Hi all,
I'm trying to understand the difference between two leakage test performed in underwater vehicle design.
The first: external overpressure water test
This test is performed with the vehicle inserted into a tank pressurized with water (at the maximum design pressure). verification of tightness is performed measuring the umidity level inside the vehicle.

The second: internal helium vacuum test
normal procedure according to varios regulamentation (EN 1779 for example).

I think that the first test is a tightness test with maximum design deformation (and so it is also a robustness test)
The second is a real leakage test.

And another consideration/question: if I apply the same pressure difference beetween the inner side and the outer side of the vehicle (with external overpressure or internal underpressure) the vehicle structural deformation is the same. Is it correct?

Thanks in advance for your answers