bulk carriers 2

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Bulk carriers

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BULK CARRIERS“a ship constructed with a single

deck, top side tanks and hopper

side tanks in cargo spaces and

intended to primarily carry dry

cargo in bulk; an ore carrier; ora combination carrier ”

(International Convention for

the Safety of Life at Sea, 1999).

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dry bulk carrier is used to distinguish bulk carriers from bulk liquid

carriers such as:

• oil,

• chemical, or

• liquefied petroleum gas carriers.

OBO - a bulk carrier which carries a combination of ore, bulk , and oil .

"O/O" is used for combination oil and ore carriers.

VLOC, ULOC, VLBC and ULBC - very large and ultra large ore and bulk

carriers.

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Bulk carriers of all types have certain features in common:

1. Single cargo deck, without ’tween decks.

2. Machinery aft of cargo spaces so shaft tunnel does not interfere with

discharging gear.3. Large ballast capacity.

4. Double bottoms under bulk cargo holds.

To facilitate rapid cargo discharge & minimise cleaning requirements,

holds are designed with a minimum of internal obstructions that mightcatch and hold cargo.

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all kinds of dry cargo in bulk,

large cargo hold volume,

hatchways as large as possible,to accelerate the discharge ofcargo,

all holds should be self-trimming to facilitate loading,

the number of holds such as topermit the loading of varioustypes of e.g. grain and also to

ensure full holds,

the ballast capacity should besuch as to ensure immersion ofthe propeller and reasonabletrim.

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Cross section of a typical bulker

1. Cargo hold

2. Hatch cover

3. Upper hopper tank for water

ballast or oil (uzvojni tank)

4. Double bottom

5. Lower hopper tank, for water

ballast (lower side ballast tank in abulk carrier, shaped & positioned to

create a hopper form to the cargo hold ).

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Hopper hold – found in bulk carriers; they

have the cut-away corners found in some

hoppers behind which are hoppered tanks

used for ballast or for stability when carrying

certain cargo.

http://en.wikipedia.org/wiki/File:Bulk_carrier_midship_section-i18.svg


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Structural configurationSingle deck ship with a double

bottom 1

Hopper tanks (donji bočni tank) 2

Single skin transverse framed sideshell (jednostruka poprečna oplata boka)3

Topside tanks 4

Deck hatchways 5

End brackets (završne konzole) 6

Corrugated transverse bulkheads(naborane poprečne pregrade)7

Typical structural arrangement of a bulk carrier cargo hold space

Corrugated (especially of sheets of iron or

cardboard) having parallel rows of folds which

look like a series of waves when seen from the edge

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1.

2.

3.

4.

5.

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1. side-rolling hatch covers - reduce cargo-handling time during loading and unloading,

2. self-trimming cargo holds,

3. Hoppers (donji bočni tank),

4. saddle tank - serves to shape the upper region ofthe cargo hold and trim the cargo,

5. double bottom ballast tank,

6. Cofferdam (koferdam, međuprostor, pregrada),

7. wing ballast tank (bočni balastni tank).

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A typical transverse section of a

cargo hold

In general

• the plating (oplata): 1. side shell,

2. bottom shell, 3. strength deck, 4. inner

bottom, 5. topside and hopper tank sloping

plating provides boundaries of thestructure & carries static & dynamic

pressure loads exerted by e.g. the cargo,

ballast and the sea.

The plating is supported by secondary

stiffening members such as frames orlongitudinal.

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1.

2.

3.

4.

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Specific safety concerns related to this type ofship Loading of cargo must be done carefully,

ensure cargo cannot shift during a voyage leading to stability problems,

large hatch covers must be watertight and secure.

The International Maritime Solid Bulk Cargoes Code (IMSBC Code), & amendments to

SOLAS chapter VI to make the Code mandatory, were adopted by the Maritime Safety Committee

(MSC), 85th session, in 2008.

The amendments expected to enter into force on 1 January 2011.

The IMSBC Code replaces the Code of Safe Practice for Solid Bulk Cargoes (BC Code), which

was first adopted as a recommendatory code in 1965 and has been updated at regular

intervals since then.

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The aim of the mandatory IMSBC Code is: to facilitate the safe stowage and shipment of solid bulk cargoes by providing information on

the dangers associated with the shipment of certain types of cargo and instructions on theappropriate procedures to be adopted.

The Code

highlights the dangers associated with the shipment of certain types of bulk cargoes, gives guidance on various procedures which should be adopted; lists typical products which are shipped in bulk, gives advice on their properties & how they should be handled, and describes various test procedures which should be employed to determine the characteristic

cargo properties.

The Code contains a number of general precautions & says it is of fundamental importancethat bulk cargoes be properly distributed throughout the ship so that the structure is notoverstressed and the ship has an adequate standard of stability. Code of Practice for the safeloading and unloading of bulk carriers (resolution A.862(20).

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Overloading the cargo in insufficient draft

results in an excessive vertical load on the double bottom which maydistort the overall structural configuration:

Sheer stress

in transverse

corrugated

bulkhead

Cargoweight

Buoyancy force

Buoyancy force

Cargo weight

Excessive deformation of

the double bottom

structure

Sheering of the transverse

corrugated bulkhead &

the comprehension of the

deck

Buoyancy force

Corrugated (especially of sheets of iron or cardboard) having

parallel rows of folds which look like a series of waves when seen from the edge

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Cargo distributions along the ships length – direct

influence on the bending & shearing of the hull girder

& on the stress in the hull

Homogenous hold loading conditions

(fully loaded)

Block hold loading conditions

Alternate hold loading conditions

(fully loaded)

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Stages in the development of a plan forloading/unloading

• 1. given the intended voyage the amount of cargo and/or

water ballast to be carried & imposed operational limits ,create a departure condition: develop a stowage plan.

• 2. given the arrival condition & having the stowage plan,

plan loading/unloading according to imposed operationallimits.

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A cargo loading/unloading plan should demonstrate an

Indication of:

The quantity of cargo & the corresponding hold number to beladed/unladed.

The amount of water ballast & the corresponding tank / hold

number to be discharged / loaded.

The ship’s draft & trim.

Estimated time for completion of each step.

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