Class 5 Boiler Practice Exam

Which non-destructive examination method is most effective for revealing lack of fusion in a finished weld?

1. Visual testing

2. Magnetic particle testing

3. Radiography

4. Ultrasonic testing

The correct answer is: Radiography

Radiography is highly effective for identifying issues such as lack of fusion in finished welds because it utilizes X-rays or gamma rays to penetrate the material and reveal internal flaws. When this method is employed, it produces an image on a photographic film or a digital detector that allows the inspector to see the internal structure of the weld and the base material. Lack of fusion, which occurs when weld metal does not properly bond with the base metal or other weld metal, can generate images that clearly show the presence of voids or incomplete penetration within the weld. This makes radiography a critical tool in maintaining the integrity of welds in various structures and ensuring compliance with safety standards. Visual testing may be useful for detecting surface defects, but it might not reveal internal issues like lack of fusion. Magnetic particle testing is effective for detecting surface and near-surface discontinuities in ferromagnetic materials, while ultrasonic testing is excellent for assessing the thickness of materials and identifying internal flaws; however, it requires a level of skill to interpret the results accurately for detecting lack of fusion. Nonetheless, among these options, radiography stands out as the most capable method for revealing such internal welding defects.