«STRENGTH, CONSTRUCTION AND WATERTIGHT SUBDIVISION 2.1 Definitions (Regulation 2) The following notes are for the guidance of surveyors in the ...»
2.9.1 The bulkhead deck is only required to be weathertight when it is not protected by a higher deck which is weathertight. However, in ships where the bulkhead deck is so protected, the portion of deck which forms the step between the fore peak bulkhead and its extension, when they are not in line, is still required to be weathertight in accordance with Regulation 11(1). The portion of deck which forms the step between a main subdivision bulkhead and a partial bulkhead or web, fitted to limit the spread of water along the deck, is required to be watertight in accordance with Regulation 13.
2.9.2 In Ro-Ro ships, although Regulation 12 and the above indicates that the deck may not be required to be weathertight, in order to meet the intention provided for in Regulation 32 (see also paragraph 4.2 of Part 4 to these Instructions), the deck must be at least weathertight.
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2.10 Partial Subdivision Above the Bulkhead Deck (Regulation 13) 2.10.1 If the margin line is submerged during the flooding of one or more compartments within the extent of damage outlined in Schedule 3 to Merchant Shipping Notice MSN 1698 (M), means shall be provided to limit the spread of water along the bulkhead deck to a minimum, and help to maintain positive stability through all stages of flooding.
2.10.2 If partial watertight bulkheads or webs are fitted to provide such means, they should be fitted immediately above the main subdivision bulkheads of the damaged compartment or compartments, or as close to them as possible, but not in such a position that they could be involved in the damage. Such partial bulkheads or webs should extend inboard from the ship's side, to at least the point of intersection between a line drawn parallel to, and 76 mm above, the heeled waterline and the bulkhead deck. This heeled waterline is the one which extends furthest inboard, at the longitudinal position of the partial bulkhead or web during the flooding of the compartment or compartments (see figure 2.10.2).
The plating and stiffeners of partial bulkheads or webs are to be constructed in accordance with Section 1 of Schedule 4 to Merchant Shipping Notice MSN 1698 (M), as if they formed part of the bulkhead immediately below the bulkhead deck.
2.10.3 In ships where fire resisting bulkheads forming the boundaries of main vertical zones are fitted on the bulkhead deck, such bulkheads, together with any additional bulkheads or webs which are considered necessary, may be accepted as complying with Regulation 13 providing they are suitably positioned, and any openings in them are above the line defined in the preceding paragraph.
2.10.4 In ships which, due to their particular service, are not fitted with bulkheads on the bulkhead deck, alternative means for limiting the spread of water along the bulkhead deck may be considered.
2.10.5 In ships where it is not intended to fit any means to limit the spread of water along the bulkhead deck, the damage stability calculations must show that the margin line is not submerged at any stage of flooding (see paragraph 5.6 of Part 5 of these Instructions).
2.10.6 In order to show that progressive flooding cannot take place when the margin line is submerged, a trace of the line to which the water extends furthest inboard during any stage of flooding should be shown on a plan of the bulkhead deck which indicates the partial subdivision arrangements, and the position of openings in the deck and bulkheads. If air and overflow pipes terminate on the bulkhead deck, the trace should also be shown on a profile to show that progressive flooding cannot take place through the pipes.
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2.11 Openings in Watertight Bulkheads (Regulation 14) 2.11.1 Position of watertight doors 22.214.171.124 It has always been accepted that some access openings, closed by means of watertight doors, will be required in some watertight bulkheads for essential purposes, for example, to inspect vital items of machinery, provide emergency or alternative means of escape. Acceptance of the location of any watertight door will be dependent upon the Certifying Authority being satisfied that its presence is essential for the proper working of the ship.
126.96.36.199 Every effort should be made to reduce, as far as practicable, the number of watertight doors fitted in any passenger ship. In any new design reducing the number of openings in watertight bulkheads might be achieved in a number of ways. For example, in the accommodation spaces, efforts should be made to arrange access and escape routes in a manner which would minimise the need for people to pass through watertight bulkheads below the level of the bulkhead deck. In the case of service spaces and other working compartments normal access should where possible be available without the need for continual passage through main bulkheads.
188.8.131.52 The possible effects of progressive flooding through an unclosed opening should always be taken into account when deciding upon the position and size of any watertight door. An unclosed door, lying wholly below the level of the waterline, obviously presents a great potential hazard.
To lessen such dangers, watertight doors should be kept as small as possible and be positioned, whenever practicable, close to the centreline with their sills as high as is possible and consistent with safe access and preferably above the level of the waterline.
184.108.40.206 The effectiveness of subdivision arrangements is dependant on any watertight door being closed when breaching occurs, or almost immediately afterwards. It is also essential to limit the number of access openings placed in the divisional bulkheads and also to exercise the strictest control over the operation of the watertight doors provided to close such openings.
220.127.116.11 Watertight doors should be fitted inboard of the B/5 line and with their sills as high as possible above the keel. A door positioned outboard of the B/5 may be permitted if the surveyor, and Headquarters, is satisfied that it is necessary for the proper working of the ship and cannot be located elsewhere.
18.104.22.168 Where watertight doors are permitted to be fitted in bulkheads dividing two between deck cargo spaces they must be located inboard of the B/5 line.
2.11.2 Regarding the requirements of Regulation 14(3) and paragraph 29 of Section 4 of Schedule 4 to Merchant Shipping Notice MSN 1698 (M) that a watertight door must be fitted at one end of a tunnel, surveyors should note that MSIS003/PT 2/REV 1.01/PAGE 18 an exemption from this requirement can be considered for short tunnels situated near the centre line of the ship, if the safety of the ship in the event of damage is not impaired. In other cases, where the tunnel is used as a passage at sea, access shall also be obtained by means of a trunkway extending watertight to above the margin line.
2.11.3 Under the provision of Regulations 14(5) watertight bulkheads outside the spaces containing machinery may not be pierced by openings which are capable of being closed only by portable bolted plates. Such openings may, however, be permitted for special purposes in watertight bulkheads within such spaces.
2.11.4 Valves in piping systems
22.214.171.124 Valves which are fitted in piping systems in order to maintain the integrity of the watertight bulkheads in the event of damage, should normally be screw-down valves capable of being controlled manually at the valve, and in the case of ships constructed on or after 1 September 1984, also from a position above the bulkhead deck by means of extended spindles. The spindles and controls to such valves should be fitted inboard of the B/5 line, but in ships such as vehicle ferries, with casings on the bulkhead deck outboard of the B/5 line, the Certifying Authority may permit the spindles and controls to be taken to casings outboard of the B/5 line providing they are positioned on the side of the bulkhead which provides the greater protection, and kept as close to the bulkhead as possible. The Certifying Authority may consider any alternative means of controlling the valves, and if it is from a central control, it must be such that damage to any valve or operating equipment within the extent of damage specified in paragraph 1(3) of Schedule 3 to Merchant Shipping Notice MSN 1698 (M) does not render the system inoperable in the remaining intact portion of the ship. The system should also be such that the valves will automatically close if the means of operating them fails.
126.96.36.199 Lead or other heat sensitive materials may be used in systems which penetrate watertight subdivision bulkheads or other watertight divisions provided that measures are taken to prevent the possibility of deterioration due to fire.
188.8.131.52 The use of plastics for piping systems which pierce subdivision bulkheads, or for valves in such systems will not be permitted, unless they comply with IMO Res. A753(18) - “Guidelines for the application of plastic pipes in ships”, with respect to heat sensitivity.
184.108.40.206 When it is intended to use any other material, which the surveyor may consider to be heat sensitive, for piping and/or parts of valves which maintain the integrity of the watertight bulkheads, details should be submitted to Headquarters for consideration.
2.12.1 General requirements The general requirements for openings in the shell plating below the bulkhead deck, and their means of closing, are set out in Schedule 10 to Merchant Shipping Notice MSN 1698 (M). The requirements of paragraph 1(2) of Schedule 10 are illustrated by figure 2.12.1.
2.12.2 Side scuttles 220.127.116.11 The arrangements of side scuttles should be re-examined for compliance when an increase in draught is proposed. Any side scuttle found not to comply must be blanked off.
18.104.22.168 Where it is proposed to fit heavy duty side scuttles bolted to the shell, particular attention should be made where the connection is not bolted through the shell plating in ships of Class I.
22.214.171.124 For the side scuttles for ships built before 1st September 1984, referred to in paragraph 1(1) of Schedule 10 to Merchant Shipping Notice MSN 1698 (M), the Certifying Authority may indicate the mean draught at which the sills of these side scuttles will not be below the line at which it will be permissible, on the responsibility of the master of the ship, to depart from port without previously closing and locking them. In the application of this sub-paragraph, the appropriate allowance for fresh water may be made when applicable. The surveyor should, therefore, report to the Certifying Authority MSIS003/PT 2/REV 1.01/PAGE 20 in appropriate cases such particulars as will enable the limiting mean draught to be determined. The limiting draught is that at which the side scuttles will have their sills above a line drawn parallel to the bulkhead deck at side and having its lowest point 1.4 metres plus 25% of the breadth of the ship above the waterline corresponding to the limiting mean draught. For this purpose, the distance of the sill below the bulkhead deck at side should be reported for the opening type side scuttle which has its sill the greatest distance below the bulkhead deck at side, this dimension being measured vertically at the side scuttle.
The limiting mean draught resulting from the information supplied should be included in the stability information provided to the master.
126.96.36.199 The general requirements for side scuttles is contained in paragraph
1.3 of these Instructions.
2.12.3 Inlets and discharges 188.8.131.52 The arrangement of scuppers and discharges is, in addition to the following paragraphs, to comply with the requirements of the International Convention on Load Lines.
184.108.40.206 Lead or other heat sensitive materials shall not be used in any other place where the deterioration of such pipes in the event of a fire would give rise to the danger of flooding.
220.127.116.11 Discharge pipes, fitted in accordance with the provisions of the Regulations, should have a sufficient bend to provide for expansion of the pipe and also any movement due to the working of the ship.
18.104.22.168 All discharge pipes led through the shell below the bulkhead deck and the valves relating thereto shall be protected from damage.
22.214.171.124 The arrangements of scuppers and discharges should be reexamined when an increase in draught is proposed, and where such an increase warrants a more positive means of preventing water from passing inboard, such means must be fitted to the scuppers and discharges.