ENERGY CENTRE2X55MW

TURBINE TG COOLING TOWER STEAM SYSTEM

ELECTRICAL SYSTEM132KV SWITCH YARD

11KV CONTRACT DEMAND

CAPTIVE POWER PLANT (2 X 55 MW)

STEAM TURBINE • TURBINE CONSTRUCTION• TURBINE SYSTEM • TURBINE OPERATION• TURBINE PROTECTION

INTRODUCTION TO 2X55 MW LMZ (LENINGRADSKY METALLIEHESKY ZAVOD)

The turbine is a single cylinder single shaft unit to be mounted on a common foundation with the generator. the rated power out put of 55mw, for this following basic parameters:

• Absolute live steam pressure before esv 60 kgf/cm2

• Live steam temperature 475 º c • Rated consumption of live steam 209.5 ton/hour

• Absolute pressure in the condenser 0.11 kgf/cm2

• Normal cooling water temperature 35 º c• Nominal flow rate of cooling water via the

condenser 12200 ton/hour.

TURBINE CONSTRUCTION NOZZLE• The turbine has a nozzle steam distribution.

the segments of the nozzles of the first (regulating) stage are mounted in nozzle box. steam having passed the regulating stage and 17 intermediate stage of pressure, get into the condenser

CYLINDER• Cylinder consists of two parts. the front part

is casted and the rear exhaust part is welded of steel plates. both parts are coupled with vertical joint.

DIAPHRAGM• Diaphragms of flow path of the cylinder

are mounted in 5 diaphragm holders. all the diaphragms are welded steel.

• The overbandage packings of the regulating stage are fitted in the deflector of diaphragm holder number 1.

• The diaphragm packing are designed as rows of stepped borings on the rotor fitted in the diaphragm boring are packing segments of the diaphragm packing.

TURBINE CYLINDER MOUNTING• The front part of the turbine cylinder rest

with its support surface on transverse keys mounted on the case of the front bearing.

• During thermal expansion of the turbine cylinder, the front bearing case is free to travel across the bed frame in the longitudinal direction.

• The fixing point of turbine cylinder is located on the rear bed frame so that cylinder expansion is toward the front bearing and approximately up to 14 mm.

TURBINE ROTOR• Turbine rotor is one piece forged of cr, mo,

v steel. ROTOR BLADE• These are most important (and costly too)

components of the turbine as these are responsible for the main function of the turbine, i.e. converting heat energy to mechanical energy.

Turbine Rotor Coupling • The turbine rotor is flexible, i.e. the

operating speed exceeds the first critical speed of turbine rotor. The turbine rotor and the generator are joined with a rigid coupling. The sense of rotation of the rotor is clockwise when seen from the front bearing facing the generator.

TURBINE ROTOR RESTING • Turbine rotor rest on two bushing the front bearing Turbine rotor rest on two bushing the front bearing

case comprises the front thrust/support bushing case comprises the front thrust/support bushing φ 270 mm, serving as a fixing point for the turbine φ 270 mm, serving as a fixing point for the turbine rotor and the generator rotor and ensuring their rotor and the generator rotor and ensuring their expansion towards the generatorexpansion towards the generator. .

SAFETY VALVE OF TURBINE• Mounted on the cover of the cylinder exhaust part

are two safety valves of a membrane type opening at an increase of the absolute pressure in the cylinder’s exhaust part up to 1.2 kgf/cm2

LABYRINTH GLAND• Gland are used on turbine to prevent or

reduce the leakage of steam or air between rotating and stationary component which have a pressure difference across them; this applies particularly where the turbine shaft passes through the cylinder.

• If the cylinder pressure is higher than atmospheric pressure there will be a general steam leakage outwards; if the cylinder is below atmospheric pressure there will be a leakage of air inward and some sort of sealing system must be used to prevent the air from entering the cylinder and the condenser.

SHAFT TURNING (BARRING) GEAR

• Turning gear is provided to rotate the turbine shaft slowly (at 3.4 r.p.m.) during the pre run up operation and after shut down to prevent uneven heating or cooling of the shaft.

• The uneven heating or cooling would lead to bending and misalignment of shaft with possible fouling of stationary and moving part.

• TURNING GEAR PROVIDE THE AIR CIRCULATION WITHIN THE CASING PARTICULARLY AT THE LOW PRESSURE END AFTER SHUT DOWN.

• THE TURBINE MUST REMAIN ON

TURNING GEAR UNTIL METAL TEMPERATURE HAS DROP BELOW 150° C WITH NORMAL COOLING, THIS WILL TAKE APPROXIMATELY 72 HOURS.

TURBINE SYSTEM• OIL SYSTEM• CONDENSATE SYSTEM• COOLING WATER SYSTEM• VACUUM AND GLAND SEALING

SYSTEM• DRAIN SYSTEM

OIL SYSTEM THE TURBINE OIL SYSTEM FULFILS

FOLLOWING FUNCTIONS. (a) provides a supply of oil to the journal

bearing to give an oil wedge at the shaft rotors.

(b) maintains the temperature of the turbine bearing constant at the required level. the oil does this by removing the heat which is produced by the shaft conduction, the surface friction and the turbulence in the oil.

(c) Provides a medium for hydraulically operating the governor gear and controlling the steam admission valves.

OILTANK• The oil tank having a capacity of 14 m3 in

capacity is made of two layer corrosion resistance steel and serves to store oil and clean it of mechanical impurities water and air and is a supporting structure for pump.

FUNCTION OF CONDENSER • To provide lowest economic heat rejection

temperature for the steam. thus saving on steam required for unit electricity.

• To convert exhaust steam to water for reuse thus saving on feed water requirement.

• The condensate is collected in hotwell and with the help of 3 condesate extraction pump (having capacity 125 m3 /hr) condensate is send to condensate polish tank.

VACUUM AND GLAND SYSTEM

WHY VACUUM IS NECESSARY?• We know that output of a turbine is the

product of (efficiency × pressure drop × enthalpy drop) so when we plot p-h diagram we see that if we able to increase enthalpy drop & pressure drop we can get maximum output of turbine i.e. exhaust pressure should be decreased which is only possible by the help of vacuum in condenser.

EQUIPMENT USED FOR MAINTAINING VACUUM

• Air extraction equipment is used to extract air and other non condensable gases from the condenser for maintaining vacuum.

• During starting of turbine large amount of air is required to be extracted from condenser while during normal operation quantity of air to be extracted is lower.

DRAIN SYSTEM• In order to remove condensate from the

turbine cylinder and from the pipe lines during start up and warm up drain system is provided and all the condensate from different point of turbine system is collected in h.p. & l.p. flash tank. this h.p. & l.p. flash tank is connected with condenser.

TURBINE OPERATION THERE ARE TWO TYPES OF TURBINE

START UP PROCEDURE.• Cold start up (if casing metal temperature is

less than 170º c)• Hot start up (if casing metal temperature is

more than 170º c)

COLD STARTUP

VACUUMS PULLING

TURBINE HEATING

TURBINE ROLLING

LOADING

SYNCHRONIZING

Vacuum pulling

Ensure c w system is running normal

Ensure turbine lube oil system is running normal

Ensure turbine rotor is on barring gear &normal

Ensure MSV ,RV, VACUUM BRAKER,DRAIN,CLOSED

Checked vacuum protection reset & sufficient vacuum in condenser

Stop the startup ejector

Charged steam to gland steam ejector &startup ejector and rises the vacuum up to 70 K Pa, then main ejector ,then sealing to turbine ,see that vacuum steadily rising

Charged the PRDS &adjust pr. 6kg/cm²&temp 200ºC

TURBINE HEATING

CHECK THAT ALL PRE START REQUIREMENT ARE OVER

CHECK THAT HEADER PR 60KG/CM² TEM. 475ºC

CHECK ESV, RV IS CLOSED

OPEN THE BYPASS ISOLATION AND IT CONTRAL VALVE

OPEN THE DRAIN OF CROSSEROVER PIPE

OPEN THE ESV AND HEAT THE CROSSOVER PIPE

HEAT THE ESV

TURBINE ROLLING

CHECK METAL TEMP,STEAM PR,&TEMP.DIFFERENTIAL- EXPANSION,AXIAL SHIFT,ECCENTRICITY

THEN TO 3000 RPM

THEN TO 2000 RPM

THEN TO 1200 RPM

SLOWLY INCRESED TO 500RPM

SYNCHRONIZING & LOADING

EXCITATION ON

SWITCH ON THE AVR

GRADUALLY BUILT VOLTAGE

MATCH THE VOLTAGE ,FREQUENCY,PHASE ANGLE BETWEEN TG AND GRID

GIVE POWER CLERANCE TO PLANT ACCORDING TO THE AVAILABILITY OF THE STEAM

SHUT DOWN OF TURBINE

GRADUALLY REDUCE LOAD FROM TURBINE TO NO LOAD

OPEN THE GENERATOR CIRCUIT BREAKER

SWITCH OFF THE AVR

GIVE SHUT DOWN COMMAND MANUALLY

AS SOON AS THE TURBINE REACHES TO ZERO R.P.M. START BARRING

AT 1000 R.P.M. START JACKING OIL PUMP

AT 2000 R.P.M. BREAK VACUUM

CHECK THE R.P.M. REDUCING GRADUALLY

TURBINE WILL BE ON BARRING (3.4 R.P.M.) UNTILLTHE CASING METAL TEMPERATURE REDUCED TO <150º C

TURBINE HEATING RATE METAL TEMPERATURE METAL TEMPERATURE

RANGES ºC INCREASE RATE ºC/MMFROM 100 TO200 4FROM 200 TO 300 3FROM 300 TO 400 2

FROM 400 TO 475 1 .

TURBINE ROLLING

• SOAKING METHOD

In this method the machine is given a soaking time just before the critical speed. e.g.. the turbine is rolled 500 rpm and hold at this speed for 15 minutes, again at 2000 rpm is hold for 45 minutes ,at 3000 rpm soaking time of 30 minutes is given.

• CONSTANT ACCELERATION METHOD

m/c is rolled and speed is increased at a constant rate (the acceleration rate should be as per manufacturers guidance)

TURBINE PROTECTION• 1. TURBINE OVER SPEED PROTECTION• 2. AXIAL SHIFT• 3. PRESSURE IN CONDENSER• 4. LUBE OIL PRESSURE• 5. LIVE STEAM TEMPERATURE• 6. GENERATOR PROTECTION• 7. MANUAL TRIP

AREA MAX.LOAD RUNNING LOAD STARTUP LOADD AP 12.3 11.5 .3P AP 19.8 18.0 2.6 SAP 3.0 2.8 1.4U/O 3.5 2.8 2.3CONVEYAR 3.2 2.7 0AMMONIA 1.6 1.3 .7E/C 9.9 7.5 4.5TOTAL 53.3 46.68 11.8

• EFFECT OF PRESSURE & TEMPERATURE

• But due to certain metallurgical constraint steam temperature is restricted up to 620 ºC.

• If the moisture content of steam in the latter stages of turbine is high, the entrained water particles along with the vapour coming out of the nozzle with high velocity strike the blades and erode their edges, as a result life of turbine blades decreased.

• So the maximum moisture content at turbine exhaust is not allowed to exceed beyond 12%. With the increase in pressure latent heat required for evaporation in boiler is reduced.

• EFFICIENCY OF VARIOUS GENERATING SYSTEM

Generation type Unit Size Thermal Efficiency MW %

Steam 200 – 800 30 – 40Nuclear 500 -1100 31 – 34Gas turbine 50 – 100 22 - 28Combined turbine 300 – 600 36 – 50Diesel Engine 10 – 30 27 - 30

STEAM DISTRIBUTION OBJECTIVE• The objective of the steam distribution system is

to supply steam at the correct pressure to the point of use.

• The steam distribution system is the essential link between the steam generator and the steam user.

• Whatever the source, an efficient steam distribution system is essential if steam of the right quality and pressure is to be supplied, in the right quantity, to the steam using equipment

• STEAM DISTRIBUTION AT VARIOUS PRESSURE AND TEMP ACCORDING TO THE REQUIREMENT OF VARIOUS UNIT OF PLANT IS DONE THROUGH STEAM SYSTEM

• SOURCE OF STEAM at 60 kg/cm² and temp. 475± 5ºc• A.F.B.C 2X110 TPH• S.AP 2X175 TPH• DISTRIBUTION OF STEAM• HP Steam – TG , TURBO BLOWER, BFW Pump ,

CP Pump• MEDIUM PRESSURE –( 16kg/cm²,temp 210ºc) MP to PAP and DAP for Circulator, Evaporators & PN• LOW PRESSURE STEAM –( 2kg/cm²,temp 132ºc) LP steam to PAP & DAP for Evaporators &Ammonia

vaporization.

INTRODUCTION Steam has been a popular mode of conveying

energy. The following characteristics of steam make it so popular and useful to the industry:

• Highest specific heat and latent heat • Highest heat transfer coefficient • Easy to control and distribute • Cheap and inert

FEATURES OF STEAM PIPING• Steam pipes should be laid by the shortest

possible distance rather than to follow a building layout or road etc.

• Apart from proper sizing of pipe lines, provision must be made for proper draining of condensate which is bound to form as steam travels along the pipe.

• These drain pockets should be provided at every 30 to 50 meters and at any low point in the pipe network. The pocket should be fitted with a trap to discharge the condensate.

• Necessary expansion loops are required to take care of the expansion of pipes when they get heated up.

• Proper sizing of steam pipelines help in minimizing pressure drop. The velocities for various types of steam are:

• Superheated 50–70 m/sec

• Saturated 30–40 m/sec

• Wet or Exhaust 20–30 m/sec

• The steam piping should be sized, based on permissible velocity and the available pressure drop in the line. Selecting a higher pipe size will reduce the pressure drop and thus the energy cost. However, higher pipe size will increase the initial installation cost.

• By use of smaller pipe size, even though the installation cost can be reduced, the energy cost will increase due to higher-pressure drop. It is to be noted that the pressure drop change will be inversely proportional to the 5th power of diameter change. Hence, care should be taken in selecting the optimum pipe size.

. AVOIDING STEAM LEAKAGES• Steam leakage is a visible indicator of waste and must be

avoided. • It has been estimated that a 3 mm diameter hole on a

pipeline carrying 7 kg/cm2 steam would waste 33 KL of fuel oil per year.

• Steam leaks on high-pressure mains are prohibitively costlier than on low pressure mains. Any steam leakage must be quickly attended to.

• In fact, the plant should consider a regular surveillance programme for identifying leaks at pipelines, valves, flanges and joints.

•

• Indeed, by plugging all leakages, one may be surprised at the extent of fuel savings, which may reach up to 5% of the steam consumption in a small or medium scale industry or even higher in installations having several process departments.

• To avoid leaks it may be worthwhile considering replacement of the flanged joints which are rarely opened in old plants by welded joints

• Utilising Steam at the Lowest Acceptable Pressure for the Process

• A study of the steam tables would indicate that the latent heat in steam reduces as the steam pressure increases. It is only the latent heat of steam, which takes part in the heating process when applied to an indirect heating system. Thus, it is important that its value be kept as high as possible. This can only be achieved if we go in for lower steam pressures.

• As a guide, the steam should always be generated and distributed at the highest possible pressure, but utilized at as low a pressure as possible since it then has higher latent heat.

• Limit to reduction in pr.• However, it may also be seen from the

steam tables that the lower the steam pressure, the lower will be its temperature. Since temperature is the driving force for the transfer of heat at lower steam pressures, the rate of heat transfer will be slower and the processing time greater.