Download - 94649631 Vacuum System
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Turbine VacuumSystem
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Presentation outline Why Vacuum system is required ?
Parts of Vacuum system?
Steam Ejectors
Vacuum Pumps
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Why is it required? The steam turbine itself is a device to
convert the heat in steam to mechanical
power.
Enthalpy drop across the turbine decides
the work output of the turbine. For
increasing this enthalpy drop across the
turbine we need effective condenservacuum system.
http://en.wikipedia.org/wiki/Steam_turbinehttp://en.wikipedia.org/wiki/Heathttp://en.wikipedia.org/wiki/Steamhttp://en.wikipedia.org/wiki/Power_%28physics%29http://en.wikipedia.org/wiki/Power_%28physics%29http://en.wikipedia.org/wiki/Steamhttp://en.wikipedia.org/wiki/Heathttp://en.wikipedia.org/wiki/Steam_turbinehttp://en.wikipedia.org/wiki/Steam_turbinehttp://en.wikipedia.org/wiki/Steam_turbine -
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By condensing the exhaust steam ofturbine, the exhaust pressure is brought
down below atmospheric pressure,
increasing the steam pressure drop
between inlet and exhaust ofsteam turbine.This further reduction in exhaust pressure
gives out more heat per unit weight of
steam input to the steam turbine, for
conversion to mechanical power.
http://en.wikipedia.org/wiki/Steamhttp://en.wikipedia.org/wiki/Atmospheric_pressurehttp://en.wikipedia.org/wiki/Steam_turbinehttp://en.wikipedia.org/wiki/Steamhttp://en.wikipedia.org/wiki/Steam_turbinehttp://en.wikipedia.org/wiki/Steam_turbinehttp://en.wikipedia.org/wiki/Steam_turbinehttp://en.wikipedia.org/wiki/Steam_turbinehttp://en.wikipedia.org/wiki/Steamhttp://en.wikipedia.org/wiki/Steam_turbinehttp://en.wikipedia.org/wiki/Steam_turbinehttp://en.wikipedia.org/wiki/Steam_turbinehttp://en.wikipedia.org/wiki/Atmospheric_pressurehttp://en.wikipedia.org/wiki/Atmospheric_pressurehttp://en.wikipedia.org/wiki/Atmospheric_pressurehttp://en.wikipedia.org/wiki/Steam -
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Parts of Vacuum System
Condenser
CW system
Ejectors/Vacuum pumps
Gland Sealing System
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CondenserSteam from last stage
of LPT Exhausts on
condenser tube
condensation of
steam takes place
Water collected in hot
well
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Shell of the Condenser
The shell is the outer most body of the condenser shell is fabricated from fairly thick carbon steel plates.
Due to its large size the shell is sufficiently
strengthened or stiffened internally with carbon steel
plates to give sufficient rigidity for the shell proper. The shell also gives support to number of intermediate
support plates for the long tubes, depending on the size
of the condenser.
At the same time the intermediate tube support platesallow for the free movements of tubes in all directions
particularly lengthwise due to expansion and
contraction occurring during operation.
http://en.wikipedia.org/wiki/Carbon_steelhttp://en.wikipedia.org/wiki/Expansionhttp://en.wikipedia.org/wiki/Contractionhttp://en.wikipedia.org/wiki/Contractionhttp://en.wikipedia.org/wiki/Expansionhttp://en.wikipedia.org/wiki/Carbon_steelhttp://en.wikipedia.org/wiki/Carbon_steelhttp://en.wikipedia.org/wiki/Carbon_steel -
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The whole condenser is supported on heavy springs,
mounted on steel sole plates at suitable places on theconcrete foundation
At the bottom of the shell where the condensate isallowed to collect, a sump (often referred to as the
hotwell) is provided. This sump is common to both the halves but separated
by a partition wall in the middle up to the height of thebottom row of tubes.
The inside of shell and outside the tubes as a whole
remains undervacuum under normal operatingconditions. Inside the tubes the cooling or circulatingwater passes through.
http://en.wikipedia.org/wiki/Spring_%28device%29http://en.wikipedia.org/wiki/Vacuumhttp://en.wikipedia.org/wiki/Vacuumhttp://en.wikipedia.org/wiki/Spring_%28device%29 -
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Air Zone Inside the shell, a central or side portion
longitudinally is separated by an outershield except at the bottom. This partitionis called the Air zone.
All the gases released in the condenserdue to cooling are taken out via these airzone tubes.
From a suitable portion of this air zoneinside the shell an air vent pipe is takenout and brought out of the shell forconnection to an airextraction device.
http://en.wikipedia.org/wiki/Extractionhttp://en.wikipedia.org/wiki/Extraction -
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Tube Sheets At each end of the shell, tube sheet of sufficient
thickness is provided, with holes for the tubes
to be inserted and rolled. To take care of length wise expansion of tubes
some designs have expansion joint between the
shell and the tube sheet allowing the latter to
move longitudinally.
http://en.wikipedia.org/wiki/Tubehttp://en.wikipedia.org/wiki/Tubehttp://en.wikipedia.org/wiki/Expansionhttp://en.wikipedia.org/wiki/Butterfly_valvehttp://en.wikipedia.org/wiki/Butterfly_valvehttp://en.wikipedia.org/wiki/Expansionhttp://en.wikipedia.org/wiki/Tubehttp://en.wikipedia.org/wiki/Tube -
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Water Boxes The tube sheet at each end with tube ends rolled, for
each half condenser is enclosed in a fabricated boxknown as water box.
These water boxes on inlet side will also have big size
flanged connections for cooling water inlet at lowerlevel forbutterfly valves.
small vent pipe with hand valve for air venting athigher level, and hand operated drain valve at bottomto drain the water box for maintenance.
Similarly thermometerpockets are located at inlet andoutlet pipes for local measurements cooling watertemperature.
http://en.wikipedia.org/wiki/Valvehttp://en.wikipedia.org/wiki/Thermometerhttp://en.wikipedia.org/wiki/Brasshttp://en.wikipedia.org/wiki/Cupro_nickelhttp://en.wikipedia.org/wiki/Cupro_nickelhttp://en.wikipedia.org/wiki/Brasshttp://en.wikipedia.org/wiki/Thermometerhttp://en.wikipedia.org/wiki/Valvehttp://en.wikipedia.org/wiki/Valvehttp://en.wikipedia.org/wiki/Valve -
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Tubes Generally the tubes are made of brass,
aluminum brass, cupro nickel, stainless steel ortitanium depending on the cooling water
chemistry. The lengths are fixed at about 20 ft (6 m) (for the
200 MW device mentioned above), dependingon the size of the condenser.
The outer diameter is limited to a maximum ofone inch for ease of handling and ease ofinsertion through the shell tube holes and forrolling at both ends.
http://en.wikipedia.org/wiki/Stainless_steelhttp://en.wikipedia.org/wiki/Titaniumhttp://upload.wikimedia.org/wikipedia/en/2/25/Dores-Cond-diag1.pnghttp://localhost/var/www/apps/conversion/Documents%20and%20Settings/Siva/Desktop/2BE3%20how%20it%20works.swfhttp://localhost/var/www/apps/conversion/Documents%20and%20Settings/Siva/Desktop/2BE3%20how%20it%20works.swfhttp://upload.wikimedia.org/wikipedia/en/2/25/Dores-Cond-diag1.pnghttp://upload.wikimedia.org/wikipedia/en/2/25/Dores-Cond-diag1.pnghttp://upload.wikimedia.org/wikipedia/en/2/25/Dores-Cond-diag1.pnghttp://en.wikipedia.org/wiki/Titaniumhttp://en.wikipedia.org/wiki/Titaniumhttp://en.wikipedia.org/wiki/Titaniumhttp://en.wikipedia.org/wiki/Stainless_steel -
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CW system
CW pumps supply cooling
water to condensers
CW maintains vacuum in
condensers
CW flows through
condensers tubes
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STEAM EJECTORS Air and water vapor are removed from the
main steam condenser, enter the 1st stageejector and are compressed to the interstagepressure by means of the high pressure
motive steam. The load and motive steam are discharged
to the inter condenser and a portion of thewater vapor load and motive steam are
condensed by condensate from the maincondenser.
Non-condensibles and associated watervapor are removed from the inter condenser
by the 2nd stage ejector.
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STEAM EJECTORS
Motive
steam
Non condensibile gases and
water vapour from condenser
Convergent
divergent
diffuser
Nozzle
D
ischargeto
co
ndenser
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STEAM EJECTORS Multistage condensing ejector systems can be
designed to operate at any condenser pressure and
designs are not limited by the available cooling
water temperature to the intercondenser
(condensate cooled systems are common).
These systems have no moving parts, are the most
reliable, require the least maintenance of all venting
systems, and are the least expensive in initial cost.
Once equipment is built for a given motive steampressure that pressure must be maintained or the
ejector will become unstable and lose vacuum.
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STEAM EJECTORS
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EJECTORS MAIN AIR EJECTOR
STARTING AIR EJECTORS
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Ejectors
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VACUUM PUMPS The liquid-ring vacuum pump is a specific form of
rotary positive-displacement pump utilizing liquidas the principal element in gas compression.
The working parts of the liquid ring vacuum pumpconsist of a multi-bladed impeller mountedeccentrically in a round casing which is partlyfilled with liquid. As the impeller rotates, theliquid is thrown by centrifugal force to form a
liquid ring which is concentric with the peripheryof the casing.
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LRVPSuction port
Impeller
Gas vapour
mixture Liquid ring
Casing
Discharge port
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LRVP In addition to being the compressing
medium, the liquid ring absorbs the heatgenerated by compression and friction,absorbs any liquid slugs or vapor enteringwith the gas stream, and condenses watervapor entering with the gas.
A closed loop (or total recirculation) sealsystem is commonly used. The seal watertemperature warmer than the cooling waterto the pump heat exchanger, which isnormally taken from the same source as thecondenser cooling water (CW or ARCW).
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LRVPSeparator
vent
Non condensible gases and
water vapour from condenser
Cooling
water
Liquid ring vacuum pump system
Seal water
LRVP
Seal cooler
Makeup
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LRVP The vacuum attainable by a liquid ring vacuum pump is
limited by the vapor pressure of the seal fluid.
As the operating vacuum approaches the vaporpressure of the seal, more and more of the seal fluid willflash into vapor.
The capacity of the liquid ring vacuum pump is reducedas more of the impeller space is occupied by vapor fromthe seal fluid, leaving less space available to accept theincoming load.
If allowed to continue, cavitation will occur inside thepump, resulting in damage to internal surfaces, andpreventing the pump from achieving greater vacuumlevels.
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