Vibration Measurements
Vibration Measurements
(OP)
A manufacturer I work with took some measurements of a piece of equipment at the bearings/housing and the supporting framing levels.....and sent them to me to because he wants the framing addressed. (Apparently some support framing was altered during the shut down (on the 4th) and nobody checked it out for vibration.)
Aside from fixing that, one question he has for me is: can I give him an idea as to how unbalanced the machinery currently is? About the only way I know how to do that (aside from bringing in someone who balances machinery for a living) is to model the situation, take a guess at the unbalanced force, and adjust that force to match the measured amplitudes (i.e. data they provided).
But is there a way to answer his question based on the data alone? (Which I could back check once the modeling is done.) I would think that the measurements taken at the housing/bearing level would be magnified by the fact the support is now shaking so badly.
Aside from fixing that, one question he has for me is: can I give him an idea as to how unbalanced the machinery currently is? About the only way I know how to do that (aside from bringing in someone who balances machinery for a living) is to model the situation, take a guess at the unbalanced force, and adjust that force to match the measured amplitudes (i.e. data they provided).
But is there a way to answer his question based on the data alone? (Which I could back check once the modeling is done.) I would think that the measurements taken at the housing/bearing level would be magnified by the fact the support is now shaking so badly.





RE: Vibration Measurements
If the machine is operating in the stiffness controlled area of the frame then then you could use an estimated frame stiffness
If, as is most likely, you think a resonance is involved then you need to know the damping, is not available which from a single speed measurement'
Bash it with a hammer (even without a load cell) and record the vibration.
Hopefully Walt will chime in.
Cheers
Greg Locock
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RE: Vibration Measurements
That is interesting, and certainly suspicious, but may not be the whole story. The modifications may have altered alignment as well as stiffness, and maybe some other things I can't think of right now.
The fact that the machine speed was also increased 20% as part of the modifications may be yet to be revealed.
Are there any vibration measurements pre-modification?
Does the vibration data include amplitude, frequency, and phase?
RE: Vibration Measurements
Yep.
I asked that question about a hundred times myself......they swear they didn't change a thing with the machine. (And honestly, looking at the steel shop drawings (for the new framing), I think I believe them.)
The answer to all your questions is: yes. But their point on that was that the data is very old.....ergo, they want an update.
RE: Vibration Measurements
Are those drawings something you could share with your old buddies here on Eng-Tips ?
Along with some indication what was removed ?
===============
1X phase from Volume 1(The early days) vs 1X phase from today might offer a talking point.
http://lampx.tugraz.at/~hadley/ss1/appendix/resona...
RE: Vibration Measurements
I don't think I should risk it.....I have a NDA with these guys. (And they are adamant about even their name being mentioned.)
They basically took out some support beams (under a couple of the skids)....and put in something more shallow. (For the purpose of running some new pipe in a tight space.) I've seen the calcs on the new framing.....it checks out, but they ran numbers for the static loads only.
I appreciate everyone's comments. I think (for now) I'll just go with my original idea of modeling the situation and adjusting the force to match the measurements. (Then working back to figure the unbalance.)
RE: Vibration Measurements
Best regards,
Jason
RE: Vibration Measurements
True.....but this being something supported on a (elevated) steel frame.....I don't think the level of damping is any big mystery. (I.e. we are talking about 2%.)
I think I may suggest that.....but since it would mean extra dollars, I doubt they will approve.
RE: Vibration Measurements
This paper may be a useful reference: https://sem.org/wp-content/uploads/2016/01/sem.org-IMAC-XVII-17th-173805-The-Identification-Rotor-Unbalance-from-Measured-Foundation-Response.pdf
Best regards,
Jason
RE: Vibration Measurements