Section 4 Bulkhead requirements

4.1.1 All ships are to have a collision bulkhead, an after peak bulkhead, generally enclosing the sterntubes in a watertight compartment, and a watertight bulkhead at each end of the machinery space. Additional watertight bulkheads are to be fitted so that the total number of bulkheads is at least in accordance with Table 3.4.1 Total number of bulkheads.

4.1.2 The bulkheads in the holds should be spaced at reasonably uniform intervals. Where non-uniform spacing is unavoidable and the length of a hold is unusually great, the transverse strength of the ship is to be maintained by fitting web frames, increased framing, etc. and details are to be submitted.

4.1.3 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.

4.1.4 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 in the country in which the ship is registered.

4.2.1 A collision bulkhead shall be fitted which shall be watertight up to the bulkhead deck. This bulkhead shall be located at a distance from the forward side of the stem, on the waterline on which L _L is measured, of not less than 0,05L _L or 10 m, whichever is the less, and, except as may be permitted by the Administration, not more than 0,08L _L or 0,05L _L + 3 m, whichever is the greater.

4.2.2 Where any part of the ship below the waterline extends forward of the forward side of the stem, on the waterline on which L _L is measured, e.g. a bulbous bow, the distances stipulated in Pt 3, Ch 3, 4.2 Collision bulkhead 4.2.1 are to be measured from a point either:

1. at the mid-length of such extension;

2. at a distance 0,015L _L forward of the forward side of the stem, on the waterline on which L _L is measured; or

3. at a distance 3 m forward of the forward side of the stem, on the waterline on which L _L is measured, whichever is the least.

4.2.3 No doors, manholes, access openings, ventilation ducts or any other openings shall be fitted in the collision bulkhead below the bulkhead deck.

4.3.1 All ships are to have an after peak bulkhead generally enclosing the sterntube and rudder trunk in a watertight compartment. In twin screw ships where the bossing ends forward of the after peak bulkhead, the sterntubes are to be enclosed in suitable watertight spaces inside or aft of the shaft tunnels. The sterntubes are to be enclosed in watertight spaces of moderate volume. In passenger ships, the stern gland is to be situated in a watertight shaft tunnel or other watertight space separate from the sterntube compartment and of such volume that, if flooded by leakage through the stern gland, the bulkhead deck will not be submerged.

4.4.1 The collision bulkhead is normally to extend to the uppermost continuous deck or, in the case of ships with combined bridge and forecastle or a long superstructure which includes a forecastle, to the superstructure deck. However, if a ship 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.

4.4.2 The after 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 ships, the after 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 ship as regards watertight subdivision is not thereby diminished.

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

4.5.1 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.

4.5.2 In collision bulkheads, any recesses or steps in the bulkhead are to fall within the limits of bulkhead positions given in Pt 3, Ch 3, 4.2 Collision bulkhead 4.2.1. Where the bulkhead is extended above the freeboard deck or bulkhead deck, 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, see Pt 4, Ch 1, 4 Deck structure.

4.5.3 Where bow doors are fitted and a sloping loading ramp forms part of the extension of the collision bulkhead above the bulkhead deck the ramp shall be weathertight over its complete length. In cargo ships the part of the ramp which is more than 2,3 m above the bulkhead deck may extend forward of the limit specified in Pt 3, Ch 3, 4.2 Collision bulkhead 4.2.1 or Pt 3, Ch 3, 4.2 Collision bulkhead 4.2.2. Ramps not meeting the above requirements shall be disregarded as an extension of the collision bulkhead.

4.5.4 The number of openings in the extension of the collision bulkhead above the freeboard deck shall be restricted to the minimum compatible with the design and normal operation of the ship. All such openings shall be capable of being closed weathertight.

4.6.1 When timber load lines are to be assigned, double bottom tanks within the midship half-length are to have adequate longitudinal subdivision.

4.7.2 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.

4.7.3 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.

4.7.5 Where a corner to corner situation occurs, tanks are not considered to be adjacent.

4.7.6 Where fitted, cofferdams are to be suitably ventilated, provided with a suitable drainage arrangement, see Pt 5, Ch 13, 3.5 Tanks and cofferdams, and be of sufficient size to allow proper inspection, maintenance and safe evacuation.

4.7.7 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, see also SOLAS - International Convention for the Safety of Life at Sea Chapter II-2 - Construction - Fire protection, fire detection and fire extinction Part B - Prevention of fire and explosion1 4.2.2.3.2.

4.7.8 For vessels which do not comply with the accidental fuel oil outflow performance standard given in MARPOL Annex 1, Regulation 12A-11, fuel oil tanks are to be bounded by double bottom and double side tanks or void spaces such that the distance between the fuel oil tank boundary and the shell plating is not less than that given in Table 3.4.2 Fuel oil tank boundary requirements and Figure 3.4.1 Fuel oil tank boundary lines. For double hull oil tankers where the requirements of Pt 4, Ch 9, 1.2 Application and ship arrangement 1.2.17 conflict with this requirement Pt 4, Ch 9, 1.2 Application and ship arrangement 1.2.17 is to take precedent. Alternatively the accidental oil outflow performance standard specified in MARPOL Annex 1 Regulation 12A may be complied with.

Table 3.4.2 Fuel oil tank boundary requirements

Fuel oil tank capacity (C),	Minimum double side width (d s)	Minimum double bottom depth (d b)
m3	metres	metres
C ≥ 5000
	or	or
	d s = 2,0	d b = 2,0
	whichever is the lesser, but not less than 1,0	whichever is the lesser, but not less than 0,76
600 ≤ C < 5000
	or	or
	d s = 1,0	d b = 2,0
	whichever is the greater, see Note	whichever is the lesser, but not less than 0,76
C < 600	d s = 0	d b = 0
Symbols
C = the ship’s total volume of fuel oil, including that of small fuel oil tanks, in m3, at 98 per cent tank filling db = the distance, in metres, between the bottom of the fuel oil tank and the moulded line of the bottom shell plating. In the turn of bilge area and at locations without a clearly defined turn of bilge, the fuel oil tank boundary line shall run parallel to the line of the midship flat bottom as shown in Figure 3.4.2 Definition of db d s = the distance, in metres, between the side of the fuel oil tank and the moulded line of the side shell plating, see Figure 3.4.1 Fuel oil tank boundary lines
Note 1. However, for individual tanks with an fuel oil capacity of less than 500 m3, the minimum distance is 0,76 m. Note 2. Fuel oil tanks with a maximum individual capacity not greater than 30 m3 need not comply with the requirements of this Table, provided the aggregate capacity of such excluded tanks is not greater than 600 m3. Note 3. Suction wells in fuel oil tanks may protrude into the double bottom below the boundary line defined by the distance d b, provided that such wells are as small as practicable and the distance between the well bottom and the bottom shell plating is not less than 0,5d b.

Figure 3.4.1 Fuel oil tank boundary lines

Figure 3.4.2 Definition of d_b

4.7.9 No individual fuel oil tank is to have a capacity greater than 2,500 m³.

4.8.1 Where a machinery space is situated with a compartment or compartments between it and the after peak bulkhead, the shafting is to be enclosed in a watertight tunnel large enough to permit proper examination and repair of shafting. A sliding watertight door, capable of being operated locally from both sides, is to be provided at the forward end of the tunnel. Consideration may, however, be given to the omission of the watertight door, subject to satisfactory compliance with any relevant statutory requirements. Where two or more shafts are fitted, the tunnels shall be connected by an interconnecting passage. There shall be only one door between the machinery space and the tunnel spaces where two shafts are fitted and only two doors where there are more than two shafts.

4.8.2 Pipe tunnels are to have dimensions adequate for reasonable access.

4.8.3 Where fore and aft underdeck passageways are arranged at the ship's side, the after access thereto is to be by a watertight trunk led to the upper deck. Alternative arrangements to prevent the engine room being flooded, in the event of a collision or if the passageway doors are left open, will be considered.

4.9.1 For the requirements for means of escape, see SOLAS 1974 as amended Regulation 13 - Means of escape.

4.10.1 For subdivision requirements within the cargo tank region for oil tankers, see Pt 4, Ch 9, 1 General.