ASTM D6377 for determination of vapor pressure of crude oil
ASTM D6377 standard test method for determination of vapor pressure of crude oil: VPCR(X) (Expansion method)
4. Summary of Test Method
4.1 Employing a measuring chamber with a built-in piston, a sample of known volume is drawn from a pressurized sampling system (floating piston cylinder) into the temperature controlled chamber at 20°C or higher. After sealing the chamber, the volume is expanded by moving the piston until the final volume produces the desired V/L value. The temperature of the measuring chamber is then regulated to the measuring temperature.
4.2 After temperature and pressure equilibrium, the measured pressure is recorded as the VPCRx of the sample. The test specimen shall be mixed during the measuring procedure by shaking the measuring chamber to achieve pressure equilibrium in a reasonable time between 5 and 30 min.
4.3 For results related to Test Method D323, the final volume of the measuring chamber shall be five times the test specimen volume and the measuring temperature shall be 37.8°C.
5. Significance and Use
5.1 Vapor pressure of crude oil at various V/Ls is an important physical property for shipping and storage.
5.2 Vapor pressure of crude oil is important to crude oil producers and refiners for general handling and initial refinery treatment.
NOTE 1 - A V/L of 0.02:1 (X = 0.02) mimics closely the situation of an oil tanker.
5.3 To prevent losses of high volatile compounds, the sample is always maintained at a pressure at least 100 kPa (14.5 psi) higher than the vapor pressure.
5.4 The vapor pressure determined by this test method at a V/L of 4:1 (VPCR4) of crude oil at 37.8°C can be related to the vapor pressure value determined on the same material when tested by Test Method D323 (see Appendix X1).
5.5 Chilling and air saturation of the sample prior to the vapor pressure measurement is not required.
5.6 This test method allows the determination of VPCRx samples having pour points above 0°C.
