ali guddu report thesis

Internship Report at TPS Guddu Combine report from june 15 to july 15 2014 And 05 june to 15 june 2015

BYAli Muhammad(k-13EL-19)3rd year B.E Electrical MUET khp

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ALI MUHAMMAD (K13-EL-19)

FIRE ANDSAFETY

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FIRE

Fire is the rapid oxidation of a material in the exothermic chemical process of combustion, releasing heat, light, and various reaction products i.e. toxic gases and smoke.

PRINCIPLE OF FIRE

Fires start whe n 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. T his is commonly called the fire tetrahe dron (three-dimensional case).


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Fire cannot exist without all of these elements in place and in the right proportions

1. Oxygen2. Fuel3. Heat

When fire take place, below mentioned three objects can be observed easily.

1. Hot Gases (emission)2. Light3. 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. Name of Gas Symbol % in air1 Nitrogen N2 78%2 Oxygen O2 21%3 Carbon Dioxide CO2 1%

The flash point of different fuels is listed below.

S/No. Name of Gas Flash Point Auto ignitiontemperature

1 Gasoline (Petrol) -43 OC 280 OC2 Furnace Oil (RFO) >60 OC 407 OC3 Natural Gas >93.3 OC 580 OC4 Kerosene Oil >37 to 65 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 -- Wood, Coal, Lignite, Peat etc.

2. Liquid --Petroleum, Diesel, Fuel Oils, Alcohols etc.

3. Gaseous – Natural Gas, Coal Gas, Hydrogen etc.


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TYPES OF FIRE

Class C fires are fires involvingenergized electrical equipment

3 Csuch as motors, transformers, andAppliancesFires that involve combustiblemetals, such as s odium,

4 D magnesium, an d potassium

5 E gases, such as natural gas,hydroge n, prop ane, b utane

Fires that involve flammable

S/No. Fire Class Symbol PropertiesFires that involve flammable


1 Asolids such as wo od, cloth,rubber, paper, a nd some typesof plastics

Fires that involve flammableliquids or liquefia ble solids such as

2 B petrol/gasoline, oil, paint, somewaxes & plastics, but not cookingfats or oils

Fires involving co oking fats & oils.The high temp. o f oils when on

6 F or K fire far exceeds that of otherflammable liquid s making normalextinguishing agents ineffective.

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TYPES OF FIRE AND EXTINGUISHING

Fuel Source Class Type of Extinguisherof Fire (Extinguishing Agent)

Ordinary combustibles(e.g. trash, wood, paper, A Water; chemical foam

cloth)Flammable liquids

Carbon dioxide (CO2); dry(e.g. oils, grease, tar, B chemical; film forming foamgasoline, paints, thinners)Electricity

(e.g. live electrical C CO2; dry chemicalequipment)

Combustible metals Dry powder (suitable for theD specific combustible metal(e.g. magnesium, titanium) involved)

Combustible gasesE A.B.C powder(e.g. Natural Gas, Butane)

Combustible CookingWet chemical (Potassium(e.g. cooking oils; animal F or K acetate based)fats, vegetable fats)


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PORTABLE AND SEMI PORTABLE FIRE EXTINGUISHERS.

Fire Class Extinguisher TypeA Soda AcidA Water TypeBCDE Carbon DioxideAB Foam TypeABCD Chemical Powder, Dry TypeABCE B.C.F HalonBE 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 connected3. 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 exitEnter low into fire zone.Remove endanger personTake control

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FUNDAMENTALS FOR EXTINGUISHING FIRE

The below mentioned are basic fundamental rules to extinguishing fire

1. Starvation2. Smothering3. Cooling

StarvationRemoving fuel from fire triangle is called elimination of fire starvation.

SmotheringRemoving oxygen from fire triange is called smothering

CoolingTo decrease the temperature of fuel from ignition point is called cooling

PRECAUTIONARY MEASURES

1. To store carefully hazardous fuels i.e. petrol, oil, thinner etc.2. To stop leakage in oil lube, hydrogen, natural gas lines etc.3. To observe the increase in bearing temperature of I.D and

F.D fans.4. Always observe the oil leakage where steam and oil lines

in vicinity.5. Cotton rags should be kept in safe place.6. Whenever oil is used in plant or workshop the excessive

quantity should be returned back to store.7. Where smoking is not allowed, make sure that the

rule is followed.8. 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 non-desirable.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 CODEThe 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 GuardingDuring work all safety gears should be wear i.e. gloves, safety shoes, safety goggles etc.3. Defective MaterialBefore 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. HazardsEverything 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. Thu s during work on electrical pole or any place alike that, safety belt must be used. Safety shoes

9. Welder protecti ve 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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INTRODUCTIONTO

POWERPLANTS

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BASIC CONCEP T OF MODERN POWER P LANTS

The modern power complex consists on Steam and Gas Turbine has three major concepts.

S/No. Name and History Concept

1Willian Rankin e’s (1845~1865) Where heat is added in waterThermodynam ics boiler to conv ert heat into

work2 George Brayto n (1872) Where heat is added and

Thermodynam ics discharged at constantpressure

3 Michael Farad ay (1831) When a perm anent magnet isdiscovery of induction in 1831 moved relativ e to a

conductor, or vice versa, anelectromotive force iscreated. If the wire isconnected through anelectrical load, current willflow, and thus electricalenergy is gene rated

Faraday's iron ring ap paratus. 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 CAT EGORIES 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. BOILER2. TURBINE3. 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 Boiler1. Water tube boiler 2. Fire tube boilerWater 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 press ures.

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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 3.Planten SH A.Radiant Zone

4. Convective SH 5. Re-heater 6.Economizer B.Radiant Zone

7.Air preheater 8. Water wall C. Convection zone

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1. Boiler Drum 2. Furnace 3. Burner 4. Down Comer 5. Lower Drum6. Radiant S.H 7. Platen S.H 8. Convective S.H 9.Reheaters 10. Economizer11. Air Pre Heater 12. Air Duct 13. F.D Fan 14. Calorifire 15. I.D Fan16. Chimney 17. Soot Blower 18. Generation Tubes 19. GRC 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

9 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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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 purificationat 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 waterOR

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 GasesDuring burning of fuel some gases are expelled which are called flue gases.

BurnersBurner 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 operate3. 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. It increases the temp. of saturated steam.2. It is used to dry the steam3. 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 heater2. Platen Super heater3. 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

Advantage of super heated steam1. Improve turbine efficiency2. No harm can occurred to turbine blade due to wet steam3. No rust will occur to turbine blade4. Blades does not bend

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Steam temperature control in boiler

1. De-super heatera. Atomprationb. F.W injection

2. Gas recirculation fan3. Fuel increased / decreased4. Air flow control5. Tilting of burner position6. Soot blowing7. Shot blasting

RE-HEATERS

Re-heater can also be termed as super heater. They can also becalled as intermediate super heaters. These are installed in flue gasduct. The get heat through flue gases and rises wet steamtemperature. There is no temperature different in re-heater or superheater. However due no decrease in steam pressure it is called re-heater. The pressure decreases due to line resistance.

Duties of re-heaters

1. Re-heaters increase the temperature of cold reheat steam2. 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 economizer1. It increase the temperature of feed water2. Receives heat from flue gases3. Lower the temperature of flue gases4. Reduces the size of boiler5. Increase the efficiency of boiler upto 1% in terms of

fuel consumption6. 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-heaters1. Regenerative2. Recuperative

(i) Tubular(ii) Plate type

Advantages of air pre-heating1. Improved combustion and efficiency use of fuel2. Stabilized fuel ignition which improves low

load combustion3. Increased steam generation capacity4. Better utilization of low grade, high ash fuel5. Minimized size of boiler6. 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 flexibility8. 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

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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.


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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. Flue gases2. Exhaust gases3. Exist gases4. Chimney gases5. Stack gases6. Hot gases

Duties of ID Fan1. It suck flue gases from furnace2. It provides zero pressure in the furnace. (it slightly operates

on negative pressure)3. 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 Fan1. Continue air supply for combustion2. 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.

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Schematic of ID and FD Fans

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Chimney / Stack

The first industrial chi mneys were built in the mid-17th century when it was first understood how they could improve the c ombustion of a furnace by increasing the draught of air into the com bustion 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 perf orated bricks. Generally they are made of several sections. For short exhaust stack, steel chimneys are preferre d. Steel chimneys are particularly favored in the case of G TPS because a gas turbine attains its full load in less 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 boiler s working on partial load are connected to a commo n chimney. The phenomena of cold air inversion takes place; when the flue gas pressure inside the chimney is less th an the air pressure outside the chimney


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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.

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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.


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Schematic of boiler safety vlave


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Boiler Surface

1. Water surface

Waer surface include the following parts of boiler

1. Economizer 100%

2. Boiler drumpartially

3. Down comers 100%4. Generation tubes partially

2. 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.

·Thereare three tyoes of heating surfaces in a boiler

(i) Radiant heating surface(ii) Radiant convective heating surface(iii) Convective heating surface

3. Heat transfer surface

All the compnents of boiler, except down comers, includign furnace, super heater, re-heaters, de-super heaters are heat transfer surfaces

·Advtanges of long flue gases path

(i) Heat stays in the flue gases path for maximum possible time.

(ii) Different compenets placed in the flue gases path absorb heat from the flue gases.

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· Ratio of heat absorbed by different compenents placed in the foue gases path

1. Water wall 48%2. Super heater 15%3. Air preheater 10%4. Economizer 07%5. Re-heater 08%6. Chimney 12%

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Boiler Draught

The pressure difference between furnace and atomospheric air is called draught. There are two kinds of draughts.

Natural draughtWhen the draught is generated with the help of the chimney only, it is called natural draught.ORWhen 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 DraughtThe 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

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low draught loss nee ds. In order to meet higher press ure differentials, the stacks must simultaneously operate with draught fans.

Types of artificial dra ughts

Positive: When fur nace pressure is greater tha n atmospheric pressure. It also called forced draught. O nly F.D is used in it.

Negative: When furnace pressure is less than atmospheric pressure. It is also call ed induct draught. Only ID is used in it

Balance: With both F.D and I.D fan whne used simul taneously


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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

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Boiler safety interlock

Prevents fuel form being admitted toPre-purge inter lock a furnace until the furnace has been

thoroughly air purged to removeresidual combustibles

High steam pressure interlock Fuel is shut off upon abnormally

higher boiler steam pressure

Fuel is shut off upon loss of air flowLow air flow interlock from the combustion air fan or

blower, the I.D and F.D fanFuel is shut off upon loss of fuel supply

Low fuel supply inerlock pressure would resulting unstableflame condition

Loss of flame interlock All fuels is shut off upon loss of flamein the furance or individual burner

Fan inerlock Stop FD from upon loss of ID fan

Low water interlock Shutoff fuel on low water level boilerdrum

High combustibles interlock Shut off fuel on highly combustiblecontent in the flue gases

Continues fan operation to remove

Post purge interlockresidual combustion from the furnaceprior to shutting down the fan


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COMBINEDCYCLE

POWERPLANT

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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.

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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 HRSG1. To provide sufficent steam to turbine.2. To supply steam and hot water on commercial basis to offices. 3. To supply seam to sugar, cloth, wood mils4. To clean the sea water into drinking water / desolination plant

Parts of HRSG1. Feed water gate and regulator valve2. Economizer3. H.P Drum4. Evaporator re-circulation pump5. Evaporator6. Super heater7. By-pass damper8. Isolation Damper9. Weather damper / stack damper

Protection of HRSG1. Drum level low low2. Drum level high high3. Live steam temperature > 540 0C4. Evaporator circulation pump tripped.5. G.T Tripped6. HP Bypass station tripped7. G.T flue gases pressure high (50mbar alarm…. 70 mbar trip)8. Vacuum low9. Pressure rising OR dropping at the rate >4 bar min (ramp

rate)

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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. Filter House2. Axial Flow Compressor3. Combustion Chamber4. 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

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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 Turbine1. Fuel gas system2. Lube oil system3. Fuel oil system4. Cooling water system

Advantages of gas turbine1. Neat to load center2. As synchronous condenser3. Peak hours loading4. Black start provision5. Less auxiliaries6. Less are required due to being compact7. Short starting time8. Easy for operation9. Power supply in emergency

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Gas Turbine protections

1. Exhaust temperature high2. Thrust bearing temperature high3. High vibration4. Loss of flame5. Lube oil pressure low / high6. Fuel pressure low / high7. Lube oil temperature high8. Over speed9. Compressor surging

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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 RotorThis 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.

ShaftTurbine 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.

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Requirement of SealingThe 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. Stuffing boxes2. Carbon ring packing3. Labyrinth seal4. Water glands

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Turbine blades

There are two kinds of turbine blades

1. Stationary or fixed blades2. 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 type2. Impulse type

Reaction Type TurbinePressure continuous drop and volume increased in stator blades and in moving blades pressure remains constant and volume becomes decreased

Impulse TurbinePressure 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.

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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.

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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, andideal for quick shut-off, since a 90° turn offerscompleteshut-offangle,comparedtomultiple 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 oronabrasivefluids.Ceramicdisccanalsoprovide 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 cylinderwhichisplacedaroundorinsideanothercylinder which has holes or slots. Used for highpressure drops found in oil and gas wellheads.

· Diaphragm valve, whichcontrolsflowbyamovementofadiaphragm.Upstreampressure,downstreampressure,oranexternalsource(e.g.,pneumatic, hydraulic, etc.) can be used tochange the position of the diaphragm.

· Gate valve, mainlyforon/offcontrol,withlowpressuredrop.

· Globe valve, good for regulating flow.

· Knife valve, similartoagatevalve,butusuallymorecompact. Often used for slurries or powderson/off control.

· Needle valve for accurate flow control.


· Pinch valve, for slurry flow regulation and control.Page : 75 of 105


· Piston valve, for regulating fluids that carry solids insuspension.

· Plug valve, slimvalveforon/offcontrolbutwithsomepressure drop.

· Poppet valve, commonly used in piston engines to regulatethe fuel mixture intake and exhaust

· Spool valve, for hydraulic control

· Thermal expansion valve, usedinrefrigerationandairconditioningsystems.

· Pressure Reducing Valve

· Sampling valves

· Safety valve

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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. Upper half2. 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.

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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 gearHelical gearBevel gearWorm gearRack 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 couplingHydraulic couplingFlexible couplingMagnetic couplingJaw couplingSpider coupling and SSS coupling

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Traps

Bucket trapExpansion trapFloat trapThermostatic trapTilting trap

Kinds of relays

Instantaneous relayElectrostatic relayElectromechanical relayTime 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.

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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. Vacuum loss2. Lube oil pressure low3. Turbine bearing vibration high4. Turbine over speed5. Axial displacement6. Minimum level of hot well7. Maximum level of hot well8. Relative expansion differential expansion9. Wet steam protection10. Lube oil temperature

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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. Back washing2. CW reverse flow partially3. Brushes4. Plugs5. Rubber balls6. Hard deposit removed by chemical treatment7. Jet washing

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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.

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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

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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.

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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

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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 horseshoe-shaped 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.

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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 & StatorCasing & BearingExciter

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RotorThis is rotating part of generator and field winding in nested upon it, this is coupled with turbine shaft.

StatorThis 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.

BearingThe bearing share load of generator rotor and prevent from excess radial movement.

ExciterThis 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.

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SynchronizationWhen 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. Generator and system voltage should be same.2. Generator and system frequency should be same.3. Generator and system phase angle should be equal.

Thus, if above three conditions are equal then generator should be synchronized with system

Advantages of A.C Generator1. Field winding on rotor2. Less insulation3. Weight of rotor less4. Easy to retain centrifugal force5. Size of rotor is smaller6. High voltage on rotor7. Transmission of voltage is easy8. Easy cooling system

Generator protections1. Generator differential protection2. Generator over current protection3. Stator earth fault protection4. Rotor earth fault protection5. Under excitation protection6. Reverse power protection generator motoring7. Negative phase sequence protection… system unbalance8. Over / under frequency protection9. Breaker pole failure protection10. Synchronous check protection “When you system supply is

dead and you are the 1st one in the system.. no need of synchronization”

11. Over excitation

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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 faultsSystem reflected faults

1Certain internal faults on generator

1Generator differential

are mechanical in nature such as; protection (Primary)* Lube oil problem 2 Natural over current

relay

* Vibrations 3

Time over current relay(Secondary)

* Bearing problems 4 Loss of excitation

* Cooling system problem 5 Reverse power relay

* Prime mover failures 6 Frequency protection

7 Over voltageprotection

2 Electrical internal faults 8 Under voltageprotection

*Phase to phase fault

*Phase to ground fault

*Negative phase sequence (or)Un-balanced current in generator

* Rotor earth fault

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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 system1. 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 natural5. LT terminal6. HT terminal7. Iron core8. Transformer cover9. Oil cooler10. Cooling fans11. Tap changer

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Power Transformer

Buchhloz relay

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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. Earth fault protection2. Overload relay3. Buchholz relay4. Oil and winding temperature high5. Differential relay

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SWITCH YARD

1. Bus bar2. Bus couplers3. Feeder4. CT & PT5. Power transformer6. Isolators7. Breakers8. Lightening arrestor

Bus-barThese are connecting bar which are connected to various local and distribution feeders and also intact with supply sources.ORThose conductors that receive source supply and distribute to different lines.Bus CouplerDouble 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.FeederThe feeder is used to connect the electricity to consumer. This has vital role is power systemCT/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 TransformerThese are used for set up and set down of voltage

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IsolatorThis can be termed as off load switch

BreakerThis is an on load switching device. This can be opened or closed while sharing load.

Lightening arrestorA 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),

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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. Rectifier2. Battery charger3. 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. Lead acid batteries2. Nickel cadmium alkaline batteries3. Nickel iron alkaline batteries

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Use of battery if power station

1. Control of electrical equipment2. Open / close of breakers3. Position indicators4. Emergency lights5. Field flashing6. Control and protection system7. 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/hrCapacity of battery

24VDC=39 cells=100 Amp/hr

Parts of battery

1. Plate2. Group3. Element4. Separator5. Cell connector6. Vent plug7. Body8. Electrolyte

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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.

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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.

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AbbreviationsNDT Non destructive testDPT Dye penetrate testMPI Magnetic particles inspectionXRT x-ray testUST Ultra sound testLED Light emitting diodeWDS Watch dog systemAVR Auto voltage regulatorOTC Calculated outlet temperatureFIC Frequency influence controlSCADA Supervisory control and data acquisitionPLC Programmable logic controlDCS Distributed control system

NTDCNational transmission and dispatch company

UPS Uninterruptable power supplySFC Static frequency converterBST Baroscopic testSCBA Self contained breathing apparatusPASS Personal alert safety systemTDS Total dissolved saltsAPH Air pre-heaterEMF Electro motive forceSOP Standing operating procedureBTG Boiler turbine generatorCP Condensate pumpMUP Makeup pumpMSV Main steam valveESV Emergency stop valveQCV Quick closing valveNPCC National power control centerBOP Balance of plantGUD Gas and draftTSE Turbine stress evaluatorSSS Synchro self shifting

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