STEAM TURBINE POWER PLANT Muhammad Taha (EE106013) Faisal Iqbal Khan Group Members: H. M. Furqan (EE106024) Muhammad Taha (EE106013) Faisal Iqbal Khan (EE306071)

DEFINITION Turbines are used in  systems to convert kinetic energy of  fluid to mechanical energy

Steam Turbine Power Plant hot gases superheated steam compressed water Steam Generator Steam Turbine C Pump Gen Condenser saturated water saturated steam cooling water

The Simple Steam Power Plant

Steam Turbine to produce Electricity Oil could be used instead of coal.

CHOICE OF STEAM TURBINE The choice of steam turbine depends on the following factors : (i) Capacity of plant (ii) Plant load factor and capacity factor (iii) Thermal efficiency (iv) Reliability (v) Location of plant with reference to availability of water for condensate.

Construction Rotor  Blades or Buckets Nozzles Bearing

Turbine Blades(Buckets) FIXED BLADES: These are constructed in halves. Fixed blades have a convergent nozzle shape. MOVING BLADES: These can be shaped either in reaction or impulse. The K.E is transferred to a row of moving blades. Moving blades converts this K.E in to mechanical energy by rotation.

Rotor

Nozzle

Nozzle

Bearing

Bearing

Impulse Turbine Basic Priciple The toy pinwheel can be used to study some of the basic principles of turbines. when you blow on the rim of the wheel, it spins rapidly the harder you blow the faster it run.

IMPULSE TURBINE An impulse turbine has fixed nozzles that orient the steam flow into high speed jets. A pressure drop occurs across only the stationary blades, with a net increase in steam velocity across the stage. The steam leaves the nozzle with a very high velocity The steam leaving the moving blades is a large portion of the maximum velocity of the steam when leaving the nozzle

Impulse Turbine

Basic Principle of Reaction Turbine Reaction turbine is built on principle of Newton’s third law of motion which state: For every action there must be an equal and opposite reaction

REACTION TURBINE 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. 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

Comparision of Impulse and Reaction Turbine In case of an impulse turbine the pressure remains same in the rotor,but in case of reaction turbine the pressure decreases in rotor as well as stators also. In case of impulse turbine the pressure drop happens only in the nozzle part by means of its kinetic energy. In case of Reaction one the stators those are fixed to the diaphragm act as a nozzle.

Main Componets of Turbine TANDUM COMPOUND: The different cylinders(HP-IP and LP cylinders) mounted over one common shaft to derive a generator is called the tendum compound. SHROUDING: A metal band along the outer rim of the blading is called a shrouding, which ties the blading together. STAGE: One row of moving and one row of fixed blade is called a stage.

Bearings keep the rotor in its correct axial position. The rotor assembly consists of turbine shaft and attached moving blades. CYLINDER: A turbine rotor assembly and casing as a unit is called a cylinder. BEARINGS: Bearings keep the rotor in its correct axial position.

TURNING GEAR: Function of turning gear is to keep the turbine turning during startup and shut down periods. EXHAUST HOOD COOLING SYSTEM: This system is designed to reduce the stresses on turbine parts that could result from exposures to high temperatures GLAND STEAM SEALING: The steam is admitted to the rotor glands to prevent air ingress to LP turbine and steam leak out from HP-IP rotor glands.

Main stop valves Governing valves TURBINE VALVES MSV pilot valves open and steam enters in chest by full arc admission. Its for proper warming of steam chest Governing valves Valve transfer takes place, control shifts from MSV s’ to GV s Interceptor valves ICV regulates or shuts off the steam flow rate during emergency or shut down. Starts to close on overspeeding.

ECCENTRICITY: The amount that rotor deviates from its normal center of rotation. It will be active up to 600 rpm. ROTOR POSITION: Rotor position indicator indicates relative movement between thrust bearing collar and thrust bearing pedestal. VIBRATION: The radial movement of the shaft is measured in terms of vibration. The excessive vibration will cause shaft and seal wear and bearing damage.

PROTECTIVE DEVICE Following protective device must be carried out on monthly basis. Over speed test. Condenser vacuum low trip. Bearing oil pressure low trip. Thrust bearing wear trip.

STEAM TURBINE CAPACITY The capacities of small turbines and coupled generators vary from 500 to 7500 kW whereas large turbo alternators have capacity varying from 10 to 90 mW. Very large size units have capacities up to 500 mW. Generating units of 200 mW capacity are becoming quite common. The steam consumption by steam turbines depends upon steam pressure, and temperature at the inlet, exhaust pressure number of bleeding stages etc. The steam consumption of large steam turbines is about 3.5 to 5 kg per kWh.

STEAM TURBINE CAPACITY (CONT) Turbine kW = Generator kW / Generator efficiency Generators of larger size should be used because of the following reasons: (i) Higher efficiency. (ii) Lower cost per unit capacity. (iii) Lower space requirement per unit capacity. 3.45.1 Nominal rating. It is the declared power capacity of turbine expected to be maximum load.

CAPABILITY The capability of steam turbine is the maximum continuous out put for a clean turbine operating under specified throttle and exhaust conditions with full extraction at any openings if provided. The difference between capability and rating is considered to be overload capacity. A common practice is to design a turbine for capability of 125% nominal rating and to provide a generator that will absorb rated power at 0.8 power factor. By raising power factor to unity the generator will absorb the full turbine capability.

ADVANTAGES OF STEAM TURBINE It requires less space. Absence of various links such as piston, piston rod, cross head etc. make the mechanism simple. It is quiet and smooth in operation, Its over-load capacity is large. It can be designed for much greater capacities as compared to steam engine. Steam turbines can be built in sizes ranging from a few horse power to over 200,000 horse power in single units

ADVANTAGES OF STEAM TURBINE (cont) The internal lubrication is not required in steam turbine. This reduces to the cost of lubrication. In steam turbine the steam consumption does not increase with increase in years of service. In steam turbine power is generated at uniform rate, therefore, flywheel is not needed. It can be designed for much higher speed and greater range of speed. The thermodynamic efficiency of steam turbine is higher.

SPECIFICATION Type………………………………….. Single reheat condensing tandem two cylinder double flow exhaust MCR…………………………………. 362 MW Speed……………………………….… 3000 rpm Direction of rotation………………..... clockwise (from GV end) Inlet pressure……………………….... 169kg/cm2 Inlet temperature…………….….…… 538 C0 (Main steam and reheat) Exhaust pressure ………………….… 692 mmHg No of Extractions………………….… 8 Blading: HP Turbine……………….Impulse ………1 Stage (Rateau). Reaction………11Stages. IP Turbine……………….. Reaction………10 Stages. LP Turbine……………….Reaction………..6 Stages.

Main steam and hot reheat steam (Turbine Inlet) + 8 0 C + 14 0 C APPLICATION LIMIT ALARM/TRIP REMARKS Main steam and hot reheat steam (Turbine Inlet) + 8 0 C + 14 0 C + 28 0 C Max allowable temperature Emergency Allowable Max In A amount With in 400 hrs in a year With in 15 minutes continuously & 80 hrs a year Main steam Pressure (Turbine Inlet) +5 % +10 % +20 % Mean allowable for continous operation. Maximum allowable for continous operation. Max Emergency allowable. With in 12 hrs in a year.

Journal bearing metal temperature 107 0 C 113 0 C Alarm Trip APPLICATION LIMIT ALARM/TRIP REMARKS Journal bearing metal temperature 107 0 C 113 0 C Alarm Trip Thrust bearing metal temperature 99 0 C Bearing oil drain temperature 77 0 C Exhaust Hood Temp. 80 0 C 70 0 C 120 0 C Spray set point

Bearing oil temp. at exit of oil cooler 50 0 C APPLICATION LIMIT ALARM/TRIP REMARKS Condenser Vacuum 692 mm Hg 635 mmHg 500 mmHg Normal Alarm Trip Vacuum Breaker < 400 rpm Over speed trip. < 111 % Valve stem free test 75 % load Bearing oil temp. at exit of oil cooler 50 0 C

Differential expansion - 1.7 – 15.8 mm APPLICATION LIMIT ALARM/TRIP REMARKS Eccentricity 0.075 mm Alarm 0 – 600 rpm Rotor Vibration 0.125 mm 0.25 mm Trip Rotor Position + 0.9 mm + 1 mm + thrust side. - Anti thrust side. Thrust bearing wear 2.1 Kg/cm2 5.6 Kg/cm2 Differential expansion - 1.7 – 15.8 mm

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