Section 2 Strength and securing of small hatches on the exposed foredeck

2.1 Application

2.1.1 This section applies to small hatches on the exposed foredeck giving access to spaces forward of the collision bulkhead, and to spaces which extend over this line aft. Small hatches in this context are hatches designed for access to spaces below the deck and are capable of being closed weather-tight or watertight, as applicable. Their opening is normally 2,5 m² or less.

2.1.2 Emergency escape hatches are excluded from complying with Ch 1, 2.3 Primary securing devices 2.3.1, Ch 1, 2.4 Requirements for primary securing 2.4.3 and Ch 1, 2.5 Secondary securing device.

2.2 Strength

2.2.1 For small rectangular steel hatch covers, the plate thickness, stiffener arrangement and scantlings are to be in accordance with Table 1.2.1 Scantlings for small steel hatch covers on exposed deck, and Figure 1.2.1 Arrangement of stiffeners. Stiffeners, where fitted, are to be aligned with the metal-to-metal contact points, required in Ch 1, 2.4 Requirements for primary securing 2.4.1, see Figure 1.2.1 Arrangement of stiffeners. Primary stiffeners are to be continuous. All stiffeners are to be welded to the inner edge stiffener, see Figure 1.2.2 Example of primary securing method.

Table 1.2.1 Scantlings for small steel hatch covers on exposed deck

Nominal size (mm x mm)	Cover plate thickness (mm)	Primary stiffeners	Secondary stiffeners
Nominal size (mm x mm)	Cover plate thickness (mm)	Flat bar (mm x mm); number
630 x 630	8	-	-
630 x 830	8	100 x 8;1	-
830 x 630	8	100 x 8;1	-
830 x 830	8	100 x 10;1	-
1030 x 1030	8	120 x 12;1	80 x 8;2
1330 x 1330	8	150 x 12;2	100 x 10;2

Figure 1.2.1 Arrangement of stiffeners

Figure 1.2.2 Example of primary securing method

2.2.2 The upper edge of the hatchway coamings is to be suitably reinforced by a horizontal section, normally not more than 170 to 190 mm from the upper edge of the coamings.

2.2.3 For small hatch covers of circular or similar shape, the cover plate thickness and reinforcement are to be of equivalent strengfth to that of the small rectangular steel hatch covers described in Ch 1, 2.2 Strength 2.2.1.

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

2.3 Primary securing devices

2.3.1 Hatches are to be fitted with primary securing devices such that their hatch covers can be secured in place and weather-tight by means of a mechanism employing any one of the following methods:

Butterfly nuts tightening onto forks (clamps);
Quick acting cleats; or
Central locking device.

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

2.4 Requirements for 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 1.2.1 Arrangement of stiffeners, 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 can be 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. This can be achieved by curving the forks upward, raising the surface on the free end, or by a similar method. The plate thickness of unstiffened steel forks is not to be less than 16 mm. An example arrangement is shown in Figure 1.2.2 Example of primary securing method.

2.4.4 For small hatch covers located on the exposed deck forward of the fore-most cargo hatch, the hinges are to be fitted such that the predominant direction of green sea will cause the cover to close. The hinges are normally to be located on the forward edge.

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

2.5 Secondary securing device

2.5.1 Hatches 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 becomes loosened or dislodged. It is to be fitted on the side opposite to the hatch cover hinges.