INDEX

Acknowledgement Introduction DSTPS: Andal 2x500 MW Power Plant Main parts of the plant Coal Handling Plant Boiler TG Section Balance of plant Electrical Package Safety Quality Finance Conclusion

ACKNOWLEDGEMENT

I have completed my vocational training at DSTPS (Durgapur Steel Thermal Power Station) site where I got a first hand experience of The Thermal Power Plant. In the process of completing this industrial visit, I interacted with a lot of engineers and site professionals who donated their valuable time for making me understand the basics of boiler assembly and operations. In this regard I would like to extend my thanks to Mr. D. K Navin, Mr. A. Shah, Mr. Anand, Mr. R. Kumar, Mr. Hoque, Mr. Rehman, Mr. S. Bitter, Mr. S. Majumdar, Mr. S. Mukhopadhyay and many others. Finally I would like to extend my heartiest thanks to my training co-ordinators Mr. A. K. Guha, Mr. P. Pandit and Mr. D. Roy and last but not the least my heartiest thanks to Mr. S. Bhattacharya, The Honourable G.M. of Bharat Heavy Electricals Limited (BHEL) who structured the whole training procedure, guided us through the whole plant and power manufacturing process and was there to answer our random questions with an air of confidence.

INTRODUCTIONBHARAT HEAVY ELECTRICALS LIMITED (BHEL) is one of the oldest and largest state owned engineering and manufacturing enterprise in India in the energy- related and infrastructure sector which includes Power, Railways Transmission and Distribution, Oil and Gas sectors and many more. It is the 12th largest Power equipment manufacturer in the world. BHEL was established more than 50 years ago, ushering in the indigenous Heavy Electrical Equipment industry in India. The company has been earning profits continuously since 1971-72 and paying dividends since 1976-77.74% total power generated in India is produced by equipment manufacture by BHEL.

It is one of the India's largest Public Sector Undertakings or PSUs , known as the Navratnas or the nine jewels. I am a students of Bengal College Of Engineering and Technology, Durgapur, was permitted to have an experience enriching Vocational Training at Durgapur Steel Thermal Power Station, (DSTPS), Andal with a permission letter bearing ref. no. :1. Gourhari GhoshI was provided with a training schedule of four weeks duration of practical training from the OFFICE OF THE GENERAL MANAGER which included every eminent part of the power plant.This project report regarding Vocational Training is being submitted on the basis of first-hand training undergone at Durgapur Steel Thermal Power Station (DSTPS). Here 2(two) units, each of capacity 500MW, are under construction by M/s BHEL who has been awarded this contract on Turnkey basis by M/s Damodar Valley Corporation (DVC), the owner of this project.

Name of Project:-2x500 MW DURGAPUR STEEL THERMAL POWER STATION Location: Andal, Durgapur, Dist.-Burdwan (West Bengal) Name of Customer: Damodar Valley Corporation (DVC) Name of Contractor: Bharat Heavy Electricals Limited Area: The total area of the plant is 3.47sqkm. Seismological data: The area falls in Zone-3 of seismological zone.Communication: The site is located 0.5 km away from NH-2. The nearest railway station is Andal station which is about 3 km away from the site

MAIN PARTS OF PLANTThe central steam station works on Rankine Cycle. Coal is burnt in the furnace to produce heat, which is utilized to form steam out of feed water. This steam is utilized to run the Steam Turbine, which is the Prime Mover to the alternator & power is generated. This steam is condensed in the condenser & reutilized However certain machineries have been added to the Power Plant to ensure heat economy & to enhance the Thermal efficiency of the Plant.The plant can be divided into four main circuits, namely:- 1. Fuel & Ash circuit. 2. Air & Gas circuit. 3. Feed water & Steam circuit. 4. Cooling Water circuit.

1.FUEL & ASH CIRCUIT:-Fuel (coal ) is fed from storage at Coal Handling Plant (CHP )to the Boiler furnace through fuel handling and feeding units such as the conveyer belts, coal bunkers, bowl mills and pipe lines arranged as Coal A, Coal B having 8 such. The ash produced, as a result of combustion of coal in the furnace to produce heat, collects at the back of the furnace & this ash is removed to ash storage unit using ash handling equipments initially & then to Ash Handling plant using other means of transport.2. AIR & GAS CIRCUIT:- Air for combustion is fed into the boiler furnace using Forced Draught fans (FD fans). This air is initially passed through the air-preheater where the air uses the heat of flue gases & gets heated up. The waste flue gases are then made to pass through chimney using Induced Draught fans (ID fans).

3. FEED WATER & STEAM CIRCUIT:-The feed water & steam circuit consists of the Boiler, Condenser, Condensate Extraction Pump(CEP), LP Heater, HP Heater, Deaerator, Boiler Feed Pump(BFP).4. COOLING WATER CIRCUIT:- Large amount of water is required to convert the steam utilized in Turbine back to water in the Condenser & to maintain a low pressure.The above constructions of a Thermal Power station are briefly described as follows:COAL HANDLING PLANTCoal, which is primary Fuel of a thermal power plant, burnt in the furnace to produce steam, reaches the power plant in the form of large chunks. This coal, if fed to the boiler furnace, would result in inefficient, incomplete & smoky combustion. Hence this coal is pulverized (finely grinded into almost powdery form) in multiple stages in the coal mill located in the coal handling plant. Raw coal is carried out of the coal bed with the help of conveyor belt; it is further pulverized in bowl mills & sent to the boiler furnace. This pulverized coal ensures the complete & efficient combustion. The design of the coal handling plant must be able to meet the daily requirements of the power station. A number of factors like steam parameters, type of thermal cycle, carbon content of coal used, efficiency of the boiler determine the coal consumption. The estimated coal consumption of a station is about 150 tonnes/hour.. The following steps take place in a coal handling plant:-1. Coal receipt & unloading at the station2. Coal crushing.3. Manual sorting and storage of coal.BOILERBOILER MEANS ANY CLOSED VESSEL EXCEEDING 22.75 LTRS. IN CAPACITY WHICH IS USED FOR GENERATING STEAM UNDER PRESSURE. -IBR

TYPES OF BOILERA) BASED ON APPLICATION:-1. UTILITY: Boilers are large capacity steam generators used purely for electrical power generation.2. INDUSTRIAL: Boilers are small capacity boilers intended for use in the process industries. B) BASED ON FUEL FIRING:-1. OIL FIRED2. OIL AND COAL FIRED3. STOKER FIREDD) BASED ON NO. OF DRUMS:- 1. SINGLE DRUM 2. BI- DRUM3. NO DRUM (Vertical Separator) - SUPER CRITICAL BOILER E) BASED ON CIRCULATION:-1. NATURAL1.1. FORCED Circulation (Pump)1.2. CONTROLLED Circulation (+Orifice)2. ASSISTED

BOILER PARAMETERS(A) UTILITY BOILER:- 1. Main Steam Flow T/Hr.2. Main Steam Pressure Kg/Sq.Cm.(g)3. Main Steam Temperature - c 4. Reheater Flow T/Hr.5. Reheater Pressure Kg/Sq.Cm.(g)6. Reheater Temperature - c (B) INDUSTRIAL BOILERS: - Steam Flow T/Hr. (C) HEAT RECOVERY UNITS: - Fuel Used T/Day.

PRESSURE PARTS(A) BASED ON CONFIGURATION : 1. HEADERS2. PANELS3. COILS4. CONNECTING LINKS5. SUPPORTS & SUSPENSIONS(B) BASED ON SYSTEM : 1. ECONOMISER SYSTEM2. CIRCULATION SYSTEM3. SUPERHEATER SYSTEM4. REHEATER SYSTEM

BOILER FLOW PATH ECONOMISER Eco inlet Link Eco inlet Header Eco Coils Eco Outlet Header Eco Connecting Links to Drum DRUM With Internals DOWN COMERS Suction Manifold Circulating Pumps (CC Pumps) Discharge Lines WATER WALL INLET HEADERS WATER WALL PANELS (Front ,Rear side) WATER WALL Loose tubes (Hanger and screen) Water wall outlet headers. Risers Drum Saturated connecting links to Radiant roof inlet header Radiant roof inlet header Radiant roof Tubes Radiant roof outlet header Back pass upper side inlet headers. Back pass wall panels Back pass lower front side inlet header

Path---1 Back pass Front wall tubes Back pass roof Back pass Roof junction header Low temperature Super heater inlet header through back pass rear upper tubes. Path---2 Economizer support tubes Eco support tubes intermediate headers LTSH support tubes Back pass Roof junction header Back pass rear upper tubes Low temperature Super heater inlet header. Path---3 Back pass side wall lower outlet header (rear) Back pass rear wall lower inlet header Back pass lower rear wall tubes Low temperature Super heater inlet header. LTSH banks LTSH Outlet header LTSH terminal tubes LTSH links to DESH Divisional panellete super heater inlet headers Divisional panels Divisional panellete super heater outlet headers Div. panel outlet link to platen inlet header Platen super heater inlet header Platen super heater coils Platen super heater outlet header Main steam line Reheater circuit Reheater inlet header Reheater coils Front Reheater coils rear Reheater outlet header. Reheater outlet line ( cold reheat line)

CIRCULATION SYSTEMThe circulation system of water through the furnace water wall is due to either natural circulation or controlled circulation. Natural circulation boilers employ the effect of density differences between water and steam to produce circulation. At higher pressures and height of the boiler where density difference is not adequate the difference is augmented by a pump and orifice effecting Controlled circulation.

PARTS OF BOILER:a. To provide space for separation of steam from steam water mixture.b. To house the internals required for steam separation such as Feed water distribution system, Turbo separators, Separating chamber, Screen driers etc.c. To provide a water storage for preventing the starvation of tubes during operation. d. Thickness of drum bears the stresses induced due to internal pressure, self weight and external loads.e. Mixing feed water from economiser and water separator from water-steam mixture.f. Carrying Blow-down for reduction of boiler water salt concentration .DOWNCOMERS:-a. Downcomers connected to bottom of the drum.b. Water from Boiler drum is circulated to water wall tube through downcomers.c. It is placed out of the heating zone.d. There are 6 downcomers for 500 MW Power Plant.

FURNACE AND BACKPASS WALLS:-Normally for boiler furnace enclosures membrane wall construction (fusion welded panels) is adopted in place of tangent tube construction which is not leak proof and increased erection work. Back pass enclosures are formed by fin welded panels with wider pitch is installed because the flue gas temperature is less compared to furnace. CIRCULATING PUMP:-There are 3 Circulating pumps in boiler by which forced circulation is occurring and its function is only to circulate the water in the boiler and not to increase its pressure.DETAILS:- Type - single suction double discharge.Design Pressure-208.5 kg/cm2Design Temperature -366oC Hydro Test pressure -312.8 kgf/cm2 Suction pressure -195.6 Kgf/cm2Quantity pumped -48453 Litre/min. Wt. Of pump case- 3425 Kgs.

BOILER ACCESSORIES1. AIR PREHEATER:- If the air entering the boiler furnace is pre-heated, better combustion is ensured. Pre-heating the air is done in an air preheater resulting in complete combustion of even low grade fuels like LIGNITE. The heat of the flue gases is utilized to preheat the air entering the boiler furnace. The thermal efficiency of the plant also increases as a result of this preheating.2. ECONOMIZER:- The economizer is a boiler accessory which is used to heat the Feed Water entering the Boiler Drum, the heat being taken from the flue gases. Commonly Greens Economizer is used in Power Plants. Since the feed water is already heated to a high temperature, steam can be quickly produced from it in the furnace by using lower amount of heat thus increasing the boiler efficiency. 3. SUPERHEATERS:-These heating surfaces are in the form of coils which are made by bending the tubes in cold or hot condition. The superheater is composed of four basic sections. The platen section and divisional panellete section is located directly above the furnace in front of the furnace arch and absorb heat mainly by radiation. The horizontal section of the low temperature superheater is located in the rear gas pass above economizer. The steam cooled wall sections form the side, front and rear walls and roof of the vertical gas pass. De-superheaters: Provided in:1. Superheater Connecting Links2. Cold Reheaburners. 4. REHEATERS:- The Reheater consists of a single stage having 2 Sections-Front & rear pendant vertical spaced. The front section located between the rear water wall hanger tubes and the superheater platen section. The rear section is located between water wall screen and rear wall hanger tubes.

PRIMARY AIR FAN(PA Fan)Primary air fan supplies the air for sealing the bearing from coal powder in the coalmill ,drying and transporting the pulverized coal from the mill classifier to the boiler furnace. The PA fan is an axial type fan. There are 2 PA fans each having 2 stages and 20 blades in each stage.

FORCED DRAUGHT FANThe FD Fans supply secondary air, which is heated by Air Pre-heater. Secondary air is required to provide excess air for combustion in the furnace. There are 2 FD Fans each having a single stage with 18 blades present in the stage.

The different parts of the fans are as follows: Diffuser Housing Suction chamber Expansion joint Silencer Roof assembly INDUCED DRAUGHT FAN:- Two ID Fans are provided at the base of the chimney, which suck the flue gases produced due to combustion of Coal & discharge these gases through the chimney. ID fan is a radial type fan and its speed is controlled by variable frequency drive.

COAL MILLCoal Mill is a very critical part of a power plant both from operation and maintenance point of view. It is a very important boiler auxiliary as it pulverizes the coal and feeds the pulverized coal to the boiler via the burner. TYPES OF COAL MILL 1. Ball/Tube/Drum Mill2. Bowl Mill &Race Mill3. Impact/Hammer MillHere we use Bowl Mill as the speed of the mill is between 40-70 rpm. General Specification of Bowl Mill (A) Speed : 40-60 rpm(B) Capacity : As per size(C) Motor Speed : 600-1000 rpm(D) No. of mills : 10(E) Input coal size : 25 mm(F) Output coal size : 65-75 micron Nomenclature of Bowl Mill XRP 1003 where X- Frequency of power supply R- Raymond(Name of the inventor) P- Pressurized type with PA Fan before mill 100- Bowl Hub Diameter in inch 3-No of RollersMAJOR PARTS OF BOWL MILL: The different parts of Bowl Mill are given below :- 1.Inlet Cone 2. Bowl Plate 3. Bullring segment 4. Classifier or Seperator 5. Central feed pipe 6. Roller 7. Gear box 8. Outlet coal pipe 9. Seal air system 10. Mill rejector 11. MDV(Mill discharge valve)

A TYPICAL BOWL MILL

Functioning of the Bowl Mill: There are two primary air ducts each providing primary air to 5 mills. Hot primary air is passed to the mill through the air inlet chamber to dry the coal and remove the pulverised coal dust from the pulverising zone to the burner. There is an inlet coal pipe which is connected to the Central Feed Pipe in Mill Inlet Housing and through this central feed pipe coal enters the mill. A motor is present which rotates the gearing arrangement in the gearbox as a result of which bowl hub rotates. As the rollers are connected to the bowl hub, the rollers also rotate. The coal particles fall on the bowl and due to centrifugal force they are thrown away towards the rollers where they get crushed and pulverized. The hot air coming from the air inlet chamber carries the pulverized coal through separator body to the separator top also known as classifier. In the classifier, vanes are present where relatively larger coal particles get separated and fall back to the bowl and the smaller particles along with the hot air passes through the mill discharge valve onto the outlet pipes from which it is transported to the burner. The coal particles which are unable to get pulverized into required size passes through the mill rejection chamber onto the pyrite hopper.

5. ELECTROSTATIC PRECIPITATOR:The electrostatic precipitator utilizes electrostatic forces to separate ash from the gas to be cleaned , the gas is conducted to a chamber containing curtains of vertical steels plates called collecting electrodes. These electrodes divide the chamber into a number of parallel gas chambers. An EMITTING FRAME is located in each passage. All frames are linked to each other to form a rigid framework. The entire framework is held in place by four support insulators which insulate it from all parts, which are grounded.A high voltage direct current is connected between framework and ground thereby creating a strong electrical field between the springs in the framework and the steel curtains . The electrical field becomes strongest between the surfaces of the springs & it is so strong that an electrical discharge, the corona discharge, develops between the springs .The gas is ionized due to corona discharge and large quantities of positive and negative ions are produced .the positive ions are attached to the negative springs due to the field.En route towards the steel curtains the ions collide with and adhere to the ash particles in the gas. The ash particles become electrically charged and migrate in the same direction as the ions towards the collecting electrodes and stick on to them. These electrodes are rapped periodically by hammers present on a rapping shaft, so as to dislodge the ash particles from the electrodes into the ash hoppers. From there, the ash is sent to the ash slurry pond through the ash handling plant.TG SECTION

HP, IP and LP turbine AssemblyTURBINE: It is a prime-mover which is used to convert the thermal energy possessed by the steam into kinetic energy of the blades of the turbine. This energy is then converted to electric power by a generator. Fluid (steam) at high pressure and temperature enters the turbine. It passes through stationery and rotary blades and looses it energy (by means of pressure and temperature) to the turbine rotor and turbine rotor rotates to rotate the generator. At the entrance pressure gets converted to velocity (partly) at stationery nozzle and in subsequent rotary stages pressure as well velocity drops while transferring the kinetic energy to the rotary blades. Stationery blade is responsible for guiding the steam and partial drop in pressure. The turbine is coupled with the rotor of the generator which rotates as the turbine blades rotate so as produce the power output.N.B. The set of turbines used at Andal site are of the Impulse Reaction type.CONTROL VALVES: The control valves at the entrance of the turbine controls the amount of steam entry to the turbine and in turn LOAD/SPEED. Stop valves before the control valves shuts off the steam entry in case of emergency which is called TRIPPING OF MACHINE. Operation: The control valves opening and closing is controlled by the demand of load / speed being generated in the governing system. This governing is electro-hydraulic. Valves operates with oil and comparison of signals are in electronic cards and coupling of these two is done by a solenoid coil and hydraulic amplifier.TURBINE TYPESHP TURBINE : This turbine is characterized by a small size and presence of a unidirectional increasing and rotating fixed blades. Since the steam passes over the turbine blades resulting in a corresponding decrease in pressure and enthalpy, the volume of the steam increases and hence, the blades are made continuously increasing in size. The blades are of aerofoil section, and are rimmed throughout their periphery so as to increase their strength. Here, the flow occurs in a single direction, and hence bearings are provided so as to balance the resultant axial and radial thrusts produced due to flow. The steam from this turbine goes back to the boiler for reheating via the cold reheat line. Steam is bled from this line for high pressure heating in the HP Heater. Also steam is bled from suitable points of this turbine for use in the DEAERATOR.IP TURBINE: This turbine is usually larger than the HP Turbines. Here the blades are placed in two parts in opposite direction, and hence the blades are bidirectional. The blades are continuously increasing in size in both directions. Here the steam after reheating in the boiler enters via the hot reheat line by two paths- one from the top and another from the bottom, at the centre of the turbine, and then divides symmetrically and expands in both the directions. This is done so as to balance the axial thrusts. The steam leaves by two paths and goes to the LP Turbines.LP TURBINE: This turbine is the biggest in size. Its blades are similar in construction and shape to that of the IP Turbine. Here the steam enters from two directions as well- but from the front and from the back, for the same purpose. The steam leaves by two paths, which unite into a common duct that leads to the CONDENSER. This turbine is coupled to the generator for electrical power production.

TG AUXILLIARIES

1. CONDENSER 2. CONDESATE EXTRACTION PUMP 3. EJECTOR 4. LP HEATER 5. HP HEATER 6. BOILER FEED PUMP 7. DEAERATOR CONDENSER: Condenser is basically a heat exchanger. Steam after moving through the turbine passes through the condenser. The use of a condenser enhances the efficiency of the power plant by reducing the exhaust pressure of steam below atmospheric pressure. The condenser basically condenses the exhaust steam into water. The use of condenser also helps in recycling of this condensed steam again & again as boiler feed water & this in turn reduces the capacity of the water softening plant. Air & other non-condensable gases present in the exhaust steam are also removed when this steam is passed through the condenser.Vacuum is maintained inside the condenser to extract maximum energy from steam as at lower pressure the heat lost is less. CONDENSATE EXTRACTION PUMP: The function of this pump is to extract the condensed steam from the condenser & deliver it to the ejector.

EJECTOR: It takes out the air & other non-condensable gases from the condenser & maintains the vacuum level in it. LP HEATER: Water coming out of the Ejector is heated at low pressure in the LP Heater. This heating is done by bleeding steam ata suitable point from the low pressure tu HP HEATER: Water coming out of the Deaerator is heated in the HP Heater at high pressure.

BOILER FEED PUMP: Feed water is delivered to the boiler with the help of boiler feed pump. There are two types of BFPs:1) MDBFP- Motor Driven boiler feed pumps. Here we have 2 such pumps. These pumps are used when the plant is not in full operation.2) TDBFP- Turbine Driven boiler feed pumps. Here we have a single such pump. It is used when the plant is in full running condition.Parts of a BFP:1) BOOSTER Pump2) Hydraulic Coupling3) Feed Pump

Working of BFP:Water with more than required NPSH goes to suction branch into the intake spiral and from here is directed to the first impeller. After leaving through the impeller it passes through the distributing passages of the diffuser where it gets certain pressure rise and flows over to guide vanes to the inlet of the next impeller.

Specification of BFP: Number of stages 6 Suction pressure 12.3ata Quantity of water for min. take off 100tons/hr Discharge capacity / head430ton/hr/1830MWC Quantity of water for warming up 8tons/hr Feed water temperature 164.20C Consumption of cooling water 280LPM Speed 4320rpm Lubrication Forced Stuffing box Mechanical Seal Net weight of pump 5850 k

COOLING WATER CYCLE

VARIOUS PARTS OF A CW CYCLE:1. CW PUMP AND PUMPHOUSE2. DUCTS3. HOTWELL4. NDCT(Natural Draught Cooling Towers)5. CW RESERVOIR

CW PUMPS AND PUMPHOUSE: The C.W. Pump house comprises mainly of three parts- a) Sump areab) Feed pool c) Duct area. The Sump is the most important area in the C.W. Pump house. Here 8 nos. chambers are constructed where CW pumps are placed. The water in these chambers will be pumped to condenser through C.W. conduits.The water from the cooling tower is conveyed into the feed pool through the CW duct. Water is stored in the feed pool and sump area.Apart from the 8 CW Pumps, we have two AUXILLIARY COOLING WATER Pumps( ACW Pumps),

DUCTS: Ducts are used to transmit the cooling water from the CW Feed pool or reservoir, to the condenser, and back from the hot well to the cooling towers,

HOTWELL: The cooling water, after heat exchange with the condensate in the condenser, collects in the hot well.

NDCT: The cooling water used to condense steam is pumped to the Natural Draft Cooling Tower (NDCT) for its own cooling, and recirculation. The shape of the NDCTs is so designed so as to ensure max rate of cooling by natural air. The steam rises in the cooling towers, thereby producing a vacuum which results in induction of cold natural air, and contact of the hot steam with this cold air results in its cooling. Sprinklers are provided so as to break the water droplets into smaller sizes at different elevations so as to produce max cooling. The height & water handling capacity of the cooling tower is determined by the amount of feed water. The height of the NDCTs at Andal site is 105m. This water is then pumped again to the feed water circuit. Some amount of water is always lost due to evaporation & has to be replenished by the tank.

COOLING WATER RESERVOIR: After cooling in the cooling towers, this cooling water is stored in the reservoir for recirculation as cooling water.

BALANCE OF PLANTBalance of plant includes-1. Refrigeration including AC2. Ventilation 3. Diesel Generation4. Battery system5. Compressed air system6. DM Plant7. Pre-treatment plant8. Fire fighting9. Cooling water system

1. REFRIGERATION:Refrigeration is the process of removing heat, and the practicalapplication is to produce or maintain temperatures below theambient.Refrigerants:The ideal properties of a suitable refrigerant are : A high latent heat of vaporization A high density of suction gas Non-corrosive, non-toxic and non-flammable Critical temperature and triple point outside the working range Compatibility with component materials and lubricating oil Reasonable working pressures (not too high, or below atmospheric pres

The Basic Refrigeration Cycle:

At the compressor, the refrigerant gets compressed to a high pressure gas. This high pressure gas then passes through the condenser where it ejects heat to the sink, and gets converted to a high pressure liquid. In the expansion valve, the high pressure liquid gets expanded at a constant enthalpy to a low pressure liquid and flash gas. This low pressure mixture is transmitted to the evaporator section where its temperature rises, and it moves to the suction side of the compressor, from where it moves back to the compressor a

AIR HANDLING UNIT:The main parts of an air handling unit are as follows:1) Fan 2) Air washer3) Planum chamber4) Water softening tank5) Cooling towers6) Chiller room

Functioning: The main purpose of the air handling unit is to supply cool air to the various offices and control panel rooms, removing the hot air present within them. The atmospheric air is at first inducted by the fan, from where it passes on to the air washer. In the air washer, plates and nozzles are present at the sides from where cooling water is sprayed onto the air, which cools as well as cleans the air. The air then passes through the planum chamber. The planum chamber has no function when we require the cool air in the rooms during the summer, but during the winter months when we require air at a temperature greater than the ambient for room heating, then in the air washer, air is cleaned only but no cooling water is sprayed. The air then goes onto the planum chamber where it is heated by means of heaters.The purified cool (or hot) air is then passed through the ducts to the diffuser plates in the room. The opening of the diffuser plates is controlled, thus permitting required amount of cool air into the room at desired temperature, and the subsequent hot air present, being lower in density, rises up and passes through the return line back to the fan, and in this way the cycle continues.

The water which becomes hot during cooling of air, is fed to the water softening tank so as to clean it as it contains the impurities of the air inducted through the fan. Then the water is fed into the cooling towers (5 in no) where it is cooled by forced draught mechanism. For further cooling, it then goes to the chiller room, where vapor absorption machine (VAM), chiller pumps, etc, are present, facilitating the cooling of the water, which is the refrigerant here. The water is the channeled back to the air washer.

VAPOUR ABSORPTION CYCLE:

Absorption refrigeration systems involve the absorption of a refrigerant by a transport medium. The most widely used absorption refrigeration system is the ammoniawater system, where ammonia (NH3) serves as the refrigerant and water (H2O) as the transport medium. Other absorption refrigeration systems include waterlithium bromide and waterlithium chloride systems, where water serves as the refrigerant. The latter two systems are limited to applications such as air-conditioning where the minimum temperature is above the freezing point of water. To understand the basic principles involved in absorption refrigeration, the NH3-H2O system shown in the figure is examined. The ammoniawater refrigeration machine was patented by the Frenchman Ferdinand Carre in 1859. Within a few years, the machines based on this principle were being built in the United States primarily to make ice and store food. You will immediately notice from the figure that this system looks very much like the vapor-compression system, except that the compressor has been replaced by a complex absorption mechanism consisting of an absorber, a pump, a generator, a regenerator, a valve, and a rectifier. Once the pressure of NH3 is raised by the components in the box (this is the only thing they are set up to do), it is cooled and condensed in the condenser by rejecting heat to the surroundings, is throttled to the evaporator pressure, and absorbs heat from the refrigerated space as it flows through the evaporator. So, there is nothing new there. Here is what happens in the box:

Ammonia vapor leaves the evaporator and enters the absorber, where it dissolves and reacts with water to form NH3 H2O. This is an exothermic reaction; thus heat is released during this process. The amount of NH3 that can be dissolved in H2O is inversely proportional to the temperature. Therefore, it is necessary to cool the absorber to maintain its temperature as low as possible, hence to maximize the amount of NH3 dissolved in water. The liquid NH3 _ H2O solution, which is rich in NH3, is then pumped to the generator. Heat is transferred to the solution from a source to vaporize some of the solution. The vapor, which is rich in NH3, passes through a rectifier, which separates the water and returns it to the generator. The high-pressure pure NH3 vapor then continues its journey through the rest of the cycle. Thehot NH3 _ H2O solution, which is weak in NH3, then passes through a regenerator, where it transfers some heat to the rich solution leaving the pump, and is throttled to the absorber pressure.

2. THE VENTILATION SYSTEM It is separate for each unit. It serves the TG hall, MCC, switch gear room, etc. Other offside plant and other buildings, which are not connected with main ventilation system, are provided with ventilation fans of adequate numbers. The Ventilation System is open cycle unlike the Air conditioning cycle. It is not economically feasible to provide air conditioning everywhere, so ventilation is required.

3. DIESEL GENERATORIn load shedding condition, the diesel generator will keep the plant working by supplying power when plant power line and power line from the grid are tripped . These generators are operated on diesel. There are three diesel generators, with two running and one in standby condition.4. BATTERY SYSTEMWhen diesel generator, power line from the grid and plant power line are all tripped charged batteries are kept in battery room from which power is used for only some important drives.5. COMPRESSED AIR SYSTEMIn the compressor house, different compressors are present so as to provide compressed air to required parts of the power plant. This compressor house along with the compressors constitutes the compressed air system. There are two types of compressed air :1) Instrumentation air2) Secondary airInstrumentation air is the compressed air which is free from moisture, and this air is produced by the compressors having a drier unit installed in them so as to remove the moisture. This air is generally supplied to the PA fan and FD fan. For this purpose, we have 3 such compressors.Secondary air is the compressed air in which moisture is present and so the compressors producing them dont have any drier units installed in them. For this purpose, we have 2 such compressors.6.DM PLANTThe water that is circulated in the boilers is essentially de-mineralized water (DM water). DM water is used because it is free from minerals which would have caused scale formation and corrosion in the different boiler parts.7.PRE-TREATMENT PLANTThe water that is present in the cooling water circuit is pre-treated in the pre-treatment plant so as to remove the impurities before it is circulated.8.FIRE FIGHTINGEach Fire Extinguisher displays the letter of the class of fire it is designed to put out. It also indicates a numerical stating the size of the fire it can put out. On seeing a fire we should first of all activate the alarm, assist any person in danger and try to extinguish the fire. We should fight a fire only if it is small & contained and we are safe from toxic smokes. We should also see that there is a proper escape route. Otherwise we should leave immediately.9.COOLING WATER SYSTEMTHIS HAS ALREADY BEEN DISCUSSED IN TG SECTION.

ELECTRICAL PACKAGEMAIN PARTS OF TURBOGENERATOR Stator Stator Frame (Fabrication & Machining) Core Assembly - Stator Core, Core suspension Arrangement End Seals Stator winding Assembly- Stator winding, winding assembly, connecting bus-bars Rotor- rotor shaft, rotor wedges, rotor coils, wound rotor, rotor assembly Completing assembly- Bearing assembly, shaft seal assembly, oil catchers, insert covers, etc Auxiliary system ExciterEXCITATION SYSTEM:Static ExcitationRotor field winding is connected to slip ring mounted on rotor.Excitation is provided by current transfer by contact through carbon brushes, slip ring and field lead.AUXILLIARY SYSTEM:Primary water systemDissipation of losses in stator winding, bushings, bus-bar.Seal oil systemPrevents H2 losses at the shaft entry into the stator.Gas flow systemFacilitates H2 filling and maintains gas pressure in the stator.N.B.- The Generators are hydrogen cooled where the hydrogen is circulated in a closed circuit by two axial flow fans arranged on the rotor shaft journals. Cold gas is drawn by the fans from the cooler compartments. The cooling gas flow is divided into three flow paths.

SPECIFICATION OF 500MW TURBOGENERATOR Rating - 500 MW Output Voltage- 21 KV Phase- 3 phase Power Factor- 0.85 Inductive Reactance- 17.19% No of poles- 2 Speed- 120f/p= 120x50/2= 3000 rpm N.B. It has brushless excitation.

TRANSFORMERSDepending upon the system design, the power transformers are classified as follows:1) GENERATOR TRANSFORMERS- There are three generator transformers used in each unit.Specification:a. Phase- singleb. No of transformers- 3c. Type- Step-up transformers(21KV/400KV)d. Connection Type- Delta-stare. Rating- 200 MVA. HV sides 440 KV. LV side is 21 KV. 2) STATION TRANSFORMER- Specification:a. Phase 3b. No of transformers- 2c. Type- Step-down(400KV/11.5KV)d. Rating- 90/45 MVA 3) UNIT TRANSFORMER- Specification:a. Type- Step-down(21.5 KV/11KV)b. Rating- 25 MVA4) UNIT AUXILIARY TRANSFORMER-Specification:a. Type - Step-down (11 KV/3.3 KV), dry type.b. Rating 16 MVAc. No of transformers- 25) DISTRIBUTION TRANSFORMER-Specification:a) Type- Step-down(11 KV/ 0.433 KV)b) Rating- 2000KVAc) Current rating- 2500 A(max)6) CURRENT TRANSFORMER- The current transformers are used for metering and protection differential and restricted earth protection (REF).7) POTENTIAL TRANSFORMER- The potential transformers are used in metering and protection purpose. We can also measure voltage by this type. This is also called Capacitor Voltage Transformer (CVT).8) AUXILLIARY TRANSFORMERS -a) Station service transformersb) Ash handling transformersc) DM and CW service transformers.d) Fuel-oil pump house transformers.e) Vacuum pump house transformers. f) Ash slurry transformers. g) Service building or compressor house transformers. h) Workshop or hydro plant service transformers. i) Fire water transformers. j) Ash water recirculation transformers. k) Raw water transformers.l) Make-up water transformers.m) Water treatment plant transformers.n) Coal handling plant track hopper transformer.

MOTORS11 KV MOTORS: Are connected with:1) PA fan 2) ID fan3) CW Pump4) MDBFP (Motor Driven Boiler Feed Pump)5) FD fan3.3 KV MOTORS: Are connected with:1) CEP (condensate extracting pump) 2) Bowl Mills3) Boiler Cooling Water4) Service Air Compressor5) IA Compressor6) Auxiliary Cooling Water.7) De-mineralized cooling water turbo generator.8) De-mineralized cooling water service generator.9) HP water pump10) Conveying water pump.11) Slurry di DIESEL GENERATORSIn load shedding condition, the diesel generator will keep the plant working by supplying power. These generators are operated on diesel. There are three diesel generators, with two running and one in standby condition.Specification:1) Phase- 3 Phase2) Rating- 1500 KVA3) Power factor- 0.84) Output voltage- 415 V5) Power- 3W6) Frequency- 50 HzVARIABLE FREQUENCY DRIVEVFDs are used in ID fans to control the speed of rotation of the fan blades, and hence the speed and amount of the discharge through the chimney.Various areas of application:1) Fans2) Pumps 3) Compressors 4) Stbreakers, hence the name.SAFETYIndustrial safety can generally be divided into two parts.1. Electrical Safety2. Fire Prevention and Safety

ELECTRICAL SAFETYElectric shock and its aftermath: When the body becomes a part of the electric circuit which is closed (contact with wires, wires and ground). Electric shock is affected by the current, its path and length of time it is in the body. Voltage, presence of moisture in the body and phase of the heart cycle also affects the severity of electric shock. Slight current such as 1mA may cause tingling sensations whereas 6mA-30 mA can be quite painful for the muscles. Muscular contraction and resulting death is very likely for a current of about 1A-4.3 A. Low and high voltages are equally dangerous for the human body. Lower voltages for longer periods of time (100 mA) can cause muscular fibrillation whereas higher voltages break down human skin. Electric shock can cause electric burns, internal injuries and involuntary muscle contractions. Injuries are less severe if the current does not pass through vital organs or major nerve centre. Electric shock results from Contact with live parts. Lack of ground fault protection. Path to ground missing or discontinuous. Equipment not used properly. Improper use of extension cables.

Dos in case of Electrical accidents: In case of electrical fires we should switch off the main power source, use only dry type fire extinguishers (no water) ,call the local fire brigade. In case of electrical shocks we should not touch the affected person (as he may still be in the circuit).Switch off the power and call for help. When it is ensured that the person is not in contact with electricity we should give him first aid(CPR-cardiopulmonary resuscitation).CPR is a life saving technique during many emergencies such as cardiac arrest.

FIRE PREVENTION AND SAFETY Fire is a chemical reaction involving burning or oxidation of combustibles. It requires four elements fuel, O2 ,heat and chemical reactionFuel+ O2 + heat =FireThree of them form the apex of a fire triangle, removing any one of them will nullify the triangle.

Classification of fires:Class A: Caused by ordinary combustibles such as wood, paper, cloth. Hence we should keep the work area clean, prevent storing combustibles near the construction area and keep them away from flame producing sources.Class B: Caused by combustible gases and liquids such as gasoline, paint .Keep them in sealed and spill proof containers and ply them away from spark producing sources .Use them only in well ventilated areas.Class C: Caused by electrical appliances, panel boxes and switches. Check electrical insulation in equipments, prevent motors from overheating and investigate any unusual odour.Class D: Caused by combustible metals such as Mg, K & Ti which burn at high temperatures.Types of fire extinguishers:Foam: Foam F.Es separate the oxygen element from other elements. Avoid these on electrical fires (due to shock hazards) and they can be used for A & B fires only.Water: Kill fires by removing the heat element from fire triangle. Can be used for class A fires only (not B & C associated shock hazards and spreading of the flammable liquid).CO2: Separates the oxygen element from other elements with a cold discharge. Can be used in B & C fires (ineffective in case of A fires)Dry chemical: Interrupts the chemical reaction of the fire triangle, used for B & C fires only.Dry powder: Separates the fuel element from the other elements and extinguishes the fire. Effective only for Class D fires. Fire Fighting: Each Fire Extinguisher displays the letter of the class of fire it is designed to put out. It also indicates a numerical stating the size of the fire it can put out. On seeing a fire we should first of all activate the alarm, assist any person in danger and try to extinguish the fire. We should fight a fire only if it is small & contained and we are safe from toxic smokes. We should also see that there is a proper escape route. Otherwise we should leave immediately.ABOVE ALL:Safety is not only the responsibility of the safety officials but each and every one associated with the organization. Every organization should have its own safety plan which has to implement properly. Workers working in dangerous environments should be provided with PPEs (personal protective equipments) such as goggles, helmets, ear buds, rope harnesses, lifelines, foot protection devices.

QUALITY & INSPECTIONQuality means a totality of characteristics of an entity that bear on its ability to satisfy stated and implied needs. Quality is referred to as,- fitness for use, fitness for purpose, customer satisfaction or conformance to the requirements. To achieve satisfactory quality we must concern all stages of the product or service cycle. In the first stage quality is due to a definition of needs. In the second stage it is due to product design and conformance. In the last stage quality is due to product support throughout its lifetime. There are basically 4 main quality system documents used in BHEL which are:1. QUALITY MANUAL2. STANDARD PROCEDURE3. DEPARTMENTAL PROCEDURE4. WORK INSTRUCTION There are various other documents maintained by us and those are the guidelines for keeping Quality as our supreme motto which covers every aspects of power plant such as Welding Manual ,Heat Treatment Manual ,NDE Manual, Welding Procedure Specification, Recommended Hydrostatic Test Procedure ,etc.

FINANCEFinancial statements provide an overview of a business' financial condition in both short and long term. There are three basic financial statements:

Balance sheet: It is a summary of a person's or organization's balances.

Income statement: Indicates how Revenue money is transformed into net income , to show whether the company made or lost money during the period being reported.

Statement of cash flows: Reports on a company's cash flow activities, particularly its operating, investing and financing activities.

For large corporations, these statements are often complex and may include an extensive set of notes to the financial statements and management discussion and analysis. The notes typically describe each item on the balance sheet, income statement and cash flow statement in further detail.

CONCLUSIONDuring my short tenure in DSTPS, Andal I gathered a lot of experience in power plant engineering. When I first entered this plant I was simply dumbfounded by the sheer enormity of the boilers and turbines. The labyrinth air ducts and coal pipes were beyond our comprehension. But slowly with several plant visits I got to understand the working of the power plant. I got to know about the different parts of the boiler such as burners, oil-guns, furnace walls etc. I also got to see the turbine blades, multistaging of turbines. This has truly been an enriching experience which will last with me forever and help me to be better engineers in the future.