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  Tonnage Rules        


Legislative Requirements



SOLAS - Carriage of Grain

Intact Stability

The intact stability characteristics of any ship carrying bulk grain shall be shown to meet, throughout the voyage, at least the following criteria after taking into account in the manner described in part B of this Code and, in figure the heeling moments due to grain shift:

.1 the angle of heel due to the shift of grain shall not be greater than 12˚ or in the case of ships constructed on or after 1 January 1994 the angle at which the deck edge is immersed, whichever is the lesser;

.2 in the statical stability diagram ‘the net or residual area between the heeling arm curve and the righting arm curve up to the angle of heel of maximum difference between the ordinates of the two curves, or 40˚ or the angle of flooding (θ), whichever is the least, shall in all conditions of loading be not less than 0.075 metre-radians; and

.3 the initial metacentric height, after correction for the free surface effects of liquids in tanks, shall be not less than 0.30 m.

Before loading bulk grain the master shall, if so required by the Contracting Government of the country of the port of loading, demonstrate the ability of the ship at all stages of any voyage to comply with the stability criteria required by this section.

After loading, the master shall ensure that the ship is upright before proceeding to sea.

Stability requirements for existing ships

For the purposes of this section the term existing ship means a ship the keel of which is laid before 25 May 1980.

An existing ship loaded in accordance with documents previously approved under regulation 12 of chapter VI of SOLAS 1960, IMO resolutions shall be considered to have intact stability characteristics at least equivalent of this Code. Documents of authorization permitting such loadings shall be accepted for the purposes of masters ability to show that the ship would be able to comply at all sections of the voyage (stated earlier).

Existing ships not having on board a document of authorization may apply the provisions of ‘Optional stability requirements for ships without documents’ (below paragraph), without limitation on the deadweight, which may be used for the carriage of bulk grain.

Optional Stability requirements for ships without documents of authorization carrying partial cargoes of bulk grain

A ship not having on board a document of authorization may be permitted to load bulk grain provided that:

.1 the total weight of the bulk grain shall not exceed one third of the deadweight of the ship;

.2 all filled compartments, trimmed, shall be fitted with centreline divisions extending, for the full length of such compartments, downwards from the underside of the deck or hatch covers to a distance below the deck line of at least one eighth of the maximum breadth of the compartment or 2.4 m, whichever is the greater, except that saucers may be accepted in lieu of a centreline division in and beneath a hatchway except in the case of linseed and other seeds having similar properties;

.3 all hatches to filled compartments, trimmed, shall be closed and covers secured in place;

.4 all free grain surfaces in partly filled cargo space shall be trimmed level and

.5 throughout the voyage the metacentric height after correction for the free surface effects of liquids in tanks shall be 0.3 m or that given by the following formula, whichever is the greater:

GMR =             L B Vd (0.25 B - 0.645 sqrt of (Vd B))

SF x A x 0.0875


L = total combined length of all full compartments (metres)

B    = moulded breadth of the vessel (metres)

SF   = stowage factor (cubic metres per tonne)

Vd   = calculated average void depth calculated in accordance with B 1 (metres - Note: not millimetres)

A    = displacement (tonnes); and

.6 the master demonstrates to the satisfaction of’ the Administration or the Contracting Government of the port of loading on behalf of the Administration that the ship in its proposed loaded condition will comply with the requirements of this section.

Document of authorization

A document of authorization shall be issued for every ship loaded in accordance with the regulations of this Code either by the Administration or an organization recognized by it or by a Contracting Government on behalf of the Administration.  It shall be accepted as evidence that the ship is capable of complying with the requirements of these regulations.

The document shall accompany or be incorporated into the grain loading manual provided to enable the master

Such a document, grain loading stability data and associated plans may be drawn up in the official language or languages of the issuing country.  If the language used is neither English nor French, the text shall include a translation into one of these languages.

A copy of such a document, grain loading stability data and associated plans shall be placed on board in order that the master, if so required, shall produce them for the inspection of the Contracting Government of the country of the port of loading.

A ship without such a document of authorization shall not load grain until the master demonstrates to the satisfaction of the Administration, or of the Contracting Government of the port; of loading acting on behalf of the Administration, that, in its loaded condition for the intended voyage, the ship complies with the requirements of this Code. 

Information regarding ship’s stability and grain loading

Information in printed booklet form shall be provided to enable the master to ensure that the ship complies with this Code when carrying grain in bulk on an international voyage.  This information shall include the following.

Information which shall be acceptable to the Administration or to a contracting Government on behalf of the Administration shall include:

.1 ship’s particulars;

.2 lightship displacement and the vertical distance from the intersection of the moulded base line and midship section to the centre of gravity (KG);

.3 tables of liquid free surface corrections;

.4 capacities and centres of gravity;

.5 curve or table of angle of flooding, where less than 40˚’, at all permissible displacements;

.6 curves or tables of hydrostatic properties suitable for the range of operating drafts; and

.7 cross curves of stability which are sufficient for the purpose of the requirements and which include curves at 12˚ and 40˚.

Information which shall be approved by the Administration or by a contracting Government on behalf of the Administration shall include:

.1         curves or tables of volumes, vertical centres of volumes, and assumed volumetric heeling moments for every compartment, filled or partly filled, or combination thereof, including the effects of temporary fittings;

.2         tables or curves of maximum permissible heeling moments for varying displacements and varying vertical centres of gravity to allow the master to demonstrate compliance with the requirements; this requirement shall apply only to ships the keels of which are laid on or after the entry into force of this Code;

.3         details of the scantlings of any temporary fittings and, where applicable, the provision is necessary to meet the requirements of the code;

.4         loading instructions in the form of notes summarizing the requirements of this Code;

.5         a worked example for -the guidance of the master; and

.6         typical loaded service departure and arrival conditions and where necessary intermediate worst service conditions.

It is recommended that loading conditions be provided for three representative stowage factors, example - 1.25, 1.50, and 1.75 cubic metres per tonne.