Section 1 General

101. Application

1. Barges of 90 m and above in length are to be provided with double bottoms. However, they may be provided with single bottoms subject to the approval by the Society.

2. The requirements in this chapter may be suitably modified, where partial double bottoms are pro- vided and where longitudinal bulkheads are made to reduce the unsupported breadth of double bottoms.

3. Where the longitudinal system of framing is transformed into the transverse system, or depth of double bottom changes suddenly, special care is to be taken for the continuity of strength by means of additional intercostal girders or floors.

4. Bottom structure of holds intended to carry heavy cargoes is to be subjected to special consideration.

102. Manholes and lightening holes

1. Manholes and lightening holes are to be provided in all non-watertight members to ensure accessi- bility and ventilation, except in way of widely spaced pillars and where such openings are not per- mitted by this rule.

2. The number of manholes in tank tops is to be kept to the minimum compatible with securing free ventilation and ready access to all parts of the double bottom. Care is to be taken for locating the manholes to avoid the possibility of inter connection of main subdivision compartments through the double bottom so far as practicable.

3. Covers of manholes specified in Par 2 are to be of steel, and where no ceiling is provided in the

cargo holds, the covers and their fittings are to be effectively protected against damages by cargoes.

4. Air and drainage holes are to be provided in all non-watertight members of the double bottom structures. The proposed locations and sizes of manholes and lightening holes are to be indicated in the plans submitted for approval.

5. The proposed location and size of manholes and lightening holes are to be indicated in the plans submitted for approval.

103. Drainage

1. Efficient arrangements are to be provided for draining water on the tank top.

2. Where wells are provided for the foregoing purpose, such wells are not to extend for more than one- half depth of the double bottom nor less than 457 mm from the bottom shell, as far as practicable.

104. Watertight girders

The thickness of watertight girders and floors, and the scantlings of stiffeners attached to them are to comply with the relevant requirements for girders and floors, as well as the requirements in Ch 14, 202. and 203.

105. Minimum thickness

No member of the double bottom structure is to be less than 6 mm in thickness.