«STRENGTH, CONSTRUCTION AND WATERTIGHT SUBDIVISION 2.1 Definitions (Regulation 2) The following notes are for the guidance of surveyors in the ...»
188.8.131.52 If, in the case of any ship of Classes II or II(A) whose factor of subdivision falls to be dealt with under paragraph 9(2)(c) and (d) of Section 3 of Schedule 2 to Merchant Shipping Notice MSN 1698 (M), the Certifying Authority is satisfied that it is impracticable to comply with a unity factor of subdivision in particular compartments, such exemptions in respect of those compartments as appear to be justified may be granted. In which event, having regard to all the circumstances, provided that the aftermost compartment and as many as possible of the forward compartments (between the forepeak and the after end of the machinery space) shall be kept within the floodable length.
2.5.4 Criterion of Service
184.108.40.206 For ships not having a continuous bulkhead deck the volumes used for the purpose of calculating the Criterion of Service Numeral should be taken up to the actual margin lines used in determining floodable length.
Paragraph 2.1.3 of these Instructions defines those passenger spaces, whose volumes may be used to determine the value of P in the Criterion of Service Numeral formulae.
220.127.116.11 The volumes of all permanent fuel tanks which are positioned above the line of the inner bottom and below the bulkhead deck, and not just those which are adjacent to the machinery space, are to be added to the machinery space volume used in the formulae for Criterion of Service Numeral.
2.5.5 Special rules for subdivision 18.104.22.168 A compartment exceeding its permissible length (i) Paragraph 6(1) of Section 2 of Schedule 2 to Merchant Shipping Notice MSN 1698 (M) states the circumstances under which a compartment may exceed the permissible length.
(ii) In exceptional circumstances consideration may be given to nonstructural means of providing buoyancy in compartments which do not achieve the required standard of subdivision, providing such means are fitted inboard of the B/5 line and below the margin line. Such buoyancy should be fitted as high as possible in the compartment, especially if the stability of the ship is marginal when the compartment is assumed damaged.
22.214.171.124 Steps and recesses in bulkheads and equivalent plane bulkheads Paragraphs 6(3)(b), 6(4) and 6(5) of Section 2 of Schedule 2 to Merchant Shipping Notice MSN 1698 (M) which deal with steps and recesses in bulkheads and equivalent plane bulkheads respectively, are illustrated by figures 126.96.36.199 a, b and c.
2.5.6 Allowance for local subdivision 188.8.131.52 Any claim for an allowance for local subdivision under the provisions of paragraph 6(7) of Section 2 of Schedule 2 to Merchant Shipping Notice MSN 1698 (M), in the consideration of flooding curves only should be accompanied by plans showing the proposed local subdivision and the
184.108.40.206 When alternative damage calculations are considered in accordance with paragraph 2.5.1 of these Instructions, local allowance shall only be allowed for those spaces symmetrical about the centreline which can be shown to remain intact following side damage of standard length extending to the centreline.
220.127.116.11 In order to comply with this paragraph, the subdivision of multi-hull ships must be considered symmetrically i.e. compartments must be assumed to be flooded in centre, port and starboard hulls at the same time.
Corresponding bulkheads in each hull should normally be in the same longitudinal position. Where this is not compatible with the design, the shipbuilder should submit details of the measures which are to be adopted in order to maintain the same measure of safety presented by a plane bulkhead.
2.5.7 Verification of subdivision particulars 18.104.22.168 The surveyor is to ensure that the submitted particulars are correct, and that all measurements upon which flooding curves or equivalent calculations are based closely correspond to the ship as building, and adequately define the volumes used in the computation.
22.214.171.124 The designers/builders of the ship should be informed that, in the event of any alteration to the lines plan or subdivision arrangements, all relevant plans should be revised immediately, and forwarded to the surveyor for consideration with revised flooding curves or equivalent calculations.
2.5.8 Verification of watertight subdivision arrangements When the watertight subdivision arrangements have been accepted, the surveyor should satisfy himself that the ship is built in accordance with the accepted
arrangements. The procedure described below should generally be followed:
126.96.36.199 Spacing of watertight bulkheads The positions of the main transverse bulkheads should be checked at ship against the accepted subdivision plans, together with those of the accepted steps and recesses in the watertight bulkheads, and the arrangements of the longitudinal watertight and non-watertight bulkheads.
188.8.131.52 Appropriation of spaces
The surveyor should examine each space, and satisfy himself that it has been fitted out in accordance with the appropriation of spaces upon which the calculations for average permeabilities, and criterion of service numeral, have been calculated, and as shown on the accepted plans. If it appears that a
184.108.40.206 Survey of watertight subdivision arrangement before painting, etc.
The survey of a ship during construction is for the purpose of enabling the surveyor to form an opinion of the construction and workmanship and the surveyor should not undertake the survey of a new ship after the hull is painted, cemented or otherwise coated. Where such coatings have been applied prior to survey the surveyor should report full particulars to the lead surveyor for the ship in question, and await instructions about the action to be taken. Particular care should be exercised by the surveyor to satisfy himself that the integrity of the watertight subdivision, where pipes etc. pass through steps or recesses in watertight bulkheads, is not impaired.
2.6 Construction of Watertight Bulkheads, etc. (Regulation 9)
In the application of paragraph 1(2) of Schedule 4 to Merchant Shipping Notice MSN 1698 (M) the strength and construction of every watertight subdivision bulkhead, or other portion of the internal structure forming part of the watertight subdivision of the ship, shall be of sufficient strength capable of supporting, with an adequate margin of resistance, the pressure due to the maximum head of water which it might have to sustain in the event of damage to the ship. The pressure head is not to be less than the pressure due to a head of water up to the margin line, including any additional head estimated to result from flooding or heeling, when calculating stability in the damaged condition.
2.6.1 Initial tests of bulkheads, etc.
The requirements for initial tests of bulkheads, watertight flats are contained in Section 1 of Schedule 4 of Merchant Shipping Notice MSN 1698 (M).
220.127.116.11 All watertight bulkheads, decks, etc. should be examined by the surveyor.
18.104.22.168 Main compartments may be tested by filling with water, but this is NOT compulsory. Where this is not carried out, a hose test should be applied to the bulkheads.
22.214.171.124 A hose or flooding test should be applied to watertight decks, and a hose test to watertight trunks, ventilators and tunnels.
126.96.36.199 Hose testing of watertight bulkheads, including the watertight doors and the attachments of the door frame to the bulkheads, decks and tunnels, should be simultaneously inspected on both sides of the plating while the water is being played upon all connections.
188.8.131.52 These tests are for the purpose of ensuring that the subdivision structural arrangements are watertight, and should not be regarded as a test of the fitness of any compartment for the storage of liquids, or for other special purposes for which a test of a superior character may be required; such superior tests may be accepted in substitution, depending on the height to which the liquid has access in the tank or its connections.
184.108.40.206 The hose and pressure tests should be carried out in the presence and to the satisfaction of the surveyor, who should record the results of the test on the appropriate file.
220.127.116.11 When testing arrangements considered equivalent to the above are proposed, full details should be submitted to Headquarters.
2.7 Collision, Machinery Space and Afterpeak Bulkheads and Shaft Tunnels (Regulation 10) 2.7.1 Extension to the collision bulkhead 18.104.22.168 Where a ramp or door forms part of the extension to the collision bulkhead, the intention of Regulations 10(6) and 10(7) is that it shall open forward.
22.214.171.124 In ships fitted with a bow ramp to facilitate the loading and/or unloading of vehicles at the fore end, such a ramp may be accepted as the extension to the collision bulkhead in compliance with Regulation 10(1).
Details of the position, construction and means of making the ramp weathertight should be submitted for consideration by Headquarters.
126.96.36.199 The requirement for ships constructed before 1 July 1997 is to ensure that if fore end damage occurs resulting in damage to the bow visor, where fitted, that the integrity of the bow ramp forming the extension to the collision bulkhead is not at risk. This effectively excludes those existing arrangements which have an articulated outer portion of the ramp stowed horizontally under the deckhead from being considered as an extension to the collision bulkhead. However, arrangements have been accepted where the two portions are disconnected when in the stowed position. Where unusual arrangements exist, surveyors are to submit as much detail as is available to Headquarters for consideration.
188.8.131.52 Some existing Class II(A) ships have been found to have extensions not complying with the new requirements and, in lieu of retrofitting, “open bow” model tests have been accepted. As it is considered that all existing ships have been identified and considered, no details of the test requirement is considered necessary. Surveyors are advised to note the foregoing when
2.7.2 Shaft tunnels 184.108.40.206 The watertight shaft tunnel, or other watertight space in which, under Regulation 10(3), the stern gland is to be situated, should be of sufficient height and width to allow proper attention to be given to shaft couplings, bearings etc. within the space.
220.127.116.11 The stern tube should be enclosed a watertight compartment the volume of which should be the smallest compatible with the proper design of the ship.
2.8 Double Bottoms (Regulation 11) 2.8.1 Inner bottom The inner bottom may be pierced by the minimum number of access manholes compatible with the design and safe working of the ship, providing such manholes are fitted with efficient covers and provided the joint between the cover and the inner bottom is watertight.
2.8.2 Air and sounding pipes All air and sounding pipes to double bottom compartments are to be effectively protected against the risk of damage and located so far as practical to avoid damage.
2.8.3 Depth of double bottom and suitability to protect the turn of bilge 18.104.22.168 The moulded depth of a double bottom in millimetres measured at the centreline should not be less than 406 plus 4.17 times the length of the ship in metres.
22.214.171.124 The requirement of Regulation 11(3) regarding the suitability of the inner bottom protecting the turn of bilge is illustrated by figure 2.8.3.
126.96.36.199 The surveyor's attention is drawn to the fact that Regulation 11(4) does not permit either the depth of drain wells to be more than the depth of the double bottom at centre less 460 mm, or the wells to extend below the horizontal plane referred to in Regulation 11(3).
188.8.131.52 If wells for purposes other than drainage are proposed, and the surveyor considers they are essential, they should be as small as possible and full particulars of the method to be adopted for maintaining the protection given by the double bottom should be submitted to Headquarters to establish whether or not an exemption from Regulation 11(5) can be granted.
2.9 Weather-deck (Regulation 12)