It is true that some support get lift off all the time in operation giving rise to flow induced vibration and we are blaming the operating load on recurrent weld failure, too, as to prevent vibration, we made piping excessively rigid in axial direction, without removing root cause.

Our operating temperatures are not always high enough to have full 100% relaxation in small duration.

Many times we face difficulty in explaining situations with code and doubt appears in mind! I will think over the problem afresh.

It is very difficult to assess as-built support stiffness and structural steel support elevations in successive supports at site which can give rise to lift off which can not be caught in alt sust cond
Loads.
Reg,
Sam