ESLORA_INUNDABLE-_BILGING[2)

8/12/2019 ESLORA_INUNDABLE-_BILGING[2)

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Flooding & Damaged Stability

So far we consider the stability of an intact ship. In the event ofcollision or grounding, water may enter the ship. If flooding isnot restricted, the ship will eventually sink. To prevent this, thehull is divided into a number of watertight compartments by

watertight bulkheads .

Transverse (or longitudinal) watertight bulkheads can

Minimize the loss of buoyancy

Minimize the damage to the cargo

Minimize the loss of stability


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Too many watertight bulkheads will increase cost & weight of the

ship. It is attempted to use the fewest watertight bulkheads toobtain the largest possible safety (or to satisfy therequirement of rule ).

Forward peak bulkhead (0.05 L from the bow)After peak bulkheadEngine room: double bottomTanker: (US Coast Guard) Double Hull (anti pollution)


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EFECTOS


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Trim when a compartment is open to Sea

0 0

1 1

W.L. before the damage

W.L. after the damage

W L

W L

If W 1 L 1 is higher at any point than the main deck at which the bulkheads stop (the bulkhead deck ) it is usually consideredthat the ship will be lost (sink) because the pressure of waterin the damaged compartments can force off the hatches andunrestricted flooding will occur all fore and aft.


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THE EFFECTS OF BILGING AN EMPTY AMIDSHIPS COMPARTMENT

The changes in draught and stability when a compartment becomes floodeddue to damage can be investigated by either of two methods:(1) the lost buoyancy (constant displacement) method, or;(2) the added weight method.


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Los t buoyancy ( cons tan td isp lacement) method

So it is assumed that the sinkage of the

vessel is caused by the redistribution ofthe intact underwater volume. Sincenothing has been loaded and theeffective volume of displacement is thesame, the assumptions of this approachare:(1)Volu m e of displacem ent (anddisplacement) remain cons tant , and;(2)KG remains c ons tant


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Added weigh t method

This assumes that the floodwater entering the ship increases the displacement and affectsthe ships KG by reason of the effect of added mass and (in some cases) the effect of theintroduced free surface. Essentially the problem is approached in the same way that wouldapply when a tank is either partially or fully filled during routine ship operations.


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EJERCICIO 1

A box-shaped vessel has length 75 m, breadth 12 m and is floating on an even keel draught insalt water of 2.5 m. In this condition the KG is 3.00 m. An empty forward end compartment oflength 6 m extending the full breadth and depth of the vessel is bilged.Calculate the draughts in the flooded condition.

EJERCICIOS PA RA DESARROLL AR EN CLA SE

EJERCICIO 2


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Asymmetric flooding

1. If the inclination angle is large,then the captain should let thecorresponding tank flooding.Then the flooding is

symmetric.2. If the inclination angle is small,

w

Lost buoyancy :

Heeling moment:

sin ,

sin ,

is the inclination angle.

w

w

w

v

v y

GM v y

vy

GM

COMUNICACIN LIBRE CONEL MAR


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Floodable length and its computation

Floodable Length : The F.L . at any point within the length ofthe ship is the maximum portion of the length, having its centerat the point which can be symmetrically flooded at the

prescribed permeability, without immersing the margin line .


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Bulkhead deck : The deck tops the watertight bulkhead

Margin line : is a line 76 mm (or 3) below the bulkheadat the side of a ship

Without loss of the ship: When the W.L. is tangent to

the margin line.

Floodable length (in short) The length of (part of) theship could be flooded without loss of the ship.

Determine Floodable length is essential to determine1. How many watertight compartments (bulkheads) needed2. Factor of subdivision (How many water compartments

flooded without lost ship)


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0 0 0 0

1 1

1 1 1 1

1 0

Steps for computing the F.L. given , , or

1) Obtain a limit W.L.: ,

2) using the Bonjean Curves to obtain and under .3) , is the loss of buoyancy due to the flooding.

B W L

W L

B W Lv v

1 0 11 0 1 1 01 0

0

1 0 0 0

4) ,

is the distance of the center of the lost buoyancy from .5) , is the area of the cross section, is the F.L.

Setting a half of on either

B B B B v x x x

x Bv A l A l

l

0

sideof the center of lost Buoyancy.

Near the ends of a ship, ischanging rapidly then using theiterative process to determine .

A

l


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6) Repeating (1) to (5) for

a series of . .s tangent to

the margin line at different positions in the length of the

ship. Then a series of valuesof the F.L. can be obtainedfor different positions a

W L

long

the ship.7) Considering the different

permeability coefficientsat different positions alongthe ship.


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8) Factor of Subdivision F

Factor of subdivision is the ratio of a permissible length tothe F.L.

For example, if F is 0.5, the ship will still float at a W.L. under

the margin line when any two adjacent compartments of theship are flooded. If F is 1.0, the ship will still float at aW.L . under the margin line when any one compartment ofthe ship is flooded.

Rules and regulations about the determination of F are set bymany different bureaus all over the world (p126-127)


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Clculo FL Mtodo grfico

1. Calcular V diferentes WL2. Calcular v de avera (damage water)3. Calcular centroides4. Calcular curva de rea para cada condicin de WL y curva de volumen5. Calcular l grficamente

0nv V V

0 0

0

n n

n

V x V x x

V V

0

V

V

= En la condicin deInundacin WL1

= En calado de diseox1

x2

l= x1-x2


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Seccin transversaltpica

Cubierta ppal

D

B = 5

B = 5

Perfil

2,5

2,0

20

2,0 1,5Teniendo en cuenta la geometra dela embarcacin presentada abajo,generar la curva de flotacincorrespondiente.

El calado de diseo ser T = 1,0 m .Para facilitar el clculo, realizar almenos 5 condiciones de inundacin:dos hacia popa, dos hacia proa y 1en la inundacin mxima, en la franjade reserva de flotacin a 76 mm dela cubierta principal. El coeficientede permeabilidad de la embarcacinser n= 0,95Las dimensiones presentadas en losesquemas estn dadas en m.

EJERCICIO EN GRUPOS


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AREAS PARA LAS DIFERENTES LINEAS DE TRIMADO

LEVER

CALADO

DEDISEO W1 W2 WMAX W4 W3

0 0.00 2.12 2.12 2.12 0.58 0

1/2 1.25 5.72 5.80 5.87 4.51 2.91

1 5.00 9.31 9.47 9.62 8.24 6.81

2 5.00 9.00 9.31 9.62 8.39 7.13

3 5.00 8.68 9.16 9.62 8.54 7.44

4 5.00 8.37 9.01 9.62 8.70 7.755 5.00 8.06 8.85 9.62 8.85 8.06

6 5.00 7.74 8.70 9.62 9.01 8.37

7 5.00 7.43 8.54 9.62 9.16 8.68

8 5.00 7.12 8.39 9.62 9.31 8.99

9 3.50 5.36 6.74 8.12 7.97 7.80

9 1/2 0.50 2.15 3.66 5.12 5.04 4.96

10 0.00 0.00 0.58 2.12 2.12 2.12


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ESLORA_INUNDABLE-_BILGING[2)