURE OPERATION MODE
• MODIFIED SLIDING PRESSURE OPERATION MODE
NOZZLE CONTROL MACHINE:
SALIENT FEATURES ARE
 IMPULSE TURBINE WITH DIAPHRAGMS, LINEAR
 NOZZLE SEGMENTS IN THE PERIPHERY
 PRESSURE DROP IN THE NOZZLES
 SEQUENTIAL VALVE OPENING
 PARTIAL ARC ADMISSION
 LOWER THROTTLING LOSS AT PART LOADS
 PERFORMANCE NOT VERY POOR AT PART LOAD
 TURBINES IDEAL FOR PEAK LOAD OPERATION
THROTTLE CONTROL MACHINE:
FEATURES IN COMPARISON ARE
IMPULSE TURBINE WITH
DIAPHRAGMS, LINEAR
1. Nozzle segments in the
periphery
2. Pressure drop in the nozzles
3. Sequential valve opening
4. Partial arc admission
5. Lower throttling loss at part
loads
6. Performance not very poor at
part load
7. Turbines ideal for peak load
operation
REACTION TURBINE
1. No nozzle segments
2. No pressure drop
3. Simultaneous valve opening
4. Full arc admission
5. Higher throttling loss at part loads
6. Performance poor at part load
7. Turbines ideal for base load
operation

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STEAM TURBINE CHARACTERISTIC CURVE
SLIDING PRESSURE OPERATION MODE:
IN THROTTLE CONTROL MACHINE
• ADMISSION VALVES FULLY OPEN AT ALL LOADS
• BOILER PRESSURE TO BE MATCHED WITH FIRST STAGE
• HENCE STEAM PRESSURE SLIDES WITH RESPECT TO LOAD
• MINIMUM THROTTLING LOSS
MODIFIED SLIDING PRESSURE OPERATION MODE:
• SOME THROTTLING RESERVE ( 10 TO 20% ) MAINTAINED
• ADMISSION VALVES NOT FULLY OPEN BUT SLIGHTLY CLOSED
• MAIN CONTROL STILL WITH BOILER
• CONSTANT THROTTLING LOSS AT ALL THE LOADS
• PERFORMANCE SLIGHTLY POOR

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K_N SERIES TURBINE:
 Output ranges 100 to 450 MW.
 Maximum pressure (bar/psi) 170/2470
 Max main steam temperature (0
C/0
F) 565/1050
 Max reheat steam temperature (0
C/0
F) 565/1050
 Combined (K) high- and Intermediate- pressure Cylinder, and separate low-
pressure (N) cylinder
HMN- SERIES TURBINE:
 Output ranges 200 to1200 MW.
 Maximum pressure (bar/psi) 300/4350
 Max main steam temperature (0
C/0
F)600/1100
 Max reheat steam temperature (0
C/0
F) 620/1150
 Separate high- (H) intermediate- (M) and low-pressure (N) cylinders

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CROSS SECTIONAL VIEW OF STEAM TURBINE:
TURBINE STEAM PARAMETERS ADOPTED FOR 200 MW AND
ABOVE CPACITY:
 FOR 200 MW UNITS
1. Initial steam pr - 150 kg/sq. cm (abs.)
2. Initial steam temperature - 537 deg c
3. Reheat steam temperature - 537 deg c
 FOR 500 MW UNITS (SUB CRITICAL UNITS)
 FOR 660 MW UNITS (SUPER CRITICAL UNITS)

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TURBINE CASINGS:
HP TURBINE CASING:
 HP Turbine casing is a double shell type
 Outer casing is barrel type without axial joint. This avoids mass accumulations
Gives uniform moderate wall thickness
 Inner casing is axially split and carries guide blades. Horizontal joint flanges are
relieved by the higher pressure arising outside and can thus be kept small
 The inner casing is kinematically supported inside the barrel resulting in free
radial expansion in all directions and axial expansion from a fixed point when
heating-up
 Barrel construction permits rapid start-ups and higher rates of load changes due to
absence of higher thermal stresses
 HP Casing is made of 1.5% Cr, 1.0% Mo, 0.25% V Cast Steel

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IP TURBINE CASING:
 IP Turbine casing is of double shell type
 It is of double flow construction. This compensates axial thrust
 Steam enters at the mid-section of the turbine. This avoids heating of bearing
sections and supporting brackets
 Both inner and outer casings are horizontally split
 The joint of the outer casing is subjected to lower pressure & temperature
prevailing at the outlet of the inner casing. This keeps the joint flange small
 The joint of the inner casing is relieved by the pressure in the outer casing so that
this joint has to be sealed only against the resulting differential pressure
 IP Casing is made of 1.5% Cr, 1.0% Mo, 0.25% V Cast Steel
LP TURBINE CASING:
 LP Turbine casing is of triple shell type


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 It is of double flow construction. This compensates axial thrust
 The shells are axially split and of rigid welded construction
 The outer casing consists of front & rear end walls, two side memebers called
longitudinal girders and top cover
 The inner casing is supported kinematically at each end by two support arms
resting on the side members of the outer casing
 The inner shell carries the first 2x5 stages guide blades. It is attached
kinematically in the middle shell
 Rings of guide blade carriers which constitute the remaining stages of the turbine
are bolted to the middle inner outer casing
 The casings are made of steel plates

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ANCHOR POINT OF TURBINE:
PURPOSE: Taking care of thermal expansions and contractions of the machine during
thermal cycling.
THE FIXED POINTS OF THE TURBINE ARE AS FOLLOWS:
 The bearing housing between the IP and LP turbines.
 The rear bearing housing of the IP turbine.
 The longitudinal beam of the I.P turbine.
 The thrust bearing in rear bearing casing of H.P turbine.
ROTORS:
HP ROTOR:
 The HP rotor is machined from a single Cr-Mo-V steel forging with integral discs.
 In all the moving wheels(17 stages), balancing holes are machined to reduce the
pressure difference across them, which results in reduction of axial thrust.
 First stage has integral shrouds while other rows have shroudings, rivetted to the
blades are periphery.

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IP ROTOR:
 The IP rotor has 12*2 discs integrally forged with rotor while last four discs are
shrunk fit.
 The shaft is made of high creep resisting Cr-Mo-V steel forging while the shrunk
fit disc are machined from high strength nickel steel forgings.
 Except the last two wheels, all other wheels have shrouding riveted at the tip of
the blades. To adjust the frequency of the moving blades, lashing wires have been
provided in some stages.
COMBINED HP –IP ROTOR
LP ROTOR:
 The LP rotor consists of shrunk fit discs a shaft.
 The shaft is a forging of Cr-Mo-V steel while the discs are of high strength nickel
steel forgings.
 Blades are secured to the respective discs by riveted fork root fastening.
 In all the stages lashing wires are providing to adjust the frequency of blades. In
the last two rows salite strips are provided at the leading edges of the blades to
protect them against wet steam erosion.

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 BLADES:
 Blades are single most costly elements of turbine
 Blades fitted in the stationary part are called guide blades or nozzles and that
fitted in the rotor are called moving or working blades
 Types of blades
1. Cylindrical or constant profile blades
2. Tapered cylindrical blades
3. Twisted and varying profile blades. Used for very long blades
BLADE PARTS:
 Aerofoil – working part of the blade
 Root – blade portion that is held with disc, drum or casing
 Shroud – can be either riveted by tanon to main blade or integrally machined with
the blade. Nowadays trend is integral shourd for shorter blades and free standing
blades for longer blades.
 Shrouds are used to prevent steam leakage & to guide steam to next set of
moving blades.
TYPICAL 3DS BLADE TYPICAL TX BLADE

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SEALING GLANDS:
 Steam is supplied to the sealing chamber at 1.03 to 1.05 Kg/sq.cm abs and at
temperature 1300
C To 1500
C from the header.
 Air steam mixture from the last sealing chamber is sucked out with the help of a
special steam ejector to gland steam cooler.
 Provision has been made to supply live steam at the front sealing of H.P. and I.P.
rotor to control the differential expansion, when rotor goes under contraction
during a trip or sharp load reduction.
BEARINGS:
 General bearing --- 6no.s
 Thrust bearing --- 1no.
Bearings are usually forced lubricated and have provision for admission of jacking oil
FRONT BEARING PEDESTAL:
 The Front Bearing Pedestal is located at the turbine side end of the turbine
generator unit.
 Its function is to support the turbine casing and bear the turbine rotor.

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 It houses the following components
a. Journal bearing
b. Hydraulic turning gear
c. Main oil pump with hydraulic speed transducer
d. Electric speed transducer
e. Over speed trip
f. Shaft vibration pick-up
g. Bearing pedestal vibration pick-up
 The bearing pedestal is aligned to the foundation by means of hexagon head
screws that are screwed in to it at several points.
 The space beneath the bearing pedestal is filled with non shrinking grout.
 The bearing pedestal is anchored at to the foundation by means of anchor bolts.
 The anchor bolt holes are filled with gravel; it gives a vibration damping effect.
FRONT BEARING PEDESTAL

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BEARING PEDESTAL (HP REAR):
 The Bearing pedestal (2) is located between the HP and IP turbine.
 Its function is to support the turbine casing and bear the HP IP rotor.
 It houses the following components
1. Combine Journal and Thrust bearing
2. Shaft vibration pick-up
3. Bearing pedestal vibration pick-up
4. Thrust Bearing trip(electrical)
COMBINED JOURNAL AND THRUST BEARING:
 The magnitude and direction of axial thrust of the turbine depends on the load
condition
 The Journal bearing is elliptical sleeve bearing.
 The bearing liners are provided with a machined babbit face.
 Located at each end of bearing shell, babbitted thrust bad forms 2 annular
surfaces.

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 These collars and thrust pads permit equal loading of thrust bearing.
 Thrust pads are of tilting type.
 Metal temperature of the journal bearing and thrust pads is monitored by the
thermocouples.
IP REAR BEARING PEDESTAL:
ARRANGEMENT: The bearing pedestal is located between the HP and IP turbines. Its
function is to support the turbine casing and bear the HP and IP turbine rotors. The
bearing pedestal houses the following turbine components:
 Journal bearing
 Shaft vibration pick-up
 Bearing pedestal vibration pick-up
 Hand barring arrangement
 Differential expansion measurement device
JOURNAL BEARING:
 The function of the journal bearing is to support the turbine rotor.
 The journal bearing Consists of the upper & lower shells, bearing cap, Spherical
block, spherical support and key.
 The bearing shell is provided with a babbit face.
 Bearing is pivot mounted on the spherical support to prevent the bending
movement on the rotor.
 A cap which fits in to the corresponding groove in the bearing shell prevents
vertical movement of the bearing shell.
 The bearing shells are fixed laterally by key.
 Each key is held in position in the bearing pedestal by 2 lateral collars.
 The Temperature of the bearing bodies is monitored by thermocouple.
 Upper and lower shell can be removed without the removal of Rotor.
 To do this shaft is lifted slightly by means of jacking device but within the
clearance of shaft seal.
 The lower bearing shell can be turned upward to the top position and removed.

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 LP TURBINE:
REAR BEARING PEDESTAL:
 The bearing pedestal is situated between the LP turbine and generator. Its function
is to bear the LP rotor.
 The bearing pedestal contains the following turbine components:
1. Journal bearing
2. Shaft vibration pick-up
3. Bearing pedestal vibration pick-up
BARRING GEAR:
The primary function of barring gear is rotate the turbo generator rotors slowly
and continuously during startup and shutdown periods when changes in rotor
temperature occurs
shaft system is rotated by double row blade wheel which is driven by oil provided
by AOP
A manual barring gear is also provided with hydraulic gear
Barring speed 210/240 rpm

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TYPES OF TURNING GEAR:
 Mechanical turning gear speed is 3 to 4 rpm (LMW)
 Hydraulic turning gear speed is 60 to 120 rpm (KWU )
 Hand barring
ESV & CV:
 2 main stop valves and 2 control valves located symmetrically
 The main steam is admitted through the main steam inlet passing first the main
stop valves and then the control valves. From the control valves the steam passes
to the turbine casing.
 Turbine is equipped with emergency stop valve to cut off steam supply with
control valves regulating steam supply
 Emergency stop valve are actuated by servo motor controlled by protection
system
 Control valves are actuated by governing system through servo motors to regulate
steam supply
COUPLINGS:
 Shaft is made in small parts due to forging limitation and other technological and
economic reason, so coupling is required between any two rotors
 Here using rigid coupling due to high torque flexible coupling can’t be used
coupling between
1. HP & IP
2. IP & LP
3. LP & generator
4. GEN & exciter
5. MOP & HP

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6. HEAT RATE CHARACTERISTICS OF NOZZLE
CONTROLLED / THROTTLE CONTROLLED MACHINES
TECHNICAL DATA OF 500MW TURBINE

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STEAM PRESSURES
STEAM TEMPERATURES

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PROTECT. SYSTEM

32
OIL SUPPLY

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MATERIAL COMPOSITION:
 H.P. CASING : 1 ½ % Chromium, 1 % Molybdenum.
 I. P. CASING : 1 ½ % Cr, 1 % Mo, ¼ % V, cast steel.
 L.P. CASING : Steel plate (tested).
 H.P. ROTOR : ½ % Cr, 1% Mo, ¼ % V, steel forgings.
 I.P. ROTOR : ½ % Cr, 1% Mo, ¼ % V, steel forgings.
 L.P. ROTOR : 1 ¼%Cr, 1% Mo, ¼ %V steel forgings.
 HP – IP BLADES:
 STATIONARY AND MOVING : 11%Cr, ¼% Mo, ¼ %V
(High temperature) steel forgings
LOW TEMPERATURE &LOW PRESSURE:
STATIONARY AND MOVING : 12 to 14 %Cr, steel forgings
(Low temperature)
 L.P. BLADES:
 STATIONARY AND MOVING : 12 to 14 %Cr, steel forgings
 WHITE BABBIT : Copper 5 to 6 %, Antimony 9 -10 %, Lead 0.3 % Tin –
balance.
SHAFT SEALS:
 Shaft seals in turbine are provided to check steam leakage from HP and IP
turbines and air leakage into L.P. Turbine.
 The shaft seals are axial labyrinths with the sealing strips caulked into the shafts
and into stationary seal rings alternatively.
 In case of L.P. Cylinder glands sealing strips are fitted in the stationary rings only.

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CHAPTER-2
DEMENARALIZATION PROCESS
INTRODUCTION
Water, which is required for process use or for industrial
purpose, is available from two sources. Surface supplies such as
rivers lakes etc., and underground supplies such as tube wells.
Natural water contains dissolved salts in the form of Bi-
carbonates and carbonates of calcium, magnesium and sodium
as alkaline salts and in the form of sulfates, chlorides and nitrates of
calcium, magnesium and sodium as neutral salts. Other dissolved
impurities such as silica, dissolved CO2 and metal such as Iron,
Manganese and organic matter may also be present to a lesser
extent.
The nature of water in use depends on the type of the
industry. For example, I the case of industries with low-pressure
boilers, heating and cooling systems, bottle-washing process, water
in raw condition could be used. But in thermal power station, a
very high quality – ultra pure de-mineralized water is used in their
high pressure boilers to avoid scaling in the system and also in case
of laboratory purposes to avoid contamination of reagents.

35
The chemical reagent manufacturing companies, the
thermal power station, scientific labs, nuclear power stations, heavy water
producing plants are few to mention which consume ultra-pure de-
mineralized water.
2.1. Harmful Effects of Water Impurities
Harmful effects may be classified as:
1. Deposits or scales formed in boilers and other heat exchange
equipment, which acts as insulation, preventing efficient heat
transfer and causing boiler tube failures through over heating of
metal.
2. Poor-quality boiler steam, which contains impurities that foul steam-
using equipment such as turbines and decrease their efficiency
rapidly
3. Waste of various chemicals such as acids, alkalis and other
chemicalsresultingundesirableeffectsonenvironmentthroughconta
mination of drinking water making it unsuitable because of
objectionable tastes, odor or bacterial contaminations
4. Chloride and sulfate contaminated water will cause corrosion of
boilers, heaters and the connected piping.

36
These ill-effects cause harm in thermal power station both structurally and
financially. For example the de-scaling process of a boiler of one unit
through chemical cleaning would take several weeks time and will cost
several lakhs of rupees besides generation loss.
2.2.Why De-Mineralized Water In Thermal Power Stations
A thermal power plant consists of a large water heating system that
produces high quantities of steam under full load conditions. Ordinary
water or mineralized water will contaminate the system through corrosion,
erosion and scaling and likely will scrap the system within no time.
Hence to ensure the longevity of the heating system ultra-pure de-
mineralized water is a must. With a proper quality of D. M. water, a boiler
in a thermal power plant could be run for a long period, provided there is
no other specified water leakages into the system.
2.3. Where is D.M. Water produced
A separate entity called De-Mineralized Plant (D.M. Plant) is provided in
every thermal power station for production of D.M. Water. It consists of
various stages, wherein, the ordinary water loses its mineral and purifies
Since the production of D.M. Water and the maintenance of high
quality involve a large number of chemical procedure, a chemical
division comprising of chemists of various executive cadres are entitled to
supervise it. The D.M. Plant needs the support of mechanical, electrical,
instrumentation and control, turbine and civil maintenance personnel for
the periodical maintenance and smooth running of the plant.

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FIG 2.1 LINE DIAGRAM OF D.M PROCESS
1.Clarifier tank
2.pressurized sand filter
3.activated carbon filter
4.Cat ion exchanger
5.Degassifier stank
6.Blower
7.Anion exchange
8.Mixed Bed
PRINCIPLE OF OPERATION OF D.M PLANT :
The most important operation of D.M Plant is the production of D.M Water of very
high quality that would suit the specific requirements of a high – pressure boiler.
D.M Plant de-mineralizes the ordinary raw water through the principle of ion
exchange. To start with, the raw water which consists of turbidity varying from
1
2
3
4
5
6
7 8

38
10NTU to 400NTU depending on season is clarified by treatment with aluminum
sulphate or Alum in a water clarifier. Thus clarified water normally has turbidity <=
5 NTU. Thus, clarified
water becomes the primary source of water for a D.M Plant. The clarified water
is treated with liquid chlorine to reduce organic matter such as Algae
The clarified water is filtered using a pressurized sand filter containing sand of
various graded sizes as filer medium. The effluent of PSF has a turbidity of <=
1NTU.
This filtered water is passed through Activated Carbon Filter wherein any excess
chlorine, colouring matter, oil etc are absorbed by Activated Carbon. The
Effluent of ACF has turbidity <=0.2 NTU. Thus filtered water from ACF is passed
into cat ion exchanger bed . The cat in exchanger bed consists of strong acid
cat ion exchange resin – made up of sulphonated polystyrene – represented as
R-H. This resin is in the form of a bead and has many active sites in the
exchangeable hydrogen form. The positive ions (cat ions) present in water are
exchanged with hydrogen in the resin as represented in the following equation.
R-SO3H+Ca+2 R-SO
3 Ca+2 +RX
Mg+2 X- Mg+2
Na+ Na+
This resin bead has a specified exchange bed contains 11000 liters
of cation resin and treats 3000 tonnes of water, after which it losses exchange
property and thus is said to have “exhausted”. The exhausted resin bed is again
regenerated into original hydrogen form using strong acids such as sulphuric

39
acid or hydrochloric acid at 5% concentration. The process is called
„Regeneration‟ and is represented by the following equation.
R-SO3 Ca+2 +H2SO4 RSO3H+Mineral sulphates
Mf+2 or or
Na+ HCI Chlorides
Exhausted (5%Conc.) Resin
Resin
During this process the bicarbonate salts produces a sizeable quantity of carbon
dioxide, which has to be eliminated, if not, would load the anion exchanger unit
represented as
R – H + NaHCO3 R Na + C02 +H2O
Cation exchanger effluent has low pH owing to the presence of mineral
acids around 2.8 – 3.3. Cation water is tested for pH and free mineralacidity(FMA).
F.M.A
PH~2.8-3.3
FMA ~28-32(at KTPS). (IF F.M.A IS LESSTHAN 28 RESIN IS EXHAUSTED)
The cation effluent water is passed into De-gasser consisting of “Raschig”-
Porcelain rings arranged in a tower like structure fitted with air blower opposite to
the flow, forces out the dissolved CO2.this water is called De-Gassed water.

40
The de-gassed water contains only 6ppm of CO2 at 300C, is transferred
into anion exchanger bed. The anion exchanger resin is Polystyrene compound
with quaternary ammounium group-represented as R-OH. The de-gassed water
containing free mineral acids pass through the strong base anion resin wherein
the negative ions of the free acids are exchanged with hydroxide ions of the
resin as represented
R – OH + HCI CI-
H2SO4 R SO4
-2 + H2O
H2CO3 CO3
-2 H2SIO3
SiO3
-2
The effluent of anion exchanger is alkaline in nature. The PH of this effluent
depends on the amount of sodium slip from the cation exchanger, which
also induces rise in conductivity.
The most important parameter to be noted for the anion effluent is silica.
The point of exhaustion of anion resin is determined by the breaking of silica ,The
safety parameters for a better quality effluent from anion exchanger are:
Conductivity <20 micro siemens / cm.
Silica < 0.2ppm
Sodium <2.0ppm
The anion exchanger effluent in itself is dematerialized water as
both positive and negative components of water have been removed.
But these high side safety limits doesn‟t make this water suitable for use in
H.P Boilers. A polishing unit called Mixed bed is used to further reduce the

41
impurities of anion water. The mixed bed consists of both cation and
anion exchanger resin mixed in suitable proportions. The anion exchanger
effluent passes through the mixed bed and undergoes further
demineralization and the final product is the D.M water of high quality
suitable to be used for H.P boiler with pressures above 135KSC.
A mixed bed normally, is not run for exhaustion. It has high
treatment capacity of order of 20,000MT between regenerations. A
mixed bed is pre-exhausted and then regenerated, as its exhaustion
would lead to the contamination of stored D.M water.
The regeneration procedure of mixed bed is highly intricate,
involves large number of operations
The D.M water of high quality must have following specifications:
Conductivity <0.2 micro siemens/cm.(Online Measurement)
Silica <5ppb (Spectrophotometric Measurement)
PH ~ 6.5 – 7.0
C1- <2ppb (Measured by Multi – ion analyzer)
During this process of demineralization, chemical wastes such as sulphuric
acid and caustic soda are collected into a waste water sump. They are tested
for PH and neutralized accordingly before disposed into the station drain ensuring
the minimization of environmental pollution.

42
2.4 COST ECONOMICS OF D.M WATER PRODUCTION
The cost of production for one tone of D.M water produced in D.M Plant
KTPS, C Station is calculated as follows.
TOTAL FIXED COSTS
The fixed costs in D.M Plant include costs incurred on working personnel,
auxiliary power consumption on various motors, costs of resins, sand, activated
carbon, laboratory reagents, alum, water etc. Each of the items is calculated for
a month. The variable costs include the costs of sulphuric acid and caustic
soda, which vary according to the D.M. Water production per month.
The total fixed cost is calculated to be Rs 396000/- per month.
NOTE:
1. Salaries of the employees are calculated @ 80% per employee as the
employee‟s services are used for other purposes also.
2. Resins life span is considered to be for 5 years.
3. Sand and activated carbon has a life span of 8 years.
4. Power consumption @ Rs 1.35/- per unit.
5. Average power consumption is estimated as 515 units/day.
6. The cost of sulphuric acid is Rs. 3300/- per ton.
7. The cost of caustic soda is Rs. 17000/- per ton.
8. Higher costs of D.M. Water in Aug-2005 owes to the de-fouling
procedure taken up for two anion exchangers, done periodically for
every six month.

43
9. The average cost is calculated within an error of 5%.The variable
chemical costs and hence the cost of D.M Water.
SAFETY Average cost=26.938
2.5 PRECAUTIONS IN HANDLING OF CHEMICALS
1. Sulphuric acid and caustic soda cause severe burns when come into
contact with contact with skin.
2. The affected area must be washed with plenty of water for 10 minutes
and should be neutralized with dilute boric acid or sodium carbonate.
3. Hand gloves, eye glasses, safety jacket must be used to avoid such
accidents.
4.The affected victim must be rushed to hospital in case of emergency.
Month/
2005
Acid
consumption
(tons) X Rs.
3300/- (A)
Alkali (tons) X
Rs 1700/- (B)
A+B +Rs
396000/-
D.M.W
Prod‟n In
tons
Cost/ton
Rs.
March 27720 48790 475080.40 18000 26.59
April 25245 39490 460685.00 18910 24.36
May 23430 48110 467540.00 21330 21.91
June 32670 59840 488510.00 22550 21.67
July 25080 48110 469190.00 20620 22.75
August 15180 481 459290.00 13380 34.32

44
CHAPTER - III
TURBINE DEPOSITS & ITS EFFECTS
3.1 TYPES OF DEPOSITS:
1. Water soluble deposits
Ex: sodium chlorides, sodium hydroxide
2.Water insoluble deposits
mainly silica water soluble deposits prevail in the H.P & I.P section of steam
turbine.
The silica segments prevail at the end of intermediate pressure and low pressure
section of the turbine.
The quantity of the steam is to upgraded to avoid turbine deposition this is done
by
1. Boiler feed quality
2. steam boiler model
3. boiler design
4. boiler operation
3.2 BAD EFFECT OF TURBINE DEPOSITION :
Economic effect
a) Reduction in turbine output.

45
b) Decrease in efficiency requiring high steam consumption
EROSION ON TURBINE BLADES
EFFECT OF OVER LODING AND DECREASING RELIABILITY
IN OPERATION
a) Pressure in the turbine gets distributed with the effect Overloading,
the effect on thrust bearing increases.
b) Blades are subjected to high bending stress.
c) Nature vibration of the balding effected.
d) Vibration due to uneven deposition on turbine.
e) Valve jamming due to deposit on the valve steam.
CORROSION EFFECT
1.Pitting corrosion
2.Stress corrosion
3.Erosion corrosion

46
1. PITTING CORROSION
Pitting corrosion is a localized accelerated attack, resulting in the
formation of cavities around which the metal is relatively unattached. Thus,
pitting corrosion results in the formation of pinholes, pits and cavities I the metal.
Pitting is, usually, the result of the breakdown or cracking of the protective film on
a metal at specific points. This gives rise to the formation of small anodic and
large cathodic areas. In the correct environment, this produces corrosion
current. Breakdown of the protective film may be caused by
i. Surface roughness or non-uniform finish
ii. Scratches or cut edges
iii. Local straining of metal, due to non-uniform stresses
iv. Alternating stresses
v. Sliding under load
vi. Impingement attack
vii. Chemical attack
Metal owing their corrosion resistance to their passive state, show a
marked pitting under all conditions, which lead to the destruction of their
passivity. For examples, stainless and aluminum shoe characteristic pitting in
chloride solution.
The presence of the extraneous impurities embedded on the surface of
metal also to pitting. Owing to the differential amount of oxygen in contact with
the metal the small part become the anodic areas and the surrounding large
parts become the cathodic areas. Intense corrosion, therefore, start just
underneath the impurity. Once a pit is formed, the rate corrosion increases

47
2. STRESS CORROSION:
‘It is the combined effect of static tensile stresses and the corrosive
environment on a meal”. It is characterized by a highly localized attack
occurring, when overall corrosion is negligible. For stress corrosion to
occur
i. Presence of tensile stress, and
ii. Specific corrosive environments are necessary.
The corrosive agents are highly specific and selective such are
a) Caustic alkalis and strong nitrate solution for mild steel
b) Traces of ammonia for brass
c) Acid chloride solution for stainless steel.
The type of corrosion is seen in fabricated articles of certain alloys (like
high-zinc brasses and nickel brasses) due to the presence of stresses
caused by heavy working like rolling, drawing or insufficient annealing.
however, pure metals are relatively immune to stress corrosion.
Stress corrosion involves in localized electrochemical corrosion, occurring
along narrow paths, forming anodic with respect to the cathodic areas at
the metal surface. Presence of stress produces strains, which result in
localized zones of higher electrode potential. These become so
chemically active that they are attacked, even by a mild corrosive
environment, resulting in the formation of a crack, which grows and
propagates in a plant until failure occurs

48
3. EROSION CORROSION:
Erosion corrosion is caused by the combined effect of the abrading
action of turbulent flow of gases, vapours and liquids; and the mechanical
rubbing action of solids over a metal surface.
CORROSION ON TURBINE BLADES
Erosion corrosion is caused by the break-down of a protective film at the
spot of impingement and it‟s subsequent to repair itself under exiting abrading
conditions. The abrading action removes protective films from localized spot on
the metal surface, there by resulting in the formation of differential cells at such
areas and to localized corrosions at anodic points of the cells.
Erosion corrosion is most frequently encountered in piping, agitators,
condenser-tubes or such vessels in which streams of liquids emerge from an
opening and strike the –walls with high velocities.
A bout 500grms deposits distributed all over the blade section can bring
down the turbine efficiency by 1%

49
EFFECT ON TURBINE BLADES :
When deposited steam flow over the surface of the blade it may leads to:
1. Growth of boundary layer.
2. Frictional resistance of the nozzle valves.
3. Energy losses of steam before entering the nozzle.
4. Deflection of the flow.
5. Erosion and corrosion.
6. Formation of eddies resulting in losses due to turbulence in steam flow
When the turbine and caused by the irregularities of steam flow i.e.
periodic nature of steam Flow as periodic external forces responsible for blades
vibration.
SCALING ON TURBINE BLADES AND ITS EFFECTS
Higher vibration causes damage rows of the turbine as these causes more
failure to the machine. As a consequence the life of the machine will come
down.
REMEDY:
1.By changing the number of blades in a stages or increasing space between
the blade rows.
2.By altering the thickness of the blade aerofoil all over (or) selectively.

50
3.Selecting appropriate material vibration.
When vibration comes the following also occurred.
1. Axial shift.
2. Differential expansion.
3. Eccentricity.
1. AXIAL SHIFT:
Axial shift is shifting of the rotor towards the generator or away from the
generator.
Limited value is = 0.65
„+‟ Means towards generator.
„-„ Means away from generator.
When axial shift is more than the limited value:
1.The rotor moves axially and touches the static parts; then blades get
damaged.
2.Axial shift measured at the thrust bearing (between H.P AND L.P turbine)
3.Monitoring of this parameter is very important
4.High axial thrust may result due to sudden water induction or abnormal
chocking of flow passages.
2. DIFFERENTIAL EXPANSION :
Owing to large different in masses rotor expands more than stator It effect
on
1.Outlet edge of guide blade
2.Inlet edge of moving blade

51
3.Gland fins or the rotor
Difference expansion = rotor expansion – stator expansion.
H.P. turbine + 3.5 mm to –1.5 mm
M.P. Turbine + 3.5 mm to –1.5 mm
L.P. Turbine + 4.0 mm to –1.5 mm
1. ECCENTRICITY:
When eccentricity occurs more than limited shaft may bend
1. It indicates bend in shaft
2. It is only indicative
3. Due to vibrations, bearing temperature rises
3.3 DEPOSITS DETECTING PROCESSES
PRESSURE MONITORING
Pressure of the steam is measured at particular points
1. At wheel chamber.
2. Points of pass out
3. Inlet and outlet of high pressure, intermediate pressure, low
Pressure the turbine.
The turbine manufacture provides the pressure characteristic in form of
the graph.
These theoretical graphs are derived actual measurement during the first.
These pressure characteristic compared with those operated during the
operation in lateral under identical condition and increasing pressure
show the formation of deposits.

52
A steam in the range of 72 to 80% an increasing wheel chamber pressure
more than 10% Sevier blade deposition.
INTERNAL EFFICIENCY MONITORING:
The economic rate efficiency various with the steam flow, the blade
deposition the passages of the steam flow.
i = ( H)pro/( H)ad*100H
( H)pro = process heat drop
( H)ad = adiabatic heat drop
The change inner condition steam turbine will alter in comparison original
value.
MONITORATING EXCHAUST STEAM TEMPERATURE:
The different exhaust temperature for different steam flow rates are
determined against steam flow plotted this will give at the time of First
condition.
Similar graphs are to be drawn at the lateral period comparing the initial
graph. A rise in exhaust steam temperature under the same condition
shows to Deposit formation.
A increasing of more than 30% exhaust steam temperature in the range if
70-100% steam flow rate indicates blade deposition.
These deposites are washed of by shutdown the unit.
The specific stream consumption (d) = D/E
D=Steam flow rate Kg/hr
E=Electrical Output at terminal Kw/hr
D=is determined at the time of first comes at clean turbine.

53
3.4 MONITORING OF AXIAL SHIFT
The following table consists of concentration of silica values in the DM
water for the period of six months from 25/01/2006 to 20/07/2006.
S.No Date Concentration of silica Axial shift (mm)
1. 25-01-2006 4.5 PPb 0.13
2. 11-02-2006 15.5 PPb 0.287
3. 17-02-2006 14.5 PPb 0.317
4. 29-02-2006 4.5 PPb 0.24
5. 09-03-2006 5.0 PPb 0.30
6. 24-03-2006 4.5 PPb 0.38
7. 25-03-2006 14 PPb 0.47
8. 08-04-2006 14 PPb 0.448
9. 30-04-2006 4 PPb 0.56
10. 07-05-2006 4 PPb 0.629
11. 14-05-2006 4.5 PPb 0.71
12. 21-05-2006 13 PPb 0.78
13. 01-06-2006 14 PPb 0.81

54
14. 07-06-2006 5 PPb 0.85
AXIAL SHIFT DATA FROM 1.01.06 TO 08.01.06, CORRESPONDING SILICA CONENTRATION
The above graph is drawn between concentration of silica (for the period of 6
months) and axial shift.
From the above graph it is observed that the percentage of silica in the DM
water is maintained with in the limited values the axial shift of rotor is increased
at the time of exhaustion of anion bed silica values are exceeds the limiting
values due to which little penetration silica and impinged action on the turbine
blade surface causes irregularity in the periodic nature of steam flow, which
results in axial shift of rotor. Further increase in the these values causes more
axial shift and vibrations, hence the turbine will get damaged.
*The other factor which influence the axial shift of Rotor is load.
When ever the load reduces on the turbine, decrease in steam flow and pressure
by governing system, at the same time extraction of steam from the extraction

55
points also reduces. Due to this little quantity of steam is retained in the turbine
and exerts residual forces on the turbine
RESULT:
shifting of turbine in axial position. If rotor moves towards generator is
„+‟ve and towards HP turbine is „-„ve.The following details collected from the
maintenance records of KTPS-VI unit B-Station. Before and after shut down of unit
on 20-07-2006.
Sl.No. Date
Load
(MW)
AXIAL SHIFT
(MM) Remarks
1. 19-01-2006 94 0.13
2. 28-01-2006 118 0.09
3. 03-02-2006 119 0.1
4. 11-02-2006 120 0.15
5. 17-02-2006 119 0.21
6. 22-02-2006 120 0.24
7. 27-02-2006 120 0.287
8. 29-02-2006 120 0.317
9. 03-03-2006 120 0.38
10. 09-03-2006 120 0.47

56
11. 24-03-2006 111 0.616
12. 24-03-2006 113 0.21
13. 25-03-2006 119 0.27
HP heater kept in
service.
14. 03-04-2006 119 0.24
15. 04-04-2006 120 0.25
16. 08-04-2006 116 0.33
17. 11-04-2006 115 0.398
18. 13-04-2006 116 0.39
19. 16-04-2006 118 0.435
20. 18-04-2006 118 0.448
21. 25-04-2006 120 0.44
22. 30-04-2006 116 0.56
23. 07-05-2006 115 0.57
24. 12-05-2006 116 0.58
25. 14-05-2006 116 0.62
C.b.pump is employed

57
26. 19-05-2006 116 0.629
27. 21-05-2006 115 0.21
28. 09-05-2006 114 0.78
29. 01-06-2006 113 0.81
30. 04-06-2006 114 0.82
31. 05-06-2006 114 0.85
32. 23-07-2006 119 0.09
After completion of all
shutdown works.
33. 26-07-2006 119 0.11
(SHUT DOWN WORK IS CARRIED OUT FROM 14/10/2006 TO 22/10/2006 BY
PROVIDING SHIMS IN THRUST BEARING)
The following graph is drawn between load (M.W) and Axial shift (mm)

58
From the above graph it observed that while decreasing the load
on the turbine axial shift of the rotor is been increasing.
At 120&114 MW the maximum and minimum values of axial shift
are 0.15mm, 0.85 mm respectively
Pressure
(Kg/Cm2)
Flow quantity
(tones)
LP-I - 0.24 8.4
LP-II - 0.476 7.42
LP-III - 1.207 10.863
LP-IV - 2.279 9.314
LP-V - 5.35 13.776
6TH – DA - 6.00 3.236
HP-II - 33.67 24.35

59
rotor
will shifts
from its
original
position to other position as comparatively at low load of 115 MW with full load
of 120 MW.
FIG 3.1 HEAT BALANCE SHEET OF TURBINE 120 MW
Pressure
(Kg/Cm2)
flow quantity
(tones)
LP-I - 0.199 7.2
LP-II - 0.39 6.31
LP-III - 1.14 9.19
LP-IV - 2.0 7.976
LP-V - 4.8 11.24
6TH – DA - 5.5 2.371
HP-I - 16.23 20.21
HP-II - 31.08 21.30

60
CHAPTER - IV
REMOVAL OF DEPOSITS
4.1. WATER SOLUBLE DEPOSITS :
1. Washed up the condensate
2. Washed up the wet steam.
The washing of turbine blades with condensate :
The washing of turbine blades carried out with the condensate at 1000C.
The turbine is cooled or heated up to 1000C and filled with the condensate
via a turbine drain.
The rotor is turned or barred by hand and the condensate is drained after 2
to 4 hours. It is then again filled with the condensate at 100C (but up to the
rotor center-level), the rotor is rotated and the condensate is drained after
sometime. This process is repeated several times.
The washing of turbine blades with wet steam :
Wet steam produced usually by injecting cold condensate into the superheated
steam, is introduced to he turbine which is kept on running at about 20% of
nominal speed.
For back pressure turbine the exhaust steam is let out into the open air
through a gate valve. For a condensing turbine, the vacuum pump is kept out of
service while cooling water is running, with the effect that the entering cooling

61
steam is condensed. The condensate is drained off. The washing steam
condition is gradually adjusted to a final wetness of 0.9 to 0.95.
4.2. WATER INSOLUBLE DEPOSITS ARE REMOVED BY MECHANICAL AFTER
DISMANTLING OF THE TURBINE.
Preparation for steam washing :
The following main works had been carried out during the shutdown in july
2006 and the subsequent start-up.
 During inspection of thrust bearing certain marks were observed on the
pedestal cover. The necessary rectification was carried out.
 The spring plate of the thrust bearing was replaced with the new spring
plate issued by APGENCO.
 Steam washing of the turbine was carried out during start-up
After start-up and noting down the readings of axial shift, main steam
pressure and load have been found to be normal.
PROCEDURE ADOPTED FOR WET STEAM WASHING OF HP TURBINE
PREPARATION FOR STEAM WASHING :
1. Total water in the system should be drain
2. fill hot well and dearator with fresh water
3. take sample for chemical testing.
4. HPT evacuation valve should be closed permanently by passing
protections to dump the exhaust into condenser.

62
5. IPT stop valves were closed permanently to avoid entering of HRH steam
in to IP TURBINE
6. All drain on turbine side and boiler side are kept open and HPDFT drain to
atmosphere.
7. All the extraction valves closed manually.
Kept CEP in service and after filling dearator, level become high (2200)
close the valve in condensate line after LPH-III and keep CEP in recirculation
mode, maintain the expander level with RFT and keep CBP in service and
makeup the dearator with CBP no wards. Boiler flashed and pressure is raised up
to 2kg/cm2 with superheat of 30C to 50C HPT rolling started and kept at 300rpm
for of an hour and at 500 rpm for 1 hour and at 100 rpm for remaining period. As
the turbine metal temperatures start increases, the pressure MS increased
50kg/cm2 gradually.
Samples were collected from hot well (i.e. from BEP suction drain points)
and Operation continued till constant valves reached. Hot well level maintaining
with CEP discharge valve locally, MS temperatures controlled with
attemperation. RH pressure maintained at 8 kg/cm2 to block NRV”s,to open and
not to allow back low with LPBP. HPBP opened around 40%. CEP discharge drain
adjusted in such way that CBP discharge flow should match the drain flow and
maintain hot well or reduce the quantity of steam dumping by closing HPBP. The
boiler is tripped ad boxed up till boiler falls to 5kg/cm2.
4.3 STEAM WASHING OF IP-LP TURBINES :
1. Evacuation should be normalized.
2. IPT stop valves blocking to be removed

63
At kg/cm2 of drum pressure all the vents were opened and SH drains and
water wall drains were opened to flush the boiler water walls an SH system.
During this period dearator, hot well drained and filled with fresh DM water
and rinsed complete compete system up to BEP suction by taking CEP. During
this period the BFP suction drain opened to let out the washed out material from
the system like condenser RC line, dearator suction lines. This operation continues
till.
The standard valves were obtained. After getting clearance from the
chemist boiler filling started.
During boiler filling operation all drains from the SH system and CBD are
kept opened. The boiler samples are being tested regularly to obtain silica
valves.
1. The clamps installed in tested devices of IP servomotors were removed to
enable the IP CVs to open manually.
2. The manual knobs in the vioth converters of all four HPCVs were closed to
ensure that the HPCVs not open.
3. The HRH pressure was maintained initially at around 8kg/cm2 with by pass
control ad the turbine was rolled to 500 rpm.
4. Gradually pressure ad temperature were raised and speed was raised up
to 900rpm.
5. Condensate draining out through CEP discharge continued.
6. Periodically samples were taken from condensate and MS points

64
7. The operation was continued till conductivity of condensate came down
to normal value.
8. Turbine tripped and kept on barring gear vacuum filled also boiler was
tripped.
9. All the drains were left open, as some contaminated would have entered
rest of the system (like drains of drain flash tank all heater, dearator boiler
condensate and feed water system.
10. After completion of draining the hot well, dearator drained again till the
conductivity values become equal to that of fresh DM water.
To open evacuation and to give the close feed back the following
modification done on siemens hardware side for HP turbine steam washing.
It was observed that as compared to the period soon after commissioning
higher-pressure live steam required before HP stop valve and also before HPT
blading. The axial shift was gradually increases hence it was decided to carry out
steam washing during overhauls.
TIME ACTIVITY
18:30 Samples taken from hot well
Ph Conductivity silica phosphate
8.45 10.32 0.035
18.45 Rolling started and kept at 300 rpm with
parameters MS pr. 20kg/cm2, MS
TEMPERATURE 250 C dearator makeup with CBP

65
TIME ACTIVITY
from DM WATER hot well level maintaining with
CEP discharge drain valve.
MS temp. control with spray station valves,
CRH presser.
Maintained at 8kg/cm2 to block NRVs to open and not
to allow back flow with LPBP.
Samples taken from hot well.
18.55 9.2 47 3.5 5.0
19.15 10.25 138 22.5 6.0
19.45 HP inner casing temp : 126
HP shaft temp. : 119
HP casing top : 112
HP casing bottom : 106
Speed raised to 500 rpm as I.P front horizontal
Vibrations found high (65cm) if there is no
Vibration problem it is better to continue at

66
300 rpm up to HP inner casing temp raised to 250C
CEP discharge drain adjusted in such a way that
CBP discharge flow and maintain hot well level at around
2000mmwc.
20.20 Parameters as follows :
HP inner casing temp : 132
HP shaft temp : 134
HP casing top : 139
HP casing bottom : 127
Ms pr : 28
Ms temp : 260/270
Gradually raise MS pr and temp as turbine inner casing temp are raises.
As the CEP discharge drain is not sufficient to evacuate
The condensate (hot well level raised above 2500mmwc) close the HPBP to 20%
and the quantity of steam dumping is reduced.
MS pr : 30, MS TEMP : 279/284
21.10 Hot well level comes to control range (2200) adjust the
CEP discharge drain valve to maintain the above level.

67
ti
22.0
Speed raised to 1000 rpm as chemical values becomes
stable HP
HP inner casing temp :157
HP shaft temp :
HP casing top : 144
MS pr : 36.3
MS temp : 269/270
22.10 When generator from vertical vibration found increases
reduced the speed to 935 rpm. Steam dumping reduced
by closing HPBP from 25% to 20%.
22.45 HP inner casing temp : 223
HP shaft temp : 202
HP casing top : 188
HP casing bottom : 280/291
23.0 MS Pr. Raised to 40kg/cm2 and temp to around 280c.MS
pr. Raised to hold the turbine at 20kg/cm2 when boiler
trapped and to reroll the turbine immediately, CBD closed
fully.
Boiler stopped H.P. turbine rolling stopped.
HP evacuation normalized

68
IP turbine CVs blocking removed
HPBP closed to 5%
Purge commenced.
23.10 Purge competed and boiler flashed.
MS pr : 34.75kg/cm2
MS temp : 288298
Speed : 563
Turbine reset after CRH pr. Reduced to 3kg/m2.
With LPBP
23.15 After speed falls to 300rpm LPBP (to stop MP roling on its
own CRH pr. Hold at 3kg/cm2) CBD opened, manual
injection valve opened
IP turbine rolling started with fixed HRH pr. Or 8kg/cm2,
with LPBP control HPBP opened at around 35%.
23.30 As the drum level make up is reduced due to initial steam
dumping from IP turbine, dearator level is increased.
Expander set point is raised to reduce feeding to dearator
(dearator pr.increased hence 11/6 by pass control valve
closed further)
23.45 As the flow to the dearator is not sufficient, dearator level

69
is falling, 2nd DM plant kept in service to increase flow to
expander to raise the Dearator level.
01.00 MS pr. : 31.81
MS temp : 274/283
IP top casing temp : 77.9
IP bottom casing temp : 77.9
IP shaft temp : 101
Speed : 500 rpm
1.20 Speed raised to 950 rpm
01.30 HPBP opened from 20% to 40% to dump more steam an to
quick fall of dearator CBP flow also closed by opening
CBP recirculation.
01.45 DM water to CP closed
CBP stopped
MS pr. : 28
MS temp : 275/285
IP top casing temp : 94
IP bottom casing temp : 79
IP shaft temp : 122

70
Speed : 950
02.0 Turbine tripped
CBO, attemperation manual valves, lanching manual
valve closed, vacuum idled by CEP discharge drain and
hot well drain is in progress, HP/BP gland steam valves
closed, hot well make up by FOT closed.
02.30 CEP stopped when hot well level alls 500mmwc, hot well
drain opened. BFP-A stopped,
BFP-B taken into service
BFP-A suction drain opened
02.40 Bearing gear taken into service
03.0 BFP stopped
Hot well draining completed
03.15 Hot well filled up to 1200 wc and CEPB & CEPC started
03.45 Hot well drain started
04.0 CEPs stopped
04.30 Hot well filled
CEP-6C started and dearator level normal and it is Tripped
due to suction/discharge temp. difference high.

71
6.20 BFP-5A started.
6.30 Boiler flashed.
6.35 DEA 8.44 6.4 0.045
CEP 7.8 2.6 0.028
08.55 Turbine rolling started to 1000 rpm.
MS pr. 71 kg/cm2, MS temp : 400/410
13.0 Unit synchronized
14.40 Unit tripped with furnace draft high
15.35 Unit flashed
17.30 Unit synchronized
After completion of washing of HP and IP turbine sections the axial shift of rotor is
decreased from 0.85 mm to 0.11 (on 26-02-03).
CHEMICAL VALVES DURING STEAM WASHING (HOT WELL SAMPLES)
TIME PH COND. SILICA PO4 REMARKS
18.30 08.45 10.32 0.035 Before steam washing

72
TIME
18.55
PH
09.82
COND.
47
SILICA
3.5
PO4
5.0
REMARKS
19.15 10.25 138 22.5 6.0 1
19.30 10.29 139 23.0 5.0
19.45 10.22 136 12.5 1.5 Speed raised to 500
20.00 10.15 132.5 12.25 1.0
20.15 10.08 112.9 10.0 10.0
20.30 9.96 92 8.22 4.2
20.45 9.85 74 6.50 1.5 Dumpingredused
21.00 9.82 78 7.0 1.0
21.15 9.06 76.5 7.0 1.0
21.30 9.75 74.6 7.0 1.0
21.45 9.97 67.2 5.5 0.5
22.30 9.6 52.4 3.50 0.3 Speed raised to 955
23.00 9.45 40.8 2.25 0.3
23.30 9.37 25.5 1.0 0.2 IPT rolling Started
24.00 9.1 11.8 0.7 Nil

73
CONCLUSION
In this project the various process i.e., ion exchange/ demineralization
process are used for removing hardness of water and condensate/wet steam
washing processes are used for removing the suspended solid particles/deposits
are may occurred on the blade surface the following conclusion are made.
1. From the graphs it is observed that the axial shift (+/- 0.65 mm limiting
value) after 5 months is 0.71 mm with limiting value of silica at 5 ppb. As
the axial shift crossed the limiting value the turbine is taken for washing
after steam washing the axial shift is reduced to 0.15 mm. Hence it is
concluded that the turbine can run it at least 5 months with the limiting
value of 5 ppb of silica in the feed water.
2. At lower loads the reduced quantities of steam from the extractions is not
maintaining the rotor in balanced position to avoid this inbalance the
turbine must be run at rated load (120 MW)
3. The Direction of the flow over the surface of the blade is improved by
removing the scales on the blades.
4. Erosion on the blade surface is prevented by allowing the silica in the
limiting value of feed water.
5. And finally the pressure/enthalpy drop, worked done is improved by
which efficiency of the turbine is improved.

74
BIBLOGRAPHY
1. POWER PLANT ENGINEERING BY S.DOMKUNDWAR
2. POWER PLANT ENGINEERING BY P.K.NAG
3. POWER PLANT ENGINEERING BY F.T.MORSE
4. TEXT BOOK OF POWER PLANT ENGINEERING BY RAJPUT
5. STEAM TRUBINES PRACTICE AND THEORY W.J.KEARTON
6. ENGINEERING CHEMISTRY BY JAIN & JAIN
7. KTPS MANUAL

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