Boiler Classification and Principles
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Questions and Answers

What is the primary method of water circulation in a natural circulation boiler?

  • Forced by pumps
  • Due to temperature difference (correct)
  • Through vacuum formation
  • By mechanical agitation

    • Which of the following statements is true about fire tube boilers?

  • They are primarily designed for rapid steam generation.
  • They can operate at pressures above 20 bar.
  • They use hot flue gases to heat water surrounding the tubes. (correct)
  • They circulate water inside tubes.

    • What distinguishes water tube boilers from fire tube boilers?

  • Gases pass through the tubes while water circulates outside.
  • Water circulates inside the tubes with gases passing around them. (correct)
  • They are less efficient than fire tube boilers.
  • Water is circulated externally to the tubes.

    • Which boiler type is more suitable for generating steam at very high pressures?

    <p>Water tube boiler</p> Signup and view all the answers

    Which boiler examples are categorized as fire tube boilers?

    <p>Cochran, Cornish, and Locomotive</p> Signup and view all the answers

    What is a characteristic feature of the Babcock and Wilcox boiler?

    <p>It is an externally fired boiler.</p> Signup and view all the answers

    What is the function of the chain grate stocker in a steam boiler?

    <p>To adjust coal feeding speed for effective burning.</p> Signup and view all the answers

    How is water introduced into the boiler drum?

    <p>Via the feed valve, maintaining a constant water level.</p> Signup and view all the answers

    What is the maximum steam pressure that a high capacity Babcock and Wilcox boiler can produce?

    <p>80 bar</p> Signup and view all the answers

    What initiates the circulation of water within the boiler?

    <p>The reduction in water density due to heating.</p> Signup and view all the answers

    Which of the following boilers is suited for quick steam raising?

    <p>Babcock and Wilcox boiler</p> Signup and view all the answers

    What is the flow path of the flue gases in a steam boiler?

    <p>Upwards and downwards around the water tubes and out through the exit door.</p> Signup and view all the answers

    What happens to the steam-water mixture from the water tubes in the boiler?

    <p>It ascends through the uptake header to the boiler drum.</p> Signup and view all the answers

    What role do the baffle plates serve in the path of flue gases?

    <p>They direct the flow of hot gases around the water tubes.</p> Signup and view all the answers

    What is the primary function of the steam stop valve?

    <p>To regulate the flow of steam from the boiler</p> Signup and view all the answers

    Where is the upper junction box of the super heater tubes connected?

    <p>To the T-tube situated in the steam space of the drum.</p> Signup and view all the answers

    What primarily governs the time for coal to burn in the chain grate stocker?

    <p>The speed at which the grate moves.</p> Signup and view all the answers

    How does the blow off valve contribute to boiler maintenance?

    <p>It removes sediments from the boiler</p> Signup and view all the answers

    What unique feature does the feed check valve possess?

    <p>It operates as both a feed valve and a check valve</p> Signup and view all the answers

    What triggers the operation of the fusible plug?

    <p>A drop in water level in the boiler</p> Signup and view all the answers

    What is the purpose of the manhole in the boiler?

    <p>To allow access for cleaning and inspection</p> Signup and view all the answers

    Where is the mud box located in relation to the boiler system?

    <p>At the bottom of the down take header</p> Signup and view all the answers

    What is one of the primary functions of boiler accessories?

    <p>To enhance the boiler's overall efficiency</p> Signup and view all the answers

    Which component is specifically designed to prevent water from flowing back into the feed pump?

    <p>Feed check valve</p> Signup and view all the answers

    What is the primary purpose of the super heater in a water tube boiler?

    <p>To ensure the steam is superheated for efficient operation</p> Signup and view all the answers

    How do water tube boilers compare to fire tube boilers in terms of steam generation speed?

    <p>Water tube boilers can raise steam more quickly due to a lower water content ratio</p> Signup and view all the answers

    What advantage do water tube boilers have over fire tube boilers regarding pressure?

    <p>They can operate at higher pressures for the same wall thickness</p> Signup and view all the answers

    What is a major advantage of water tube boilers concerning evaporation rates?

    <p>Their design leads to greater evaporation rates due to a larger heating surface</p> Signup and view all the answers

    What is the primary cause of lower sediment deposition in water tube boilers?

    <p>Water circulation is more efficient in water tube boilers</p> Signup and view all the answers

    Which component is essential for controlling superheated steam flow in a boiler system?

    <p>Steam stop valve</p> Signup and view all the answers

    What is one common disadvantage of fire tube boilers compared to water tube boilers?

    <p>They are less likely to develop high pressures</p> Signup and view all the answers

    In a water tube boiler, what typically happens to steam when it is not required?

    <p>It directly passes out to the prime mover through the steam stop valve</p> Signup and view all the answers

    What is the primary function of an economizer in a boiler system?

    <p>To preheat feed water using flue gas heat</p> Signup and view all the answers

    Which accessory is specifically used to enhance combustion efficiency by preheating air?

    <p>Air Preheater</p> Signup and view all the answers

    Why is superheated steam necessary in thermal power generation?

    <p>To prevent condensation and corrosion in turbines</p> Signup and view all the answers

    What role does a steam separator play in a boiler system?

    <p>To separate entrained water particles from steam</p> Signup and view all the answers

    Where is an air preheater typically located in relation to other boiler components?

    <p>Between the economizer and the chimney</p> Signup and view all the answers

    What is the effect of using an economizer on fuel consumption in a boiler?

    <p>It reduces fuel consumption by improving efficiency</p> Signup and view all the answers

    Which accessory is essential for maintaining dry steam conditions in steam turbines?

    <p>Superheater</p> Signup and view all the answers

    What is a disadvantage of using wet steam in a steam turbine?

    <p>It can cause turbine corrosion and damage</p> Signup and view all the answers

    Study Notes

    Boiler Classification

    • Boilers are categorized based on circulation methods: Natural Circulation (due to temperature difference) and Forced Circulation (using pumps).
    • Another classification is based on the arrangement of water and flue gases: Fire Tube Boilers and Water Tube Boilers.

    Fire Tube Boilers

    • Hot flue gases circulate through tubes while water surrounds these tubes.
    • Common types include:
      • Cochran boiler
      • Cornish boiler
      • Lancashire boiler
      • Locomotive boiler
      • Scotch Marine boiler
    • Suitable for steady working pressures up to 20 bar.

    Water Tube Boilers

    • Water circulates inside tubes, with hot gases passing around externally.
    • Examples include:
      • Babcock and Wilcox boiler
      • Stirling boiler
      • Yarrow boiler
    • Better suited for high pressure steam generation and rapid steam production.

    Babcock & Wilcox Boiler

    • Type of horizontal, externally fired, natural circulation water tube boiler.
    • Capable of producing steam at up to 80 bar.
    • Features a superheater with U-tubes located in the combustion chamber.

    Water Circuit

    • Water enters the boiler drum via a feed valve, maintaining a constant level.
    • Heated water descends into headers, ascending in inclined tubes due to decreased density.
    • Continuous circulation established between the boiler drum and the water tubes.

    Flue Gas Path

    • Hot gases pass upwards and downwards around water tubes before exiting through the chimney.
    • Direct contact with hot gases leads to efficient heating and evaporation of water in the tubes.

    Superheating of Steam

    • Steam from the boiler drum is directed to a superheater for increased temperature.
    • Superheated steam is essential for thermal power generation to avoid turbine corrosion.

    Advantages of Water Tube Boilers

    • Quicker steam production: Lower water content allows for rapid steam generation.
    • Higher pressure capacity: Ability to withstand extreme pressures due to no tubes inside the boiler drum.
    • Increased evaporation rate: More heating surface area leads to higher evaporation rates, making it suitable for large power plants.
    • Less sediment deposition: Improved circulation minimizes the likelihood of sediment buildup.

    Boiler Components

    • Steam Stop Valve: Regulates steam flow; opened/closed by rotating a handle.
    • Blow Off Valve: Removes sediment from the boiler; essential for maintenance.
    • Feed Check Valve: Non-return valve regulating water flow; prevents backflow to the drum.
    • Fusible Plug: Safety device that extinguishes fire when water level drops too low.
    • Man Hole & Mud Box: Enhances access for maintenance and sediment removal, respectively.

    Boiler Accessories

    • Accessories serve to improve boiler efficiency and performance, installed outside the boiler drum.
    • Key accessories include:
      • Economizer: Preheats feed water using leftover heat from flue gases, reducing fuel consumption.
      • Air Preheater: Preheats air supplied to the furnace for improved combustion efficiency.
      • Superheater: Increases steam temperature beyond saturation, preventing condensation in turbines.
      • Steam Separator: Removes water particles from steam before it enters the turbine, enhancing efficiency.

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    Description

    Explore the various classifications of boilers, including natural and forced circulation types, as well as the differences between fire tube and water tube boilers. This quiz will test your understanding of how these systems operate based on the principles of working and the flow of water and flue gases.

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