1. Marine Engineering I

2. Marine Engineering I Attendance Course Outline
2 Hour Examinations – 40 % (20 % each)
Laboratories – 15 % **
** All labs are mandatory and include STCW content. Missed labs will not be made up during the term and will result in a “F” for the course.

3. Marine Engineering I Homework – 10 %
Class Participation & Quizzes – 5 %
Final Exam – 30 % *
* In order to pass the course with a grade of “D” or better, Midshipman must have an examination average of 60 % or better.

4. Marine Engineering I What happens inside a Steam Generator?
A fuel (Oil, Coal, Natural Gas, Wood and other fuels) (Chemical Energy).
Mixes with the O2 in air and undergoes combustion.
From combustion heat is generated (Thermal Energy).

5. Marine Engineering I
The heat is transferred to the water and steam in the boiler which raises it temperature and changes its phase.

6. Marine Engineering I
Heat Transfer is accomplished in three different modes.
Conduction – which is heat transfer thru a solid.
Convection – which is heat transfer thru a fluid (liquid and/or vapor).
Natural convection – Convection due to a density difference.
Forced convection – Convection by the use of a mechanical means (fan, blower, etc.)

7. Marine Engineering I
Radiation – Heat transfer thru electromagnetic wave lengths
Conduction (Q) = KA(Δt/Δx)
Convection (Q) = hA(t1 – t2)
Radiation (Q) = εσA(T14 – T24)
All three modes of heat transfer have what in common?

11. Heat Energy Required Superheater outlet conditions 600 PSIA 800 °F
h = BTU/lbm

12. Heat Energy Required Feedwater entering Boiler 700 psia 300 °F
h = BTU/lbm

13. Heat Energy Required
Energy required to raise temperature of boiler water to where boiling take place?

14. Heat Energy Required
Since boiler pressure is 600 psia, the corresponding saturation temperature is °F
h 600 psia = BTU/lbm
Energy Required to heat water to its boiling point is h 600 – h 300
471.7 BTU/lbm – BTU/lbm
202.0 BTU/lbm

15. Heat Energy Required Energy required to change phase is 732.0 BTU/lbm
Energy required to change water at 600 psia to 100% steam at 600 psia.
hf = BTU/lbm
hg = BTU/lbm
hfg = BTU/lbm
Energy required to change phase is BTU/lbm

16. Heat Energy Required
Energy needed to superheat steam from saturated conditions to boiler outlet conditions.
hg = BTU/lbm
Superheater outlet conditions are 600 psia and 800 °F, hSH = BTU/lbm
Energy required to superheat steam is hSH – hg
– = BTU/lbm

17. Heat Energy Required Total energy required is:
202.0 BTU/lbm (Sensible Heat Energy)
732.0 BTU/lbm (Latent Heat Energy)
204.6 BTU/lbm (Sensible Heat Energy)
Total Energy Required is BTU/lbm

18. QIn
Work
QOut

19. Marine Boilers
Fire Tube Boilers (Scotch Boiler)
Water Tube Boilers

20. Firetube Boilers
The fire or hot gases from the burner is channeled through tubes that are surrounded by the fluid to be heated.
The body of the boiler is the pressure vessel that contains the fluid.
In most cases the fluid is water that will be circulated for heating purposes or converting to steam.

21. Firetube Boilers
Every set of tubes that the flue gas travels through, before it makes a turn is considered a “pass”.
A three pass boiler will have three sets of tubes with the stack outlet located on the rear of the boiler.
A four pass boiler will have four sets and the stack outlet at the front of the boiler.

22. Firetube Boilers Firetubes Stay Rods Firetubes Stays Furnace Furnace
Source:
Combustions Chamber

23. Firetube Boilers
Source:

28. Exhaust Out
Steam Out

29. Scotch Boiler
Consists of a horizontal cylindrical shell closed a each end. Inside the shell were mounted the following:
Mounted corrugated metal furnaces
Combustion chamber(s)
Fire tubes
Structural support members called stays

30. Fire Tube Boiler Size
The amount of heating surface needed to provide the required rate of evaporation and steam pressure
The type of fuel being used (Coal, Oil, Gas)
Method of firing

31. Furnaces
Space provided within or as a part of boiler construction for the burning of fuel
The furnaces were constructed of a corrugated design for the following advantages
1. Greater Strength
2. Increase surface area for heat transfer
3. Allow for expansion and contraction

32. Combustion Chambers
Is an enclosed space constructed of steel, provided for the completion of combustion which was started in the furnace.
The combustion chamber was located in the rear of the scotch boiler shell and also acts to redirect gases of combustion and also serves as part of the heating surface of the boiler.

33. Combustion Chambers Types of combustion chambers
1. Dry back combustion chamber with single or multiple furnaces.
2. Wet back combustion chamber with single or multiple furnaces.

34. Uptakes
Uptakes are generally constructed of steel and are used to serve as a retainer for the exhaust gases of combustion flowing from the front head to the boiler stack
Uptakes are provided with inspection doors and are insulated to prevent personnel injury and excessive heat from radiating into the fire room

35. Fire Tubes
Fire tubes are small cylindrical shells or pipes that make up the greatest surface area for heat transfer
The rear ends of the fire tubes are connected to the front face of the combustion chamber (know as the tube sheet) The front ends of the tubes are connected to the front head of the boiler shell.

36. Stay Tubes
In a fire tube boiler the products of combustion pass through the fire tubes which are surrounded by water
Stay tubes are thicker tubes and are used not only as a heating surface, but also structurally support the tube sheet of the combustion chamber(s) to the front head of the boiler.

37. Mountings and Fittings
Internal feed line – This line is a continuation of the feed pipe within the boiler and is used to distribute the feed water evenly along the length of the shell
Scum pan – Is located at the normal water level of the boiler and is used to collect floating impurities on the water surface and lead them to the surface blow connection

38. Mountings and Fittings
Dry pipe – This pipe is located near the top of the shell and runs almost the full length of the shell, It is used to collect steam for removal from the boiler and to minimize moisture carryover
Fusible plug – The fusible plug is a device installed in the center of the crown sheet of the combustion chamber to warn the operator in the event of low water level

39. Advantages of Scotch Boiler
Low cost
Easy accessibility for maintenance
Less radiation losses (fires and gases of combustion are surrounded by water)
Capability of using relatively impure water without causing serious damage
Less skilled operators required because of the large quantity of water present
Steadier steam pressures

40. Disadvantages of Scotch Boilers
Susceptibility to explosions that would result in hot water dumping into the fire room, flashing into steam, and injuring engineroom personnel.
Thick boiler plating requirements for high pressures making the boiler weight prohibitive for most high pressure applications
Relative long warm up period (minimum time 12 to 24 hours)

41. Disadvantages of Scotch Boilers
Weakened structural integrity of the ship (Scotch boilers are usually delivered completely assembled which requires large openings in the fire room for installation and when filled with water offer large concentrations of weight to some structural members of the ship
Incapability of rapid changes in steaming rates for maneuvering purposes

42. Disadvantages of Scotch Boilers
Sluggishness for long maneuvering periods requiring frequent changes in steam demand (caused by large volume of water in the boiler)
Incapability of rapid changes in steaming rates for maneuvering purposes

43. Firetube Boilers
Source: Cleaver-Brooks

44. Cleaver – Brooks Boiler
Dryback Style
15 – 80 Horsepower
Heating or processing
Steam ( psi) or Hot Water (30 psi)
Oil, Natural Gas or combination
Alternate fuel capability
Low NOx capability

45. Firetube Boilers
Source:

46. Firetube Boilers
Source:

47. Firetube Boilers
Source: Babcock & Wanson

48. Firetube Boilers
Source: Babcock & Wanson

49. Firetube Boilers Advantages
Relatively inexpensive
Easy to clean
Compact in size
Available in sizes from 600,000 BTU/hr to 50,000,000 BTU/hr.
Easy to replace tubes
Well suited for space heating and industrial process applications
Very easy to automate

50. Firetube boiler Disadvantages
Not suitable for high pressure applications of 250 psig and above.
Limitation of high capacity steam generation.

51. Firetube Boilers