HSE has investigated a number of instances where the NDT has been falsified, mainly at the fabrication stage. Welds have not been thoroughly tested and/or the results have been misrepresented.
Metallic structures fabricated by welding are prone to defects, such as inclusions, porosities and cracking. The absence of significant defects is assured, at the construction phase, by NDT of the welded joints.
Source: HSE