ASTM D7157 Standard Test Method for Determination of Intrinsic Stability of Asphaltene-Containing Residues, Heavy Fuel Oils, and Crude Oils (n-Heptane Phase Separation; Optical Detection)
14. Report
14.1 Report the following information:
14.1.1 A reference to this test method.
14.1.2 The sample identification.
14.1.3 The date of the test.
14.1.4 The stability parameters: S, Sa, and So, to the nearest 0.01.
14.1.5 The goodness of fit, R-squared.
14.1.6 Any deviation, by agreement or otherwise, from the specified procedures.
14.2 For an example of the output report of the analyzer system and the intermediate calculations given in equations Eq 1-4 (see 13.1), refer to Fig. X1.1 and Fig. X1.2.
NOTE 5 - Users of this test method would normally use stability and compatibility parameters to determine stability reserve of residual products, fuel blends, and crude oils. However, the interpretation of stability, stability reserve, and compatibility is beyond the scope of this test method.
15. Precision and Bias
15.1 Precision - The precision statements for S, Sa, and So were obtained by statistical analysis of results from an interlaboratory study involving 11 laboratories using 5 residual fuel oils, 2 thermally cracked residues, 1 atmospheric distillation residue, and 3 crude oils. The study covered the S nominal range from 1.29 to 4.23, the Sa nominal range from 0.4 to 0.85, and the So nominal range from 0.46 to 1.36.
NOTE 6 - Nominal ranges are determined by (min. sample mean - Reproducibility) to (max. sample mean + Reproducibility).
15.1.1 Repeatability - The difference between successive results obtained by the same operator with the same apparatus, under constant operating conditions, on identical test materials would, in the long run, in the normal and correct operation of the test method, exceed the values in Table 2 only in one case in twenty.
15.1.2 Reproducibility - The difference between two single and independent results obtained by different operators working in different laboratories on identical test material would, in the long run, in the normal and correct operation of this test method, exceed the values in Table 2 only in one case in twenty.
15.2 Bias - This test method has no bias because the results of the test are defined only in terms of this test method.
16. Keywords
16.1 asphaltenes; compatibility; crude oil; heavy fuels oils; intrinsic stability; S-value; phase separation; residual oil
