When mission-critical fuels are stored, it’s necessary to use fuel testing to verify that it’s still in useable condition. Some installations, like hospitals, are required by law to do this on an annual basis (or more often than that). Other mission critical installations also find it in their best interests to stay on top of their stored fuel condition by annual testing. It’s important to know what you can expect, and the only way to really know is to test the fuel’s properties (specifications). And a test is only as good as the sample it's testing. You might think "a sample is a sample is a sample". But it's a little more complicated than that.
Proper sampling techniques for fuel can be complex enough that you can take a multi-day class on the subject and get a certification in fuel sampling. None of us have time for that - we need things a little more simply put. So here are some simple tips you can use to ensure you get reliable fuel samples that will convey accurate results reflecting the real condition your fuel is in.
Start With The Basics
Make sure your sampling device and containers are clean. You’d think this is elementary, but apparently not.
The kind of container does matter. Glass is inert but requires more specialized packaging if you’re going to mail off the sample to a lab. A clean plastic container made with fluorinated plastic is quite acceptable. You need the plastic to be fluorinated to prevent softening and reactivity over time.
Be sure not to overfill the container – 80% full is a safe benchmark that allows for expansion of the liquid inside.
How Much Do You Need?
How much of a sample do you need? The exact answer depends on the specific tests you want done – some tests require more than others. One quart is a good rule of thumb to follow.
Be sure to pull two fuel samples, though. You want to keep a backup in case something happens to the first one.
How To Take Samples
How best to take fuel samples? There are two main ways to do this.
The industry standard is a device called a Bacon Bomb. Some call it a Pencil Bomb or a Fuel Thief. It looks like a cylinder that is lowered into the tank, with a cord that can be pulled to allow fuel to flow into the cylinder at the appropriate time. They are usually made from brass or some non-sparking metal for safety.
Alternatively, if your fuel storage tank has sampling valves, it's acceptable to drain samples from those. The ASTM protocols allow you to do this provided you run about 5-10 seconds of fuel out of the drain before filling your sampling container.
When sampling from a fuel tank, you should take one sample each from the top, middle and bottom of the tank. The composite results will give you the best picture of the fuel condition in the tank. The fuel at the top can look markedly different (and have different properties) than the fuel at the bottom of the tank.
If you get fuel deliveries on a regular basis, another idea would be to take a sample directly from the fuel delivery truck. This would give you a fuel sample representative of what was being received from the fuel terminal itself.
Handling & Shipping It Off For Testing
Sampling is fine, but once you have your sample, the clock is now ticking. Fuel samples change over time, especially when considering microbial testing. You want to put fuel samples on ice until they're ready to ship. It's also recommended, if you're using a clear glass sample container, to wrap them to keep out sunlight.
When sending the sample off for testing, make sure the container has a tightly-sealed cap. Put the bottle inside of a plastic bag, seal the bag, then package it in a corrugated box. This is the acceptable shipping container for petroleum fuel samples.
You may be interested in these other posts:
- "Wow" Facts on Contaminated Diesel Fuel. Be Prepared.
- Fuel Storage Issues Explained: Why Stored Fuel is Easily Contaminated
- 7 Signs of Diesel Fuel Contamination by Microbes, Fungus and Bacteria
This post was published on January 12, 2016 and was updated on October 19, 2020.