Hello, I am writing from Argentina..I am having some doubts regarding to TAN levels on the lubricant used on a marine gearbox.
The gearbox that I am talking about is an MAN AMG55EV, and really common gearbox in today's ships.
The oil used for this gearbox, as the manufacturer recommends is a SAE 30 "diesel engine oil". Actually we are using Shell Gadinia 30 as it is one of the recommended products in the manual of the equipment.
As this oil is made for engines, it has got initial TBN levels of 12, but as the system is a gearbox, when I do oil analysis I request for TAN.
Now, I am asking myself what happens when the TAN goes up, let's say to a value of 3.0.
Did TBN counteract the acid generated by oxidation of oil? In that case, when we change the oil, would be a good parameter to check the TBN apart from the TAN?
I am quite confused as you may see, all my life I have heard about alkaline reserve which give positive TBN value on engine oils, but as far as I am concerned gear/hydraulic oils haven't got this alkaline reserve...
Actually after running the oil for many hours probably (I haven't got an exact maintenance log from previous owner) we decided to change oil after getting a TAN value of 3.0.
I would be glad to hear your advice, what TAN value you think that would be good for this system, and which value would be critical. I think that it is good to remark that this equipment apart from gears, it has got a hydraulic system for the clutches and variable pitch propeller.
Thank you very much!!!
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