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Diesel Fuel Storage Guidelines: Things To Consider in 2018

Posted by: Erik Bjornstad

Care and husbandry of fuel storage is a hotter topic than ever before. You can’t treat stored diesel fuel like you used to. And it helps to have some guidelines on the best practices to take into account if you want to minimize potential unpleasant surprises.

diesel fuel storage guidelinesWe’ve written a lot on the topic of diesel fuel storage in recent years.  Why fuels have changed.  What problems they’re prone to. What kind of chemicals you may or may not need to treat them with.  Today we wanted to touch on a few different aspects of diesel fuel storage in a little more detail, in terms of what you may not know or realize.  There’s a lot of information out there and, sometimes, important considerations can get lost in the shuffle.

Biostats vs. Biocides

Microbes in fuel are the hot trending topics for stored diesel fuels.  It should be clear that microbial contamination is a problem that must be dealt with to head off massive future problems.  To do this properly, you have to understand the difference between a biostat and a biocide.  Failing to know the difference between the two can spell big trouble, because you think you’re taking the right steps but may not be solving the problem at all.

A biocide is a chemical or substance (including another microorganism) intended to destroy, deter or exert a controlling effect upon a harmful microorganism, by chemical or biological means.

A biostat is a chemical or substance that relates to the conditions which make it easy (or more difficult) for microbes to reproduce and grow.  Something that makes it harder for microbes to grow, but which do not actually kill the microbes.

This is an important distinction. There are many chemicals in the marketplace that make “biocidal claims” in that they imply that if you use them, they will “get rid” of a microbe problem.  Or they make an explicit claim that, among other things, they will kill microbes or eliminate problems.  Another practice that falls under the “biostat umbrella” is the removal of free water.  Yes, it is important to remove free water from storage tanks with microbe problems – it’s one of the recommended best practices.  But removing free water doesn’t kill microbes. If anything, it’s a biostat practice. It seeks to change the conditions of the tank to (hopefully) make it more difficult for microbes to grow. But simply removing free water won’t kill microbes and won’t solve a microbe problem.

When you talk about killing microbes, that’s a biocidal claim because that’s what biocides specifically do. They kill microbes.  And when you have an active microbe problem in your stored fuel, you have to use a biocide to kill the microbes and stop their reproduction.  That’s the only solution that will solve your problem.

To solve microbe problems in stored fuel, be sure to use a biocide, not a biostat.

The Kinds of Testing To Take Into Account

Fuel testing is another trending topic in fuel storage. Microbial contamination is on the rise in stored fuels, along with associated problems like tank corrosion and particulate formation in stored fuels.  While we know the kind of signs and symptoms that are associated with these, those only tell us about the present state of the fuel.  How can we predict fuel problems when we may not be able to correctly observe or assess the real state of the fuel today?  Fuel testing is the only thing that can help you do that. These are the kind of fuel tests that can be most helpful for good fuel storage husbandry.

Stability Testing – tests like Accelerated Oxidative Stability, Thermal Stability and the Petroxy stability test can be extremely useful in predicted what may happen to the fuel’s condition in the coming weeks. So they are a little different in that they don’t necessarily tell you, from a measurable standpoint, the exact condition of the fuel right now. They tell you what to expect with the fuel in the near future. This makes sense, since “stability” is defined as something’s ability to resist change. So you’re expressing the fuel’s ability to not change.  

One thing to keep in mind with Stability Testing is that the right kind of test to do can depend on whether the fuel is ULSD or not, as well as if it contains a significant amount of biodiesel. What they’re finding is that the Petroxy stability test is actually preferable to the older Accelerated Oxidative Stability test (ASTM D-2274) because the older test was optimized for higher sulfur diesel fuels.

It’s recommended for you to have the stability of your stored fuel tested once or twice a year.

Water and Particulate Content – This is specified in the ASTM D975 requirements for diesel fuel. This test will tell you what the actual total content of water and particulate is in your fuel at the time of testing. So it’s not predictive as stability testing is, it’s descriptive.  And that’s important enough to know that the law says diesel fuel cannot have more than 500 ppm of water + sediment content in it at any one time.  If your diesel fuel exceeds these, it’s going to cause problems.

You may be interested in these related posts:

Are You Fuel Ready? The Checklist

This post was published on June 15, 2018 and was updated on June 15, 2018.

Topics: Diesel, Fuel Storage