The Complete Guide to Fuel Sampling: Best Practices and Techniques

When it comes to the dual goals of maintaining fuel quality and preventing costly equipment failures that might be fuel-related, proper fuel sampling is a step that cannot be skipped. Fuel testing and fuel monitoring are (together) one of the three prongs of the best practice Hybrid Approach to Fuel Care. But you can't do these without proper fuel sampling. As discussed in a recent episode of the Fuel Pulse Show podcast, where you sample from in a tank can significantly impact your test results—and ultimately, your fuel management decisions.

Why Sampling Location Matters

Sampling location matters because the fuel in a storage tank can look and test differently based on where it is in the tank. Contaminants like water, sediment and microbial growth tend to concentrate at the bottom of fuel tanks. This means that taking samples from the wrong location could give you misleading results, depending on what you're testing for. This can potentially lead to false negatives that mask serious problems requiring immediate attention.

Choosing the Right Sampling Location

So where should you sample from? The ideal sampling location depends on what you're testing for:

Physical or Combustion Properties Testing

For tests like flashpoint, distillation, cetane value, viscosity, and cold flow/cloud point, samples from the top or middle of the tank work well. These properties remain relatively consistent throughout the tank, so sampling from the top or middle will tell you what you need to know while avoiding excess contamination that might skew these results.

Stability Testing

While top or middle samples can work for oxidative or thermal stability testing, bottom samples are preferred. This is because heavier oxidative precursor molecules tend to concentrate near the tank bottom.

Microbial Contamination

Bottom sampling is essential for microbial testing, but with a catch—you want to sample 3-6 inches from the bottom, not from the very bottom. Microbes typically concentrate at the interface between water and fuel layers, making this zone crucial for accurate testing.

Water and Sediment Testing

These tests absolutely require bottom samples. Top or middle samples simply won't provide meaningful results since water content concentrates near the bottom.

Professional Sampling Techniques

The Bacon Bomb Method

The industry standard for fuel sampling is the "bacon bomb" fuel sampler —a non-sparking metal cylinder designed specifically for this purpose. Here's how to use it effectively:

1. Measure your tank depth using a measuring stick
2. Mark the cord for precise depth positioning
3. Lower the fuel sampler to the desired depth indicated by your mark
4. Collect the sample using the sampler's release mechanism
5. Transfer to a clean sampling container

Advanced Sampling Tools

Some versions of this fuel sampler, like those from Bell Performance, come with specialized attachments of varying lengths (3-inch, 6-inch, and 12-inch). These attachments ensure consistent sampling heights without the need for manual measurement.

Best Practices for Sample Handling

Container Selection

You do want to consider a few things for the container you'll be decanting your sample into.

• Use clean containers to prevent contamination
• Glass mason jars are preferred over plastic containers because they provide better visual inspect capabilities
• Pre-label containers before starting the sampling process

Sample Preservation

If you're taking samples to do microbial testing, you want to handle that sample properly to preserve its condition and keep it from changing. This is especially true for samples used in microbial testing. That's because whatever microbial populations are in your sample will start to change once you remove them from their "normal environment" of the storage tank - a place that is dark, climate-controlled, and oxygen-free. You can't keep all changes from happening, but the ASTM offers a few simple steps to try and stem the changing tide.

For preserving samples used for microbial testing:

• Keep samples on ice while in the field
• Transfer to refrigeration as soon as possible
• Maintain cool temperatures to preserve microbial populations

Multiple Test Considerations

Sometimes you need to run several different tests from one sample. If some tests work best from bottom samples while others work fine from top or middle samples, where in the tank should you sample from if you're mixing different tests?

When conducting multiple types of tests from a single sample, default to collecting from 3-6 inches off the bottom. This location provides the best overall diagnostic value for comprehensive testing requirements.

Key Takeaways

1. Sampling location directly impacts test accuracy
2. Different tests require different sampling heights
3. Professional sampling tools ensure consistent results
4. Proper sample handling is crucial for accurate testing
5. When in doubt, bottom sampling (3-6 inches up) provides the most comprehensive results

By following these guidelines, fuel managers can ensure they're getting the most accurate test results possible, leading to better fuel quality management and reduced equipment problems.

---

*This article is based on Episode 67 of the Fuel Pulse Show podcast hosted by Erik Bjornstad. For more insights on fuel management, subscribe to the Fuel Pulse Show on your preferred podcast platform.*

Listen to the Episode