20. Nondestructive Testing

Welding being a process of joining, the end user would like to assure himself of the quality of the joint that has been achieved though welding. There should be some mechanism which will give assurance to this aspect of no-defect in the welded joint. Hence the necessity of non-destructive testing (NDT). Through this the welded joints are inspected to determine the presence of any flaw, its type, extent and its location, such that, if it qualifies to be an unacceptable flaw, i.e. a defect, then necessary remedial measures could be undertaken to eliminate the defect. Thus it will ensure that the structural component is free from any welding defect. Various standards have been worked out by various regulatory authorities. The non-destructive testing (NDT) is carried out to verify compliance to the standards by suitable methods of examination of the surface and subsurface of the welded joint. The NDT methods that are commonly used to examine finished welds in shipbuilding are: visual, dye penetrant, magnetic particle, radiographic and ultra-sonic testing.