ASTM D7686-19

5.1 This test method provides a simple field-based technique for condition monitoring of soot in in-service lubricants associated with combustion engines, machinery, and equipment used in industry and by the military. Critical applications should use laboratory-based test methods, such as Thermal Gravimetric Analysis (TGA) described in Test Method D5967, Annex A4. Infrared spectroscopy is a well-established laboratory method for evaluating soot levels in lubricants. This test method can be used to monitor soot build-up in lubricants and can indicate whether soot has accumulated to an extent that could significantly degrade the performance of the oil. High soot content can compromise lubricant performance and cause filter and oil passage blockage. Soot concentration should be considered in conjunction with data from other condition monitoring tests as described in Practice E2412 to determine whether the oil should be replaced to minimize machinery wear or failure, or both.

1.1 This test method pertains to field-based monitoring of soot in diesel crankcase engine oils as well as in other types of engine oils where soot may contaminate the lubricant as a result of a blow-by due to incomplete combustion of fuels. It is applicable to oils having soot levels of up to 12 % by mass.

1.2 This test method uses filter-based infrared technology for monitoring of soot build-up in in-service petroleum and hydrocarbon-based lubricants as a result of normal machinery operation. Soot levels in engine oils rise as soot particles contaminate the oil as a result of exhaust gas recirculation from blow-by. This test method is designed as a fast, simple, and field-capable spectroscopic check for soot in in-service hydrocarbon-based lubricants with the objective of helping diagnose the operational condition of the machine based on measuring the level of soot in the oil.

1.3 This test method is intended as a field test only, and should be treated as such. Critical applications should use laboratory based methods, such as Thermal Gravimetric Analysis (TGA) described in Test Method D5967, Annex A4.

1.4 Acquisition of spectral data for measuring soot in in-service oil and lubricant samples with the use of a fixed-filter IR instrument is described in this test method. Calibration against prepared soot standards is also described.

1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.