ASTM D91 standard test method for precipitation number of lubricating oils
1. Scope
1.1 This test method covers the determination of the precipitation number of steam cylinder stocks and black oils, and can be used for other lubricating oils.
1.2 The values stated in acceptable SI units are to be regarded as the standard.
1.3 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.
2. Referenced Documents
2.1 ASTM Standards:
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
D4177 Practice for Automatic Sampling of Petroleum and Petroleum Products
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 ASTM precipitation number, of lubricating oils, n - the number of millilitres of precipitate formed when 10 mL of lubricating oil are mixed with 90 mL of ASTM precipitation naphtha, and centrifuged under the conditions of the test.
4. Significance and Use
4.1 Fully refined petroleum oils normally contain no naphtha insoluble material. Semirefined or black oils frequently contain some naphtha insoluble material (sometimes referred to as asphaltenes). This test measures the amount of naphtha insoluble material in the oil. This quantity is reported as the precipitation number.
