Section 7 Welding repairs

7.1.1 The following guidance should be used for welding repairs. For repair of large areas of structure, the guidelines of Ch 3, 4 Survey during construction should be followed.

7.1.2 Repairs are to be carried out by workshops, repair yards and personnel who have demonstrated their ability to perform the appropriate type of repairs. Provisions are to be made for proper accessibility, staging lighting, ventilation and shelter.

7.1.3 Welding of hull structure is to be carried out by qualified welders in accordance with approved weld procedures using approved welding consumables suitable for the material being welded. Records of tests and valid certificates are to be made available for inspection by the Surveyor, or see Vol 1, Pt 6, Ch 6, 4 Requirements for welded construction of the Rules for Naval Ships.

7.1.4 Personnel carrying out NDE for the purpose of assessing the quality of welds are to be suitably qualified. Records of qualifications are to be made available for inspection by the Surveyor.

7.1.5 Visual inspection of welds is to be supplemented by Non-Destructive Examination in accordance with the requirements of Ch 13, 2.12 Non-destructive examination of steel welds of the Rules for Materials. The criteria for accepting NDE examination are given in Ch 2, Table 3.2.2 Weld defect acceptance levels for fabrication.

7.1.6 The quality and workmanship of the welding of all fittings and attachments to main structure, both permanent and temporary are to be equivalent to those of the main hull structure.

7.1.7 Temporary attachments to the hull are to be removed by cutting and grinding to avoid damage to the hull plating.

7.1.8 Welding repairs may be carried out on structure that is backed by water provided that the minimum thickness is 6 mm and the material is not grade E or higher. The steel must have a yield strength less than 360 N/mm² and suitably dried low hydrogen electrodes are to be used. To ensure that moisture is removed, the area to be welded should be preheated to a temperature above 5°C.

7.2.1 For the general requirements concerning the repair and assessment of fractures, see Ch 13 Fractures.

7.2.2 For the weld repair of fractures the requirements of Figure 15.7.1 Welding repairs for fractures in structure and Table 15.7.1 Weld repairs for fractures are to be complied with.

Figure 15.7.1 Welding repairs for fractures in structure

7.3.1 Insert plates are to be in accordance with the requirements of Ch 3, 2.4 Part replacement of plates.

7.4.1 Where it is proposed by Owners to permanently repair corroded, fractured or holed structure by means of welded doubling plates then, in certain circumstances, this can be accepted.

7.4.2 Doubling plates should not be accepted as a permanent repair in the following circumstances:

1. In way of local excessive corrosion: that is, plating and stiffeners corroded to a level equal to or greater than the maximum dimunition.

2. In way of holed shell plating and tank plating.

3. In way of fractured shell, deck and bulkhead plating.

7.4.3 Where circumstances are such that the Surveyors consider that welded doubling plates may be used as a permanent means of repair, the doubling plate is to be satisfactorily attached to the original structure with peripheral welds and slot welds, see Ch 13, 2.7 Closing plates of the Rules for Materials.

7.4.4 The Surveyors are to ensure that faying surfaces are suitably prepared and primed, prior to fitting the doubler.

7.4.5 The material grade for doublers should generally be similar and compatible to that of the original plate.

7.4.6 Buckled lattice structures are usually best dealt with by cropping out the affected areas and replacement as original. Additional support may be required.

7.4.7 Buckled or bent tubular structures may often be dealt with by cropping/fairing, and fitting well-connected sleeves of similar material, see Figure 15.7.2 Repair of tubular structure.

7.4.8 Proof testing of the equipment should be carried out after such repairs.

Figure 15.7.2 Repair of tubular structure

7.5.1 For details on the assessment of pitting and the type of repair to be undertaken, see Ch 12 Pitting.

7.6.1 Proprietary plastic filler materials are not to be used to restore strength and their use should be limited to pit filling applications where fairness is required (e.g. for underwater form or cosmetic appearance) or where a failure to fill will result in a weak spot for further corrosion (e.g. to avoid cracked paint around the edge of pits). The surface preparation procedures recommended by the manufacturer are to be strictly adhered to.