A close call indeed! It does go to demonstrate the need for the right type of NDT. The dye penetrant method is a simple one but has limitations. Must be done correctly and the position/ size/ critical nature of use of the tested component all limit the use. When in a steelworks I was detailed with testing some rolls used in the mill. It involved dye penetrant tests on corners of the drive tangs, whilst the rolls were still on a lathe prior to use. A big lathe! It was a quick check at high stress points but we pointed out the limitations. One roll had failed in the area we tested and that instigated pre use tests. I never had suspicions of cracks in all the tests I did nor any failures in use. A mate worked for an NDT company and he was sent to test oil storage tanks ( huge buggers) at a refinery where a fire had occurred. He was X- ray testing all the welded joints in the tank skins, signing off each X-ray taken.
