Southwest Research Institute (SwRI) has been awarded a two-year, $650,000-contract from the US Department of Transportation to study the risks posed by gases dissolved in hazardous liquids during transport.

The federal government has well-defined quantitative criteria and regulations for distinguishing hazardous liquids and gases as well as how and in what materials they can be transported. Some of the properties that distinguish these liquids and gases are their initial boiling point and degree of flammability, respectively.

The regulations related to the transportation of hazardous chemicals such as crude oil or gasoline are very different from those for transporting milk. However, the Department of Transportation lacks regulatory language to classify the liquids containing significant quantities of dissolved gases. Current regulations do not provide guidelines on how much gas can be dissolved in liquid without changing the hazard classification of the fluid.

—SwRI Fluids Engineering Department Research Engineer Dr. Swanand Bhagwat, who leads the project

The gap in regulations creates challenges such as discrepancies in handling and selection of appropriate shipping containers, and enforcement of compliance issues when it comes to transporting these fluids.

Additionally, the presence of gases such as methane and ethane in crude oil or dissolved air in fuels such as diesel and kerosene could increase the vapor pressure and the volatility of the liquids and form an ignitable mixture in the tank being transported.

To safely handle hazardous liquids containing dissolved gases, it is necessary to understand the acceptable thresholds of dissolved gases in liquids to estimate the risk of leaks due to over pressurization, and fire or explosion due to formation of ignitable mixture in the tank.

—Swanand Bhagwat

To address this knowledge gap, Bhagwat will collaborate with SwRI’s Chemistry and Chemical Engineering Division to perform a series of experiments to ascertain the solubility of gases that are often found in hazardous liquids transported through rail cars.

The team will then use computer modeling to characterize associated safety risks and hazards. Additional experiments will determine how the concentration of dissolved gas affects the hazardous properties of the liquid and identify how temperature changes and agitation associated with transport affect risks. Experiments will also assess risk associated with venting or leaking vapors of various gases exuded from liquids.

The outcome of this work will create awareness among the transportation industry about the possible safety and environmental hazards associated with transporting hazardous liquids and help the Department of Transportation develop new regulations.

—Swanand Bhagwat