ASTM D2889 Test Method for Calculation of True Vapor Pressures of Petroleum Distillate Fuels
3. Summary of Test Method
3.1 Equilibrium flash vaporization (EFV) temperatures are calculated from distillation data (Test Method D86) determined on the sample. The distillation data, calculated EFV data, and API gravity of the sample are used with a graphical correlation procedure to obtain two pairs of temperature-pressure coordinates through which the bubble-point line of the phase diagram for the sample may be drawn. The calculated true vapor pressure at a specified temperature is obtained by reading the pressure at the intersection of the bubble-point line and specified temperature.
NOTE 1 - Details of the procedure and data substantiating its validity for establishing equilibrium flash vaporization temperatures have been published.
4. Significance and Use
4.1 The true vapor pressure of a distillate fuel is a relative measurement, both of the tendency of the most volatile portion of the fuel to gasify, and of the restraining pressure required to prevent gasification of the most volatile portion. Thus the measurement is of importance when a fuel is to be utilized in applications where no gasification may be tolerated, and temperature-pressure conditions are expected to be near the true vapor pressure of the fuel.
