CORROSION AND DEBRIS IN FUEL STORAGE TANKS

Corrosion and Debris in Fuel Tanks

?02-25-2018

The mandated introduction of low ultralow sulfur diesel (ULSD) and combinations of fatty acid methyl esters (FAME) have certainly had an effect on the number of heavy contamination incidents caused by microbial colonization (diesel bugs) and acidic atmospheres (low PH) seen in retail and commercial fuel storage tank systems.

As a result, those involved in its production, distribution and storage find a need to change, or at least review, the way they manage their operations to maintain fuel quality and safe fuel storage.

What is the Diesel Bug and Can it Be Prevented?

Diesel bug is one of the many names for a consortium of microorganisms able to grow in storage tank environments. Once there they utilize the alkanes, additives, amines and the fuel itself, creating a biomass, biofilms, damaging acidity and other annoying and contamination by products.

This consortium of organisms will live very happily in any water bottom and particularly at a fuel/water interface where it can create thick communal mats known as biomass. This consortium of biofilm colonizing constituencies can coat fuel mien level exposed empty space surfaces (climbing) up storage tank walls.

How does the bug form?

The bugs are inherent in fuel resident and or delivered to the tank. The bugs exist and are continually able to conditionally adapt--genealogically simple, extremely diverse, and possessive of extremely clever techniques required for survival. If conditions suit, the bugs will colonize and develop very quickly, particularly with humid conditions when condensation becomes dissolved in fuel, resident on a tank bottom, on an exposed tank containment boundary (wetting) wall, and/or on other exposed fueling system component surfaces.

Fungal spores and bacteria are inherent in the fuel and additionally carried in both air and water humid tank venting atmospheres. They cannot be kept out of fuel storage tanks! Monitoring and restricting the infiltration of oxygen and water rich venting atmospheres along with good housekeeping is a key to limiting problems.

Changes Having an Impact.

Changes intended and thought positive for the environment have had less than desirable impacts on fuel storage systems and system component integrity. The unintended ULSD reformulation, consequences aside from the threat of microbiological contamination, is helping to create extremely acidic and hostile tank empty space atmospheres.

Dealing with the colonizing diesel bugs and acidic atmospheres for some is proving to be a complex problem. Understanding and dealing with the problem requires knowledge that things other than the reformulation of today’s fuels have changed.

Recommendations to remove and prevent water, minimize diesel bug colonization and acidic empty space atmosphere problems are as true today as they have ever been.

• It is much more difficult to prevent the hygroscopic effects and effectively remove water from diesel fuel containing blended percentages of biofuel.
• ULSD fuel today is more hygroscopic, meaning biofuels absorb and hold on to water to a greater degree than traditional diesel fuel refined in the past.

Economics and the Effect on Fuel Storage Practices in Retail and Commercial Fuel Storage Tanks Today.

The divested ownership and management of retail fuel storage tanks by major oil company inevitably has led to less fuel being stored in lower demand throughput tanks. Understanding that when retail fueling facilities were directly owned and managed by refiners, tanks on those properties were included in part as a regional refinery’s bulk volumes of untaxed presale product storage. These lower volume aspects of fuel storage dramatically changed as fueling site divestment of below grade asset ownership and management changed.

A tanks space is now more likely “in laymen’s terms” managed and operated typically less full of fuel and or “more-empty.” Realization that tanks now exhibiting fuel quality storage and velocity corrosion system component problems initially were designed to be “fuel” full with limited or less empty space (ullage) volume. Retail operators typically for economic reasons now reconcile, store and order fuel based on anticipated daily throughput.

• Higher anticipated sale volume product storage tanks tend to be kept more
• (Worked from the top down) full.
• Lower anticipated sale volume product storage tanks tend to be kept less (worked from the bottom up) full.

Unfortunately the “Mostly Empty Space” (MES) effects exhibited today on a storage tanks containment integrity, design expectancy term and ability to safely store and dispense a quality fuel is questionable.

Regulatory Changes and Requirements Effecting Equipment Storing and Dispensing Common Fuels.

There seems to be an unfortunate disconnect between equipment manufacturers, fuel refiners, fuel marketers and clean air and water regulatory agencies regarding fuel storage and delivery fueling system component compatibility for storing reformulated fuels. State and Federal regulating agencies may be guilty for requiring dramatic changes in tank venting without considering serious fatal flaw operation dynamics or conflicting required equipment regulation consequences.

Truly unfortunate is the realization that fuel storage infrastructure failure warnings issued as early as 2003 continue to be ignored. Ignorance seemly becoming an accepted or preferred way of preventing problems.

Interestingly about the time corrosion and oxidization debris problems in storage tanks were becoming obvious, system dynamic configuration changes by regulation were (PV valves on tank vents and phase II decommissioning) implemented. At the same time fueling system component manufacturers were making changes to address problems caused by intermittent line leak detector alarms. Simple uncalculated term or effect changes in fueling equipment storage and delivery system dynamics combining with larger tank empty space atmospheres may have seriously been overlooked.

Can the Problem Be Solved?

Ironic as it might sound determining the cause would be recognition that there IS actually a problem. Unfortunately the cause once identified in the end is going to cost someone a lot of money. In the meantime maybe we just need further study.

We have been studying “The Problem” now for 14 YEARS. Individual and corporate agendas with no infrastructure failure, economic or environmental concerns have produced a “Titanic” and inevitable doom scenario where as long as you “booked with a first class ticket you probably still have nothing to worry about” The Titanic sank didn’t it?

First Ask One Has to Ask What Is the Problem?

The problem is inherent hydrocarbon consuming bugs exist in all fuel. Realize YOU can’t get rid of them. If you do temporally get rid of most of the bugs in the tank more show up the next time fuel is delivered. When adding chemical amines to control contaminating constituents (bugs and or molds) you are trying to control an organism(s) that is extremely diverse and reactive with respect to adaptation and exercising techniques for survival.

Fuel storage integrity and fuel quality issues are only symptoms of a real problem not the cause or the problem - continuing to ‘treat’ just the symptoms - will not correct the real cause or problem – we may end up on a chemical tread mill that never ceases.

Humidity in atmosphere venting into a tank to relieve vacuum produced as fuel is dispensed will condense as water. Water is heavier than most fuel and will eventually end up at the bottom of the tank. Two very basic and fundamentally proven dynamics of physical science.

Number One Problem Resolution Path; Keep Water Out of Tanks!

Number Two Problem Resolution Path; Keep Water and Oxygen Out of Tanks!

Bugs inherent in fuel will become active and begin colonization in a tank at the point where the water interfaces with fuel. Bio activity can or will produce adverse acidic atmospheric conditions in a fuel tanks empty space. Acidity combining (low PH) in an atmospherically humid empty space becomes environmentally hostile to any fueling component surface wetted and or exposed. Oxygen as an oxidizing agent, the fuel pump atomizing fuel upon pressure relief in a tanks empty space combined with low PH and moisture now complicated becomes a recipe for the “Cauldron Effect”. Ferrous oxide and a myriad of other nasty constituents you end up with exposed tank surface, system component contact corrosion and inevitably containment and component integrity failure.