Abnormal noise from Pressure Vessel with Internals

[ww2i]

We have been experiencing an abnormal noice from a pressure vessel having heavy internals.
Vane system exists inside and the vessel is of a knockout function.
What can be the probable causes? How best should we judge this not to end up opening to find nothing inside was actually abnormal?

[octane]

First thing first, have you checked the history of the equipment to have any idea what the noise could be coming from?
That may provide you with some clear indicators.

[arcpro]

Just check if such sound has already been reported before (operators may confirm you this), and after that was there any internal inspection performed with any findings?
This would provide you some confidence.
The most common cause would be an internal component vibration which may include loose vane pack supports, broken hold-down clips, loose demister pad retaining grids, internal baffles vibrating due to gas flow, fatigue cracking of support members.
Associated typical sound type would help as well. It should be like rattling, metallic knocking, intermittent banging, noise intensity changes with flow,
You can have an indication as well where noise often increases at specific flowrates and disappears when flow is reduced.

[irish]

The sound type itself can help.
Check if that is not rattling or metallic and instead humming, whistling or a low-frequency one.
This can be due to some high gas velocity passing through vane opening, support beams, nozzles.
And you may end up finding that nothing is mechanically damaged.

[sys1]

If you do not sort anything out where the noise disappears as well for some time, instead there is an increase, take an opportunity, ask for that.
With support from operations, you need to have a closer observation to look for:
Noise increasing with time
Measurable shell vibration increase
Sudden onset after a process upset
DP changes across internals
Separation performance deterioration
Evidence of loose internal supports from vibration analysis
Metallic impact sounds rather than aerodynamic noise

[ww2i]

I appreciate all your inputs guys.
We are in contact with our Inspection teams as we see that noise does not increase and does not stay the same.
Based upon the type of sound, we believe it is not metallic and there is this gas only causing the noise.
Yes, operators confirm they heard such noise previously as well!