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Reply to "Marine Diesel generator High vibration in Axial direction at Engine Free End"

Greetings Mr. OLI

Pleased to see your interests and quick response.

1. So did you check if the compression is about the same on pads on the 3 motors?

Ans: There is no issue of the resilient mounts as the Alternator end/Engine end radial vibrations appearing in limit.

2. Just to check from what you can see on pictures, there are no obvious problem anyway.
So if it end up a gear problem? I had a similar problem on a Mitsubishi last year in 1 unit on a brand new set of dieselgens for a hospital and I could estimate what gear that was the problem as it was not that bad so I got FFT data to look at.
Final it was the old test to have a look at the oil, we just pulled the dipstick and took a look at a clean cloth and it was no argument, real disaster metal particles all over and relative large. You can also listen to it with a screwdriver to your ear protector, it should sound like a disaster......

Ans: Gear problem in FFT not significant and gear mesh amplitudes are not considerable. 5Hz/300 rpm  most probably resonance is the issue due to various reasons.

As you see the cleanliness of DG areas and the operation doesn't show any serious problems and engines are running satisfactory.

Marine Engineers are capable of handling normal issues, being myself Ex marine Engineer and Technical superintendent, physically not in a position to justify any problem with this AXIAL vibration.

Lube oil, No doubt an issue, however, marine engineers normally take care of Lube oil issues.

I did not see serious issue during operation, however, alarming is the Axial vibration, Thrust bearing issues, Crankshaft deflections, Main bearing issues, coupling issues and alignment issues.

Out of 3 Diesel generators one DG is serious, No2 DG is above IACS limits and No3 DG is satisfactory.

Looking all above, I asked the Company managers to have extensive search about thrust bearings, Gear train, Shaft deflections, Main and Connecting rod bearings, Piston cooling issues to verify and looking forward hearing from them.


Chary Tatta