5.1 New and used petroleum products can contain basic constituents that are present as additives or as degradation products formed during service. The amount of these additives in an oil can be determined by titrating against an acid. The base number is a measure of the amount of basic substance in the oil, always under the conditions of the test. A decrease in base number is often used as a measure of lubricant degradation, but any condemning limits must be empirically established.
5.2 This test method uses reagents that are considered less hazardous than most reagents used in alternate base number methods. It uses pre-packaged reagents to facilitate base number determinations in the field where scientific equipment is unavailable and quick results are at a premium.
NOTE 1: Results obtained by this test method3 are similar to those obtained by Test Method D2896.
1.1 This test method covers a procedure for determining the basic constituents in petroleum products in the field or laboratory using a pre-packaged test kit. The test uses a micro-titration resulting in a visual endpoint facilitated by a color indicator.
1.1.1 This test method covers base numbers from 0 to 20. It can be extended to higher ranges by diluting the sample or by using a smaller sample size; however, the precision data were obtained for base numbers up to 20.
1.2 This test method can be used to indicate relative changes that occur in an oil during use under oxidizing conditions. Although the test is performed under closely specified conditions with standardized reagents, the test method does not measure an absolute basic property that can be used to predict performance of an oil under service conditions. No general relationship between bearing corrosion and base number is known.
1.3 The values stated in SI units are to be regarded as the standard.
1.3.1 Exception—The values given in parentheses are for information only.
1.4 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 and health practices and determine the applicability of regulatory limitations prior to use.
1.5 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.
Extracted, with permission, from ASTM D5984 - 11(2017) Standard Test Method for Semi-Quantitative Field Test Method for Base Number in New and Used Lubricants by Color-Indicator Titration, copyright ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428. A copy of the complete standard may be purchased from ASTM International, astm.org
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