Section 3 Procedures for welded construction
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Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Special Service Craft, July 2022 - Part 7 Hull Construction in Aluminium - Chapter 2 Construction Procedures - Section 3 Procedures for welded construction

Section 3 Procedures for welded construction

Parent topic: Chapter 2 Construction Procedures

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.

3.1.2 Cast aluminium alloys are not in general to be welded directly to wrought high magnesium alloys unless the welding is carried out in accordance with an agreed procedure.

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.

3.4.2 Structural arrangements are to be such as will allow adequate ventilation and access for preheating, where required, and for the satisfactory completion of all welding operations. Welded joints are to be so arranged as to facilitate the use of downhand welding wherever possible.

3.5 Heat treatment

3.5.1 For aluminium-magnesium alloys, the preheating temperature is to be limited to 60oC to avoid the risk of stress corrosion cracking.

3.5.2 With the 6000 series heat-treatable alloys, it is sometimes beneficial to apply a post-weld heat treatment in the form of artificial ageing. The procedure to be used depends on the alloy and, in order to quantify the benefits, tests are required using representative specimens which accurately simulate the true situation in terms of metal thickness, geometry, filler metal and welding parameters, as well as the post-weld treatment employed.

3.6 Inspection and non-destructive examination

3.6.1 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.

3.6.2 Checkpoints for volumetric examination are to be selected so that a representative sample of welding is examined.

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

Table 2.3.1 Non-destructive examination of welds

Volumetric non-destructive examinations - Recommended extent of testing, see Pt 7, Ch 2, 3.6 Inspection and non-destructive examination 3.6.3
Item Location Checkpoint, seeNote 1
Intersections of butts and seams of fabrication and section welds Throughout:
  • hull envelope
  • longitudinal and transverse bulkheads
  • inner bottom and hopper bottom
The summation of checkpoint lengths (see Note 2) examined at intersections is to be L, where L is the overall length of the ship in metres
Butt welds in plating Throughout 1 m in 25 m, see Note 3
Seam welds in plating Throughout 1 m in 100 m
Butts in longitudinals Hull envelope within 0,4L amidships

Hull envelope outside 0,4L amidships

1 in 10 welds

1 in 20 welds

Bilge keel butts Throughout 1 m in 20 m
Structural items when made with full penetration welding as follows:
  • 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
Throughout 1 m in 20 m

Note 1. The length of each checkpoint is to be between 0,3 m and 0,5 m.

Note 2. For checkpoints at intersections the measured dimension of length is to be in the direction of the butt weld.

Note 3. Checkpoints in butt welds and seam welds are in addition to those at intersections.

Note 4. Agreed 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.

Note 5. Particular attention is to be given to repair rates in longitudinal butts. Additional welds are to be tested in the event that defects, such as lack of fusion or incomplete penetrations, are repeatedly observed.

3.7 Acceptance criteria

3.7.1 All finished welds are to be sound and free from cracks and substantially free from lack of fusion, incomplete penetration, porosity and tungsten inclusions. The surfaces of 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.

3.7.2 The acceptance criteria are to be in accordance with Ch 13, 8 Specific requirements for welded aluminium of the Rules for Materials.

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