Section 3 Procedures for welded construction

3.1 General

3.1.1 Except as otherwise indicated below, all welded construction is to be conducted in accordance with the requirements specified in Ch 13 Requirements for Welded Construction of the Rules for Materials.

3.2 Information to be submitted

3.2.1 The plans and information submitted for approval are to clearly indicate details of the welded connections of the main structural members, including the type, disposition and size of welds.

3.3 Defined practices and welding sequence

3.3.1 The final boring out of propeller brackets and sterntubes and the fit-up and alignment of rudder bearings and jet units are to be carried out after the major part of the welding of the aft end of the craft is complete. The contacts between rudder stocks and propeller shafts with bearings are to be checked before the final mounting.

3.4 Structural arrangements and access

3.4.1 Ceilings, cabin sole, side and overhead linings are to be secured in such a manner as to be easily removed for the maintenance and inspection of the structure below.

3.5 Inspection and non-destructive examination

3.5.1 Inspection of welded construction is to be conducted in accordance with the requirements specified in Ch 13 Requirements for Welded Construction of the Rules for the Manufacture, Testing and Certification of Materials, July 2022, and the general NDE requirements as per Ch 1, 5.1 General NDE requirements of the Rules for the Manufacture, Testing and Certification of Materials, July 2022.

3.5.2 Checkpoints examined at the pre-fabrication stage are to include ultrasonic testing on examples of the stop/start points of automatic welding and magnetic particle inspections of weld ends.

3.5.3 Typical locations for volumetric examination and number of checkpoints to be taken are shown in Table 2.3.1 Non-destructive examinations of welds. A list of the proposed items to be examined is to be submitted for approval.

3.5.4 Alternative proposals to Table 2.3.1 Non-destructive examinations of welds will be considered on a case by case basis for example, implementing a statistical approach based on historical data and current trends, or implementing an enhanced quality assurance process scheme.

Table 2.3.1 Non-destructive examinations of welds

Volumetric non-destructive examinations - Recommended extent of testing
Item	Location	Checkpoints, see Notes 1,2 and 4 (these are common to all listed item locations)
Intersections of butt and seams of fabrication and section welds	Throughout: hull envelope longitudinal and transverse bulkheads inner bottom and hopper bottom	Checkpoints shall be taken at these locations; the summation of checkpoint lengths examined at intersections is to be 0,2L, where L is the overall length of the ship in metres.
Butt welds in plating	Throughout	1 m in 100 m, see Note 3
Seam welds in plating	Throughout	1 m in 200 m, see Note 3
Butts in longitudinals	Hull envelope within 0,4L amidships	1 in 40 welds
	Hull envelope outside 0,4L amidships	1 in 30 welds
Bilge keel butts	Throughout	1 in 40 welds
Structural items when made with full penetration welding as follows:	Throughout	1 m in 60 m
connection of stool and bulkhead to lower stool shelf plating vertical corrugations to an inner bottom hopper knuckles sheerstrake to deck stringer hatchways coaming to deck
Note 1. The length of each checkpoint is to be between 0,3m and 0,5m, where the length of weld permits. Note 2. For checkpoints at intersections the measured dimension of length is to be in the direction of the butt weld. See Figure 2.3.1 Inspection of checkpoints located on longitudinal stiffeners to Figure 2.3.3 Checkpoint positions in way of radiography and ultrasonic inspection on deck plating Note 3. Checkpoints in butt welds and seam welds are in addition to those at intersections. Note 4. The NDE checkpoint locations are not to be indicated on the blocks prior to the welding taking place, nor is any special treatment to be given at these locations.

3.5.5 Any checkpoint which contains a rejectable weld discontinuity shall be repaired, as appropriate, and retested. Furthermore, volumetric NDE shall be increased by an additional one checkpoint for each checkpoint failure, to be chosen at random by the Surveyor. This additional checkpoint is supplementary to the repaired/retested location.

3.5.6 Systematic defects or repetitive defects shall be investigated, rectified, and retested where appropriate. The extent of NDE checkpoints shall be increased in way of the areas, weld types or intersections, where the systematic or repeated defects are observed, by an additional 50 per cent of the affected item (listed in Item column of Table 2.3.1 Non-destructive examinations of welds, to determine the weld quality.

3.5.7 If there is evidence to suggest the overall welding quality is not of a satisfactory nature, then a further NDE checkpoint regime, and enhanced quality assurance process, shall be applied. The fabricator shall present to the Surveyor the additional measures and regime to be implemented.

3.5.8 If cracks of any type or size are detected, then Pt 6, Ch 2, 3.5 Inspection and non-destructive examination 3.5.5 and Pt 6, Ch 2, 3.5 Inspection and non-destructive examination 3.5.6 shall apply.

3.5.9 Isolated gas pores, slag inclusions, or metallic inclusions shall not be considered as systematic defects, however, they must be assessed individually with respect to the applicable acceptance criteria within LR Rules, and Pt 6, Ch 2, 3.5 Inspection and non-destructive examination 3.5.5 shall apply. All other defect types when repeatedly observed shall be considered as systematic defects, and Pt 6, Ch 2, 3.5 Inspection and non-destructive examination 3.5.6 shall apply.

The length of butt welds located at checkpoints on longitudinal stiffeners may be less than 300 mm for radiography or 500 mm for ultrasonic inspection. In such cases inspect as much of the welds as access permits.

Figure 2.3.1 Inspection of checkpoints located on longitudinal stiffeners

Note for illustration, drawing shows checkpoint in vertical butt direction. For seam welds, the checkpoint location may lay in the horizontal direction.

Figure 2.3.2 Checkpoint positions in way of radiography and ultrasonic inspection on hull plating

Note for illustration, drawing shows checkpoint in vertical butt direction. For seam welds, the checkpoint location may lay in the horizontal direction.

Figure 2.3.3 Checkpoint positions in way of radiography and ultrasonic inspection on deck plating

3.6 Acceptance criteria

3.6.1 The surfaces of all finished welds are to be reasonably smooth and substantially free from undercut and overlap. Care is to be taken to ensure that the specified dimensions of welds have been achieved and that both excessive reinforcement and underfill of welds are avoided.

3.6.2 The acceptance criteria are to be in accordance with the appropriate Tables contained within Ch 13, 2 Specific requirements for ship hull structure and machinery of the Rules for the Manufacture, Testing and Certification of Materials, July 2022.