WELDING AND FABRICATION RESULT

MUH. HIDAYAT ARIF  D311 12 003 20

CHAPTER III RESULT

A. UNDERSTANDING OF ABS RULES

3.1 WELDING AND FABRICATION

3.1.1 Preparation of Welding 1.

Edge Preparation  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 0,5 inchi, whichever is the lesser. Case 1 Thickness base metal t = 12 mm Welding gap = 5 mm So, maximum welding gap requirement is 3 mm Figure 1 : Sketch of Case 1 Procedure Build Up : t x 0,5 : 12 x 0,5 : 6 mm  compare with 12,5 Choose whichever is the lesser : 6 mm 12,5 mm Build Up Requirement Figure 2 : Build Up Process MUH. HIDAYAT ARIF  D311 12 003 21 Case 2 Thickness base metal t = 30 mm Welding gap = 16 mm So, maximum welding gap requirement is 3 mm Figure 3 : Sketch of Case 2 Procedure Build Up : t x 0,5 : 30 x 0,5 : 15mm  compare with 12,5 Choose whichever is the lesser : 12,5 mm Can Not Build Up Solution of above problem, Rules with No. 47 IACS Shipbuilding and Repair Quality Standard For New Contruction and For Existing may be applied.  When 5 mm Gap  16 mm Build up gap with welding on one or both sides of preparation, with possible use of backing strip as necessary, to maximum 16 mm.  When 16 mm Gap 25 mm Welding up with edge preparation or partly renew welding.  When Gap 25 mm An insert plate, of minimum width 300 mm, to be welded in place. According the above rules, the case 2 may be applied Backing Strips See Figure 4 Figure 4 : Backing Strips  The Surveyor may accept edge build up in excess of the above, up to the full thickness of the member on a case-by-case basis, provided the Surveyor is notified of such cases MUH. HIDAYAT ARIF  D311 12 003 22 before the members are welded together. Where plates to be joined different in thickness and have an offset on either side of more than 3 mm 18 in., a suitable transition taper is to be provided.  For the transverse butts in bottom shell, sheer strake, and strength deck plating within the midship portion of the hull, 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 following of taper procedure are Figure 5 :

1. Determine the difference thickness of the two plates to be at joint. See Figure A.

T = 7 mm – 5 mm = 2 mm 2. Determine the taper length L. Based on the rules ABS Point 2, taper length is 3 x T = 6 mm. See Figure B 3. Later, the difference between the plate thickness associated eith the length of taper. Eventually, cutting the plates as shown C. Figure 5 : Taper Process 2. Run-on and Run-off Tabs Run-on and run-off tabs are to be designed with the following purpose : MUH. HIDAYAT ARIF  D311 12 003 23 1. To minimize the possibility of high-stress concentrations and base-metal and weld- metal cracking. 2. The result of welding can be neat 3. Stability of welding process can be maintained. Because run-on and run-off tabs will be to bind the both plates before continues welding joint Figure 6 : Run on and Run off Tabs 3. Cleanliness. All surfaces to be welded are to be free from moisture, grease, loose mill scale, excessive rust or paint. Primer coatings of ordinary thickness, thin coatings of linseed oil, or equivalent coatings may be used, provided it is demonstrated that their use has no adverse effect in the production of satisfactory welds. Slag and scale are to be removed not only from the edges to be welded but also from each pass or layer before the deposition of subsequent passes or layers. Weld joints prepared by 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. Compliance with these cleanliness requirements is of prime importance in the welding of higher-strength steels, especially those which are quenched and tempered.

4. Tack Weld

Tack weld is similar with intermitten welding. The fungtion of tack weld is to position and to lock with temporary two plates before joint with continues welding. The several requirement for tack weld process are : 1. To made with the same grade of filler metal 2. To need be removed, if after examination to be thoroughly clean and free from crack or other crack. MUH. HIDAYAT ARIF  D311 12 003 24 3. 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.

3.1.2 Production Welding Especially Preheat Process

Preheat is giving heat before welding process plates. In all cases, preheat and interpass temperature control are to be sufficient to maintain dry surfaces and minimize the possibility of the formation of fractures. The preheat requirements is : 1. When welding is performed under high humidity conditions or when the temperature of steel is below 0°C 32°F, the base metal is to be preheated to at least 16°C 60°F or temperature appropriate to the alloy and the thickness, whichever is higher. 2. When preheat is used, the preheat and interpass temperatures are to be in accordance with the accepted welding procedure and to the satisfaction of the Surveyor.

3.2 DEAD SHIP AND BLACKOUT