If you’re in charge of any setting where large tanks of diesel are stored, it’s important to know how to maintain the quality of that fuel. This is especially important where there are large tanks of standby fuel held back for emergencies that may end up standing untouched for long periods. The other important thing is to know how to test and maintain fuel quality in a cost-effective manner.

The potential costs of replacing large quantities of fuel and of failing to meet emergency fuel requirements can both be huge. Luckily, there are a number of different technologies available to help you keep your fuel supply viable. What can actually happen if you don’t take these measures? Let’s take a look.

The Benefits of Clean Fuel and of Cleaning Your Fuel

Keeping your fuel supply clean and viable is essential no matter how long you store it, but the longer you store it for, the more likely you are to face problems with fuel degradation. Water and sediment in fuel can lead to blocked fuel filters on the equipment that’s using it. Ultimately you can end up seeing equipment suddenly fail.

If mission critical equipment fails you can end up facing all of the problems the equipment should be protecting you from, along with a hefty maintenance bill. This is especially pertinent where lives are at stake, or in situations where power failure will lead to high costs for customers using your service.

Fuel contamination and degradation is one of the main causes of equipment failure in an emergency, making looking after your fuel a key part of your emergency back-up maintenance responsibility.

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How Does Fuel Get Contaminated?


One of the most common fuel contaminants is water. Water, of course, doesn’t burn. Nor does it mix with diesel or other oil-based fuels. Water can get into your fuel system when its being filled, or from condensation from air that’s in the tanks. Water can mix with fuel to form a ‘mayonnaise-like’ goo that blocks filters and gets stuck in fuel lines, leading to system failure.


Microbes are also a problem, especially with modern fuels. They can get in to fuel tanks along with the air. After this they’re free to grow, largely clinging to fuel additives and living off of air in the system. Microbes can form both a jelly-like substance and sediment from their dead bodies. Both of these lead to fuel line blockage, filter blockage, and system failure.

Microbes are more common near water, so they can be especially problematic in marine industry. They’re also more of a problem where fuel is stored for a long time, so emergency tanks stored near the sea are especially vulnerable. The slimes and sludges that microbes can produce may also cause equipment and fuel lines to crack, make filters last less time, and can cause raised emissions and black smoke. If your tank filters need changing a lot more often than usual, there’s a good chance that microbes are to blame.

Sludge caused by diesel bug growth

Sediment, Sludge, and Other Particulates

Sediment formed from dying microbes, shed from decaying tanks, or brought in from outside as dust or dirt on the wind can also cause problems. Not only can it block pipes and filters, it can also get into running equipment and cause friction and other wear and tear on moving parts.

Sometimes these particulates come from organic matter, such as dead microbes or other organic waste that has gotten into the tanks. Other times rust or even just plain old dirt is the culprit. Both of these are a big problem and need to be dealt with as soon as possible. Decaying matter especially can damage tanks and other equipment in the long term, leading to increased maintenance costs and sudden unpredictable failures.


Protecting Fuel in Storage

Many settings call for fuel to be stored long-term to make sure it’s always available in case of emergencies. Hospitals, data centres, and other settings with emergency back-up generators need to know there’s plenty of fuel on hand should the power grid go down. When you store diesel and other fuel oils long term, there’s a risk that sediment and gum can form as the fuel reacts with oxygen in the air. Even assuming that your fuel has been stored at the recommended temperature in a perfectly maintained tank, you can only assume that it will keep for 6-12 months

Fuel degradation is made worse by failing to keep the fuel at the optima ambient temperature of 20° C, allowing dust and debris to enter the tank (perhaps when filling it or testing the fuel), and letting the fuel come into contact with copper, zinc, and certain alloys, or reactions due to microbes reacting with the fuel or its components. Debris and sediment can cause fuel filter blockage during use, leading to a sudden failure of emergency power generation equipment. Prevention is better than a cure, though measures can be taken to test and re-filter fuel that has already been standing for long periods.

The best way to protect long-term fuel storage from degradation is to use well maintained storage facilities that allow you to fill, drain, and test the fuel without letting anything that shouldn’t come in to contact with the fuel or get in to the tank. Careful management when fuel is stored, accessed, and transferred is an important first step when trying to ensure a clean fuel supply.

What if Fuel Condition is Already Questionable?

Of course, in some cases it’s impossible to avoid storing large amounts of fuel for years. This is where fuel polishing becomes important. With the right equipment it’s possible to polish up to 20 tonnes per hour, removing all contaminants down to a diameter of 1 micron. Periodic polishing of stored fuel serves to keep it in a viable condition, ready to use at a moment’s notice.

Unfortunately, sometimes you only find out about the ways that fuel can degrade when testing shows there’s already a problem. Luckily this doesn’t mean the fuel is a dead loss. Fuel polishing can still be used to clean up the fuel in situ, and any debris and old fuel can be flushed from the system to give you a clean slate. If you have problems with microbes you won’t be able to get rid of the problem with fuel polishing alone, you’ll need to add a biocide to your fuel supply in addition to any mechanical cleaning.

Prevention is Better than Cure

The best way to prevent fuel quality issues is to have procedures in place to prevent problems developing. A little bit of forward planning can make sure you’ll never face sudden equipment failure due to fuel quality issues.

As a minimum, you’ll need to:

  • Make sure you have fuel handling policies in place to ensure tanks are filled and tested carefully, without allowing contamination to creep in when they’re accessed
  • Have a regular testing policy to check for contaminants
  • Check and change filters and other equipment regularly
  • Test all equipment regularly, including the fuel system
  • Set up periodic fuel polishing and tank flushing to clear any blocked pipes and maintain the quality of stored fuel and its pathway to where it’s used
  • Include checks on temperature and physical degradation in your tank maintenance check

If you’re in charge of mission critical fuel systems then you need to make sure you’re doing everything to protect your users and your equipment. Get in touch today to find out the best way to protect your fuel and prevent problems in an emergency.


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