Hello, We installed a rebuilt electric motor and performed a solo run test after it had found it's mag center. We had a report of .1 IPS is threshold of acceptable this measures .235 IPS of 1 x unacceptable. The bolting was is tight to the motor and foundation to grout, We then pulled together the group went out and retested our reading were acceptable good condition. Could rotor sag caused the first bad reading? Unit has proximity probes we will tie equipment into them for further evaluation. Has anyone come across this before?

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If some kind of rotor asymmetry is causing vibration oscillation of at pole pass frequency during solo run, vibration will vary very very very slowly (pole pass period might be 30 minutes).

 Rotor asymmetry could include a static bow or a dynamic bow (operating near flexible rotor resonance) or excess bearing clearance or (less likely) rotor bar problem.  

by the way, we don't know anything about your machine (horizontal/vertical, bearing type, which direction was 1x measured).

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HACKATHON in association with IMC-2019

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