Minimal pipe size for stress analysis

Hi to all,

I would like to ask is there minimal pipe size above which the stress analysis is necessary.
The problem is about lines for hydrogen measurement equipment in the nuclear PWR containment building. The lines are 6 mm diameter and 1 mm wall thickness. The fluid is air with ambient temperature and the pressure is little below the atmospheric pressure. The question is - Is there a reason for stress analysis for this type of lines?

In my experience of recent nuclear work in the UK, anything that is round, with a hole down the middle and is not scaffolding, requires a stress calc. Not just static but response spectra dynamics too.

Some very small lines are critical to plant operation and need to be designed accordingly.

Thank you for the quick response!