Fuel Vapor Recovery Tank Saturation: A Comprehensive Guide

Fuel vapor recovery tank saturation is a critical safety concern in the aviation industry, particularly in transport airplanes with fuel tanks located near heat sources. The saturation of fuel vapor recovery tanks can lead to the accumulation of explosive vapors, posing a significant risk of explosion. To address this issue, the FAA has established regulations and guidelines to minimize the hazards associated with explosive fuel-air mixtures in all transport airplane fuel tanks.

Analyzing the Threat of Fuel Tank Explosion

One of the key aspects of fuel vapor recovery tank saturation is the analysis of the threat of fuel tank explosion due to internal and external tank ignition sources. The SAFER data presented to the FAA in 1978 serves as a starting point for determining the level of safety. This data includes an evaluation of fuel tank safety in both operational and post-crash conditions.

The SAFER data analysis revealed that the probability of a fuel tank explosion due to internal ignition sources, such as electrical arcing or hot surface ignition, is approximately 1 in 10 million flight hours. However, the probability of a fuel tank explosion due to external ignition sources, such as lightning strikes or engine/APU fires, is significantly higher, ranging from 1 in 100,000 to 1 in 1 million flight hours.

To further reduce the risk of fuel tank explosions, the FAA has requested industry through the American Petroleum Institute to provide information on fuel properties that could reduce exposure to explosive vapors within fuel tanks. Factors that may enhance the benefits of modified fuels, such as cooling provisions incorporated to reduce fuel tank temperatures, should be considered.

Reducing Exposure to Explosive Vapors

fuel vapor recovery tank saturation

In addition to fuel properties, various means of reducing or eliminating exposure to explosive vapors in fuel tanks should be analyzed. These may include:

  1. Inerting: The introduction of an inert gas, such as nitrogen or carbon dioxide, into the fuel tank to displace the oxygen and prevent the formation of an explosive fuel-air mixture.
  2. Cooling of Lower Center Tank Surfaces: Reducing the temperature of the lower center tank surfaces can decrease the saturation of fuel vapors, thereby reducing the risk of explosion.
  3. Combination of Cooling and Modified Fuel Properties: A combination of cooling provisions and the use of modified fuel properties, such as increased flash point or reduced vapor pressure, can further enhance the safety of fuel tanks.
  4. Selective/Voided/Full Tank Reticulating Explosion Suppression Systems: These systems are designed to detect and suppress the propagation of an explosion within the fuel tank, minimizing the risk of a catastrophic event.

The cost-benefit analysis of these options for fleet retrofit, current production, and new type design airplanes should also be provided to the FAA for consideration.

Emission Testing and Reporting Requirements

The emissions testing rules in Utah provide further insights into the measurement of emissions from petroleum refineries and liquid storage. These rules establish emission standards for various sources, such as:

  • Gasoline transfer and storage
  • Pneumatic controllers
  • Flares
  • Tank truck loading

The rules also outline the procedures for continuous emission monitoring programs and source-specific allowable emissions.

Additionally, the EPA’s greenhouse gas reporting rule requires the reporting of emissions from petroleum storage tanks and vapor recovery systems. The rule specifies that only tank-specific methane composition data and gas generation rate data, along with fuel sampling data received from the fuel supplier, are required.

Conclusion

The saturation of fuel vapor recovery tanks is a critical safety concern in the aviation industry. Regulations and guidelines have been established to minimize the hazards associated with explosive fuel-air mixtures in all transport airplane fuel tanks. Emission testing rules and greenhouse gas reporting requirements provide further insights into the measurement and reporting of emissions from petroleum storage tanks and vapor recovery systems.

By understanding the technical details and specific data points related to fuel vapor recovery tank saturation, aviation professionals and regulatory bodies can make informed decisions to enhance the safety of aircraft operations and mitigate the risks associated with explosive fuel-air mixtures.

References:

  • Fuel Tank Inerting for Transport Airplanes, FAA, https://www.faa.gov/regulations_policies/rulemaking/committees/documents/media/ECfthwgT1-1231998.pdf
  • AIR QUALITY RULES – Utah DEQ Document Repository, Utah DEQ, https://documents.deq.utah.gov/air-quality/planning/air-quality-policy/DAQ-2017-006637.pdf
  • 40 CFR Part 98 — Mandatory Greenhouse Gas Reporting, eCFR, https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-98