ASTM D5191 Test Method for Vapor Pressure of Petroleum Products (Mini Method)
1. Scope
1.1 This test method covers the use of automated vapor pressure instruments to determine the total vapor pressure exerted in vacuum by air-containing, volatile, liquid petroleum products. This test method is suitable for testing samples with boiling points above 0°C (32°F) that exert a vapor pressure between 7 and 130 kPa (1.0 and 18.6 psi) at 37.8°C (100°F) at a vapor-to-liquid ratio of 4:1. Measurements are made on liquid sample sizes in the range from 1 to 10 mL. No account is made for dissolved water in the sample.
NOTE 1 - Samples can also be tested at other vapor-to-liquid ratios, temperatures, and pressures, but the precision and bias statements need not apply.
NOTE 2 - The interlaboratory studies conducted in 1988 and 1991 to determine the precision statements in Test Method D5191 did not include any crude oil in the sample sets. Test Method D6377, as well as IP 481, have been shown to be suitable for vapor pressure measurements of crude oils.
1.1.1 Some gasoline-oxygenate blends may show a haze when cooled to 0 to 1°C. If a haze is observed in 8.5, it shall be indicated in the reporting of results. The precision and bias statements for hazy samples have not been determined (see Note 11).
1.2 This test method is suitable for calculation of the dry vapor pressure equivalent (DVPE) of gasoline and gasoline-oxygenate blends by means of a correlation equation (see 13.2). The calculated DVPE very closely approximates the dry vapor pressure that would be obtained on the same material when tested by Test Method D4953.
1.3 The values stated in SI units are regarded as standard. The inch-pound units given in parentheses are provided for information only.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific warning statements, see 7.2 through 7.7.
2. Referenced Documents
2.1 ASTM Standards:
D2892 Test Method for Distillation of Crude Petroleum (15-Theoretical Plate Column)
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
D4953 Test Method for Vapor Pressure of Gasoline and Gasoline-Oxygenate Blends (Dry Method)
D5190 Test Method for Vapor Pressure of Petroleum Products (Automatic Method)
D6377 Test Method for Determination of Vapor Pressure of Crude Oil: VPCRx (Expansion Method)
2.2 IP Standards:
IP 481 Test Method for Determination of the Air Saturated Vapour Pressure (ASVO) of Crude Oil
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 absolute pressure - the pressure of the air-free sample. It is calculated from the total pressure of the sample by subtracting out the partial pressure of the dissolved air.
3.1.2 dry vapor pressure equivalent (DVPE) - a value calculated by a correlation equation (see 13.2) from the total pressure.
3.1.2.1 Discussion - The DVPE is expected to be equivalent to the value obtained on the sample by Test Method D4953, Procedure A.
3.1.3 total pressure - the observed pressure measured in the experiment that is the sum of the partial pressure of the sample and the partial pressure of the dissolved air.
