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Today we have encountered a shaft vibration issue in a high speed gearbox for STG application, wherein the pinion shaft speed is 11200 RPM. We have encountered with drive end vibration upto 3 mils, both transient speed data and steady state data checked and found that the vibrations are increasing with speed, nbalance in the pinion shaft checked and found OK. The coupling runout measured and found 0.25 mm.

Kindly, study the case and let me have your views on the effect of the runout on the vibration and what is the permissible limit.





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Shaft vibrations
Tags: GB

the run out of coupling that you mean is on coupling hub ? if 0.25mm is on coupling hub (normally, it should be not over 0.05mm), it is too much run out and able to make unbalance at drive end? you should check at some points along with coupling hub to define it is eccentricity or shaft bow.

You check unbalance in WS with or without coupling hub? what kind of coupling do you used?




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