Regulation 27 - Types of Ships

  (1) For the purposes of freeboard computation ships shall be divided into Type 'A' and Type 'B'.

  Type 'A' ships

  (2) A Type 'A' ship is one which is designed to carry only liquid cargoes in bulk, and in which cargo tanks have only small access openings closed by watertight gasketed covers of steel or equivalent material.

Such a ship necessarily has the following inherent features:

• (a) high integrity of the exposed deck; and

• (b) high degree of safety against flooding, resulting from the low permeability of loaded cargo spaces and the degree of subdivision usually provided.

  (3) A Type 'A' ship, if over 150 metres (492 feet) in length, and designed to have empty compartments when loaded to its summer load waterline, shall be able to withstand the flooding of any one of these empty compartments at an assumed permeability of 0.95, and remain afloat in a condition of equilibrium considered to be satisfactory by the Administration. In such a ship, if over 225 metres (738 feet) in length, the machinery space shall be treated as a floodable compartment but with a permeability of 0.85.

For the guidance of Administrations the following limits may be regarded as satisfactory:

• (a) the final waterline after flooding is below the lower edge of any opening through which progressive flooding may take place;

• (b) the maximum angle of heel due to unsymmetrical flooding is of the order of 15 degrees;

• (c) the metacentric height in the flooded condition is positive.

  (4) A Type 'A' ship shall be assigned a freeboard not less than that based on Table A of Regulation 28.

  Type 'B' ships

  (5) All ships which do not come within the provisions regarding Type 'A' ships in paragraphs (2) and (3) of this Regulation shall be considered as Type 'B' ships.

  (6) Type 'B' ships, which in position 1 have hatchways fitted with hatch covers complying with the requirements of Regulation 15 (7) or 16 shall, except as provided in paragraphs (7) to (10) inclusive of this Regulation, be assigned freeboards based on Table B of Regulation 28.

  (7) Any Type 'B' ships of over 100 metres (328 feet) in length may be assigned freeboards less than those required under paragraph (6) of this Regulation provided that, in relation to the amount of reduction granted, the Administration is satisfied that:

• (a) the measures provided for the protection of the crew are adequate;

• (b) the freeing arrangements are adequate;

• (c) the covers in positions 1 and 2 comply with the provisions of Regulation 16 and have adequate strength, special care being given to their sealing and securing arrangements;

• (d) the ship, when loaded to its summer load waterline, will remain afloat in a satisfactory condition of equilibrium after flooding of any single damaged compartment at an assumed permeability of 0.95 excluding the machinery space; and

• (e) in such a ship, if over 225 metres (738 feet) in length, the machinery space shall be treated as a floodable compartment but with a permeability of 0.85.

For the guidance of Administrations in applying sub-paragraphs (d) and (e) of this paragraph the limits given in sub-paragraphs (3) (a), (b) and (c) may be regarded as satisfactory.

The relevant calculations may be based upon the following main assumptions:

• the vertical extent of damage is equal to the depth of the ship;
• the penetration of damage is not more than B/5;
• no main transverse bulkhead is damaged;
• the height of the centre of gravity above the base line is assessed allowing for homogeneous loading of cargo holds, and for 50 per cent of the designed capacity of consumable fluids and stores, etc.

  (8) In calculating the freeboards for Type 'B' ships which comply with the requirements of paragraph (7) of this Regulation, the values from Table B of Regulation 28 shall not be reduced by more than 60 per cent of the difference between the 'B' and 'A' tabular values for the appropriate ship lengths.

  (9) The reduction in tabular freeboard allowed under paragraph (8) of this Regulation may be increased up to the total difference between the values in Table A and those in Table B of Regulation 28 on condition that the ship complies with the requirements of Regulation 26 (1), (2), (3), (5) and (6), as if it were a Type 'A' ship, and further complies with the provisions of paragraph (7) (a) to (d) inclusive of this Regulation except that the reference in sub-paragraph (d) to the flooding of any single damaged compartment shall be treated as a reference to the flooding of any two adjacent fore and aft compartments, neither of which is the machinery space. Also any such ship of over 225 metres (738 feet) in length, when loaded to its summer load waterline, shall remain afloat in a satisfactory condition of equilibrium after flooding of the machinery space, taken alone, at an assumed permeability of 0.85.

  (10) Type 'B' ships, which in position 1 have hatchways fitted with hatch covers which comply with the requirements of Regulation 15, other than paragraph (7), shall be assigned freeboards based upon the values given in Table B of Regulation 28 increased by the values given in the following table:

Freeboards at intermediate lengths of ship shall be obtained by linear interpolation.

Ships above 200 metres in length shall be dealt with by the Administration.

Freeboards at intermediate lengths of ship shall be obtained by linear interpolation.

Ships above 660 feet in length shall be dealt with by the Administration.

  (11) A lighter, barge or other ship without independent means of propulsion shall be assigned a freeboard in accordance with the provisions of these Regulations. However, in the case of barges which are unmanned the requirements of Regulations 25, 26 (2) and (3) and 39 shall not apply. Such unmanned barges which have on the freeboard deck only small access openings closed by watertight gasketed covers of steel or equivalent material may be assigned freeboards 25 per cent less than those calculated in accordance with these Regulations.