Marine Engineering I. Attendance Attendance Course Outline Course Outline 2 Hour Examinations – 40 % (20 % each) 2 Hour Examinations – 40 % (20 % each)

Marine Engineering IMarine Engineering I


• AttendanceAttendance

• Course OutlineCourse Outline

• 2 Hour Examinations – 40 % (20 % 2 Hour Examinations – 40 % (20 % each)each)

• Laboratories – 15 % **Laboratories – 15 % ** ** All labs are mandatory and include ** All labs are mandatory and include

STCW content. Missed labs will not be STCW content. Missed labs will not be made up during the term and will result made up during the term and will result in a “F” for the course.in a “F” for the course.


• Homework – 10 %Homework – 10 %

• Class Participation & Quizzes – 5 % Class Participation & Quizzes – 5 %

• Final Exam – 30 % *Final Exam – 30 % * * In order to pass the course with a * In order to pass the course with a

grade of “D” or better, Midshipman must grade of “D” or better, Midshipman must have an examination average of 60 % or have an examination average of 60 % or better.better.


• What happens inside a Steam What happens inside a Steam Generator?Generator?

• A fuel (Oil, Coal, Natural Gas, Wood A fuel (Oil, Coal, Natural Gas, Wood and other fuels) (Chemical Energy).and other fuels) (Chemical Energy).

• Mixes with the OMixes with the O22 in air and undergoes in air and undergoes combustion.combustion.

• From combustion heat is generated From combustion heat is generated (Thermal Energy).(Thermal Energy).


• The heat is transferred to the water The heat is transferred to the water and steam in the boiler which raises and steam in the boiler which raises it temperature and changes its it temperature and changes its phase.phase.


Heat Transfer is accomplished in three Heat Transfer is accomplished in three different modes.different modes.

• Conduction – which is heat transfer thru a Conduction – which is heat transfer thru a solid.solid.

• Convection – which is heat transfer thru a Convection – which is heat transfer thru a fluid (liquid and/or vapor).fluid (liquid and/or vapor). Natural convection – Convection due to a density Natural convection – Convection due to a density

difference.difference. Forced convection – Convection by the use of a Forced convection – Convection by the use of a

mechanical means (fan, blower, etc.)mechanical means (fan, blower, etc.)


• Radiation – Heat transfer thru Radiation – Heat transfer thru electromagnetic wave lengthselectromagnetic wave lengths

• Conduction (Q) = KA(Conduction (Q) = KA(ΔΔt/t/ΔΔx)x)

• Convection (Q) = hA(tConvection (Q) = hA(t11 – t – t22))

• Radiation (Q) = Radiation (Q) = εσεσA(TA(T1144 – T – T22

44))

• All three modes of heat transfer have All three modes of heat transfer have what in common?what in common?

Heat Energy RequiredHeat Energy Required

• Superheater outlet conditionsSuperheater outlet conditions•600 PSIA 600 PSIA

•800 800 °F°F

•h = 1407.9 BTU/lbmh = 1407.9 BTU/lbm


• Feedwater entering BoilerFeedwater entering Boiler•700 psia700 psia

•300 300 °F°F

•h = 269.7 BTU/lbmh = 269.7 BTU/lbm


• Energy required to raise temperature Energy required to raise temperature of boiler water to where boiling take of boiler water to where boiling take place?place?


• Since boiler pressure is 600 psia, the Since boiler pressure is 600 psia, the corresponding saturation corresponding saturation temperature is 486.25 temperature is 486.25 °F°F

• h h 600 psia600 psia = 471.7 BTU/lbm = 471.7 BTU/lbm• Energy Required to heat water to its Energy Required to heat water to its

boiling point is h boiling point is h 600 600 – h – h 300 300 • 471.7 BTU/lbm – 269.7 BTU/lbm471.7 BTU/lbm – 269.7 BTU/lbm• 202.0 BTU/lbm202.0 BTU/lbm


• Energy required to change water at Energy required to change water at 600 psia to 100% steam at 600 psia.600 psia to 100% steam at 600 psia.

• hhf f = 471.7 BTU/lbm= 471.7 BTU/lbm

• hhgg = 1203.7 BTU/lbm = 1203.7 BTU/lbm

• hhfg fg = 732.0 BTU/lbm= 732.0 BTU/lbm

• Energy required to change phase is Energy required to change phase is 732.0 BTU/lbm732.0 BTU/lbm


• Energy needed to superheat steam Energy needed to superheat steam from saturated conditions to boiler from saturated conditions to boiler outlet conditions.outlet conditions.

•hhg g = 1203.7 BTU/lbm= 1203.7 BTU/lbm

•Superheater outlet conditions are 600 psia Superheater outlet conditions are 600 psia and 800 and 800 °F, h°F, hSH SH = 1408.3 BTU/lbm= 1408.3 BTU/lbm

•Energy required to superheat steam is hEnergy required to superheat steam is hSH SH – – hhg g

•1408.3 – 1203.7 = 204.6 BTU/lbm1408.3 – 1203.7 = 204.6 BTU/lbm


• Total energy required is:Total energy required is:•202.0 BTU/lbm (Sensible Heat Energy)202.0 BTU/lbm (Sensible Heat Energy)

•732.0 BTU/lbm (Latent Heat Energy)732.0 BTU/lbm (Latent Heat Energy)

•204.6 BTU/lbm (Sensible Heat Energy)204.6 BTU/lbm (Sensible Heat Energy)

•Total Energy Required is 1138.6 BTU/lbmTotal Energy Required is 1138.6 BTU/lbm

QIn

QOut

Work

MarineMarine BoilersBoilers

• Fire Tube Boilers (Scotch Boiler)Fire Tube Boilers (Scotch Boiler)

• Water Tube BoilersWater Tube Boilers

Firetube BoilersFiretube Boilers

• The fire or hot gases from the burner The fire or hot gases from the burner is channeled through tubes that are is channeled through tubes that are surrounded by the fluid to be heated.surrounded by the fluid to be heated.

• The body of the boiler is the pressure The body of the boiler is the pressure vessel that contains the fluid.vessel that contains the fluid.

• In most cases the fluid is water that In most cases the fluid is water that will be circulated for heating will be circulated for heating purposes or converting to steam.purposes or converting to steam.


• Every set of tubes that the flue gas Every set of tubes that the flue gas travels through, before it makes a travels through, before it makes a turn is considered a “pass”.turn is considered a “pass”.

• A three pass boiler will have three A three pass boiler will have three sets of tubes with the stack outlet sets of tubes with the stack outlet located on the rear of the boiler.located on the rear of the boiler.

• A four pass boiler will have four sets A four pass boiler will have four sets and the stack outlet at the front of and the stack outlet at the front of the boiler.the boiler.


Source: www.steamesteam.com

Furnace

Stay Rods

Furnace

Firetubes

Firetubes

Combustions Chamber

Stays


Source: www.steamesteam.com

Steam Out Exhaust Out

Scotch BoilerScotch Boiler

Consists of a horizontal cylindrical shell Consists of a horizontal cylindrical shell closed a each end. Inside the shell were closed a each end. Inside the shell were mounted the following:mounted the following:

• Mounted corrugated metal furnacesMounted corrugated metal furnaces• Combustion chamber(s)Combustion chamber(s)• Fire tubesFire tubes• Structural support members called Structural support members called

staysstays

Fire Tube Boiler SizeFire Tube Boiler Size

• The amount of heating surface The amount of heating surface needed to provide the required rate needed to provide the required rate of evaporation and steam pressureof evaporation and steam pressure

• The type of fuel being used (Coal, Oil, The type of fuel being used (Coal, Oil, Gas)Gas)

• Method of firingMethod of firing

FurnacesFurnaces

• Space provided within or as a part of boiler Space provided within or as a part of boiler construction for the burning of fuelconstruction for the burning of fuel

The furnaces were constructed of a The furnaces were constructed of a corrugated design for the following corrugated design for the following advantagesadvantages

1. Greater Strength1. Greater Strength2. Increase surface area for heat 2. Increase surface area for heat transfertransfer3. Allow for expansion and contraction3. Allow for expansion and contraction

Combustion ChambersCombustion Chambers

• Is an enclosed space constructed of Is an enclosed space constructed of steel, provided for the completion of steel, provided for the completion of combustion which was started in the combustion which was started in the furnace.furnace.

• The combustion chamber was located The combustion chamber was located in the rear of the scotch boiler shell in the rear of the scotch boiler shell and also acts to redirect gases of and also acts to redirect gases of combustion and also serves as part of combustion and also serves as part of the heating surface of the boiler.the heating surface of the boiler.

Combustion ChambersCombustion Chambers

• Types of combustion chambersTypes of combustion chambers

1. Dry back combustion chamber 1. Dry back combustion chamber with single or multiple furnaces.with single or multiple furnaces.

2. Wet back combustion chamber 2. Wet back combustion chamber with single or multiple furnaces.with single or multiple furnaces.

UptakesUptakes

• Uptakes are generally constructed of Uptakes are generally constructed of steel and are used to serve as a retainer steel and are used to serve as a retainer for the exhaust gases of combustion for the exhaust gases of combustion flowing from the front head to the boiler flowing from the front head to the boiler stackstack

• Uptakes are provided with inspection Uptakes are provided with inspection doors and are insulated to prevent doors and are insulated to prevent personnel injury and excessive heat personnel injury and excessive heat from radiating into the fire roomfrom radiating into the fire room

Fire TubesFire Tubes

• Fire tubes are small cylindrical shells Fire tubes are small cylindrical shells or pipes that make up the greatest or pipes that make up the greatest surface area for heat transfersurface area for heat transfer

• The rear ends of the fire tubes are The rear ends of the fire tubes are connected to the front face of the connected to the front face of the combustion chamber (know as the combustion chamber (know as the tube sheet) The front ends of the tube sheet) The front ends of the tubes are connected to the front tubes are connected to the front head of the boiler shell.head of the boiler shell.

Stay TubesStay Tubes

• In a fire tube boiler the products of In a fire tube boiler the products of combustion pass through the fire combustion pass through the fire tubes which are surrounded by watertubes which are surrounded by water

• Stay tubes are thicker tubes and are Stay tubes are thicker tubes and are used not only as a heating surface, used not only as a heating surface, but also structurally support the tube but also structurally support the tube sheet of the combustion chamber(s) sheet of the combustion chamber(s) to the front head of the boiler.to the front head of the boiler.

Mountings and FittingsMountings and Fittings

• Internal feed line – This line is a Internal feed line – This line is a continuation of the feed pipe within the continuation of the feed pipe within the boiler and is used to distribute the feed boiler and is used to distribute the feed water evenly along the length of the water evenly along the length of the shellshell

• Scum pan – Is located at the normal Scum pan – Is located at the normal water level of the boiler and is used to water level of the boiler and is used to collect floating impurities on the water collect floating impurities on the water surface and lead them to the surface surface and lead them to the surface blow connectionblow connection

Mountings and FittingsMountings and Fittings

• Dry pipe – This pipe is located near the Dry pipe – This pipe is located near the top of the shell and runs almost the full top of the shell and runs almost the full length of the shell, It is used to collect length of the shell, It is used to collect steam for removal from the boiler and steam for removal from the boiler and to minimize moisture carryoverto minimize moisture carryover

• Fusible plug – The fusible plug is a Fusible plug – The fusible plug is a device installed in the center of the device installed in the center of the crown sheet of the combustion crown sheet of the combustion chamber to warn the operator in the chamber to warn the operator in the event of low water levelevent of low water level

Advantages of Scotch Advantages of Scotch BoilerBoiler

• Low costLow cost• Easy accessibility for maintenanceEasy accessibility for maintenance• Less radiation losses (fires and gases of Less radiation losses (fires and gases of

combustion are surrounded by water)combustion are surrounded by water)• Capability of using relatively impure Capability of using relatively impure

water without causing serious damagewater without causing serious damage• Less skilled operators required because Less skilled operators required because

of the large quantity of water presentof the large quantity of water present• Steadier steam pressuresSteadier steam pressures

Disadvantages of Scotch Disadvantages of Scotch BoilersBoilers

• Susceptibility to explosions that would Susceptibility to explosions that would result in hot water dumping into the result in hot water dumping into the fire room, flashing into steam, and fire room, flashing into steam, and injuring engineroom personnel.injuring engineroom personnel.

• Thick boiler plating requirements for Thick boiler plating requirements for high pressures making the boiler high pressures making the boiler weight prohibitive for most high weight prohibitive for most high pressure applicationspressure applications

• Relative long warm up period Relative long warm up period (minimum time 12 to 24 hours)(minimum time 12 to 24 hours)


• Weakened structural integrity of the ship Weakened structural integrity of the ship (Scotch boilers are usually delivered (Scotch boilers are usually delivered completely assembled which requires completely assembled which requires large openings in the fire room for large openings in the fire room for installation and when filled with water installation and when filled with water offer large concentrations of weight to offer large concentrations of weight to some structural members of the shipsome structural members of the ship

• Incapability of rapid changes in steaming Incapability of rapid changes in steaming rates for maneuvering purposesrates for maneuvering purposes


• Sluggishness for long maneuvering Sluggishness for long maneuvering periods requiring frequent changes in periods requiring frequent changes in steam demand (caused by large steam demand (caused by large volume of water in the boiler)volume of water in the boiler)

• Incapability of rapid changes in Incapability of rapid changes in steaming rates for maneuvering steaming rates for maneuvering purposespurposes


Source: Cleaver-Brooks

Cleaver – Brooks BoilerCleaver – Brooks Boiler

• Dryback StyleDryback Style

• 15 – 80 Horsepower15 – 80 Horsepower

• Heating or processingHeating or processing

• Steam (15-250 psi) or Hot Water (30 psi)Steam (15-250 psi) or Hot Water (30 psi)

• Oil, Natural Gas or combinationOil, Natural Gas or combination

• Alternate fuel capabilityAlternate fuel capability

• Low NOx capabilityLow NOx capability


Source: www.energyinc.com


Source: www.energyinc.com


Source: Babcock & Wanson


Source: Babcock & Wanson

Firetube Boilers Firetube Boilers AdvantagesAdvantages

• Relatively inexpensiveRelatively inexpensive

• Easy to cleanEasy to clean

• Compact in sizeCompact in size

• Available in sizes from 600,000 BTU/hr to Available in sizes from 600,000 BTU/hr to 50,000,000 BTU/hr.50,000,000 BTU/hr.

• Easy to replace tubesEasy to replace tubes

• Well suited for space heating and Well suited for space heating and industrial process applicationsindustrial process applications

• Very easy to automateVery easy to automate

Firetube boiler Firetube boiler DisadvantagesDisadvantages

• Not suitable for high pressure Not suitable for high pressure applications of 250 psig and above.applications of 250 psig and above.

• Limitation of high capacity steam Limitation of high capacity steam generation.generation.


Documents

Marine Engineering I. Attendance Attendance Course Outline Course Outline 2 Hour Examinations – 40 % (20 % each) 2 Hour Examinations – 40 % (20 % each)