Section 4 Bulkhead arrangements

4.1.1 The criteria on bulkhead arrangements in this Section apply to seagoing craft. Bulkhead arrangements for non-seagoing craft will be specially considered based on the structural requirements and the requirements of the authority where the craft is registered. In the absence of National Authority requirements the relevant requirements of the Rules and Regulations for the Classification of Inland Waterways Ships, July 2022 are to be complied with.

4.1.2 Watertight bulkheads are, in general, to extend to the uppermost continuous watertight deck, hereinafter referred to as the bulkhead deck, and their construction is to be in accordance with Pt 6 Hull Construction in Steel, Pt 7 Hull Construction in Aluminium and Pt 8 Hull Construction in Composite as appropriate.

4.1.3 Where openings are permitted in bulkheads they are to be provided with suitable closing devices in accordance with Pt 3, Ch 4, 2 Bulkhead openings.

4.2.1 All craft with a Rule length, L_R, greater than 15 m are to have a collision bulkhead.

4.2.2 In motor craft with a Rule length, L_R, less than or equal to 15 m, the machinery is to be enclosed by gastight bulkheads to protect accommodation spaces from gas and vapour fumes from machinery, exhaust and fuel systems.

4.2.3 Where the aft peak bulkhead does not enclose the hull penetration for the sterntube, see Pt 3, Ch 3, 3.13 Sterntubes 3.13.14.

4.2.4 All craft with a Rule length, L_R, greater than 15 m are to have a watertight bulkhead at each end of the machinery space, where the machinery is amidships or a watertight bulkhead at the forward end of the machinery space, where the machinery is aft.

4.2.5 All craft with a Rule length, L_R, greater than 25 m are to have a watertight bulkhead at each end of the machinery space, with the aft peak bulkhead forming the aft bulkhead of the machinery space, where the machinery is aft.

4.2.6 Additional watertight bulkheads are to be fitted so that the total number of bulkheads is at least in accordance with Table 2.4.1 Total number of bulkheads.

4.2.7 Bulkheads are to be spaced at reasonably uniform intervals. Where non-uniform spacing is unavoidable and the length of a compartment is unusually great, the transverse strength of the craft is to be maintained by fitting of web frames, increased framing, etc. and details are to be submitted.

4.2.8 Proposals to dispense with one or more of these bulkheads will be considered, subject to suitable structural compensation, if they interfere with the requirements of a special trade.

4.2.9 Where applicable, the number and disposition of bulkheads are to be arranged to suit the requirements for subdivision, floodability and damage stability, and are to be in accordance with the requirements of the National Authority.

4.3.1 The collision bulkhead in all craft other than passenger craft, patrol craft and yachts is to be positioned as detailed in Table 2.4.2 Collision bulkhead position (excluding passenger craft, patrol craft and yachts). Consideration will, however, be given to proposals for the collision bulkhead to be positioned slightly further aft on Arrangement (b) craft, but not more than 0,08L _L from the fore end of L _L, provided that the application is accompanied by calculations showing that flooding of the space forward of the collision bulkhead will not result in any part of the freeboard deck becoming submerged, or any unacceptable loss of stability. Special consideration may be given to the extent of the collision bulkhead above the bulkhead deck for multi-hull craft.

Table 2.4.2 Collision bulkhead position (excluding passenger craft, patrol craft and yachts)

Arrangement	Length, L L	Distance of collision bulkhead aft of the fore end of L L, in metres
		Minimum	Maximum
(a)	≤ 150	0,05L L	0,08L L
(b)	≤ 150	0,05L L - f 1	0,08L L -f 1
Symbols and definitions
f 1 = or 0,015L L, whichever is the lesser G = Projection of bulbous bow forward of fore end of L L, in metres L L is as defined in Pt 3, Ch 1, 6.2 Principal particulars Arrangement (a) A craft that has no part of its underwater body extending forward of the fore end of L L. Arrangement (b) A craft with part of its underwater body extended forward of the fore end of L L (e.g. bulbous bow).

4.3.2 The collision bulkhead in passenger craft, patrol craft and yachts is to be in accordance with the following:

1. A craft shall have a forepeak or collision bulkhead, which shall be watertight up to the bulkhead deck. (The bulkhead deck is the uppermost deck up to which the transverse watertight bulkheads are carried, see Pt 3, Ch 2, 4.2 Number and disposition of bulkheads 4.2.9). This bulkhead is to be positioned as detailed in Table 2.4.3 Collision bulkhead for passenger craft, patrol craft and yachts.

2. If the craft has a long forward superstructure, the forepeak or collision bulkhead is to be extended weathertight to the deck next above the bulkhead deck. The extension need not be fitted directly over the bulkhead below, provided it is located within the limits specified in Table 2.4.3 Collision bulkhead for passenger craft, patrol craft and yachts with the exemption permitted by Pt 3, Ch 2, 4.6 Watertight recesses, flats and loading ramps 4.6.3 and the part of the bulkhead deck which forms the step is made effectively weathertight.

Table 2.4.3 Collision bulkhead for passenger craft, patrol craft and yachts

Arrangement	Distance of collision bulkhead aft of fore perpendicular, in metres
	Minimum	Maximum
(a)	0,05L pp	3 + 0,05L pp
(b)	0,05L pp - f	3 + 0,05L pp - f
Symbols and definitions
f = or 0,015L pp, whichever is the lesser G = Projection of bulbous bow forward of fore perpendicular, in metres L pp is as defined in Pt 3, Ch 1, 6.2 Principal particulars . Arrangement (a) A craft that has no part of its underwater body extending forward of the fore perpendicular. Arrangement (b) A craft with part of its underwater body extending forward of the fore perpendicular (e.g. bulbous bow).

4.3.3 Alternative arrangements may be submitted for consideration in the case of sailing and auxiliary craft.

4.3.4 For craft with pronounced rake of stem, the position of the collision bulkhead will be specially considered.

4.3.5 Accesses are not to be fitted in collision bulkheads. In particular designs where it would be impracticable to arrange access to the fore peak other than through the collision bulkhead, access may be permitted subject to special consideration. Where accesses are provided, the openings are to be as small as practicable and positioned as far above the design waterline as possible. The closing appliances are to be watertight, to open into the fore peak compartment and consideration will be given to operation from one side only.

4.4.1 An aft peak bulkhead, where required to be fitted (in each half of a multi-hull craft) is, in general, to enclose the sterntube, water jet unit, etc. in a watertight compartment. Where the aft peak bulkhead does not enclose the hull penetration for the sterntube, waterjet unit, etc. see Pt 3, Ch 3, 3.13 Sterntubes 3.13.14. See also Table 2.4.1 Total number of bulkheads.

4.5.1 The collision bulkhead is to extend to the uppermost continuous deck or, in the case of craft with combined bridge and forecastle or a long superstructure which includes a forecastle, to the superstructure deck if the superstructure is considered effective in stability. However, if a craft is fitted with more than one complete superstructure deck, the collision bulkhead may be terminated at the deck next above the freeboard deck. Where the collision bulkhead extends above the freeboard deck, the extension need only be to weathertight standards.

4.5.2 The aft peak bulkhead may terminate at the first deck above the load waterline, provided that this deck is made watertight to the stern or to a watertight transom floor. In passenger craft the aft peak bulkhead is to extend watertight to the bulkhead deck. However, it may be stepped below the bulkhead deck provided the degree of safety of the craft as regards watertight subdivision is not thereby diminished.

4.5.3 The remaining watertight bulkheads are to extend to the bulkhead deck. In passenger craft of restricted draught and all craft of unusual design, the height of the bulkheads will be specially considered.

4.6.1 Watertight recesses in bulkheads are generally to be so framed and stiffened as to provide strength and stiffness equivalent to the requirements for watertight bulkheads.

4.6.2 In collision bulkheads, any recesses or steps in the bulkhead are to fall within the limits of bulkhead positions given in Pt 3, Ch 2, 4.3 Collision bulkhead 4.3.1 or Pt 3, Ch 2, 4.3 Collision bulkhead 4.3.3 as applicable. Where the bulkhead is extended above the freeboard deck, or bulkhead deck in passenger craft, the extension need only be to weathertight standards. If a step occurs at that deck, the deck need also only be to weathertight standards in way of the step, unless the step forms the crown of a tank, in which case the requirements for deep tank structures are to be complied with.

4.6.3 In craft fitted with bow doors, in which a sloping loading ramp forms part of the collision bulkhead above the freeboard or bulkhead deck, that part of the ramp which is more than 2,30m above the freeboard or bulkhead deck may extend forward of the minimum limit specified in Table 2.4.2 Collision bulkhead position (excluding passenger craft, patrol craft and yachts) or Table 2.4.3 Collision bulkhead for passenger craft, patrol craft and yachts as appropriate. Such a ramp is to be weathertight over its complete length.

4.7.1 Where bulkheads are required to be gastight in accordance with Pt 3, Ch 2, 4.2 Number and disposition of bulkheads 4.2.2, and where it is proposed to pierce such bulkheads for the passage of cables, pipes, vent trunking etc. gastight glands are to be provided to maintain the gastight integrity.

4.8.1 The scantlings of deep tank bulkheads are to be in accordance with Pt 6, Ch 3, 7 Bulkheads and deep tanks, Pt 7, Ch 3, 7 Bulkheads and deep tanks and Pt 8, Ch 3, 7 Bulkheads and deep tanks, for steel, aluminium alloy and composite structures respectively.

4.8.2 Air and sounding pipes are to comply with the requirements of Pt 15, Ch 2, 11 Air, overflow and sounding pipes.

4.9.2 Tanks carrying liquids for the purposes of fire-fighting (e.g. foam concentrate) are to be separated by cofferdams from adjacent tanks containing liquid fuels.

4.9.3 Tanks carrying fresh water for human consumption (potable water) are to be separated by cofferdams from adjacent tanks containing liquid substances harmful to human health. Fresh water for other purposes and water ballast are not considered harmful.

4.9.5 Where a corner to corner situation occurs, tanks are not considered to be adjacent, but any welds near the corner joining the continuous plate are to be full penetration welds.

4.9.6 Where fitted, cofferdams are to be suitably ventilated, provided with a suitable drainage arrangement, and be of sufficient size to allow proper inspection, maintenance and safe evacuation.

4.9.7 If fuel oil tanks are necessarily located within or adjacent to the machinery spaces, their arrangement is to be such as to avoid direct exposure of the bottom from rising heat resulting from a machinery or hazardous space fire. In addition SOLAS Regulation II-2/B4.2.2.3.2, where applicable, shall be adhered to. Alternative standards consistent with SOLAS Regulation II-2/B4.2.2.3.2 can be applied.

4.9.8 Attention is drawn to the Flag Administration requirement's concerning separation and protection of tanks.

4.10.1 The arrangement of the hull is to be such that all underdeck compartments are as accessible as practicable and provided with a satisfactory means of escape. Access and escape hatches to the machinery and tanks are not to be obstructed by deck coverings or fixed furniture. Special consideration may be given to escape arrangements through raised deck areas or fixed furniture where the escape trunk is an integral part of the raised area or the fixed furniture. Access and escape hatches are not to have their operation obstructed.

4.11.1 Special provision is to be made for the carriage of low flash point fuel in accordance with Pt 15, Ch 3, 5 Low flash point fuels.