good day

this about vertical pump which tripped due to high vibration. Pump speed 745 rpm. During the cost down the vibration cascaded spectrum was at 740 cpm at every speed till zero. What does this indicate ??? Is natural freq or something else.

Thanks

Original Post

Based on what you have said, I would suspect a resonance which you could confirm with a bump test.  In the interim I would be looking for something that might have significantly changed the mounting base stiffness.   That could be something as simple as loose bolts to something as complex as a cracked weld.  But since mass hasn’t likely changed then you have to look at a stiffness change that has caused the resonance to likely shift downward.   Check piping supports as well.  Basically look at the entire system; if something exists to position and hold something rigidly, check it to make sure it is doing its job.

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