1. The waveforms look very high amplitude and odd pattern (or lack thereof) and the analyzer/meter indicates overload. There are no high frequencies in the spectra, so the overload would have to be from much higher frequencies; from impacts. This is consistent with the fact that about 12" away the amplitude is much less; suggesting high frequency. The generator drive bevel gear is suspect for producing axial vibrations and worthy of a visual inspection.
ANS: Thanks for your assessment Mr. Walt Strong, Yes the gear train end is the issue, however, in a similar engine, other vessel, we requested for Gear train Inspection with makers service Engineers and reported that No gear train deficiencies found. Thrust bearing is another to check, Crank shaft deflections another important parameter.
At the alternator end the vibrations are found normal only Engine side Axial is high. here also we have requested Ship managers to check the gear train, shaft deflections, thrust bearings, Engine Resilient pads. Once the vessel come out with all details we will put the details here for case study observations.
2. The low frequency at 5 Hz is perhaps from propeller blade rate (if underway) or another machine or general resonance on the mounts. At 5 Hz the entire engine-generator should have about the same axial vibrations at both ends.
Ans: 5Hz I am finding many DG vibrations list. The point of 5Hz values at both ends to be verified. These engines are connected Alternators and no propeller issue other than alternator cooling fan.
Once again thanks for your professional interests and responding to this case studies. If you feel any additional data is required, I will try to workout at next vessel.
Nice clean engine room to work in!
Thanks and regards