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How To Take A Hydraulic Oil Sample

Rob Panzarella
Posted by Rob Panzarella on Jun 23, 2022 12:00:00 PM

Oil sampling is the important process of analyzing the quality and condition of oil in a hydraulic system. Oil is a hydraulic system's lifeblood, and much like a blood sample, oil samples get analyzed to tell us important information that often goes undetected until system failure. Approximately 85% of hydraulic component failures result from contaminated oil, so today, I'll teach you one way to take an oil sample so that you can prevent these failures from happening to you!


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Video Tutorial  |  What's In A Kit?  |  Step-by-Step Process  |  What Do Standard Kits Test For?

| What if my Hydraulic Fluid is Contaminated?    Summary & Resources


Watch our video for an overview of the process:

Watch on YouTube

What's in a Hydraulic Fluid Test Kit?


A standard oil testing kit usually includes an empty bottle to fill with oil, a container for shipping that bottle, a form to fill out with system information, and a return label to send the sample to the laboratory for analysis. While a sample could be taken just by scooping oil from the reservoir, it isn't effective, as contaminants and water have likely settled or separated from the still oil, leading to inaccurate analysis.

The best method of acquiring an oil sample is to utilize a pump (pictured above) that attaches to a test point in the return line. This ensures the oil being tested is in the work stream and accurately represents the oil going through your system.


HYDAC Fluid Service1-1

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  • System performance analysis

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How To Take a Hydraulic Oil Sample: Step by Step

Below are simple step-by-step instructions that explain how to take a hydraulic oil sample:

1. Safety First - Always utilize safety glasses, gloves, and skin protection before taking an oil sample.

2. Connect to Test Point - Attach your pump line to the test point once you've identified the proper test point.

3. Purge the Test Line - Use the pump to ensure that all of the oil from the last oil sample is out of the test line before filling up your sample bottle.

4. Attach the Sample Bottle - With fresh oil flowing, screw the empty sample bottle to the pump so you can start filling it without the mess! 

5. Slowly Draw Oil - Make sure to use smooth and steady strokes to fill the bottle with oil. 

6. Disconnect Test Point - With the bottle full, you can detach your pump from the test line.

7. Detach Sample Bottle - Then unscrew the sample bottle from the pump.

8. Cap the Sample Bottle - You need the oil to return to the lab! 

9. Fill Out the Paperwork - Make sure to give as much detail on these forms as possible so the lab knows what it's dealing with during testing. Things like the valves incorporated and pumps running can make a big difference when analyzing the test findings and troubleshooting any issues.

10. Send It Back - Make sure the sample bottle is secure in the shipping container, use the return label, and send it back to the lab for analysis!


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What Do Standard Kits Test?


Most standard kits test for the following things:

- Spectro Metals by ICP (tests for traces of 24 different substances, like wear, contaminant, multi-source, and additive metals)

- Viscosity

- Water percentage by Karl Fischer (crackle) method.

- Total Acid Number (TAN)

- Particle count as per ISO 4406

This will vary by company and test, though, so you'll want to make sure to choose the right one based on your needs.

With this information, trained professionals can break down what's happening within a system and implement the necessary changes, much like a doctor analyzes blood work to diagnose and remedy. It's essential to have oil samples done at regular intervals to chart and track the changes and trends in your system. This will allow you and the lab to see the performance and quality of your system over time, which helps enable proactive and predictive maintenance measures.

Oil Sample Analysis


What If My Hydraulic Fluid is Contaminated?


If your fluid sample comes back dirty, all is not lost! There are options to recondition and filter the impurities from your oil. Airline offers the standard rental options below, and other options are available too. Contact us and we can help determine the right conditioning solution based on your oil sample results.

OLF Offline Filtration Unit Rental

Ion Filtration Cart Rental

OLF info th rev (003) cart no bk 2
Filters and conditions hydraulic mineral oils, lubrication oils, cleaning fluids, and coolants Filters and conditions Phosphate Ester (HFDR type) hydraulic fluid
Learn more Learn more




Taking routine oil samples is critical for a proper machine maintenance program. The oil sampling method discussed above is as simple as receiving the kit, filling the sample bottle with oil from your system (preferably with in-stream oil), and sending it back to the lab for analysis. With all the information about the oil and your system, experts can diagnose things like what parts of your system are wearing, what contaminants are in your oil, and the particle count. All these things combined will enable preventive and predictive maintenance measures, saving you from costly downtime.

Look out for Part 2, where we'll break down an oil sample analysis!


We're Here To Help!

If you want assistance in taking or analyzing oil samples for your hydraulic systems, we have industry experts that would be happy to help and answer your questions!

Contact Us


Related Blogs & Resources

Hydraulic Fluid Cleanliness Resources

Hand-Held Filter System

Airline's Machine Maintenance Month

Request a free HYDAC ISO Filtration Poster

More Hydraulic Technically Speaking Articles


Topics: Hydraulics, Explainers, Tutorials, Maintenance, HYDAC, Fluid Cleanliness, Video

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