Aerodynamically induced forces 1

[raphatss]

Hello everyone,
Recently I've experienced some problems with a centrifugal compressor presenting subsynchonous vibration due to aerodynamically induced forces, most probably diffuser rotating stall.

The vibration starts at low flows, but within the operational range. Amplitude is not reaching alarm level, but I wonder if the values will remain the same or increase with time.

Has anyone here faced this kind of problem?

Some people have said that it would be better to reduce the operational range by moving the surge control line to a higher flow, avoiding the inception of the rotating stall. Others argue that the forces and vibration are not so severe, and the equipment can operate at low flows without worries.

Would like to hear your opinions/experiences…

Thanks in advance.

 

[DLite30]

Which direction is the increased vibration in--radial or axial? What % speed is it running when this happens?
What % of run-time does it operate in this condition?

You can certainly try opening the surge valve a bit, to see if that would have any effect, good, bad, or none, but at the expense of energy usage.

If it were my machine, and it hadn't exceeded an alarm point while running or upon start up or shutdown, I wouldn't be too concerned. I would just watch it and see what it does over time.

 

[raphatss]

Thank you DLiteE30 for your post.
The vibration is in radial direction, 6-8% of speed.
It's a new plant and at this time the equipment is not running, so I don't have the % of run-time in this condition.
I think that, as you said, the best thing to do is watch it and see what will happen.