ASTM D4305 Test Method for Filter Flow of Aviation Fuels at Low Temperatures
12. Report
12.1 Record the flow temperature to the nearest 0.1°C. When determining compliance with aviation fuel specifications, the flow temperature can be reported as the freezing point of the fuel.
12.2 Record the no-flow temperature to the nearest 0.1°C (optional).
12.3 Record whether Procedure A or Procedure B was used.
13. Precision and Bias
13.1 The precision of this test method, as determined by statistical analyses of interlaboratory results, is as follows:
13.1.1 Repeatability - The difference between two test results obtained by the same operator with the same apparatus under constant operating conditions, on identical test material would, in the long run, in the normal and correct operation of this test method, exceed the following only in one case in 20.
13.1.1.1 Procedure A, 26-µm Test Filter - r = 0.53°C.
13.1.1.2 Procedure B, 42-µm Test Filter - r = 1.2°C.
13.1.2 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 correct operation of this test method, exceed the following only in one case in 20.
13.1.2.1 Procedure A, 26-µm Test Filter - R = 2.21°C.
13.1.2.2 Procedure B, 42-µm Test Filter - R = 2.6°C.
13.2 Test Programs:
13.2.1 Procedure A (26-µm Test Filter) - An international interlaboratory test program7 involving 14 aviation fuels and seven laboratories was carried out in 1993-1994, comparing flow point with freezing point by Test Method D2386. Four fuels were excluded from the analysis because their viscosities exceeded 5.0 mm2/s (cSt) at -20°C.
13.2.2 Procedure B (42-µm Test Filter) - A1980 interlaboratory test program involving 19 aviation fuels among eight laboratories was carried out comparing flow point results with freezing point by Test Method D2386. Two fuels were excluded from analysis because their flow points exceeded the low temperature limit of the instrument (about -70°C).
13.3 Bias - Since there is no accepted reference material suitable for determining the bias of the procedures in this test method, bias cannot be determined.
13.4 Relationship to Test Method D2386 - The following relative bias was determined when compared to the results of Test Method D2386.
13.4.1 Procedure A (26-µm Filter) - The interlaboratory program indicated no relative bias between this test method and Test Method D2386.
13.4.2 Procedure B (42-µm Test Filter) - The correlation between FR (freezing point in Test Method D2386), and FP (flow point in this test method), is given as follows:
FR(°C) = 1.04 (FP°C) + 2.67°C
NOTE 5 - Procedure A: Aviation fuels with a viscosity of greater than 5 mm2/s (cSt) at -20°C (determined by Test Method D445) can give a result which is warmer than the freezing point determined by Test Method D2386.
NOTE 6 - Procedure B: Fuels of similar composition and wax precipitation characteristics can exhibit constant bias from the correlation line between freezing point and flow point. Where this occurs, such as production from a single refinery or crude source, a different correlation may exist.
NOTE 7 - Procedure B: Results of up to 10°C colder than those obtained by Test Method D2386 have been reported when testing hydrocracked fuels.
14. Keywords
14.1 aviation fuels; filter flow; flow point; freezing point
