Downloaded from https://www.everyspec.com ADS-79D-HDBK particles larger than 10 microns are not detected (not atomized) and the daily standardization with reference materials is often time consuming. A modification is available to the AES called rotrode filter spectroscopy (RFS), which increases the size range for particle detection up to at least 25 microns. This technique adds an additional step and time to the testing process; and requires different atomic emission limits to be established. FTIR (ASTM E2412) detects fluid condition (degradation, loss of additives) and organic fluid contamination (water, fuel, incorrect fluid).
It is easy to use; requires no sample preparation; incorporates a built-in reference standard; and is relatively easy to deploy. FTIR requires knowledge of the lubricant class (e.g., gas turbine versus diesel) and the use of a non- flammable solvent. AN determines the change in relative acidity of a lubricant. An increase in acidity is important because it is generally caused by degradation of the lubricant. Note, AN requires the use of hazardous chemicals and generates a separate waste stream. 83 Water by KFT determines the water content in oil detecting low, for example, 50 parts per million (PPM), concentrations of water.
84 The major disadvantage with KFT is it requires the use of hazardous chemicals and generates a separate waste stream. In addition, oxidation by- products are titrated as water, even with an oven attachment. FTIR, mentioned previously, is an easier technique to determine water contamination in polyol ester oils (MIL-PRF-23699F and DOD-PRF-85734A) and clearly differentiates water from degradation by-products. Viscosity determines the ―thickness‖ of the oil. 85 A change in viscosity indicates a change in oil chemistry. For instance, a decrease in viscosity may indicate contamination with a lower viscosity fluid such as fuel.
However, a change in viscosity does not indicate what problem caused the change. Ferrography determines the appearance, type, size and number of wear particles by microscopic examination. 86 This ability is beneficial since the morphology of larger particles may provide some indication of wear mode and metal source. In addition, ferrous and non- ferrous particles are differentiated. Ferrography is often very time consuming, it requires an expert microscopist, and does not determine the elemental or alloy composition of the particles. 83 ASTM D664-11A, Standard Test Method for Acid Number of Petroleum Products by Potentiometric Titration.
Or ASTM D974-11, Standard Test Method for Acid and Base Number by Color-Indicator Titration. 84 ASTM D6304-07, Standard Test Method for Determination of Water in Petroleum Products. Lubricating Oils and Additives by Coulometric Karl Fischer Titration. 85 ASTM D445-11A, Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity). 86 ASTM D7684-11, Standard Guide for Microscopic Characterization of Particles from In Service Lubricants. And ASTM D7690-11, Standard Practice for Microscopic Characterization of Particles from In Service Lubricants by Analytical Ferrography. 248