ASTM D2500 standard test method for cloud point of petroleum products
9. Report
9.1 Report the temperature recorded in 8.7 as the cloud point, Test Method D2500.
10. Precision and Bias
10.1 The precision of this test method as determined by statistical examination of interlaboratory results is as follows:
10.1.1 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 2°C only in 1 case in 20.
10.1.2 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 4°C only in 1 case in 20.
10.1.3 The precision statements were derived from a 1990 interlaboratory cooperative test program. Participants analyzed 13 sample sets comprised of various distillate fuels and lubricating oils with temperature range from -1 to -37°C. Eight laboratories participated with the manual D2500/IP219 test method. Information on the type of samples and their average cloud points are in the research report.
10.2 Bias - The procedure in this test method has no bias, because the value of cloud point can be defined only in terms of a test method.
10.3 Precision for Biodiesel Products - The precision of this test method as determined by statistical examination of interlaboratory results is as follows:
10.3.1 Repeatability for Blends of Biodiesel in Diesel - The difference between successive test results obtained by the same operator, using 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 2°C only in 1 case in 20.
10.3.2 Reproducibility for Blends of Biodiesel in Diesel - The difference between two single and independent test 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 3°C only in 1 case in 20.
NOTE 6 - The precision for blends of biodiesel in diesel samples comprised cloud points from about -2 to +10°C.
10.3.3 The precision statements were derived from a 2001 interlaboratory cooperative test program. Participants analyzed eleven sample sets comprised of different blends of two petroleum distillate fuels, diesel and kerosene, with various biodiesel fuels with temperature range from +10 to -45°C. Ten laboratories participated with the manual D2500/IP219 test method. Information on the type of samples and their average cloud points are in the research report.
NOTE 7 - One of the outcomes of the interlaboratory study was the selection of the sample types, since the ones used in the study contributed to a difficulty in determining the precision statement. Kerosene is a sufficiently different fuel type from biodiesel to cause some slight separation of phases upon cooling when in B20 blends. Also, the particular kerosene sample used was atypical, which complicated the study further. Therefore, data from the blends of kerosene in biodiesel were not used in the precision statement. In addition, the diesel fuel used in the research report was high cloud point material. Due to the cloud point of the base diesel material, this temperature range in the precision statement was limited.
NOTE 8 - A future interlaboratory cloud study will be done to include a wider range of base biodiesel fuels with various distillate blend stocks.
10.4 Bias for Biodiesel Products - The procedure in this test method has no bias, because the value of cloud point can be defined only in terms of a test method.
11. Keywords
11.1 cloud point; petroleum products; wax crystals
