Section 45.147 - Hatchway coamings(a) Except where the Commandant determines that the safety of the vessel will not be impaired in any sea condition, each hatchway must have a coaming that is at least- (1) 18 inches in position 1; and(2) 12 inches in position 2.(b) Each hatchway coaming required by this section must be made of steel or equivalent material.(c) The height of these coamings may be reduced or omitted if the Commandant is satisfied that safety of the ship is not thereby impaired in any sea conditions.