Recently I have attended an offshore oil rig site.
There was a main diesel engine EMD with an alternator in operation.
Engine make : EMD, 900 RPM
Alternator: Synchronous type- single bearing alternator, 2525Amp, 60 HZ, 600V, , 900 RPM,
1. Engine DE & NDE side vibrations were in range of 9 -10 mm/s rms
2. High axial vibrations on Alternator NDE side observed
H V A
DE 9.3 5.3 16.7
NDE 7.8 16.0 21.8
Spectrum: High peaks at 1X & 4X along with tiny 2X & 3X
(Attached for reference)
Phase relations : erratic. (Not constant at H,V,A)
We have ruled out possibility of misalignment as we have done laser shaft alignment, but still the vibrations are on higher side with same above.