For a structure like a crane, is it ever a designed
fitness-for-purpose / planned Non-Destructive Examination technique to
make it entirely from Structural Hollow Section, fully-sealed
(eg. ends blanked-off), so that the voids can be pressurised through a
valve, with cracks detected by leaks?
Immersed in water to see bubbles; watch for pressure fall over time;
I was thinking of this for a structure I was sketching and designing,
to prove it has no through-thickness cracks anywhere.
What it lacked in not detecting cracks before they become
full-thickness, it would gain from testing the entire structure 100%,
not requiring any preparation (surface or otherwise), no sensitivity
to testing orientation of flaws / defects which do exist (like
dye-pen, but unlike mag-part) - and cheap so you could test often /
before any critical use.