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MAIN FEED and CONDENSATE

INTRODUCTION TO NAVAL ENGINEERING. MAIN FEED and CONDENSATE. Main Condensate System. P-V DIAGRAM. BOILER. PRESSURE. PUMP. TURBINE. CONDENSER. VOLUME. P-V DIAGRAM. SUBCOOLED LIQUID. PRESSURE. SUPERHEATED STEAM. “WET VAPOR”. VOLUME. T-S DIAGRAM. TEMPERATURE. ENTROPY.

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MAIN FEED and CONDENSATE

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  1. INTRODUCTION TO NAVAL ENGINEERING MAIN FEED and CONDENSATE

  2. Main Condensate System

  3. P-V DIAGRAM BOILER PRESSURE PUMP TURBINE CONDENSER VOLUME

  4. P-V DIAGRAM SUBCOOLED LIQUID PRESSURE SUPERHEATED STEAM “WET VAPOR” VOLUME

  5. T-S DIAGRAM TEMPERATURE ENTROPY

  6. EXPANSION (Turbines)

  7. The Expansion Phase • Transformations of thermal energy to mechanical kinetic energy (at nozzles) to mechanical work (at blades) • General differences between HP and LP turbines • Pressure-temperature relationships throughout turbines

  8. EXPANSION (Turbines) • Goes first to the High Pressure Turbines • Converts thermal energy to mechanical energy • Steam first goes through “nozzles” to increase steam speed then through “blades” which does the actual work • Then goes through Low Pressure Turbine

  9. EXPANSION (Turbines)

  10. Objectives • Components of Main Condensate System and purposes of each • Components of Main Feed System and purposes of each • Operation of Automatic Control Systems • Interrelationship of systems during operations

  11. CONDENSATION (Condenser, MCP, AEC)

  12. THE CONDENSATION PHASE • Condense steam to water for re-use in plant • Why a vacuum? • Pump condensate from main condenser to DFT • Provide cooling for air ejector condenser

  13. SEAWATER COOLING • Main Seawater Circulating System • Main Seawater Circulating Pump • propeller type (high flow rate; low HP) • used when • going astern or stopped • slow ahead (< 5 knots) • also to de-water engineroom in case of flooding • Scoop Injection System • used when moving ahead at speeds over 5 kts

  14. CONDENSATE DEPRESSION • The difference between temperature of the condensate and the temperature at which steam condenses at a given vacuum (i.e. sub cooling) • Maintained at 2-5 degrees • Above 2: Necessary to prevent cavitation and vapor lock of the MCP • Below 5: Above which efficiency is lost since condensate must be reheated. Also, above 5F, the absorption of air by the condensate is increased which increases the corrosion of piping

  15. Main Feed System • Purpose: to deaerate, preheat, store, and transport water from DFT to the boiler or S/G

  16. THE FEED PHASE • Overall purposes for the feed phase • preheat • store • deaerate • increase pressure to deliver feedwater to the steam drum • Pressure-temperature relationships across each component

  17. PURPOSE OF DFT • Preheats feedwater • Deaerates feedwater • Stores

  18. FEED (DFT, MFBP, MFP) • Deaerating Feed Tank: • Removes Oxygen • Preheats • Stores Water • MFBP takes suction on DFT and discharges it at 80-100#’s (Prevents hot feedwater at 250F from flashing to steam in the MFP)

  19. PURPOSE OF MFBP • Prevent vapor lock of MFP • Ensure there is always sufficient NPSH for the MFP • (Typically a single-stage, double-suction, centrifugal pump)

  20. MAIN FEED PUMP • Provides water to the boilers at a sufficient rate and pressure to ensure boiler level is maintained • Typically: Multistage, high speed, centrifugal pump. May be either steam or electric driven • Discharge pressure up to 1300 psig

  21. FEEDWATER CONTROL VALVE Regulates the amount of water sent to the boilers

  22. AUTOMATIC BOILER CONTROL SYSTEM Three Parts

  23. Automatic Combustion Control (ACC) System

  24. AUTOMATIC COMBUSTION CONTROL (ACC) • Purpose: To maintain the boiler steam-drum pressure at a constant 1275 psig during steady and changing steam conditions. • Measures • Compares • Computes • Corrects

  25. FEEDWATER CONTROLS (FWC) • Purpose: To regulate the supply of feedwater sent to the boiler for use in steam production • Measures • Compares • Computers • Corrects

  26. MFP DIFFERENTIAL PRESSURE CONTROLS • Purpose: Ensures that the feedwater-supply pressure is maintained at a constant value above the steam-drum pressure (75 psi) • Measures • Compares • Computes • Corrects

  27. Interrelation of Systems • Answering AA2/3 -> OOD orders AAII • Open throttles -> steam flow -> steam pressure • ACC system air & fuel to combustion rate • FWC system feed to match steam flow • DCS of MFP speed of MFP to discharge pressure

  28. BOILER WATER CHEMISTRY

  29. BOILER WATER CHEMISTRY • pH AND PHOSPHATES • PREVENTION OF SCALE BUILDUP • PURPOSE OF BLOWDOWNS • LOWER PH / PHOSPHATE LEVEL • REMOVE SLUDGE OR SUSPENDED SOLIDS • REMOVE CHLORIDE IONS (FROM SEAWATER ACCIDENT) • INSPECTION / CLEANING REQUIREMENTS

  30. Factors Involved in Machinery Plant Layout and Design • Midships location of engine rooms and machinery rooms

  31. Factors Involved in Machinery Plant Layout and Design • Functional relationships between components

  32. Factors Involved in Machinery Plant Layout and Design • Use of multiple levels or decks

  33. Factors Involved in Machinery Plant Layout and Design • Component relationship to centerline (stability)

  34. Factors Involved in Machinery Plant Layout and Design • Ease of maintenance • Damage control (prevent spread of fires and flooding)

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