Thanks guys, I found ISO 8528-9 which ISO covers 8528-9 Reciprocating internal combustion engine driven alternating current generating sets -- Part 9: Measurement and evaluation of mechanical vibrations.
I have done further investigations and it seems the vibrations is coming from 1800 rpm part of the gear. ( 30hz )
The gear has now been opened at some level and it doesn´t look good but they haven´t yet found what was the couse of the vibration.
ISO 10816 is now 20816 I am told.
I can put frequency marker on spectrum but it is quite limited software when it comes to analysis. ( no orders or bearing data )
Thanks a lot for you replies.