Section 1 General

1.1.1 This Chapter applies to all ship types detailed in Pt 4 Ship Structures (Ship Types), unless otherwise stated, with the exception of Sections 1 to 5 which are not applicable to Bulk Carriers with a CSR notation and Section Pt 3, Ch 11, 6.1 Small hatchways on exposed decks which is not applicable to Bulk Carriers and Oil Tankers with a CSR notation, see Pt 1, Ch 2, 2.3 Class notations (hull). Additional provisions regarding access arrangements for oil tankers and chemical carriers are contained in Pt 4, Ch 9 Double Hull Oil Tankers, Pt 4, Ch 10 Single Hull Oil Tankers and the Rules and Regulations for the Construction and Classification of Ships for the Carriage of Liquid Chemicals in Bulk, July 2022 (hereinafter referred to as the Rules for Ships for Liquid Chemicals), respectively.

1.1.2 Requirements are given for steel and wooden hatch covers, securing arrangements, tarpaulins, coamings and side shell doors for main openings, also closing arrangements for other miscellaneous openings.

1.1.3 Where relevant, the contents of this Chapter conform with the requirements of the Load Lines, 1966/1988 - International Convention on Load Lines, 1966, as Amended by the Protocol of 1988 . Attention should, however, be given to any additional Statutory Requirements of the National Authority of the country in which the ship is to be registered and to the relevant regulations of the SOLAS - International Convention for the Safety of Life at Sea and applicable amendments.

1.1.4 For the purpose of this Chapter the basic types of ships are those defined in the Load Lines, 1966/1988 - International Convention on Load Lines, 1966, as Amended by the Protocol of 1988 namely:

1.1.5 The type of hatch covers on the weather decks of the basic ship types defined in Pt 3, Ch 11, 1.1 Application 1.1.4 are detailed below and may be used in the types of ships as indicated in Table 11.1.1 Covers associated with ship types:

1. Steel plated cargo hatch covers stiffened by webs or stiffeners and secured by clamping devices. Weathertightness to be achieved by means of gaskets. Hatch covers used for holds containing liquid cargoes are included in this category.

2. Steel plated cargo hatch pontoon covers having interior webs and stiffeners extending for the full width of the hatchway. A pontoon cover is defined as a portable cover, secured weathertight by tarpaulins and battening devices.

3. Hatch covers of wood or steel used in conjunction with portable beams. Weathertightness to be obtained by tarpaulins.

4. Access hatch covers for cargo oil tanks and adjacent spaces. The hatch covers are to be of steel and gasketed.

5. Access hatch covers other than (d). For Type `A', Type `B-100' and Type `B-60' ships, the covers are to be of steel, and weathertightness is to be achieved by means of gaskets.

1.1.6 The positions of hatches on weather decks are defined in Pt 3, Ch 1, 6.6 Position 1 and Position 2.

1.1.7 'Tween deck hatch covers may be any of the types defined in Pt 3, Ch 11, 1.1 Application 1.1.5, but need not be weathertight unless fitted to deep tanks or water ballast holds or compartments, in which case the covers are to be of type (a) and oiltight or watertight as appropriate.

1.1.8 The scantlings specified in the following Sections are applicable to covers of mild steel or higher tensile steel. Where other materials are used, equivalent scantlings are to be provided. The scantlings apply basically to rectangular covers, with the stiffening members arranged primarily in one direction and carrying a uniformly distributed load. The covers are assumed to be simply supported. Where covers are stiffened by a grillage formation, and also where point loads are applied to any type of cover, the scantlings are to be determined from direct calculations.

1.1.9 In the case of flush hatch covers or of covers on coamings of lesser height than required by Pt 3, Ch 11, 5.1 General 5.1.1, their scantlings, the securing and sealing arrangements and the drainage of gutterways will be specially considered.

1.1.10 The scantlings of hatch covers need to be increased only if the loading exceeds that given in Pt 3, Ch 11, 2.3 Load model. The scantlings of the surrounding deck structure are to be sufficient to support this loading. Heavier loading may be permitted only if the scantlings of the cover are capable of withstanding this increased loading, satisfying the stress and deflection criteria given in this Chapter. The deck structure is also to be capable of withstanding this increased loading.

1.1.11 Where timber cargo is to be carried on the hatch covers the requirements of Pt 3, Ch 9, 2.11 Scantlings of hatch covers are to be satisfied in addition to the requirements of this Chapter.

1.1.12 Where hatchways are trunked through one or more 'tween decks, and hatchway beams and covers are dispensed with at the intermediate decks, the hatchway beams, coamings and covers immediately below the trunk are to be adequately strengthened. Plans are to be submitted for approval.

1.1.13 The net plate thickness, t _net, is the calculated minimum thickness of the plating and stiffeners. The required thickness is the net thickness plus a corrosion addition, t _c, given in Table 11.1.2 Corrosion addition t _c .