ASTM D5191 Test Method for Vapor Pressure of Petroleum Products (Mini Method)
14. Report
14.1 Report the dry vapor pressure equivalent to the nearest 0.1 kPa (0.01 psi) without reference to temperature.
14.2 If the sample was observed to be hazy in 8.5, report the test result as in 14.1, followed by the letter H.
NOTE 11 - The precision and bias statements have not been determined for hazy samples since these types of samples have not been evaluated as part of a interlaboratory study.
NOTE 12 - The inclusion of the letter H in 14.2 is intended to alert the data recipient that the sample analyzed was hazy. In the event that a laboratory has a computer system that is incapable of reporting alphanumeric results in accordance with the requirements in 14.2, it is permissible for the laboratory to report the result obtained as in 14.1, along with a statement or annotation that clearly conveys to the data recipient that the analyzed sample was hazy.
15. Precision and Bias
15.1 Precision - The precision of this test method as determined by the statistical examination of interlaboratory test results is as follows:
NOTE 13 - The following precision data were developed in a 1991 interlaboratory cooperative test program. Participants analyzed sample sets comprised of blind duplicates of 14 types of hydrocarbons and hydrocarbon-oxygenate blends. The oxygenate content (MTBE, ethanol, and methanol) ranged from 0 to 15 by volume nominal and the vapor pressure ranged from 14 to 100 kPa (2 to 15 psi) nominal. A total of 60 laboratories participated. Some participants performed more than one test method, using separate sample sets for each. Twenty-six sample sets were tested by Test Method D5190 and 27 by this test method. In addition, six sets were tested by modified Test Method D5190, and 13 were modified by this test method.
15.1.1 Repeatability - The difference between successive 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 the test method, exceed the value calculated as per Eq 2 only in one case in twenty:
repeatability = 0.00807 (DVPE + B)
where:
B = 124 kPa (18.0 psi).
15.1.2 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 the test method, exceed the value calculated as per the following equation only in 1 case in 20:
reproducibility = 0.0161 (DVPE + B)
where:
B = 124 kPa (18.0 psi).
15.2 Bias - Since there is no accepted reference material suitable for determining the bias for the procedures in this test method, bias cannot be determined.
15.3 Relative Bias - A statistically significant relative bias was observed in the 1991 interlaboratory cooperative test program between the total pressure obtained using this test method and the dry vapor pressure obtained using Test Method D4953, procedure A. This bias is corrected by the use of Eq 1 (see 13.2), which calculates a DVPE value from the observed total pressure.
16. Keywords
16.1 dry vapor pressure; gasoline; hydrocarbon-oxygenate blends; mini method; petroleum products; vapor pressure
