Lack of Side Wall Fusion 

LOSWFLack of Side Wall Fusion is a welding defect caused by deficiencies in the welding process. When the weld material does not fuse with the parent plate at the side of the weld, a LOSWF defect is produced. Lack of fusion is caused by too little heat input, the travel speed of the welding electrode being too fast, a poor welding technique, restricted access to the joint or an unclean base metal.

The LOSWF defect is generally a planar defect and it will be smooth on the parent plate side because this is the original welding preparation. On the weld side it could be smooth or rough. As a LOSWF can be an embedded defect, the best method of detection is by ultrasonics. BS EN ISO 17640:2010 ‘Non-destructive testing of welds – Ultrasonic testing’ requires that one of the probe angles used shall ensure that the weld fusion faces are examined at, or as near as possible to, normal incidence. This requirement maximises the ultrasonic signal that would be produced by a LOSWF defect.

LOSWF defects can have small gapes and so, to maximise the chance of detection by radiography, the radiation beam should be directed down the angle of the fusion face.

For more information on LOSWF see:

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