Hydraulic Fluid Contamination and How it Can Negatively Impact Your Ground Support Equipment

Airplace on the Tarmac Surrounded by GSE

A significant issue in the aviation industry, hydraulic fluid contamination is responsible for a majority of all hydraulic system failures in aircraft tugs and other types of ground support equipment (GSE). In order to prevent this issue, it's important to have a good understanding of the different sources of fluid contamination. This guide will explore the causes of contamination and how to effectively reduce it through testing and regular inspections.

What Is Hydraulic Fluid Contamination?

Hydraulic fluid contamination is when foreign particles, debris or moisture pollute your system's hydraulic fluid. Any type of contamination of hydraulic fluid can cause severe damage to hydraulic systems. In fact, it's been found that more than 75 percent of hydraulic system failures can be directly traced back to dangerous contamination levels in the hydraulic fluid. When hydraulic contamination issues arise, decreased efficiency, expensive repairs and system failures are common occurrences.

Types Of Hydraulic Fluid Contamination

Contamination of your hydraulic fluid can cause it to degrade, which hinders the fluid's ability to lubricate and protect the system's components, thereby reducing your GSE's performance. Corrosion and even a thick sludge or silt can then develop, causing even more serious problems. The following are some of the various hydraulic contamination issues to look out for.

  • Particulate Contamination. Abrasive particulate contamination includes contaminates like sand, dirt or metal flakes. This type of contamination can score precision-machined parts in your ground support equipment, which may lead to the failure of hydraulic pumps and motors. Particulate contamination also increases the risk of cavitation, or the formation of small vapor-filled cavities.
  • Non-Abrasive Particle Contamination. Non-abrasive particle contamination includes things like shredded elastomeric seals or chemical byproducts. These contaminates are equally as damaging as abrasive particulate contamination. It can result in clogged parts and stuck valves, causing issues when trying to control flow and pressure. Non-abrasive particle contamination also increases the likelihood of cavitation.
  • Moisture Contamination. When moisture reacts with the additives in your GSE's hydraulic fluid, problematic chemical reactions can occur. This can include corrosion and issues with the hydraulic fluid's elasticity and performance. And when water is trapped in the hydraulic fluid during pressure changes, the risk of cavitation can spike.

What Are the Sources of Fluid Contamination?

In order to effectively prevent hydraulic fluid contamination — and the damage it can cause — it's important to understand the various sources of fluid contamination. Because at the end of the day, contamination can occur almost anywhere. But if you know when and where it's happening, you can take the right steps to correct and minimize any contamination.

Hydraulic Fluid Manufacturing

During the manufacturing and/or assembly process, built-in contamination can occur. While you can't do much to prevent this, you can mitigate the effects by using filters and regularly flushing old hydraulic fluid.

Hydraulic Fluid Production & Storage

Yes, you read that correctly. Contaminants can very easily make their way into hydraulic fluids during the production process and subsequent storage. Because of this, it's crucial that you use a filtration system with any fresh hydraulic fluid prior to placing it in your GSE.

Moisture can also develop while the fluid is in storage, even with "waterproof" containers. This process is called "breathing" and occurs when a container experiences drastic changes in temperatures. By simply storing your containers in a temperature-controlled environment on their sides, you can help minimize these effects.

Handling & Transfer

When handling and transferring hydraulic fluid, you are naturally exposing it to possible contamination via moisture and particles from the environment. So, be sure to keep containers closed when not in use, especially when in an environment that is relatively unclean. It's also important to remember that different types of fluids should never be mixed, so always flush the system before replacing the fluid in your electric aircraft tug or other GSE.

Operation & Maintenance of GSE

During daily operations, hydraulic fluid contamination is bound to occur. When opening a closed hydraulic system, take care to keep hoses and fittings clean and free of debris. It's also a good idea to use lint-free rags. Be sure to use and maintain filters to prevent any internally generated contamination.

How to Reduce Hydraulic Fluid Contamination

While you can't totally eliminate contamination from a hydraulic system, you can drastically minimize contamination levels through the use of a carefully planned out reduction strategy. Your strategy should take into account the environment, the GSE components and the operating conditions of your hydraulic system. Focus on developing a strategy that is feasible and that supports the design of your system. The following are some steps you can add into your inspection checklist and predictive maintenance routine to help reduce overall hydraulic fluid contamination levels.

Establish a budget based on your organization's day-to-day equipment needs. As long as you have a ground support equipment maintenance plan in place and are regularly maintaining and servicing your GSE, you should be able to resell your equipment or even earn credit as a trade-in. Just understand that some obsolete equipment may have to be scrapped.

Regularly Test & Analyze Hydraulic Fluid

A rigorous program of hydraulic fluid contamination testing, fluid analysis and measurement is the most important part of your reduction strategy. Using a hydraulic testing kit, you'll be able to sample hydraulic fluid at various points in the system. You can then perform an analysis in-house or send it out to a reputable laboratory for further testing. This analysis can give you an accurate measurement of your system's contamination levels, a metric with which to evaluate the cleanliness of your system and the ability to track down the source of the contamination.

Remove Particulate Contamination

If you've identified above-average contamination levels, you'll need to remove the contaminants. It's important to understand that removing contaminants from your hydraulic system is not just time-consuming but also extremely expensive. You'll need to flush the contaminated system, add fresh hydraulic fluid and possibly even remove the old fluid and add new filters.

Keep Everything Clean

When equipment is in the field (and even off the field), it can be difficult to keep contamination under control. Dirt and sand can fall into the hydraulic tank and ports can be left open, allowing moisture to condense. During repairs and maintenance, contamination can easily make its way into your system if you're not careful. The following are just a few things to be mindful of during repairs and maintenance.

  • Keep ports closed during repairs.
  • Remove any abrasive particles that may be lingering on your workbench from a prior repair.
  • Wipe down and thoroughly clean the end of the hydraulic hose before reattaching it.

To combat hydraulic fluid contamination in and out of the field, you need to keep things clean. This includes work surfaces, tools, equipment and the GSE itself. When opening up your GSE's hydraulic system, be extra careful to ensure contamination never has a chance to make its way into the system.

Properly Store & Handle Hydraulic Fluid

To combat minimal contamination, you should properly store and handle hydraulic fluid to reduce moisture. This means ensuring lids are tightly secured, containers are stored on their sides to prevent water from collecting on the top and hydraulic fluid is kept at a consistent temperature to prevent condensation.

Filter Fresh Hydraulic Fluid

Finally, you need to filter any and all hydraulic fluid that enters your GSE hydraulic systems using high-quality filters. This helps to trap any particles that do happen to make their way into your system from the fresh hydraulic fluid.

Minimize Hydraulic Fluid Contamination with the Help of Eagle Tugs

At Eagle Tugs, our mission has always been to provide customers with high-quality GSE that is cutting-edge, safe and reliable. Your ground support equipment is an investment — be sure to maintain it properly through the use of a reputable hydraulic test kit and filtration system. Have a question or need additional information about any of our product lines? Reach out to one of our knowledgeable Eagle Tugs representatives today for more information or to get a quote.

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