(1) At positions 1 and 2 the height above the
deck of hatchway coamings fitted with weathertight hatch covers of
steel or other equivalent material fitted with gaskets and clamping
devices shall be as specified in Regulation
15 (1). The height of these coamings may be reduced, or the
coamings omitted entirely, on condition that the Administration is
satisfied that the safety of the ship is not thereby impaired in any
sea conditions. Where coamings are provided they shall be of substantial
construction.
(2) Where weathertight covers are of mild steel
the strength shall be calculated with assumed loads not less than
1.75 metric tons per square metre (358 pounds per square foot) on
hatchways in position 1, and not less than 1.30 metric tons per square
metre (266 pounds per square foot) on hatchways in position 2, and
the product of the maximum stress thus calculated and the factor of
4.25 shall not exceed the minimum ultimate strength of the material.
They shall be so designed as to limit the deflection to not more than
0.0028 times the span under these loads. Mild steel plating forming
the tops of covers shall be not less in thickness than one per cent
of the spacing of stiffeners or 6 millimetres (0.24 inches) if that
be greater. The provisions of Regulation
15 (5) are applicable for ships of not more than 100 metres
(328 feet) in length.
(3) The strength and stiffness of covers made
of materials other than mild steel shall be equivalent to those of
mild steel to the satisfaction of the Administration.
Means for Securing Weathertightness
(4) The means for securing and maintaining weathertightness
shall be to the satisfaction of the Administration. The arrangements
shall ensure that the tightness can be maintained in any sea conditions,
and for this purpose tests for tightness shall be required at the
initial survey, and may be required at periodical surveys and at annual
inspections or at more frequent intervals.