TAN and TBN Explanation

MolaKule

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Originally Posted by SpectroScientific
Background TOTAL ACID NUMBER A high concentration of acidic compounds in a lubricant can lead to corrosion of machine parts and clogged oil filters due to the formation of varnish and sludge. When a lubricant breaks down, acidic by-products will be formed from the chemical decomposition of the base stock and additives in the presence of air and heat. Total Acid Number (TAN) is a measure of acid concentration present in a lubricant. The acid concentration of a lubricant depends on the presence of additive package, acidic contamination, and oxidation by-products. Occasionally, the depletion of an additive package may cause an initial decrease in TAN of fresh oil. However, the accumulation of oxidation by-products and acidic contaminants in an oil over time will always lead to an increase in TAN. This test is most meaningful in industrial machinery applications although sometimes it is recommended in engine applications along with Total Base Number (TBN). TOTAL BASE NUMBER Total Base Number (TBN) is a measure of alkaline concentration present in a lubricant. Engine oils are formulated with alkaline additives in order to combat the build-up of acids in a lubricant as it breaks down. The TBN level in a lubricant is targeted for its application. Gasoline engine oils are typically formulated with starting TBN around 5-10 mg KOH/g whereas diesel engine oils tend to be higher (15-30 mg KOH/g) due to the more severe operating conditions. Specialized applications, such as marine engines, may require >30 mg KOH/g. As the oil remains in service, this BN additive is depleted. Once the alkaline additives are depleted beyond a certain limit the lubricant no longer performs its function, and the engine is at risk of corrosion, sludge, and varnish. At this point it is necessary to top-off or change the oil...
See TAN and TBN Instrumentation and more info here: http://cdn2.hubspot.net/hubfs/857680/WP_MeasuringTANandTBN_in_Oil_final.pdf
 
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Do you know what method of measuring TAN & TBN that the popular motor oil analysis labs use? Interesting read. Thanks for sharing.
 
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Don't some esters naturally have some higher TAN from the start, which would be misleading in some analysis on VOA's? I remember Terry Dyson mentioning that on VOA's for Renewable Lube oils.
 
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Originally Posted by BHopkins
Do you know what method of measuring TAN & TBN that the popular motor oil analysis labs use? Interesting read. Thanks for sharing.
https://www.ccjdigital.com/partner-...ng-tbn-in-modern-heavy-duty-engine-oils/ Labs typically test under ASTM D4739
Originally Posted by UG_Passat
Don't some esters naturally have some higher TAN from the start, which would be misleading in some analysis on VOA's? I remember Terry Dyson mentioning that on VOA's for Renewable Lube oils.
Yes, if present, they will increase your TAN
 

MolaKule

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Originally Posted by UG_Passat
Don't some esters naturally have some higher TAN from the start, which would be misleading in some analysis on VOA's? I remember Terry Dyson mentioning that on VOA's for Renewable Lube oils.
Brian is correct, but it is not misleading, you have to simply adjust your UOA interpretation to accommodate any potential ester component. This is why I keep telling people that without a current VOA of the oil you have put into the engine, any subsequent UOA interpretation is pretty much useless.
 
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People tend to use Blackstone and they nickel and dime you for TBN and TAN tests. I've had blackstone question a Renewable Lubes VOA as being a UOA instead, due to the initial TAN of the esters.
 

MolaKule

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Amanda from Blackstone states that the TAN testing is based on ASTM D664 and the TBN testing is based on ASTM D4739.
 
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whereas diesel engine oils tend to be higher (15-30 mg KOH/g) due to the more severe operating conditions. This must refer to heavy duty diesel engines only. Most modern European passenger car diesels require ACEA C2/3/5 and the TBNs are no different from petrol engines - typically between 6 and 8 - never seen a Cx oil with more than 10. Question for the experts - do the dispersents, detergents etc contribute to the TBN ?
 
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