ASTM D5772 Standard Test Method for Cloud Point of Petroleum Products and Liquid Fuels (Linear Cooling Rate Method)
12. Report
12.1 Report the temperature recorded in 11.6 as the automatic cloud point Test Method D5772.
12.2 When specified, round the temperature recorded in 11.6 to the next lower integer and report as the Test Method D2500 equivalent cloud point in accordance with Test Method D5772.
13. Precision and Bias
13.1 Precision - The precision of this test method as determined by the statistical examination of the interlaboratory test results is as follows:
13.1.1 Repeatability - 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 ofthis test method, exceed 1.3 °C only in one case in twenty.
13.1.2 Reproducibility - 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 3.3 °C only in one case in twenty.
13.1.3 The precision statements were derived from a 1997 interlaboratory cooperative test program. Participants analyzed eleven sample sets, as blind duplicates, comprised of various distillate fuels and lubricating oils with a temperature range from +34 °C to -56 °C. Five laboratories participated with the automatic apparatus and eight laboratories participated with the manual Test Method D2500/IP 219 test method. Information on the type of samples and their average cloud points are in the research report.
13.2 Bias - Since there is no accepted reference material suitable for determining the bias for the procedure in this test method, bias has not been determined.
13.3 Relative Bias - The results of the interlaboratory program were examined for bias relative to Test Method D2500/IP 219. Although statistically significant bias was observed, the magnitude was determined to be small enough (-0.67 °C) to be of little practical significance.
13.4 Precision forBiodiesel Products - The precision of this test method, as determined by the statistical examination of the interlaboratory test results, is as follows:
13.4.1 Repeatability for Biodiesel in Diesel Blends - 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 0.7 °C only in one case in twenty.
13.4.2 Reproducibility for Biodiesel in Diesel Blends - 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 normal and correct operation ofthis test method, exceed 2.2 °C only in one case in twenty.
NOTE 4 - The precision for blends of biodiesel in diesel samples comprised cloud points from about -2 °C to + 10 °C.
13.4.3 The precision statements were derived from a 2001 interlaboratory cooperative test program. Participants analyzed eleven sample sets comprised of two petroleum distillate fuels, diesel and kerosine, with various biodiesel fuels with a temperature range from +10 °C to -45 °C. Five laboratories participated with the automatic machines and ten laboratories participated with the manual Test Method D2500/IP 219. Information on the type of samples and their average cloud points are in the research report.
NOTE 5 - One of the outcomes of the interlaboratory study was the selection of the sample types used in the study contributed to a difficulty in determining the precision statement. Kerosine is a sufficiently different fuel type from biodiesel to cause some slight separation of phases upon cooling when in B20 blends. Also, the particular kerosine sample used was atypical, which complicated the study further. Therefore data from the blends of kerosine in biodiesel were not used in the precision statement. In addition, the diesel fuel used in the round-robin 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 6 - A future interlaboratory cloud study will be done including a wider range of base biodiesel fuels with various distillate blend stocks.
13.5 Bias - Since there is no accepted reference material suitable for determining the bias for the procedure in this test method, bias has not been determined for blends ofbiodiesel in diesel samples.
13.6 Relative Bias - The statistical analysis for the interlaboratory test program for bias relative to Test Method D2500/IP 219 has not been determined.
14. Keywords
14.1 automatic cloud point; cloud point; D2500 equivalent cloud point; petroleum products
