Axial vibration on gear box and motor

[sancru98]

I have a motor driving a gearbox. I had DE bearing of the gearbox replaced recently as pitting in the inner race was found. Before re coupling the two units, I had the motor vibration checked and found to have satisfactory vibration levels in horizontal, vertical and axial directions. After the two were recoupled, I have done another vibration analysis and instead of improving the axial vibration, it made it worst. The axial displacement have increased...

Anyone seen this kind of problem?

 

[brewnog]

Yes.

Measure the phase angle between the motor and gearbox in all planes, and we may be able to diagnose a type of misalignment. Also look where the peaks appear in the frequency spectrum, let us know where these appear and what speed the unit runs at.

 

[sancru98]

The cpm is around 525 while the rpm is at 680.. how do you measure phase angle?

 

[brewnog]

Accelerometers on both components in the same plane, look at the frequencies of concern, and look at whether there's a lag between the two signals. If the axial signals are out of phase, you likely have an angular misalignment problem. If transverse/vertical signals are out of phase, you likely have a parallel misalignment problem.