Understanding the Behavior of Petroleum in Underground Storage Tanks: Moisture, Evaporation, and Volume Changes

Phenomena like expansion and contraction of petroleum products due to temperature changes affect the integrity and efficiency of underground storage tanks. This article explores how these factors can impact the volume and moisture content of petroleum in such tanks.

Temperature-Induced Volume Changes in Underground Storage Tanks

Petroleum products, like gasoline and diesel, expand and contract with temperature changes. This is a well-known property due to the thermal expansion and contraction of hydrocarbons. However, the magnitude of these changes is small and largely inconsequential in partially filled tanks. This article discusses the implications of filling a large underground storage tank with 600 gallons of petroleum when its capacity is 12,000 gallons.

Underground storage tanks are designed to maintain a stable temperature, often regulated with insulation and proper heat management. Therefore, when warmer fuel is introduced into a colder underground tank, there might be a slight reduction in stored fuel volume. Nevertheless, the changes in volume due to temperature fluctuations are minimal and usually not detectable. Outdoor temperature variations will have little impact on the stored fuel in an underground tank.

Factors Influencing Volume Changes:

Thermal expansion and contraction of petroleum products. Stability of underground temperatures. Quality and design of the underground storage tank.

When filling a tank that is already partially filled, the stored fuel has a pre-existing temperature and volume. Adding warm fuel can lead to minor volume changes, but these changes are typically negligible in terms of practical significance.

Petroleum Evaporation and Moisture Concerns

Petroleum products, notably gasoline, are prone to evaporation. The empty air space within the tank facilitates this evaporation process, pushing fuel vapor into this space until the air reaches its saturation point. This process is a significant concern as it leads to a loss of valuable petroleum product.

A method has been developed to reduce evaporation loss and also improve the mixture in the engine by introducing a fuel additive that is a surface-active agent. The additive works by reducing the vapor pressure of gasoline, which in turn reduces the evaporation rate. However, this method must be carefully considered and implemented to ensure the additive does not negatively impact the performance of the fuel in the engine.

Components of Evaporation Control:

Vapor pressure of petroleum products. Air saturation and evaporation rate. Selective use of fuel additives.

Addressing evaporation loss involves not only the careful addition of chemical agents but also the physical design of the storage tank. Vented tanks are more susceptible to evaporation and can also accumulate water from the air due to condensation, which can lead to the formation of moisture. Ensuring proper sealing and maintaining a consistent temperature are crucial for minimizing these losses.

Practical Considerations and Recommendations

When filling an underground storage tank, it is essential to understand the behavior of the petroleum product in relation to temperature and volume changes. Ensuring that the tank is well-insulated and properly sealed can significantly reduce the risk of evaporation and moisture buildup. Careful temperature management also helps maintain the integrity of the stored fuel, ensuring that it remains in optimal condition for use.

Using fuel additives can be an effective strategy for reducing evaporation loss, but their use must be carefully monitored. Regular maintenance and monitoring of the storage tank can help identify any issues and address them promptly.

Key Points to Remember:

Monitor the temperature of the tank and adjust accordingly. Use vapor recovery systems if necessary to minimize evaporation loss. Ensure the tank is properly sealed to prevent water intrusion. Regularly check the tank for damage or leaks.

Understanding and managing the behavior of petroleum in underground storage tanks is crucial for maintaining the efficiency and safety of the fuel system. By addressing the impacts of temperature, evaporation, and moisture, operators can ensure that their stored fuel remains in optimal condition for extended periods.