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Working of steam turbines and its auxillaries

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A power plant can be roughly divided into 3 parts. Furnace boiler, Turbine which includes condenser pump, feed water heater, and rejection system and the electric generator. Steam from furnace is …

A power plant can be roughly divided into 3 parts. Furnace boiler, Turbine which includes condenser pump, feed water heater, and rejection system and the electric generator. Steam from furnace is supplied in which K.E of steam is used to drive the turbine to obtain Mechanical Energy. Study of Steam turbine which is capable of generating power with its auxiliaries is studied in this study.

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  • 1. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES WORKING OF STEAM TURBINE AND ITS AUXILIARIES - INDEX Abstract 1 CHAPTER 1 Introduction to Steam Turbine 5 1.1 Definitions of Steam turbine 5 1.2 Principle of Operation 5 1.3 Classification of Steam Turbines 5 1.4 Basic types of turbine 6 1.4.1 The Impulse Turbine 6 1.4.2 The Reaction Turbine 8 1.5 Steam Turbine Applications 9 CHAPTER 2 Steam Turbine Parts 11 CHAPTER 3 Construction and Steam Flow 14 CHAPTER 4 Normal Working Condition 21 CHAPTER 5 Specifications of Steam Turbine 23 CHAPTER 6 Turbine Auxiliaries 6.1 Turbine Governing System 27 6.2 Vacuum System 29 6.3 Condensate System 31 6.4 Feed Water System 36 6.5 Cooling Water System 41 6.6 Lubrication Oil System 42 Conclusion 47 Bibilography 48 1 DEPARTMENT OF MECHANICAL ENGINEERING
  • 2. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES List of Figures Page No. Fig(a) Diagram of a typical coal-fired thermal power station. 3 Fig.1.4.1 Diagram of a Impulse Turbine 7 Fig.1.4.2 Diagram of a Reaction Turbine 8 Fig.2.1 Diagram showing Parts of Steam Turbine 11 Fig:2.2 Outer & Inner casing of Steam turbine 12 Fig:2.3 Oil system 13 Fig.2.4 Pipes 13 Fig.3.1 HP Turbine 15 Fig.3.2 Sectional view of HP Turbine 15 Fig.3.3 IP Turbine 16 Fig.3.4 LP Turbine with Shaft 17 Fig.3.5 Turbine & Generator System in Steam Power Plant 17 Fig.3.6 Main and Thrust Bearings:(a)main bearing;(b)section of thrust bearing and housing;(c)thrust bearing cage in place 18 Fig:4.1 Diagram showing Working of Steam turbine 21 Fig:6.2 Condenser 29 Fig:6.2.1 Ejector 30 Fig:6.3 Condensate Extraction Pump 31 Fig:6.3.1 Deareator 33 Fig:6.3.2 Circuit diagram of Condenser Connections 34 Fig:6.3.3 Circuit diagram of Condensate System Connections 35 Fig:6.4 Turbine Driven Boiler Feed Pump 36 Fig:6.4.1 HP Heater 38 Fig:6.4.2 Circuit Diagram of Turbine Driven Boiler Feed Pump 39 Fig:6.5 Cooling towers 41 Fig:6.6 Turbine Lube Oil System 44 Fig:6.6.1 Steam Turbine flow Diagram Showing Auxiliaries 46 2 DEPARTMENT OF MECHANICAL ENGINEERING
  • 3. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES ABSTRACT A power plant can be roughly divided into 3 parts. Furnace boiler, Turbine which includes condenser pump, feed water heater, and rejection system and the electric generator. Steam from furnace is supplied in which K.E of steam is used to drive the turbine to obtain Mechanical Energy. Study of Steam turbine which is capable of generating power with its auxiliaries is studied in this project. 3 DEPARTMENT OF MECHANICAL ENGINEERING
  • 4. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES INTRODUCTION TO THE FUNCTIONING OF A POWER PLANT (a)Diagram of a typical coal-fired thermal power station Key 1. Cooling tower 10. Steam governor valve 19. Superheater 2. Cooling water pump 11. High pressure turbine 20. Forced draught fan 3. Transmission line (3-phase) 12. Deaerator 21. Reheater 4 DEPARTMENT OF MECHANICAL ENGINEERING
  • 5. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES 4. Unit transformer (3-phase) 13. Feed heater 22. Air intake 5. Electric generator (3-phase) 14. Coal conveyor 23. Economiser 6. Low pressure turbine 15. Coal hopper 24. Air preheater 7. Boiler feed pump 16. Pulverised fuel mill 25. Precipitator 8. Condensor 17. Boiler drum 26. Induced draught fan 9. Intermediate pressure turbine 18. Ash hopper 27. Chimney Stack Description:- . 1. Coal is conveyed (14) from an external stack and ground to a very fine powder by large metal spheres in the pulverized fuel mill (16). 2. There it is mixed with preheated air (24) driven by the forced draught fan (20). 3. The hot air-fuel mixture is forced at high pressure into the boiler where it rapidly ignites. 4. Water of a high purity flows vertically up the tube-lined walls of the boiler, where it turns into steam, and is passed to the boiler drum, where steam is separated from any remaining water. 5. The steam passes through a manifold in the roof of the drum into the pendant superheater (19) where its temperature and pressure increase rapidly to around 200 bar and 570°C, sufficient to make the tube walls glow a dull red. 6. The steam is piped to the high-pressure turbine (11), the first of a three-stage turbine process. 7. A steam governor valve (10) allows for both manual control of the turbine and automatic set point following. 8. The steam is exhausted from the high-pressure turbine, and reduced in both pressure and temperature, is returned to the boiler reheater (21). 9. The reheated steam is then passed to the intermediate pressure turbine (9), and from there passed directly to the low pressure turbine set (6). 10. The exiting steam, now a little above its boiling point, is brought into thermal contact with cold water (pumped in from the cooling tower) in the condensor (8), where it condenses rapidly back into water, creating near vacuum-like conditions inside the condensor chest. 11. The condensed water is then passed by a feed pump (7) through a deaerator (12), and prewarmed, first in a feed heater (13) powered by steam drawn from the high pressure set, and then in the economiser (23), before being returned to the boiler drum. 12. The cooling water from the condensor is sprayed inside a cooling tower (1), creating a highly visible plume of water vapor, before being pumped back to the condensor (8) in cooling water cycle. 13. The three turbine sets are coupled on the same shaft as the three-phase electrical generator (5) which generates an intermediate level voltage (typically 20-25 kV). 14. This is stepped up by the unit transformer (4) to a voltage more suitable for transmission (typically 250-500 kV) and is sent out onto the three-phase transmission system (3). 15. Exhaust gas from the boiler is drawn by the induced draft fan (26) through an electrostatic precipitator (25) and is then vented through the chimney stack (27). 5 DEPARTMENT OF MECHANICAL ENGINEERING
  • 6. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES 1. INTRODUCTION TO STEAM TURBINE A steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and converts it into rotary motion. Its modern manifestation was invented by Sir Charles Parsons in 1884. 1.1 Definitions of Steam turbine: • Turbine in which steam strikes blades and makes them turn. • A system of angled and shaped blades arranged on a rotor through which steam is passed to generate rotational energy. Today, normally used in power stations • A device for converting energy of high-pressure steam (produced in a boiler) into mechanical power which can then be used to generate electricity. • Equipment unit flown through by steam, used to convert the energy of the steam into rotational energy. 1.2 Principle of Operation: In reciprocating steam engine, the pressure of energy of steam is used to overcome external resistance and dynamic action of the steam is negligibly small. Steam engine may be return by using the full pressure without any expansion or drop of pressure in the cylinder. The steam energy is converted mechanical work by expansion through the turbine. The expansion takes place through a series of fixed blades (nozzles) and moving blades each row of fixed blades and moving blades is called a stage. The moving blades rotate on the central turbine rotor and the fixed blades are concentrically arranged within the circular turbine casing which is substantially designed to withstand the steam pressure. 1.3 Classification of Steam Turbines 6 DEPARTMENT OF MECHANICAL ENGINEERING
  • 7. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES The first steam turbine, at its time indeed did spark off the industrial revolution through out the west. However, the turbine at that time was still an inefficient piece of heavy weighing high maintenance machine. The power to weight ratio of the first reciprocating steam turbine was extremely low, and this led to a great focus improving the design, efficiency and usability of the basic steam turbine, the result of which are the power horses that currently produce more than 80% of today’s electricity at power plants! Steam Turbines are Classified as:- Steam Turbines can be classified on the basis of a number of factors. Some of the important methods of steam turbine classification are enunciated below:  On the basis of Stage Design: Steam turbines use different stages to achieve their ultimate power conversion goal. Depending on the stages used by a particular turbine, it is classified as Impulse Turbine, or Reaction type.  On the Basis of the Arrangement of its Main Shaft: Depending on the shaft arrangement of the steam turbine, they may be classified as Single housing (casing), tandem compound (two or more housings, with shafts that are coupled in line with each other) and Cross compound turbines (the shafts here are not in line).  On the Basis of Supply of Steam and Steam Exhaust Condition: They may be classified as Condensing, Non Condensing, Controlled or Automatic extraction type, Reheat (the steam is bypassed at an intermediate level, reheated and sent again) and Mixed pressure steam turbines (they have more than one source of steam at different pressures).  On the basis of Direction of Steam Flow: They may be axial, radial or tangential flow steam turbines.  On the Basis of Steam Supply: Superheated steam turbine or saturated steam turbine. 1.4 Basic types of turbine The two most basic and fundamental types of steam turbines are the impulse turbine and the impulse reaction turbine. 7 DEPARTMENT OF MECHANICAL ENGINEERING
  • 8. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES 1.4.1 The Impulse Turbine: The impulse turbine consists of a set of stationary blades followed by a set of rotor blades which rotate to produce the rotary power. The high pressure steam flows through the fixed blades, which are nothing but nozzles, and undergo a decrease in pressure energy, which is converted to kinetic energy to give the steam high velocity levels. This high velocity steam strikes the moving blades or rotor and causes them to rotate. The fixed blades do not completely convert all the pressure energy of the steam to kinetic energy, hence there is some residual pressure energy associated with the steam on exit. Therefore the efficiency of this turbine is very limited as compared to the next turbine we are going to review- the reaction turbine or impulse reaction turbine. Fig.1.4.1 Diagram of a Impulse Turbine Working of Impulse Turbine:- The impulse turbine was one of the basic steam turbines. It involved striking of the blades by a stream or a jet of high pressure steam, which caused the blades of the turbine to rotate. The direction of the jet was perpendicular to the axis of the blade. It was realized that the impulse turbine was not very efficient and required high pressures, which is also quite difficult to maintain. The impulse turbine has nozzles that are fixed to convert the steam to high pressure steam before letting it strike the blades. Impulse turbine mechanism: 8 DEPARTMENT OF MECHANICAL ENGINEERING
  • 9. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES Impulse turbine Mechanism deals with the Impulse force action-reaction. As we all know the Newton 3rd law of motion," Every action has equal and opposite reaction", the same is work on this. As the water fall on the blade of the rotor it generate the impact force on the blade surface, The blade tends to give the same reaction to the fluid, but the rotor is attached to the rotating assembly, it absorb the force impact and give the reaction in the direction of the fluid flow. Thus the whole turbine rotates. The rotation speed of the turbine depends on the fluid velocity, more the fluid velocity, greater the rotation speed, and greater the speed means more power generation. 1.4.2 The Reaction Turbine The reaction turbine is a turbine that makes use of both the impulse and the reaction of the steam to produce the rotary effect on the rotors. The moving blades or the rotors here are also nozzle shaped (They are aerodynamically designed for this) and hence there is a drop in pressure while moving through the rotor as well. Therefore in this turbine the pressure drops occur not only in the fixed blades, but a further pressure drop occurs in the rotor stage as well. This is the reason why this turbine is more efficient as the exit pressure of the steam is lesser, and the conversion is more. The velocity drop between the fixed blades and moving blades is almost zero, and the main velocity drop occurs only in the rotor stage. Fig.1.4.2 Diagram of a Reaction Turbine WORKING OF REACTION TURBINE: In the reaction turbine, the rotor blades themselves are arranged to form convergent nozzle Reaction Turbines. 9 DEPARTMENT OF MECHANICAL ENGINEERING
  • 10. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES In the reaction turbine, the rotor blades themselves are arranged to form convergent nozzles. This type of turbine makes use of the reaction force produced as the steam accelerates through the nozzles formed by the rotor. Steam is directed onto the rotor by the fixed vanes of the stator. It leaves the stator as a jet that fills the entire circumference of the rotor. The steam then changes direction and increases its speed relative to the speed of the blades. A pressure drop occurs across both the stator and the rotor, with steam accelerating through the stator and decelerating through the rotor, with no net change in steam velocity across the stage but with a decrease in both pressure and temperature, reflecting the work performed in the driving of the rotor. This type of turbine makes use of the reaction force produced as the steam accelerates through the nozzles formed by the rotor. Steam is directed onto the rotor by the fixed vanes of the stator. It leaves the stator as a jet that fills the entire circumference of the rotor. The steam then changes direction and increases its speed relative to the speed of the blades. A pressure drop occurs across both the stator and the rotor, with steam accelerating through the stator and decelerating through the rotor, with no net change in steam velocity across the stage but with a decrease in both pressure and temperature, reflecting the work performed in the driving of the rotor. 1.5 Steam Turbine Applications The Steam turbines of today are mostly used in the power production field. Steam turbines are used to efficiently produce electricity from solar, coal and nuclear power plants owing to the harmlessness of its working fluid, water/steam, and its wide availability. Modern steam turbines have come a long way in increasing efficiency in performance and more and more efforts are being made to try and reach the ideal steam turbine conditions, though this is physically impossible! Almost every power plant in the world, other than hydro electric power plants, that use turbines that run on water (the Francis, Pelton turbines also have the influence of steam turbines) , use steam turbines for power conversion. With all the scientific advancement in power generation being attributed to them, steam turbines really have changed the way the world moves! Steam turbines are devices which convert the energy stored in steam into rotational mechanical energy. These machines are widely used for the generation of electricity Utility Steam Turbine Applications: Applications for utility Steam Turbines are applied for control of straight condensing, reheat and non-reheat steam turbines up to 300MW. These upgrades may include integrated generator control for generator protection and excitation/ AVR upgrades, utilizing the latest commonly available industry-standard digital equipment. Industrial application of steam turbine: 10 DEPARTMENT OF MECHANICAL ENGINEERING
  • 11. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES Applications of Industrial Steam Turbines cover all straight condensing, non-condensing, and automatic extraction steam turbines. Specific design features are incorporated to address control issues often unique to process plants including paper mills, oil refineries, chemical plants, and other industrial applications, generator and mechanical drive. Some of the world’s largest turbines manufacturing companies that are seeing the rewards of research and steam turbine advances are coming together to develop highly efficient turbines. The collaboration of Mitsubishi Heavy Machinery and General Electric Energy (GE Energy) for the conceptualization and design of a highly efficient “next- generation” steam turbine for its inception in combined cycle gas turbine power plants recently has further proved that there is still a lot to be achieved in steam turbine related research and development, and that the scope for improvement can be much higher. 11 DEPARTMENT OF MECHANICAL ENGINEERING
  • 12. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES CHAPTER 2 Steam Turbine Parts Steam turbines are machines that are used to generate mechanical (rotational motion) power from the pressure energy of steam. Steam turbines are the most popular power generating devices used in the power plant industry primarily because of the high availability of water, moderate boiling point, cheap nature and mild reacting properties. The most widely used and powerful turbines of today are those that run on steam. From nuclear reactors to thermal power plants, the role of the steam turbine is both pivotal and result determining. A steam turbine basically has a mechanical side, and an electrical side to it. The mechanical components include the moving parts (mechanical), such as the rotor, the moving blades, the fixed blades, and stop valves, while the electrical side consists of the generator and other electrical components to actually convert the energy into a usable, easily transferable form. Blades: For starters, a simple turbine works just like a windmill. Only, in the steam turbines of today, rather than striking the blades directly, the blades are designed in such a way as to produce maximum rotational energy by directing the flow of the steam along its surface. So the primary component that goes into a steam turbine is its blades. The blades of a steam turbine are designed to behave like nozzles, thus effectively tapping both the impulse and reaction force of the steam for higher efficiency. Nozzle design itself is a complex process, and the nozzle shaped blade of the turbine is probably one of the most important parts in its construction. The blades are made at specific angles in order to incorporate the net flow of steam over it in its favor. The blades may be of stationary or fixed and rotary or moving or types. Fig.2.1 Diagram showing Parts of Steam Turbine 12 DEPARTMENT OF MECHANICAL ENGINEERING
  • 13. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES Shafts: The shaft is a power transmitting device and is used to transmit the rotational movement of the blades connected to it at one end via the rotor to the coupling, speed reducer or gear at the other end. Outer Casing: The steam turbine is surrounded by housing or an outer casing which contains the turbine and protects the device components from external influence and damage. It may also support the bearings on which the shafts rest to provide rigidity to the shaft. Usually split at the center horizontally, the casing parts are often bolted together for easy opening, checking and steam turbine maintenance, and are extremely sturdy and strong. Fig:2.2 Outer & Inner casing of Steam turbine. Governor: The governor is a device used to regulate and control or govern the output of the steam turbine. This is done by means of control valves which control the steam flow into the turbine in the first place. Oil System: A steam turbine has thousands of moving parts and all these parts not only have to move in high velocities, but also need to be protected from wear and tear over the years. This is 13 DEPARTMENT OF MECHANICAL ENGINEERING
  • 14. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES done by effective lubrication by the oil system, which governs the pressure, flow and temperature of the turbine oil, the bearing oil and lubrication of other moving parts. Fig:2.3 Oil system Pipes: The pipe is an all important steam turbine component that brings the steam from the boiler to the turbine. This has to be done without an appreciable loss in pressure, and at the same time, must be able to withstand all these pressures safely. The pipes should be easy to clean and are prone to deposits on their inner surfaces. Deposits on the inner surface of the steam pipe reduce the net steam flow area, throwing forth a negative effect on the efficiency. Fig.2.4 Pipes 14 DEPARTMENT OF MECHANICAL ENGINEERING
  • 15. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES CHAPTER 3 CONSTRUCTION & STEAM FLOW The turbine is a single shaft machine with separate HP and LP parts, the HP part being a single flow, the IP and IP parts double flow cylinders. Ring couplings connect the individual turbine rotors and the generator rotor. The HP cylinder has a throttle control. The initial steam admitted before the blading by four combined main steam stop and control valves. The lines leading from the two HP exhaust branches to the reheated are provided with swing check valves which prevent hot steam from the reheater flowing back into the HP turbine. The steam coming from the reheater is passed to the IP part via four combined reheats stop and control valves. Crossover pipes connect the IP and LP cylinders. HP TURBINE, BARREL TYPE CASING: The outer casing of the HP turbine is of the barrel type and has neither an axial nor a radial flange. This prevents mass accumulation with high thermal stresses. The almost perfect rotational symmetry permits moderate wall thickness of nearly equal strength at all sections. The guide blade carrier is axially split and kinematically supported. As only slight pressure differences are effective, the horizontal flange and connection bolts can be kept small. The barrel type casing permits flexibility of operation in the form of short startup times and a high rate of change of load even at high initial steam conditions. 15 DEPARTMENT OF MECHANICAL ENGINEERING
  • 16. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES Fig.3.1 HP TURBINE Fig.3.2 SECTIONAL VIEW OF HP TURBINE 16 DEPARTMENT OF MECHANICAL ENGINEERING
  • 17. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES IP TURBINE: The IP turbine part is double flow construction. Attached in the axially split casing is an inner casing supported kinematically and taking the guide blades. The reheated steam is admitted to the inner casing through the top and bottom center of the casing. The arrangement of an inner casing confines the high steam inlet conditions to the admission branch of the casing, while the joint of the outer casing is only subjected to the lower pressure and lower temperature at the exhaust of the inner casing. Fig.3.3 IP TURBINE LP TURBINE: The casing of the double flow IP cylinder is of three shell design. The shells are axially split and have rigid welded construction. The inner shell taking the first rows of the guide blades is attached kinematically in the middle shelf. Independent of the outer shell, the middle shell is supported at four points on longitudinal beams. Two rings carrying them last guide blade rows are also attached to the middle shelf. 17 DEPARTMENT OF MECHANICAL ENGINEERING
  • 18. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES Fig.3.4 LP TURBINE WITH SHAFT Fig.3.5 TURBINE & GENERATOR SYSTEM IN STEAM POWER PLANT BLADING: The entire turbine is provided with reaction blading. The guide blades of the LP parts with inverted T-roots and shrouding are milled from one piece. The last stages of the IP part consists of twisted drop forged moving blades with fir-tree roots inserted in corresponding grooves of the rotor and guide blade rows made of sheet steel. 18 DEPARTMENT OF MECHANICAL ENGINEERING
  • 19. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES BEARINGS: Fig.3.6 Main and Thrust Bearings:(a)main bearing;(b)section of thrust bearing and housing; (c)thrust bearing cage in place The HP rotor is supported by two bearings, the journal bearing at the front end of the turbine and a combined journal and thrust bearing directly adjacent to the coupling with the IP rotor. The IP and LP rotors having journal and thrust bearing incorporates a journal hearing and thrust bearing which takes up residual thrust from both directions. The bearing temperatures are measured by thermocouples in the lower shell directly under the white metal lining. The temperature of the thrust bearing is measured in two opposite thrust pads. The front rear bearing pedestals of the HP turbine is placed on base plates. The pedestals of the LP part are fixed in position, the front pedestals of the LP part are fixed in position, the front pedestal and the pedestal between HP and IP part are able to move in axial direction. The brackets at the sides of the HP and IP parts are supported by the pedestals at the level of the machine axial. In the axial direction of the HP and IP parts are firmly connected with the pedestal by means of casing guided without restricting radial expansion. Since the casing guide do not yield response to axial displacement, the HP and IP casings as well as associated bearings pedestals move forward from the front LP bearing pedestal on thermal expansion. Journal bearings are manufactured in two halves and usually consist bearing body faced with anti-friction tin based babbling to decrease coefficient of friction. Bearing body match with adjustable seating assembly in the pedestal. Bearings are usually forced lubricated and have provision for admission of jacking oil. 19 DEPARTMENT OF MECHANICAL ENGINEERING
  • 20. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES The thrust bearing is normally Mitchel type and is usually combined with a journal bearing, horsed in spherically machined steel shell. The bearing between the HP and IP rotors is of this type; while the rest are journal bearings. Earlier each rotor used to have its own set of bearings. Not with the popularity of rigid coupling between rotors, it is possible to use only on bearings between two rotors. This arrangement will lead to more flexible rotors (lower critical speed), for the same rotor design because span between bearings increases. With reduction in number of bearings, length of turbine gets reduced resulting in consideration saving in capital cost. SHAFT GLANDS AND BLADE SEALING STRIPS: All shaft glands sealing the steam in the cylinders against atmosphere are axial flow labyrinths. They consist of a large number of thin sealing strips which in the HP and IP parts are alternate caulked into grooves in the shafts and surrounding sealing rings. The sealing strips of the LP parts are only caulked into the sealing rings. These rings are split into segments, which are forced radially against a projection by helical springs and are able to yield in the event of rubbing. Sealing strips of similar design are also used to seal the radial blade strip clearances. VALVES: The HP turbine is fitted with four initial steam stop and control valves. A stop and control valve with steams arranged at right angles to each other are combined in a common body. The stop valves are spring operated single seal valves; the control valves, also of single seat design, have diffuser to reduce pressure losses. IP turbine has four-combined reheat stop and control valves. The reheat stop valves are spring loaded single sealed valves. The control valves operate in parallel and fully opened in the upper load range in the load range, they control the steam flow to the IP turbine and ensure stable operation even when the turbo set is supplying only the station load. Emergency Stop Valves and Control Valves: (ESVs) Turbine is equipped with emergency stop valves to cut off steam supply and with control valves to regulate steam supply. Emergency stop valves (ESV) are provided in the mainstream line and interceptor valves (IV) are provided in the hot reheat line. Emergency stop valves are actuated by servomotor controlled by the protection system. ESV remains either fully open or fully close. Control valves are actuated by the governing system through servomotors to regulate steam supply as required by the load. Valves are either single seat type or double seat type. Single seat type valves are preferred through these require higher force for opening or closing. 20 DEPARTMENT OF MECHANICAL ENGINEERING
  • 21. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES Couplings: Since the shaft (rotor) is made in small parts due to forging limitations and other technological and economic reasons, the couplings are required between any two rotors. This coupling permits angular misalignment, transmits axial thrust and ensures axial location. The couplings are either rigid or semi flexible. The former neither permits angular nor lateral defection while the later permits only angular defection. Number of critical speeds depends upon the modes of vibrations and hence the type of coupling provided between rotors. Generally in 200/210MW turbine,coupling between HPT and IPT is of rigid type and between IPT and LPT is of semi- flexible lens type. 21 DEPARTMENT OF MECHANICAL ENGINEERING
  • 22. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES CHAPTER 4 NORMAL WORKING CONDITION Fig:4.1 Diagram showing Working of Steam turbine The super heated steam from the boiler super heater is bleed into high pressure turbine where the expansion takes place upto an intermediate pressure. This intermediate steam is next further bleed into intermediate pressure turbine after reheating expansion occurs. This expanded steam further sent into low pressure turbine. The kinetic head of the steam is used to rotate or drive the turbine rotor due to expanding on the turbine blades. This rotor of the turbine is coupled to generator shaft. Due to revolution of generator shaft produces the electricity (based on the faraday’s law). The power generated is 14KV is connected to the step up transformer producing 400 KV and further connected to switchyard for distribution. 22 DEPARTMENT OF MECHANICAL ENGINEERING
  • 23. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES Working under abnormal conditions: The super heated steam from the boiler super heater is bleed into high pressure turbine is cut off by a control valve then the by pass system is used because due to the continuous flow of super heated steam from the boiler super heater lead to the damage of steam pipe line due to excessive increase in pressure. Then the steam from the by pass valve, I made to pass through the intermediate pressure turbine or high pressure reheater. Similarly if the steam entering the intermediate pressure turbine is cut off then the steam is made by passed to pass through the control valves and sent to cold reheater. Similarly if the steam entering the low pressure turbine is cut off then the steam is made by passed to pass through boiler feed pump. The expanded steam from the low pressure turbine is sent to the condenser. The condensate is pumped to Low preheater 1,2 and further to low preheater 3 by condensate extraction pump. The water from lph3 is sent to deareator. The water from deareator is sent to high pre-heater 5,6 and then to economizer and then to the boiler furnace. The heat absorbed by the cooling water by condensing the steam in the condenser is sent to the cooling towers for cooling by I.D. fan. 23 DEPARTMENT OF MECHANICAL ENGINEERING
  • 24. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES CHAPTER 5 Specifications of Steam Turbine Make : BHEL, KWU Type : Three cylinder reheat Condensing reaction turbine Nominal rating : 500 MW Peak loading : 545 MW Rated speed : 3000rpm Max/Min speed : 3090/2850rpm (no time limitation) Speed exclusion range : 400 to 2850rpm Steam Pressure & Temperature (Rated Values) Pressure (ata) Temp. (0 C) Initial Steam 170 537.0 First stage pressure 151.79 537.0 HP cylinder exhaust 45 342.5 IP stop valve inlet 40.5 537 Extraction-6 45.0 342.5 Extraction-5 19.52 428.3 24 DEPARTMENT OF MECHANICAL ENGINEERING
  • 25. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES Extraction-4 7.57 302.0 Extraction-3 2.76 197.8 Extraction-2 1.42 138.8 Extraction-1 0.286 67.6 LP cylinder exhaust 0.0884 43.1 Weight(Tonnes) HP IP LP Rotor(complete with Blading) 11.6 21.8 84.6 Reheat stop and control Valve(complete without Bend & pipe section) 17.0 Moments of Inertia(Kg-M2 ) Rotor of HP cylinder 713.0 Rotor of IP cylinder 2145.6 Rotor of LP cylinder 22981.0 Limiting Values Casing temperature(0 C) Alarm at M/c must be shut down at HP turbine exhaust 480.0 500.0 Outlet casing of LPcylinder 90.0 110.0 25 DEPARTMENT OF MECHANICAL ENGINEERING
  • 26. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES Alarm at M/c must be shut down at HP turbine middle +55 +70 IP turbine front +30 +45 IP turbine rear +30 +45 (Spray water to LP cylinder must be switched on at 900 C) Temperature Difference (K) (Between Upper and Lower Casing Section) Steam Purity(KWU Recommended Values) During Operation Conductivity at 250 C Alkaline method <0.10 us/Cm Silica acid(SiO2) <0.010 mg/Kg Total iron(Fe) <0.005 mg/Kg Total copper <0.0010 mg/Kg Sodium(Na) <0.005 mg/Kg Bearing Temperature(0 C) Alarm M/c must be shut down at Vibration(Absolute Vibration) Bearing Shaft Housing Nominal value for alarm 30 microns above normal level Max. value for alarm 35microns 120 microns Limit value for 26 DEPARTMENT OF MECHANICAL ENGINEERING
  • 27. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES tripping(manual) 45microns 200 microns Differential Expansions HP turbine : +5mm to -3mm IP turbine : +8mm to -2mm LP turbine : +30mm to -3mm Material Of Construction Casings HP outer casing Barrel casing GS 17 cr. MOV 511 HP blade carrier GS 17 cr. MO 511 IP casing GS 22 MO 4 LP casing Outer ST 37-2N Inner-I GS 22,MO4,H II,15 MO 3 Inner-II ST 37-2N Shafts HP shaft 28 Cr.MO Ni 59 IP shaft 30 Cr.MO Ni V 511 LP shaft 26 Ni Cr MO V 145 Moving Blades HP turbine first stage x22 Cr MOV 121 HP turbine other stages x20 Cr 13/x22 CrMOV 121 IP turbine stage x20 Cr MO 13/x 20 Cr.30 27 DEPARTMENT OF MECHANICAL ENGINEERING
  • 28. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES LP turbine stage x20 Cr 13 CHAPTER 6 TURBINE AUXILIARIES 6.1 TURBINE GOVERNING SYSTEM Power station turbines are constant sped machines and they are rotated at a speed of 3000rpm to enable the coupled generator to produce electricity at 50 Hz frequency. The main purpose of the governor is to maintain the desired speed of turbine during fluctuation of load on generator by varying steam input into the turbine as required. The governing system is addition to ensuring the following load speed characteristics of the turbine also ensure the following functions. • The run up of the turbine from the rest to the rated speed and synchronizing with the grid. • Meeting the steam load variation in the predetermined manner, when running in parallel with the other machines. • Protecting the machine by reducing the load or shutting of completely in a abnormal and emergency situation. TYPES OF GOVERNING SYSTEMS: 1. Throttle Governing. 2. Nozzle Governing. 3. Bypass Governing. THROTTLE GOVERNING: In Throttle Governing system the governing attachment is attached directly to the Turbine shaft itself and rotates at the same speed of the turbine. According to the turbine speed the attachment linked with the rotor will run. The balls attached to the arrangement will run by the centrifugal force and the valve will operate and allow the steam to flow into the turbine. When the load on the generator will get through off and due to this effect the speed of the turbine will rise 28 DEPARTMENT OF MECHANICAL ENGINEERING
  • 29. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES tremendously which will damage the equipment. The fulcrum attached to the governing system will pull the valve position. NOZZLE GOVERNING: In this method the Nozzles are grouped and the supply of steam is controlled by a special system called as ELECTRO HYDRAULIC CONTROL system. The controlling of the intercept valves will supply the steam to the curtesvey stage of the high pr turbine through intercept valves. There will be a rack and pinion attachment arrangement to operate the intercept valves. The valves will operate radially in a sequence by maintaining the input supply under balancing. At full load the valves will be in fully open condition. The operation of the valves totally carried out by the hydraulic oil supply only thus the nozzle governing system is called as ELECTRO HYDRAULIC CONTROL GOVERNING system. In Ramagundam this system was adopted to have better control on valve operation. It is most effective one and is suitable for control the high capacity turbines. BYPASS GOVERNING: In this system the steam is supplied through a primary valve and is adequate to meet a major function of the maximum, load, which is called the “economic load”. At loads less than this throttling steam through this valve does the regulations. When the load on the turbine exceeds this economic load which can be develop by the UN throttled, full flow through the primary valve. This steam joins the partially spent steam admitting through the primary valve, developing additional blade torque to meet the increased load. 29 DEPARTMENT OF MECHANICAL ENGINEERING
  • 30. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES 6.2 VACUUM SYSTEM As we begin the recirculating processes, the first system, which comes into focus, is the vacuum system. The equipments under this system, as described in this chapter, strive to maximize the work done of turbine by maintaining the rated vacuum limits. Condenser: There are two condensers entered to the two exhausters of the LP turbine. These are surface type condensers with two-pass arrangement. Cooling water pumped into each condenser by a vertical C.W. Pump thru’ the inlet pipe. Water enters the inlet chamber of the front water box, passes horizontally thru’ the brass troes to the water box at the other end, takes a turn, passes thru’ the upper cluster to tubes and reaches the outlet chamber in the front water box. From these, cooling water leaves the condenser thru’ the outlet pipe and discharges into the discharge duct. Steam exhausted from the LP turbine washing the outside of the condenser tubes loses it latent heat to the cooling water and is connected with water in the steam side of the condenser. This condensate collects in the hot well. Fig:6.2 Condenser Ejectors: 30 DEPARTMENT OF MECHANICAL ENGINEERING
  • 31. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES There are two 100% capacity ejectors of the steam eject type. The purpose of the ejector is to evacuate air and other non-condensing gases from the condensers and thus maintain the vacuum in the condensers. This is a 3 stage ejector using steam from the deaerator with 11 ATM header as the working medium. The ejector has three compartments. Steam is supplied generally at a pressure of 4.5 to 5 kg/Cm2 to the three nozzles in the three compartments. Steam expands in the nozzles thus giving a high velocity eject which creates a low pressure zone in the throat of the eject. Since the nozzle box of the ejector is connected to the air pipe from the condenser, the air and pressure zone. The working steam which has expanded in volume comes into contact with the cluster of tube bundles thru’ which condensate in flowing and gets condensed thus further aiding the formulation of vacuum. The non consuming gases of air are further sucked with the next stage of the ejector by the action of the second nozzle. The process repeats itself in the third stage also and finally the steam air mixture is exhausted into the atmosphere thru the outlet. In addition to the main ejectors there is a single stage starting ejectors which is used for initial of vacuum upto 500mm of Hg. It consists of nozzle is connection to the air pipe from the condenser. Fig:7.2.1 Ejector Gland Steam Cooler: Steam from deaerator or from Auxillary steam header is supplied to the end seals of the HP rotor and LP rotor generally at a pressure of 0.01 to 1.03 ata. So as to prevent ingress of atmosphere air into the turbine thru’ the end clearances. This steam supplied to the end seals is extracted by the gland steam cooler by the auction of single stage steam ejector. 31 DEPARTMENT OF MECHANICAL ENGINEERING
  • 32. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES 6.3 CONDENSATE SYSTEM The steam after condensing in the condensing in the condenser known as condensate, is extracted out of the condenser hot well by condensate pump and taken to the deaerator through ejectors, gland steam cooler and series of LP heaters Condensate Pumps: The function of these pumps is to pump out the condensate to the deaerator through’ injector, gland steam cooler and LP heaters. These pumps have four stages and since the suction is at a negative pressure, special arrangements have been made for providing sealing. The level indicator for visual level indication of heating steam condensate pressure vacuum gauges for measurement of steam pressure etc, it is a direct contact type heater combined with feed storage tank of adequate capacity. The heating steam is normally supplied from turbine extractions but during starting and low load operation the steam is supplied from auxiliary source. 32 DEPARTMENT OF MECHANICAL ENGINEERING
  • 33. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES Fig:6.3 Condensate Extraction Pump Deaerator: The Deaerator comprises of two chambers: A) Deaerating column. B) Feed storage tank. Deaerating column is a spray cum tray type cylindrical vessel of horizontal construction with dished ends weided to it. The tray stack is designed to ensure maximum contact time as well as optimum scrubbing of condensate to achieve efficient deaeration. The deaeration column in mounted on the feed storage tank which in turn is supported on rollers at the two ends and a fixed support at the center. The feed storage tank is fabricated from boiler quality steel plates. Man holes are provided on deaerating column as well as on feed storage tank for inspection and maintenance. The condensate is admitted at the top of the deaerating column and flows downwards through the spray valves and trays. The trays and designed to expose though the maximum water surfaces for 33 DEPARTMENT OF MECHANICAL ENGINEERING
  • 34. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES efficient scrubbing to effect the liberation of the associated gases-steam enters from the underneath of the trays and flows in counter direction of condensate. While flowing upwards through the trays, scrubbing and heating is done. Thus the liberated gases move upwards along with the steam. Steam gets condensed above the trays and in turn heats the condensate. Liberated gases escapes to atmosphere from the office opening eant for it. This opening is provided with a number of deflectors to minimize the loss of steam. Deaerator’s main components are given below: 1. Tubular type gauge glass. 2. High level alarm switch. 3. Low level alarm switch. 4. Pressure gauge. 5. Straight thermometers with pockets. 6. Safety valve. 7. Isolating valves for stand pipes. Fig:6.3.1 Deareator 34 DEPARTMENT OF MECHANICAL ENGINEERING
  • 35. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES Fig:6.3.2 Circuit diagram of Condenser Connections 35 DEPARTMENT OF MECHANICAL ENGINEERING
  • 36. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES Fig:6.3.3 Circuit diagram of Condensate System Connections 36 DEPARTMENT OF MECHANICAL ENGINEERING
  • 37. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES 6.4 FEED WATER SYSTEM This system plays an important role in the supply of feed water to the boiler at requisite pressure and steam water ratio. This chapter describes the various auxiliaries under this system starting from Boiler Feed Pump to Feed regulating station via HP heaters. Boiler Feed Pump: This pump is horizontal and of barrel design driven by an Electric motor through a hydraulic coupling. All the bearings of pump and motor are forced lubricated by a suitable oil lubricating system with adequate protection to trip the pump if the lubrication oil pressure fails below a preset valve. The high-pressure boiler feed pump is very expensive machine which calls for a very careful operation and skilled maintenance. The safety in operation and efficiency of the feed pump depends largely on the reliable operation and maintenance. Operation staff must be able to find out the causes of defect at the very beginning which can be easily removed without the endangering the operator of the power plant and also without the expensive dismantling of the high pressure feed pump. The feed pump consists of the pump barrel, into which is mounted the inside stator together with rotor. The hydraulic part is enclosed by the high pressure cover along with the balancing device. The suction side of the barrel and the space in the high pressure cover behind the balancing device are enclosed by the low pressure covers along with the stuffing box casings. The brackets of the radial bearing of the suction side and radial and thrust bearing of the discharge side are fixed to the low pressure covers. The entire pumps is mounted on a foundation frame. The hydraulic coupling and two claw couplings with coupling guards are also delivered along with the pump. Water cooling and oil lubricating connections are provided with their accessories. Fig: 6.4 Turbine Driven Boiler Feed Pump 37 DEPARTMENT OF MECHANICAL ENGINEERING
  • 38. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES High Pressure Heaters: These are regenerative feed water heaters operating at high pressure and located by the side of turbine. These are generally vertical type and turbine bled steam pipes are connected to them. HP heaters are connected in series on feed water side and by such arrangement, the fed water, after feed pump enters the HP Heaters. The steam is supplied to these heaters from the bled point of the turbine through motor operated valves. These heaters have a group bypass protection on the feed water side. In the event of tube rupture in any of the HPH and the level of the condensate rising to dangerous level, the group protection device diverts automatically the feed water directly to boiler, thus bypassing all the 3 HP heaters. As shown in fig.V-8, feed water flows through the tube spirals and is heated by seam around the tubes in the shell of the heaters. These heaters are cylindrical vessels with welded dished ends an with integrated, de-superheating, condensing and sub cooling sections. The internal tube system of spirals is welded to the inlet and outlet headers. In order to facilitate assembly and disassembly, rollers at the side of the header have been provided. Both feed water and steam entries and exists are from the bottom end of the heaters. This design offers the advantage to optimize the arrangement of piping and the location of the heaters at power station. Following fittings are generally provided on the HP heaters: a) Gauge glass for indicating the drain level. b) Pressure gauge with three way cock. c) Air vent cock. d) Safety valve shell side. e) Seal pot. f) Isolating valves. g) High level alarm switch. Group protection device of HP Heaters: In the event of rising of the drain condensate level in any one of the HP heater, to the emergency high level, the feed water flowing through the coils of the heaters, is diverted automatically directly to the boiler, thereby all the groups of three HP heaters is by passed. Turbine Driven Boiler Feed Pump: The single cylinder turbine is of the axial flow type.The live steam flows through emergency stop valve and then through the main control valves.The valves regulate the steam supply through the turbine.There are 14 stages of reaction blading.The turbine is provided with the electro hydraulic governing system.The steam exhausted from the BFP turbine is directly connected to the main condenser and the turbine glands are gland steam.There are 2 TDBFP’s for each 500MW unit at ramagundam of capacity 1080.3m3/hr at 204.32 bar. 38 DEPARTMENT OF MECHANICAL ENGINEERING
  • 39. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES Fig: 6.4.1 HP Heater Drip/Drain System: The steam, bled from the turbine, after condensation is termed as drip/ drain. The drain is cascaded from HP 7 to IPs and further to LP 2 all the condensate due to the bled steam of the heaters is collected to in deaerator (during normal load) and in LP 2, from where the drain is pumped back into the feed system. The drain from LP.1 is only connected to the condenser by U- tube water seal. The drain from HP.5 will go to deaerator or LP.4 depending on the shell pressure and load on the machine. All the LP heater drains are having manual bypass, which can be operated in case of any individual regulators, fail. The drain from LP.2 can be regulated to condenser in case the level in LP.2 rises to a predetermined level. Drip Pumps: Two numbers of sectional multistage centrifugal horizontal pumps per unit are provided. One will be running and the other is standby (100% standby). These are especially suited for the purpose of pumping from the space of high vacuum. Condensate drip from LP heater No.2 (which is under vacuum) is pumped again to main condensate line in between LP heaters. 39 DEPARTMENT OF MECHANICAL ENGINEERING
  • 40. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES Fig:6.4.2 Circuit Diagram of Turbine Driven Boiler Feed Pump 40 DEPARTMENT OF MECHANICAL ENGINEERING
  • 41. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES 41 DEPARTMENT OF MECHANICAL ENGINEERING
  • 42. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES 6.5 COOLING WATER SYSTEM • Equipment cooling water (ECW) system: This water is used to cool the heated lubricating oil coming from the lube oil coolers of boiler and turbine side. This is demineralised water and is supplied through ECW pumps. • Auxiliary cooling water (ACW) system: This is raw water, taken a taping from CW pumps discharge side, pressurized and circulated in a Plate Heat Exchanger to cool the heated ECW water. COOLING TOWERS (CTs): • A closed circuit cooling system is used for heat rejection that consists of cooling pond and two cooling towers, ponds and towers are connected in a parallel arrangement to study the behavior of the cooling system. • The cooling tower models based on the analogy approach of a cooling tower and an heat exchanger. An effectiveness-NTU method is employed to predict the cooling tower performance with respect to ambient and load conditions. • For the circulation of cooling capacity of the cooling pond surface, a semi empirical approach is selected that is based on the combination of free and forced convection. The water flow in the pond is a approximated by a plug flow model. • From the energy transfer and flow model a stimulation program is developed that is capable of predicating of cooling pond temperatures dependent on meteorological conditions and head load on the pond. • A simple model of an atmospheric cooling spray is employed. Fig: 6.5 Cooling towers 42 DEPARTMENT OF MECHANICAL ENGINEERING
  • 43. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES 6.6 LUBRICATION OIL SYSTEM Introduction: same oil is used for governing & lubrication. The oil is kept in the main oil tank. The governing is designed for operation at the oil pressure of 14kg/cmsq while lubrication of bearings is designed to work at 2kg/cmsq.The following equipment is available in the lubricating system. 1. Auxiliary oil pump 2. A.C lube oil pump 3. D.C emergency oil pump 4. main oil pump 5. booster pump 6. oil tank 7. oil coolers 8. vent fans Lubrication oil system lubricates both turbine and generator bearings. Moreover it supplies oil to seal oil system. During normal operation of turbine shaft directly drives pump (centrifugal type) at 3000 rpm and supplies oil to the lubrication system. Auxiliary oil pump is incorporated in the oil system to deliver oil to governing system and bearings at the time of starting of turbine with back up protection. D.C. stands by oil pumps are used for bearing oil supply only. AUXILARY OIL PUMP: It is centrifugal pump driven by A.C electric motor. Auxiliary oil pump is provided for meeting the requirement of oil for the turbine governing system and bearing lubrication system during and stopping. It is mounted on the main oil tank. DC LUB OIL PUMP: The bearing are protected from possible lubrication failure by the provision of two automatically starting oil pumps-i.e. AC lubrication oil pump and DC emergency oil pump AC lube oil pump automatically start when lubrication oil pressure drops to 1.2kg/cmsq. The emergency lubrication oil pump (DC driven) is provided as a backup protection against the failure of AC lubrication oil pump or AC supply. DC lubrication oil pump cuts in automatically when lubrication pressure drops down to 0.8kg/cmsq. Both AC lubrication oil pump and DC lubrication oil pump are mounted on main oil tank. MAIN OIL PUMP: During normal operation of turbine, main lubrication oil pump is mounted on turbine shaft and driven by turbine shaft at 3000rpm. It supplies oil to the governing and lube oil system. 43 DEPARTMENT OF MECHANICAL ENGINEERING
  • 44. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES Pump is designed for continues operation at 3000rpm and installed inside the front pedestal of turbine. The MOP is capable to supply oil to the system at full capacity when the turbine reaches to 2800rpm. Then the AOP, which is in service, will be separated from the system automatically. BOOSTER PUMP: The oil pressure developed by auxiliary oil pump discharge during staring and stopping of turbine operates booster pump. During normal running of turbine (at 3000rpm) it is operated by main oil pump discharge. It supplies oil to lubricating. OIL TANK: Oil is stored in main oil tank (MOT) whose capacity is 16cum. Two numbers of vapour fans are mounted on MOT to extract oil vapour and dissolved gases also to the atmosphere from MOT. Auxiliary oil pump, AC lubrication oil pump, DC lubrication booster pump and oil coolers are mounted on MOT. Oil level indicators and instruments such as oil pressure and temperature gauges and pressure switches for pump interlocks and annunciation’s are mounted on MOT. Local starting and stopping of pumps and local pressure indicators are also available on MOT. The oil cooler changing system and magnetic duplex system selection also mounted on MOT. The line to oil purification system is connected to MOT. OIL COOLERS: Oil coolers are of surface type. Usually one cooler will be in service while the other is standby. It consists of tubes through which cooling medium flows. The cooling medium used is raw water. The oil cooler consist of the following. 1. shell 2. upper water chamber 3. lower water chamber 4. tube system 5. cooler change over mechanism 44 DEPARTMENT OF MECHANICAL ENGINEERING
  • 45. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES Fig:6.6 Turbine Lube Oil System 45 DEPARTMENT OF MECHANICAL ENGINEERING
  • 46. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES 46 DEPARTMENT OF MECHANICAL ENGINEERING
  • 47. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES Fig:6.6.1 Steam Turbine flow Diagram Showing Auxiliaries 47 DEPARTMENT OF MECHANICAL ENGINEERING
  • 48. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES CONCLUSION The working of Steam Turbine 500MW was studied, the process of Conversion of Kinetic head of Steam into Mechanical Energy was observed. The Auxiliaries of Steam Turbine and their importance in power generation were studied and observed the various components involved in the working of Steam Turbine. 48 DEPARTMENT OF MECHANICAL ENGINEERING
  • 49. STUDY OF WORKING OF STEAM TURBINE AND ITS AUXILIARIES BIBILOGRAPHY http://www.brighthub.com/engineering/mechanical/articles/60844.aspx#ixzz1UAY phNuz http://www.scribd.com/doc/46740256/Power-Plant-Familiar-is-at-Ion-v-III http://www.seminarprojects.com/Thread-steam-turbine en.wikipedia.org/wiki/Thermal_power_station www.indiamart.com › ... › Industrial Plants & Machines 49 DEPARTMENT OF MECHANICAL ENGINEERING

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