Section 4 Bulkhead arrangements

4.1.1 Watertight bulkheads for NS2 and NS3 ships are, in general, to extend to the uppermost continuous deck, and their construction is to be in accordance with Vol 1, Pt 6, Ch 3, 9 Bulkheads and deep tanks. In the larger multidecked NS1 ships (e.g. Aircraft Carriers) the watertight bulkheads are generally to extend to the lowest continuous vertical limit of weathertightness determined by Vol 1, Pt 3, Ch 2, 1.3 Watertight and weathertight integrity

4.1.2 Where permitted by the stability and subdivision standard, certain openings below the deck described in Vol 1, Pt 3, Ch 2, 4.1 General 4.1.1 may be allowed, see Vol 1, Pt 1, Ch 2, 1.1 Framework of Classification 1.1.9. In all cases these openings must be kept to a minimum and provided with means of closing to watertight standards.

4.1.3 The number of openings in watertight bulkheads is to be reduced to the minimum compatible with the design and proper working of the ship. Where openings are permitted in bulkheads they are to be provided with suitable closing devices in accordance with Vol 1, Pt 3, Ch 4, 4 Watertight doors and hatches in watertight subdivision boundaries

4.1.4 Bulkheads forming the boundaries to citadels and zones as defined in Vol 1, Pt 4, Ch 1, 7 Design guidance for nuclear, biological and chemical defence other than watertight bulkheads, are usually specified to be gastight. See also Vol 1, Pt 3, Ch 2, 4.7 Gastight bulkheads. Where specified, LR can assess the gastight integrity of defined gastight boundaries, see Vol 1, Pt 6, Ch 6, 7.6 Gastight testing.

4.1.5 Pipe or cable runs through watertight bulkheads are to be kept to a minimum and are to be fitted with suitable watertight glands of a type, approved and pressure tested for the maximum head of water indicated by any required damage stability calculations.

4.1.6 The specified subdivision and stability standard(s) may require all bulkhead penetrations to be of to a nominated standard.

4.1.7 Heat-sensitive materials are not to be used in pipe or cable runs which penetrate watertight bulkheads, where deterioration of such systems in the event of fire would impair the watertight integrity of the deck.

4.1.8 Partial or main bulkheads are to be located beneath the ends of superstructures and deckhouses and masts and heavy items of equipment such as weapon systems to support and transmit the static and dynamic forces into the hull structure. They are to be of sufficient strength and rigidity to carry the concentrated loads imposed on them and maintain alignment where necessary.

4.2.1 In general, 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 specified subdivision and stability standard(s).

4.2.2 Main transverse watertight bulkheads are to be spaced at reasonably uniform intervals. Where non-uniform spacing is unavoidable and the length of a compartment is unusually large, the transverse strength of the ship is to be maintained by fitting of web frames, increased framing, etc. Details of the proposed arrangements are to be submitted.

4.2.3 All ships are to have a collision bulkhead, an after peak bulkhead and a watertight bulkhead at each end of all main and auxiliary machinery spaces. Additional watertight bulkheads are to be fitted so that the total number of bulkheads is at least in accordance with Table 2.4.1 Minimum number of bulkheads.

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

4.2.5 A main transverse bulkhead is to be located at the position where the ship sues during docking.

4.3.1 The collision bulkhead is to be positioned as detailed in Vol 1, Pt 3, Ch 2, 4.4 Aft peak bulkhead 4.4.1. However, consideration will be given to proposals for the collision bulkhead, including any extensions to be positioned further aft provided that the application is accompanied by calculations showing that flooding of the spaces forward of the collision bulkhead, including below any steps, will not result in any part of the uppermost continuous deck becoming submerged, or any unacceptable loss of stability. The length L_R is as defined in Vol 1, Pt 3, Ch 1, 5.2 Principal particulars 5.2.2.

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

4.3.3 No accesses are to be fitted in the collision bulkhead below the vertical limit of watertight integrity. In designs where it would be impracticable to arrange access to the fore peak spaces other than through the collision bulkhead, access may be permitted provided the openings are as small as practicable and positioned as far above the design draught as possible. Access is to be by a watertight manhole with a bolted cover (e.g. ISO 5894 Ships and marine technology – Manholes with bolted covers).

4.3.4 Penetrations for piping, cabling, ventilation or other services are only to be fitted in the collision bulkhead below the vertical limit of watertight integrity if permitted by the sub-division and stability standard(s). Where permitted, pipe penetrations are to be in accordance with Vol 2, Pt 7, Ch 2, 3 Drainage of compartments, other than machinery spaces.

4.3.5 The number of openings in the extension of the collision bulkhead above the vertical limit of watertight integrity 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.

4.4.1 NS1 and, where practicable, NS2 ships, are to have an aft peak bulkhead generally enclosing the sterntube and rudder trunk in a watertight compartment. In twin screw ships where the bossing ends forward of the aft peak bulkhead, the sterntubes are to be enclosed in suitable watertight spaces inside or aft of the shaft tunnels. 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 ship will remain fully operational. The arrangement in NS3 ships, and in NS2 ships where it is impracticable to meet the aforementioned conditions, will be specially considered based on the integrity of the gland sealing arrangements and damage stability requirements.

4.5.1 The collision bulkhead is normally to extend to the uppermost continuous deck or, in the case of a ship with a long forward superstructure or forecastle, to the first superstructure deck or weather deck above the uppermost continuous deck. Where the collision bulkhead extends above the vertical limit of watertight integrity, the extension need only be to weathertight standards; however, where Vol 1, Pt 5, Ch 3, 5.9 Design pressures for collision bulkheads 5.9.5 applies, the full height shall also be designed to the pressures for the shell envelope.

4.5.2 The aft peak bulkhead may terminate at the first deck above the design draught, provided that this deck is made watertight to the stern or to a watertight transom floor.

4.5.3 The remaining watertight bulkheads are to extend as required by Vol 1, Pt 3, Ch 2, 4.1 General 4.1.1. In ships of unusual design, the height of the bulkheads will be specially considered.

4.5.4 In ships fitted with enclosed mooring decks above the uppermost continuous deck, and where the arrangements prevent the collision bulkhead from extending to the first superstructure deck, the enclosed mooring deck and fittings are to be weathertight up to and including the next bulkhead aft, unless they are otherwise required to be watertight by the sub-division and stability standards.

4.6.1 Watertight recesses in bulkheads are to be avoided whenever possible.

4.6.2 Where watertight bulkhead stiffeners are cut in way of watertight doors in the lower part of a bulkhead, the opening is to be suitably framed and reinforced. Where stiffeners are not cut but the spacing between the stiffeners is increased on account of watertight doors, the stiffeners at the sides of the doorways are to be increased in depth and strength so that the efficiency is at least equal to that of the unpierced bulkhead, without taking the stiffness of the door frame into consideration.

4.6.3 In collision bulkheads, any recesses or steps in the bulkhead are to fall within the limits of bulkhead positions given in Vol 1, Pt 3, Ch 2, 4.3 Collision bulkheads 4.3.1. If a step occurs above the vertical limit of watertight integrity, the deck need only be weathertight in way of the step, unless it forms part of a damage control deck, in which case it shall be watertight. Additionally, if the step forms the crown of a tank, the requirements for deep tank structures are to be complied with.

4.6.4 In ships fitted with bow doors, in which a sloping loading ramp forms part of the collision bulkhead above the virtual limit of watertight integrity, that part of the ramp which is more than 2,30 m above the virtual limit of watertight integrity may extend forward of the minimum limit specified in Table 2.4.2 Collision bulkhead position distance of collision bulkhead aft of fore end of L_R, in metres Such a ramp is to be weathertight over its complete length.

4.7.1 Where an assessment of gastight integrity is required the scantlings of gastight bulkheads are to be in accordance with Vol 1, Pt 6 Hull Construction in Steel.

4.7.2 Where bulkheads are required to be gastight 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 For bulkheads in way of partially filled compartments or tanks, sloshing forces may be required to be taken into account. Where such forces are likely to be significant, the scantlings will be required to be verified by additional calculations.

4.8.2 The scantlings of deep tank bulkheads are to be in accordance with Vol 1, Pt 6 Hull Construction in Steel.

4.8.3 Air and sounding pipes are to comply with the requirements of Vol 1, Pt 3, Ch 4, 7 Air 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.

4.9.6 Where fitted, cofferdams are to be suitably ventilated, provided with a suitable drainage arrangement, see Vol 2, Pt 7, Ch 2, 3.2 Tanks and cofferdams, 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.

4.10.1 Sterntubes are to be enclosed in watertight spaces of moderate volume. In addition, arrangements are to be made to minimise the danger of water penetrating into the ship in case of damage to the sterntube. Normally 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 vertical limit of watertight integrity, see Vol 1, Pt 3, Ch 2, 1.3 Watertight and weathertight integrity, will not be submerged.

4.11.1 The arrangement of the hull is to be such that all under deck compartments are as accessible as practicable and provided with a satisfactory means of escape in accordance with a specified standard(s). Access and escape hatches to the machinery and tanks are not to be obstructed by deck coverings or furniture.

4.12.1 For ships having fuel oil with a flash point below 60°C the arrangement for the storage, distribution and utilisation of the fuel oil is to be such that the safety of the ship and persons on board is preserved, having regard to the fire and explosion hazards.See Vol 2, Pt 7, Ch 3, 2 Fuel oil - General requirements