Durga,

Vendor does not say "if pipe is rigid".
Vendor says " Vibration (If any)--> than announce me".

You would say "we made stiff supports around and piping arrangement around is quite rigid, vibration is not an concern".

Or you would say "we've been obliged to put there spring supports, arrangement is not stiff, is possible to have vibrations due to [...] and the parameters of vibration are [...]".
In this case you must fill in the [...] fields- that's all.
How? Here is your engineering contribution.

Sometimes is "not simple". They are cases when vibrations can be self-excited - associated with flow hydrodynamic instabilities (the system vibrates under no periodical external forces) and you cannot be 100% sure the system vibrates or not unless you have references on similar cases, anyway (IMO) you cannot describe accurately such vibrations by math.

I think you have enough elements to take a decision which is your way.