ASTM D7170 Standard Test Method for Determination of Derived Cetane Number (DCN) of Diesel Fuel Oils - Fixed Range Injection Period, Constant Volume Combustion Chamber Method
14. Report
14.1 Report the following information:
14.1.1 A reference to this standard,
14.1.2 The sample identification,
14.1.3 The date of the test,
14.1.4 The ID result to the nearest hundredth (0.01 ms),
14.1.5 The DCN result to the nearest tenth (0.1),
14.1.6 The test's average charge air temperature to the nearest tenth °C,
14.1.7 Any deviation, by agreement or otherwise, from the specified procedures,
14.1.8 Whether or not the sample was filtered, and
14.1.9 If the sample was filtered, report the media that was used for filtration.
15. Precision and Bias
15.1 Precision - The precision statements for ID and DCN are based on results from the Interlaboratory Study (ILS) conducted from May to July of 2007. The study involved 15 samples (12 instruments; 12 operators), and covered DCN results ranging from a minimum value of 35.0 DCN (ignition delay of 4.89 ms) to a maximum value of 59.6 (ignition delay of 2.87 ms). The average DCN result for each sample ranged from 37.29 DCN (average ignition delay of 4.5894 ms) to 56.517 (average ignition delay of 3.0281 ms).
NOTE 11 - The precision listed in this test method was obtained on unfiltered samples. Refer to ASTM Research Report RR:D02-1641.
NOTE 12 - A robust statistical study was performed on filtered and nonfiltered samples with respect to DCN measurement. The conclusion of the study was, "No statistically observable effect between filtered vs. non-filtered results". Refer to ASTM Research Report RR:D02-1658.
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 1 only in one case in twenty.
NOTE 13 - The Fuel Ignition Tester (FIT) was used to develop this precision statement.
15.1.2 Reproducibility - The difference between two single independent results obtained on identical test samples under reproducibility conditions would, in the long run, in the normal and correct operation of the test method, exceed the values in Table 1 only one case in twenty.
NOTE 14 - The degrees of freedom associated with the reproducibility estimate from this round robin study are 20. Since the minimum requirement of 30 (in accordance with Practice D6300) is not met, users are cautioned that the actual reproducibility estimate may be significantly different than this estimate.
15.1.3 Examples of precision are shown in Table 2 for information.
15.2 Initial Tentative Precision (2004) - Initial tentative precision was based on results from a within-laboratory study conducted in April 2004. The study involved 22 samples (2 instruments; 1 operator) comprising some samples from the 2003 and 2004 NEG diesel exchange and NEG Cetane Check Fuel and covered DCN range from 40.8 to 58.6 DCN (Ignition Delay range 4.26 ms to 2.97 ms).
15.3 Bias - The ID determined using this test method has no bias because ID is defined only in terms of this test method.
15.4 No bias-correction considered in Practice D6708 can further improve the agreement between results from Test Method D7170 and Test Method D613.
15.4.1 Between Method Reproducibility - Differences between results from Test Method D7170 and Test Method D613, for the sample types and property ranges studied, are expected to exceed the values in Table 3 Between Method Reproducibility (RXY), as defined in Practice D6708, about 5 % of the time.
16. Keywords
16.1 cetane number; derived cetane number; diesel performance; ignition characteristic; ignition delay
