An Introduction

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• An Introduction
• To
• Marine Steam Propulsion Plant
• Source US Navy

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Four Phases of Steam Cycle

• Generation
• Expansion
• Condensation
• Feed

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GENERATION (Boilers)
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GENERATION

• Boiler
• fuel is converted to heat
• largest and heaviest part of steam plant
• heat is transferred via conduction to water in
  the metal tubes
• some of this water becomes steam
• Steam drum
• as steam is generated it collects in the upper
  portion of the boiler
• steam collecting in the steam drum is called
  saturated steam

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GENERATION

• Super heater
• saturated steam does not contain enough thermal
  energy to make the turbines operate efficiently
• uses heat from the burner section of the boiler
  to increase the temperature of the steam
• superheated steam is also dryer which helps
  prevent erosion of the turbine blades and main
  feed pumps

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GENERATION

• Economizer
• improves efficiency in the steam plant
• uses thermal energy that would go up the stack to
  preheat feedwater before the steam drum
• nest of tubes located between the generating
  tubes of the boiler and the stack

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EXPANSION (Turbines)
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EXPANSION

• Turbines
• High pressure/high temperature steam goes from
  the superheater outlet to the high pressure
  turbine of the main engine
• this is where expansion begins
• superheated steam expands in the turbine and is
  converted to mechanical energy to turn the rotor

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EXPANSION

• energy conversion takes place in two steps in
  each stage of turbine blades
• first the steam passes through the nozzles which
  increase the steams velocity
• this kinetic energy is then converted into work
  by the turbine blades
• after steam leaves the HP turbine it still has
  thermal energy
• steam undergoes the same process in the LP turbine

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CONDENSATION (Condenser, MCP, AEC)
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CONDENSATION

• Main Condenser
• large sealed container that serves as an
  indirect-type shell and tube heat exchanger
• cool seawater flows through thousands of internal
  tubes
• steam from the exhaust of the LP turbine flows
  over these tubes and heat is removed from the
  steam, condensing the steam in to a liquid
  (Condensate)
• The condensing action of the steam creates and
  maintains a vacuum in the condensers

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CONDENSATION

• Main condensate pump
• one or two stage centrifugal pump, electrically
  driven
• moves condensate from the hotwell through the
  main air ejector condenser to the deaerating feed
  tank
• pump is drawing a suction on the water in the
  hotwell
• lowest pressure in the system occurs here

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CONDENSATION

• Air ejector condenser
• shell and tube heat exchanger
• two functions
• removes latent heat from the auxiliary steam
  being discharged by the air ejector
• transfers heat from the steam to the condensate
  to preheat it before it enters the deaerating
  feed tank

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FEED (DFT, MFBP, MFP)
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FEED PHASE

• The Deaerating feed tank is the beginning of the
  feed phase
• Direct type heat exchanger - three functions
• feed is heated by auxiliary steam and then falls
  to the lower section - causing the oxygen held in
  solution to be removed
• heats feed and maintains proper temperature of
  water
• storage tank for heated oxygen free feedwater

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FEED PHASE

• Feedwater goes from deaerating tank to main feed
  boost pump(MFBP)
• MFBP
• one or two stage double suction centrifugal pump
• installed below the DFT
• discharges into the suction side of the main feed
  pump (MFP)

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FEED PHASE

• MFP
• Large Multistage Centrifugal pumps (steam or
  electrically driven)
• delivers feedwater in sufficient amounts and
  develops enough pressure to force the water into
  the boiler against the pressure of the steam drum

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MACHINERY PLANT LAYOUT

• No two ships are exactly alike
• Machinery is arranged in various ways as space
  and weight permit
• Generally speaking
• Propulsion machinery is usually on two levels
• condensers and main reduction gear on lower level
• propulsion turbines and pinion gears are on upper
  level

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MACHINERY PLANT LAYOUT

• Low pressure turbine exhaust is directly above
  the condenser
• Boilers are on the lower and upper levels along
  the centerline of the ship
• END