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Condenser for Marine Boiler Feed System & Steam Turbines

The condenser is a heat exchanger which removes the latent heat from exhaust steam so that it condenses and can be pumped back into the boiler. This condensing should be achieved with the minimum of under-cooling, i.e. reduction of condensate temperature below the steam temperature. A condenser is also arranged so that gases and vapours from the condensing steam are removed.

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It is also required to reduce the back pressure and so allowing a greater amount of work to be done by the engine, improving efficiency. An auxiliary condenser is shown in Figure below. The circular cross-section shell is provided with end covers which are arranged for a two-pass flow of sea water. Sacrificial corrosion plates are provided in the water boxes.

The steam enters centrally at the top and divides into two paths passing through ports in the casing below the steam inlet hood. Sea water passing through the banks of tubes provides the cooling surface for condensing the steam.

The central diaphragm plate supports the tubes and a number of stay rods in turn support the diaphragm plate. The condensate is collected in a sump tank below the tube banks. An air suction is provided on the condenser shell for the withdrawal of gases and vapours released by the condensing steam.

Auxiliary feed system

Fig:Auxiliary feed system


Main condensers associated with steam turbine propulsion machinery are of the regenerative type. In this arrangement some of the steam bypasses the tubes and enters the condensate sump as steam. The condensate is thus reheated to the same temperature as the steam, which increases the efficiency of the condenser. One design of regenerative condenser is shown in Figure .

A central passage enables some of the steam to pass to the sump, where it condenses and heats the condensate. A baffle plate is arranged to direct the gases and vapours towards the air ejector. The many tubes are fitted between the tube plates at each end and tube support plates are arranged between. The tubes are circulated in two passes by sea water.

The feed system completes the cycle between boiler and turbine to enable the exhausted steam to return to the boiler as feedwater. The arrangements for steam recovery from auxiliaries and ship services may form separate open or closed feed sysems or be a part of the main feed system.

The two principle types of condenser are:
  1. Surface : in the surface type, there is a temperature drop of about 8°C from inlet to outlet and the condensate and air leave from the bottom


  2. Regenerate : in this type, steam flowing along the regenerative passage and up into the tube nest heats the condensed droplets from the tubes so there is practically no temperature drop in the condenser. Air trapped by the exhaust baffles is extracted separately by an ejector.



Summarized below more guidance for marine feed system:
  1. Sketch and explain an `End on' or axial exhaust regenerative condenser


  2. Open feed system for an auxiliary boiler - how it works
    3. In open feed system for an auxiliary boiler , the exhaust steam from the various services is condensed in the condenser. The condenser is circulated by sea water and may operate at atmospheric pressure or under a small amount of vacuum. The condensate then drains under the action of gravity to the hotwell and feed filter tank....


    More .....

  3. Closed feed system for an auxiliary boiler - operating principle
    4. A closed feed system for a high pressure watertube boiler supplying a main propulsion steam turbine is shown in Figure above. The steam turbine will exhaust into the condenser which will be at a high vacuum.

    More.....

  4. How De-aerator works in a boiler feed system
    5. The de-aerator completes the air and vapour removal process begun in the condenser. The condenser is a heat exchanger which removes the latent heat from exhaust steam so that it condenses and can be pumped back into the boiler

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  5. Heat exchangers in a boiler feed system /steam turbines
    6. The gland steam condenser, drains cooler and low-pressure feed heater are all heat exchangers of the shell and tube type. Each is used in some particular way to recover heat from exhaust steam by heating the feedwater which is circulated through the units.

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  6. Auxiliary Feed systems for boilers and steam turbines
    7. Where, for instance, steam-driven deck auxiliaries are in use, a separate auxiliary condenser operating at about atmospheric pressure will condense the incoming steam . An extraction pump will supply the condensate to an air ejector which will return the feedwater to the main system at a point between the gland steam condenser and the drains cooler.....

    More .....

    Boiler feed operation and maintenance
    Extraction pumps should be checked regularly to ensure that the sealing arrangements are preventing air from entering the system. It is usual with most types of glands to permit a slight leakage of water to ensure lubrication of the shaft and the gland.

    More .....

  7. Function of High pressure feed heater
    8. The high-pressure feed heater is a heat exchanger of the shell and tube type which further heats the feedwater before entry to the boiler. Further heat may be added to the feedwater without its becoming steam since its pressure has now been raised by the feed pump.....

    More .....

  8. Sea water circulation of coolers for lubricating oil, piston cooling, jacket water, charge air, turbo-charger
    9. The usual arrangement for motorships has been to have sea-water circulation of coolers for lubricating oil, piston cooling, jacket water, charge air, turbo-charger oil , fuel valve cooling, plus direct sea-water cooling for air compressors and evaporators.....

  9. Feed extraction pump - working procedure
    10. The extraction pump is used to draw water from a condenser which is under vacuum.The pump also provides the pressure to deliver the feed water to the de-aerator or feed pump inlet.

  10. How an air ejector works in a boiler feed system
    11. The air ejector draws out the air and vapours which are released from the condensing steam in the condenser. If the air were not removed from the system it could cause corrosion problems in the boiler. Also, air present in the condenser would affect the condensing process and cause a back pressure in the condenser.....

  11. Function of condenser in a feed system for boiler and steam turbine
    12. The condenser is a heat exchanger which removes the latent heat from exhaust steam so that it condenses and can be pumped back into the boiler. The feed system completes the cycle between boiler and turbine to enable the exhausted steam to return to the boiler as feedwater.



Marine machineries - Useful tags

Marine diesel engines ||Steam generating plant ||Air conditioning system ||Compressed air ||Marine batteries ||Cargo refrigeration ||Centrifugal pump ||Various coolers ||Emergency power supply ||Exhaust gas heat exchangers ||Feed system ||Feed extraction pump || Flow measurement || Four stroke engines || Fuel injector || Fuel oil system || Fuel oil treatment ||Gearboxes || Governor || Marine incinerator || Lub oil filters || MAN B&W engine || Marine condensers || Oily water separator || Overspeed protection devices || Piston & piston rings || Crankshaft deflection || Marine pumps || Various refrigerants || Sewage treatment plant || Propellers || Power Plants || Starting air system || Steam turbines || Steering gear || Sulzer engine || Turbine gearing || Turbochargers || Two stroke engines || UMS operations || Drydocking & major repairs || Critical machinery || Deck machineries & cargo gears || Control and instrumentation ||Fire protection ||Engine room safety ||





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