ASTM D6426 method for determining fiterability of middle distillate fuel oils
10. Report
10.1 Report the following information:
10.1.1 The source and how the sample was obtained, as required in 7.1.
10.1.2 The temperature recorded in 9.4 and, if applicable, undissolved water present, filtration not performed; otherwise, report per 10.1.3.
10.1.3 The final pressure (P(F)) and volume (V(F)) in the form P(F)(kPa)/V(F)(mL) or P(F)(psi)/V(F)(mL), and F-QF.
11. Precision and Bias
11.1 Precision - The precision for the F-QF of this test method for field samples of diesel, home heating, and blended bio-diesel fuels was determined by statistical analysis of test results obtained by a cooperative test program conducted at a common test site. The precision of this procedure in this test method for measuring filterability of aviation turbine fuels and gasoline is being determined.
NOTE 4 - These results were calculated by applying ASTM D2PP statistical analysis computer program8 to the data obtained from a May 2000 laboratory cooperative test program. The repeatability and reproducibility values were calculated from the results obtained at the same location on two consecutive days, by six different operator/instrument pairs performing replicate tests on twelve identical samples. Results, particularly for reproducibility, obtained at different times and locations may, therefore, not be comparable according to these calculations, since they may contain errors due to sampling and environmental factors. In practice, two results obtained at different laboratories (locations) would be acceptable if their difference did not exceed the published reproducibility. In the event that the difference did exceed the reproducibility there would be no means of testing whether the results were acceptable. This precision analysis may not apply to samples having viscosities other than those that were used in the round robin program.
11.1.1 Repeatability - The difference between successive measured F-QF values obtained by the same operator with the same apparatus under constant operating conditions on identical test material at the same fuel temperature would, in the long run, in the normal and correct operation of the test method, exceed the values in Table 1, graphically shown in Fig. 4, only in one case in twenty.
11.1.2 Reproducibility - The difference between two single and independent measurements of F-QF values obtained by different operators using different apparatus under constant operating conditions on identical test material at the same fuel temperature would, in the long run, in the normal and correct operation of the test method, exceed the values in Table 1, graphically shown in Fig. 4, only in one case in twenty.
11.2 In 1999, a test program was carried out to investigate reproducibility of results when samples are shipped between laboratories. While repeatability values were similar to those in Table 1, it was concluded that adequate reproducibility values were not obtained due to changes in the physical characteristics of samples during shipment, storage, and aging. The latter was considered to have the most effect since the different laboratories randomly tested the samples over a three-month period. In the event of dispute or concern regarding the F-QF of the shipped sample, it is recommended that operators come to the bulk fuel storage site to measure F-QF on bulk fuel or on freshly obtained samples according to cited procedures. This ensures that a sample identical to the bulk supply is tested by either or both parties and the precision data shown in Table 1 and Fig. 4, shall apply.
11.3 Bias - The procedure in this test method has no bias because the value of F-QF is defined only in terms of this test method.
12. Keywords
12.1 aviation turbine fuels; distillate fuels; filterability; fuel cleanliness; fuel filterability; gas oils
