turbine oil justification for bleed & feed based on RBOT,TAN

Before I would go to a feed and bleed I would do some additional testing. RBOT (RPVOT) is a older test methodology that has been shown to have considerable data scatter. I would contact your lab and have them perform a varnish potential test, either a RULER test or a complete turbine oil quality test. I would also run an extensive test slate on some unused oil for a baseline comparison. Look at any of the major lab websites for more details. Oil is way too expensive to dispose of without being very solid with your analysis.

quote:

Originally posted by mas.rif:
Dear All

Could any body share the interpretation for this result of oil analysis:
Mobil Oil DTE Ligth
RBOT new oil 688 min,RBOT used oil 156 min.
TAN used oil 0.22 mg KOH/gr
viscosity index new oil 102, used oil 98
Some ref. from this forum state RBOT under 25% should replace the oil.

Does any body, has some reference on best practice how to bleed and feed turbine oil.

Thank you

rif

Regarding the remaining oxidation stability reserve it seems that your oil is near the end of service life.

Based on the original RBOT level, it is more likely that your oil is a Group1+ or Group2 oil. If this is the case, than your initial AN could have been below 0.1 (too bad you didn’t mention it), and current 0.22 is another indication that antioxidant is pretty much used up.

Elemental spectroscopy analysis is a good tool to verify how this elevated AN affect the equipment corrosion wise (e.g. leaching copper, aluminum, etc.). Also, it would show the remaining amount of zinc and phosphorus (metallic base of R&O additives), unless your additive package is an ashless type, and will show contaminants in oil (except water).

Better assessment of your oil could be made if you reported what is the application, original and actual viscosity (rather than VI) cleanliness of the oil, moisture content, and years of oil being in service.

Bleed & feed approach is a temporary fix to give you some time (year or two) to schedule oil replacement and set all logistics needed for such action to avoid costly unscheduled downtime, because by adding some new oil to the existing oil, you will still have higher AN than the new oil, as well as wear and other contaminants remaining in the system, some of which may act as catalysts to more rapidly deteriorate additives added via bleed&feed approach.

Thank you very much for all your responses.

@rgf12
RBOT (RPVOT) this is the one we could do by local lab.
I've try to find out local lab that could test the RULER

@michael
This DTE Light used for steam turbine unit 55 MW.

New Oil Data
TAN : 0.09 mgKOH/gr
Zinc: 3 ppm
Silicon: 3 ppm
Sodium: 1 ppm
Calcium: 1 ppm

Used Oil Data
TAN: 0.22
Zinc: 6 ppm
Silicon: 4 ppm
Sodium: 4 ppm
Calcium: 3 ppm
Led : 2 ppm

Those data is shown on the last elemental lab analysis.
Could you please share your intepretatiion for those set of data?

It is true bleed & feed some time only give one to two year extension life, but in an economic view & as long as technical judgment can accept, we think we'll take this action first.

That is way I wish some body share an experience in bleed & feed


Once again thank you verymuch for any sharing for my case


regards

rif