The Acid Number (AN) measurement detects both weak organic acids and strong inorganic acids.
Fluctuations in the acid concentration of an oil can originate from sources such as:
- Oxidation by-products.
- Acidic contaminants.
- Incorrect oil or additives.
Acid Number is an excellent diagnostic and predictive test for:
- Hydraulics
- Gearboxes
- Compressors
- Natural Gas Engines
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How is the Acid Number calculated?
The acid Number (AN) is measured and quantified by the weight in
milligrams of potassium hydroxide (KOH) required to neutralize all the acidic constituents
in one gram of lubricating oil. Also known as Neutralization Number. (Previously known as Total Acid Number (TAN))
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Carefully and systematically monitoring the acid number is an advanced and effective method of oil analysis when properly applied. Knowledge of how the
acid number is calculated and what variances exist will help in interpreting the results. AN tests are typically conducted to
obtain an accurate indication of additive depletion or acidic infiltration.
Trending is the best way to monitor an abnormal increase in the acid number.
Regular testing will provide the necessary data to formulate the most identifiable trends occuring within the lubricating system.
An elevated acid number can result in:
- Component corrosion, more severe if water is present.
- Deposits of tars and lacquers on metal surfaces.
- Increased viscosity resulting in pumping losses.
- A gradual increase in the rate of AN elevation.
- Greater potential for varnish formation.
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