13 NDT in one sitting · 8 min
Five methods, one percent of the paper
Visual is your method. The others exist so you know when to call them.
| Method | Sees | Misses / limits |
|---|---|---|
| VT visual | Surface: profile, undercut, porosity, cracks you can resolve, size | Subsurface anything; needs light, access, clean weld |
| MT magnetic particle | Surface and slightly subsurface cracks in ferromagnetic steel | Non-ferrous; needs magnetization and particles |
| PT liquid penetrant | Surface-breaking on metals (and more) | Nothing subsurface; dirty or coated surfaces lie |
| UT ultrasonic | Volumetric, thickness, fusion, many cracks | Needs a qualified tech; geometry and austenitics are hard |
| RT radiography | Volumetric: slag, porosity, some lack of fusion if aligned | Safety, access both sides or source side; tight planar cracks can hide |
W59 does not send every fillet to RT. The engineer specifies extra NDT. Your closed-book job is to pick the method that can actually find the discontinuity in the question. A buried slag line is not a penetrant problem. A toe crack is not a job for RT as the first thought.