Inspection of the Crossed Areas of Welds Joining Hull Sections by Time-of-Flight Diffraction Technique

A special TOFD inspection procedure has been designed to cover the blind testing zone due to the weld reinforcement height when testing the crossed areas of longitudinal and transverse welds joining hull sections.It uses TOFD probe pairs scanning along two 45°angled paths towards the welds direction.In order to eliminate measurement error brought by angled scanning,several formulae have been derived to compute the corrected values for defects length and depth.Using the designed procedure,46 crossed areas have been inspected successfully on the 180 kiloton cargo vessel.After comparing the TOFD results to radiographic testing,the TOFD inspection procedure validation has been demonstrated,which could satisfy the requirement of testing crossed areas of welds.