Section 3 Hatch beams and wood covers

3.1.1 The section modulus and moment of inertia of portable web plate beams stiffened at their upper and lower edges by continuous flat bars are to satisfy the requirements of Pt 3, Ch 11, 2.17 Pontoon covers for pontoon covers. Alternatively, direct calculations may be used, provided the requirements of Pt 3, Ch 11, 2.17 Pontoon covers for pontoon covers are complied with.

3.1.2 The ends of web plates are to be doubled, or inserts fitted for at least 180 mm along length of web.

3.1.3 At beams which carry the ends of wood or steel hatch covers, a vertical 50 mm flat is to be arranged on the upper face plate. The width of bearing surface for hatch covers is to be not less than 65 mm.

3.1.4 Carriers or sockets, or other suitable arrangements, of suitable construction are to provide means for the efficient fitting and securing of portable hatch beams. The width of bearing surface is to be not less than 75 mm.

3.1.5 Sliding hatch beams are to be provided with an efficient device for locking them in their correct fore and aft positions when the hatchway is closed.

3.2.1 Wood covers are to have a finished thickness of not less than 60 mm in association with an unsupported span of not more than 1,5 m. Where the 'tween deck height measured vertically on the centreline of the ship from ‘tween deck to underside of the hatch cover stiffeners on deck above, exceeds 2,6 m, the thickness of the wood covers is to be increased at the rate of 16,5 per cent per metre excess in 'tween deck height.

3.2.2 The ends of all wood hatch covers are to be protected by encircling galvanised steel bands, about 65 mm wide and 33 mm thick, efficiently secured.