2 Small Hatchways Fitted on the Exposed Fore Deck

2.1 General

2.1.1

These requirements apply to small hatchways (generally openings 2.5 m² or less) on the exposed deck within 0.25 L from the FP and located at a height less than 0.1 L or 22 m, whichever is less, from the summer load water line at the location of the hatch.

2.1.2

Hatchways designed for emergency escape need not comply with the requirements [2.3.1] items (a) and (b), [2.4.3] and [2.5.1].

2.1.3

Securing devices of hatches designed for emergency escape are to be of a quick-acting type (e.g. one action wheel handles are provided as central locking devices for latching/unlatching of hatch cover) operable from both sides of the hatch cover.

2.2 Strength

2.2.1

For small rectangular steel hatch covers, the gross plate thickness, stiffener arrangement and scantlings are to be not less than those obtained, in mm, from Table 1 and Figure 2. Stiffeners, where fitted, are to be aligned with the metal-to-metal contact points, required in [2.4.1] and shown in Figure 2. Primary stiffeners are to be continuous. All stiffeners are to be welded to the inner edge stiffener, see Figure 1.

2.2.2

The upper edge of the hatchway coaming is to be suitably reinforced by a horizontal member, normally not more than 190 mm from the upper edge of the coaming.

2.2.3

For small hatch covers of circular or similar shape, the cover plate thickness and reinforcement is to provide strength and stiffness equivalent to the requirements for small rectangular hatches.

2.2.4

For small hatch covers constructed of materials other than normal strength steel, the required scantlings are to provide equivalent strength and stiffness.

2.3 Primary securing devices

2.3.1

Dogs (twist tightening handles) with wedges are not acceptable.

2.4 Requirement to primary securing

2.4.1

The hatch cover is to be fitted with a gasket of elastic material. This is to be designed to allow a metal to metal contact at a designed compression and to prevent over compression of the gasket by green sea forces that may cause the securing devices to be loosened or dislodged. The metal-to-metal contacts are to be arranged close to each securing device in accordance with Figure 2 and of sufficient capacity to withstand the bearing force.

2.4.2

The primary securing method is to be designed and manufactured such that the designed compression pressure is achieved by one person without the need of any tools.

2.4.3

For a primary securing method using butterfly nuts, the forks (clamps) are to be of robust design. They are to be designed to minimise the risk of butterfly nuts being dislodged while in use; by means of curving the forks upward, a raised surface on the free end, or a similar method. The plate thickness of unstiffened steel forks is to be not less than 16 mm. An example arrangement is shown in Figure 1.

2.4.4

For small hatch covers located on the exposed deck forward of the foremost cargo hatch, the hinges are to be fitted such that the predominant direction of green seas will cause the cover to close, which means that the hinges are normally to be located on the fore edge.

2.4.5

On small hatches located between the main hatches, for example between No. 1 and No. 2, the hinges are to be placed on the fore edge or outboard edge, whichever is practicable for protection from green water in beam sea and bow quartering conditions.

2.5 Secondary securing devices

2.5.1

Small hatches on the fore deck are to be fitted with an independent secondary securing device, e.g. by means of a sliding bolt, a hasp or a backing bar of slack fit, which is capable of keeping the hatch cover in place, even in the event that the primary securing device became loosened or dislodged. It is to be fitted on the side opposite to the hatch cover hinges.

Figure 1 : Example or primary securing device

Figure 2 : Arrangement of stiffeners