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US EPA Confirms Alternative Test Method for Crude Oil Vapor Pressure

Release Date: Wednesday, October 30, 2013

CONTACT: Angel Schell 518-689-0055

BROKEN ARROW, OK, October 2013 – A new method for measuring the True Vapor Pressure (TVP) of crude oils is spreading quickly within the oil and gas industry. At request of the American Petroleum Institute (API), the US 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 of high VP crude oils. Widely used by the industry, the new method is now included within AMETEK Petrolab vapor pressure testers.

As defined by International Maritime Organization, the True Vapor Pressure (TVP) or bubble point vapor pressure is the equilibrium vapor pressure of a mixture when the vapor/liquid ratio (V/L) is zero. A V/L =0 can be achieved if a container is filled to the top with crude oil. This condition is typical for floating roof tanks, where the roof is floating directly on the crude oil.

As clear as this definition seems, 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 a ship is filled 95% with crude oil and only 5% vapor space remains, the vapor pressure at a V/L = 0.053 may be referred to as TVP. Within US EPA title 40 regulations, the term TVP is used for a TVP estimate calculated from a D323 Reid Vapor Pressure measurement and the crude oil´s tank stock temperature.

In a letter dated May 28, 2013 and published on its website, the US EPA acknowledged the broad use of the ASTM D6377-10 standard for VP measurement of crude oils. It confirmed the use of D6377 as an alternative method for TVP measurement of volatile crude oils, as defined under title 40 CFR with the understanding that crude oil samples are delivered pressurized for measurement to prevent evaporation of light ends and that the TVP is measured at a V/L = 4.

The ASTM D6377 method is very versatile. It allows measurement of the TVP at various V/L ratios to reflect different tank filling levels. In addition, Grabner vapour pressure analyzers from AMETEK Petrolab include a method for Bubble Point determination. Sandia National Laboratories has used this Bubble Point / TVP extrapolation method successfully (see Lord & Rudeen, 2010): From three D6377 measurements at different V/L ratios, the TVP of crude oil at a V/L = 0 is extrapolated. The extrapolation function assumes that crude oil is composed of three components: very light gas components (e.g. methane or nitrogen), intermediate volatility components (e.g. C2 and higher) and a non-volatile fraction (Lord & Rudeen, 2010).

The TVP extrapolation method used by Grabner analyzers has been successfully demonstrated around the world. The method was used on large number of crude oil samples at the US Strategic Petroleum Reserve, and a similar TVP extrapolation project is currently underway at the Canadian Crude Quality Technical Association (CCQTA).
Additional information on ASTM D6377 laboratory and process vapor pressure testers is available online at or by e-mail at

Literature Cited
(1) Lord, David L. & Rudeen, David K [2010]. Strategic Petroleum Reserve Crude Oil Equation of State Model Development – Current Performance Against Measured Data. Research Report, Sandia National Laboratories, Albuquerque, NM & Livermore, CA, 2010

PETROLAB, a subsidiary of AMETEK, Inc., is widely recognized as the expert in vapor pressure testing. Petrolab’s success is based on the development of portable, rugged and easy-to-operate oil and fuel analyzers for accurate quality control in the laboratory as well as for fast on-site tests in mobile laboratories. Since 1993, its MINIVAP tester has served as the U.S. Environmental Protection Agency’s reference instrument for highest-precision vapor pressure measurement. For additional information contact us at or by calling (918) 459-7170.

AMETEK, Inc. is a leading global manufacturer of electronic instruments and electromechanical devices with annualized sales of $3.6 billion. AMETEK’s corporate growth plan is based on four key strategies: Operational Excellence, Strategic Acquisitions and Alliances, Global and Market Expansion, and New Products. AMETEK is an NYSE-listed stock as well as a component of the S&P 500 and the Russell 1000 Index.

Click here for a hi-res image of the MINIVAP On-line Vapor Pressure Analyzer

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