ASTM D6378 Determination of Vapor Pressure of Petroleum Products
ASTM D6378 Standard Test Method for Determination of Vapor Pressure (VPX) of Petroleum Products, Hydrocarbons, and Hydrocarbon-Oxygenate Mixtures (Triple Expansion Method)
1. Scope
1.1 This test method covers the use of automated vapor pressure instruments to determine the vapor pressure exerted in vacuum by volatile, liquid petroleum products, hydrocarbons, and hydrocarbon-oxygenate mixtures. This test method is suitable for testing samples with boiling points above 0°C (32°F) that exert a vapor pressure between 7 and 150 kPa (1.0 and 21psi) 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.
NOTE 1 - The test method is suitable for the determination of the vapor pressure of volatile, liquid petroleum products at temperatures from 0 to 100 °C at vapor to liquid ratios of 4:1 to 1.1 (X = 4 to 1) and pressures up to 500 kPa (70 psi), but the precision statement (see Section 15.) may not be applicable.
1.2 The VPX determined by this test method at a vapor-liquid ratio of 4:1 (X = 4) of gasoline and gasoline–oxygenate blends at 37.8°C can be correlated to the dry vapor pressure equivalent (DVPE) value determined by Test Method D5191 (see Section 15.2).
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 hazard statements, see Note 6.
2. Referenced Documents
2.1 ASTM Standards:
D323 Test Method for Vapor Pressure of Petroleum Products (REID Method)
D1160 Test Method for Distillation of Petroleum Products at Reduced Pressure
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
D4177 Practice for Automatic Sampling of Petroleum and Petroleum Products
D4953 Test Method for Vapor Pressure of Gasoline and Gasoline-Oxygenate Blends (Dry Method)
D5191 Test Method for Vapor Pressure of Petroleum Products (Mini Method)
D5842 Practice for Sampling and Handling of Fuels for Volatility Measurements
D5854 Practice for Mixing and Handling of Liquid Samples of Petroleum and Petroleum Products
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 dry vapor pressure equivalent (DVPE) - a value calculated by a correlation equation from the total pressure (Test Method D5191), which is equivalent to the value obtained on the sample by Test Method D4953, Procedure A.
3.1.2 partial pressure from dissolved air (PPA), n - the pressure exerted in vacuum from dissolved air that escapes from the liquid phase into the vapor phase.
3.1.3 Reid vapor pressure equivalent (RVPE) - a value calculated by a correlation equation from the TPX, which is equivalent to the value obtained on the same by Test Method D323.
3.1.4 total pressure (TPX), n - the pressure exerted in vacuum by air- and gas-containing petroleum products, components and feedstocks, and other liquids, in the absence of undissolved water at a vapor-liquid ration of X:1.
3.1.5 vapor pressure (VPX), n - the total pressure minus the PPA in the liquid at a vapor-liquid ratio of X:1.
VPX = TPX - PPA
