Section 1 General
Clasification Society 2024 - Version 9.40
Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Ships, July 2022 - Part 4 Ship Structures (Ship Types) - Chapter 11 Ore Carriers - Section 1 General

Section 1 General

Parent topic: Chapter 11 Ore Carriers

1.1 Application

1.1.1 This Chapter applies to the arrangements and scantlings within the cargo region of sea-going ore carriers, intended for the carriage of ore in centre holds.

1.1.2 The requirements of Pt 4, Ch 9 Double Hull Oil Tankers are to be applied to ore carriers, except as required by the provisions of this Chapter.

1.1.3 The scantlings of structural items may be determined by direct calculation. Where the length of the ship exceeds 150 m, the scantlings of the primary supporting structure and the fatigue performance of structural details are to be assessed in accordance with the relevant ShipRight procedures, see Pt 4, Ch 11, 1.3 Class notation 1.3.5. In such cases, the calculations are to be submitted for approval.

1.1.4 The additional requirements for ore-carriers for the alternate carriage of oil cargo and dry bulk cargo are given in Pt 4, Ch 9, 11 Ships for alternate carriage of oil cargo and dry bulk cargo.

1.1.5 Ore carriers with a deadweight greater than 200 000 tonnes are to comply with the requirements of Pt 4, Ch 11, 13 Single pass loading.

1.2 Structural configuration and ship arrangement

1.2.1 The requirements contained in the Chapter apply to single deck ships with machinery aft, having two longitudinal bulkheads and a double bottom throughout the centre hold. A typical cross-section is indicated in Figure 11.1.1 Typical cross-section.

Figure 11.1.1 Typical cross-section

1.2.2 The bottom, and the deck outside the line of ore hatchways, are to be framed longitudinally within the cargo region. The side shell and longitudinal bulkheads are generally to be framed longitudinally where the length of the ship exceeds 150 m, but alternative proposals will be specially considered. Inside the line of openings, the deck is to be transversely framed.

1.2.3 The notation Strengthened to carry cargoes which may liquefy (IMSBC Group A) is only applicable to ore carriers having a conventional structural configuration with cargo holds bounded by two longitudinal bulkheads widely separated from the side shell, see Figure 11.1.1 Typical cross-section.

1.3 Class notation

1.3.1 Sea-going ships complying with the requirements of this Chapter and other relevant Rule requirements for the draught required will be eligible to be classed 100A1 ore carrier, ESP.

1.3.2 The notation ESP serves to identify the ship as being subject to an Enhanced Survey Programme as detailed in Pt 1, Ch 3, 3 Intermediate Surveys - Hull and machinery requirements and Pt 1, Ch 3, 6 Special Survey - Bulk carriers - Hull requirements, see also Pt 1, Ch 2, 2.3 Class notations (hull) 2.3.12.

1.3.3 Where a vessel is built in accordance with the requirements detailed in this Section, the vessel will be eligible for the notation Strengthened to carry cargoes which may liquefy (IMSBC Group A). The requirements in this Section do not allow the loading of cargo with moisture content in excess of the transportable moisture limit (TML), as defined in the IMSBC Code, but instead make allowance for the rise in moisture content of the cargo above the TML after loading. Attention is drawn to Section 7.3.2.1 of the IMSBC Code.

1.3.4 The notation Strengthened to carry cargoes which may liquefy (IMSBC Group A) serves to identify the ship as being specially constructed for loads from Group A cargoes, as defined in the IMSBC Code.

The loading condition cargo density, ρc, applicable to this notation is not to be less than the virtual homogeneous load density as calculated based on MFull at maximum draught, see Pt 4, Ch 7, 1.8 Symbols and definitions. The virtual cargo density is calculated based on homogeneous cargo at maximum draught.

The density is to be agreed between the Owner and the Builder and is to be noted in the Loading Manual in this form: ‘Carriage of cargo with moisture content above TML shall only be undertaken if the cargo density is above <density> t/m3’.

To be eligible for this notation additional calculations are required to assess stresses from liquefied cargo. The following structures are to be assessed:
  1. Longitudinal bulkheads using one of the following cargo density cases:
    • Assessment using virtual cargo density, i.e. fully filled:
    • Assessment using cargo density higher than the virtual cargo density, i.e. partially filled:
      • According to Table 9.6.1 Inner hull and longitudinal oiltight bulkhead scantlings with the following considerations:
      • load height, h, measured up to the height of the cargo in the hold;
      • horizontal distance, b1, measured from the calculation point to the centreline as the filling level allows. When the level of the liquefied cargo is above the hold corner after the ship is heeled over, b1 is to be specially considered to ensure a correct increased load height, h + R b1, in the heeled state with roll angle θ; and
      • the results are to be corrected for density by applying a factor of ρc/1,025 to the load height.
  2. Transverse bulkheads using one of the following cargo density cases:
    • Assessment using virtual cargo density, i.e. fully filled:
      • According to Table 9.7.1 Transverse oiltight bulkhead scantlings with the following considerations:
      • load height, h, measured to the highest point of the hold; and
      • the results are to be corrected for density by applying a factor of ρc/1,025 to the load height.
    • Assessment using cargo density higher than the virtual cargo density, i.e. partially filled:
      • According to Table 9.7.1 Transverse oiltight bulkhead scantlings with the following considerations:
      • load height, h, measured up to the height of the cargo in the hold;
      • horizontal distance, b1, measured from the calculation point to the centreline as the filling level allows. When the level of the liquefied cargo is above the hold corner after the ship is heeled over, b1 is to be specially considered to ensure a correct increased load height, h + R b1, in the heeled state with roll angle θ; and
      • the results are to be corrected for density by applying a factor of ρc/1,025 to the load height.
  3. Intersection of continuous secondary and primary members according to Pt 3, Ch 10, 5.2 Arrangements at intersections of continuous secondary and primary members using loads in the same Section from Table 10.5.1 Total load transmitted to connection of secondary members (3)(b)(iii) in Pt 3 Ship Structures (General) with Kc = 1.
  4. Cross ties in wing tanks as per requirements for primary structure in this Chapter.
  5. Lower stool as per requirements for Pt 4, Ch 11, 1.3 Class notation 1.3.4.(c) transverse bulkheads.

Additionally, the vessel is to be designed in accordance with LR’s ShipRight SDA Procedure for Primary Structures of Ore Carriers..

1.3.5 Where the length of the ship is greater than 150 m, or where the structural arrangements are considered such as to necessitate it, the scantlings of the primary supporting structure are to be assessed by direct calculation and the ShipRight notations SDA, FDA and CM are mandatory, see Pt 4, Ch 11, 1.3 Class notation 1.3.7 and Pt 4, Ch 11, 11 Direct calculations.

1.3.6 For ore carriers where an assessment of multiple port loading and unloadinghas been carried out in accordance with the relevant ShipRight procedures and the ShipRight notation SDA has been assigned, an optional ShipRight notation MP can be assigned.

1.3.7 The ‘ShipRight Procedures’ for the hull construction of ships are detailed in Pt 3, Ch 16 ShipRight Procedures for the Design, Construction and Lifetime Care of Ships and the classification notations and descriptive notes associated with these procedures are given in Pt 1, Ch 2, 2 Character of classification and class notations.

1.3.8 The Regulations for classification and the assignment of class notations are given in Pt 1, Ch 2, 2 Character of classification and class notations.

1.4 Symbols and definitions

1.4.1 The following symbols and definitions are applicable to this Chapter unless otherwise stated:

L, B, D, T as defined in Pt 3, Ch 1, 6 Definitions.

b = the width of plating supported by the primary member, in metres or mm
h = the load head, in metres, applied to the item under consideration
k = higher tensile steel factor. For the determination of this factor, see Pt 3, Ch 2, 1 Materials of construction. For mild steel k may be taken as 1,0
l e = effective length of primary or secondary member, in metres, see Pt 3, Ch 3, 3 Structural idealisation.
s = spacing, in mm, of secondary members
Z = the section modulus, in cm3, of the primary or secondary member, in association with an effective width of attached plating determined in accordance with Pt 3, Ch 3, 3 Structural idealisation.

1.4.2 The expression `primary member' as used in this Chapter is defined as a girder, transverse, vertical web, stringer, cross-tie, buttress or double bottom floor. `Secondary members' are supporting members other than primary members.

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