(1) The height above deck of hatchway coamings
shall be as specified in regulation 5(1).
Where operating experience has shown justification, and on the approval
by the Administration, the height of these coamings may be reduced,
or the coamings omitted entirely, provided that the safety of vessels
is not thereby impaired. In this case, the hatchway openings shall
be kept as small as practicable and the covers be permanently attached
by hinges or equivalent means and be capable of being rapidly closed
and battened down, or by equally effective arrangements to the satisfaction
of the Administration.
(2) For the purpose of strength calculations,
it shall be assumed that hatchway covers are subjected to the weight
of cargo intended to be carried on them or to the following static
loads, whichever is the greater:
For intermediate lengths the load values shall be determined
by linear interpolation. The Administration may reduce the loads to
not less than 75% of the above values for covers to hatchways situated
on the superstructure deck in a position abaft a point located 0.25L from the forward perpendicular.
(3) Where covers are made of mild steel, the maximum
stress calculated according to paragraph (2) multiplied by 4.25 shall
not exceed the minimum ultimate strength of the material. Under these
loads the deflections shall not be more than 0.0028 times the span.
(4) Covers made of materials other than mild steel
shall be at least of equivalent strength to those made of mild steel,
and their construction shall be of sufficient stiffness ensuring weathertightness
under the loads specified in paragraph (2).
(5) Covers shall be fitted with clamping devices
and gaskets sufficient to ensure weathertightness, or other equivalent
arrangements to the satisfaction of the Administration.