Ships are divided into types ‘A’ and ‘B’.
Type ‘A’ ships are those which are designed to carry only liquid cargoes in bulk, and in which the cargo tanks have only small access openings closed by watertight gasketed covers of steel or equivalent material.
These vessels benefit from the minimum assignable freeboard. All ships which do not come within the provisions regarding Type ‘A’ ships are considered as Type ‘B’ ships.
As a considerable variety of ships will come within the Type ‘B’ category, a reduction or increase from the basic table Type ‘B’ freeboard is made in the following cases:
In other words we can understand type A and B as :
For the purpose of assigning freeboards a type ‘A’ ship is one which:
- Is designed to carry only liquid cargoes in bulk;
- Has a high integrity of the exposed deck with only small access openings to cargo compartments, closed by watertight gasketed covers of steel or equivalent material, and;
- Has a low permeability of loaded cargo compartments.
A type ‘A’ ship if over 150 m in length to which a freeboard less than type ‘B’ has been assigned, when loaded in accordance with the assumed initial condition of loading, shall be able to withstand the flooding of any compartment or compartments, with an assumed permeability of 0.95, consequent upon the damage assumptions specified, and shall remain afloat in a satisfactory condition of equilibrium. In such a ship the machinery space shall be treated as a floodable compartment, but with a permeability of 0.85.