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At the request of the American Petroleum Institute (API), the U.S. Environmental Protection Agency (EPA) recently confirmed the use of the ASTM D6377-10 standard as an alternative test method for the determination of the true vapor pressure (TVP) of crude oils.
As defined by the International Maritime Organization, the true vapor pressure or bubble point vapor pressure is the equilibrium vapor pressure of a mixture when the vapor/liquid ratio (V/L) is zero. This ratio can be achieved if a container is filled to the top with crude oil.
A correct interpretation of the TVP term always depends on the specification for which it is used. In refining, the term TVP often is used to reflect the specific conditions of storage or transport. For example, if a truck or ship is filled 95 percent with crude oil and only 5 percent of vapor space remains, the vapor/liquid ratio of 0.053 may be referred to as TVP.
The ASTM D6377 method allows measurement of TVP at various vapor/liquid ratios to indicate different tank filling levels. Widely used by the oil and gas industry, the new method is now included within the Ametek Grabner Instruments vapor pressure testers provided by Petrolab Company.
For more information, visit www.grabner-instruments.com.