Section 2 Welding and Fabrication

201. General

1. Welding

(1) Welding in SPM hull or buoy construction of the mooring system is to comply with the re- quirement of this section.

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(2) It is recommended that appropriate permanent markings be applied to the side shell of welded SPM buoys or hulls to indicate the location of bulkheads for reference.

(3) In all instances, welding procedures and filler metals are to produce sound welds having

strength and toughness comparable to the base material.

(4) Welding of tubular and/or bracing members which may be used in tower mooring is to comply with Pt 2 of "Rules for classification of Steel ships."

2. Plans and specification

(1) The plans submitted are to clearly indicate the proposed extent of welding to be used in the principal parts of the structure.

The welding process, filler metal and joint design are to be shown on the detail drawings or in

separate specifications submitted for approval.

(2) The builders are to prepare and file with the Surveyor a planned procedure to be followed in the erection and welding of the important structural members.

3. Workmanship and supervision

(1) The Surveyor is to satisfy himself that all welders and welding operators to be employed in the construction of SPMs to be classed are properly qualified and are experienced in the work proposed.

(2) Inspection of welds employing methods outlined in 203. 9. is isfaction of the Surveyor.

4. Welding procedures

(1) General

to be carried out to the sat-

Welding procedure qualification test is to comply with Classification of Steel ships."

Pt 2,

Ch 2, Sec 4 of "Rules for

(2) Weld Metal Toughness-Criteria for steels for hull Pt 2, Ch 2.

Steel ships."

(3) Weld Metal Toughness -Criteria for Other Steels

of "Rules for Classification of

Weld metal is to exhibit Charpy V-notch toughness values at least equivalent to transverse base metal requirements.

202. Preparation for welding

1. Edge preparation and fitting

(1) The edge preparation is to be accurate and uniform and the parts to be welded are to be fitted in accordance with the approved joint detail. All means adopted for correcting improper fitting are to be to the satisfaction of the attending Surveyor.

(2) The Surveyor may accept a welding procedure for build up of each edge that does not exceed one half the thickness of the member or 12.5 mm, whichever is the lesser.

(3) Where plates to be joined differ in thickness and have an offset on either side of more than 3

mm, a suitable transition taper is to be provided. For butts in bottom shell, strength deck plat- ing and other joints which may be subject to comparatively high stresses, the transition taper length is to be not less than three times the offset. The transition may be formed by tapering the thicker member or by specifying a weld joint design which will provide the required transition.

2. Alignment

Means are to be provided for maintaining the parts to be welded in correct position and alignment during the welding operation. In general, strong backs, or other appliances used for this purpose are to be so arranged as to allow for expansion and contraction during production welding. The re- moval of such items is to be carried out to the satisfaction of the Surveyor.

3. Cleanliness

(1) All surfaces to be welded are to be free from moisture, grease, loose mill scale, excessive rust or shop primer coatings of ordinary thicknesses, thin coatings of linseed oil, or equivalent coat- ings may be used provided it is demonstrated that their use has no adverse effect in the pro- duction of satisfactory welds.

(2) Slag

pass

and scale are to be or layer before the

removed not only from the edges to be welded but also from each deposition of subsequent passes or layers. Weld joins prepared by

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arc-air gouging may require additional preparation by grinding or chipping and wire brushing prior to welding to minimize the possibility of excessive carbon on the scarfed surfaces. However, these cleanliness requirements is of prime importance in the welding of higher strength steels especially those which are quenched and temperd.

4. Tack welds

(1) Tack welds of consistent good quality, made with the same grade of filler metal as intended for production welding and deposited in such a manner as not to interfere with the completion of the final weld, need not be removed provided they are found upon examination to be thor- oughly clean and free from cracks or other defects.

(2) Preheat may be necessary prior to tack welding when the materials to be joined are highly restrained. Special consideration is to be given to use the same preheat as specified in the welding procedure when tack welding higher-strength steels, particularly those materials which are quenched and tempered. These same precautions are to be followed when making any per- manent welded markings.

5. Run-on and run-off tabs

When used run-on and run-off tabs are to be fitted to minimize the possibility of high-stress con- centrations and base-metal and weld-metal cracking.

6. Stud welding

The use of stud welding for structural attachments is subject to special approval and may require special procedure tests appropriate to each application.

203. Production welding

1. Environment

Proper precautions are to be taken to insure that all welding is done under conditions where the welding site is protected against the deleterious effects of moisture, wind and severe cold.

2. Sequence

Welding is to be planned to progress symmetrically so that shrinkage on both sides of the structure will be equalized. The ends of frames and stiffeners should be left unattached to the plating at the subassembly stage until connecting welds are made in the intersecting systems of plating, framing and stiffeners at the erection stage.

3. Preheat

(1) The use of preheat and interpass temperature control are to be considered when welding high- er- strength steels, materials of thick cross-section or materials subject to high restraint. When welding is performed under high humidity conditions or when the surface temperature of steel is

below 0 ℃, the control of interpass temperature is to be specially considered

(2) The control of interpass temperature is to be specially considered when welding quenched and

tempered higher-strength steels.

(3) When preheat is used the preheat and interpass temperatures are to be in accordance with the accepted welding procedure.

4. Low-hydrogen electrodes or welding processes

(1) Welding of ordinary and higher strength steel

The use of low-hydrogen electrodes or welding processes is recommended for welding all high- er-strength steel and may also be considered for ordinary-strength steel weldment subject to high restraint. When using low-hydrogen electrodes or processes, proper precautions are to be taken to ensure that the electrodes, fluxes and gases used for welding are clean and dry.

(2) Welding of quenched and tempered steels

Unless approved otherwise, matching strength low-hydrogen electrodes or welding processes arc to be used for welding quenched and tempered steels and overmatching should be generally avoided. When welding quenched and tempered steels to other steels, the weld filler metal se- lection is. to be based on the lower strength. base material being joined and low-hydrogen prac- tice being comparable to that for the higher strength material. In all cases, filler metal strength

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is to be no less than that of the lowest strength member of the joint unless approved otherwise.

5. Back gouging

(1) Chipping, grinding, arc-air gouging or other suitable methods are to be employed at the root or underside of the weld to obtain sound metal before applying subsequent beads for all full-pene- tration welds.

(2) When arc-air gouging is employed, a selected technique is to be used so that carbon buildup and burning of the weld or base metals minimized. Quenched and tempered steels are not to be

flame gouged.

6. Peening

The use of peening is tipass welds. Peening,

not recommended for single-pass weld and the root or cover passes on mul- when used to correct distortion or to reduce residual stresses, is to be ef-

fected immediately after depositing and cleaning each weld pass.

7. Fairing

Fairing for correcting distortion in fabrication of main strength members and other plating which may be subject to high stresses is to be carried out only with the express approval of the Surveyor.

8. Visual inspection

The welds are to be regular and uniform with a minimum amount of reinforcement and reasonably free from undercut and overlap. Welds and adjacent base metal are to be free from injurious de- fects such as arc strikes etc.

9. Non-destructive inspection of welds

(1) Inspection of welded joints in important locations is to be carried out by an approved non-de- structive test.

(2) Annex 2-9 "Giudance for Radiographic and Ultrasonic inspection of Hull Welds" of Pt 2

"Guidances relating to rules for classification of steel ships" or an approved equivalent standard is to be used in evaluating radiographs and ultrasonic indications.

(3) Radiographic or ultrasonic inspection, or both, is to be used when the overall soundness of the

weld cross section is to be evaluated. Magnetic-particle or dye-penetrant inspection or other ap- proved methods are to be used when investigating the outer surface of welds or maybe used as a check of intermediate weld passes such as root passes and also to check back-gouged joints prior to depositing subsequent passes.

(4) Surface inspection of important fillet joints, using an approved magnetic particle or dye pene- trant method is to be conducted.

(5) Extra high-strength steels, (minimum yield strength, 415-690 ) may be susceptible to de- layed cracking. When welding these materials, the final NDT is to be delayed sufficiently to permit detection of such defects. Weld run-on or run-off tabs may be used where practical and be sectioned for examination.

10. Repair welding

(1) Defective welds and other injurious defect, as determined by visual inspection; non-destructive test methods, or leakage are to be excavated in way of the defects to sound metal and cor- rected by rewelding using a suitable repair welding procedure to be consistent with the material being welded.

(2) Removal by grinding of minor surface imperfections such as scars, tack welds and arc strikes may be curried out where permitted by the attending Surveyor.

(3) Special precautions, such as the use of preheat interpass temperature control, and low-hydrogen

electrodes, are to be considered when repairing welds in all higher strength steel, ordinary

strength steel of thick

(4) In all cases, preheat surfaces.

cross section, or steel subject to high restraint.

and interpass temperature control are to be sufficient to maintain dry