Internship Progress report GTPS, CTW, SPS Internship Period: 4 week in GTPS, 3 weeks in CTW, 1 week in SPS (07-02-2018 to 07-04-2018)

1. Power plant
(GENCO 3rd)
U C E T ,
U O S , S A R G O D H A
0 7 / 0 4 / 2 0 1 8
Sections:
 GTPS
 CTW
 SPS

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Internship Progress report
GTPS, CTW, SPS
Internship Period: 4 week in GTPS, 3 weeks in CTW, 1 week in SPS
(07-02-2018 to 07-04-2018)
SUBMITTED BY:
ALI HASSAN (BMTF14E023)
HAFIZ AMEER HAMZA (BMTF14E067)
NOMAN ALI (BMTF14E082)
ADNAN AHMED (BMTF14E101)
ARSLAN MUNIR (BMTF14E110)
AHMED TAUSEEF (BMTF14E114)
B.S. MECHANICAL ENGINEERING TECHNOLOGY
CET, University Of Sargodha, Sargodha

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contents
1. Introduction 4
Thermal power complex Faisalabad 5
2. Gas turbine power station 5
Gas turbine at gtps 6
Main parts of gas turbine 6
Working principle of gas turbine 7
Brayton cycle 7
Fuel gas compressor 9
Gas turbine burns fuel 10
Generator and its working principle 10
Difference between ac and dc generator 10
Different parts of generator 11
Excitation system 12
Generator protection 13
3. Combine cycle plant 14
Heat recovery steam generator (hrsg) 14
Fundamental parts of hrsg 15
Hrsg module 16
Types of hrsg 16
Steam turbine 17
Steam turbine operation (ccp) 18
Turbine control room 18
4. Central turbine workshop 20
Sections of ctw 20
5. Steam power station (sps) 29
Component 29
Chemical dosing 30
Canal water 30
Cold storage tank 32
Force draft fan 32
Feed pump 32
Exhaust tower 32
Cooling tower 32
Seal oil unit 33
Chemical storage tank 33
Mechanical boiler 33
Basic power plant cycle 33
Firing 35
Heat source 35
Fuel 35

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Fluids 35
Circulation 35
Furnace position 35
Furnace type 35
Categorization of boiler 35
Drum 35
Super heater 36
Water walls 36
Economizer 36
Derator 36
Types of steam turbine 37
Associated system in power plant 38
Ways to increase the thermal efficiency of power plant 40
Losses during operation and maintenance of plant 42
Steam turbine operation 43
6. Fuel cost Rs/kwh 44

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INTRODUCTION:
After the creation of Pakistan, Electricity & irrigation Departments were established
in all provinces to deal with different development schemes in Water & Power Sectors. In
1959, an institution named Water and Power Development Authority (WAPDA) was
established to deal with these schemes. Since October 2007, WAPDA has been bifurcated
into two distinct entities i.e. WAPDA and Pakistan Electric Power Company (PEPCO).
WAPDA is responsible for water and hydropower development whereas PEPCO is vested
with the responsibility of thermal power generation, transmission, distribution and billing.
Under pepco, there are four power generation companies name:
 Jamshoro power company limited (jpcl) genco i
 Central power generation company limited (cpgcl) genco ii
 Northern power generation company limited (npgcl) genco iii
 Lakhra power generation company limited (lpgcl) genco iv
Power from these companies is transmitted to national transmission & power dispatch
company (ntdc) which transmits electricity to the whole country through eight distribution
corporate entities which are:
 Lahore electric supply company limited (lesco)
 Gujranwala electric power company (gepco)
 Faisalabad electric supply company (fesco)
 Islamabad electric supply company (iesco)
 Multan electric power company (mepco)
 Peshawar electric supply company (pesco)
 Hyderabad electric supply company limited (hesco)
 Quetta electric supply company (qesco)
 Northern power generation company limited (npgcl) genco – iii:
Northern power generation company limited owns and operates thermal power generation
facilities located at muzaffargarh, multan and faisalabad. Installed capacity of the generating
assets is 1,921 mw, which has declined over the years to dependable capacity of 1,169 mw.

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Thermal power complex, Faisalabad:
Thermal power complex is a part of NPGCL GENCO iii. It is
in Faisalabad at 10 km canal road. This power station consists of
three units:
1. Gas turbine power station (GTPS)
2. Combine cycle plant (CCP)
3. Central gas turbine maintenance workshop (CTW)
4. Steam power station (SPS)
1) Gas turbine power station (GTPS):
A gas turbine, also called a combustion turbine, is a type of internal combustion
engine. It has an upstream rotating compressor coupled to a downstream turbine, and a
combustion chamber in between.
Working of a gas turbine:
In its working, fresh atmospheric air flows through a compressor that brings it to
higher pressure. Energy is then added by spraying fuel into the air and igniting it so the
combustion generates a high temperature flow. This high-temperature high-pressure gas
enters a turbine, where it expands down to the exhaust pressure, producing a shaft work
output in the process. The turbine shaft work is used to drive the compressor and other
devices such as an electric generator that may be coupled to the shaft. The energy that is not
used for shaft work comes out in the exhaust gases, so these have either a high temperature or
a high velocity.
The purpose of the gas turbine determines the design so that the most desirable energy
form is maximized. Gas turbines are used to power aircrafts, trains, ships, electrical
generators, or even tanks. Because natural gas burns cleanly, it has become a popular fuel
to generate electricity. As a result of environmental concerns and technological advances,
natural gas power plants have become more appealing than coal or nuclear power
plants in some contexts.
the main components used to generate power in a gas turbine power plant are a
compressor, a combustor, and a gas turbine. Because they can be started up quickly, gas
turbines are ideal for meeting peak loading demands.

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Gas turbines at GTPS:
This power station has 8 simple gas turbine plants of 25 mw capacity each and
one ccp which has a capacity of 46 mw. Thus the total generation capacity of this power
station is 246 mw.
Fuel:
The fuel used here is gas or
high speed diesel. Liquid fuel is kept
in large tanks having a capacity of
storing 50,000 liters of fuel. The tank
has a solenoid valve for extraction.
Ac and dc pumps are used for
supplying fuel to the injectors which
then supply them to the combustion
chambers. In case of natural gas, the
pressure is maintained at 17-17.5kg
pressure.
Diesel is cleaned by a filter while a scrubber is used in case of natural gas.
Filter house:
Each of the 8 units has a filter house from where the air is filtered and supplied to the
compressor. These filters are air cleaned.
Start speed ratio valve:
This valve is used to control the flow of fuel. It operates on ehmc which is electrical control
for the fuel. It is given pressure ranges for sounding alarm and tripping in case the fuels
pressure becomes low. The pressure is measured using a pressure transducer which has
pressure input and voltage output.
Gas turbine:
Gas turbine functions in the
same way as the internal combustion
engine. It sucks in air from the
atmosphere, compresses it. The fuel
is injected and ignited. The gases
expand doing work and finally
exhausts outside. The only difference
is that instead of the reciprocating
motion, gas turbine uses a rotary
motion throughout.
The three main sections of the gas turbine are as follows:
Compressor:
The compressor sucks in air form the atmosphere and compresses it to pressures in the
range of 15 to 20 bar. The compressor consists of a number of rows of blades mounted on a
shaft. This is something like a series of fans placed one after the other. The pressurized air
from the first row is further pressurized in the second row and so on. Stationary vanes

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between each of the blade rows guide the air flow from one section to the next section. The
shaft is connected and rotates along with the main gas turbine.
Combustor:
This is an annular chamber where the fuel burns and is similar to the furnace in a
boiler. The air from the compressor is the combustion air. Burners arranged circumferentially
on the annular chamber control the fuel entry to the chamber. Each unit has 10
combustion chambers.
The hot gases in the range of 1400 to 1500°c leave the chamber with high energy
levels. The chamber and the subsequent sections are made of special alloys and designs that
can withstand this high temperature.
Turbine:
The turbine does the main work of energy conversion. The turbine portion also
consists of rows of blades fixed to the shaft. Stationary guide vanes direct the gases to the
next set of blades. The kinetic energy of the hot gases impacting on the blades rotates the
blades and the shaft. The blades and vanes are made of special alloys and designs that can
withstand the very high temperature gas. The exhaust gases then exit to exhaust system
through the diffuser. The gas temperature leaving the turbine is in the range of 500-550 °c.
The gas turbine shaft connects to the generator to produce electric power. This is
similar to generators used in conventional thermal power plants.
Working principle of the Gas Turbine:

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This cycle is recognized as the Brayton Cycle. This cycle occurs in all internal
combustion engines.
A brief summary of the Brayton steps are as follows:
1) Compression occurs between the intake and the outlet of the compressor (represented
by line 1-2). Pressure and temperature of the air increases.
2) Combustion occurs in the combustion chamber where fuel is mixed with the
compressed air and ignited. The addition of heat due to combustion causes a sharp
increase in volume (Represented by line 2-3).

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3) Expansion occurs as hot gasses accelerate from the combustion chamber. The gasses
at constant pressure and increased volume enter the turbine and expand through it
(Represented by line 3-4).
4) Exhaust occurs at the engine exhaust stack with a large drop in volume at a constant
pressure (Represented by line 4-1).
Fuel Gas Compressors:
Introduction:
4 FGC‟s are usually installed at CCP. The basic purpose of FGC installation is to
meet the gas pressure requirement of 46 bars for the gas turbine fuel requirement.
Stage # 1:
Gas comes from Gas yard into separator in which separates the moisture and
condensate present in the gas. Condensate is settling down in the separator and gas moves in
the suction bottle of the first stage compressor. First stage contains 2 cylinders having 3
suction and 3 discharge valves at each. Gas enters at 2.2 bar and discharge at 7.9 bar at
1100C temperature and accumulate in discharge bottle of first stage. Pressure safety valve is
placed between discharge bottle and inter cooler which sets at 17.2 bar.
After discharge bottle gas is passed through water cooler which lowers the
temperature and specific volume of the gas. Water cooler is the shell and tube type heat
exchanger having compressed gas in tube side and water at shell side.
Stage # 2:
After the inter-cooler Compressed gas is entered in the inter stage separator of 2nd
stage where gas and condensate separates. Gas is then enter in the 2nd stage cylinders where
it compressed down to the pressure of 18.4 bar, after compression temperature of gas is 124
0C. After compression gas comes in discharge bottle from where it follows into the heat
exchanger, having compressed gas on tube side and cooling water on shell side.
A pressure safety valve is placed between discharge bottle and inter cooler which sets
at 29 bar.
Stage# 3:
From the inter-cooler of second stage, gas is forwarded to the suction bottle of 3rd
stage cylinder where it further compressed to 46 bar and temperature of gas at this stage is
124 0C. 3rd stage cylinder has 4 suction and 4 discharge valves.
Compressed gas is then transferred to the heat exchanger having gas on shell side and
water on tube side. From heat exchanger compressed gas is transferred to discharge separator
which separates the gas and moisture from where it supplied into the discharge header
followed by a non returning valve and shut off valve.
A pressure safety valve is placed between discharge bottle and intercooler of 3rd
stage. Which sets at 52 bar. Blow down valve is also placed before inter cooler, used to
depressurize the system. A line from 3rd stage intercooler is also provided followed by the
two Pressure Control Valves for Fuel Gas recycling purpose. Recycle systems connects the
outlet of 3rd stage cooler to inlet separator before PCV.

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Gas turbine burns fuel:
The gas turbine compresses air and mixes it with fuel that is heated to a very high
temperature. The hot air-fuel mixture moves through the gas turbine blades, making
them spin. The fast-spinning turbine drives a generator that converts a portion of the
spinning energy into electricity.
Generator:
Synchronous generator is used to convert mechanical energy into electrical energy.
Basic Working principle:
According to Faraday‟s law of
electromagnetic induction: “If there is a
relative motion between conductor and
magnetic field, then an EMF will be induced
into the conductor”. To create this relative
movement, it does not matter whether the
magnet is rotating and the conductor is
stationary or the conductor is moving and
magnet is stationary. The magnitude of the
induced EMF is directly proportional to the
No of conductors (N) and the rate of change of
magnetic flux crossing the conductors.
E = N (dΦ/dt)
Difference between AC generator and DC generator:
There is one main difference between an AC and DC generator. In DC Generator, the
armature rotates but the field system remains stationary but in AC generator, the case is
reverse because here armature remains stationary but field winding rotates.
The general thing to keep in mind in this reference is that armature is a thing, which produces
alternating magnetic field. Therefore, in DC, this magnetic field is being produced by rotor,
which is called the armature, and in AC, this remains stationary and here it is called the
stator.
The stator consists of a cast iron frame, which supports the armature core having slots
on its inner periphery for housing the armature conductors. In a slip ring induction machine
the rotor, winding terminals are coming out and then they are supplied with a DC supply to
produce the stationary magnetic field, which is converted into the rotating magnetic field by
rotating the rotor by an external source, which is called the prime mover.
When the rotor rotates, the stator conductors are cut by magnetic flux, hence they
have an induced EMF produced in them. As magnetic poles are alternately N and S, they
induce an EMF and hence current starts flowing in armature conductors, which first flows in
one direction and then in the other. Hence, alternating EMF is produced in the stator
conductors whose frequency depends on the No of N and S poles moving past a conductor in
one second and its direction is given by Fleming‟s right hand rule:

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Different Parts of Generator:
The two-pole generator uses directly air-cooling for the rotor winding and indirect air-
cooling for the stator winding. All types of losses (iron, friction, windage, stray and etc) are
also dissipated through air. Generally a generator consists of following parts:
 Stator
 Rotor
 Excitation system
 Carbon brushes and Slip rings
 Retaining rings
 Bearing
 Rotor grounding system
 Cooling system
Stator:
It is a stationary part of the generator. The stator has two main components:
Stator frame,Magnetic core,Stator winding,Stator End shields
Stator frame:The frame is for to support the laminated core and winding and also for to
increase the mechanical strength of the machine. It is the heaviest part of the generator. Air
ducts are provided for the rigidity of stator frame. End shields are also bolted to this frame.
For the foundation purposes feet are provided.
Electrical connection of bars and Phase connectors: Electrical connection between the top
and bottom bars is made by brazing. One top bar strand being brazed to one strand of
associated bottom bar, so that the beginning of each strand is connected without having any
electrical contact with the remaining strands. This connection offers the advantage that
circulating current losses in the stator bars are kept small.
The phase connectors consists of flat copper sections, the cross section of which results in a
low specific current loading. The ends of each phase are attached to the circular phase
connector, which leads from winding ends to the top of the frame. The phase connectors are
mounted on the winding support, using clamping pieces and glass fabric tape.
Rotor:
It is the rotating part of the generator. It is driven by the turbine and it creates rotating
magnetic field. There are two types of rotor:
 Cylindrical type
 Salient-pole type
The cylindrical type rotor is used in turbo alternators and a having a uniform air gap.
Normally it is used in all types of thermal power stations where the rotating speed of rotor is
high like 3000 rpm in PAKISTAN. For 3000 rpm, it has two poles. The field winding is
accumulated in slots on the solid rotor.Salient pole rotors are used for low speed operation
like about 167 rpm for 50 Hz. For this arrangement, we use 36 poles of the rotor.
Rotor has the following main components:
Rotor shaft: The rotor shaft is made of single gorging whose ingot is made in an electric
furnace and then vacuum cast. The rotor consists of an electrically active portion and the two
shaft ends. A forged coupling is used to couple the rotor to the turbine. The longitudinal slots

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hold the field winding. Slot pitch is selected so that two solid poles are displaced by 180°
electrical. In these slots field coils are milled into shaft body and is arranged so as to generate
magnetomotive force wave approaching a sine wave. Rotor teeth are provided with axial and
radial ducts enabling the cooling air to be discharged into the air gap for intensive cooling of
the end winding. Rotor winding: Rotor winding has also two distinct parts: The shaft
contained in shaft body. The part outside the shaft body.
The rotor winding consists of several coils, which are inserted into the slots, and series
connected such that two coil groups form one pole. Each coil consists of several series
connected turns, each of which consists of two half turns which are connected by brazing in
the end section. Strips of laminated glass fabric insulate the insulated turns from each other.
The edges of slots are made up of high conductivity material and they are there to act as
damper winding. At the ends, the clots are short-circuited by retaining rings.
Rotor fan: The generator cooling air is circulated by two axial flow fan located at the end of
the shaft. To argument the cooling of the rotor winding, the pressure established by the fan in
conjunction with the air expelled from the discharge port along the rotor. The moving of the
fan have threaded roots for being screwed into the rotor shaft. Threaded roots fastening
permits the blade angle to the required level.
Excitation system:
The excitation system is to supply the direct current to rotor which allows the
generator to maintain a controlled voltage between its terminals when connected to the
network. A voltage regulator drives the excitation system. The excitation power for the
generator is supplied by an exciter with rotating diodes that are fitted at the end of main
generator shaft.
The excitation voltage is developed by rotating Diode Bridge that supplies the rotor winding.
These rectifying diodes are given supply by an excitation transformer of which the primary
winding is supplied by the main generator. Then a three-phase thyrister bridge rectifies the
secondary winding.
Generator cooling system: The heat losses arising in the generator interior are dissipated to
the secondary coolant (cooling water) through air. Direct cooling of rotor removes hot spots
and differential temperature between the adjacent components. Indirect cooling is used for
stator winding.
Air and hydrogen are two cooling media for the generator cooling. The field and armature
copper losses are evacuated by air/ hydrogen gas flowing inside the generator. The axial fans
circulate the air. In KAPCO all generators are air cooled. Advantages of Air-cooling: lower
cost price Easy maintenance Short inspection Air cooling circuit: Cooling air is circulated in
the generator by two axial-flow fans on the rotor shaft. Cold air is drawn by fans from cooler
and then divided into three parts:
Flow path 1:
It is directed into the rotor end winding and cools the rotor winding. Along this path heat of
the rotor winding is directly transferred to the cooling air.
Flow path 2:
It is directed over the stator end winding to the cold air ducts and in the stator frame space
between the generator housing and the stator core.

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Flow path 3:
It is directed into the air gap via the rotor retaining rings. This path mainly cools the rotor
retaining rings, the end of the rotor body and end portion of the stator frame. Then this flow
of air is mixed up in air gap from where it goes for the cooling of the other remaining portion
of the stator core and the stator winding. The hot air is returned to the cooler via hot air ducts
re-cooling and draws again by the fans.
Generator protection:
There are different types of fault can occur on to the generators so the protection of
these faults to the generators we used some protections. These are giving below.
 Negative phase sequence protection.
 Rotor earth fault protection.
 Loss of excitation.
 Reverse power protection.
 Differential protection.
 Under frequency/over frequency relay.
 Stator over current protection.
 Stator over voltage protection.

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2) Combined cycle plant (CCP):
There is a combined cycle plant (CCP) at this power station which has a
generation capacity of 46 mw. The exhaust of gas turbine has a temperature around
450 degrees centigrade. So, at the exhaust of four gas turbine units a “heat recovery”
system is installed so that this high temperature exhaust is not wasted. This is how a
combined-cycle plant works to produce electricity and captures waste heat from the gas
turbine to increase efficiency and electrical output.
Heat Recovery Steam Generator (HRSG)
Introduction:
As the natural gas is burned in the single annular combustor of the LM6000 gas
turbine, it is a well-known fact that the exhaust temperatures would be high and letting the
exhaust gas into the environment would be a waste of energy. The HRSG is installed here at
the CCPP which utilizes the high exhaust temperatures to convert water from the RO to
superheated steam which powers the 25MW steam turbine.
Heat recovery system captures exhaust:
A heat recovery steam generator (HRSG) captures exhaust heat from the gas turbine
that would otherwise escape through the exhaust stack. The hrsg creates steam from the gas
turbine exhaust heat and delivers it to the steam turbine.

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steam turbine delivers additional electricity:
The steam turbine sends its energy to the generator drive shaft, where it is converted
into additional electricity. The exhaust gases from unit number 5, 6, 7 and 8 are used to
generate electricity using the combined cycle. This increases the efficiency of electricity
generation by almost 50%.
The steam turbine has two different stages, LP turbine and HP turbine. So the steam
generated at the HRSG is for both the LP and HP turbines, the only difference is the pressure
that is maintained.
Fundamental parts of HRSG:
Four basic HRSG components are:
1. Evaporators (Gas to wet steam heat exchanger)
a. HP Evaporator and LP Evaporator
2. Economizers (Gas to water heat exchanger)
a. HP economizer 1 & 2 and LP Economizer
3. Superheaters (Gas to dry steam heat exchanger)
a. HP Superheater and LP Superheater
4. Preheater (gas to water heat exchanger)
a. Condensate Preheater
Figure 13: Serrated Finned Tubes

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HRSG Modules
Preheater
HP Economizer 1
LP Economizer
LP Evaporator
HP Economizer 2
LP Superheater
HP Evaporator
HP Superheater
Types of HRSG
There are three main types:
1. Natural Circulation HRSGs
2. Forced Circulation HRSGs
3. Once Through HRSGs
The one used at Korangi CCPP is the Forced Circulation HRSG where the exhaust
gas glows vertically and the water/steam flows horizontally and uses serrated fins on its
tubing to maximize heat transfer (See Figure 13 on previous page).
Forced Circulation HRSG Operation:
Feedwater from the RO Plant enters the HRSG from the top where it first goes
through the Economizer where the water is preheated and directed to the respective steam
drums (LP and HP steam have different drums and different HRSG components). Since the
steam is less dense as compared to water, it rises and the water accumulates at the bottom.
The water at the bottom of the tank is pumped to the evaporator where saturated steam is
made and then returned again to the steam drum. The superheated steam is pumped to the
superheated, located at the very bottom since high temp. are required, where dry superheated
steam is produced and pumped on to the steam turbine. The HP drum is maintained at a
pressure of 54 bar and the LP turbine is maintained at a pressure of 8 bar.
The LP drum and HP drum are dozed with LP phosphate and HP phosphate
respectively and also with ammonia and oxygen. This maintains the pH levels at approx. 9.5
and eliminates the possibility of corrosion in the steam turbine.
Figure 14: Schematic of
Forced Circulation HRSG

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Steam Turbine
Overview:
Max load: 25MW
RPMs: 4500
Stages: 9 Overall; 6HP & 3LP.
Operation Overview:
The steam turbine operates on the rankine cycle where superheated steam is generated and
pumped into the steam turbine which rotates and drives the load, the generator. The two
different stages of the steam turbine requires different steam pressure and depending upon the
load a valve controls the amount of steam that enters the HP and LP turbine. The valve

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reduces the steam that enters the HP turbine to about 10-12 Bar. After expanding through the
turbine the steam pressure drops to about 2-3 Bar and this is where LP steam is enters. Since
the steam turbine operates on a closed cycle, the exhaust steam is condensed and pumped
back to the HRSG to be superheated and used again in the steam turbine.
Operation:
Central turbine control room:
There is a central control room which controls the operation of all the plants. In this
plant, there is the whole system installed which starts the system and synchronize it. For
synchronization, a synchroscope is there. There are total four bus bars in this control room
which receives the power from the gas turbine generators:
Moreover, in there we have an excitation system which is used to excite the generator coils to
start. This control room is concerned with the working of gas turbines (GTS).
CCP control room
The hrsg unit is used to run an additional steam turbine. The working of this steam
turbine is controlled from another control room. In this control room the whole working and
transmission of hrsg & steam generator is controlled. Computerized system is installed here.
There is a digital control system in which there is complete schematic diagram of hrsg
system. And from here manually, the working of this system is controlled. Apart from this
digital system, there is also an analogue control.

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Moreover, to control the transmission of output power there is also a system installed similar
to that in the central control room.
Transmission:
After the generation the electricity that is of vary high amperage is transmitted using a
very high capacity cable to the transformers. The transformers step up the electricity to 132kv
which can then safely be transmitted to the grid station.
The turbine starting speed is 1000 rpm. Starting devices are used to initiate rotation which
runs on diesel or electricity. Each starting device has a power of 500 hp. The speed is
gradually increased to obtain the operational speed of 5100rpm after which the turbine is
coupled to the generator. The generator is to be run at 300 rpm so the decrease in rpm is done
using a larger diameter gear at the generator.
Turbine Control rooms
To control the working of turbines & other systems and production & transmission of
electricity, control rooms are installed. In each turbine there is a control room to control room
from where the plan is initiated and brought to its operational speed of 5100 rpm. The turbine
is operated by a 125 v supply. Other than these there are two control rooms:

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3) Central turbine Workshop (CTW):
This workshop was established by wapda-pakistan in 1983 and was expanded in
1995. This workshop is capable to provide repair facilities to all power stations (locally &
globally) all the turbine hot gas path components are made of high temperature (nickel &
cobalt) alloys of ge frame-5 & frame-9 machines can be repaired here.
Mission of workshop:
Save the money and develop the country
Description of the working:
Repair jobs are received in this workshop from all wapda/pepco power houses
(thermal & hydral), ipp‟s, kesco, kapco, ppl and another private sector also. The expansion of
this workshop was carried out to meet with the repair needs of the power houses. At present
this is the single largest repair workshop ever in pakistan. Repair of all power plants turbine
rotors, re-winding of generator rotors, re-winding of all kind of motors, ndt (nondestructive
test) available, all types of welding, re-babbiting of all types of bearings, heat treatment the
turbine parts in vacuum furnace, sand blasting, balancing of all type of rotors is done in this
workshop.
Sections / shops:
The workshop is divided into different sections / shops to perform different operations.
There are
 Cleaning shop
 Non-destructive testing (ndt) shop
 Tig welding shop
 Grinding shop
 Electric and gas welding shop
 Machine shop
 Bearing and re-metaling shop
 Balancing shop
 Chemical lab
The description of the following is given below:
Cleaning shop:
When a job is received in the workshop its condition is such that it is covered with
rust, oil, grease or such other things because of its continuous running in the turbine. So, first,
job is brought to this shop where oil, grease, rust and hard scaling also is removed. In this
shop, there are five machines.
Vapor degreasing plant:
This plant is used for removing oil and grease. Fumes of trichloroethylene are produced in a
tank and job is suspended in the closed tank. Fumes of trichloroethylene make the oil and

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grease soft and the fell in the tank. Chemical is heated up to 87°c to make fumes. While
410°c is its flame temperature.
Steam jet cleaner:
Steam cleaning involves using steam for cleaning. Its uses include domestic applications in
cleaning flooring and household dirt removal, and industrial uses in removing grease and dirt
from engines.
Vapor blasting machine:
Air+water+al2o3 mixture is used to remove rust and scales from the surface of the job.
Mixture comes out of the nozzle with pressure to remove rust. A pump is used to
continuously mix the mixture in a tank.
Vacuum blasting machine:
It is same as previous machine the difference is that no water is used in the mixture. It is
called as vacuum blasting machine because for smaller jobs a separate container is used in
which the job is blasted with the mixture. Chemical fell into the container where it is taken to
the machine through a vacuum pump. This save our expensive chemical
Open dry blasting / sand blasting machine:
It is a simple machine which uses a mixture of sand and air to remove stains from job with
pressure.
“for all blasting machines carbide nozzles are used because these do not get destroyed with
high speed moving particles.”
Non-destructive testing shop (NTD shop):
After cleaning the job is taken to this shop where it is examined to find any cracks and
breakage both internally and externally. First the job is tested visually then it is passed
through different tests. This test no destructs the material.
Surface testing:
For surface testing, we have following two tests
Penetrate test (PT)
In this test a penetrant is used to identify cracks and a
developer is used to visualize them.
It has further two methods.
Dye PT (day light test)
In this test a red liquid (penetrant) is used. It is sprayed over
the job and dried for 1 hour. After that it is washed with
ordinary water then a developer is sprayed which reacts with
penetrate which has been penetrated the cracks to give red color, which identify the cracks
and mark these cracks.
zyglo PT (dark light test)
In this test a greenish oil (penetrant) is used. Job is dipped in the oil (self-emulsifying oil).
After that it is washed with ordinary water with pressure and takes to the drying tank where
heaters are present for drawing. Then a fluorescent powder (zyglo) is present in a tank, job is
suspended in the tank and through a fan chemical is made to cover the whole job which reacts

23. 22 | P a g e
with penetrant which has been penetrated the cracks to give green color, which identify the
cracks, but these cracks can only be visualized in ultraviolet light in the dark.
Magnetic particle inspection
In this test first job is magnetized by passing current through it having low voltage and high
current. Before that a white paste is painted on all over the job. Then a solution of iron
particles is sprayed over the job for day light test it is ferro flux and for dark light test it is flu
flux. Where there are cracks, the solution remains as it is because there is a break in magnetic
field in cracks. So, this solution can be visualized after drying
Internal cracks testing by ultrasonic inspection
For testing internal cracks ultrasonic test is used. First job and ultrasonic set is calibrated.
Then sound waves are passed through the job where there are cracks the waves are reflected
before passing through the whole job, in this way crack is detected. For detecting the position
of the crack sound waves are passed at different angles.
Argon welding shop (TIG welding)
Tig stand for (tungsten inert gas). Tig welding or argon welding uses argon as shielding gas
and an electric spark to create heat for welding. Job after testing in ndt and then grinding shop
comes in welding shops where they are repaired through welding where required.
Temperature of tig welding is different for different material maximum temperature is 3200 c
and minimum temperature is 50c. In this shop, super alloy material can be welding.13 types
of material can be welding in this workshop. Clean filler rod is used in this shop it means it is
without powder. Same type of filler rod is used for only same type material welding. There is
no need grinding after welding. Thickness of filler rod is start from .8mm to 3.2mm.
Advantages of tig welding
. Advantages of tig welding are that the weld is very clear, strong and long lasting. It gives
fewer sparks. But the disadvantage is that tig welding is expensive.
Welding torch
Welding torch is shown in the figure,
having the following parts
 Tungsten rod
 Ceramics nozzle
 Cap
 Gas valve regulator
 On/off switch
 Four pipes are coming to the welding
torch.
1st pipe has current carrying wire for on/off switch.
2nd has argon for shielding.
3rd has current carrying cable for heating, welding and water carrying copper tube for
cooling.
4th has hot water which goes to the cooling tank d.
Welding plant is d otc it works on both dc and ac supply. This plant can do tig, spot and
electric arc welding. Fish tails are welded in this shop x.

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Electric and gas welding shop
this shop electrical arc welding and oxy-acetylene gas welding is done on broken jobs.
First v-groove is made between two welded materials and filler is inserted between those
grooves. Grooving is done for proper filling of the metal and for strengthening purposes.
Electrical arc welding
In this high electric voltage is used to melt the metal and a specific electrode is used to pass
current
Welding electrodes
Welding electrodes are metal wires with baked on chemical coatings. The rod is used to
sustain the welding arc and to provide the filler metal required for the joint to be welded.
Standards and codes (asw)
The american welding society (aws) numbering system can tell a welder quite a bit about a
specific stick electrode including what application it works best in and how it should be used
to maximize performance. With that in mind, let's look at the system and how it works.
The general asw standard is
E 60 1 10
Electrode
Tensile
strength
Position
Type of coating and
current
The prefix "e"
Designates an arc welding electrode.
Minimum tensile strength
The first two digits of a 4-digit number and the first three digits of 5-digit number indicate
minimum tensile strength. It is in kilo pounds per square inch.
Position
The next to last digit indicates position. The "1" designates an all position electrode, "2" is for
flat and horizontal positions only; while "4" indicates an electrode that can be used for flat,
horizontal, vertical down and overhead.
Current type and coating
the last 2 digits taken together indicate the type of coating and the correct polarity or
current to use.
Digit Type of coating Welding current
0 High cellulose sodium Dc+
1 High cellulose potassium Ac, dc+ or dc-
2 High titania sodium Ac, dc-
3 High titania potassium Ac, dc+
4 Iron powder, titania Ac, dc+ or dc-
5 Low hydrogen sodium Dc+
6 Low hydrogen potassium Ac, dc+

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7 High iron oxide, iron powder Ac, dc+ or dc-
8 Low hydrogen potassium, iron powder Ac, dc+ or dc-
DC and AC electrodes
A dc machine produces a smoother arc. Dc rated electrodes will only run on a dc welding
machine. Electrodes which are rated for ac welding are more forgiving and can also be used
with a dc machine. Here are some of the most common electrodes and how they are typically
used.
Oxy-acetylene gas welding
Oxy-fuel welding (commonly called oxyacetylene welding, oxy welding, or gas welding in
the u.s.) and oxy-fuel cutting are processes that use fuel gases and oxygen to weld and cut
metals, respectively. The apparatus used in gas welding consists basically of an oxygen
source and a fuel gas source (usually contained in cylinders), two pressure regulators and two
flexible hoses (one for each cylinder), and a torch. This sort of torch can also be used
for soldering and brazing. The cylinders are often carried in a special wheeled trolley.
Non-return valve
Acetylene is not just flammable, in certain conditions it is explosive. Although it has an upper
flammability limit in air of 81% acetylene's explosive decomposition behavior makes this
irrelevant. If a detonation wave enters the acetylene tank, the tank will be blown apart by the
decomposition. Ordinary check valves that normally prevent back flow cannot stop a
detonation wave because they are not capable of closing before the wave passes around the
gate. For that reason, a flashback arrestor is needed. It is designed to operate before the
detonation wave makes it from the hose side to the supply side.
Types of flames
There are three basic flame types: neutral (balanced), excess acetylene (carburizing), and
excess oxygen (oxidizing) as shown below. A neutral flame is named neutral since in most
cases will have no chemical effect on the metal being welded. A carburizing flame will
produce iron carbide, causing a chemical change in steel and iron. For this reason, a
carburizing flame is not used on metals that absorb carbon. An oxidizing flame is hotter than
a neutral flame and is often used on copper and zinc.
Welding torch flame types
carburizing flame (less o2) neutral flame (50% o2) oxidizing flame
(more o2)

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Grinding shop:
When non-destructive testing is done, job is taken to grinding shop. In grinding shop
surface is polished and defected parts are cut or removed, parts are also for making v groove
for welding. For this carbide tools are used which are fixed on rotating grinders these
machines are basically of two types.
Electrically operated
Electricity is used to operate these machines but these cannot be used for longer time because
these get heated shortly.
Air operated
Compressed air is used to run the rotor of these machines. These can be used for longer time
and speed can be regulated easily.
Grinder types based on cutting angle are
Straight grinder angular grinder
Grinding burrs
The tool head attached to the grinder which removes the material is called burr. Following are
commonly used types of burrs:
 Oval/tree shape
 Ball shape
 T shape
 Flap wheel
Disks
The disks used are of three types, i.e.
 Cutting disk
 Grinding disk
 Flap disk
There is one of the best grinding burr is nomadic burr which
Cannot heat easily and we can work till 24 hour. Ans we can
also change the speed of the nomadic burr.
Machine shop:
Machine shop includes several machines. All machining is used for doing operation
on the job. Following machines are present in this shop .

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Heavy duty lathe machine
It has following specifications
Chuck dia 1755 mm
Swing on carriage length is 1880mm
Swing on bed length is 2200mm
Length center to center is 7000mm
Max weight it can support is 22 tons
Made in spain
Facilities threading, boring, turning,
Facing
vertical boring machine
It has following specifications
Boring spindle diameter 110 mm
Bore depth is from 150-1000 mm
Facilities turning, facing and drilling
Boring spindle transverse 600 mm
Weight 2000kg
Made in china
Mascon lathe machine
It has following specifications
Bed length is 3240mm
Chuck dia is 600mm
Made in germany
Vertical lathe machine sc 33
It has following specifications
Chuck dia is 3300mm
Max transverse length is 2300mm
Max weight it can support is 35000kg
Made in Romania
Cnc lathe machine
It has following specifications
Chuck dia is 4000mm
Swing on bed 4200mm
Length center to centre 15000mm
Job holding capacity =100 tons
Made in china

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There other machines as well like universal milling machine, slaughter machine and
surface grinding machine.
Bearing re-metaling shop
Bearings coming from different power stations are repaired in this shop. On the inner
surface of bearing a soft material is deposited to save the shaft this material is called babbitt.
After that bearing is taken to the machining shop for surface finishes.
Babbitt
It is a tin based alloy with 88% tin, 5% copper, 4% antimony and 7-8% lead.
Bearing is first heated up to 250°c to first remove the worn-out metal then new metal which
is babbitt is either welded or casted on the inner surface of the bearing.
Balancing shop:
In this shop, unbalanced parts are operated to turn them into balanced ones.
Unbalance exists in a rotor when the mass center axis is different to its running center axis.
Practically all newly machined parts are non-symmetrical due to blow holes in castings,
uneven number and position of bolt holes, parts fitted off-center, machined diameters
eccentric to the bearing locations etc.
To identify the position and amount of unbalance, balancing machines are used by a rotor
manufacture to correct any unbalance that exists. These machines are so sensitive that they
can easily and accurately identify any mass axis 0.001mm off the running axis.
The balancing machine used at ctw is of a german company schenck. It has a rotor weight
range of 2500-60000 kg (60 ton) while a maximum length of 8 meters. After detection if
mass is required some where it is welded there and if mass is required to remove it is
removed through grinding. The job is fit in balancing machine by coupling.
Max. Length of rotor 8000 mm
Max. Dia of rotor 4000 mm
Rotor journal dia 40-900 mm

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Chemical lab:
Here in this lab metals are testes to assign appropriate electrode for welding and other
purposes.
Cleaning:
Also in chemical lab, cleaning of job is done to some extent. For cleaning metal is dipped in
heated chemicals for 1 hour then they are washed with tap water these chemicals remove
scales from the surface of job. There are three tanks having different chemicals i.e.
4181(alkaline base) remove oil and grease.
4338(alkaline base)
493(acidic form) mistake
Some inhibitors are added to prevent reaction of the chemicals with metal.
Metallurgical equipment’s
Following equipment‟s are present in this lab for analyzing the alloys.
Alloy analyzer
Atomic or x-ray source is used here to analyze the chemical composition of an alloy. We can
get print of the percentage chemical composition of any alloy. Its rays should be kept away
from the skin.
Non-portable alloy analyzer
It works same as previous one but metal must be cut first then it should be placed in the
analyzer.
Some other equipment
There are some other equipment‟s too working in this lab, which are
Digital boroscope
Hardness tester
Rockwell hardness tester
Induction furnace

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4) Steam power station (SPS):
A steam power station is a power station in which the electric generator is steam driven.
Water is heated, turns into steam and spins a steam turbine. After it passes through the
turbine, the steam is condensed in a condenser. The greatest variation in the design of steam-
electric power plants is due to the different fuel sources. Almost all coal, nuclear, geothermal,
solar thermal electric power plants, waste incineration plants as well as many natural gas
power plants are steam electric. Natural gas is frequently combusted in gas turbines as well as
boilers. The waste heat from a gas turbine can be used to raise steam, in a combined cycle
plant that improves overall efficiency. Worldwide, most electric power is produced by steam-
electric power plants, which produce about 86% of all electric generation.
The power station at faisalabad has 2 units, each of a generating capacity of 66 mw (132 mw
total), although due being more than 40 years old, its capacity is reduced to about 40 mw
each (80 mw total).
Components:
Some important components of the steam power plant are described below:
Reverse Osmosis (RO) Plant
Introduction:
The reverse osmosis plant here at the Korangi Combined Cycle Power Plant is used to
treat sea water by passing it through semi-permeable membrane under high pressure. The
final product (Permeate Water) is used for various applications such as for cooling and in the
HRSG for steam generation.

31. 30 | P a g e
Osmosis is phenomena that occurs naturally in which a solution that is less
concentrated will migrate to a solution with high concentration through a semi-permeable
membrane. Where as in reverse osmosis an external force is applied to the high concentration
solution which passes through a semi-permeable membrane that allows the passage of water
molecules but not the majority of the salts ect. To achieve this, the force applied should
generate pressure more than the „Osmotic Pressure‟ to initiate the reverse osmosis
phenomena.
There are two stage systems common to the RO plant, single and double stage
systems. Single stage is fairly simple, the feed water enters as one stream and exists the RO
as permeate water from one side and condensate from the other. In the double stage the
concentrate of the first stage becomes feed water for the second stage. By increasing the
stages the recovery from the system increases.
Also used are the single and double pass system. The single pass system is the same
as the single stage system. Where as in the double pass system the permeate of the first pass
becomes the feed water to the second pass which produces a higher quality permeate water.
Chemical Dosing:
Five different types of chemical dosing are done in the feed water in order to minimize the
fouling, scaling, chemical attacks and biological growth. Two dosing are done before the
Multimedia Filters and three are done after the multimedia filters.
 Coagulant/Ferric Chloride Injection System: This promotes the clumping of particular
matter in water, forming a larger size and thus promoting settling of particulates and
clarification of the water.
 Flocculants: An electrolyte added to a colloidal suspension to cause the particles to
aggregate and settle out as the result of reduction in repulsion between particles.
 Sodium Meta-Bisulfate Injection System: This is used to remove the presence of
chlorine.
 Caustic Injection System: Sodium Hydroxide is injected in the system to increase the
pH of the water to approx. 6.4 for the intermediate tank.
 Anti-Scalant Injection System: Anti Scalant is used to stop and remove the formation
of scaling in RO membranes.
Sea Water Reverse Osmosis System:
This system mainly consist of:
 Cartridge filters
 HP Multistage pump
 Booster Pump
 ERD System
 18 Membrane modules
After passing through the Bernoulli filters and getting the first and second chemical dozing,
the water enters the main RO system where it passes through the 7 Multi Media Filters
(MMF). A MMF contains eight layers of media consisting of stones, white gravel, purple

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garnet, white sand, brown sand, pink garnet, purple garnet and anthracite coal. The feed water
enters from the top, passes through the media and is collected at the bottom. After passing
through the MMF, the water enters the cartridge filters (having 82 propylene filters rated at 5
Microns). Two lines are extracted from the cartridge filter housing where one line supplies
water to high pressure pump inlet and the other one is going to ERD (energy recovery
deceive) inlet. Each module contains 7 members and at the inlet of the membranes the
pressure is about 52 bar which is increased by the help of a high pressure multistage pump. In
the RO membranes water is divided into two streams, ones is permeate and the other one is
concentrated water (waste product). The permeate is transferred to the Intermediate tank
where it has a conductivity of 400-500μs/cm (compared to 55,000μs/cm at the start). The
concentrated water goes to the EDR inlet where high pressure concentrated water runs a
turbine and transfers it pressure to the Low pressure Sea water which comes in the EDR from
the cartridge filters. The high pressure water leaving the EDR passes through a booster pump
which raises the pressure to 54 bar from where it is supplied to the inlet of the RO
membranes.
Figure 16: Sea Water RO Modules

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Permeate Water RO System:
After the SWRO the permeate water is stored in an intermediate tank from where it is
supplied to PWRO system by the PRWO supply pumps. After passing through the 3 microns
rated filters water enters the booster pumps which raise the pressure of the water and feed it
into the 12 PWRO modules (containing 4 membranes each) yielding in the permeate water
having a conductivity of approx. 10μs/cm. The permeate water from the PWRO enters the
EDI machine which removes the ionic impurities by the electro deionization method. The
final product water has a conductivity of 0.075 μs/cm and is then stored in demin tank and 3
KPTS tanks as a backup. From here the water is supplied in two streams. The first stream
supplies water to GT-1 and GT-2 operational tanks, Skids and serge tank for evaporator
chillers and the Second stream supplies water to closed cooling first filling and hot well of
steam turbine.
Cold storage tank:
This is a tank which stores cold raw water which is used by condenser and other
components for cooling purpose.
Fd fan:
A forced-draft (fd) fan is a type of pressurized fan
that gives off positive pressure within a system. It is
mainly used in industries that employ boiler systems
in order to promote boiler efficiency, but it has a
wide range of applications. Typically, outlet and
inlet dampers are utilized in order to maintain the
pressure in the system. A common fd fan has a
wheel at the center that hangs on a shaft along with
integrated inlet boxes.
Feed pump:
A boiler feed-water pump is a specific type of pump used to pump feed-water into a steam
boiler. The water may be freshly supplied or returning condensate produced as a result of the
condensation of the steam produced by the boiler. These pumps are normally high pressure
units that take suction from a condensate return system and can be of the centrifugal pump
type or positive displacement type:
Exhaust tower:
The exhaust tower is used as an outlet for the residual gases coming after combustion from
the boiler chamber.
Cooling tower:
Acooling tower is a heat rejection device which rejects waste heat to the atmosphere
through the cooling of a water stream to a lower temperature. Cooling towers may either use
the evaporation of water to remove process heat and cool the working fluid to near the wet
bulb air temperature or, in the case of closed circuit dry cooling towers, rely solely on air to

34. 33 | P a g e
cool the working fluid to near the dry-bulb air temperature. The cooling towers used
here are made of wood which makes then light in weight and results in faster cooling. Each
tower has 4 fans. Each fan has 8 blades and weight of each blade is about 38 kg. These
blades are at an angle of 9-9.5o. The valve used for water is a distribution valve. The water is
sprinkled downwards and is cooled on its way down by the upcoming air.
Seal oil unit:
This unit provides the lubricating oil to the bearings and needs to be in operation all
the time otherwise the hydrogen gas and other gases used for cooling and other purposes
might escape resulting in exposure to atmosphere which can result in an explosion.
Chemical storage tanks:
These tanks store different chemicals used at various components of the plant.
Mechanical boilers:
The boilers used are water-tube type. A water-tube boiler is a type of boiler in which water
circulates in tubes heated externally by the fire. Fuel is burned inside the furnace, creating hot
gas which heats water in the steam generating tubes. In smaller boilers, additional generating
tubes are separate in the furnace, while larger utility boilers rely on the water filled tubes that
make up the walls of the furnace to generate steam. Each boiler has 2 chambers, each having
4 burners. These boilers are lined inside with pipes through which water flows.
Basic power plant cycle : rankine cycle
The Rankine cycle is a cycle that converts heat into work. The heat is supplied
externally to a closed loop, which usually uses water. This cycle generates about 80% of all
electric power used throughout the world, including virtually all solar thermal, biomass, coal
and nuclear power plants. It is named after William John Macquorn Rankine, a Scottish
polymath. The Rankine cycle is the fundamental thermodynamic underpinning of the steam
engine.

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Boiler: A boiler is the central or an important component of the thermal power plant which
focuses on producing superheated steams that is used for running of the turbines which in
turn is used for the generation of electricity. A boiler is a closed vessel in which the heat
produced by the combustion of fuel is transferred to water for its conversation into steam of
the desired temperature & pressure. The heat-generating unit includes a furnace in which the
fuel is burned. With the advantage of watercooled furnace walls, super heaters, air heaters
and economizers, the term steam generator was evolved as a better description of the
apparatus. Boilers may be classified on the basis of any of the following characteristics:
 Use
 Pressure
 Material
 Size
 Tube contents, shape and position
 Firing
 Heat source
 Fuel
 Fluid
 Circulations
 Furnace position
 Furnace type
 General shape
 Trade name
 Special features
Use: The characteristics of the boiler vary according to the nature of service performed.
Customarily boiler is called either stationary or mobile. Large units used primarily for electric
power generation are known as control station steam generator or utility plants.
Pressure: To provide safety control over construction features, all boilers must be
constructed in accordance with the Boiler codes, which differentiates boiler as per their
characteristics.
Materials: Selection of construction materials is controlled by boiler code material
specifications. Power boilers are usually constructed of special steels.
Size: Rating code for boiler standardize the size and ratings of boilers based on heating
surfaces. The same is verified by performance tests.
Tube Contents, shape and position: In addition to ordinary shell type of boiler, there are
two general steel boiler classifications, the fire tube and water tube boilers. Fire tube boiler is
boilers with straight tubes that are surrounded by water and through which the products of
combustion pass. Water tube boilers are those, in which the tubes themselves contain steam
or water, the heat being applied to the outside surface.

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Firing: The boiler may be a fired or unfired pressure vessel. In fired boilers, the heat applied
is a product of fuel combustion. A non-fired boiler has a heat source other than combustion.
Heat Source: The heat may be derived from
(1) the combustion of fuel
(2) the hot gasses of other chemical reactions
(3) the utilization of nuclear energy.
Fuel: Boilers are often designated with respect to the fuel burned.
Fluid: The general concept of a boiler is that of a vessel to generate steam. A few utilities
plants have installed mercury boilers.
Circulation: The majority of boilers operate with natural circulation. Some utilize positive
circulation in which the operative fluid may be forced 'once through' or controlled with
partial circulation.
Furnace Position: The boiler is an external combustion device in which the combustion
takes place outside the region of boiling water. The relative location of the furnace to the
boiler is indicated by the description of the furnace as being internally or externally fired.
Furnace type: The boiler may be described in terms of the furnace type.
General Shape: During the evaluation of the boiler as a heat producer, many new shapes and
designs have appeared and these are widely recognized in the trade.
Trade Name: Many manufacturers coin their own name for each boiler and these names
come into common usage as being descriptive of the boiler.
Special features: some times the type of boiler like differential firing and Tangential firing
are described.
Categorization of Boilers:
Boilers are generally categorized as follows:
• Steel boilers
• Fire Tube type
• Water tube type
• Horizontal Straight tube
The main components of a boiler and their functions are given below:
Drum: It is a type of storage tank much higher placed than the level at which the boiler is
placed, and it is also a place where water and steam are separated. First the drum is filled with
water coming from the economizer, from where it is brought down with the help of down-

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comers, entering the bottom ring headers. From there they enter the riser, which are nothing
but tubes that carries the water (which now is a liquid-vapor mixture), back to the drum.
Now, the steam is sent to the super heaters while the saturated liquid water is again circulated
through the down-comers and then subsequently through the risers till all the water in the
drum turns into steam and passes to the next stage of heating that is superheating.
Super heaters: The steam from the boiler drum is then sent for superheating. This takes
place in three stages. In the first stage, the steam is sent to a simple super heater, known as
the low temperature super heaters (LTSH), after which the second stage consists of several
divisional panels super heaters (DPSH). The final stage involves further heating in the Platen
super heaters (PLSH), after which the steam is sent through the Main Steam (MS) piping for
driving the turbine.
Water walls: The water from the bottom ring header is then transferred to the water walls,
where the first step in the formation of steam occurs by absorbing heat from the hot interior
of the boiler where the coal is burned continuously. This saturated water steam mixture then
enters the boiler drum.
Economizer: The economizer is a tube-shaped structure which contains water from the boiler
feed pump. This water is heated up by the hot flue gases which pass through the economizer
layout, which then enters the drum. The economizer is usually placed below the second pass
of the boiler, below the Low Temperature Super heater. As the flue gases are being
constantly produced due to the combustion of coal, the water in the economizer is being
continuously being heated up, resulting in the formation of steam to a partial extent.
Economizer tubes are supported in such a way that sagging, deflection & expansion will not
occur at any condition of operation.
Deaerator: A deaerator is a device that is widely used for the removal of air and other
dissolved gases from the feedwater to steam-generating boilers. In particular, dissolved
oxygen in boiler feedwaters will cause serious corrosion damage in steam systems by
attaching to the walls of metal piping and other metallic equipment and forming oxides (rust).
Water also combines with any dissolved carbon dioxide to form carbonic acid that causes
further corrosion. Most deaerators are designed to remove oxygen down to levels of 7 ppb by
weight (0.005 cm³/L) or less.
Turbine: A turbine is a turbomachine with at least one moving part called a rotor assembly,
which is a shaft or drum with blades attached. Moving fluid acts on the blades so that they
move and impart rotational energy to the rotor. But in thermal power plant the turbine use as
called steam turbine.
Steam Turbine: A steam turbine is a device which extracts thermal energy from pressurized
steam and uses it to do mechanical work on a rotating output shaft. Its modern manifestation
was invented by Sir Charles Parsons in 1884.

38. 37 | P a g e
Because the turbine generates rotary motion, it is particularly suited to be used to drive an
electrical generator – about 90% of all electricity generation in the United States (1996) is by
use of steam turbines. The steam turbine is a form of heat engine that derives much of its
improvement in thermodynamic efficiency from the use of multiple stages in the expansion
of the steam, which results in a closer approach to the ideal reversible expansion process.
Types of Steam Turbine:
Impulse turbines: An impulse turbine has fixed nozzles that orient the steam flow into high
speed jets. These jets contain significant kinetic energy, which is converted into shaft rotation
by the bucket-like shaped rotor blades, 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 inlet pressure to the exit
pressure (atmospheric pressure, or more usually, the condenser vacuum). Due to this high
ratio of expansion of steam, the steam leaves the nozzle with a very high velocity. The steam
leaving the moving blades has 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.
Operation and maintenance of steam turbine: Because of the high pressures used in the
steam circuits and the materials used, steam turbines and their casings have high thermal
inertia. When warming up a steam turbine for use, the main steam stop valves (after the
boiler) have a bypass line to allow superheated steam to slowly bypass the valve and proceed
to heat up the lines in the system along with the steam turbine. Also, a turning gear is
engaged when there is no steam to slowly rotate the turbine to ensure even heating to prevent
uneven expansion. After first rotating the turbine by the turning gear, allowing time for the
rotor to assume a straight plane (no bowing), then the turning gear is disengaged and steam is
admitted to the turbine, first to the astern blades then to the ahead blades slowly rotating the
turbine at 10–15 RPM (0.17–0.25 Hz) to slowly warm the turbine. The warm up procedure
for large steam turbines may exceed ten hours.
During normal operation, rotor imbalance can lead to vibration, which, because of the high
rotation velocities, could lead to a blade breaking away from the rotor and through the casing.
To reduce this risk, considerable efforts are spent to balance the turbine. Also, turbines are
run with high quality

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steam: either superheated (dry) steam, or saturated steam with a high dryness fraction. This
prevents the rapid impingement and erosion of the blades which occurs when condensed
water is blasted onto the blades (moisture carry over). Also, liquid water entering the blades
may damage the thrust bearings for the turbine shaft. To prevent this, along with controls and
baffles in the boilers to ensure high quality steam, condensate drains are installed in the steam
piping leading to the turbine.
Associated systems in a power plant :
Pa fans: The primary air fans are used to carry the pulverized coal particles from the mills to
the boiler. They are also used to maintain the coal-air temperature. The specifications of the
PA fan used at the plant under investigation are: axial flow, double stage, reaction fan.
Fd fans: The forced draft fans, also known as the secondary air fans are used to provide the
secondary air required for combustion, and to maintain the wind box differential pressure.
Specifications of the FD fans are: axial flow, single stage, impulse fan.
Id fan: ( An induced fan ) The main purpose of an ID fan is to suck the flue gas through all
the above mentioned equipments and to maintain the furnace pressure. ID fans use 1.41% of
plant load for a 500 MW plant.
Air pre-heaters: Air pre-heaters are used to take heat from the flue gases and transfer it to
the incoming air.
They are of two types:
a) Regenerative b) Recuperative
b)
Electrostatic precipitators: They are used to separate the ash particles from the flue gases.
In this the flue gas is allowed into the ESP, where there are several metallic plates placed at a
certain distance from each other. When these gases enter, a very high potential difference is
applied, which causes the gas particles to ionize and stick to the plates, whereas the ash
particles fall down and are collected in a hopper attached to the bottom of the ESP. The flue
gas is allowed to cool down and is then released to the ID fan to be sent to the chimney.
Mill: As the name suggests the coal particles are grinded into finer sized granules. The coal
which is stored in the bunker is sent into the mill, through the conveyor belt which primarily
controls the amount of coal required to be sent to the furnace. It on reaching a rotating bowl
in the bottom encounters three grinding rolls which grinds it into fine powder form of approx.
200 meshes per square inch. the fine coal powder along with the heated air from the FD and
PA fan is carried into the burner as pulverized coal while the trash particles are rejected
through a reject system.
Seal air fan: The seal air fan is used near the mill to prevent the loss of any heat from the
coal which is in a pulverized state and to protect the bearings from coal particle deposition.

40. 39 | P a g e
Wind box: these acts as distributing media for supplying secondary/excess air to the furnace
for combustion. These are generally located on the left and and right sides of the furnace
while facing the chimney.
Igniter fan: Igniter fans which are 2 per boiler are used to supply air for cooling Igniters &
combustion of igniter air fuel mixture.
Chimney: These are tall RCC structures with single & multiple flues. Here, for I & II we
have 1 chimney, for unit III there is 1 chimney & for units IV & V there is 1 chimney. So
number of chimneys is 5 and the height of each is 275 metres.
Coal handling plant: This part of the thermal power plant handles all the requirements of
coal that needs to be supplied to the plant for the continuous generation of electricity. Coal is
generally transported from coal mines ( mostly located in peninsular regions of India ) to
Thermal power plant with the help of rail wagons. A Single rail wagon can handle upto 80
tons of coal( gross weight) . When these rail wagons reach the thermal plant the coal is
unloaded with the help of wagon tipplers. A wagon tippler is actually a huge J shaped Link
pinned at its top. Powerful motors are used to pull the ropes attached to an end which lets the
wagon to rotate at an angle of 135 degree. The coal falls down due to action of gravity into
the coal bunkers. Vibration motors then are used to induce the movement the coal through its
way. as the coal reaches the hopper section of the bunker , it is taken away by conveyer be lts
to either the storage yard or to the assembly points where the coal gets distributed on different
conveyers. Initially, the size of coal is taken as 250mm in size. The macro coal has to be
converted into micro ( 25mm ) size coal for the actual combustion. This is attained by using
high pressure crushers located at the coal handling plants. Here various metal are separated
by various mechanisms. There are various paths through which a coal can go to boiler
section. These paths are alternative such as A and B and only one is used at a time letting the
other standby.
Coal bunker: These are in process storage used for storing crushed coal from the coal
handling system. Generally, these are made up of welded steel plates. Normally, these are
located on top of mills to aid in gravity feeding of coal. There are 10 such bunkers
corresponding to each mill.
Ash handling plant: The ash produced in boiler is transported to ash dump area by means of
sluice type hydraulic ash handling system, which consists of:
Bottom Ash System: In the Bottom Ash system the ash slag discharged from the furnace
bottom is collected in two water impounded scraper troughs installed below bottom ash
hoppers. The ash is continuously, transported by means of the scraper chain conveyor, on to
the respective clinker grinders which reduce the lump sizes to the required fineness.
Fly Ash System: In this system, Fly ash gets collected in these hoppers drop continuously to
flushing apparatus where fly ash gets mixed with flushing water and the resulting slurry drops

41. 40 | P a g e
into the ash sluice channel. Low pressure water is applied through the nozzle directing
tangentially to the section of pipe to create turbulence and proper mixing of ash with water.
Ash Water System: High pressure water required for B.A hopper quenching nozzles, B.A
hopper`s window spraying, clinker grinder sealing scraper bars, cleaning nozzles B.A hopper
seal through flushing, Economizer Hoppers` flushing nozzles and sluicing trench jetting
nozzles is tapped from the high pressure water ring main provided in the plant area.
Ash Slurry System: Bottom Ash and Fly Ash slurry of the system is sluiced up to ash slurry
pump along the channel with the aid oh high pressure water jets located at suitable intervals
along the channel. Slurry pump section line consisting of reduc ing elbow with drain valve,
reducer and butterfly valve and portion of slurry pump delivery line consisting of butterfly
valve, Pipe and fitting has also been provided.
Reheater: The function of reheater is to reheat the steam coming out from the high
pressure turbine to a temperature of 540 degrees Celsius. It is composed of two sections: the
rear pendant section is located above the furnace arc & the front pendant section is located
between the rear water hanger tubes & the Platen superheater section.
Burners: There are total 20 pulverised coal burners for the boiler present here, & 10 of the
burners provided in each side at every elevation named as A,B,C,D,E,F,G,H,J,K. There are
oil burners present in every elevation to fire the fuel oil (LDO & HFO) during lightup.
Ways to increase the thermal efficiency of power plants:
The basic idea behind all the modifications to increase the thermal efficiency of a
power cycle is the same: Increase the average tempe rature at which heat is transferred to the
working fluid in the boiler, or decrease the average temperature at which heat is rejected from
the working fluid in the condenser. That is, the average fluid temperature should be as high as
possible during heat addition and as low as possible during heat rejection.
1) Lowe ring the Condenser Pressure (Lowers Tlow,avg): Steam exists as a saturated
mixture in the condenser at the saturation temperature corresponding to the pressure
inside the condenser. Therefore, lowering the operating pressure of the condenser
automatically lowers the temperature of the steam, and thus the temperature at which
heat is rejected. The effect of lowering the condenser pressure on the Rankine cycle
efficiency is illustrated on a T-s diagram in Fig.1. For comparison purposes, the
turbine inlet state is maintained the same. The colored area on this diagram represents
the increase in net work output as a result of lowering the condenser pressure from P4
to P4‟. The heat input requirements also increase (represented by the area under curve
2_-2), but this increase is very small. Thus the overall effect of lowering the
condenser pressure is an increase in the thermal efficiency of the cycle.

42. 41 | P a g e
Fig 7. Effect of lowering of the condenser pressure on efficiency
2) Superheating the Steam to High Tempe ratures (Increases Thigh,avg): The average
temperature at which heat is transferred to steam can be increased without increasing
the boiler pressure by superheating the steam to high temperatures. The effect of
superheat ing on the performance of vapor power cycles is illustrated on a T-s
diagram in Fig.2. The colored area on this diagram represents the increase in the net
work. The total area under the process curve 3-3_ represents the increase in the heat
input. Thus both the net work and heat input increase as a result of superheating the
steam to a higher temperature. The overall effect is an increase in thermal efficiency,
however, since the average temperature at which heat is added increases.
Fig 8. Effect of superheating the steam to high temperatures

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3) Increasing the Boiler Pressure (Increases Thigh,avg): Another way of increasing the
average temperature during the heat-addition process is to increase the operating
pressure of the boiler, which automatically raises the temperature at which boiling
takes place. This, in turn, raises the average temperature at which heat is transferred to
the steam and thus raises the thermal efficiency of the cycle. The effect of increasing
the boiler pressure on the performance of vapor power cycles is illustrated on a T-s
diagram in Fig.3. Notice that for a fixed turbine inlet temperature, the cycle shifts to
the left and the moisture content of steam at the turbine exit increases. This
undesirable side effect can be corrected, however, by reheating the steam, as
discussed in the next section.
Fig 9. Effect of increasing boiler pressure to increase efficiency
Losses during operation & maintainance of plant:
Surface roughness:
It increases friction & resistance. It can be due to Chemical deposits, Solid particle
damage, Corrosion Pitting & Water erosion. As a thumb rule, surface roughness of about 0.05
mm can lead to a decrease in efficiency of 4%.
Leakage loss:
a) Interstage Leakage
b) Turbine end Gland Leakages
c) About 2 - 7.5 kW is lost per stage if clearances are increased by 0.025 mm depending upon
LP or
HP stage.
Wetness loss:
A) Drag Loss: Due to difference in the velocities of the steam & water particles, water
particles lag behind & can even take different trajectory leading to losses.

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B) Sudden condensation can create shock disturbances & hence losses.
C) About 1% wetness leads to 1% loss in stage efficiency.
Steam turbine:
A steam turbine is a device that extracts thermal energy from pressurized steam and uses it to
do mechanical work on a rotating output shaft. Its modern manifestation was invented by sir
charles parsons in 1884. Because, the turbine generates rotary motion, it is particularly suited
to be used to drive an electrical generator. The steam turbine is a form of heat engine that
derives much of its improvement in thermodynamic efficiency from the use of multiple
stages in the expansion of the steam, which results in a closer approach to the ideal reversible
expansion process. The inlet pressure is 1250 psi. The temperatures of primary and secondary
stages are 570o f and 950o f respectively.
operation:
During the operation the rotor rotates at a
speed of 3000 rpm. Once this speed is
achieved, it is coupled with the generator.
A starting gear, which is a motor, is used to
start rotation of the rotor. The turbine is
cooled using h2 gas and is sealed using
sealing oil from the seal oil unit.
Control room:
The whole generation process is operated and monitored at the control room where all the
temperature and pressure readings are available at designated gauges. Each component also
has a manual control in case any faults occurs in the control room.

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Table Fuel Cost R.s/Kwh
Year
Fuel Cost Generation
Energy Charge Unit Sold
Tariff As Per
R.S/Kwh Cost R.S/Kwh Ppa R.S/Kwh
2009 7.749 8.296 27343977598 3296919496 8.29
2010 9.17 9.742 29196367636 3140772805 9.29
2011 11.12 11.192 36783510000 2981976153 11.18
2012 9.346 10.862 6149080254 3401610000 10.81
2013 7.164 6.225 6149080254 987552070 6.22
2014 8.639 8.986 2413028000 1484748103 9.09
2015 9.656 11.103 9434167676 1684730497 11.19
Energy Generation Source Vies Graph: