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SOLUTIONS: Evaluation of welds

After welding

Visual inspection after welding has been completed is also useful in evaluating quality, even if ultrasonic, radiographic, or other methods are to be employed. As welding progresses, surface flaws such as cracks, porosity, and unfilled craters can be detected, leading to repairs or rejection of the work. There is no point in submitting an obvious bad weld to sophisticated inspection methods.

Underwelding is a violation of specification and can not be tolerated.

Dimensional variations from tolerances, warping, and faults in appearance are detected visually at this stage. The extent and continuity of the weld, its size, and the length of segments in intermittent welds can be readily measured or recorded. Welds must be cleaned from slag to make inspection for surface flaws possible. A 10x magnifying glass is helpful in detecting fine cracks and other faults. Shot blasting should not be used prior to examination, since the peening action may seal fine cracks and make them invisible. The objective of visual inspection at this stage is not only to detect non permissible faults, but also to give clues as to what may be wrong in the entire repair /fabrication process. If the inspector has a sound knowledge of welding, he can read much from what he sees. Thus, the presence of excessive porosity and slag inclusions may be an indication of insufficient current even if the dial readings on the machine tell otherwise. Subsequent tests will also give clues to faults in equipment or procedures, but the information acquired through visual examination allows corrections to be made before results from more sophisticated methods become available.

Overwelding is costly and serves no useful purpose. It only makes the construction stiffer and heavier.

2.10

A-measurement Leg length

Leg length

The designer has specified a weld size and this should be observed. For filled joints it is also important that the leg lengths are equal.

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