Welding sequence

Welding course

MarineTypewritten textMATERI SOSIALISASI DAN PELATIHAN WELDING INSPECTORBAGI MAHASISWA TEKNIK SISTEM PERKAPALANTAHUN 2013

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Learning objectives

After this lesson, you will be able to:

- easier observe if wrong welding sequences are used.

- evaluate welding sequences of some common welded connections.

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Useful information

Information on NB and repairs regarding welding, minimum weld length and other limitations are to be found in

the IACS Guide No.47 SHIPBUILDING AND REPAIR QUALITY STANDARD

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Why welding sequences?

Why should we consider the welding sequences?

Welding creates stresses in the structure and shrinkage occur.

Use of correct welding sequences may decrease the stress level in the structure.

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Stress levels

You may have seen what happens when you are welding two plates together.

Use of back step technique give smaller distortions.

Welding straighton gives a lotof distortions.

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Welding of erection joints

Deck, double-bottom, bottom and skin may be welded in the above mentioned sequences.

Welding sequences are used in order to transfer the high stress peaks in the structure to a free end.

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1. Completely fill up weld no.1

2. Continue with the vertical no.2and finish it before welding thehorizontal part of joint no.2

3. Clean the joint in the crosses4. Weld joint no.3 starts at least

150mm away from the crossingweld.

This will prevent increased stress levels in the weld.

Erroneous Openings - Welding sequences

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Inserts

Shrinkage of the weld will open up the joint at the opposite side

Since the insert plate has moved with free ends, the welds are without high stress levels.

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Inserts of sheets

First weld the ends of the sheet from centre to the edge.

Then weld the full length.

Back step technique may prevent the stress level to increase too much.

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Welding of Block Joints

Which one to be welded first?1. Butt weld of sections

2. Butt weld of stiffener

and finally

3. Fillet weld of stiffener

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Conclusion

Correct welding sequences helpto avoid distortions.

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