Our turbine oil is already in its critical warning limit in terms RPVOT values and we are planning to sweeten up or adding anti-oxidants package as stop gap measure as per recommendation of our oil supplier, since we can't afford to a sudden outage since its not our scheduled maintenance. Also the oil is already 5 years in service and we observe some thick foaming of oil. Would appreciate If could get some sweetening procedure on turbine oils in general?

Ricardo,
Sweetening you oil with new, but compatible, turbine oil is your best solution; far better than adding additives to your oil. That way you can replenish other essential additives (i.e. foaming inhibitor), and improve viscosity. I don't know how you condition your oil, but I suspect a lot of wear particles and/or contaminants being present in oil, including moisture. I say this because every particle is a seed for air entrainment and foaming. From that point on, everything is spiraling downwards:
1. Air in oil working hard and persistent on oxidizing your oil
2. Copper and iron present in oil aid the oxidation process by catalyzing it
3. Oxidation inhibitor gets quicker used up by trying to prevent this oxidation (low RPVOT?)
4. Varnish starts flourishing (more seeds for air entrainment?)
5. Moisture (water) hydrolyzes polar additives (foaming agent?) and strips them from oil
6. All of this happening starts to affect viscosity, especially at spots of higher temp

Remedy: Try to keep your oil clean and dry, and it will last you much longer
Good luck!

Hi John,

Thanks for your valuable inputs I'm sure this would be of great help to our technical team.

More power to this forum.

Thanks and regards.

Ricardo