How Much Sludge is in Your Fuel Storage Tank?
by Ambrose Hughey, OMA I
Business Manager Northwest

If a good tank maintenance program is not in place, I'd bet there is a sludgy mess in your tank. We have seen a surge in samples from fuel storage tanks over the past few years. Much of this surge has been driven by the many changes to diesel fuel refining, new engine design and emissions regulations. This brief article touches upon some of the common issues associated with diesel fuel storage.

To start, diesel fuel degrades naturally over time. This degradation of the fuel produces particulate and gums both soluble and insoluble that build up in storage tanks. This effect is exacerbated in applications that have long term storage, such as standby generators. Generally, biodiesel can degrade faster than conventional middle distillate fuel, which should not be problematic for normal use. However, there may be a need for increased monitoring for long-term storage of biodiesel blends. Proper tank maintenance is a key function to help ensure that the fuel is suitable for use when needed. Accelerated aging testing can be performed to estimate the storage stability of fuels. Changes in test rating values can indicate a relative change in inherent stability.

Tanks breathe and with changes in temperature and humidity, water condenses in fuel storage tanks. Keeping the water content in check can prevent several water related problems. Water contamination can corrode fuel system components and lead to increased wear. Too much water impairs the fuels ability to properly lubricate, especially when enough water is present to create emulsions. Biodiesel typically has a higher water saturation point than middle distillate fuel. As a result, biodiesel blends may have more dissolved water which can create complications with water removal.

Microorganisms, which can plague fuel storage tanks and lead to numerous maintenance issues, also require water to grow. Since most microbial growth occurs at the fuel water interface, keeping fuel systems dry will greatly reduce the likelihood of microbial contamination outbreaks and their related problems. Monitor your fuel and storage tank's water content to ensure your fuel stays dry. Two of the most common problems associated with microbial contamination are the increased potential for filter plugging and corrosion of fuel system components. The slime or sludge normally associated with microbial growth is waste by-product produced and provides a source of premature filter plugging. If an outbreak persists without treatment and removal of the waste, then the sludge buildup in the tank will continue to increase.

Proper fuel storage tank housekeeping is a chief preventative tool for microbial contamination and its associated problems. Biocides are also recommended, especially in wet or humid long term storage environments. Periodic inspection of tank bottoms and dispensers is suggested, and water should be removed from tanks regularly. Depending on fuel cleanliness, having your fuel polished may be a useful tool to remove contamination from otherwise quality fuel. As part of a good housekeeping program, periodic tank bottom samples should be taken to monitor the amount of sediment and water that has accumulated in the tank. It is also recommended that a midpoint sample is taken to monitor the condition of the fuel itself.

For long-term storage of fuel; fuel monitoring, regular sampling and tank maintenance are key components of a successful storage and maintenance program. ALS fluids analysis laboratories can assist maintenance and asset care personnel in establishing a routine sampling and testing program for monitoring storage conditions of diesel and industrial fuel applications.