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Vapor Space Flammability of Automobile Tanks Containing Low RVP Gasolines
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Abstract
As a means of reducing evaporative emissions from gasoline sources, the Environmental Protection Agency (EPA) and other legislative and regulatory bodies have required reductions in gasoline volatility. Further reductions are being proposed. This paper reports the results of an investigation into the resulting flammability potential of low volatility gasolines contained in automobile tanks when low ambient temperatures are experienced.
The hydrocarbon composition and the flammability tendency of the vapor in fuel tanks of passenger cars were determined via a matrix of 45 different gasoline volatility, temperature, and tank level combinations. A flammability device was developed and used to ignite vapors drawn from the tanks of in-use vehicles at the test conditions. The Reid Vapor Pressure (RVP) of the test gasolines ranged from 6.5 to 9.4 psi in the near-full tank level and 6.4 to 7.8 psi at a low tank level. Ambient test temperatures were selected to represent probable winter/spring and fall/winter transition period low temperatures. Results demonstrate that at moderately low temperatures and low gasoline volatility conditions, the vapor space of a vehicle's fuel tank will be flammable and no longer “protected” by the volatile components in the fuel. Such a condition will result in a flame if an ignition source is available. It was demonstrated that an initial fill of 9.4 psi RVP gasoline does not result in a flammable vapor space at temperatures above 0°F. However, upon drive-down to a low tank level, the same gasoline produced a fully flammable vapor space at 0°F and even a marginally flammable vapor space at 10°F. A simple model was developed to predict fuel tank hydrocarbon vapor concentrations as a function of the gasoline RVP and operating temperature. The model can be used to predict gasoline fuel tank conditions that will result in a potentially flammable and unsafe condition.
Marketing fuels under past American Society of Testing and Material (ASTM) recommended volatility classes and transitional periods helped assure that commercial gasolines produce fuel-rich (non-flammable) conditions in vapor spaces of storage tanks. The ASTM recommended geographical and seasonal adjustments helped to maintain this extra margin of safety regardless of location or time of year. Gasolines marketed today under the EPA Phase I regulations on gasoline volatility may continue to largely avoid this concern with their high volatility components producing a gasoline vapor concentration sufficient for the gaseous phase above the fuel to be richer than the fuel-rich flammability limit. This means that insufficient air or oxygen is present to sustain a flame. Thus, the tank is protected against ignition or explosion from extraneous sparks or arcing within the tank's vapor space.
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Citation
Marshall, W. and Schoonveld, G., "Vapor Space Flammability of Automobile Tanks Containing Low RVP Gasolines," SAE Technical Paper 902096, 1990, https://doi.org/10.4271/902096.Also In
References
- Environmental Protection Agency “Regulation of Fuels and Fuel Additives: Volatility Regulations for Gasoline and Alcohol Blends Sold in Calender Years 1989 and Beyond; Final Rule,” Federal Register 54 54 March 22 1989
- American Society of Testing and Material “Standard Test Method for Vapor Pressure of Petroleum Products (Reid Method),” 1990 Annual Book of ASTM Standards, Designation: D323-89 05.01 132 1990
- Brownlow A. D. Brunner J. K. Welstand J. S. “Changes in Reid Vapor Pressure of Gasoline in Vehicle Tanks as the Gasoline is Used,” Society of Automotive Engineers paper no. 892090 1989
- Barth E. A. “Vehicle Fuel Weathering Effect with Operating Temperatures on the Road and Dynamometer,” Environmental Protection Agency Report EPA-AA-TEB-86-01 March 1986
- Automotive Testing Laboratories, Inc. “Final Report - Driving Cycle Effect on Tank Fuel Temperature,” Environmental Protection Agency Work Assignment 1-6 of Contract 68-03-3380 July 29 1988
- Environmental Protection Agency “Regulation of Fuels and Fuel Additives: Volatility Regulations for Gasoline and Alcohol Blends Sold in 1989 and Later Calendar Years; Notice of Proposed Rulemaking,” Federal Register 52 160 August 19 1987
- American Petroleum Institute “Comments of the American Petroleum Institute Concerning EPA's August 19, 1987 Proposed Regulation of Fuels and Fuel Additives and Regulation of Refueling Emissions,” February 11 1988
- Phillips Petroleum Company “Comments of Phillips Petroleum Company Concerning EPA's August 19, 1987 Proposed Regulation of Fuels and Fuel Additives and Regulation of Refueling Emissions,” February 1988
- Environmental Protection Agency “Regulation of Fuels and Fuel Additives: Volatility Regulations for Gasoline and Alcohol Blends Sold in Calender Year 1992 and Beyond; Final Rule,” Federal Register 55 112 June 11 1990
- Bardo M. F. Rao V. K. Battista V. “Volatility and Flammability of Methanol/Gasoline Blends,” Society of Automotive Engineers paper no. 892062 1989
- Doner J. P. “Final Report - A Predictive Study for Defining Limiting Temperatures and Their Application in Petroleum Product Specifications,” U.S. Army CCL Report No. 316 November 1972
- Moore W. J. “Physical Chemistry.” 1959
- Zabetakis M. G. “Flammability Characteristics of Combustible Gasses and Vapors.” Bulletin 627 Bureau of Mines 1965