NPN Magazine April 2013

National Petroleum News (NPN) has been the independent voice of the petroleum industry since 1909 as the opposition to Rockefeller’s Standard Oil. So, motor fuels marketing and retail is not just a sideline for us, it’s our core competency.

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acid) present in ULSD systems are facilitating aggressive corrosion • Additives in the fuel could play a role in contributing to the corrosive environment in ULSD systems, but it is unlikely All of the inspected sites contained microbes with the dominant organism known as Acetobacter, which leads to the production of acetic acid, which was found to be ubiquitous in the fuel, water bottoms, vapors and scrapings at all of the sites that were inspected. Secondly, and more surprisingly, ethanol was identified and measured in the USTs at five of the six inspected sites. The source of the ethanol was unknown, however, diesel fuel is often delivered in the same trucks as ethanol-blended gasoline. In addition, it is possible that a ULSD UST that was previously used to store gasoline, could potentially have a manifolded ventilation system connected to other gasoline tanks. These two circumstances could lead to some cross-contamination of ethanol and ULSD. The report's conclusion stated: "Corrosion in systems storing and dispensing ULSD is likely due to the dispersal of acetic acid throughout USTs. It is likely produced by Acetobacter bacteria feeding on low levels of ethanol contamination. Dispersed into the humid vapor space by the higher vapor pressure (0.5 psi compared to 0.1 psi for ULSD) and by disturbances during fuel deliveries, acetic acid is deposited throughout the system. This  n  NPN Magazine results in a cycle of wetting and drying of the equipment, concentrating the acetic acid on the metallic equipment and corroding it quite severely and rapidly." This shows that corrosive particles can be circulated through the UST and that it is possible for them to exit during the fueling process. The last line of defense against this potential invasion of corrosive particulates into a vehicle's fueling system is the dispenser fuel filter. Instead of blaming the fuel filter for becoming fouled and needing to be replaced, fuel-site operators that dispense ULSD should recognize that the fuel filter halts the particulate invasion and serves as an indicator that problems with excessive corrosion may exist in the UST and the overall fuel-dispensing system. Suggested solutions to the problem of excessive ULSD UST corrosion include the installation of a water-monitoring probe in the tank or the use of biocides that are designed to kill any microbes that are present. Additionally, the Petroleum Equipment Institute has created a number of "Recommended Practices" manuals that address UST operation, inspection and maintenance at fueling sites, including RP500: Inspection and Maintenance of Motor Fuel Dispensing, RP900: UST Inspection and Maintenance and RP1200: Testing and Verification of Equipment at UST Facilities. Finally, you can also contact your filter distributor if you have any further questions regarding the issue of excessive ULSD corrosion and how it can affect filter performance. April 2013 21

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