CENTRAL POWER GENERATION CO. LTD
GENCOGENCO-II
TRAINING CENTER TPS GUDDU
ADVANCE OPERATOR COURSE
BY
KHALID AYAZ SOOMRO
INSTRUCTOR (INTERN ENGINEERS)
TPS, GUDDU
By:Khalid Ayaz Soomro
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FIRE AND
SAFETY
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FIRE
Fire is the rapid oxidation of a material in the exothermic
chemical process of combustion, releasing heat, light,
light and various
reaction products i.e. toxic gases and smoke.
PRINCIPLE OF FIRE
Fires start when a flammable or a combustible material, in
combination with a sufficient quantity of an oxidizer such as oxygen
gas, is exposed to a source of heat or ambient temperature above
the flash point for the fuel/oxidizer mix, and is able to sustain a rate of
rapid oxidation that produces a chain reaction.. This is commonly
called the fire tetrahedron (three-dimensional case)..
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Fire cannot exist without all of these elements in place and in
the right proportions
1.
2.
3.
Oxygen
Fuel
Heat
When fire take place, below mentioned three objects can be
observed easily.
1.
2.
3.
Hot Gases (emission)
Light
Heat
The emission gases have different properties regarding fuel. The
visibility of flame light depends on the particles which have not been
burned completely. Hence, they become visible.
The different gases contain in atmosphere are listed below.
S/No.
1
2
3
Name of Gas
Nitrogen
Oxygen
Carbon Dioxide
Symbol
N2
O2
CO2
% in air
78%
21%
1%
The flash point of different fuels is listed below.
S/No.
1
2
3
4
Name of Gas
Flash Point
Gasoline (Petrol)
Furnace Oil (RFO)
Natural Gas
Kerosene Oil
-43 OC
>60 OC
>93.3 OC
>37 to 65 OC
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Auto ignition
temperature
280 OC
407 OC
580 OC
229 OC
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Flash Point
The flash point indicates how easy a chemical may ignite and
burn
Auto Ignition Temperature
The Auto-Ignition Temperature - or the minimum temperature
required to ignite a gas or vapor in air without a spark or flame
FUEL
Fuels are any materials that store potential energy in forms that can
be practicably released and used for work or as heat energy.
OR
Those materials that are storing energy in the form of chemical
energy that could be released through combustion.
Types of Fuels
1. Solid
-2. Liquid
-3. Gaseous –
By:Khalid Ayaz Soomro
Wood, Coal, Lignite, Peat etc.
Petroleum, Diesel, Fuel Oils, Alcohols etc.
Natural Gas, Coal Gas, Hydrogen etc.
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Types of Fire
S/No. Fire Class
1
2
3
4
5
6
Symbol
Properties
A
Fires that involve flammable
solids such as wood,
wood cloth,
rubber, paper,, and some types
of plastics
B
Fires that involve flammable
liquids or liquefiable solids such as
petrol/gasoline,, oil, paint, some
waxes & plastics, but not cooking
fats or oils
C
Class C fires are fires involving
energized electrical equipment
such as motors, transformers, and
appliances
D
E
F or K
By:Khalid Ayaz Soomro
Fires that involve combustible
metals, such as sodium,
sodium
magnesium,, and potassium
Fires that involve flammable
gases, such as natural gas,
gas
hydrogen, propane,
propane butane
Fires involving cooking fats & oils.
The high temp. of oils when on
fire far exceeds that of other
flammable liquids making normal
extinguishing agents ineffective.
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Types of Fire and extinguishing
Fuel Source
Class
of Fire
Type of Extinguisher
(Extinguishing Agent)
Ordinary combustibles
(e.g. trash, wood, paper,
cloth)
A
Water; chemical foam
Flammable liquids
(e.g. oils, grease, tar,
gasoline, paints, thinners)
B
Carbon dioxide (CO2); dry
chemical; film forming foam
Electricity
(e.g. live electrical
equipment)
C
CO2; dry chemical
Combustible metals
(e.g. magnesium, titanium)
D
Dry powder (suitable for the
specific combustible metal
involved)
Combustible gases
(e.g. Natural Gas, Butane)
E
A.B.C powder
Combustible Cooking
(e.g. cooking oils; animal
fats, vegetable fats)
F or K
Wet chemical (Potassium
acetate based)
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Portable and semi portable fire extinguishers.
Fire Class
A
A
BCDE
AB
ABCD
ABCE
BE
Extinguisher Type
Soda Acid
Water Type
Carbon Dioxide
Foam Type
Chemical Powder, Dry Type
B.C.F Halon
Carbon Tetrachloride
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HOW TO OPERATE FIRE EXTINGUISHNER
Check either extinguisher is fully charged or not
Ensure you remain a safe distance from the fire and remove the
safety pin
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Where to aim the fire extinguisher hose:
Fires spreading horizontally:
Aim the hose at the base of the fire, moving the
jet across the area of the fire
Fire spreading vertically:
Aim the hose at the base of the fire, slowly
moving the jet upwards following the direction of
the fire
Squeeze the lever slowly to begin discharging the extinguisher, as the fire starts
to diminish carefully move closer to it.
Ensure all the fire has been extinguished; try to focus on any hot spots that may
re-ignite.
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Non-portable Fire Extinguishing Systems
1.
Mulsi Fire System
• Used to extinguishing the fire occurred at electrical transformer
The MulsiFire system applies water in the form of a conical spray
consisting of droplets of water travelling at high velocity. These
droplets bombard oil surface to form a mixture of oil & water. This
mixture significantly cools fire reducing the rate of liquid vaporization,
While water droplets are passing through flame zone, some of the
water is formed into steam that dilutes the air feeding the fire and
creates a smothering effect to extinguish the fire.
2.
Sprinkler System
• Used to extinguishing the fire occurred in cable trenches
A fire sprinkler system is an active fire protection measure, consisting
of water supply system, providing adequate pressure & flow rate to a
water distribution piping system, onto which fire sprinklers are
connected
3.
Auto Carbon Dioxide
Used to extinguishing the fire occurred on Turbine & Generator.
The non-portable fire extinguishing systems are often used at large
power plants.
WHENEVER FIRE OCCURRED
When you find fire, inform the concern.
Restrict the fire by using extinguishing.
Activate the fire alarm.
Leave your self and exit
Enter low into fire zone.
Remove endanger person
Take control
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Fundamentals for extinguishing fire
The below mentioned are basic fundamental rules to extinguishing
fire
1.
2.
3.
Starvation
Smothering
Cooling
Starvation
Removing fuel from fire triangle is called elimination of fire starvation.
Smothering
Removing oxygen from fire triange is called smothering
Cooling
To decrease the temperature of fuel from ignition point is called
cooling
PRECAUTIONARY MEASURES
1.
2.
3.
4.
5.
6.
7.
8.
To store carefully hazardous fuels i.e. petrol, oil, thinner etc.
To stop leakage in oil lube, hydrogen, natural gas lines etc.
To observe the increase in bearing temperature of I.D and F.D
fans.
Always observe the oil leakage where steam and oil lines in
vicinity.
Cotton rags should be kept in safe place.
Whenever oil is used in plant or workshop the excessive quantity
should be returned back to store.
Where smoking is not allowed, make sure that the rule is
followed.
Always make close watch over electric supply cables and
wires.
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DIFFERENT SAFETY SIGNS
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safety
Safety is the state of being “safe”. The condition of being protected
against physical, social, financial, political or other types damages,
harm accidents or any other event which would be considered nondesirable.
Safety can also be defined to be the control of recognized hazards
to achieve an acceptable level of risk. It includes protection of
people of possession.
Regulation of Safety Code
It power plant and other industrial workers should use safety codes
and follow safety precautions during work hrs, so that no harm or
fatal accident does not take place
DUTIES OF WORKERS
All employees should follow safety rules and always try best to avoid
redundant situation regarding his own and other co-workers.
SAFETY CODE
The safety code contains all information and guideline to restrain
from accidents during job and further if any accident take place
then how the aftereffect can be minimized. Thus, safety code is used
to minimize the risk of accident for example: safety tags etc.
SAFETY FUNDAMENTALS
There are two major rules of safety
Good House Keeping
Good Operation
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Good housekeeping
Your work location should be kept clean and orderly. Keep
machines and other objects (merchandise, boxes, shopping carts,
etc.) out of the center of aisles. Clean up spills, drips, and leaks
immediately to avoid slips and falls. Place trash in the proper
receptacles. Stock shelves carefully so merchandise will not fall over
upon contact.
GOOD OPERATION
Good operation means to take necessary measures to safe
operation of all appliances at industry i.e. If you have to work on
breaker then it should be isolated, check its isolation and connect a
earth lead. The worker should take serious efforts on the following.
1.
Missing Warning Sign.
Without warning sign any work on equipment can be very
dangerous and severe damage to life and equipment can take
place.
2.
Improper Guarding
During work all safety gears should be wear i.e. gloves, safety shoes,
safety goggles etc.
3.
Defective Material
Before starting work proper tools and safety gears should be used to
avoid any accident. It should be ensured that tools are made in
accordance with international laws and they have not been broken
nor have bad workmanship quality.
Causes of accidents
1.
Hazards
Everything which came under hazards is dangerous. i.e. oil leakage,
cotton rags, and bad sanitation.
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2.
Insufficient lighting
At work place insufficient lighting is can be a part during accident.
Thus, sufficient lighting at work place should be ensured.
3.
Air Ventilation
At work place harmful gases should not be gathered i.e. acid vapors
and dust. Thus, proper ventilation of air should be ensured.
4.
Loose Cloths
Loose cloths should not be wearing at work place.
SAFETY GEARS
Safety gears are used as prime substance to ensure safety to worker.
Thus, before working on electrical system this should be checked
and ensure according to rules and regulation of department.
Kinds of safety gears
1.
Safety Helmet
It protect worker from head and eye injury, further it protects from
heat stroke and dust. Thus, this should be wear during work hrs.
Safety equipment
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2.
Ear Muffs
This protect human ear from excessive noise a work place which can
damage hearing efficiency. Normal noise level is 85~90db. Thus if the
noise exceed from above the ear muffs should be used.
3.
Safety shoes.
At industrial area the safety shoes are used to restrain hazards at
wet, oils places or any place where foot injury is one of most prime
cause. These shoes can be used at chemical plant, However they
are called long rubber shoes. They also insulate human body from
electrical shock.
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4.
Protective Cloth
Use appropriate protective cloth during decanting of furnace oil,
acid tankers and batteries.
5.
Respirator mask
This should be wear, where industrial exhaust i.e. stacks or where any
other dangerous gases contacting human body. If respirators are
not used that this will bring deceases like i.e. chest infection and
allergies during respiration.
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6.
Safety glasses
The wearing of safety glasses by all shop employees and work on
sand blasting etc. Strict adherence to this policy can significantly
reduce the risk of eye injuries.
7.
Safety gloves.
Through this apparatus worker can be safe during work on acid,
handing furnace oil, steam and hot valves or electrical contacts.
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8.
Safety belts.
This safes the worker from fall down from height. Thus during work on
electrical pole or any place alike that, safety belt must be used.
Safety shoes
9.
Welder protective shield.
During welder a vital sparking light may cause an injury to eye. Thus,
to restrain such type of injury protection shield must be wear before
welding.
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Safety programs
The below are prime objects to conduct safety programs.
1.
To point out unsafe practice, so that employees and
appliances are prevented from accident.
2.
To empower the administrative to follow ensure the regulation
of safety code.
3.
To abide the SOP for safety code.
4.
To prepare a comprehensive accident reports this contains
causes of accident and prevention, so that other may follow to
restrain such accidents.
5.
Work plan may be made in accordance with safety rules.
6.
To conduct safety seminars in-between other power plants, so
that awareness to new technology may be discussed and this
will bring knowledge for safe operations.
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INTRODUCTION
TO
POWER
PLANTS
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Basic concept of modern power plants
The modern power complex consists on Steam and Gas Turbine has
three major concepts.
S/No. Name and History
1
Willian Rankine’s (1845~1865)
Thermodynamics
2
George Brayton (1872)
Thermodynamics
3
Michael Faraday (1831)
discovery of induction in 1831
Concept
Where heat is added in water
boiler
ler to convert heat into
work
Where heat is added and
discharged at constant
pressure
When a permanent magnet is
moved relative to a
conductor, or vice versa, an
electromotive force is
created. If the wire is
connected through
throug an
electrical load,
load current will
flow, and thus electrical
energy is generated
Faraday's iron ring apparatus. Change in the magnetic flux of the left
coil induces a current in the right coil.
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Entropy of Rankine Cycle
Where heat is added in water boiler to convert heat into work
Entropy of Braytone Cycle
Where heat is added and discharged at constant pressure
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POWER PLANTS
A power station (also referred to as a generating station, power
plant, powerhouse or generating plant) is an industrial facility for the
generation of electric power.
Each power station contains one or more generators, a rotating
machine that converts mechanical power into electrical power by
creating relative motion between a magnetic field and a conductor
HISTORY OF POWER PLANT
The world's first power station was designed and built by Lord
Armstrong at Cragside, England in 1868. Water from one of the lakes
was used to power Siemens dynamos
The first public power station was the Edison Electric Light Station,
built in London, which started operation in January 1882. This was a
project of Thomas Edison, it was called JUMBO.
Types of Power Plants
1.
Conventional Power Plants.
Those power plants, which can be installed at any where easily
i.e. Thermal Power Plants.
2.
Non-conventional Power Plants.
Those Power Plants, which cannot be installed at any where
easily i.e. Wind Electric Power.
Those power plants, which produce electricity by converting
chemical into electric energy called thermal power plant.
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Different categories of power plants
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WIND POWER PLANT
Energy Cycle
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BLOCK DIAGRAM OF STEAM POWER PLANT
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BASIC PARTS OF THERMAL POWER PLANT
1.
2.
3.
BOILER
TURBINE
GENERATOR
A boiler or steam generator is a device used to create steam by
applying heat energy to water. Thus, when heat is applied it
produces steam and pressure in close vessel.
Types of Boiler
1. Water tube boiler
2. Fire tube boiler
Water Tube Boiler
In water tube boiler, boiler feed water flows through the tubes and
enters the boiler drum. The circulated water is heated by the
combustion gases and converted into steam at the vapor space in
the drum. These boilers are selected when the steam demand as
well as steam pressure requirements are high.
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Fire Tube Boiler
In fire tube boiler, hot gases pass through the tubes and boiler feed
water in the shell side is converted into steam. Fire tube boilers are
generally used for relatively small steam capacities and low to
medium steam pressures.
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BOILER ZONES
A water tube boiler has three zones
Radiation zone:
Heat transfer takes place by radiation from the yellow flames. This
zone is located in the bottom and middle portion of the furnace
(1200~1400 0C). It consists of combustion chamber, water wall and
radiant super heaters.
Radiant convection heating zone:
The effect of radiation is reduced in the top portion of Zone-1 where
secondary air is introduced. Here het transfer takes place both by
radiation and convection. Temp (800~1200 0C). It consists of platen
super heaters and water wall.
Convective heating zone (i) and (ii)
It may call high temperature convective heating zone. Heat transfer
predominately is convection. It is located after radiant convective
heating part with temperature (800~900 0C. It consists of convection
super heaters, re-heaters and economizer. Convective zone (ii) has
temp lower than 800 0C. APH (Air preheater) is located in this zone.
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1. Burner
2. Radiant SH
4. Convective SH 5. Re-heater
7. Air preheater
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8. Water wall
3. Planten SH
A. Radiant Zone
6. Economizer
B. Radiant Zone
C. Convection zone
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1. Boiler Drum
6. Radiant S.H
11. Air Pre Heater
16. Chimney
2. Furnace
7. Platen S.H
12. Air Duct
17. Soot Blower
3. Burner
8. Convective S.H
13. F.D Fan
18. Generation Tubes
4. Down Comer
9. Reheaters
14. Calorifire
19. GRC fan
5. Lower Drum
10. Economizer
15. I.D Fan
PARTS OF BOILER
01
Boiler Drum
02
Boiler Furnace
03
Super Heaters
04
Re-heaters
05
Boiler water tubes
06
Water economizer
07
Gas recirculation fan
08
Air pre heater
09
Calorifier
10
I.D. Fan
11
F.D Fan
12
Chimney
13
Soot Blower / Shot Blasting
14
Boiler safety valves
15
Down comers
16
Lower header / Drum
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BOILER DRUM
Boiler drum earn feed water from economizer. This water goes
through the drum to down comers and thereafter it enters into up
riser tubes. The up riser tubes generate saturated steam which came
back into boiler drum and thereafter the steam goes to different
super heaters.
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BOILER DRUM INTERNAL DIAGRAM
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Duties of Boiler Drum
01
Receives feed water
02
Store feed water
03
Distributes the water
04
Contains pressure
05
Receive steam water mixture
06
Provides outlet to saturated steam
07
It performs the process of separation and steam purification
at higher pressure with the aid of baffles and other devices.
08
Produce blow down C.B.D and E.B.D
DRUM INTERNALS
Baffle plates
Baffle plates in the steam drum reduce turbulence, improving steam
purity and reducing steam in the circulating boiler water
OR
It converts feed water into small particles and when it passes through
feed water it separate rust & unsolvable gases which may remove
through boiler vent.
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Steam Separator
It removes heavy pollution from steam. Chemical dozing is also used
to remove pollutions.
Steam Washer
This is a mechanical arrangement which washes the steam.
Steam purifier
This eliminates remaining pollution and moisture and purify the
steam. Further passes the steam from drum to super heaters.
Steam Scrubber
This filters steam.
Cyclone
The function of cyclone is to eliminate silica and hardness.
Discharge lines
Discharge lines are used to discharge steam from boiler drum
C.B.D (Continuous blow down)
To control silica value in drum normally 5~7 T/h and 18 T/h
E.B.D (Emergency blow down)
To meet the emergency for controlling silica value in drum
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BOILER FURNACE
The furnace is the place where burning process with a mixture of fuel
and air takes place. This provides space during burning. This also
prevents the heat loss during fire because this is a sealed
compartment. Furnace disburses heat to up riser tubes which
converts water into steam. This also prevents to enter cold air into
furnace.
The furnace design should be like that which prevent heat losses.
Flue Gases
During burning of fuel some gases are expelled which are called flue
gases.
Burners
Burner is a device, which helps to ignite fuel with the help of air. This
device is used for proper firing. Burner is a prime source to set right
the fuel and air mixture, pressure and firing location. Burner is also
called boiler operating parameter due to its importance for
calculating boiler efficiency.
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Properties of Burner.
1. With the help of burner fuel burns completely.
2. Easy to operate
3. Maintain fire arc’s direction, so that at heat utilized within
furnace.
4. It make proper mixture of air and fuel
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Super Heaters
It is boiler auxiliary designed to superheat the saturated steam to a
specified temperature. It may reach upto 540 0C.
Duties of Super Heater
1.
2.
3.
It increases the temp. of saturated steam.
It is used to dry the steam
It provides an outlet to superheated steam towards the steam
turbine.
Super heater is consisting of a bundle of tubes therein saturated
steam passes. This wet steam gets more heat to convert as super
heated steam. Super heaters are installed in all three zones of boiler.
1. Radiant Super heater
2. Platen Super heater
3. Convective Super heater
The temperature of superheated steam is around 400 to 595 0C.
Usually it is around 540 0C. The allowable difference is around ±5 to
10 0C
1.
2.
3.
4.
Advantage of super heated steam
Improve turbine efficiency
No harm can occurred to turbine blade due to wet steam
No rust will occur to turbine blade
Blades does not bend
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Steam temperature control in boiler
1. De-super heater
a. Atompration
b. F.W injection
2. Gas recirculation fan
3. Fuel increased / decreased
4. Air flow control
5. Tilting of burner position
6. Soot blowing
7. Shot blasting
ReRe-heaters
Re-heater can also be termed as super heater. They can also be
called as intermediate super heaters. These are installed in flue gas
duct. The get heat through flue gases and rises wet steam
temperature. There is no temperature different in re-heater or super
heater. However due no decrease in steam pressure it is called reheater. The pressure decreases due to line resistance.
Duties of re-heaters
1. Re-heaters increase the temperature of cold reheat steam
2. They prevent the condensation of steam in I.P turbine.
3. Re-heater is a safety device of I.P turbine.
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Boiler Water Tubes
Down comers
Tubes that come downward from boiler are called down comers.
These are located in unheated zone. They contain feed water.
Further due to less temperature of feed water it become heavy
comparison to steam, thus natural circulation of water occurs. The
feed water enters in boiler drum lower header. This is also called
thermal circulation of feed water.
Up riser
Tubes that come from downward to boiler drum called up risers. In
these tubes water coverts into saturated steam that why they are
also called as generation tubes. These tubes are located inside the
furnace and came into radiation zone, that’s why they get
maximum heat. These are also called water wall and also used as
insulation of boiler.
Boiler Water Circulation Types:
1. Natural or thermal circulation
•
No pump or any device used
2. Control or forced circulation
•
(FCP) Forced circulation pump is used for circulation
3. Once through circulation
•
Boiler drum is not present in the circuit (no storage
capacity)
4. Combined circulation
•
It is combination of forced and natural circulation
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Economizer
Economizer is an accessory of boiler that recovers the waste heat
from the flue gas blown out of the boiler. Thus it actually
"economizes" the operational cost or in other words, improves the
efficiency of fuel utilization in the boiler
Economizer is installed in flue gas duct. The economizer tubes get
heat from flue gases to raise the temperature of feed water. This
device is also reducing the temperature of flue gases.
Economizers dramatically reduce boiler fuel consumption by
efficiently removing waste heat from the flue gas and returning the
heat to the feed water system
Duties of economizer
It increase the temperature of feed water
1.
2.
Receives heat from flue gases
3.
Lower the temperature of flue gases
4.
Reduces the size of boiler
5.
Increase the efficiency of boiler upto 1% in terms of fuel
consumption
6.
It is water heat recovery device.
The temperature of water which is going to enter in economizer
should be higher than freezing point of water because it will start
condensing the flue gases this situation can also be termed as swat
of economizer tubes. The flue gases with a content of sulpher
become condense and form sulphuric acid which is harmful for
economizer tubes. Thus, the minimum temperature of feed water in
economizer is set upto 60 0C
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Gas Recirculation Fan
Gas recirculation (GRC) is a highly effective technique used for
lowering Nitrogen Oxide (NOx) emissions from burners. In industrial
boilers by reticulating used flue gases back into the system. This
process lowers the peak combustion temperature and drops the
percentage of oxygen in the combustion air/flue gas mixture,
delaying the formation of NOx caused by high flame temperatures
This fan is installed in the 2nd zone of boiler, however sent the flue
gases to 1st zone from this cold reheat steam converts into hot reheat
steam and further increased the temperature upto 540 0C. This
steam is used in IP turbine. The GRC fan is only used whenever reheat
temperature did not arise.
Duties of GRC Fan:
•
Delay they action of burning fuel and burn sufficiently
•
Help re-heaters in raising the temperature of cold re-heat
steam
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Air pre-heater
Heating combustion air can raise boiler efficiency about 1% for every
40F in temperature increase. The most common way to preheat the
air is with a heat exchanger on the flue exhaust.
Air pre-heater is installed into flue gases duct. The heating element
get heat from flue gases and passes it to the air going into furnace,
so that temperature of combustion air increased. This helps for
proper fuel burning.
Kinds of air pre-heaters
1.
Regenerative
2.
Recuperative
(i)
Tubular
(ii) Plate type
Advantages of air pre-heating
1.
Improved combustion and efficiency use of fuel
Stabilized fuel ignition which improves low load
2.
combustion
3.
Increased steam generation capacity
4.
Better utilization of low grade, high ash fuel
5.
Minimized size of boiler
6.
Higher thermal efficiency as most of the heat from
combustion products in recovered. If flue gases temp. is
decreased upto 100 0F, the efficiency will increase by 25%
(particularly in the boilers where gas, oil or coal is used as
fuel)
7.
Greater load flexibility
8.
Greater pre-heat, lower the SO3 in the flue gas and
therefore the stack outlet temperature can be lowered
resulting in greater heat utilization.
9.
Air preheating ensures complete burning of fuel resulting
in less slugging and cleaner flue gas and this reduces
boiler outage for cleaning
By:Khalid Ayaz Soomro
Page : 47 of 105
By:Khalid Ayaz Soomro
Page : 48 of 105
Calorifier
This is also called steam air heater. When the machine is operating of
fewer load, this device is used to increase the temperature of flue
gases to ensure not getting dew point in air pre heater and as well in
stack.
It is a tubular heat exchanger in which low temperature steam flows
in the tubes while air flows in the shell side in cross current flow.
Normally the temperature of heating steam is about 120~130 0C. This
steam is the worked off steam from the steam turbine. SAH or
calorifier is introduced at downstream of F.D Fan.
Duties of calorifier
1.
It works as heat exchanger, worked off steam from the turbine
bleed and transfer it heat to combustion air, so it helps in better
combustion.
2.
It prevents air pre heaters from reaching the stage of dew
point.
3.
Indirectly, it regulates the temperature of flue gases flowing
towards the chimney.
By:Khalid Ayaz Soomro
Page : 49 of 105
Induced Draught Fan
The main aspect of ID fan is to exhaust of flue gas, which were
generated in the furnace during firing. The exhaust gases are also
called as under:
1.
2.
3.
4.
5.
6.
Flue gases
Exhaust gases
Exist gases
Chimney gases
Stack gases
Hot gases
Duties of ID Fan
1.
2.
3.
•
It suck flue gases from furnace
It provides zero pressure in the furnace. (it slightly operates on
negative pressure)
The temperature of flue gases when exit from chimney should
not less than 150 0C
ID fan efficiency should be above 20% from FD fan, as leakage
air is also sucked.
Forced Draught Fan
This fan intake air from turbine hall or boiler side and sent it through
air pre heater in the burners. This creates a positive draught in
furnace.
Duty of F.D Fan
1.
2.
Continue air supply for combustion
Push the flue gases toward chimney
The size of F.D fan is smaller since the temperature (specific volume)
of air handled by F.D fan is low than that of the flue gases handled
by the I.D fan. The size of I.D fan is 1:3 times of he size of the F.D fan.
By:Khalid Ayaz Soomro
Page : 50 of 105
Schematic of ID and FD Fans
By:Khalid Ayaz Soomro
Page : 51 of 105
Chimney / Stack
The first industrial chimneys were built in the mid-17th
mid 17th century when it
was first understood how they could improve the combustion of a
furnace by increasing the draught of air into the combustion zone
The chimney has a vital impact on creation of natural
draught.. This is used to exhaust of flue gases. The increase
in height prevents pollution.
Chimney are made of steel or masonry or concrete,
common bricks or perforated bricks. Generally they are
made of several sections. For short exhaust stack, steel
chimneys are preferred. Steel chimneys are particularly
favored in the case of GTPS because a gas turbine attains
its full load in lesss than a minute and as such a chimney
has to with stand a thermal shock resulting from the
increase in temperature of 450~500 0C during this period.
Where several boilers working on partial load are
connected to a common chimney. The phenomena of cold
air inversion takes place; when the flue gas pressure inside
the chimney is less than the air pressure outside the
chimney
By:Khalid Ayaz Soomro
Page : 52 of 105
Soot blower
Flue gas contains numerous compounds. When combustion occurs
some of these compounds will collect and build up on surfaces
within the furnace. The buildup will start to affect the overall
performance of the boiler by obstructing the heat transfer. To
address this problem, soot blowers are installed inside the furnace.
To generate steam several boiler use fuel as coal, gas, oil etc. When
firing occurs due to higher viscosity value of fuel comparison to air
some un-burnt particles remains and further deposit on the boiler
tubes is called soot.
The soot restrains heat transfer and to tackle this soot blowers are
installed, so that flue gases transfer maximum heat to superheater,
economizer and re-heaters etc. Further to improve the heat transfer
either steam or feed water tubes.
By:Khalid Ayaz Soomro
Page : 53 of 105
Boiler Safety Valves
The boiler drums are manufactured on a specific pressure. Thus, in
case the pressure exceed beyond the capability of boiler drum can
explode and due to explosion, chaotic situation can occur in shape
of fatal accident to human or machinery. Thus, to prevent from this
state boiler safety valves are installed which operates on specific
pressure. So whenever pressure exceed from limit these valve get
operated automatically.
•
Regulation for safety valve
1. On every small boiler one safety valve with minimum size of ½”
should be installed. Further if the surface area is exceeding from
500 ft2 then at least two safety valves should be installed.
2. 1st valve should operate at 6% of boiler drum maximum pressure
and thereafter 2nd valve should operate on 3% after working
pressure of 1st safety valve. Safety valves should be installed
without any extension pipe on the boiler drum.
Usually on modern boilers three safety valves are installed. Two
valves on boiler drum and one valve on life steam line are
commonly installed. Both boiler drum valve does not operate on
same pressure.
By:Khalid Ayaz Soomro
Page : 54 of 105
Schematic of boiler safety vlave
By:Khalid Ayaz Soomro
Page : 55 of 105
Boiler Surface
1.
Water surface
Waer surface include the following parts of boiler
1.
2.
3.
4.
2.
Economizer
Boiler drum
Down comers
Generation tubes
100%
partially
100%
partially
Boiler heating surface
Heating surface is the surface area of boiler tubes exposed to
the hot gases of combustion in the furnace space ir order to
transfer heat to the working fluid (FW) to generate steam.
Heating surface include super heaters, re-heaters, de-super
heater and furnace.
•
(i)
(ii)
(iii)
3.
Thereare three tyoes of heating surfaces in a boiler
Radiant heating surface
Radiant convective heating surface
Convective heating surface
Heat transfer surface
All the compnents of boiler, except down comers, includign
furnace, super heater, re-heaters, de-super heaters are heat
transfer surfaces
•
(i)
(ii)
Advtanges of long flue gases path
Heat stays in the flue gases path for maximum possible
time.
Different compenets placed in the flue gases path
absorb heat from the flue gases.
By:Khalid Ayaz Soomro
Page : 56 of 105
•
1.
2.
3.
4.
5.
6.
Ratio of heat absorbed by different compenents placed in
the foue gases path
Water wall
Super heater
Air preheater
Economizer
Re-heater
Chimney
By:Khalid Ayaz Soomro
48%
15%
10%
07%
08%
12%
Page : 57 of 105
Boiler Draught
The pressure difference between furnace and atomospheric air is
called draught. There are two kinds of draughts.
Natural draught
When the draught is generated with the help of the chimney only, it
is called natural draught.
OR
When air or flue gases flow due to the difference in density of the hot
flue gases and cooler ambient gases. The difference in density
creates a pressure differential that moves the hotter flue gases into
the cooler surroundings.
Balanced draught: When the static pressure is equal to the
atmospheric pressure, the system is referred to as balanced draught.
Draught is said to be zero in this system
Artificial Draught
The draught produced by mechanical means like fans and blowers
is called artificial draught. Artificial draught is required because
natural draught will not be sufficient to generate enough static
draught (25 to 350mm of water column) as is quired by large steam
generation plants. Moreover natural draught depends upon climate
conditions.
Forced draught: When air or flue gases are maintained above
atmospheric pressure. Normally it is done with the help of a forced
draught fan.
Induced draught: When air or flue gases flow under the effect of a
gradually decreasing pressure below atmospheric pressure. In this
case, the system is said to operate under induced draught. The
stacks (or chimneys) provide sufficient natural draught to meet the
By:Khalid Ayaz Soomro
Page : 58 of 105
low draught loss needs. In order to meet higher pressure differentials,
the stacks must simultaneously operate with draught fans.
Types of artificial draughts
draught
Positive:
When furnace pressure is greater than atmospheric
pressure. It also called forced draught. Only F.D is used in
it.
Negative: When furnace pressure is less than atmospheric pressure. It
is also called induct draught.. Only ID is used in it
Balance: With both F.D and I.D fan whne used simultaneously
By:Khalid Ayaz Soomro
Page : 59 of 105
How does balanced draught fuction ?
The F.D fan will supply the combustion air for proper and complete
combustion fuel and will overcome the fuel bed resistance I the
case of stoker grate.
The I.D fan will remove the flue gases in addition eliminate excess air
from the furnace , maintaining the pressure inside the furnace just
below the atmospheric pressure (slightly negative)
Boiler protections
•
HP Drum level low
•
HP Drum Level High
•
Fuel Pressure Low
•
Fuel Pressure High
•
Furnace pressure low
•
Furnace pressure high
•
Both f.D fans tripped
•
Both I.D fans tripped
•
All feed pumps tripped
•
Loss of flame
•
Control supply failed
By:Khalid Ayaz Soomro
Page : 60 of 105
Boiler safety interlock
Pre-purge inter lock
Prevents fuel form being admitted to
a furnace until the furnace has been
thoroughly air purged to remove
residual combustibles
High steam pressure interlock
Fuel is shut off upon abnormally
higher boiler steam pressure
Low air flow interlock
Fuel is shut off upon loss of air flow
from the combustion air fan or
blower, the I.D and F.D fan
Low fuel supply inerlock
Fuel is shut off upon loss of fuel supply
pressure would resulting unstable
flame condition
Loss of flame interlock
All fuels is shut off upon loss of flame
in the furance or individual burner
Fan inerlock
Stop FD from upon loss of ID fan
Low water interlock
Shutoff fuel on low water level boiler
drum
High combustibles interlock
Shut off fuel on highly combustible
content in the flue gases
Post purge interlock
Continues fan operation to remove
residual combustion from the furnace
prior to shutting down the fan
By:Khalid Ayaz Soomro
Page : 61 of 105
Combined
Cycle
Power
Plant
By:Khalid Ayaz Soomro
Page : 62 of 105
Combined Cycle Power Plant
Combining two or more thermodynamic cycles results in improved
overall efficiency, reducing fuel costs. Overall effiency of combine
cycle is around 52~65%, whereas gas turbine effiency is around
32~36%.
In stationary power plants, a widely used combination is a gas
turbine (operating by the Brayton cycle) burning natural gas or
synthesis gas from coal, whose hot exhaust powers a steam power
plant (operating by the Rankine cycle). This is called a Combined
Cycle Gas Turbine (CCGT) plant.
Types of CCPP
•
Unfired CCPP
•
Additional fired CCPP
HRSG
It is also called waste heat boiler (or) waste heat recovery steam
generator
The temperature of exhaust flue gases from gas turbine is 540 0C. This
has HHV higher heating value and thereafore these gases are used
in HRSG instead of ruined in atomopsheric air.
Arrangement of HRSG
1st of all super heater has been installed in HRSG to attain maximum
heat and to convert saturated steam into superheated steam,
thereafter evporator tubes are installed therein feed water converts
into saturated steam and in final stage economizer has been placed
therein feed water temp increased upto 250~270 0C.
By:Khalid Ayaz Soomro
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After transfering heat to feed water these gases are throngn into
atmospheric air which has 160~170 0C temperature.
The HRSG generated superheated steam with temp. 500~540 0C and
this steam is used to operate steam turbine.
Working principal of HRSG
1.
2.
3.
4.
To provide sufficent steam to turbine.
To supply steam and hot water on commercial basis to offices.
To supply seam to sugar, cloth, wood mils
To clean the sea water into drinking water / desolination plant
Parts of HRSG
1.
2.
3.
4.
5.
6.
7.
8.
9.
Feed water gate and regulator valve
Economizer
H.P Drum
Evaporator re-circulation pump
Evaporator
Super heater
By-pass damper
Isolation Damper
Weather damper / stack damper
Protection of HRSG
1.
2.
3.
4.
5.
6.
7.
8.
9.
Drum level low low
Drum level high high
Live steam temperature > 540 0C
Evaporator circulation pump tripped.
G.T Tripped
HP Bypass station tripped
G.T flue gases pressure high (50mbar alarm…. 70 mbar trip)
Vacuum low
Pressure rising OR dropping at the rate >4 bar min (ramp rate)
By:Khalid Ayaz Soomro
Page : 64 of 105
By:Khalid Ayaz Soomro
Page : 65 of 105
Gas Turbine
Turbine is a prime mover. It transforms one kind of energy into the
other kind. It is a device used for transformation of energy and
resultantly mechanical or kinetic energy is received.
Gas Turbine
Gas Turbine is the machine which converts hot gases kinetic energy
into mechanical energy or gas turbine is the device which operates
on hot gases energy. Gas Turbines are made with the special
material that can endure high heat.
Parts of Gas Turbine
1.
2.
3.
4.
Filter House
Axial Flow Compressor
Combustion Chamber
Gas Turbine
Filter House
It consists of 1200 approx. air inlet filter which cleans atmospheric air
for compressor. These filters are cartridge type and their use full life is
around 2 years further due to these air inlet filer hard particulars
cannot penetrate into compressor.
Axial Flow Compressor
This compressor intake air through air inlet filters and sent into
combustion chamber. The air is pases through different stages and
attains pressure & temperature. On every stage the temp and
pressure arises with a certain ratio. Compressor has 16 stages and its
comparison ratio is 1-10 bar. Thus if the inlet pressure is 1 bar then
compressor outlet pressure will be 10bar and temperature arises upto
355 0C. This mean at every stage temperature raises upto 22 0C and
in final this compressed and temperature air enter into combustion
chamber
By:Khalid Ayaz Soomro
Page : 66 of 105
Combustion Chamber
Combustion chamber is that part of turbine where energy converts
from chemical energy to heat energy. Some gas turbines have 14
combustors and hot gases are passes through each combustor and
enter into turbine. Some gas turbines have 02 combustion chambers
and contain 8 burners.
Gas turbine
Gas Turbines are operated on hot gases pressure. These hot gases
have been attained from combustion chamber. The temperature of
these gases on turbine inlet is 1060 0C. However on the outlet their
temperature decreases upto 540 0C. Gas Turbine is the main part
which converts heat energy into mechanical energy, so that
electrical output can be received.
Heat + Mech + Elect = Gas Turbine
B.O.P of Gas Turbine
1.
2.
3.
4.
Fuel gas system
Lube oil system
Fuel oil system
Cooling water system
Advantages of gas turbine
1.
2.
3.
4.
5.
6.
7.
8.
9.
Neat to load center
As synchronous condenser
Peak hours loading
Black start provision
Less auxiliaries
Less are required due to being compact
Short starting time
Easy for operation
Power supply in emergency
By:Khalid Ayaz Soomro
Page : 67 of 105
Gas Turbine protections
1.
2.
3.
4.
5.
6.
7.
8.
9.
Exhaust temperature high
Thrust bearing temperature high
High vibration
Loss of flame
Lube oil pressure low / high
Fuel pressure low / high
Lube oil temperature high
Over speed
Compressor surging
By:Khalid Ayaz Soomro
Page : 68 of 105
By:Khalid Ayaz Soomro
Page : 69 of 105
Steam Turbine
Steam turbine is a prime mover that drives its energy of rotation due
to conversion of heat energy of steam into kinetic energy as it
expands through a series of nozzles mounted on the casing or
produced by the fixed blades.
That machine converts heat energy into mechanical energy called
steam turbine.
Chemical energy + heat energy + mechanical energy + electric
energy = steam turbine
Casing / cylinder
The casing contains rotor, blades, seals and bearings. All articles of
turbine contained in casing. This prevents to enter air and other
things this casing also balance the heat. This is also called stationary
part of turbine.
Turbine Rotor
This is rotational parts of turbine. Moving blades are installed in rotor
and their fuction is to rotate turbine rotor, so that generator rotor
may also accompany during rotation.
Shaft
Turbine blades are affixed on shaft. If HP, IP, LP rotors are coupled it is
called shaft.
Seals
Turbine seals are used where leakage of air or steam can occur. Due
to turbine improper sealing vacuum can be loss because LP has
works under negative pressure and that why air tries to enter in LP
turbine.
By:Khalid Ayaz Soomro
Page : 70 of 105
Requirement of Sealing
The sealing is applied when steam or air tries to enter or escape from
turbine casing this has a major impact on overall turbine efficiency
for that reason different types of seals and glands are used
Types of sealing
1.
2.
3.
4.
Stuffing boxes
Carbon ring packing
Labyrinth seal
Water glands
By:Khalid Ayaz Soomro
Page : 71 of 105
Turbine blades
There are two kinds of turbine blades
1.
2.
Stationary or fixed blades
Rotating or moving blades
Stationary or fixed blades
These are also called diaphragm blades and their prime function is
to divert the steam toward moving blades. Steam pressure is much
higher on fixed blades as compare to moving blades. Hence they
divert high pressure steam to moving blades.
Rotating or moving blades
These are installed on the rotor surface and high pressure steam hits
them and movement starts. This rotates the turbine on constant
speed.
Turbine blades have two kinds in respect to their design
1. Reaction type
2. Impulse type
Reaction Type Turbine
Pressure continuous drop and volume increased in stator blades and
in moving blades pressure remains constant and volume becomes
decreased
Impulse Turbine
Pressure drop & velocity increases in curtus wheel stage after this
pressure works in constant position (some lose) and velocity
decreased in every moving blade. In gas turbine 75% energy and
pressure used on 1st stage and the remaining i.e. 25 used on 2nd
stages.
By:Khalid Ayaz Soomro
Page : 72 of 105
By:Khalid Ayaz Soomro
Page : 73 of 105
Steam Valves
Main Steam Valve
Usually main steam valve found in 100% opened or closed position
from this valve steam enters into turbine. This is a huge hand wheel
valve and the steam line contains bypass valves.
Quick Closing Valve
These are also called emergency stop valve. Their prime function is
to protect the turbine in the event of emergency initiated through
protection system. These valves are also called protection operated
valves. These valves operate on hydraulic system.
Governing or regulating valves
Usually these are called governor and their prime function is to
maintain turbine rated speed. To maintain the speed of turbine i.e.
3000 rpm these valve operate automatically. As we know that when
the load increased on generator the turbine speed decreased and
this valve increase it opening to maintain the speed and when he
load decreased on generator the turbine speed increased and this
valve decrease it by closing to maintain the speed.
Thus, this valve maintain the turbine speed in all condition either
under rpm or over rpm.
In power plant generator / turbines are rotated on constant speed,
so that frequency may not get disturbed. In Pakistan the idle
frequency is 50 hz and the formula is as under:
F= p x n / 120
Frequency = no. of poles x speed / phase angle
Thus, if the rotor speed decreased or increased the frequency will be
changed simultaneously.
By:Khalid Ayaz Soomro
Page : 74 of 105
Types of governor valves
Fly weight governor, hydraulic governor, and electrical governor
Different types of valves
•
Ball valve,
for on/off control without pressure drop, and
ideal for quick shut-off, since a 90° turn offers
complete shut-off angle, compared to
multiple turns required on most manual valves.
•
Butterfly valve,
for flow regulation in large pipe diameters.
•
Ceramic Disc valve,
used mainly in high duty cycle applications or
on abrasive fluids. Ceramic disc can also
provide Class IV seat leakage
•
Check vlv or non-return vlv,
allows the fluid to pass in one direction only.
•
Choke valve,
a valve that raises or lowers a solid cylinder
which is placed around or inside another
cylinder which has holes or slots. Used for high
pressure drops found in oil and gas wellheads.
•
Diaphragm valve,
which controls flow by a movement of a
diaphragm. Upstream pressure, downstream
pressure, or an external source (e.g.,
pneumatic, hydraulic, etc.) can be used to
change the position of the diaphragm.
•
Gate valve,
mainly for on/off control, with low pressure
drop.
•
Globe valve,
good for regulating flow.
•
Knife valve,
similar to a gate valve, but usually more
compact. Often used for slurries or powders
on/off control.
•
Needle valve
for accurate flow control.
•
Pinch valve,
for slurry flow regulation and control.
By:Khalid Ayaz Soomro
Page : 75 of 105
•
Piston valve,
for regulating fluids that carry solids in
suspension.
•
Plug valve,
slim valve for on/off control but with some
pressure drop.
•
Poppet valve,
commonly used in piston engines to regulate
the fuel mixture intake and exhaust
•
Spool valve,
for hydraulic control
•
Thermal expansion valve,
used in refrigeration and air conditioning
systems.
•
Pressure Reducing Valve
•
Sampling valves
•
Safety valve
By:Khalid Ayaz Soomro
Page : 76 of 105
Bearings
A device that supports, guides, and reduces the friction of motion
between fixed and moving machine parts is called bearing. This also
reduces radial movement of shaft.
General Bearings
To endure load of turbine general bearing are used. Oil supply is
always disbursed into general bearing, so that metal can’t be
rubbed together. This bearing consist of two parts
1.
2.
Upper half
Lower half
Onto this bearing we control lubricating oil temperature along with
bearing temperature. This should be exceeding from OEM
recommendations.
Thrust bearing
These bearings are installed to endure axial movement of turbine
shaft. Thus, to prevent the rotating blades with collapse to stationary
blades this bearing is installed. When force is applied on HP turbine
the shaft shifts toward generator that is called “advancing” and
when load is decreased the shaft shifts towards HP turbine that is
called “retiring”.
Thus, to prevent from any misshape or dislocation of vital turbine
parts thrust pads have been installed. Usually tilting thrust pads are
installed. White metal is applied on that pad, where hardness is less
then bearing material and these pad can tilt their direction and also
get lubrication.
By:Khalid Ayaz Soomro
Page : 77 of 105
Turning Gear
When turbine stops rotating then there is a vital chance that upper
half will be hotter than lower half casing. Thus, if shaft stops rotating a
difference will occur in-between upper and lower half of turbine
casing this will lead to shaft sag or bend. Thus, to prevent from sag
and bend turning gear rotates the shaft slowly on constant speed, so
that the temperature of shaft remain equal on both side i.e. upper
and lower half of turbine casing.
Kinds of gear
Supr gear
Helical gear
Bevel gear
Worm gear
Rack gear
Coupling
Coupling is the device which is used to joint two or more shafts
straight together, so that power can be disbursed.
Kinds of coupling
Rigid coupling
Hydraulic coupling
Flexible coupling
Magnetic coupling
Jaw coupling
Spider coupling and SSS coupling
By:Khalid Ayaz Soomro
Page : 78 of 105
Traps
Bucket trap
Expansion trap
Float trap
Thermostatic trap
Tilting trap
Kinds of relays
Instantaneous relay
Electrostatic relay
Electromechanical relay
Time delay relay
Oil System
There is three kind of oil systems are used in thermal power plants.
This system is used to lubricate the bearing and has low pressure.
Another oil system is used for sealing of generator which has medium
pressure and the third one is control oil which is usually high pressure.
Main Oil Pump
This pump operates through directly from turbine shaft. This provides
bearing lubrication and hydraulic pressure to governing system. In
big machine some centrifugal pumps are installed because their
discharge pressure is much higher, however priming shall be carried
out before taking into service.
Auxiliary Oil Pump
This pump supply oil to turbine during startup and shutdown. This
pump has been installed over main oil tank.
By:Khalid Ayaz Soomro
Page : 79 of 105
DC Lube Oil Pump
When AC supply fails or AC can’t be operated then DC lube oil
pump starts atomically. This pump only lubricates the bearings.
AC and DC Seal Oil Pump
The AC auxiliary pump is coupled with the turbine main oil pump,
however it decreases the discharge pressure for generator seals on
rare and front ends. When AC supply fails the DC lube oil pumps
starts automatically, so that hydrogen can’t expel or to prevent
hydrogen sealing.
Oil Coolers
Lubrication oil attains heat when gone through the bearings, thus to
decrease the temperature of lube oil “oil coolers” have been
installed. When hot lube oil passes through these cooler its
temperature become decreased.
Protection of Steam Turbine
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Vacuum loss
Lube oil pressure low
Turbine bearing vibration high
Turbine over speed
Axial displacement
Minimum level of hot well
Maximum level of hot well
Relative expansion differential expansion
Wet steam protection
Lube oil temperature
By:Khalid Ayaz Soomro
Page : 80 of 105
Condenser
The prime function of condenser is to condense the steam which has
been coming from LP turbine. The tubes contain raw water and
when steam hits the surface of tubes steam got condensed.
The condensation is collected in hot well, thus it can be called main
condensate water.
When steam is contacted with tube surface for condensation it is
called surface condenser and these types of condensers are used in
major power plants.
There is another kind of condenser i.e. jet type condenser.
In jet type condenser the condensate water is directly sprayed on
the steam, so that the water can take the heat from steam and
resultantly steam get condensed.
Function of Condenser
A turbine condenser accomplished two jobs. It condenses steam
coming from LP turbine and it transfer the het contained in steam to
circulating water.
Cleaning of condenser
1.
2.
3.
4.
5.
6.
7.
Back washing
CW reverse flow partially
Brushes
Plugs
Rubber balls
Hard deposit removed by chemical treatment
Jet washing
By:Khalid Ayaz Soomro
Page : 81 of 105
Steam Jet Air Ejector
It prime function is to eliminate non condensable gases from
condenser. This has been made on different stages. One separate
line of air has been taken to ejector where pressurized steam
applied. This steam expels through nozzle where velocity is
decreased and pressure is decreased. This steam takes away non
condensable gases from condenser.
Condensate Pump
These pumps take water from hot well and sent to feed tank through
LP heaters.
L.P Heaters
The condensate water flow into the tubes and gain heat from
bleeding steam and resultantly bleeding steam got condensate. This
condensate is supplied to hot well or feed tank.
Deaerator
This has been installed over the speed tank. Its prime function is to
remove non-solvable gases from condensate water. This has been
energized by using bleeding steam. A pipeline with small holes have
been installed wherefrom feed pump fall in shape of drops. The
baffle plates are inside under the pipe on which waterfalls.
Therefore, non solvable gases get eliminated and water emerges
into bottom of feed tank.
By:Khalid Ayaz Soomro
Page : 82 of 105
Feed Tank
This has been installed under the deaerator. The condense sate
water is collected here without any gases. This water is also called
boiler feed water.
Feed Pump
This feed pumps drive water from feed tank and supply it to boiler
drum through H.P heaters and economizer
H.P Heaters
The feed water passes into tubes and take heat from bleeding
steam. In this process bleeding steam got condensed and heated
water goes toward feed water. The main aspect of H.P heater is to
improve turbine efficiency and to supply hot water to boiler drum.
This saves fuel consumption.
Condensate Cycle
It is also called heat exchanger. Condenser is the device where
steam gets condensed and collected into hot well. Each unit has
three condensate pumps and two pumps in operation while the 3rd
one remains on standby position. 1st their discharge goes to steam
jet air ejector then vent condenser. Thereafter a small line goes for
condenser recirculation. The remaining condensate water travels
through main regulator and goes to LP heater No. 1 and 2 and
subsequently attained heat. Then this condensate water goes
through gland condenser and thereafter passes through LP heater
No. 3, 4, 5. After passing from all above heater the temperature of
condensate water rises from 50 0C to 140 0C and at final this
condensate water goes through non return valve and enters into a
header where two lines have been coupled to deaerator for
entering into feed tank
By:Khalid Ayaz Soomro
Page : 83 of 105
Feed Water Cycle
When feed water passes through deaerator then non condensable
gases separates at that stage and at that time temperature of feed
water is 160 0C. Feed water enters into feed pump through its suction
filter.
Each unit has 03 feed pumps. Two remain in operation while the 3rd
one is on standby position.
Suction pressure: 6kg/cm2 and discharge pressure 160 kg/cm2
According to load on machine usually two pumps in operation. The
discharge of both pumps enters into a common header and
wherefrom the feed water passes through HP heater No. 1, 2 and
economizer. At this stage feed water gain temperature 240 0C.
These HP heaters can be bypassed and resultantly economizer
directly enters into boiler drum. Feed water can also be re-circulated
through discharge recirculation line.
By:Khalid Ayaz Soomro
Page : 84 of 105
By:Khalid Ayaz Soomro
Page : 85 of 105
By:Khalid Ayaz Soomro
Page : 86 of 105
Main steam cycle
The steam get out through super heater no. 4 and enters into HP
turbine at that time its pressure is 130 kg/cm2 and temperature is 540
0C and after exiting from HP turbine it becomes 370 0C with 32
kg/cm2. This steam is sent in re-heaters where its temperature raised
upto 520 0C however its pressure remain unchanged
Thereafter at final the steam enters in LP turbine and performs work
and at the end condense in condenser. Further for starting stopping
and emergency controls HP and LP bypass station has been
installed.
HP by pass station by HP turbine whiles the LP by pass station by pass
the LP turbine. Moreover, after bypassing the steam directly enters in
condenser.
The turbine consumes 30~40 heat energy and 5 % in leakage while
the remaining heat energy collected in condenser.
Advantage of extractions
•
•
It increase thermal efficiency in feed water
It reduce the size of turbine and condenser
By:Khalid Ayaz Soomro
Page : 87 of 105
By:Khalid Ayaz Soomro
Page : 88 of 105
Generator
The operating principle of electromagnetic generators was
discovered in the years of 1831–1832 by Michael Faraday. The
principle, later called Faraday's law, is that an electromotive force is
generated in an electrical conductor which encircles a varying
magnetic flux.
He also built the first electromagnetic generator, called the Faraday
disk, a type of homopolar generator, using a copper disc rotating
between the poles of a horseshoe magnet. It produced a small DC
voltage.
The Faraday disk was the first
electric generator. The horseshoeshaped
magnet
created a
magnetic field through the disk .
When the disk was turned, this
induced an electric current
radially outward from the center
toward the rim. The current flowed
out through the sliding spring
contact m, through the external
circuit, and back into the center
of the disk through the axle.
By:Khalid Ayaz Soomro
Page : 89 of 105
Generator
Generator is the device which coverts mechanical energy into
electrical energy.
Alternator
Due to generator of voltage in AC it is called alternator
Turbo Generator
As the generator has been rotated through turbine that why it is
called turbo generator
Synchronous Generator
When generator is coupled with system and it operate according to
other generators then this is called synchronous generator
Synchronous Condenser
When generator gain power from system to improve power factor it
act like a synchronous motor then this is called synchronous
condenser.
Parts of Generator
Rotor & Stator
Casing & Bearing
Exciter
By:Khalid Ayaz Soomro
Page : 90 of 105
By:Khalid Ayaz Soomro
Page : 91 of 105
Rotor
This is rotating part of generator and field winding in nested upon it,
this is coupled with turbine shaft.
Stator
This is stationary part of generator and stator winding is nested in it,
this is coupled through bus bar to system.
Frame
Generator frame contain rotor winding, stator winding and bearing.
Generator frame restrict the outer element to get into the generator
casing. This also prevents from expulsion of hydrogen and provide
heavy support.
Bearing
The bearing share load of generator rotor and prevent from excess
radial movement.
Exciter
This device supplies DC current to rotor, so that the generator can
work on the law of electromagnetic.
Basic working principal of generator
The rotating part is called rotor and stationary part is called stator.
Generator rotor field winding is energized through DC supply which is
called excitation this produce magnetism to rotor thus it generates
magnetic flux. When generator rotor starts rotating it cut then stator
winding reacts by cutting the flux.
This product Electromagnetic flux. The EMF excites the electrons for
movement and a flow of electrons starts. So, it is called terminal
voltage or generator voltage. This excitation plays main role for
generating voltage in generator i.e. 11kV, 15.75kV or 20~30kV.
By:Khalid Ayaz Soomro
Page : 92 of 105
Synchronization
When do different electrical systems are coupled together it is called
synchronization or to connect the generator with system.
There are three main aspects during synchronization
1.
2.
3.
Generator and system voltage should be same.
Generator and system frequency should be same.
Generator and system phase angle should be equal.
Thus, if above three conditions are equal then generator should be
synchronized with system
1.
2.
3.
4.
5.
6.
7.
8.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Advantages of A.C Generator
Field winding on rotor
Less insulation
Weight of rotor less
Easy to retain centrifugal force
Size of rotor is smaller
High voltage on rotor
Transmission of voltage is easy
Easy cooling system
Generator protections
Generator differential protection
Generator over current protection
Stator earth fault protection
Rotor earth fault protection
Under excitation protection
Reverse power protection generator motoring
Negative phase sequence protection… system unbalance
Over / under frequency protection
Breaker pole failure protection
Synchronous check protection “When you system supply is
dead and you are the 1st one in the system.. no need of
synchronization”
Over excitation
By:Khalid Ayaz Soomro
Page : 93 of 105
Generator protection system
Being the ultimate device for generating electricity it value can be
rated as most liable. Thus to prevent from internal and external fault
protection system is installed
Generator faults can be categorized as follows:
Internal faults
1
System reflected faults
Certain internal faults on generator
are mechanical in nature such as;
1
* Lube oil problem
2
* Vibrations
3
* Bearing problems
4
Loss of excitation
* Cooling system problem
5
Reverse power relay
* Prime mover failures
6
Frequency protection
7
2
Electrical internal faults
8
Generator differential
protection (Primary)
Natural over current
relay
Time over current relay
(Secondary)
Over voltage
protection
Under voltage
protection
* Phase to phase fault
* Phase to ground fault
*
Negative phase sequence (or)
Un-balanced current in generator
* Rotor earth fault
By:Khalid Ayaz Soomro
Page : 94 of 105
Power Transformer
This is stationary device even though no part of this device is
rotating. This operates on the law of mutual induction. According to
faraday’s law if current is supplied in one coil the due to mutual
induction the supply will automatically enters into second coil.
Transformer work on this law and transform the current from high to
low voltage or low to high voltage.
The coil in which the current is supplied called “Primary coil” and the
receiving coil is called “Secondary coil”. The transformer can be step
up or step down. Transformers are used to reduce of improve the
generator voltage which is further supplied to system.
Parts of Transformer
Parts of Transformer
Transformer cooling system
1.
Conservation tank
1.
ON,AN (oil natural, air natural)
2.
Breather
2.
ON,AF (oil natural, air forced)
3.
Primary winding
3.
OF,AF (Oil force, air forced)
4.
Secondary winding
4.
OF,AN (Oil force air natural
5.
LT terminal
6.
HT terminal
7.
Iron core
8.
Transformer cover
9.
Oil cooler
10.
Cooling fans
11.
Tap changer
By:Khalid Ayaz Soomro
Page : 95 of 105
Power Transformer
Buchhloz relay
By:Khalid Ayaz Soomro
Page : 96 of 105
Buchholz relay
This relay has been installed in between conservator tank and
transformer. This prevent the transformer from every of kind of
internal fault which can be occur by short circuiting winding and
core terminals. Due to short circuit the oil gets overheated and
resultantly gasification will occur. These gases travels to the
conservative tank thereby buchholz relay has been placed. The
mercury switches will get operated which subsequently operate the
primary and secondary circuit breaker and generator breaker got
opened. It is also called gas operated relay.
Differential relay
This relay is operates when uneven current / load of both side
terminal i.e. LT and HT. This can be happen due to shot circuiting and
grounding of winding. These types of faults are very harmful for
generator and transformer. When such type of fault occurs this relay
is operated elsewhere this relay will not be operated.
Transformer Protection
1.
2.
3.
4.
5.
Earth fault protection
Overload relay
Buchholz relay
Oil and winding temperature high
Differential relay
By:Khalid Ayaz Soomro
Page : 97 of 105
Switch yard
1.
2.
3.
4.
5.
6.
7.
8.
Bus bar
Bus couplers
Feeder
CT & PT
Power transformer
Isolators
Breakers
Lightening arrestor
Bus-bar
These are connecting bar which are connected to various local and
distribution feeders and also intact with supply sources.
OR
Those conductors that receive source supply and distribute to
different lines.
Bus Coupler
Double bus scheme, where two bus bars are installed a provision of
bus coupler has been provided. Therein a bus coupling circuit
breaker with two isolators is called bus coupler. Its prime function is to
substantiate the supply on any bus bar without disconnecting with
system.
Feeder
The feeder is used to connect the electricity to consumer. This has
vital role is power system
CT/PT (Current and potential transformer)
These are also called instrument transformer. These are used to
measure voltage and current of different high voltage lines.
Power Transformer
These are used for set up and set down of voltage
By:Khalid Ayaz Soomro
Page : 98 of 105
Isolator
This can be termed as off load switch
Breaker
This is an on load switching device. This can be opened or closed
while sharing load.
Lightening arrestor
A lightening arrester is a device to protect electrical equipment from
over-voltage transients caused by external (lightning) or internal
(switching) events. Also called a surge protection device (SPD) or
transient voltage surge suppressor (TVSS),
By:Khalid Ayaz Soomro
Page : 99 of 105
D.C Supply
As we all know that AC supply can’t be stored. Thus the back
systems in power houses are used built on DC supply system. It is a
stand by source of electricity available at every movement in shape
of storage batteries in order to protect our main system to damage.
Importance of DC supply
All the control and protection system is based on DC supply. Usually
the AC supply is converted to DC through rectifier. Further battery
bank is also used which is charge through rectifier. This DC produced
by battery bank is used in emergency when AC is not available.
Moreover, during charging the chemical energy converts into
electrical energy.
Different parts of DC supply
1.
2.
3.
Rectifier
Battery charger
Battery cell 24VDC or 220VDC
Kinds of batteries
There are so many kinds of batteries; however below mentioned are
the one who have been chosen on their type of material and
electrode.
1.
2.
3.
Lead acid batteries
Nickel cadmium alkaline batteries
Nickel iron alkaline batteries
By:Khalid Ayaz Soomro
Page : 100 of 105
Use of battery if power station
1.
2.
3.
4.
5.
6.
7.
Control of electrical equipment
Open / close of breakers
Position indicators
Emergency lights
Field flashing
Control and protection system
Emergency pumps
Electrode + Electrolyte = Battery
Note: The charge battery has 11% water and 89% sulphuric acid and
when it discharged it become 15% sulphric acid and 15% water.
Parts of battery
Battery is consisting on many cells and each cell has negative and
positive plate. Thus more cells produce more current. The battery
power has been measured in Amp/hr.
220VDC=108 cells=592 Amp/hr
Capacity of battery
24VDC=39 cells=100 Amp/hr
Parts of battery
1.
2.
3.
4.
5.
6.
7.
8.
Plate
Group
Element
Separator
Cell connector
Vent plug
Body
Electrolyte
By:Khalid Ayaz Soomro
Page : 101 of 105
Cooling tower
The prime function of cooling tower is to cold the hot water through
its structural design and fans therein 75% hot water get cold by
evaporation whereas 25% hot water get cold through air.
All cooling towers operate on the principle of removing heat from
water by evaporating
Structure
There a fan on the top of each cell of cooling tower and below the
fan (fiber) water tubes are placed which convert the water into
small particles. The titling edges are lay down on the side wall of
each cell which prevent the water from fall outside the basin. The
fan through the air outside the tower fan assembly and from this
action the process of evaporation or removing heat from water
occurs.
The water in the basin of each cell is called pit (hot basin) and
thereafter connected to cold basin (C.W pump suction). This cold
basin water is re-circulated through C.W Pumps. During this process
3% loss occurs which has been compensated / makeup through
tube wells.
By:Khalid Ayaz Soomro
Page : 102 of 105
By:Khalid Ayaz Soomro
Page : 103 of 105
Temperature measurement in cooling tower
To calculate the temperature of atmosphere and water two kinds of
meters are used i.e. Dry bulb and Wet bulb
The atmospheric temperature has been monitored through dry bulb
whereas water temperature is measured through wet bulb.
By:Khalid Ayaz Soomro
Page : 104 of 105
Abbreviations
NDT
DPT
MPI
XRT
UST
LED
WDS
AVR
OTC
FIC
SCADA
PLC
DCS
NTDC
UPS
SFC
BST
SCBA
PASS
TDS
APH
EMF
SOP
BTG
CP
MUP
MSV
ESV
QCV
NPCC
BOP
GUD
TSE
SSS
Non destructive test
Dye penetrate test
Magnetic particles inspection
x-ray test
Ultra sound test
Light emitting diode
Watch dog system
Auto voltage regulator
Calculated outlet temperature
Frequency influence control
Supervisory control and data acquisition
Programmable logic control
Distributed control system
National transmission and dispatch company
Uninterruptable power supply
Static frequency converter
Baroscopic test
Self contained breathing apparatus
Personal alert safety system
Total dissolved salts
Air pre-heater
Electro motive force
Standing operating procedure
Boiler turbine generator
Condensate pump
Makeup pump
Main steam valve
Emergency stop valve
Quick closing valve
National power control center
Balance of plant
Gas and draft
Turbine stress evaluator
Synchro self shifting
By:Khalid Ayaz Soomro
Page : 105 of 105