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TAN decrease in synthetic oil

A andjaMember
Hello,
We use hydraulic synthetic oil Quintolubric 888-46 for Hydraulic gun and drill in Blast furnace. Oil was put in the system in Decembar 2007. Tan value in January was 2,1mgKOH/gr, but in march decrease to 1,6mgKOH/gr. Last analysis showed 1,62mgKOH/gr. Saponification value is 162mgKOH/gr. There was no water ingress in the system, oil cleaness is good (6 according to NAS 1638). One reasone for this decrease could be mixing with mineral based oil, but is there any other reason for this decrease of TAN value? What happened to synthetic oil if some mineral oil is added to it? Thank you very much.
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E ehcguyLevel 2 - 51 to 100 posts
First before you take action check with the fluid supplier. The TAN of some products can drop as additives are used. Also, did you use the same lab each time because their can be variances. Plus, how do you know that there was no water ingress if you did not test for it? Do a Karl Fischer test. Also, did the viscosity or the SG change because they can shear down and these tests might also show mineral oil contamination as can a FTIR. Watch the results because these oils tend not to last as long as some other 'fire resistant' fluids like phosphate esters. In addition the reported saponification value is likely wrong because it was given as 162 mgKOH/gr. What is it now and what was it new? Quaker do not give it on their data sheet.

Ken
F fraduMember
Hi, in use TAN normally increases due to increase acid in the system .Quintolubric 888-46 TAN is < 2 when fresh. In use max TAN is 8.0 mgKOH/g. It should be either a mistake in the TAN calculation or you made additions with Q888-46 with SAP below 1.0

Do not confuse TAN with SAP. There is no need to test SAP. Replace the fluid when SAP>8.0 or water>2000ppm

Q888-46 does not contain S. It does nontain P. If you need in Maintenance Service management for Q888-68 let me know.
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