(DB) tanks,topside tanks & wing tanks for bulk carriers ballast handling
All bulk carriers must have ballast tanks of sufficient
capacity to allow immersion of the propeller and
ensure suitable trim and stability.
The ballast conditions of a bulk
carrier are as follows:
Light ballast has empty ballast
- heavy ballast (seagoing
condition), which is with the
ballast holds full
- port condition is for trimming/air draught
situations, using the additional dedicated cargo
ballast holds that are for port use only.
These are tanks of triangular configuration fitted
at both shoulders/wings of the cargo holds. Their
purpose is to carry ballast water.
Topside tanks consist of a `transverse ring' made from
frames in the transverse direction. Each transverse
ring consists of:
The topside tanks are connected to the main ballast
system of the ship. When discharging topside tanks
the BLU Code stipulates that during the loading/
discharging of cargo the discharge rate must remain
constant and that the weight of ballast water should be
harmonized with the weight of the cargo.
- A deck transverse the part of the frame under
the deck supporting the deck plating
- a side transverse the part of the frame
supporting the side shell plating. This is in line
with the side shell frames within the cargo holds
(in single skin bulk carriers)
- a bottom transverse the part of the frame
supporting the bottom part of the topside tank.
Wing Tanks (Lower Hopper Tanks)
These tanks are on the sides of the vessel within
the bottom wing of each cargo hold and are the
continuation of the DB tanks. They provide additional
space for ballast and the sloping margins of the
tanktop to collect the cargo in the central part of the
The fuel tank plating forms a sloping boundary that
carries static and dynamic load due to cargo and
ballast. The transverse frames in the wing tanks are
divided into three types, side transverse, bottom
transverse and bilge transverse, according to the
structure to which they are attached.
In addition to carrying ballast, the upper and lower
wing tanks have the following advantages:
- The space where an untrimmed cargo would
otherwise shift into is occupied by the upper wing
tanks and void space (upper stool), meaning
cargoes such as grain can sometimes be carried
without being trimmed.
- the lower wing tank, combined with the lower void
space, shapes the lower part of the cargo hold
enabling cargo to be easily accessed in the central
part of the hold when discharged with grabs.
Fig : Tanks configuration of a typical bulk carrier
Double Bottom (DB) Tanks
The double bottom is fitted between the forward
collision bulkhead and the after peak bulkhead. Its
top or `inner bottom' forms the deck of the cargo holds
and continues out to the ship's side so that the turn
of the bilge can be protected.
The design of double
bottom tanks is based on the length of the ship, ie
for ships longer than 120 m the arrangement of DB
tanks and sloped bulkheads of wing tanks consists
of longitudinal framing, while for ships of 120 m or
less the arrangement consists of transverse framing
(at least) within the cargo hold. The cargo hold area
directly below the hatchway must be strengthened.
On many ships, the double bottom is divided
transversely into three compartments instead of two.
In this case, there is a central void known as the `duct
keel' where piping may be routed.
As noted earlier, wing tanks and DBs are connected
and form part of the ballast system with the exception
that some DBs are dedicated FO/DO tanks only and
will not be connected to the ballast system, avoiding
any chance of contamination.
Lower hopper and DB tanks in the aft hold can be
fuel tanks while, correspondingly, top side tanks are
Structural strength requirements for mechanical steel hatch covers
Ships structural problem because of corrosion & metal fatigues - related countermeasures
Classification Society Establishes Design Standards For Bulk Carriers
Operation of sea going bulk carriers involved numerous hazards . Careful planning and exercising due caution for all critical shipboard matters are important . This site is a quick reference to international shipping community with guidance and information on the loading and discharging of modern bulk carriers so as to remain within the limitations as specified by the classification society.
It is vital to reduce the likelihood of over-stressing the ship's structure and also complying with all essential safety measures for a safe passage at sea. Our detail pages contain various bulk carrier related topics that might be useful for people working on board and those who working ashore in the terminal. For any remarks please
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"A ship which is intended primarily to carry dry cargo
in bulk, including such types as ore carriers and
- Hatch cover strength requirement for a seagoing bulk carrier
- Countermeasures against ships structural damage
- Ships longitudinal subdivisions - use of transverse watertight bulkheads
- Indication of unusual motion or attitude of bulk carriers and risk management / evacuation
- Deterioration of ships structure and consequences of forward flooding
- Handling water ingress problems in bulk carrier, investigation and countermeasures
- Survival and safety procedure for bulk carriers
- Suitability of Shore Terminals for handling bulk cargo
- Preparation for ships carrying bulk cargo & standard loading condition