Does anyone have any experience doing TBN test on compressor oils from NH3 systems? And if so, what would you recommend being abnormal compared to new oil? (-50% of new oil value?)

I don't think you would benefit from TBN on a ammonia compressor oil. They are typically straight mineral oils with no detergents or other additives to provide alkalinity.

I measure TAN on ammonia compressor oils (after stipping off the residual ammonia)and use the typical values for any other mineral based refrigeration lube for comparison (0.05 warning / 0.10 action levels). It always amazes me when the oil has acid present in a highly alkaline ammonia environment, but the TAN and wear metals do seem to move together.

That makes sense.

I did read about an oil analysis lab that offered TAN on all refrig oils, except ammonia systems were thy run TBN. (I dont remember who).

Just wondered if someone else used the same practice.

Thanks for your quick reply.

quote:

Originally posted by mr. Hughes:
.... what would you recommend being abnormal compared to new oil? (-50% of new oil value?)

For Trending of used Oil BN values use.
ASTM D974, 4739 & 5984-96

For Crankcase applications use -50%(of new oil BN) as the caution limit and -80%(of new oil BN) as the critical limit.

In the absence of any other indicators these should serve you satisfactorily.

There is some arguement for using Oxidisation by IR in place of TBN so this should be considered as an alternative.

happy hunting