Section 2 Materials

2.1.1 Materials are to comply with Pt 3, Ch 2 Materials.

2.1.2 Attention is drawn to the specific requirements for container ship hatch corners in Table 2.2.1 Buckling factors of safety, λ, Note 1 in Pt 3, Ch 2 Materials.

2.2.1 In addition to the requirements of Pt 3, Ch 2, 3 Corrosion protection the requirements of Pt 4, Ch 1, 2.2 Protection of steelwork 2.2.3 may also be applied.

2.3.1 This Section provides the requirements for crack arrest design to reduce the risk of brittle fractures in container ships where thick steel plates are applied for longitudinal structural members in the upper deck region. The upper deck region comprises upper deck plating, hatch side coaming plating, hatch coaming top plating and attached longitudinals.

2.3.2 This Section is to be applied to container ships where the steel plates for longitudinal structural members exceed a thickness of 50 mm but are not greater than 100 mm. Special consideration is required for plates with a thickness exceeding 100 mm.

2.3.3 This Section applies to plates having specified minimum yield strength of 355, 390 and 460 N/mm². Steels and weldments are to comply with the toughness requirements of Ch 3 Rolled Steel Plates, Strip, Sections and Bars, Ch 11 Approval of Welding Consumables and Ch 12 Welding Qualifications of the Rules for the Manufacture, Testing and Certification of Materials, July 2022.

2.3.4 Where steel having specified minimum yield strength of 460 Nmm² is utilised the material grade is to be EH.

2.3.5 The approach in this Section generally applies to the erection block-to-block joints. Appropriate measures are to be considered to prevent large scale fracture of the hull girder in anticipation of the following:

1. Crack initiation in the block-to-block butt weld joint in either the hatch side coaming or upper deck. Crack propagates along the butt weld joint without deviation.

2. Crack initiation in the block-to-block butt weld joint in either the hatch side coaming or upper deck. Crack propagates away from the butt weld joint running into base metal.

3. Crack initiation in any welded joint, for example in way of attachment welds, and deviates away from the butt weld joint running into base metal.

2.3.6 The detailed arrangements for crack arrest design are to be submitted for approval.

2.3.7 A number of measures are given in Table 8.2.1 Preventative measures to be used in design and construction for thick steel plates which are considered to be acceptable means of addressing the cases given in Pt 4, Ch 8, 2.3 Requirements for use of thick steel plates 2.3.5. A range of thicknesses is shown for the different strength grades of steel. Where the maximum as-built thickness of the hatch coaming top plate and side plate falls within this range, measures are to be selected as shown in the Table. If the as-built thickness of the hatch coaming top plate and side plate is below the values contained in the Table, then additional measures are not necessary regardless of the thickness and yield strength of the upper deck plating. The application of these measures is described in Pt 4, Ch 8, 2.3 Requirements for use of thick steel plates 2.3.8 to Pt 4, Ch 8, 2.3 Requirements for use of thick steel plates 2.3.13.

2.3.8 Where Measure 1 is required in Table 8.2.1 Preventative measures to be used in design and construction for thick steel plates, 100 per cent ultrasonic testing in accordance with Ch 13, 2.12 Non-destructive examination of steel welds of the Rules for the Manufacture, Testing and Certification of Materials, July 2022, both application and acceptance criteria, is to be carried out on all block-to-block butt joints of all upper flange longitudinal structural members in the cargo hold region. Upper flange longitudinal structural members include the topmost strakes of the inner hull/bulkhead, the sheer strake, main deck, coaming plate, coaming top plate, and all attached longitudinal stiffeners. These members are defined in Figure 8.2.1 Upper flange longitudinal structural members.

Figure 8.2.1 Upper flange longitudinal structural members

2.3.9 Where Measure 2 is required as a result of the assessment carried out in accordance with the ShipRight Procedure for the Use of Enhanced NDE for Container Ships, see Pt 4, Ch 8, 2.3 Requirements for use of thick steel plates 2.3.10.(d) in Table 8.2.1 Preventative measures to be used in design and construction for thick steel plates, there may be a need for periodic NDE during service. For such cases the frequency and extent is to be agreed with LR.

2.3.10 Where Measure 3 is required in Table 8.2.1 Preventative measures to be used in design and construction for thick steel plates, the following are considered to be acceptable examples of brittle crack arrest design for the case given in Pt 4, Ch 8, 2.3 Requirements for use of thick steel plates 2.3.5.(a):

1. Where the block-to-block butt welds of the hatch side coaming plate and those of the upper deck are staggered, this offset is to be greater than or equal to 300 mm. This offset distance is defined in Figure 8.2.2 Minimum offset between block-to-block butt welds of the hatch side coaming and those of the upper deck staggered. Brittle crack arrest steel, as defined in Pt 4, Ch 8, 2.3 Requirements for use of thick steel plates 2.3.14, is to be provided for the hatch side coaming plate.

2. Where crack arrest holes are provided in way of the block-to-block butt welds at the region where the hatch side coaming weld meets the deck weld, see Figure 8.2.3 Crack arrest hole in way of the block-to-block butt weld at the region where hatch side coaming weld meets the deck weld, the corners of the crack arrest holes located where the hatch side coaming joints meet the deck weld are to be specially assessed for fatigue strength. The fatigue strength is also to be assessed at the location where the block-to-block butt weld intersects the crack arrest hole. Brittle crack arrest steel, as defined in Pt 4, Ch 8, 2.3 Requirements for use of thick steel plates 2.3.14, is to be provided for the hatch side coaming plate.

3. Where higher crack arrest steel insert plates such as SUF (Surface Layer with Ultra-Fine grain) steel or equivalent, or weld metal inserts with high crack arrest toughness properties are provided in way of the block-to-block butt welds at the region where hatch side coaming weld meets the deck weld. Brittle crack arrest steel, as defined in Pt 4, Ch 8, 2.3 Requirements for use of thick steel plates 2.3.14, is to be provided for the hatch side coaming plate.

4. As an alternative to the mechanical measures (i.e. block offset, or crack arrest inserts, or crack arrest holes, or high arrest toughness welds), with the provision of crack arrest steel for the hatch coaming side plate stipulated in Pt 4, Ch 8, 2.3 Requirements for use of thick steel plates 2.3.10.(a), Pt 4, Ch 8, 2.3 Requirements for use of thick steel plates 2.3.10.(b) and Pt 4, Ch 8, 2.3 Requirements for use of thick steel plates 2.3.10.(c), enhanced non-destructive examination can be carried out in association with stricter acceptance criteria. The acceptance criteria are to be determined in accordance with Chapter 2 of the ShipRight Procedure for the Use of Enhanced NDE in Container Ships,and the enhanced NDE is to be carried out in accordance with Chapter 3 of the ShipRight Procedure for the Use of Enhanced NDE in Container Ships. For areas of the weld which are inaccessible for enhanced NDE, alternative NDE procedures using the same acceptance criteria as the enhanced NDE are to be agreed with LR as described in the ShipRight Procedure for the Use of Enhanced NDE in Container Ships. The weld toughness of the block to block butt welds of the hatch coaming side plate, hatch coaming top plate and upper deck is to be as required by Pt 4, Ch 8, 2.3 Requirements for use of thick steel plates 2.3.13 and EGW welding is not permitted.

Figure 8.2.2 Minimum offset between block-to-block butt welds of the hatch side coaming and those of the upper deck staggered

Figure 8.2.3 Crack arrest hole in way of the block-to-block butt weld at the region where hatch side coaming weld meets the deck weld

2.3.11 Where Measure 4 is required in Table 8.2.1 Preventative measures to be used in design and construction for thick steel plates for the cases given in Pt 4, Ch 8, 2.3 Requirements for use of thick steel plates 2.3.5.(b) the use of brittle crack arrest steel, as defined in Pt 4, Ch 8, 2.3 Requirements for use of thick steel plates 2.3.14, for the upper deck along the cargo hold region is considered to be an acceptable means to arrest a brittle crack initiating from the coaming side and top plate and propagating into the structure below.

2.3.12 Where Measure 5 is required in Table 8.2.1 Preventative measures to be used in design and construction for thick steel plates for the case given in Pt 4, Ch 8, 2.3 Requirements for use of thick steel plates 2.3.5.(c), the use of brittle crack arrest steel, as defined in Pt 4, Ch 8, 2.3 Requirements for use of thick steel plates 2.3.14, for the upper deck along the cargo hold region is considered to be an acceptable means to arrest a brittle crack initiating from the coaming side and top plate and propagating into the structure below.

2.3.13 Where enhanced NDE is used to achieve Measure 3 see Pt 4, Ch 8, 2.3 Requirements for use of thick steel plates 2.3.10.(d), the block to block butt welds of the hatch coaming side plate, hatch coaming top plate and upper deck are to have a minimum crack tip opening displacement (CTOD) value of 0,18 mm. The CTOD tests to confirm the CTOD value are to be carried out to the satisfaction of LR.

2.3.14 Brittle crack arrest steel is to be in accordance with Table 8.2.2 Brittle crack arrest steel requirement in function of structural members and thickness and as defined in the Rules for the Manufacture, Testing and Certification of Materials, July 2022, Ch 3, 3 Higher strength steels for ship and other structural applications.

2.3.15 The weld joints between the hatch coaming side and the upper deck are to be partial penetration welds approved by LR.

2.3.16 In the vicinity of ship block joints, alternative weld details may be used for the deck and hatch coaming side connection, provided additional means for preventing the crack propagation are implemented and agreed by LR in this connection area.

2.3.17 Where higher crack arrest steel or weld inserts are proposed, as given in Pt 4, Ch 8, 2.3 Requirements for use of thick steel plates 2.3.10.(c), the specific properties or grades of material are to be agreed with LR.