Arctic Bulk Carrier - Aalto

Kul-24.4110: Ship Project A Markus Mälkki, 84343C Assignment 4 Jesse Lehtonen, 84692L

Kul-24.4110: Ship project A

Arctic Bulk Carrier

Assignment 4:

Light Weight & Intact Stability

21.10.2014

Markus Mälkki, 84343C

Jesse Lehtonen, 84692L


CONTENTS

1 Light Weight............................................................................................................................................... 1

1.1 Steel Weight ....................................................................................................................................... 1

1.1.1 Hand Calculation ......................................................................................................................... 1

1.1.2 Empirical Equations .................................................................................................................... 1

1.2 Outfitting Weight ............................................................................................................................... 1

1.2.1 Hatchway covers ......................................................................................................................... 1

1.2.2 Living quarters ............................................................................................................................ 2

1.2.3 Machinery space outfitting ......................................................................................................... 2

1.2.4 Miscellaneous ............................................................................................................................. 2

1.2.5 Main equipment ......................................................................................................................... 3

1.2.6 Outfitting total weight ................................................................................................................ 3

1.2.7 Comparison of results ................................................................................................................. 4

2 Center of Gravity ........................................................................................................................................ 4

3 Intact Stability ............................................................................................................................................ 5

3.1 Initial GM Estimate ............................................................................................................................. 5

3.2 Loading conditions ............................................................................................................................. 6

3.3 Stability criteria .................................................................................................................................. 6

References ......................................................................................................................................................... 8

Appendix A: Area Weights ................................................................................................................................. 9

Appendix B: CoGs and Total Weights ............................................................................................................... 10

Appendix C-1: Loading condition cargo 1 ......................................................................................................... 11

Appendix C-2: Loading condition cargo 2 ......................................................................................................... 14

Appendix C-3: Loading condition ballast 1 ........................................................................................................ 17

Appendix C-4: Loading condition ballast 2 ........................................................................................................ 20


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1 LIGHT WEIGHT

1.1 STEEL WEIGHT

1.1.1 Hand Calculation

The steel weight of the vessel is approximated first by hand calculations. Area masses are first calculated for

each major steel component based on the plate thicknesses and stiffener sizes and spacing. The steel density

used is 8000 kg/m3. The resulting area masses can be seen in Appendix A. Total weights of the members are

then acquired by measuring the area from the general arrangement in AutoCAD and multiplying it with the

calculated mass per square meter. The spreadsheet including the areas and total masses can be seen in

Appendix B.

1.1.2 Empirical Equations

Steel weight of the ship is estimated using simple method by Det Norske Veritas (1972) Total steel weight of

cargo ships can be estimated with the following formula:

where W = 8.51m3 is the section modulus of the midship area. This gives a steel weight estimation of 3508 ton.

However, this estimation doesn’t take into account ice strengthening of the ship. According to Schneekluth, a 180%

increase in the hull steel weight can be expected for Canadian ice class Arc 4. This is the best approximation for the

weight increase caused by ice strengthening. This results in a corrected steel weight of 6318 t. This is obviously very

rough estimation as there is not any detailed information about the effects of ice strengthening to the steel weight.

To obtain more accurate value, a direct calculation is made based on the known steel scantling values of the ship.

1.2 OUTFITTING WEIGHT Outfitting weight includes all weight components that are not taken into account in steel weight. For weight

calculation purposes, outfitting equipment and components are classified in different groups according to their

purpose and position in the ship. Following outfitting groups are utilized in the weight calculation procedure:

Hatchway covers

Living quarters

Machinery space outfitting

Miscellaneous

Main equipment

1.2.1 Hatchway covers

This group includes all cargo hatches and any internal drive mechanisms. The hatchway cover weight can be

approximated using a formula given by Malzahn [x]. The weight of single-pull covers on the weather deck

carrying a load of 1.75 t/m2 estimated with the following formula:


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Where Wl is the cover weight in tons, l is the cover length and d is the cover breadth. For all 5 hatchway covers

this gives a total weight of 173.4 t.

1.2.2 Living quarters

The equipment and outfitting in the living quarters include:

Cabin and corridor walls if not classed as steel weight.

Deck covering, wall and deck ceiling with insulation.

Sanitary installations and associated pipes.

Doors, windows, portholes.

Heating, ventilation, air-conditioning and associated pipes and trunking.

Outfitting weight in the living quarters can be related to the total area of these spaces. Typically for small and

medium sized cargo ships area weight for living quarters is 160-170kg/m2. In this case all interior spaces except

engine casings in decks 5, 6 and 7 are considered living quarters. Total area of these spaces is about 1051 m2.

By using area weight of 170kg/m2 this gives total living quarter outfitting weight of 178.7 t.

1.2.3 Machinery space outfitting

Machinery space outfitting includes all machinery components except main engines, generators, emergency

generator and propulsion unit system components.

This includes pumps, pipes, sound absorbers, cables, distributors, replacement parts, stairs, platforms, gratings,

daily service tanks, air containers, compressors, degreasers, oil cooler, cooling water system, control

equipment, control room, heat and sound insulation in the engine room, water and fuel in pipes, engines and

boilers. The weight of this group can be roughly estimated as a function of engine power P with the following

formula:

The lower values are used for more powerful units of over 10MW. As the total engine output of the project

ship is 19.1 MW, a lowest value coefficient of 0.04 is used. This gives total machinery outfitting weight of 765.6

t.

1.2.4 Miscellaneous

This group includes most of the equipment that are not yet taken into account in other groups including:

Anchors, chains, hawsers.

Anchor-handling and mooring winches, chocks, bollards, hawse pipes.

Wheelhouse console, control console

Protection, deck covering outside accommodation area.

Davits, boats and life rafts plus mountings.

Railings, gangway ladders, stairs, ladders, doors (outside living quarters), manhole covers.

Awning supports, tarpaulins.

Fire-fighting equipment, CO2 systems, fire-proofing.

Pipes, valves and sounding equipment (outside the engine room and living quarters)

Hold ventilation system.

Nautical devices and electronic apparatus, signaling systems.


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Boatswain’s inventory.

The final weight group is primarily a function of the ship’s size. There is a less marked dependence on ship type.

The weight of this group can be approximated by the following formula:

At this design state a value of 0.26t/m2 is used for C due to lack of better knowledge. This should give a

conservative estimation of the actual weight of this group. Calculated total weight of this group is 400.2 ton.

1.2.5 Main equipment

This group consists of the heaviest individual components that are shown in Table 1. Positions of these

equipment are well known so they can be taken into account when calculating center of gravity for the

outfitting weight.

Table 1 Main equipment

Main equipment

vertical location CoG

longitudinal location CoG

total mass

m m t

Generator Sets 10 26 292

Emergency Generator 16 18 10

Pod unit 7 12 399

Propeller 3 16 40

TOTAL 741

1.2.6 Outfitting total weight

Total outfitting weight is the sum of weight groups calculated above. Summary of outfitting weights and the

total weight is presented in Table 2.

Table 2 Total outfitting weight

Weight group Weight [t]

Hatchway covers 173,4

Living quarters 178,7

Machinery spaces 765,5

Main equipment 741,0

Miscellaneous 400,2

TOTAL: 2258,8


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1.2.7 Comparison of results

Due to the fact that there are no build arctic double acting ore carriers with ice class POLAR-10, comparison of

weight calculation results to the existing ships is a challenging task. As the ice strengthening has a massive

impact to the steel weight, it is not feasible to compare result with similar size ore carriers with different ice

class or no ice class at all. It is also not feasible to compare result with different types of ships, even if they had

the same ice class.

Weight value used in the intact stability calculations is taken as the sum of steel weight calculated using area

weights and outfitting weight calculated with formulas in the previous section. These calculation methods gave

the most conservative results. In addition, 10% reserve is added to the total weight. This gives a total

lightweight of 9405 ton that will be used in stability calculations.

2 CENTER OF GRAVITY

The location of the center of gravity for the vessel is calculated both in longitudinal and vertical direction. The

vertical distance of the center of gravity (VCOG) is measured from the baseline and the longitudinal distance

(LCOG) towards bow from frame #140, which is the mid frame of the ship.

Calculation of the COG is based on the previously calculated weights of the structural members and weights

and locations of major outfitting equipment such as main engines, propulsion unit and anchoring gear. As the

locations of these members are known, the locations of the COGs can be approximated. For the calculations of

center of gravity only the weights of large main equipment is taken into account as those are the most local

weight components. Other globally large weight components, such as pipes, are more evenly distributed over

the extent of the ship and have thus smaller effect on the center of gravity calculations and can be omitted at

this phase of design.

For members of large quantity, such as frames, the COGs are combined to one approximated location. The

ships total COGs are then calculated by taking a mass-weighted arithmetic mean of the location coordinates.

Resulting COGs for the ship and different components of the ship are presented in Table 3. More thorough

spreadsheet is presented in Appendix B: CoGs and Total Weights.

Table 3 Weights CoGs the of Ship and components


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3 INTACT STABILITY

3.1 INITIAL GM ESTIMATE At first the metacentric height, GM, of the ship is estimated using approximate formulas [1]. This will give some

reference for the more accurate stability results to be taken from NAPA and if the values are reasonable. A

loading case where the cargo holds are full is used for this calculation. The metacentric height can be calculated

with the following equation

𝐺𝑀 = 𝐾𝐵 + 𝐵𝑀 −𝐾𝐺,

where KB is the vertical location of the center of buoyancy from the base line and BM is the metacentric radius.

They can be calculated with the following equations

𝐾𝐵 =𝑇(2.5 − 𝐶𝑤𝑝)

3

𝐵𝑀 =𝐼𝑇∇

where IT is the transversal moment of the water plane area and Cwp is the water plane area coefficient. The

resulting GM at design draught is 4.3 meters, which can be seen from Table 4.

Table 4 Estimate of Metacentric Height With Full Cargo Holds


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3.2 LOADING CONDITIONS Due to the fact that the deadweight distribution in ore carrier is varying greatly based on the loading condition

(iron ore cargo, ballast etc.), NAPA model is used to estimate floating position and metacentric height GM with

different load setups. It is not meaningful to check the stability in every possible loading condition, as there

would be practically infinite amount of different combinations to fill the tanks and cargo holds. Instead we are

using 4 different loading conditions that are considered as the extreme cases. If the vessel fulfills stability

criteria in these extreme loading conditions, it can be assumed that the criterion is also met with all the

“intermediate” cases. Loading conditions used in the stability checks are described in the Table 5. Fuel oil tanks

include MDO day tanks and setting tanks. System fluid tanks include lubrication oil tanks, sludge tanks and

fresh water tanks.

Table 5 Extreme loading conditions

Loading condition Iron ore Fuel oil System fluids

Cargo 1 Full Full Full

Cargo 2 Full Empty Empty

Ballast 1 Empty Full Full

Ballast 2 Empty Empty Empty

Ballast water tanks are filled to achieve design draught and zero trim in every loading conditions. As the vessel

can achieve design draught even in ballast condition 2, it can be said that the ballast water tank capacity is

sufficient in all situations.

Cargo condition 1 shows that the cargo capacity of the vessel is about 20700 ton in normal operation with full

fuel oil stores and system fluid tanks. Total deadweight is about 23460 ton at the design draught. Detailed

loading conditions and stability checks are presented in Appendix C.

3.3 STABILITY CRITERIA Values from the stability calculations of different loading conditions are compared to the required values by

IMO Resolution A.749. IMO requires certain minimum values for metacentric height (GM), righting lever arm

(GZ) and the area under the righting lever curve up to heeling angle 30° and 40° as well as for the area between

those angles. The maximum of GZ should also be located beyond required heeling angle. Required values as

well as attained values for different loading conditions are shown in a Table 6.

Table 6 Stability criteria for different loading conditions

Loading condition GM (m) GZ (m)

AREA30 (mrad)

AREA40 (mrad)

AREA30-40 (mrad)

GZ max angle (deg)

Cargo 1 3.97 1.98 0.54 0.88 0.34 40.14

Cargo 2 3.98 2.03 0.55 0.89 0.35 40.57

Ballast 1 5.41 2.98 0.74 1.22 0.48 48.79

Ballast 2 1.04 2.79 0.65 1.09 0.45 >50.00

Required 0.15 0.20 0.06 0.09 0.03 25.00


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As can be seen, all loading conditions fulfill the criteria by a large margin. This is most likely due to the low KG

of the vessel caused by heavy iron ore cargo located below the waterline. There are also large ballast water

tanks in the double bottom that lower the KG in ballast conditions. These results are similar with the initial GM

estimation calculated earlier.


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REFERENCES

[1] Matusiak J., Short Introduction to Ship Theory (Part 1), Otaniemi 2008


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APPENDIX A: AREA WEIGHTS

Steel Area Weight

Hull

Plate

thickness

Steel

density

Plate area

weight

Stiffener

weight

Stiffener

spacing

Girder

weight

Girder

Spacing

Total

Area

Weight

m kg/m3 kg/m2 kg/m m kg/m m kg/m2

Bottom plating 1,50E-02 8000 120 15,1 0,7 0 2,4 141,6

Tank top 1,30E-02 8000 104 29,8 0,7 0 2,4 146,6

Main deck 2,00E-02 8000 160 23,7 0,7 0 2,4 193,9

Longitudinal BHs 1,50E-02 8000 120 11,1 0,7 0 2,4 135,9

Side plating ice belt 3,60E-02 8000 288 30,2 0,6 259,2 2,4 446,3

Side plating above 2,70E-02 8000 216 15,1 0,7 0 2,4 237,6

Side plating below 2,70E-02 8000 216 15,1 0,7 0 2,4 237,6

Tween deck between BW 1,50E-02 8000 120 11,1 0,7 0 2,4 135,9

Tween deck aft 1,50E-02 8000 120 11,1 0,7 0 2,4 135,9

Girders 1,50E-02 8000 120 11,1 0,7 0 2,4 135,9

Frames 1,50E-02 8000 120 11,1 0,7 0 2,4 135,9

Machinery Deck 1,50E-02 8000 120 23,2 0,9 110 2,4 191,6

Aft hull 2,70E-02 8000 216 25 0,7 130 2,4 305,9

Bow Hull 2,70E-02 8000 216 25 0,7 130 2,4 305,9

Transversal BH mid 2,00E-02 8000 160 0 0,5 0 2,4 160,0

Transversal BH aft 1,50E-02 8000 120 11,1 0,7 0 2,4 135,9

Transversal BH bow 1,50E-02 8000 120 11,1 0,7 0 2,4 135,9

Deckhouse

Plate

thickness

Steel

density

Plate area

weight

Stiffener

weight

Stiffener

spacing

Girder

weight

Girder

Spacing

Total

Area

Weight

m kg/m3 kg/m2 kg/m m kg/m m kg/m2

Aft Weather deck 1,00E-02 8000 80 23,7 0,5 0 1 127,4

4 th deck 5,00E-03 8000 40 5,4 0,9 110 2,4 91,8

5 th deck 5,00E-03 8000 40 5,4 0,9 110 2,4 91,8

6 th deck 5,00E-03 8000 40 5,4 0,9 110 2,4 91,8

7 th deck 5,00E-03 8000 40 5,4 0,9 110 2,4 91,8

Bridge deck 5,00E-03 8000 40 5,4 0,9 110 2,4 91,8

Compass deck 5,00E-03 8000 40 5,4 0,9 110 2,4 91,8

Long BHs 5,00E-03 8000 40 5,4 0,9 110 2,4 91,8

Trans BHs 5,00E-03 8000 40 5,4 0,9 110 2,4 91,8


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APPENDIX B: COGS AND TOTAL WEIGHTS

Hull

vertical

location CoG

longitudinal

location CoGarea mass area quantity total mass total mass mass*VCoG mass*LCoG

m m kg/m2 m2 - kg t t*m t*m

Bottom plating 0 103 141,6 3100 1 438871 439 0 45204

Tank top 3 103 146,6 3100 1 454371 454 1363 46800

Main deck 14 103 193,9 3225 1 625189 625 8753 64394

Longitudinal BHs 7 100 135,9 1400 2 380400 380 2663 38040

Side plating ice belt 10 103 446,3 642 2 573092 573 5731 59028

Side plating above 12,75 103 237,6 304 2 144443 144 1842 14878

Side plating below 4,25 103 237,6 875 2 415750 416 1767 42822

Tween deck between BW 10 103 135,9 725 2 196993 197 1970 20290

Tween deck aft 10 46 135,9 490 1 66570 67 666 3062

Girders 1,5 100 135,9 370 5 251336 251 377 25134

Frames 1,5 100 135,9 151 60 1230866 1231 1846 123087

Machinery Deck 10 22 191,6 630 1 120715 121 1207 2656

Aft hull 8 26 305,9 1480 1 452704 453 3622 11770

Bow Hull 5 164 305,9 1200 1 367057 367 1835 60197

Transversal BH mid 7 103 160,0 110 3 52800 53 370 5438

Transversal BH aft 7 20 135,9 160 5 108686 109 761 2174

Transversal BH bow 7 156 135,9 130 2 35323 35 247 5510

TOTAL 5915 35019 570485

Deckhouse

vertical

location CoG

longitudinal

location CoGarea mass area quantity total mass total mass mass*VCoG mass*LCoG

m m kg/m2 m2 - kg t t*m t*m

Aft Weather deck 16 11 127,4 188 1 23951,2 24,0 383,2 263,5

4 th deck 16 24 91,8 501,6 1 46063,6 46,1 737,0 1105,5

5 th deck 19 24 91,8 501,6 1 46063,6 46,1 875,2 1105,5

6 th deck 22 24 91,8 501,6 1 46063,6 46,1 1013,4 1105,5

7 th deck 25 26,5 91,8 360 1 33060,0 33,1 826,5 876,1

Bridge deck 28 26,5 91,8 360 1 33060,0 33,1 925,7 876,1

Compass deck 31 26,5 91,8 360 1 33060,0 33,1 1024,9 876,1

Long BHs 23,5 25 91,8 335 2 61528,3 61,5 1445,9 1538,2

Trans BHs 23,5 25 91,8 290 2 53263,3 53,3 1251,7 1331,6

TOTAL 376,1 8483,5 9078,1

Equipment

vertical

location CoG

longitudinal

location CoGtotal mass total mass mass*VCoG mass*LCoG

m m kg t t*m t*m

Generator Sets 10 26 292000 292 2920 7592

Emergency Generator 16 18 10000 10 160 180

Pod unit 7 12 380000 380 2660 4560

Anchors 6 155 171000 171 1026 26505

Windlasses 16 155 5000 5 80 775

Lifeboat 16 2 6500 6,5 104 13

Boiler 10 21 23000 23 230 483

Hatch Covers 14 103 170000 170 2380 17510

Propeller 3 16 40000 40 120 640

BW Pumps 3 150 11000 11 33 1650

TOTAL 1108,5 9713 59908


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APPENDIX C-1: LOADING CONDITION CARGO 1


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APPENDIX C-2: LOADING CONDITION CARGO 2


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APPENDIX C-3: LOADING CONDITION BALLAST 1


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APPENDIX C-4: LOADING CONDITION BALLAST 2


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Arctic Bulk Carrier - Aalto

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