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Steam Turbines


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Presentation about steam turbines including how is it work, parts, operations and controlling with examples of the turbine exists in our plant EPPC

Published in: Engineering
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Steam Turbines

  1. 1. Steam Turbines Egyptian Propylene and Polypropylene Company. PDH Plant. Eng.Amir Ayad
  2. 2. Introduction • We classify as turbo-machines all those devices in which energy is transferred either to or from, a continuously flowing fluid by the dynamic action of one or more moving blade rows the word turbo or turbines is of Latin origin and implies that which spins or whirls around. • Essentially, a rotating blade row or rotor changes the stagnation enthalpy of the fluid moving through it by either doing positive (compressors & pumps) or negative work (turbines), depending upon the effect required of the machine. These enthalpy changes are intimately linked with the pressure changes occurring simultaneously in the fluid.
  3. 3. TURBOMACHINES Turbines, compressors and fans are all members of the same family of machines called turbo-machines. A turbo-machine is a power or heat-generating machine, which employs the dynamic action of a rotating element, the rotor; the action of the rotor changes the energy level of the continuously flowing fluid through the turbo-machine. Two main categories of turbo-machine are identified: • Absorb power to increase the fluid pressure or head (ducted fans, compressors and pumps). • Produce power by expanding fluid to a lower pressure or head (hydraulic, steam and gas turbines).
  4. 4. TURBOMACHINES Turbine Compressor Pumps
  5. 5. Types of Turbines Hydraulic Gas Turbine Steam Turbine Turbine
  6. 6. Hydraulic Turbines • A water turbine is a rotary engine that takes energy from moving water. • Flowing water is directed on to the blades of a turbine runner, creating a force on the blades. • Since the runner is spinning, the force acts through a distance (force acting through a distance is the definition of work). • In this way, energy is transferred from the water flow to the turbine. • Used to generate electricity from the energy of water.
  7. 7. Hydraulic Turbines
  8. 8. Gas Turbine • A gas turbine, also called a combustion turbine, is a type of internal combustion engine. It has an upstream rotating compressor coupled to a downstream turbine, and a combustion chamber in-between. • The compressor, which draws air into the engine, pressurizes it, and feeds it to the combustion chamber at speeds of hundreds of miles per hour. • The combustion system, typically made up of a ring of fuel injectors that inject a steady stream of fuel into combustion chambers where it mixes with the air. The mixture is burned at temperatures of more than 2000 degrees F. The combustion produces a high temperature, high pressure gas stream that enters and expands through the turbine section.
  9. 9. Gas Turbine • The turbine is an intricate array of alternate stationary and rotating aerofoil-section blades. As hot combustion gas expands through the turbine, it spins the rotating blades. • The rotating blades perform a dual function they drive the compressor to draw more pressurized air into the combustion section, and they spin a generator to produce electricity. • This high-temperature high-pressure gas enters a turbine, where it expands down to the exhaust pressure, producing a shaft work output in the process. • The turbine shaft work is used to drive the compressor and other devices such as an electric generator that may be coupled to the shaft.
  10. 10. Gas Turbine • The energy that is not used for shaft work comes out in the exhaust gases, so these have either a high temperature or a high velocity. • these gases can sometimes be used directly, they are more often passed to a heat recovery boiler for the production of hot water or steam. Where the site’s heat requirement exceeds the heat available in the exhaust gases, or is variable, a burner can be incorporated in the ducting between the turbine and the heat recovery boiler to increase the temperature of the exhaust gases and improve the heat output of the plant. • Gas turbines are used to power aircraft, trains, ships, electrical generators, or even tanks • Gas turbines accept most commercial fuels, such as petrol, natural gas, propane, diesel, and kerosene as well as renewable fuels such as biodiesel and biogas. • Gas turbine, may be spinning at 100,000 to 500,000 rpm.
  11. 11. Gas Turbine
  12. 12. Thermodynamic Theory • In an ideal gas turbine, gases undergo three thermodynamic processes: 1. an isentropic compression, 2. an isobaric (constant pressure) combustion 3. an isentropic expansion. Together, these make up the Brayton cycle. • In a practical gas turbine, mechanical energy is irreversibly transformed into heat when gases are compressed (in either a centrifugal or axial compressor), due to internal friction and turbulence. • Passage through the combustion chamber, where heat is added and the specific volume of the gases increases, is accompanied by a slight loss in pressure. During expansion amidst the stator and rotor blades of the turbine, irreversible energy transformation once again occurs
  13. 13. Brayton Cycle • Ideal Brayton cycle: 1. isentropic process - ambient air is drawn into the compressor, where it is pressurized. 2. isobaric process - the compressed air then runs through a combustion chamber, where fuel is burned, heating that air—a constant-pressure process, since the chamber is open to flow in and out. 3. isentropic process - the heated, pressurized air then gives up its energy, expanding through a turbine (or series of turbines). Some of the work extracted by the turbine is used to drive the compressor. 4. isobaric process - heat rejection (in the atmosphere).
  14. 14. Brayton Cycle
  15. 15. Steam Turbines What's Steam Turbine? • The steam turbine is a prime mover in which the potential energy of steam is transformed into kinetic energy and the latter in its turn is transformed into the mechanical energy of rotation of the turbine shaft. • The turbine shaft, directly, or with the help of a reduction gearing, is connected with the driven mechanism which can be generator or a compressor.
  17. 17. Steam Turbines The simplest single-disc steam turbine consists of the following parts • Shaft. • Disc with moving blades • Fixed blades on its periphery. • Expansion nozzle. • The shaft along with the disc mounted upon it comprises the most important part of the turbine and is known as the rotor, which is housed in the turbine casing. • The journals of the shaft are placed in bearings, which are located in the base of the turbine casing
  18. 18. Steam Turbines
  19. 19. Steam Turbines Theory of Working: • In turbines of these types the expansion of the steam is achieved from its initial pressure to its final one in a single nozzle or a group of nozzles situated in the turbine stator and placed in front of the blades of the rotating disc. • The decrease of steam pressure in the nozzles is accompanied by a decrease of its heat content; this decrease of heat content achieved in the nozzles subsequently accounts for the increase in the velocity of the steam issuing from the nozzles. • The energy velocity of the steam jets exerts an impulse force on the blades and performs mechanical work on the shaft of the turbine rotor.
  20. 20. Steam Turbines
  21. 21. Steam turbine is based upon Rankine cycle
  22. 22. Rankine cycle • Process 1-2: The working fluid is pumped from low to high pressure. As the fluid is a liquid at this stage, the pump requires little input energy. • Process 2-3: The high pressure liquid enters a boiler where it is heated at constant pressure by an external heat source to become a dry saturated vapour. • Process 3-4: The dry saturated vapour expands through a turbine, generating power. This decreases the temperature and pressure of the vapour, and some condensation may occur. The output in this process can be easily calculated using the Enthalpy-entropy chart or the steam tables. • Process 4-1: The wet vapour then enters a condenser where it is condensed at a constant pressure to become a saturated liquid. • In an ideal Rankine cycle the pump and turbine would be isentropic, i.e., the pump and turbine would generate no entropy and hence maximize the net work output. Processes 1-2 and 3-4 would be represented by vertical lines on the T-S diagram and more closely resemble that of the Carnot cycle. • Rankine cycle shown here prevents the vapor ending up in the superheat region after the expansion in the turbine, which reduces the energy removed by the condensers.
  23. 23. Rankine cycle T-S diagram
  24. 24. • An ideal Rankine cycle operates between pressures of 30 kPa and 6 MPa. The temperature of the steam at the inlet of the turbine is 550°C. Find the net work for the cycle and the thermal efficiency. • Wnet=Wturbine-Wpump OR Qin-Qout • Thermal efficiency hth=Wnet/Qin • Net work done is converted into power output of turbine.
  25. 25. Steam Turbines Classification Steam Turbine Flow Direction Axial Radial Way of energy conversion & type of blading Impulse Reaction Type of Compounding Pressure compounding Velocity compounding Pressure- Velocity compounding Exhausting condition Condensing Extraction Backpressure Reheat No.of stages Single Multi Inlet Pressure Low Medium High
  26. 26. Flow Directions Axial Flow turbine • The great majority of turbines, especially those of high power are axial flow. • In such turbines the steam flows in direction parallel to the axis of the shaft leaves the turbine in the same direction. • The most preferred turbine for electricity generation as several cylinders can be coupled together to achieve a turbine with greater output.
  27. 27. Axial Flow Turbines
  28. 28. Flow Directions Radial flow • In a radial flow turbine the steam enters the turbine in the direction of its radius and leaves it in the direction of the axis of the shaft. • Not preferred for electricity generation and employed for small outputs such as driving pumps.
  29. 29. Flow Directions
  30. 30. Way of Energy Conversion 1) way of energy conversion - impulse turbines - reaction turbines
  31. 31. Types of Blade • The heat energy contained within the steam that passes through a turbine must be converted into mechanical energy to achieve this depends on the shape of the turbine blades. The two basic blade shapes are: 1- Impulse 2- Reaction
  32. 32. Impulse Turbine • Impulse working on the principle of high pressure steam hitting against moving blades. • Pressure drop only occurs at the nozzles in the turbine. • In an impulse turbine, the fluid is forced to hit the turbine at high speed (due to change of potential energy to kinetic energy at the nozzles). • They are generally installed in the higher pressure sections of the turbine where the specific volume of steam is low. • Blades are usually symmetrical have entrance and exit angles 20. • Blades are short and have constant cross section area.
  35. 35. Impulse Turbine NOZZLE STEAM CHEST ROTOR
  37. 37. Reaction Turbine • The principle of pure reaction turbine is that all energy stored within the steam is converted to mechanical energy by reaction of the jet of steam as it expands at the blades of the rotor. • In a reaction turbine the steam expands when passing across fixed blades where pressure drop occurs and velocity increase. • When passing to moving blades both pressure and velocity decreases (work extraction). STEAM CHEST ROTOR
  38. 38. Comparison Impulse Reaction Pressure drop occurs in both fixed and rotating blades. Enthalpy changed into kinetic energy in both stationary and moving blades There is change in both pressure and velocity as the steam flows through the moving blades. Whole pressure drop occurs at the fixed blades. Whole enthalpy is changed into kinetic energy in the nozzle There is no change in the pressure of the steam as it passes through the moving blades. There is change only in the velocity of the steam flow.
  39. 39. Impulse Stage • An impulse stage consists of stationary blades forming nozzles through which steam expands, increasing velocity as a result of decreasing pressure. • The steam then strikes the rotating blades and performs work on them, which in turn decreases velocity (kinetic energy)of the steam. • The steam then passes through another set of stationery blades which turn it back to original direction and increases the velocity again through nozzle action.
  40. 40. Reaction Stage • In the reaction turbine both the moving and fixed blades are designed to act like nozzles. • As steam passes through the non-moving blades, no work is exerted pressure will decrease and velocity will increase. • In the moving blades are designed to act like nozzles velocity and pressure will decrease due to wok being extracted from the steam.
  41. 41. Way of compounding • Compounding of steam turbines is the method in which energy from the steam is extracted in a number of stages rather than a single stage in a turbine. • A compounded steam turbine has multiple stages i.e. it has more than one set of nozzles and rotors, in series, keyed to the shaft or fixed to the casing, so that either the steam pressure or the jet velocity is absorbed by the turbine in number of stages. • The steam produced in the boiler has very high enthalpy. In all turbines the blade velocity is directly proportional to the velocity of the steam passing over the blade.
  42. 42. Why it’s required ? • Now, if the entire energy of the steam is extracted in one stage, i.e. if the steam is expanded from the boiler pressure to the condenser pressure in a single stage, then its velocity will be very high. • Hence the velocity of the rotor (to which the blades are keyed) can reach to about 30,000 rpm, which is pretty high for practical uses because of very high vibration. • Moreover at such high speeds the centrifugal forces are immense, which can damage the structure. Hence, compounding is needed. • The high velocity which is used for impulse turbine just strikes on single ring of rotor that cause wastage of steam ranges 10% to 12%. To overcome the wastage of steam compounding of steam turbine is used.
  43. 43. Pressure Compounding impulse turbine • The pressure compounded Impulse turbine is also called as Rateau turbine, after its inventor. This is used to solve the problem of high blade velocity in the single-stage impulse turbine. • It consists of alternate rings of nozzles and turbine blades. The nozzles are fitted to the casing and the blades are keyed to the turbine shaft. • In this type of compounding the steam is expanded in a number of stages, instead of just one (nozzle) in the velocity compounding. It is done by the fixed blades which act as nozzles. The steam expands equally in all rows of fixed blade. • The steam coming from the boiler is fed to the first set of fixed blades i.e. the nozzle ring. The steam is partially expanded in the nozzle ring. Hence, there is a partial decrease in pressure of the incoming steam. This leads to an increase in the velocity of the steam. Therefore the pressure decreases and velocity increases partially in the nozzle.
  44. 44. Pressure Compounding impulse turbine • This is then passed over the set of moving blades. As the steam flows over the moving blades nearly all its velocity is absorbed. However, the pressure remains constant during this process. • After this it is passed into the nozzle ring and is again partially expanded. Then it is fed into the next set of moving blades, and this process is repeated until the condenser pressure is reached. • It is a three stage pressure compounded impulse turbine. Each stage consists of one ring of fixed blades, which act as nozzles, and one ring of moving blades. As shown in the figure pressure drop takes place in the nozzles and is distributed in many stage
  45. 45. Pressure Compounding impulse turbine
  46. 46. Velocity Compounding impulse turbine • The velocity compounded Impulse turbine was first proposed by C G Curtis to solve the problem of single stage Impulse turbine for use of high pressure and temperature steam.The rings of moving blades are separated by rings of fixed blades. The moving blades are keyed to the turbine shaft and the fixed blades are fixed to the casing. The high pressure steam coming from the boiler is expanded in the nozzle first. The Nozzle converts the pressure energy of the steam into kinetic energy. It is interesting to note that the total enthalpy drop and hence the pressure drop occurs in the nozzle. Hence, the pressure thereafter remains constant. • This high velocity steam is directed on to the first set (ring) of moving blades. As the steam flows over the blades, due the shape of the blades, it imparts some of its momentum to the blades and losses some velocity. Only a part of the high kinetic energy is absorbed by these blades. The remainder is exhausted on to the next ring of fixed blade. • The function of the fixed blades is to redirect the steam leaving from the first ring moving blades to the second ring of moving blades. There is no change in the velocity of the steam as it passes through the fixed blades. The steam then enters the next ring of moving blades; this process is repeated until practically all the energy of the steam has been absorbed.
  47. 47. Velocity Compounding impulse turbine
  48. 48. Pressure-Velocity compounded Impulse Turbine • It is a combination of the above two types of compounding. The total pressure drop of the steam is divided into a number of stages. Each stage consists of rings of fixed and moving blades. Each set of rings of moving blades is separated by a single ring of fixed blades. In each stage there is one ring of fixed blades and 3-4 rings of moving blades. Each stage acts as a velocity compounded impulse turbine. • The fixed blades act as nozzles. The steam coming from the boiler is passed to the first ring of fixed blades, where it gets partially expanded. The pressure partially decreases and the velocity rises correspondingly. The velocity is absorbed by the following rings of moving blades until it reaches the next ring of fixed blades and the whole process is repeated once again.
  49. 49. Exhaust Utilization 1. Condensing Turbine • In this type of turbine steam with pressure (42 bar) and temperature (400C) enters where pressure drop is occurred in first stage impulse turbine. • Then expands in reaction turbine and exhaust with lower pressure than atmospheric pressure. • The cooling water condenses the steam turbine exhaust in the condenser creating the condenser vacuum by using ejector or small compressor (vacuum pump). • This type is used to get only mechanical energy and not to use the exhaust steam ماكنة حمل Load machine البخار المكثف صمام التحكم بكمية جريان البخار دخول البخار steam inlet ريشة ثابتة )التوجيهية( ريش متحركة
  50. 50. Condensing turbine
  51. 51. Exhaust Utilization 2. Extraction Turbine • In this turbine steam is withdrawal from one or tow stages at a certain pressure for using at plant processing such as heating also called (bleeder turbines). • This type used for having a steam with a certain pressure to be used in other process. صمام التحكم بكمية جريان البخار دخول البخار steam inlet Load machine صمام التحكم ريش متحركة ريش ثابتة سحب البخار من مرحلة وسطية لتلبية متطلبات أخرى خروج بخار مكثف
  52. 52. Extraction Turbine
  53. 53. Exhaust Utilization 3. Backpressure Turbine • Non condensing turbine which exhausts it’s steam to industrial process or facility steam which used in another process. ماكنة حمل Load machine البخار المكثف فوق الضغط الجوي 1 ضغط جوي bar > صمام التحكم بكمية جريان البخار دخول البخار steam inlet ريش ثابتة )التوجيهية( ريش متحركة Back Pressure Turbine مخطط توربين بخاري البخار المكثف أعلى من الضغط الجوي
  54. 54. Backpressure Turbine
  55. 55. Reheat Turbine • Reheat turbines are also used almost exclusively in electrical power plants. • In a reheat turbine, steam flow exits from a high pressure section of the turbine and is returned to the boiler where additional superheat is added. • The steam then goes back into an intermediate pressure section of the turbine and continues its expansion.
  56. 56. 116MT01 Condensing turbine with a backpressure extraction Extraction MP steam to drive LP chamber MP steam LP steam to condenser LP chamber Balance line HP steam
  57. 57. 118MT01 a backpressure turbine charging MP & LP to headers HP steam MP steam LP steam
  58. 58. What is a stage in a steam turbine? • In an impulse turbine, the stage is a set of moving blades behind the nozzle. • In a reaction turbine, each row of blades is called a "stage. • " A single Curtis stage may consist of two or more rows of moving blade.
  59. 59. Number of stages & Inlet Pressure • Single stage • Multi-stage • High pressure (p>6,5MPa) • Intermediate pressure(2,5MPa <p<6,5MPa) • Low-pressure (p<2,5MPa
  60. 60. Steam Turbine Components Casing Guide Blade Carrier Rotor Blades Blades
  61. 61. Steam Turbine Components • Frame (Base): supports rotor , stator and governor pedestal. • Shell: consists of casing , nozzles , steam chest and bearings. • Rotor:consists of HP&MP&LP pressure stage blades , shaft and governor pedestal components, thrust bearing, journal bearings, Turing gear and main lube oil systems. • Governor pedestal: consists of turbine speed governor and protective devices.
  62. 62. Turbine Rotor As the steam turbine operates under high temperature and speeds high, the material that makes them rotary axis must be homogeneous and pure of impurities that cause cracks under pressure and high temperature as the material must be of high hardness and conducting laboratory tests including examination (Charpy hardness) to make sure of the hardness of metal rotary axis and makes this axis melting steel in electric oven and then pour molten steel in the mold topic in a room deflated to ensure that no entry impurities to steel and added to this alloy steels several metals to increase hardness and resistance to rust and corrosion, including metal * chromium Cr * nickel and vanadium Ni * Va * Alamuedinom Mo
  63. 63. Rotor : Forging
  64. 64. Rotor: Turing complete
  65. 65. Rotor complete
  66. 66. Turbine Rotor HP blades MP blades LP blades
  67. 67. Turbine Casing TOP Casing • The Casing of the turbine is simple structure used to minimize distortion due to temperature changes. • They are constructed in two parts (Top – Bottom) along a horizontal joint so that the turbine is easy to open for inspection. • With the top casing is removed the rotor can also be easily withdrawn without the interfering with the alignment of the bearings Bottom Casing
  68. 68. Turbine Casing Flanges • One method of joining the top and bottom of the casing is by using flanges with machined holes. • Bolts are inserted into these machined holes to hold the top and bottom casing together. • To prevent leakage from the joint between the top flange the joint faces are accurately machined.
  69. 69. Turbine blades • Blade design is extremely important in attaining high turbine reliability. • Blades are milled from stainless steel within strict specifications for proper strength and corrosion. • In HP impulse turbine blades are short so they don’t need to change the cross section. where the length of the blade (Root) to (Top) does not constitute a significant change for the length of the rotor disk diameter (Bladed Rotors disk). • But in case reaction turbine blades are long can reach 1m.
  70. 70. Turbine blade fixing • Various root fixing shapes have been developed for turbine blading to suit construction requirements and conditions under which turbine operate. • The most popular types are 1. Grooves 2. Straddle 3. Rivet
  71. 71. Blades Fixing
  72. 72. Blades Fixing
  73. 73. Diaphragms function The purpose of nozzles is to expand the high pressure steam to extract its energy and direct the resulting steam jets toward the rotating buckets or blades • The nozzles are made up of many partitions that have the appearance of airfoils, similar to rotating blades. • The partitions change the direction of steam flow to cause it to impinge on the moving blades of the rotor, as well as to increase the velocity of the flow. • The partitions are held in place in a disk-like structure that, together with the partitions, is called a diaphragm. Figure shows a typical diaphragm. • The diaphragm fits into circumferential slots in the turbine shell inside diameter. • There are labyrinth seals at the inside diameter of the diaphragm to reduce steam leakage between the rotor and the diaphragm and seal strips near the outside diameter to reduce leakage around the bucket tips.
  74. 74. Diaphragms ( Guide Blades)
  75. 75. Diaphragms ( Guide Blades)
  76. 76. Guide Blade Carrier
  77. 77. Guide Blade Carrier
  78. 78. Steam Chest • The steam chest, located on the forward, upper half of the HP turbine casing, houses the throttle valve assembly. • This is the area of the turbine where main steam first enters the main engine. The throttle valve assembly regulates the amount of steam entering the turbine. • After passing through the throttle valve, steam enters the nozzle block.
  79. 79. Balancing Piston (dummy chamber) • All the rotors of pumps, compressors and turbines experience the axial thrust due to differential pressure between suction /discharge or inlet /outlet. • For small machines a thrust bearing, balancing disk are installed on the rotor to absorb axial loading. for large machines a device called balancing piston is keyed/shrunk to the rotor at at high pressure rotor end. • This balance piston is exposed to high pressure on one side and discharge pressure/low pressure on other side. The rotor thrust is balanced based on the area provided on either side of balance piston. • (dynamic Pressure x Area)= force which acts on HP/LP side of the balance piston keeps the rotor in position and absorbs major portion of axial thrust. Residual axial loading is absorbed by thrust bearing.
  80. 80. Wheel Chamber • Wheel chamber in case of steam turbine is a chamber provided on HP side of balance piston. It is between first stage( Impulse stage ) nozzle and balance piston. For the same load on the turbine, if wheel chamber pressure increases it indicates turbine fouling. • Based on wheel chamber pressure and turbine loading, it is possible to judge turbine fouling, turbine rotor/stator sealing condition, balance piston sealing condition
  81. 81. Balancing Drum Impulse blades Wheel chamber Reaction blades
  82. 82. Thrust bearing • One of the basic purposes of a bearing is to provide a frictionless environment to support and guide a rotating shaft. • They typically depend on a regular supply or motor oil for lubrication, too; without this they can wear down, which over time will usually lead to engine trouble. • A thrust bearing is a particular type of rotary rolling-element bearing. Like other bearings they permit rotation between parts, but they are designed to support a predominately axial load. • The bearing pressure acts parallel to the shaft axis. Types of Thrust bearing 1. Thrust ball bearings. 2. Spherical roller thrust bearings. 3. Fluid film thrust bearings. 4. Tapered roller thrust bearings.
  83. 83. Thrust bearing Types Ball bearing Spherical roller Fluid film Tapered roller
  84. 84. Journal bearing • Journal bearings aligns the rotor and it will cushion the radial movement. • The bearing pressure acts perpendicular to the shaft axis.
  85. 85. Vibration Element Thrust Bearing Journal Bearing
  86. 86. Turbine Seals • To prevent the entry of air from the outside to the inside of the turbine when the steam pressure inside the final stages less than atmospheric pressure, as in the type of turbine steam condenser under pressure • To prevent the exit of steam from inside the turbine to the outside of the exit point axis of the rotor from the cover of the turbine when the steam pressure in the final stages higher than the atmospheric pressure, as in the turbine above atmospheric pressure and a seal in this Mechanic (Mechanical cell) in the turbine Small Size. • In large turbines are used mechanical seal with vapor supplied from another source pressure is higher than the vapor pressure in the final stage.
  87. 87. Seal steam • Is an entry vapor pressure and certain temperature on each of the front and end of the turbine. seal steam may enter only into the front according to turbine type and operating conditions. • Under the low-load conditions, the L.P end of the turbine will be under the vacuum of the surface condenser. The vacuum will tend to pull in cold atmospheric air through the seals along the shaft. • Cold air will have a detrimental effect on the hot metal of the shaft which can lead to damage. In order to minimize these problems, a manually controlled supply of low pressure SEAL steam (about 2 Psi), is piped to a common line feeding the glands of the machine. • A power loss is associated with steam leakage or air ingress. Thus, the design of glands and seals is optimized to reduce any leakage.
  88. 88. • To improve the efficiency of the turbine to get the highest Power with less quantity of steam where the steam expands inside the turbine to be up to a pressure less than atmospheric pressure. • Because there is a steam ejector nozzles which drag air and gases inside the condenser lead to the occurrence of back pressure at the end of the turbine. • Consumption of steam more to maintain the same power on it, affecting the efficiency of the turbine. T.steam E . steam Gland steam Seal steam
  89. 89. LABYRINTH Seal • A labyrinth seal is a type of mechanical seal that provides a tortuous path to help prevent leakage. • An example of such a seal is sometimes found within a shaft's bearing to help prevent the leakage of the oil lubricating the bearing. • A labyrinth seal may be composed of many grooves that press tightly inside another axle, or inside a hole, so that the fluid has to pass through a long and difficult path to escape. Shaft Grooves
  90. 90. Stage LABYRINTH Seal • As well as the type of sealant used to labyrinth seal between the stage and the next, and put on the barrier between the two stages where it very close to the rotary axis to prevent leakage of steam between the rotor axis. • Where it forces the steam to pass through diaphragms between blades in order to increase turbine efficiency
  91. 91. Seal Air • Enters to the turbine front between seal steam and turbine shaft bearings. • To prevent seal steam from entering or it’s condensate to the shaft bearings and the lube oil may contaminate.
  92. 92. Unit 116 Condenser • Used to condense the low pressure steam exhaust from the turbine in order to recycle this condensate back to boiler
  93. 93. Unit 116 Vacuum System • Vacuum system is used to condense the steam which was not condensed in the condenser by decreasing the pressure in the condenser and also decreasing pressure in Low pressure chamber to increase turbine efficiency. • It consists of (Ejector – common condenser)
  94. 94. Steam Ejector • A steam ejector, is a type of pump that uses the Venturi effect of a converging-diverging nozzle to convert the pressure energy of a motive fluid to velocity energy which creates a low pressure zone that draws in and entrains a suction fluid. • After passing through the throat of the injector, the mixed fluid expands and the velocity is reduced which results in recompressing the mixed fluids by converting velocity energy back into pressure energy. • The motive fluid may be a liquid, steam or any other gas. The entrained suction fluid may be a gas, a liquid, a slurry, or a dust-laden gas stream. • The adjacent diagram depicts a typical modern ejector. It consists of a motive fluid inlet nozzle and a converging-diverging outlet nozzle.Water, air, steam, or any other fluid at high pressure provides the motive force at the inlet.
  95. 95. البخار المسحوب من المكثف البخار المستخدم الي الجو Steam nozzle Steam Ejector
  96. 96. HP Steam Vapors from condenser Common Condenser Ejectors Steam Ejector
  97. 97. Speed Governor • A device to control the turbine to adjust the speed chosen by the operator despite the change of load increase it or decrease it is designed on different designs (mechanical, hydraulic, hydraulic / electronic, electrical / electronic). • And this device to control the amount of steam flowing from the valve turbine (main steam control valve) and the by changing its opening, and there governor last for speeding (Over Speed Governor) intervenes when increasing the speed of the turbine suddenly to more than (10%) of the speed controlled to shut off the steam inlet valve. • And get this case when there is a defect in the performance of work which makes it a speed governor is unable to control the turbine
  98. 98. Control System • Hydraulic oil controlling system by control oil ويكون مساره lube oil الخاص بدائره ال PCV من قبل oil pump • وهو يبدأ من طرد كالتالى . وذلك لتعويض اى خلل لحظى فى دائره زيت التحكم accumulator • يوجد عليه • Then divided into Four section 1. To CPC (Current to pressure Converter) 2. Seal steam XV 3. Safety block then to Main steam valve XV 4. To Control valve
  99. 99. ويتكون من Control Oil ان الجزء من هذه الدوائر الذى يخص نظام التحكم هو Wood Ward حاكم السرعه ( I / H ) •محول الطاقه حيث انه يحول اشاره كهربيه الى ضغط زيت وهو ينقسم الى Actuator •مشغل بلف التحكم Oil Relay ) ب servo Motor ) ا حاكم السرعه وهو ياخذ الاشاره الكهربيه بقيمه السرعه المطلوبه ويقارنها بالسرعه الفعليه (I/H) وينتج منها اشاره كهربيه معينه بالزياده او النقصان ويرسلها الى (I/H) CPC المحول فياخذ الاشاره من p1 (control oil) يدخل الى المحول نوعين من الزيت مع هذه الاشاره ويرسله p ويحولها الى ضغط زيت مناسب يسمى 3 W.W الى مشغل بلف التحكم Actuator الخاص بمشغل بلف التحكم بازحه العمود لبلف التحكم servo motor يقوم ال المرسله اليه وبالتالى p ا ا زحه تتناسب مع ضغط الزيت 3 (Control valve) يتم التحكم فى سرعه التربينه Work Of Speed Governor Wood Ward اشارة كهربيه بقيمة السرعه المطلوبه I/H بناءا علي الاشاره الكهربيه يتم خفض ضعط زيت P التحكم الداخل اليه الي 3 Actuator Servo Motor C.Oil P3 MSCV اتجاه الفتح
  100. 100. Control valve arrangement Closing spring V2 + V3 Control valves V1 - V3 Actuator Spindle packing seals live steam pressure of valve chest towards atmosphere #3 #2 #1 Nozzles spring V2 + V3 control valve بلف التحكم التى يمر البخار من خلالها الى الى ريش التربينه وهذه البوابات لها نظام اى ان nozzles ويتكون من بوابتين او ثلاث بوابات متصله بمجموعه من عند الحمل المنخفض فى بدايه التشغيل throttling لايفتح البلف )البوابه( الثانى الا اذا فتح البلف الذى قبله بالكامل وهذا لتلافى حدوث عمليه
  101. 101. servo motor - مشغل بلف التحكم الذى يضغط على مكبس التشغيل ويدفعها فى اتجاه فتح بلف التحكم p وهو عباره عن ياى ومكبس تشغيل ويوجد به فتحه لدخول زيت 1 هو عباره عن مكبس ترحيل وياى oil relay - •فكره عمل بلف التحكم ويدخل ايضا orifice عن طريق ال servo motor الى p يتم اداخال الزيت 1 p حركه مناسبه لسد فتحه ا رجع الزيت 0 Relay لتحريك p طبقا للاشاره المناسبه من حاكم السرعه فيدخل 3 p ضغط زيت 3 بالانخفاض يتحرك مكبس الترحيل p وعندما يتغير ضغط 3 C.V وبالتالى يتحرك مكبس الترحيل فى اتجاه فتح بلف S.M الداخل ال p مما يؤدى الى زياده ضغط 1 عن طريق قوى الياى . C.V وبالتالى يتحرك مكبس التشغيل فى اتجاه غلق S.M زيت التحكم الداخل الى p لفتح ا رجع الزيت مما يقلل من ضغط 1 Actuator Servo Motor Oil Relay
  102. 102. Emergency Stop Valve بلف ايقاف الطوارئ تكون بلوف العزل الموجوده على خط البخار الرئيسى تكون عاده بلوف يدويه ويكون تشغيل ويوجد به ذ ا رع توصيل لنقل القوى التى تقوم بفتح وغلق البلفوبين عمود التوصيل وجسم البلف الذى يتحرك servo motor اج ا زء الفتح والغلق بها اما يدويه او عن طريق خلاله عمود التوصيل هناك مانع تسريب ويكون عليه حشو ولكن بتك ا رر الفتح والغلق يتعرض الحشو للتلف وبالتالى لايؤدى عمله فى ظروف امنه وخاصه عندما يكون عمود التوصيل معرض لعوامل جويه غير ملائمه من اتربه ورطوبه وايضا فى حلات الطوارئ يلزم عزل البخار عن التربينه بسرعه لتامين الماكينه trip system لنتمكن من ايقافها فى حلات ال لذلك وضع بلف ايقاف الطوارئ لان . هذا البلف ليست به اج ا زء ميكانيكيه معرضه للجو اى انه يعمل عن طريق الوسط المحيط لان القوى اللازمه للفتح S.M به وفى هذه الحاله يكون الوسط هو البخار لذلك لايوجد به والغلق تنتج من ضغط الوسط والياى . يعمل هيدروكليا (pilot control device) ويوجد معه جهاز محكم مساعد ويلزم فىعمليه فتح وغلق البلف ايقاف الطوارئ Main cone Pilot cone Sleeves Closing springs
  103. 103. Lifting of guide-blade carrier top half Removal of turbine rotor and guide-blade carrier bottom half Scope of Major Overhaul
  104. 104. Operation and maintenance • When warming up a steam turbine for use, the main steam stop valves (after the boiler) have a bypass line to allow superheated steam to slowly bypass the valve and proceed to heat up the lines in the system along with the steam turbine. • Also, a turning gear is engaged when there is no steam to the turbine to slowly rotate the turbine to ensure even heating to prevent uneven expansion. • After first rotating the turbine by the turning gear, allowing time for the rotor to assume a straight plane (no bowing), then the turning gear is disengaged and steam is admitted to the turbine, first to the astern blades then to the ahead blades slowly rotating the turbine at 10–15 RPM (0.17–0.25 Hz) to slowly warm the turbine.
  105. 105. • Any imbalance of the rotor can lead to vibration, which in extreme cases can lead to a blade breaking away from the rotor at high velocity and being ejected directly through the casing. To minimize risk it is essential that the turbine be very well balanced and turned with dry steam - that is, superheated steam with a minimal liquid water content. • If water gets into the steam and is blasted onto the blades (moisture carry over), rapid impingement and erosion of the blades can occur leading to imbalance and catastrophic failure. Also, water entering the blades will result in the destruction of the thrust bearing for the turbine shaft