ASTM D7061 Standard Test Method for Measuring n-Heptane Induced Phase Separation of Asphaltene-Containing Heavy Fuel Oils as Separability Number by an Optical Scanning Device
1. Scope
1.1 This test method covers the quantitative measurement, either in the laboratory or in the field, ofhow easily asphaltene-containing heavy fuel oils diluted in toluene phase separate upon addition of heptane. This is measured as a separability number (%) by the use of an optical scanning device.
1.2 The test method is limited to asphaltene-containing heavy fuel oils. ASTM specification fuels that generally fall within the scope of this test method are Specification D396, Grade Nos. 4, 5, and 6, Specification D975, Grade No. 4-D, and Specification D2880, Grade Nos. 3-GT and 4-GT. Refinery fractions from which such blended fuels are made also fall within the scope of this test method.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
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.
2. Referenced Documents
2.1 ASTM Standards:
D396 Specification for Fuel Oils
D975 Specification for Diesel Fuel Oils
D2880 Specification for Gas Turbine Fuel Oils
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:
3.1.1 asphaltenes, n - (rarely used in the singular), in petroleum technology, represent an oil fraction that is soluble in a specified aromatic solvent but separates upon addition of an excess of a specified paraffinic solvent.
3.1.1.1 Discussion - In this test method, the aromatic solvent is toluene and the paraffinic solvent is heptane.
3.1.2 compatibility, n - of crude oils or of heavy fuel oils, the ability of two or more crude oils or fuel oils to blend together within certain concentration ranges without evidence of separation, such as the formation of multiple phases.
3.1.2.1 Discussion - Incompatible heavy fuel oils or crude oils, when mixed or blended, result in the flocculation or precipitation of asphaltenes. Some oils may be compatible within certain concentration ranges in specific mixtures, but incompatible outside those ranges.
3.1.3 flocculation, n - of asphaltenes from crude oils or heavy fuel oils, the aggregation of colloidally dispersed asphaltenes into visibly larger masses that may or may not settle.
3.1.4 peptization, n - of asphaltenes in crude oils or heavy fuel oils, the dispersion of asphaltenes to produce a colloidal dispersion.
3.1.5 stability reserve, n - in petroleum technology, the property of an oil to maintain asphaltenes in a peptized state and prevent flocculation of the asphaltenes.
3.1.5.1 Discussion - An oil with a low stability reserve is likely to undergo flocculation ofasphaltenes when stressed (for example, extended heated storage) or blended with a range of other oils. Two oils each with a high stability reserve are likely to maintain asphaltenes in a peptized state and not lead to flocculation when blended together.
3.1.6 transmittance, n - of light, the fraction of the incident light of a given wavelength that is not reflected or absorbed, but passes through a substance.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 Heavy Fuel v. 1.0, n - the name of a proprietary computer program designed to allow automatic control of test and calculations of the results in Test Method D7061.
3.2.2 separability number, n - in petroleum technology, the standard deviation of the average transmittance, determined in this test method, expressed as a percentage figure.
3.2.2.1 Discussion - The separability number estimates the stability reserve of the oil, where a high separability number indicates that the oil has a low stability reserve and a low separability number that the oil has a high stability reserve.
3.2.3 Turbisoft, n - the name of a proprietary computer spreadsheet program, designed to allow automatic calculation of the results in Test Method D7061.
