ASTM D7844 Standard Test Method for Condition Monitoring of Soot in In-Service Lubricants by Trend Analysis using Fourier Transform Infrared (FT-IR) Spectrometry
4. Summary of Test Method
4.1 This test method uses FT-IR spectrometry to monitor soot levels in in-service lubricants. The test method is meant to serve as a field-based method to provide an indicator of soot level. The FT-IR spectra of in-service oil samples are collected according to the protocol described in Standard Practice D7418 and the levels of soot are measured using the absorption intensity measurement described herein. The values obtained for the sample of the in-service oil are compared to the value for a sample of new reference oil using either direct trend analysis or differential trend analysis approaches.
5. Significance and Use
5.1 An increase in soot material can lead to increased wear, filter plugging and viscosity, which is usually a consideration for diesel engines, although it may also be an indicator of carburetor or injector problems in other fuel systems. Monitoring of soot is therefore an important parameter in determining overall machinery health and should be considered in conjunction with data from other tests such as atomic emission (AE) and atomic absorption (AA) spectroscopy for wear metal analysis (Test Method D5185), physical property tests (Test Methods D445, D6304 and D2896), and other FT-IR oil analysis methods for oxidation (Test Method D7414), sulfate by-products (Test Method D7415), nitration (Test Method D7624), additive depletion (Test Method D7412), and breakdown products and external contaminants (Practice E2412), which also assess elements of the oil's condition (1-6).
6. Interferences
6.1 High levels of water (>5%) will interfere with the soot measurement in internal combustion engine crankcases. Other interferences include high levels of sludge or insolubles. These interferences will increase the measured soot values.
