Standard Test Method for Vapor Pressure of Petroleum Products and Liquid Fuels (Mini Method).
Get more information about the standard at ASTM D5191-22.
ASTM D5191 specifies a procedure for measuring the vapor pressure of petroleum products, including gasoline, gasoline-oxygenate blends, and other volatile fuels. Vapor pressure is a crucial property for fuel performance, safety, and environmental compliance, influencing fuel evaporation, engine performance, and emissions. This method provides accurate, rapid results using a piston based mini vapor pressure analyzer, making it a preferred choice for quality control and regulatory compliance.
Details
ASTM D5191 is a method for determining the vapor pressure of fuels at a specified temperature. The test is conducted using a piston based mini vapor pressure analyzer, which operates under controlled conditions to provide precise and reproducible measurements. The sample must be chilled and air-saturated to give accurate results. After introducing the sample, the valves of the
instruments are closed and the piston is expanded to generate a vacuum in the headspace above the sample. Due to the volatility of the sample, the vapor pressure of the sample can be detected in the head space after thermal equilibrium.
ASTM D5191 is advantageous because it requires a smaller sample volume and operates more quickly than traditional vapor pressure methods like ASTM D4953. However, due to the requirement of sample preparation, it is prone to operator bias, a significant disadvantage compared to more modern vapor pressure methods like ASTM D6378.
Vapor pressure data from ASTM D5191 is used to evaluate seasonal fuel volatility, prevent vapor lock, ensure safety during transportation and storage, and limit evaporative emissions in accordance with environmental standards such as those set by the U.S. Environmental Protection Agency (EPA).
Industries & Applications
ASTM D5191 is widely used in the following industries:
- Petroleum refining: Ensures fuel meets regional and seasonal volatility specifications
- Fuel blending facilities: Monitors ethanol-gasoline blends to comply with emissions and performance standards
- Automotive industry: Validates that fuels meet performance and emissions criteria for modern engines
- Environmental agencies: Enforces compliance with fuel volatility regulations to control evaporative emissions
- Fuel distribution and storage: Maintains safety and stability during transportation and storage under varying conditions