Ok i understand.
On principle you have 2 possibilitys :
First : Dyn.calculation in design status
The difficulty is to estimate the dyn load,their location and their frequency for this phenomenon.
I think you can only take inaccurate assumption and varyation them.
On principle estimate the eigen frequencys from your pipe system.
Is the lowest eigen frequency ca. >3 - 5 Hz , then i think do have not a big dyn. problem.
If yore have lower eigen frequencys, then ellimated them with more supports.
But calculated the thermal stress !
2. Me hint from my last contribution
Recards,
Ernst Ohliger