Materials of Construction and welding
Clasification Society 2024 - Version 9.40
Clasifications Register Rules and Regulations - Rules and Regulations for the Construction and Classification of Ships for the Carriage of Liquid Chemicals in Bulk, July 2022 - The Rules and Regulations for the Construction and Classification of Liquid Chemicals in Bulk - Materials of Construction and welding

Materials of Construction and welding

Parent topic: The Rules and Regulations for the Construction and Classification of Liquid Chemicals in Bulk

6.1 Materials of construction and welding

6.1 Structural materials used for tank construction, together with associated piping, pumps, valves, vents and their jointing materials, shall be suitable at the temperature and pressure for the cargo to be carried in accordance with recognized standards. Steel is assumed to be the normal material of construction.

6.2 The shipyard is responsible for providing compatibility information to the ship operator and/or master. This must be done in a timely manner before delivery of the ship or on completion of a relevant modification of the material of construction.

LR 6.2(a) The requirement of Ch 1, 6.1 Materials of construction and welding only deals with the compatibility of the material of construction with the intended cargoes. Material of construction is to comply with the requirements of the Rules for Materials and any modification of the material of construction is to be submitted for approval.

6.3 Where applicable, the following should be taken into account in selecting the material of construction:

  1. notch ductility at the operating temperature;

  2. corrosive effect of the cargo; and

  3. possibility of hazardous reactions between the cargo and the material of construction.

LR 6.3(a) Except where otherwise required by the provisions of this Code the materials are to comply with the Rules for the Manufacture, Testing and Certification of Materials, July 2022.

LR 6.3(b) Materials for cargo piping systems are to comply with the requirements of Pt 5, Ch 12 Piping Design Requirements of the Rules for Ships for Class II systems. Materials for open ended and vent piping may be to Class III requirements. See also Ch 1, 6.1 Materials of construction and welding.

LR 6.3(c) The grade of steel to be used in hull construction is in general related to the thickness of the material and, stress pattern associated with its location and notch ductility at the minimum operating temperature. Steels with different levels of notch toughness are specified in the Rules for Materials.

LR 6.3(d) The material grade requirements for different hull members are given in Pt 3, Ch 2, 2 Fracture control of the Rules for Ships.

LR 6.3(e) Where product purity is particularly important, a material of enhanced corrosion resistance may be necessary, and the shipyard shall advise accordingly, see 6.2.

LR 6.3(f) Hatch packing material is to be resistant to both the liquids and vapours to which it is exposed and is to be efficiently held in place.

LR 6.3(g) When aluminium is used in tank construction, requirements for the material are to comply with the Rules for Materials.

LR 6.3(h) Where stainless steel is required or accepted as an alternative to mild steel then it is to be essentially an austenitic or duplex type and comply with the appropriate requirements of the Rules for the Manufacture, Testing and Certification of Materials, July 2022. Alternative, austentic or duplex grades of stainless steel may be accepted provided they comply with National or Proprietary specifications and are suitable for the intended purpose.

LR 6.3(j) The surface finish specification and permissible repair procedures for stainless steel surfaces for cargo tanks are to be agreed between the Owner, the Builder and the steel supplier of the stainless steel plate or clad carbon steel plate on the purchase order, see also LR IV.1 .

LR 6.3(k) In general, stainless steel tanks are not to be used for the carriage of sea water. Mild steel fittings are not permitted in stainless steel cargo tanks.

LR 6.3(l) The suitability of coatings and compatibility with intended cargoes are the responsibility of the Builder and the Owner. A copy of the coating manufacturer's product resistance list is to be placed on board.

LR 6.3(m) Materials of construction having a melting point below 925°C, e.g. aluminium and its alloys, should not be used for external piping involved in cargo-handling operations on ships intended for the carriage of products with flashpoints not exceeding 60°C (closed cup test) unless specified by the shipyard, see Ch 1, 6.1 Materials of construction and welding Short lengths of external pipes connected to cargo tanks may be fitted if they are provided with fire-resistant insulation. These requirements do not apply to cargo hoses.

LR 6.3(n) Where a pre-fabrication primer is used, it is to comply with the requirements of Pt 3, Ch 2, 3 Corrosion protection of the Rules for Ships.

LR 6.3(o) Pre-fabrication primers containing zinc are not to be applied to stainless steel. Where zinc primers are applied to other materials which are to be welded, the arrangements are to be such as to preclude zinc contamination of the stainless steel components.

LR 6.3(p) See Ch 1, 15.11 Acids 15.11.2 concerning the lining of tanks and piping systems.

LR 6.3(q) Where applicable, a sacrificial anode cathodic protection system may be used for the protection of the ballast tanks providing there is no other limitation on the use of the anode material. For details of anode design, attachment and location see Pt 3, Ch 2, 3 Corrosion protection of the Rules for Ships.

LR 6.3(r) Where special structural materials and linings have been used, a plan showing the location and grades of material utilised is to be placed on board the ship.

LR 6.3(s) Welding is to be performed using welding procedures that have been qualified by testing in accordance withCh 12 Welding Qualifications of the Rules for Materials.

LR 6.3(t) Welders and welder operators are to possess the necessary skills for the type of materials to be welded and the quality of work to be undertaken. Welders are to be qualified in accordance with the requirements of Ch 12 Welding Qualifications of the Rules for Materials.

LR 6.3(u) All construction welding is to be performed in accordance with the requirements of the Ch 13 Requirements for Welded Construction of the Rules for Materials.

LR 6.3(v) Inspection of all welded construction is to be in accordance with the requirements specified in Ch 13 Requirements for Welded Constructionof the Rules for Materials.

LR 6.3(w) In addition, the following non-destructive examination is to be carried out on ships to be assigned the class notation ‘Chemical tanker’:

  1. All crossings of butts and seams of cargo tank bulkhead plating joints welded in assembly areas or on the berth.

  2. Where cargo tank boundary welding is completed in assembly areas or on the berth, a minimum of 10 per cent of the total weld length is to be crack detected.

  3. Where side and bottom longitudinal framing and longitudinal stiffeners terminate at transverse bulkheads, a minimum of 10 per cent of the bulkhead boundary connections is to be crack detected in addition to the requirement given in Ch 1, 6.1 Materials of construction and welding 6.1..(b).

  4. Where longitudinal framing and longitudinal bulkhead stiffeners are continuous through transverse bulkheads, 30 per cent each of the bottom and shipside boundaries and 20 per cent of the longitudinal bulkhead boundaries are to be crack detected in addition to the requirement given in Ch 1, 6.1 Materials of construction and welding 6.1..(b).

  5. Where transverse framing members are continuous through the cargo tank boundary, a minimum of 10 per cent of boundary connections is to be crack detected.

6.4 The shipper of the cargo is responsible for providing compatibility information to the ship operator and/or master. This must be done in a timely manner before transportation of the product. The cargo shall be compatible with all materials of construction such that:

  1. no damage to the integrity of the materials of construction is incurred; and/or

  2. no hazardous, or potentially hazardous reaction is created.

6.5 When a product is submitted to IMO for evaluation, and where compatibility of the product with materials referred to in paragraph 6.1 renders special requirements, the BLG Product Data Reporting form shall provide information on the required materials of construction. These requirements shall be reflected in chapter 15 and consequentially be referred to in column o of chapter 17. The reporting form shall also indicate if no special requirements are necessary. The producer of the product is responsible for providing the correct information.

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