Considerations for Long Term Fuel Storage

–Joe Wallace, Danbury CT

Many commercial and industrial facilities are required to have fuel oil bulk storage at their sites. Whether it is for heating applications or emergency power generation, the fuel must be available to use especially in mission critical operations, such as hospitals or data centers. If fuel oil is not your primary fuel or you are not running your diesel generators all the time, this bulk storage may sit for extended periods of time before being used. During this time, the fuel begins to degrade, create sludge, grow microbes (often referred to as diesel bug) and suffer water infiltration via condensation, compromised sumps or adsorption. Water infiltration allows for microbe growth between the fuel oil and water interface, but microbe growth is not limited to this area.

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Microbial contamination of diesel fuel – Dow Chemical Company

These side effects of long-term bulk storage may cause significant damage to both your tank and diesel burning equipment resulting in high cost repairs, fines and remediation. Water infiltration will settle at the bottom of the tank and often oxidize the steel tank to create leaks. These tanks may be underground and result in a large soil remediation. Sludge/gum build-up and sediment can clog a generator’s injectors or filters causing poor combustion and engine damage. Water infiltration and fuel degradation can also cause damage to the engine.

Aside from the monetary cost that may be associated with ignoring these issues, emergency generators may be powering life safety devices that could result in major catastrophe.  

British Petroleum suggests that their diesel fuel remains usable for 6-12 months at 30°C and maybe longer at 20°C related to microbial growth. These times are even less for ultra-low sulfur diesel (ULSD or “Clean Diesel”). Circulating the fuel through the generator during load tests or having your tank exposed to the sun significantly heats the oil up and increase the rate of microbial growth. Underground and vaulted storage tanks are more susceptible to water infiltration as they stay cooler and water is able to condense more readily.

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There are several actions you can take to increase the life of your bulk storage. Water is inevitable in an atmospherically vented tank. To reduce water infiltration, keeping your tank full reduces the surface area for water to condense. Keep your sumps free of water to ensure no water is leaking through the manhole and tank fittings or compromising your steel tank. Fuel degradation, sludge and microbial growth can be proactively treated with fuel additives that are readily available.

While the above things can reduce the rate of the problems that can be seen with long-term bulk storage, they are not able to remove the water, sludge and microbes on a large scale like a proper filtration/polishing system.

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Fuel polishing units use several stages of filters to pull the contaminants such as sediment, microbes and water, out the fuel. They can also be automated to run on a schedule to ensure the polishing is consistently being done. Each filter is monitored by a control panel which alarms when they need to be cleaned or replaced. Injection of biocide or other fuel treatments can also be automated into this system.

There are also many best practices for how a fuel polishing unit should be installed and can vary on a case by case basis. Ask us how we can help increase the life of your bulk storage and associated equipment with our team of fuel oil experts.

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