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I have a industrial Hyd. application using a 100vg hyd fluid. The recent analysis shows Nitration (3). There isn't a accumulator in this system. I am confused how we would be seeing Nitration. Also, the UC is stating level 4. The system shows severe varnish but the lube analysis shows the hyd fluid health is normal beside the two issues noted above?? No contaminant elements in the Spectro analysis and the Vg is within tolerance.
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Dear Jim,

Detecting varnish problem is difficult.
UC showing level 4 is indicating that you are in marginal area.
and you also noted there that severe varnish was observed.
I am advising you to compare with other parameter i.e:
> Oil color (ASTM 1500), if it is more than 5, it is a warning
> You can try also to check the varnish rating (
> Also combine your analysis with the trending of Oil Filter Delta Pressure (DP). The increase in DP from 0.3 bar to 1 bar, for less than 6 months is indicating something wrong in the oil.

Normal or Abnormal is your decission, because you know better your equipment.
The lab just analyzing the oil test result from the available parameter.

Dear Jim,

UC level 4 is marginal (begining of alert)
I am advising you to combine with other analysis i.e:
* ASTM 1500 Color code. If it is more than 5, varnish buildup shall be considered
* Varnish Potential Analysis (
* and combine also with system monitoring data, like the trend of oil filter delta pressure (DP). the increase of DP from 0.3 reach to 1 bar below 6 months is indicating something wrong in the oil.

Normal or not is your decission.
The lab is just analyzing the available parameter.


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