Hi
in a gas turbine the RBOT value,decreases to 5o min but the TAN was not change during the last year and its max. value is 0.2mgr/gKOH.
i want to know how can i interpret it
thanks
laleh
Original Post
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RBOT is kinda a physical test in that it stresses the oil sometimes much MORE that the current operating system oil that is being tested. As such you can have a low RBOT in a system and still show a low TAN.
I would keep an eye on TAN aswell as other precursors for varnish formation I"m not totally up to date on what tests are best I would check with Herguth labs in CA. they have a large data base and can tell what tests will be best in your situation.
bruce
I would keep an eye on TAN aswell as other precursors for varnish formation I"m not totally up to date on what tests are best I would check with Herguth labs in CA. they have a large data base and can tell what tests will be best in your situation.
bruce
You will find that most OEMs set a limit on the RPVOT or RBOT to 25% of new oil as the condemning limit. 50 mins on RPVOT seems very low particularly for a gas turbine oil. The TAN on the other hand looks at the oxidation by products that have converted to weak organic acids, therefore, it only evaluates this by product and nothing else. You should consult ASTM D4378 in service monitoring of turbine oils for steam and gas turbines.
The precursors of varnish are a complex myriad of oxidation by products and does not necessarily show up in the TAN.
Speak to the lab about performing a varnishing index potential on the oil as well.
The precursors of varnish are a complex myriad of oxidation by products and does not necessarily show up in the TAN.
Speak to the lab about performing a varnishing index potential on the oil as well.
Dear Laleh
If you have a low value of RBOT (RPVOT in the new denomination), that means, that your oil doesn't have too much corrosion inhibitors. This means that the TAN will increase quickly, because your oil has lost "its defenses" against the oxidation process.
As ReneWa comments, I will sugest to perform a Varnish Potential Rating Test, and it could be preferible to perform a Flushing in your system, and to change the Oil.
If you have 50 mins of RPVOT, maybe you are using a Group I Mineral Oil. I recommend to use a Group II or III Hydrocracked Oil.
I hope my comments help to you,
Sincerely,
Cristián Schmid
If you have a low value of RBOT (RPVOT in the new denomination), that means, that your oil doesn't have too much corrosion inhibitors. This means that the TAN will increase quickly, because your oil has lost "its defenses" against the oxidation process.
As ReneWa comments, I will sugest to perform a Varnish Potential Rating Test, and it could be preferible to perform a Flushing in your system, and to change the Oil.
If you have 50 mins of RPVOT, maybe you are using a Group I Mineral Oil. I recommend to use a Group II or III Hydrocracked Oil.
I hope my comments help to you,
Sincerely,
Cristián Schmid
Dear Schmid
thanks for your coments.we flush the systems and sustitute it with new brand oil,as you recomended.but as you said we should see the quick increase in TAN,but we didn't increase on it and my question was about it?why i had no increase in TAN?
on your sugestion i do some test on varnish.
Sincerely
thanks for your coments.we flush the systems and sustitute it with new brand oil,as you recomended.but as you said we should see the quick increase in TAN,but we didn't increase on it and my question was about it?why i had no increase in TAN?
on your sugestion i do some test on varnish.
Sincerely
For new turbine oils RBOT values are generally ~500 for gp 1 type and around 1000+ mins for gp 11.
Hence regardless of base oil 50 mins is a bad number.
TAN not generally related to RBOT numbers.
Would be worrying about varnish at this stage and carrying out different tests, but feel that an oil change and flush is inevitable.
Hence regardless of base oil 50 mins is a bad number.
TAN not generally related to RBOT numbers.
Would be worrying about varnish at this stage and carrying out different tests, but feel that an oil change and flush is inevitable.
